Talk:Sensory - Balance Development

About Discussion Pages

On this website the Discussion Tab or "talk pages" for a topic has been used for several purposes: References - recent and historic that relates to the topic Additional topic information - currently prepared in draft format Links - to related webpages Topic page - an edit history as used on other Wiki sites Lecture/Practical - student feedback Student Projects - online project discussions. Links: Pubmed Most Recent | Reference Tutorial | Journal Searches Glossary Links Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link Cite this page: Hill, M.A. (2024, April 19) Embryology Sensory - Balance Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Sensory_-_Balance_Development

<pubmed limit=5>Semicircular Canal Development</pubmed>

<pubmed limit=5>Saccule Development</pubmed>

<pubmed limit=5>Utricle Development</pubmed>

2013

Morphological and morphometric study on human Scarpa ganglion development

Acta Otolaryngol. 2013 Jan 28. [Epub ahead of print]

Sanchez Del Rey A, Sánchez Fernández JM, Gutierrez N, Martínez A, Santaolalla Montoya F. Source Otorhinolaryngology Department, School of Medicine, University of the Basque Country, UPV/EHU , Bilbao, Vizcaya , Spain.

Abstract

Abstract Conclusion: In Scarpa neurons the cell and nuclear area increases and nuclear/cytoplasm ratio decreases with fetal age (p < 0.0001). There are statistically significant differences in cell area between all fetal groups, except for the interval 45-74 mm crown-rump-length (CRL). Displacement of a neuron within the internal auditory meatus (IAM) occurs from 9 weeks in the fetus until the neonate. Methods: A light microscopic histomorphometric study of the Scarpa ganglion in human fetuses from spontaneous abortions measuring 45, 74, 90, 134, 145 and 270 mm CRL and a from a 1-day-old neonate (360 mm) was carried out. Cell and nuclear area, ganglion area and distances from the Scarpa ganglion neurons to the endocranial porus of the IAM were measured. Results: In the 45, 74, 90 and 134 mm CRL human fetuses the cartilaginous labyrinthine capsule appears divided by the facial nerve and the Scarpa ganglion into two compartments: rostral and dorsal. Ovoidal Scarpa ganglion in the 45 mm CRL lies within the IAM near its endocranial porus (15 µm). In the otic capsule of the 145 mm CRL fetus an endochondral ossification appears in the IAM base, where Scarpa ganglion neurons are displayed in two groups: superior and inferior divided by a vascular-connective septum. This anatomy remains from this specimen until the neonate specimen.

PMID 23350596

http://informahealthcare.com/doi/abs/10.3109/00016489.2012.756147

2012

Replacing semicircular canal function with a vestibular implant

Curr Opin Otolaryngol Head Neck Surg. 2012 Aug 9. [Epub ahead of print]

Merfeld DM, Lewis RF. Source aJenks Vestibular Physiology Laboratory, Massachusetts Eye and Ear Infirmary bDepartment of Otology and Laryngology cDepartment of Neurology, Harvard Medical School, Boston, Massachusetts, USA.

Abstract

PURPOSE OF REVIEW: To summarize the recent progress in the development of vestibular implants. The review is timely because of the recent advances in the field and because MED-EL has recently announced that they are developing a vestibular implant for clinical applications. RECENT FINDINGS: The handicap experienced by patients suffering from bilateral vestibulopathy has a strong negative impact on physical and social functioning that appears to justify a surgical intervention. Two different surgical approaches to insert electrodes to stimulate ampullary neurons have been shown to be viable. The three-dimensional vestibulo-ocular reflex in rhesus monkeys produced with a three-dimensional vestibular implant showed gains that were relatively normal during acute stimulation. Rotation cues provided by an implant interact with otolith cues in a qualitatively normal manner. The brain appears to adapt plastically to the cues provided via artificial electrical stimulation. SUMMARY: Research to date includes just a few human studies, but available data from both humans and animals support the technological and physiological feasibility of vestibular implants. Although vestibular implant users should not expect normal vestibular function - any more than cochlear implant users should expect normal hearing - data suggest that significant functional improvements are possible.

PMID 22886037

2008

Epithelial-mesenchymal transition as a possible mechanism of semicircular canal morphogenesis in chick inner ear

Tohoku J Exp Med. 2008 Jul;215(3):207-17.

Kobayashi Y, Nakamura H, Funahashi J.

Department of Molecular Neurobiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan. Abstract Semicircular canals are sensory organs for balance, consisting of fluid-filled tubules that are arranged perpendicularly to each other in inner ear. The precise mechanism of the morphogenesis of this unique organ is still under investigation. Semicircular canals arise from the flattened pouch of epithelium. The centers of two apposing wall of the pouch approach each other and form a fusion plate. The clearing of the fusion plate makes a hole and leaves the remaining tissue as semicircular canals. Three mechanisms have been proposed for this clearing: programmed cell death, epithelial-mesenchymal transition, and retraction of the cells in the fusion plate to surrounding semicircular canals. Previous studies have revealed programmed cell death in the fusion plate, although other two hypotheses were not disproved. Here we examined the contribution of epithelial-mesenchymal transition and epithelial retraction to the morphogenesis of semicircular canals. We analyzed immunohistochemically the structural change in the epithelium of the developing fusion plate using molecular markers, basal lamina component laminin, cytoskeletal F-actin, and cellular junctional marker beta-catenin. Our observation revealed that fusion plate epithelium lost its apico-basal polarity and intermingled with facing fusion plate cells, associated with the disruption of basal lamina. Moreover, there were several cells with mesenchymal appearance adjacent to the torn basal lamina. We also found the merging of apposing basal laminae at the border between forming canal and breaking fusion plate. These observations suggest that the epithelial-mesenchymal transition, rather than the epithelial retraction, may be responsible for clearing fusion plate cells.

PMID 18648181

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2610337

---

http://www.ncbi.nlm.nih.gov/pubmed/20126551

Requirement for Lmo4 in the vestibular morphogenesis of mouse inner ear. Deng M, Pan L, Xie X, Gan L. Dev Biol. 2010 Feb 1;338(1):38-49. Epub 2009 Nov 10. PMID 19913004

Tbx1 and Brn4 regulate retinoic acid metabolic genes during cochlear morphogenesis. Braunstein EM, Monks DC, Aggarwal VS, Arnold JS, Morrow BE. BMC Dev Biol. 2009 May 29;9:31. PMID 19476657

Semicircular canal size determines the developmental onset of angular vestibuloocular reflexes in larval Xenopus. Lambert FM, Beck JC, Baker R, Straka H. J Neurosci. 2008 Aug 6;28(32):8086-95. PMID 18685033

Vestibular evoked myogenic potentials: past, present and future. Rosengren SM, Welgampola MS, Colebatch JG. Clin Neurophysiol. 2010 May;121(5):636-51. Epub 2010 Jan 18. Review. PMID: 20080441

Neurofibromatosis type 2 (NF2): a clinical and molecular review. Evans DG. Orphanet J Rare Dis. 2009 Jun 19;4:16. Review. PMID 19545378

Development and assessment of the vestibular system. Nandi R, Luxon LM. Int J Audiol. 2008 Sep;47(9):566-77. Review. PMID 18821226

http://informahealthcare.com/doi/abs/10.1080/14992020802324540

Surgery of the semicircular canals. Portmann D, Guindi S. Rev Laryngol Otol Rhinol (Bord). 2008;129(1):3-9. Review. PMID 18777763 [

---

Vestibular Development

1. Pendred Syndrome/DFNB4.

Smith RJH, Van Camp G. In: Pagon RA, Bird TC, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle; 1993-. 1998 Sep 28.

Disease characteristics. Pendred syndrome and DFNB4 comprise a phenotypic spectrum of hearing loss with or without other findings. Pendred syndrome is characterized by severe-to-profound bilateral sensorineural hearing impairment that is usually congenital and non-progressive, vestibular dysfunction, temporal bone abnormalities, and development of euthyroid goiter in late childhood to early adulthood. Variability of findings is considerable, even within the same family. DFNB4 is characterized by nonsyndromic sensorineural hearing impairment, vestibular dysfunction, and temporal bone abnormalities. Thyroid defects are not seen in DFNB4. Diagnosis/testing. Pendred syndrome and DFNB4 are diagnosed clinically in individuals with (1) hearing impairment that is usually congenital and often severe to profound, although mild-to-moderate progressive hearing impairment also occurs; and (2) bilateral dilation of the vestibular aqueduct (DVA, also called enlarged vestibular aqueduct or EVA) with or without cochlear hypoplasia (the presence of both DVA and cochlear hypoplasia is known as Mondini malformation or dysplasia). In addition, individuals with Pendred syndrome have either an abnormal perchlorate discharge test or goiter (when no other etiology of the goiter is evident and perchlorate washout cannot be performed). The only two genes known to be associated with Pendred syndrome/DFNB4 are SLC26A4 (~50% of affected individuals) and FOXI1 (~1% of affected individuals, suggesting further genetic heterogeneity). Sequence analysis identifies disease-causing mutations in approximately 50% of affected individuals from multiplex families and 20% of individuals from simplex families; such testing is clinically available. FOXI1 testing is available on a research basis only. Management. Treatment of manifestations: hearing habituation, hearing aids, and educational programs designed for the hearing impaired; consideration of cochlear implantation in individuals with severe-to-profound deafness. Standard treatment of abnormal thyroid function. Surveillance: semiannual or annual assessment of hearing and endocrine function. Repeat audiometry initially every three to six months if hearing loss is progressive. Agents/circumstances to avoid: weightlifting and contact sports. Genetic counseling. Pendred syndrome/DFNB4 is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk family members and prenatal testing for at-risk pregnancies are possible when the family-specific mutations are known.

PMID 20301640

2010

Long-term consequences of Sox9 depletion on inner ear development

Dev Dyn. 2010 Apr;239(4):1102-12.

Park BY, Saint-Jeannet JP.

Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

The transcription factor Sox9 has been implicated in inner ear formation in several species. To investigate the long-term consequences of Sox9 depletion on inner ear development we analyzed the inner ear architecture of Sox9-depleted Xenopus tadpoles generated by injection of increasing amounts of Sox9 morpholino antisense oligonucleotides. We found that Sox9-depletion resulted in major defects in the development of vestibular structures, semicircular canals and utricle, while the ventrally located saccule was less severely affected in these embryos. Consistent with this phenotype, we observed a specific loss of the dorsal expression of Wnt3a expression in the otic vesicle of Sox9 morphants, associated with an increase in cell death and a reduction in cell proliferation in the region of the presumptive otic epithelium. We propose that, in addition to its early role in placode specification, Sox9 is also required for the maintenance of progenitors in the otic epithelium.

PMCID: PMC2847000

PMID 20201105

3. PLoS One. 2010 Feb 23;5(2):e9377.

Canal cristae growth and fiber extension to the outer hair cells of the mouse ear require Prox1 activity.

Fritzsch B, Dillard M, Lavado A, Harvey NL, Jahan I.

Department of Biology, University of Iowa, Iowa City, Iowa, United States of America. bernd-fritzsch@uiowa.edu

BACKGROUND: The homeobox gene Prox1 is required for lens, retina, pancreas, liver, and lymphatic vasculature development and is expressed in inner ear supporting cells and neurons. METHODOLOGY/PRINCIPAL FINDINGS: We have investigated the role of Prox1 in the developing mouse ear taking advantage of available standard and conditional Prox1 mutant mouse strains using Tg(Pax2-Cre) and Tg(Nes-Cre). A severe reduction in the size of the canal cristae but not of other vestibular organs or the cochlea was identified in the E18.5 Prox1(Flox/Flox); Tg(Pax2-Cre) mutant ear. In these mutant embryos, hair cell differentiated; however, their distribution pattern was slightly disorganized in the cochlea where the growth of type II nerve fibers to outer hair cells along Prox1 expressing supporting cells was severely disrupted. In the case of Nestin-Cre, we found that newborn Prox1(Flox/Flox); Tg(Nestin-Cre) exhibit only a disorganized innervation of outer hair cells despite apparently normal cellular differentiation of the organ of Corti, suggesting a cell-autonomous function of Prox1 in neurons. CONCLUSIONS/SIGNIFICANCE: These results identify a dual role of Prox1 during inner ear development; growth of the canal cristae and fiber guidance of Type II fibers along supporting cells in the cochlea.

PMCID: PMC2826422 PMID 20186345

4. Int J Otolaryngol. 2009;2009:972565. Epub 2010 Jan 27.

The importance of saccular function to motor development in children with hearing impairments.

Shall MS.

Department of Physical Therapy, Virginia Commonwealth University, P.O. Box 980224, Richmond, VA 23298-0224, USA.

Children with hearing deficits frequently have delayed motor development. The purpose of this study was to evaluate saccular function in children with hearing impairments using the Vestibular Evoked Myogenic Potential (VEMP). The impact of the saccular hypofunction on the timely maturation of normal balance strategies was examined using the Movement Assessment Battery for Children (Movement ABC). Thirty-three children with bilateral severe/profound hearing impairment between 4 and 7 years of age were recruited from a three-state area. Approximately half of the sample had one or bilateral cochlear implants, one used bilateral hearing aids, and the rest used no amplification. Parents reported whether the hearing impairment was diagnosed within the first year or after 2 years of age. No VEMP was evoked in two thirds of the hearing impaired (HI) children in response to the bone-conducted stimulus. Children who were reportedly hearing impaired since birth had significantly poorer scores when tested with the Movement ABC.

PMCID: PMC2817862 PMID 20148080

2009

Auditory and vestibular dysfunction associated with blast-related traumatic brain injury

J Rehabil Res Dev. 2009;46(6):797-810.

Fausti SA, Wilmington DJ, Gallun FJ, Myers PJ, Henry JA.

Department of Veterans Affairs (VA) Rehabilitation Research and Development Service, National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR 97239, USA.

The dramatic escalation of blast exposure in military deployments has created an unprecedented amount of traumatic brain injury (TBI) and associated auditory impairment. Auditory dysfunction has become the most prevalent individual service-connected disability, with compensation totaling more than 1 billion dollars annually. Impairment due to blast can include peripheral hearing loss, central auditory processing deficits, vestibular impairment, and tinnitus. These deficits are particularly challenging in the TBI population, as symptoms can be mistaken for posttraumatic stress disorder, mental-health issues, and cognitive deficits. In addition, comorbid factors such as attention, cognition, neuronal loss, noise toxicity, etc., can confound assessment, causing misdiagnosis. Furthermore, some auditory impairments, such as sensorineural hearing loss, will continue to progress with age, unlike many other injuries. In the TBI population, significant clinical challenges are the accurate differentiation of auditory and vestibular impairments from multiple, many times overlapping, symptoms and the development of multidisciplinary rehabilitation strategies to improve treatment outcomes and quality of life for these patients.

PMID 20104403

6. BMC Ear Nose Throat Disord. 2009 Dec 29;9:13.

An evaluation of the cost-effectiveness of booklet-based self-management of dizziness in primary care, with and without expert telephone support.

Yardley L, Kirby S, Barker F, Little P, Raftery J, King D, Morris A, Mullee M.

School of Psychology, University of Southampton, Highfield, Southampton, UK.

BACKGROUND: Dizziness is a very common symptom that often leads to reduced quality of life, anxiety and emotional distress, loss of fitness, lack of confidence in balance, unsteadiness and an increased risk of falling. Most dizzy patients are managed in primary care by reassurance and medication to suppress symptoms. Trials have shown that chronic dizziness can be treated effectively in primary care using a self-help booklet to teach patients vestibular rehabilitation exercises that promote neurological adaptation and skill and confidence in balance. However, brief support from a trained nurse was provided in these trials, and this model of managing dizzy patients has not been taken up due to a lack of skills and resources in primary care. The aim of this trial is to evaluate two new alternative models of delivery that may be more feasible and cost-effective. METHODS/DESIGN: In a single blind two-centre pragmatic controlled trial, we will randomise 330 patients from 30 practices to a) self-help booklet with telephone support from a vestibular therapist, b) self-help booklet alone, c) routine medical care. Symptoms, disability, handicap and quality of life will be assessed by validated questionnaires administered by post at baseline, immediately post-treatment (3 months), and at one year follow-up. The study is powered to test our primary hypothesis, that the self-help booklet with telephone support will be more effective than routine care. We will also explore the effectiveness of the booklet without any support, and calculate the costs of treatment in each arm. DISCUSSION: If our trial indicates that patients can cost-effectively manage their dizziness in primary care, then it can be easily rolled out to relieve the symptoms of the many patients in primary care who currently have chronic, untreated, disabling dizziness. Treatment in primary care may reduce the development of psychological and physical sequelae that cause handicap and require treatment. There is also the potential to reduce the cost to the NHS of treating dizziness by reducing demand for referral to secondary care for specialist assessment and treatment. TRIAL REGISTRATION: ClinicalTrials.gov trial registration ID number: NCT00732797.

PMCID: PMC2810289 PMID 20098640

7. Cases J. 2009 Dec 21;2:9367.

Migraine vestibulopathy in three families with idiopathic scoliosis: a case series.

Uneri A, Polat S, Aydingoz O, Bursali A.

Department of Otorhinolaryngology, Balance Center, Acibadem Health Group Koztayagi Hospital, Istanbul, 34742, Turkey.

INTRODUCTION: We assessed clinical and etiological association between vestibular pathology and idiopathic scoliosis concerning seven members of three families with idiopathic scoliosis. CASE PRESENTATION: The families were referred to neurotology center for evaluation of balance problems. Patients were evaluated thorough anamnesis to relevant vestibular and audiological studies in addition to idiopathic scoliosis assessment. All evaluated scoliotic patients had clinical manifestations of vestibular dysfunctions and migrainous headache. All of the scoliotic patients (seven patients) in these three families were diagnosed as migraine vestibulopathy. CONCLUSION: With the presentation of these three families, we discussed the probable role of the vestibular dysfunctions including migraine vestibulopathy in the development and progression of idiopathic scoliosis.

PMCID: PMC2804012 PMID 20062612

8. J Clin Sleep Med. 2009 Aug 15;5(4):374-5.

Association of idiopathic rapid eye movement sleep behavior disorder in an adult with persistent, childhood onset rhythmic movement disorder.

Xu Z, Anderson KN, Shneerson JM.

Westmead Hospital, Sydney, Australia.

We present a case of a 41-year-old man with the association of REM sleep behavior disorder (RBD) and rhythmic movement disorder (RMD). The RMD had a childhood onset and persisted into adulthood. The RMD worsened with the development of RBD and has persisted despite successful treatment of RBD. However, the pathogenesis of RMD remains unclear and the movements have been suggested to play a maturational role as part of psychomotor development by stimulating the vestibular apparatus. Current models underlying the control of REM sleep may need to be refined to explain the observed association of RBD and RMD.

PMCID: PMC2725259 PMID 19968018

9. PLoS One. 2009 Nov 11;4(11):e7786.

Disorganized innervation and neuronal loss in the inner ear of Slitrk6-deficient mice.

Katayama K, Zine A, Ota M, Matsumoto Y, Inoue T, Fritzsch B, Aruga J.

Laboratory for Behavioral and Developmental Disorders, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan.

Slitrks are type I transmembrane proteins that share conserved leucine-rich repeat domains similar to those in the secreted axonal guidance molecule Slit. They also show similarities to Ntrk neurotrophin receptors in their carboxy-termini, sharing a conserved tyrosine residue. Among 6 Slitrk family genes in mammals, Slitrk6 has a unique expression pattern, with strong expression in the sensory epithelia of the inner ear. We generated Slitrk6-knockout mice and investigated the development of their auditory and vestibular sensory organs. Slitrk6-deficient mice showed pronounced reduction in the cochlear innervation. In the vestibule, the innervation to the posterior crista was often lost, reduced, or sometimes misguided. These defects were accompanied by the loss of neurons in the spiral and vestibular ganglia. Cochlear sensory epithelia from Slitrk6-knockout mice have reduced ability in promoting neurite outgrowth of spiral ganglion neurons. Indeed the Slitrk6-deficient inner ear showed a mild but significant decrease in the expression of Bdnf and Ntf3, both of which are essential for the innervation and survival of sensory neurons. In addition, the expression of Ntrk receptors, including their phosphorylated forms was decreased in Slitrk6-knockout cochlea. These results suggest that Slitrk6 promotes innervation and survival of inner ear sensory neurons by regulating the expression of trophic and/or tropic factors including neurotrophins from sensory epithelia.

PMCID: PMC2777407 PMID 19936227

10. Dev Biol. 2010 Feb 1;338(1):38-49. Epub 2009 Nov 10.

Requirement for Lmo4 in the vestibular morphogenesis of mouse inner ear.

Deng M, Pan L, Xie X, Gan L.

University of Rochester Flaum Eye Institute, University of Rochester, Rochester, NY 14642, USA.

During development, compartmentalization of an early embryonic structure produces blocks of cells with distinct properties and developmental potentials. The auditory and vestibular components of vertebrate inner ears are derived from defined compartments within the otocyst during embryogenesis. The vestibular apparatus, including three semicircular canals, saccule, utricle, and their associated sensory organs, detects angular and linear acceleration of the head and relays the information through vestibular neurons to vestibular nuclei in the brainstem. How the early developmental events manifest vestibular structures at the molecular level is largely unknown. Here, we show that LMO4, a LIM-domain-only transcriptional regulator, is required for the formation of semicircular canals and their associated sensory cristae. Targeted disruption of Lmo4 resulted in the dysmorphogenesis of the vestibule and in the absence of three semicircular canals, anterior and posterior cristae. In Lmo4-null otocysts, canal outpouches failed to form and cell proliferation was reduced in the dorsolateral region. Expression analysis of the known otic markers showed that Lmo4 is essential for the normal expression of Bmp4, Fgf10, Msx1, Isl1, Gata3, and Dlx5 in the dorsolateral domain of the otocyst, whereas the initial compartmentalization of the otocyst remains unaffected. Our results demonstrate that Lmo4 controls the development of the dorsolateral otocyst into semicircular canals and cristae through two distinct mechanisms: regulating the expression of otic specific genes and stimulating the proliferation of the dorsolateral part of the otocyst.

PMCID: PMC2812651 PMID 19913004 [

11. Acta Otolaryngol. 2010 Apr;130(4):420-8.

The intravestibular source of the vestibular aqueduct. II: its structure and function clarified by a developmental study of the intra-skeletal channels of the otic capsule.

Michaels L, Soucek S, Linthicum F.

University College London Ear Institute and Department of Cellular Pathology, UCL Medical School, University Street, London. UK. l.michaels@ucl.ac.uk

CONCLUSION: A developmental histologic study of the otic capsule indicates that it grows a system of lamellar bone with abundant interconnecting intraosseous channels. These include the 'cartilage canals' in the cartilage model, the chondro-osseous and Haversian-like (Volkmann's) canals in the ossified otic capsule, the fissula ante fenestram, which seems to function as a lifelong manufacturer of the latter two channels, and the inner layer (vestibular arch) of the vestibular aqueduct, which is a complex series of Volkmann's canals and microcanals. Chemical changes, possibly produced by breakdown of cells within the channels, may provide a homeostatic environment for the functions of hearing and balance that take place in the endolymphatic fluid. OBJECTIVES: We studied the development of the otic capsule to clarify the cellular appearances that we had previously described in the normal vestibular arch and the changes in that structure in Ménière's disease. METHODS: Step sections from 84 temporal bones, including those from fetuses, children and adults from a variety of ages were examined histologically. RESULTS: Cartilage canals, bringing blood vessels and mesenchymal cells from perichondrium to the depths of the cartilage model to mediate ossification, are found early in fetal life and disappear when ossification is complete at about 24 weeks. The otic capsule is formed of chondro-osseous canals, which are composed of trabeculae of mineralized cartilage lacunae containing mesenchymal cells that undergo ossification (globuli ossei); also Volkmann's canals (like Haversian canals in long bones but multidirectional), which are produced from osteoblasts. The lumina of the latter frequently link up with chondro-osseous canals. Lamellar bone forms the background of the otic capsule. The fissula ante fenestram is present from early in the cartilage model and then throughout life. It appears to mediate bone production and the new formation of chondro-osseous channels and Volkmann's canals. The internal layer of the vestibular aqueduct (vestibular arch) is seen in the cartilage model of the otic capsule (present in early fetal life) as a vascular layer of perichondrally derived connective tissue (not cartilage) surrounding the endolymphatic duct. When endochondral ossification starts, the bone from the adjoining cochlear and vestibular sides embrace this connective tissue layer to form the outer bony layer of the vestibular aqueduct. Osteoblasts then fill the inner layer with lamellar bone and macro- and mini-Volkmann's canals. At 1 year osteoblasts in the walls of macro-Volkmann's canals, proliferating thereafter throughout life, produce large numbers of microcanals. It is possible that slow breakdown of these osteoblasts and of similar cells in the canals of the otic capsule proper may contribute to the homeostasis of the endolymphatic duct and that of the rest of the membranous labyrinth, respectively.

PMCID: PMC2865695 PMID 19895329

12. Diagn Interv Radiol. 2009 Dec;15(4):239-41. Epub 2009 Oct 27.

Posttraumatic labyrinthitis ossificans with perilymphatic fistulization.

Aralaşmak A, Dinçer E, Arslan G, Cevikol C, Karaali K.

Department of Radiology, Akdeniz University School of Medicine, Antalya, Turkey. aysearalasmak@hotmail.com

Labyrinthitis ossificans is fibrosis or ossification of the membranous labyrinth. Tympanogenic, meningogenic, and hematogenous etiologies are more common than trauma in the development of labyrinthitis ossificans. We present a case complaining of right-sided hearing loss and symptoms of otitis media and positional vertigo resulting from perilymphatic fistulization. Imaging revealed labyrinthitis ossificans secondary to temporal bone fracture crossing through the otic capsule.

PMID 19862674

13. Nan Fang Yi Ke Da Xue Xue Bao. 2009 Oct;29(10):2118-21.

[Cochlear implant in patients with congenital malformation of the inner ear]

[Article in Chinese]

Wan LC, Guo MH, Qian YH, Liu SX, Zhang HZ, Chen SJ, Chen H, Gong J.

Department of Otolaryngology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China. wanliangcai@126.com

OBJECTIVE: To summarize the clinical experience with multi-channel cochlear implantation in patients with inner ear malformations and evaluate and the outcomes of speech rehabilitation. METHODS: A retrospective study was conducted in 295 patients receiving cochlear implantation from 1998 to 2007, including 25 patients with large vestibular aqueduct syndrome (LVAS), 9 with Modini malformation, and 5 with common cavity deformity. All the patients received the Nucleus24 cochlear implants. In LVAS cases, 4 had Nucleus 24R (ST) implants, 8 had Contuor implants, 10 had Contuor Advance, and the remaining cases used Nucleus24(M) straight-electrode implants. RESULTS: Severe gusher appeared in 3 cases of LVAS, and perilymph fluctuation were seen in other 15 cases. Four patients with Mondini malformation and 2 with common cavity malformation also experienced severe gusher, but the electrodes were inserted smoothly in all the patients without postoperative facial paralysis or cerebrospinal fluid leakage. The hearing threshold in these patients was similar to that in patients with normal cochlear structure. After speech rehabilitation for over 6 months, the abilities of speech discrimination and spoken language improved in all the cases in comparison with the preoperative lingual functions. CONCLUSION: Multi-channel cochlear implantation can be performed in patients with inner ear malformation, but should not be attempted in patients with poor cochlear and cochlear nerve development. A comprehensive pre-operative radiographic and audiological evaluation is essential.

PMID 19861281

14. Acta Otorrinolaringol Esp. 2009 Sep-Oct;60(5):318-24. Epub 2009 Jul 24.

[CSF fistulae following surgery for cerebellopontine angle tumours and their relationship with the body mass index]

[Article in Spanish]

Diaz Anadon A, Lassaletta L, Roda JM, Gavilán Bouzas J.

Servicio de Otorrinolaringología, Hospital Universitario La Paz, España. aguedadiazanadon@gmail.com

INTRODUCTION: The most frequent complication after vestibular schwannoma surgery is cerebrospinal fluid (CSF) fistula. MATERIAL AND METHODS: Retrospective study of 170 patients who had vestibular schwannoma (163) or other tumours in the cerebello pontine angle (CPA) (7). Resection was carried out using different approaches: retrosigmoid (66%), translabyrinthine (24%), middle cranial fossa (5%) and others (5%). We studied the day of onset, location and treatment of the CSF leaks, and the influence of demographic, radiological and clinical variables, including Body Mass Index. RESULTS: 27 patients developed a CSF fistula (15.9%): 15 were incisional (8.8%), 8 patients developed CSF rhinorrhea (4.7%), 1 CSF otorrhea (0.6%) and 3 a combination of the above (1.8%). We controlled 11 CSF fistulae with bed rest and compressive dressings (6.5%), 7 required lumbar drainage (4.1%), 2 lumbar drainage and wound closure with local anaesthesia (1.2%) and 7 patients required returning to the operating room under general anaesthesia (4.1%). There was not a significant relationship between the apparition of CSF and tumour size, type of approach, age or body mass index (BMI). CONCLUSIONS: Despite the great development and new surgical techniques, CSF fistulae are still a frequent complication after VS surgery. There might be other aetiological factors such as intracranial pressure. There was no significant relationship between CSF fistula and BMI. Adequate management and early conservative measures led to reduced reintervention rates of less than 5% in all patients.

PMID 19814983 [PubMed - indexed for MEDLINE]

15. J Neurosci. 2009 Oct 7;29(40):12477-83.

Vestibular asymmetry as the cause of idiopathic scoliosis: a possible answer from Xenopus.

Lambert FM, Malinvaud D, Glaunès J, Bergot C, Straka H, Vidal PP.

Centre National de la Recherche Scientifique , Unité Mixte de Recherche 7060-Université Paris Descartes, 75006 Paris, France.

Human idiopathic scoliosis is characterized by severe deformations of the spine and skeleton. The occurrence of vestibular-related deficits in these patients is well established but it is unclear whether a vestibular pathology is the common cause for the scoliotic syndrome and the gaze/posture deficits or if the latter behavioral deficits are a consequence of the scoliotic deformations. A possible vestibular origin was tested in the frog Xenopus laevis by unilateral removal of the labyrinthine endorgans at larval stages. After metamorphosis into young adult frogs, X-ray images and three-dimensional reconstructed micro-computer tomographic scans of the skeleton showed deformations similar to those of scoliotic patients. The skeletal distortions consisted of a curvature of the spine in the frontal and sagittal plane, a transverse rotation along the body axis and substantial deformations of all vertebrae. In terrestrial vertebrates, the initial postural syndrome after unilateral labyrinthectomy recovers over time and requires body weight-supporting limb proprioceptive information. In an aquatic environment, however, this information is absent. Hence, the lesion-induced asymmetric activity in descending spinal pathways and the resulting asymmetric muscular tonus persists. As a consequence the mostly cartilaginous skeleton of the frog tadpoles progressively deforms. Lack of limb proprioceptive signals in an aquatic environment is thus the element, which links the Xenopus model with human scoliosis because a comparable situation occurs during gestation in utero. A permanently imbalanced activity in descending locomotor/posture control pathways might be the common origin for the observed structural and behavioral deficits in humans as in the different animal models of scoliosis.

PMID 19812323 [PubMed - indexed for MEDLINE]

16. Theor Biol Med Model. 2009 Sep 1;6:19.

A model analysis of static stress in the vestibular membranes.

Pender DJ.

Department of Otolaryngology, Columbia University Medical Center New York, USA. djp2@columbia.edu

BACKGROUND: The scheme of the core vestibular membranes, consisting of serially connected utricle, ampulla and semicircular canal, first appeared hundreds of millions of years ago in primitive fish and has remained largely unchanged during the subsequent course of evolution. The labyrinths of higher organisms build on this core structure, with the addition of the phylogenetically newer membrane structures, namely, saccule, lagena and cochlea. An analysis of static stress in these core vestibular membranes may contribute to a better understanding of the role of stress in the evolution of derivative membrane structures over the long term as well as the short-term membrane distortions seen in Meniere's disease. METHODS: A model of these core vestibular membranes is proposed in order to analyze the distribution of stress in the walls of the component chambers. The model uses basic geometrical elements of hollow cylinders and spheres to emulate the actual structures. These model elements lend themselves to a mathematical analysis of static stress in their membranes. RESULTS: Hoop stress, akin to the stress in hoops used to reinforce barrel walls, is found to be the predominant stress in the model membranes. The level of hoop stress depends not only on pressure but as well on a geometric stress factor that incorporates membrane shape, thickness and curvature. This result implies that hoop stress may be unevenly distributed in the membranes of the several vestibular chambers due to variations in these dimensional parameters. These results provide a theoretical framework for appraising hoop stress levels in any vestibular labyrinth whose dimensions are known. CONCLUSION: Static hoop stress disparities are likely to exist in the vestibular membranes given their complex physical configurations. Such stress disparities may contribute to the development of membrane pathologies as seen in Meniere's Disease. They may also factor in the evolutionary development of other derivative membrane structures such as the saccule, the lagena, and the cochlea found in higher animals.

PMCID: PMC2745365 PMID 19723316 [PubMed - indexed for MEDLINE]

17. J Neurosci. 2009 Aug 26;29(34):10779-83.

Long-term potentiation in the rat medial vestibular nuclei depends on locally synthesized 17beta-estradiol.

Grassi S, Frondaroli A, Dieni C, Scarduzio M, Pettorossi VE.

Department of Internal Medicine, Section of Human Physiology, University of Perugia, I-06126 Perugia, Italy. sgrassi@unipg.it

In male rat brainstem slices, we investigated the involvement of locally synthesized 17beta-estradiol (E(2)) in the induction in the medial vestibular nucleus (MVN) of long-term potentiation (LTP) by high-frequency stimulation (HFS) of the primary vestibular afferents. We demonstrated that the blockade of aromatase by letrozole or of E(2) receptors (ERalpha and ERbeta) by ICI 182,780 prevented the HFS-induced LTP of the N1 wave of the evoked field potential (FP) without affecting baseline responses. Only prolonged afferent activation could induce low LTP. In contrast, HFS applied under a combined blockade of GABA(A) receptors and aromatase or ERs was still able to induce LTP, but it was significantly lower and slower. These findings demonstrate that E(2) does not have a tonic influence on the activity of the MVN neurons and provide the first evidence of the crucial role played by local synthesis of E(2) in inducing LTP. We suggest that the synthesis of E(2) occurs after aromatase activation during HFS and facilitates the development of vestibular synaptic plasticity by influencing glutamate and GABA transmission.

PMID 19710328 [PubMed - indexed for MEDLINE]

18. Tidsskr Nor Laegeforen. 2009 Aug 13;129(15):1469-73.

[Neurofibromatosis type 2 and auditory brainstem implantation]

[Article in Norwegian]

Elvsåshagen T, Solyga V, Bakke SJ, Heiberg A, Kerty E.

Avdeling for nevropsykiatri og psykosomatisk medisin, Nevroklinikken, Oslo universitetssykehus, Rikshospitalet 0027 Oslo og Institutt for psykiatri Det medisinske fakultet, Universitetet i Oslo, Norway. torbjorn.elvsashagen@rikshospitalet.no

BACKGROUND: Neurofibromatosis type 2 (NF2) is a rare and severe autosomal dominant disorder caused by mutations in a tumour suppressor gene. This article reviews NF2 and its treatment with auditory brainstem implantation. MATERIAL AND METHODS: The review is based on the authors' experience with the disease and literature identified through a non-systematic search of PubMed. RESULTS: NF2 is caused by loss-of-normal function of the tumour suppressor protein merlin. Merlin normally suppresses cell growth and proliferation. The clinical picture is dominated by neurological symptoms, caused by multiple tumours - mainly schwannomas and meningeomas. The hallmark of the disease is development of bilateral vestibular schwannomas, and the most common presenting symptom in adults is progressive hearing loss. Presenile cataract, ocular motility disorders, peripheral neuropathy and skin tumours are other common findings. The majority of patients become deaf, many patients become severely disabled and life expectancy is reduced. The goal of management is conservation of function and maintenance of quality of life. Auditory brainstem implants stimulate the cochlear nucleus directly and provide substantial auditory benefits to patients with NF2. INTERPRETATION: A multidisciplinary approach in specialty centres is recommended. Management by an experienced team reduces mortality and improves outcome after surgery. Auditory brainstem implantation is an important part of the hearing rehabilitation in these patients. Emerging knowledge of the molecular disease mechanisms offers hope for new therapeutic strategies.

PMID 19690597 [PubMed - indexed for MEDLINE]

19. Development. 2009 Aug;136(16):2837-48.

Nkcc1 (Slc12a2) is required for the regulation of endolymph volume in the otic vesicle and swim bladder volume in the zebrafish larva.

Abbas L, Whitfield TT.

MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield, UK.

Endolymph is the specialised extracellular fluid present inside the inner ear. In mammals, disruptions to endolymph homeostasis can result in either collapse or distension of the endolymphatic compartment in the cochlea, with concomitant hearing loss. The zebrafish little ears (lte) mutant shows a collapse of the otic vesicle in the larva, apparently owing to a loss of endolymphatic fluid in the ear, together with an over-inflation of the swim bladder. Mutant larvae display signs of abnormal vestibular function by circling and swimming upside down. The two available alleles of lte are homozygous lethal: mutant larvae fail to thrive beyond 6 days post-fertilisation. Patterning of the otic vesicle is apparently normal. However, the expression of several genes thought to play a role in endolymph production is downregulated, including the sodium-potassium-chloride cotransporter gene nkcc1 (slc12a2) and several Na(+)/K(+)-ATPase channel subunit genes. We show here that lte mutations correspond to lesions in nkcc1. Each allele has a point mutation that disrupts splicing, leading to frame shifts in the coding region that predict the generation of truncated products. Endolymph collapse in the lte/nkcc1 mutant shows distinct parallels to that seen in mouse Nkcc1 mutants, validating zebrafish as a model for the study of endolymph disorders. The collapse in ear volume can be ameliorated in the to27d allele of lte by injection of a morpholino that blocks splicing at an ectopic site introduced by the mutation. This exemplifies the use of morpholinos as potential therapeutic agents for genetic disease.

PMCID: PMC2730410 PMID 19633174 [PubMed - indexed for MEDLINE]

20. Orphanet J Rare Dis. 2009 Jun 19;4:16.

Neurofibromatosis type 2 (NF2): a clinical and molecular review.

Evans DG.

Medical Genetics Research Group, Regional Genetics Service and National Molecular Genetics Reference Laboratory, Central Manchester Foundation Trust, St Mary's Hospital, Manchester M130JH, UK. dgr.evans@virgin.net

Neurofibromatosis type 2 (NF2) is a tumour-prone disorder characterised by the development of multiple schwannomas and meningiomas. Prevalence (initially estimated at 1: 200,000) is around 1 in 60,000. Affected individuals inevitably develop schwannomas, typically affecting both vestibular nerves and leading to hearing loss and deafness. The majority of patients present with hearing loss, which is usually unilateral at onset and may be accompanied or preceded by tinnitus. Vestibular schwannomas may also cause dizziness or imbalance as a first symptom. Nausea, vomiting or true vertigo are rare symptoms, except in late-stage disease. The other main tumours are schwannomas of the other cranial, spinal and peripheral nerves; meningiomas both intracranial (including optic nerve meningiomas) and intraspinal, and some low-grade central nervous system malignancies (ependymomas). Ophthalmic features are also prominent and include reduced visual acuity and cataract. About 70% of NF2 patients have skin tumours (intracutaneous plaque-like lesions or more deep-seated subcutaneous nodular tumours). Neurofibromatosis type 2 is a dominantly inherited tumour predisposition syndrome caused by mutations in the NF2 gene on chromosome 22. More than 50% of patients represent new mutations and as many as one-third are mosaic for the underlying disease-causing mutation. Although truncating mutations (nonsense and frameshifts) are the most frequent germline event and cause the most severe disease, single and multiple exon deletions are common. A strategy for detection of the latter is vital for a sensitive analysis. Diagnosis is based on clinical and neuroimaging studies. Presymptomatic genetic testing is an integral part of the management of NF2 families. Prenatal diagnosis and pre-implantation genetic diagnosis is possible. The main differential diagnosis of NF2 is schwannomatosis. NF2 represents a difficult management problem with most patients facing substantial morbidity and reduced life expectancy. Surgery remains the focus of current management although watchful waiting with careful surveillance and occasionally radiation treatment have a role. Prognosis is adversely affected by early age at onset, a higher number of meningiomas and having a truncating mutation. In the future, the development of tailored drug therapies aimed at the genetic level are likely to provide huge improvements for this devastating condition.

PMCID: PMC2708144 PMID 19545378 [PubMed - indexed for MEDLINE]

21. J Korean Med Sci. 2009 May;24 Suppl 2:S258-66. Epub 2009 May 31.

Development of guideline for rating the physical impairment of otolaryngologic field.

Park CW, Do NY, Rha KS, Chung SM, Kwon YJ; Korean Academy of Medical Sciences.

Department of Otolaryngology, College of Medicine, Hanyang University, Seoul, Korea. cwpark@hanyang.ac.kr

We develop a guideline for rating the physical impairment of otolaryngologic fields. Assessment of hearing disturbance and tinnitus required physical examination, pure tone audiometry, speech audiometry, impedance audiometry, brainstem evoked response audiometry, Bekesy audiometry, otoacoustic emission test, and imaging examination. History taking, physical examination, and radiological examination for the vestibular organ and brain, righting reflex test, electronystagmography, and caloric test are taken for evaluation of balance disorder. Olfactory function tests include University of Pennsylvania Smell Identification test, Connecticut Chemosensory Clinical Research Center test, T and T olfactometry and Korean Version of Sniffin's Sticks test. Medical history and physical examination is mandatory to evaluatezseverity of respiration difficulty. Examinations include flexible fiberoptic nasopharyngoscope, bronchoscopy, simple soft-tissue radiography films of upper airway and high resolution computed tomography. Evaluation of mastication and swallowing are history taking, physical examination, examination for upper jaw, lower jaw, and temporomandibular joint, dental examination and radiological studies. Endoscopy and esophagography are also needed. Voice disorder is evaluated based on physical examination, oral pharynx and larynx endoscopy, larynx stroboscopy, hearing assessment, laryngeal electromyography, sound analysis test, aerodynamic test, electroglottography, and radiologic examination. Articulation disorder is assessed by picture consonant articulation test. These are position articulation test, Lee-Kim Korean articulation picture and speech intelligibility assessment.

PMCID: PMC2690073 PMID: 19503682 [PubMed - indexed for MEDLINE]

22. BMC Dev Biol. 2009 May 29;9:31.

Tbx1 and Brn4 regulate retinoic acid metabolic genes during cochlear morphogenesis.

Braunstein EM, Monks DC, Aggarwal VS, Arnold JS, Morrow BE.

Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA. ebraunst@aecom.yu.edu

BACKGROUND: In vertebrates, the inner ear is comprised of the cochlea and vestibular system, which develop from the otic vesicle. This process is regulated via inductive interactions from surrounding tissues. Tbx1, the gene responsible for velo-cardio-facial syndrome/DiGeorge syndrome in humans, is required for ear development in mice. Tbx1 is expressed in the otic epithelium and adjacent periotic mesenchyme (POM), and both of these domains are required for inner ear formation. To study the function of Tbx1 in the POM, we have conditionally inactivated Tbx1 in the mesoderm while keeping expression in the otic vesicle intact. RESULTS: Conditional mutants (TCre-KO) displayed malformed inner ears, including a hypoplastic otic vesicle and a severely shortened cochlear duct, indicating that Tbx1 expression in the POM is necessary for proper inner ear formation. Expression of the mesenchyme marker Brn4 was also lost in the TCre-KO. Brn4-;Tbx1+/-embryos displayed defects in growth of the distal cochlea. To identify a potential signal from the POM to the otic epithelium, expression of retinoic acid (RA) catabolizing genes was examined in both mutants. Cyp26a1 expression was altered in the TCre-KO, while Cyp26c1 showed reduced expression in both TCre-KO and Brn4-;Tbx1+/- embryos. CONCLUSION: These results indicate that Tbx1 expression in the POM regulates cochlear outgrowth potentially via control of local retinoic acid activity.

PMCID: PMC2700094 PMID 19476657 [PubMed - indexed for MEDLINE]

23. BMC Ear Nose Throat Disord. 2009 May 16;9:2.

Long-term symptoms in dizzy patients examined in a university clinic.

Wilhelmsen K, Ljunggren AE, Goplen F, Eide GE, Nordahl SH.

Department of Public Health and Primary Health Care, Section for Physiotherapy Science, University of Bergen, Bergen, Norway. Kjersti.Wilhelmsen@hib.no

BACKGROUND: The long-term course of dizziness was investigated combining medical chart and survey data. The survey was undertaken median (interquartile range (IQR)) 4.6 (4.3) years after the initial medical examination. METHODS: Chart data comprised sex, age, diagnosis, symptom duration, postural sway and neck pain. Survey data comprised symptom severity assessed by the Vertigo Symptom Scale - Short Form (VSS-SF), and data regarding current state of dizziness, medication, neck pain and other chronic conditions. RESULTS: The sample consisted of 503 patients, the mean (standard deviation (SD)) age was 50.0 (11.6) years, women being slightly overrepresented (60%). Severe problems with dizziness (VSS-SF mean (SD) 13.9, (10.8)) were indicated in the total group and in 5 of 6 diagnostic sub-groups. Vertigo/balance- and autonomic/anxiety-related symptoms were present in all groups. Current dizziness was confirmed by 73% who had significantly more severe problems than the non-dizzy (VSS-SF mean (SD): 17.2 (10.1) versus 5.0 (7.3)). Symptoms were related to vertigo/balance more than to autonomic/anxiety (test of interaction p < 0.001).Based on simple logistic regression analysis, sex, symptom duration, neck pain, sway and diagnoses predicted dizziness. Symptom duration and neck pain remained predictors in the adjusted analysis. Age, symptom duration, neck pain, sway and diagnoses predicted vertigo/balance-related dizziness in both regression analyses. Sex, neck pain and sway predicted development of autonomic/anxiety-related dizziness according to simple regression analysis, while only neck pain remained a significant predictor in the adjusted analysis. With respect to diagnosis, simple regression analysis showed significant reduced likelihood for development of dizziness in all vestibular sub-groups when compared to the non-otogenic dizziness group. With respect to vertigo/balance- and autonomic/anxiety-related symptoms, the implication of diagnostic belonging varied. No effect of diagnoses was seen in adjusted analyses. CONCLUSION: The majority of patients had persistent and severe problems with dizziness. The wait-and-see attitude before referral to specialist institutions may be questioned. Early, active movements seem necessary, and attention should be paid to the presence of neck pain. Diagnoses had limited prognostic value. Questionnaire-based evaluations could assist in classification and identification of type of dizziness and thereby provide a better basis for specific rehabilitation.

PMCID: PMC2693507 PMID 19445693 [PubMed]

24. PLoS Genet. 2009 May;5(5):e1000480. Epub 2009 May 8.

Synaptojanin1 is required for temporal fidelity of synaptic transmission in hair cells.

Trapani JG, Obholzer N, Mo W, Brockerhoff SE, Nicolson T.

Howard Hughes Medical Institute, Oregon Health and Science University, Portland, OR, USA.

To faithfully encode mechanosensory information, auditory/vestibular hair cells utilize graded synaptic vesicle (SV) release at specialized ribbon synapses. The molecular basis of SV release and consequent recycling of membrane in hair cells has not been fully explored. Here, we report that comet, a gene identified in an ENU mutagenesis screen for zebrafish larvae with vestibular defects, encodes the lipid phosphatase Synaptojanin 1 (Synj1). Examination of mutant synj1 hair cells revealed basal blebbing near ribbons that was dependent on Cav1.3 calcium channel activity but not mechanotransduction. Synaptojanin has been previously implicated in SV recycling; therefore, we tested synaptic transmission at hair-cell synapses. Recordings of post-synaptic activity in synj1 mutants showed relatively normal spike rates when hair cells were mechanically stimulated for a short period of time at 20 Hz. In contrast, a sharp decline in the rate of firing occurred during prolonged stimulation at 20 Hz or stimulation at a higher frequency of 60 Hz. The decline in spike rate suggested that fewer vesicles were available for release. Consistent with this result, we observed that stimulated mutant hair cells had decreased numbers of tethered and reserve-pool vesicles in comparison to wild-type hair cells. Furthermore, stimulation at 60 Hz impaired phase locking of the postsynaptic activity to the mechanical stimulus. Following prolonged stimulation at 60 Hz, we also found that mutant synj1 hair cells displayed a striking delay in the recovery of spontaneous activity. Collectively, the data suggest that Synj1 is critical for retrieval of membrane in order to maintain the quantity, timing of fusion, and spontaneous release properties of SVs at hair-cell ribbon synapses.

PMCID: PMC2673039 PMID 19424431 [PubMed - indexed for MEDLINE]

25. Acta Otorrinolaringol Esp. 2009 Mar-Apr;60(2):131-40.

[An update on the treatment of vestibular schwannoma]

[Article in Spanish]

Lassaletta L, Gavilán J.

Servicio de Otorrinolaringología, Hospital Universitario La Paz, Madrid, Spain. luikilassa@yahoo.com

The increase in the diagnosis of ever smaller vestibular schwannomas (VS), the fact that many tumours can be observed with serial MRI, and the development of radiosurgery as an alternative to microsurgery have led the neurotologic surgeon to a new global approach to patients with VS. On the other hand, the spread of internet-based information sources, often with biased or incomplete information, makes counselling patients with VS a challenging task. This study provides an overview of the natural history of these tumours and the main therapeutic options: observation, surgery and radiosurgery, with comments on their indications, advantages and disadvantages. Due to the completely different approach and peculiar features of bilateral VS in patients with type II neurofibromatosis, these are excluded.

PMID: 19401081 [PubMed - indexed for MEDLINE]

26. Dev Biol. 2009 Apr 15;328(2):285-96. Epub 2009 Feb 2.

Catweasel mice: a novel role for Six1 in sensory patch development and a model for branchio-oto-renal syndrome.

Bosman EA, Quint E, Fuchs H, Hrabé de Angelis M, Steel KP.

The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.

Large-scale mouse mutagenesis initiatives have provided new mouse mutants that are useful models of human deafness and vestibular dysfunction. Catweasel is a novel N-ethyl-N-nitrosourea (ENU)-induced mutation. Heterozygous catweasel mutant mice exhibit mild headtossing associated with a posterior crista defect. We mapped the catweasel mutation to a critical region of 13 Mb on chromosome 12 containing the Six1, -4 and -6 genes. We identified a basepair substitution in exon 1 of the Six1 gene that changes a conserved glutamic acid (E) at position 121 to a glycine (G) in the Six1 homeodomain. Cwe/Cwe animals lack Preyer and righting reflexes, display severe headshaking and have severely truncated cochlea and semicircular canals. Cwe/Cwe animals had very few hair cells in the utricle, but their ampullae and cochlea were devoid of any hair cells. Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion. Lastly we show that Six1 genetically interacts with Jag1. We propose that the catweasel phenotype is due to a hypomorphic mutation in Six1 and that catweasel mice are a suitable model for branchio-oto-renal syndrome. In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

PMCID: PMC2682643 PMID: 19389353 [PubMed - indexed for MEDLINE]

27. PLoS Genet. 2009 Apr;5(4):e1000455. Epub 2009 Apr 17.

Phoenix is required for mechanosensory hair cell regeneration in the zebrafish lateral line.

Behra M, Bradsher J, Sougrat R, Gallardo V, Allende ML, Burgess SM.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA.

In humans, the absence or irreversible loss of hair cells, the sensory mechanoreceptors in the cochlea, accounts for a large majority of acquired and congenital hearing disorders. In the auditory and vestibular neuroepithelia of the inner ear, hair cells are accompanied by another cell type called supporting cells. This second cell population has been described as having stem cell-like properties, allowing efficient hair cell replacement during embryonic and larval/fetal development of all vertebrates. However, mammals lose their regenerative capacity in most inner ear neuroepithelia in postnatal life. Remarkably, reptiles, birds, amphibians, and fish are different in that they can regenerate hair cells throughout their lifespan. The lateral line in amphibians and in fish is an additional sensory organ, which is used to detect water movements and is comprised of neuroepithelial patches, called neuromasts. These are similar in ultra-structure to the inner ear's neuroepithelia and they share the expression of various molecular markers. We examined the regeneration process in hair cells of the lateral line of zebrafish larvae carrying a retroviral integration in a previously uncharacterized gene, phoenix (pho). Phoenix mutant larvae develop normally and display a morphologically intact lateral line. However, after ablation of hair cells with copper or neomycin, their regeneration in pho mutants is severely impaired. We show that proliferation in the supporting cells is strongly decreased after damage to hair cells and correlates with the reduction of newly formed hair cells in the regenerating phoenix mutant neuromasts. The retroviral integration linked to the phenotype is in a novel gene with no known homologs showing high expression in neuromast supporting cells. Whereas its role during early development of the lateral line remains to be addressed, in later larval stages phoenix defines a new class of proteins implicated in hair cell regeneration.

PMCID: PMC2662414 PMID 19381250 [PubMed - indexed for MEDLINE]

28. J Assoc Res Otolaryngol. 2009 Sep;10(3):321-40. Epub 2009 Apr 17.

Hes5 expression in the postnatal and adult mouse inner ear and the drug-damaged cochlea.

Hartman BH, Basak O, Nelson BR, Taylor V, Bermingham-McDonogh O, Reh TA.

Department of Biological Structure, University of Washington, Seattle, WA 98195, USA.

The Notch signaling pathway is known to have multiple roles during development of the inner ear. Notch signaling activates transcription of Hes5, a homologue of Drosophila hairy and enhancer of split, which encodes a basic helix-loop-helix transcriptional repressor. Previous studies have shown that Hes5 is expressed in the cochlea during embryonic development, and loss of Hes5 leads to overproduction of auditory and vestibular hair cells. However, due to technical limitations and inconsistency between previous reports, the precise spatial and temporal pattern of Hes5 expression in the postnatal and adult inner ear has remained unclear. In this study, we use Hes5-GFP transgenic mice and in situ hybridization to report the expression pattern of Hes5 in the inner ear. We find that Hes5 is expressed in the developing auditory epithelium of the cochlea beginning at embryonic day 14.5 (E14.5), becomes restricted to a particular subset of cochlear supporting cells, is downregulated in the postnatal cochlea, and is not present in adults. In the vestibular system, we detect Hes5 in developing supporting cells as early as E12.5 and find that Hes5 expression is maintained in some adult vestibular supporting cells. In order to determine the effect of hair cell damage on Notch signaling in the cochlea, we damaged cochlear hair cells of adult Hes5-GFP mice in vivo using injection of kanamycin and furosemide. Although outer hair cells were killed in treated animals and supporting cells were still present after damage, supporting cells did not upregulate Hes5-GFP in the damaged cochlea. Therefore, absence of Notch-Hes5 signaling in the normal and damaged adult cochlea is correlated with lack of regeneration potential, while its presence in the neonatal cochlea and adult vestibular epithelia is associated with greater capacity for plasticity or regeneration in these tissues; which suggests that this pathway may be involved in regulating regenerative potential.

PMCID: PMC2757554 PMID 19373512 [PubMed - indexed for MEDLINE]

29. BMC Neurosci. 2009 Mar 25;10:27.

Proteomic and functional analysis of NCS-1 binding proteins reveals novel signaling pathways required for inner ear development in zebrafish.

Petko JA, Kabbani N, Frey C, Woll M, Hickey K, Craig M, Canfield VA, Levenson R.

Department of Pharmacology, Penn State College of Medicine, 500 University Drive, Hershey PA 17033, USA. jac554@psu.edu

BACKGROUND: The semicircular canals, a subdivision of the vestibular system of the vertebrate inner ear, function as sensors of angular acceleration. Little is currently known, however, regarding the underlying molecular mechanisms that govern the development of this intricate structure. Zebrafish represent a particularly tractable model system for the study of inner ear development. This is because the ear can be easily visualized during early embryogenesis, and both forward and reverse genetic techniques are available that can be applied to the discovery of novel genes that contribute to proper ear development. We have previously shown that in zebrafish, the calcium sensing molecule neuronal calcium sensor-1 (NCS-1) is required for semicircular canal formation. The function of NCS-1 in regulating semicircular canal formation has not yet been elucidated. RESULTS: We initiated a multistep functional proteomic strategy to identify neuronal calcium sensor-1 (NCS-1) binding partners (NBPs) that contribute to inner ear development in zebrafish. By performing a Y2H screen in combination with literature and database searches, we identified 10 human NBPs. BLAST searches of the zebrafish EST and genomic databases allowed us to clone zebrafish orthologs of each of the human NBPs. By investigating the expression profiles of zebrafish NBP mRNAs, we identified seven that were expressed in the developing inner ear and overlapped with the ncs-1a expression profile. GST pulldown experiments confirmed that selected NBPs interacted with NCS-1, while morpholino-mediated knockdown experiments demonstrated an essential role for arf1, pi4kbeta, dan, and pink1 in semicircular canal formation. CONCLUSION: Based on their functional profiles, the hypothesis is presented that Ncs-1a/Pi4kbeta/Arf1 form a signaling pathway that regulates secretion of molecular components, including Dan and Bmp4, that are required for development of the vestibular apparatus. A second set of NBPs, consisting of Pink1, Hint2, and Slc25a25, are destined for localization in mitochondria. Our findings reveal a novel signalling pathway involved in development of the semicircular canal system, and suggest a previously unrecognized role for NCS-1 in mitochondrial function via its association with several mitochondrial proteins.

PMCID: PMC2679751 PMID: 19320994 [PubMed - indexed for MEDLINE]

30. Acta Otorrinolaringol Esp. 2009 Jan-Feb;60(1):49-53.

[Contribution of the vestibular evoked myogenic potentials to the study of the vestibular neuritis]

[Article in Spanish]

Lesmas Navarro MJ, Pérez Garrigues H, Morera Pérez C, Piqueras A.

Servicio de Otorrinolaringología, Hospital Universitario La Fe, Valencia, España.

INTRODUCTION: Until recently, the only tests available to provide information about vestibular function were caloric and kinetic tests, which only give us information about the external semicircular canal and the superior vestibular nerve. In recent years the development of vestibular evoked myogenic potentials has allowed us to assess the saccule and the inferior vestibular nerve. Our aim is, by studying the caloric test results as well as the vestibular evoked myogenic potentials in patients with Vestibular Neuritis, to determine whether they have involvement of the superior, inferior or both vestibular nerves. MATERIAL AND METHODS: Retrospective study of 9 patients with Vestibular Neuritis admitted to a tertiary care hospital. We studied them by means of anamnesis, otoneurological clinical examination, caloric test and vestibular evoked myogenic potentials. Their clinical progress after admission and any residual instability were also studied. RESULTS: Women were more affected (66.6 %) than males. The mean age for presentation of the disease was 53.8 +/- 14.0 years. Hospital stays lasted for 5.7 +/- 3.2 days. After their crises, they suffered from instability for 122 +/- 114 days. Four cases were diagnosed as Complete Vestibular Neuritis and five as Superior Vestibular Neuritis. P13 wave latency was normal in all cases. There were no differences between the groups in terms of the length of hospital stay nor residual instability. CONCLUSIONS: Nowadays, vestibular evoked myogenic potentials make it possible to advance further in the study of Vestibular Neuritis. Complete and superior vestibular neuritis are much more frequent than inferior vestibular neuritis. Clinical behaviour is similar in the sub-types found.

PMID: 19268130 [PubMed - indexed for MEDLINE]

31. Med Oral Patol Oral Cir Bucal. 2009 Mar 1;14(3):E146-52.

A descriptive study of 113 unerupted supernumerary teeth in 79 pediatric patients in Barcelona.

Ferrés-Padró E, Prats-Armengol J, Ferrés-Amat E.

Service of Oral and Maxillofacial Surgery, Hospital de Nens de Barcelona, Barcelona, Spain.

Unerupted supernumerary teeth, depending on the morphology, number and distribution can give rise to various alterations in the eruption and development of those permanent teeth to which they are related. OBJECTIVES: We aimed to make an epidemiological and descriptive study of the clinical characteristics of patients in Barcelona, their surgical treatment and how said treatment was hindered. MATERIALS AND METHODS: A descriptive study including 113 supernumerary teeth from 79 healthy pediatric patients between 5 and 19 years of age, which underwent surgery in our hospital during a 2 year period (May 2005 / May 2007), taking into account the variables of personal data, gender, age, location, number, morphology, position-axis, radiological study, surgical treatment, related pathologies, and surgical complications. RESULTS: Male patients (51) were more frequently affected than female (28) patients mainly within the central incisors-mesiodens (53.16%), in which the unique form (68.52%) predominates in conoid morphology (69.62%). Surgical treatment was done by palatal/lingual extraction (49.37%), with few surgical complications (only 1 case of post-surgical bleeding). CONCLUSION: Incidence in supernumerary teeth is higher among male patients (ratio M:F of 1.82:1). They are most frequently located in the maxilla (82%), specifically, in the premaxilla (77%). Most cases presented only one supernumerary tooth (68.5%) and, in multiple cases, the premolar region is predominant. The conoid shape is the commonest morphology (69.62%). Surgical extraction, was done by palatal/lingual in 49.37% of the cases, as opposed to the vestibular approach in 45.57%.

PMID: 19242396 [PubMed - indexed for MEDLINE]

32. J Exp Biol. 2009 Mar;212(Pt 5):639-47.

Plasma membrane calcium ATPase required for semicircular canal formation and otolith growth in the zebrafish inner ear.

Cruz S, Shiao JC, Liao BK, Huang CJ, Hwang PP.

Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan.

Fish otoliths consist of >90% calcium carbonate, the accretion of which depends on acellular endolymph. This study confirms the presence of plasma membrane calcium ATPase 1a isoform (Atp2b1a) in the auditory and vestibular system of a teleost fish. As shown by in situ hybridization, zebrafish atp2b1a is expressed mainly in larval otic placode and lateral-line neuromast as well as in the hair cells within the adult zebrafish inner ear chamber. Zebrafish atp2b1a knockdown by antisense morpholinos reduced the number of hair cells and produced malformation of semicircular canals and smaller otoliths. These defects coincide with unbalanced body orientation. The formation of smaller otoliths in atp2b1a morphants may stem from an impairment of calcium supply in the endolymph. However, otolith formation persists in most morphants, suggesting that other zebrafish Atp2b isoforms or paracellular pathways may also transport calcium into the endolymph. These results suggest that Atp2b1a plays an important role for normal development of the auditory and vestibular system as well as calcium transport in the inner ear of zebrafish.

PMID: 19218514 [PubMed - indexed for MEDLINE]

33. PLoS One. 2009;4(2):e4368. Epub 2009 Feb 3.

A late role for bmp2b in the morphogenesis of semicircular canal ducts in the zebrafish inner ear.

Hammond KL, Loynes HE, Mowbray C, Runke G, Hammerschmidt M, Mullins MC, Hildreth V, Chaudhry B, Whitfield TT.

MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom.

BACKGROUND: The Bone Morphogenetic Protein (BMP) genes bmp2 and bmp4 are expressed in highly conserved patterns in the developing vertebrate inner ear. It has, however, proved difficult to elucidate the function of BMPs during ear development as mutations in these genes cause early embryonic lethality. Previous studies using conditional approaches in mouse and chicken have shown that Bmp4 has a role in semicircular canal and crista development, but there is currently no direct evidence for the role of Bmp2 in the developing inner ear. METHODOLOGY/PRINCIPAL FINDINGS: We have used an RNA rescue strategy to test the role of bmp2b in the zebrafish inner ear directly. Injection of bmp2b or smad5 mRNA into homozygous mutant swirl (bmp2b(-/-)) embryos rescues the early patterning defects in these mutants and the fish survive to adulthood. As injected RNA will only last, at most, for the first few days of embryogenesis, all later development occurs in the absence of bmp2b function. Although rescued swirl adult fish are viable, they have balance defects suggestive of vestibular dysfunction. Analysis of the inner ears of these fish reveals a total absence of semicircular canal ducts, structures involved in the detection of angular motion. All other regions of the ear, including the ampullae and cristae, are present and appear normal. Early stages of otic development in rescued swirl embryos are also normal. CONCLUSIONS/SIGNIFICANCE: Our findings demonstrate a critical late role for bmp2b in the morphogenesis of semicircular canals in the zebrafish inner ear. This is the first demonstration of a developmental role for any gene during post-embryonic stages of otic morphogenesis in the zebrafish. Despite differences in the early stages of semicircular canal formation between zebrafish and amniotes, the role of Bmp2 in semicircular canal duct outgrowth is likely to be conserved between different vertebrate species.

PMCID: PMC2629815 PMID: 19190757 [PubMed - indexed for MEDLINE]

34. J Neurosci. 2009 Jan 14;29(2):575-87.

Complementary actions of BDNF and neurotrophin-3 on the firing patterns and synaptic composition of motoneurons.

Davis-López de Carrizosa MA, Morado-Díaz CJ, Tena JJ, Benítez-Temiño B, Pecero ML, Morcuende SR, de la Cruz RR, Pastor AM.

Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.

Neurotrophins, as target-derived factors, are essential for neuronal survival during development, but during adulthood, their scope of actions widens to become also mediators of synaptic and morphological plasticity. Target disconnection by axotomy produces an initial synaptic stripping ensued by synaptic rearrangement upon target reinnervation. Using abducens motoneurons of the oculomotor system as a model for axotomy, we report that trophic support by brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) or a mixture of both, delivered to the stump of severed axons, results in either the prevention of synaptic stripping when administered immediately after lesion or in a promotion of reinnervation of afferents to abducens motoneurons once synaptic stripping had occurred, in concert with the recovery of synaptic potentials evoked from the vestibular nerve. Synaptotrophic effects, however, were larger when both neurotrophins were applied together. The axotomy-induced reduction in firing sensitivities related to eye movements were also restored to normal values when BDNF and NT-3 were administered, but discharge characteristics recovered in a complementary manner when only one neurotrophin was used. This is the first report to show selective retrograde trophic dependence of circuit-driven firing properties in vivo indicating that NT-3 restored the phasic firing, whereas BDNF supported the tonic firing of motoneurons during eye movement performance. Therefore, our data report a link between the synaptotrophic actions of neurotrophins, retrogradely delivered, and the alterations of neuronal firing patterns during motor behaviors. These trophic actions could be responsible, in part, for synaptic rearrangements that alter circuit stability and synaptic balance during plastic events of the brain.

PMID: 19144857 [PubMed - indexed for MEDLINE]

35. Dev Neurobiol. 2009 Feb 1-15;69(2-3):191-202.

Expression of the Pax2 transcription factor is associated with vestibular phenotype in the avian inner ear.

Warchol ME, Richardson GP.

Fay and Carl Simons Center for the Biology of Hearing and Deafness, Washington University School of Medicine, St. Louis, MO 63110, USA. warcholm@ent.wustl.edu

The paired-domain transcription factor Pax2 is involved in many facets of inner ear development, but relatively little is known about the expression or function of Pax2 in the mature ear. In this study, we have used immunohistochemical methods to characterize the expression patterns of Pax2 in the sensory organs of inner ears from posthatch chicks. Immunoreactivity for Pax2 was observed in the nuclei of most hair cells and supporting cells in the vestibular organs. In contrast, Pax2 expression in the chick cochlea was limited to hair cells located in the very distal (low frequency) region. We then used organotypic cultures of the chick utricle to examine changes in Pax2 expression in response to ototoxic injury and during hair cell regeneration. Treatment with streptomycin resulted in the loss of most Pax2 immunoreactivity from the lumenal (hair cell) stratum of the utricle. During the early phases of regeneration, moderate Pax2 expression was maintained in the nuclei of proliferating supporting cells. Expression of Pax2 in the hair cell stratum recovered in parallel with hair cell regeneration. The results indicate that Pax2 continues to be expressed in the mature avian ear, and that its expression pattern is correlated with a vestibular phenotype.

PMCID: PMC2731773 PMID: 19130600 [PubMed - indexed for MEDLINE]

36. Front Hum Neurosci. 2008;2:17. Epub 2008 Dec 3.

The vestibular component in out-of-body experiences: a computational approach.

Schwabe L, Blanke O.

Adaptive and Regenerative Software Systems, Department of Computer Science and Electrical Engineering Rostock, Germany. lars.schwabe@uni-rostock.de

Neurological evidence suggests that disturbed vestibular processing may play a key role in triggering out-of-body experiences (OBEs). Little is known about the brain mechanisms during such pathological conditions, despite recent experimental evidence that the scientific study of such experiences may facilitate the development of neurobiological models of a crucial aspect of self-consciousness: embodied self-location. Here we apply Bayesian modeling to vestibular processing and show that OBEs and the reported illusory changes of self-location and translation can be explained as the result of a mislead Bayesian inference, in the sense that ambiguous bottom-up signals from the vestibular otholiths in the supine body position are integrated with a top-down prior for the upright body position, which we measure during natural head movements. Our findings have relevance for self-location and translation under normal conditions and suggest novel ways to induce and study experimentally both aspects of bodily self-consciousness in healthy subjects.

PMCID: PMC2610253 PMID: 19115017 [PubMed]

37. AJNR Am J Neuroradiol. 2009 May;30(5):992-4. Epub 2008 Nov 27.

Communicating hydrocephalus after gamma knife radiosurgery for vestibular schwannoma: an MR imaging study.

Cauley KA, Ratkovits B, Braff SP, Linnell G.

Department of Radiology, University of Vermont College of Medicine, Burlington, VT, USA. keithcauley@hotmail.com

Vestibular schwannomas are common, and gamma knife radiosurgery is a treatment option of symptomatic tumors. Hydrocephalus may be a complication of gamma knife treatment of vestibular schwannoma, though the cause-and-effect relationship can be debated because tumors can cause hydrocephalus without treatment. We present an MR imaging study of an unusual case of communicating hydrocephalus after gamma knife radiosurgery of a vestibular schwannoma in which the timeline of events strongly suggests that gamma knife played a contributory role in the development of hydrocephalus. We discuss risk factors for the development of hydrocephalus after radiation therapy and the role of MR CSF cine-flow study in the evaluation of treatment options for hydrocephalus in this setting.

PMID: 19039040 [PubMed - indexed for MEDLINE]

38. Methods Mol Biol. 2009;493:311-21.

Identification of transcription factor-DNA interactions using chromatin immunoprecipitation assays.

Nie L, Vázquez AE, Yamoah EN.

Department of Otolaryngology, Center for Neuroscience, University of California, Davis CA, USA.

Expression of almost every gene is regulated at the transcription level. Therefore, transcriptional factor Transcription factors, consequently, have marked effects on the fate of a cell by establishing the gene expression patterns that determine biological processes. In the auditory and vestibular systems, transcription factors have been found to be responsible for development, cell growth, and apoptosis. It is vital to identify the transcription factor target genes and the mechanisms by which transcription factors control and guide gene expression and regulation pathways. Compared with earlier methods devised to study transcription factor-DNA interactions, the advantage of the chromatin immunoprecipitation (ChIP) assay is that the interaction of a transcription factor with its target genes is captured in the native context of chromatin in living cells. Therefore, ChIP base assays are powerful tools to identify the direct interaction of transcription factors and their target genes in vivo. More importantly, ChIP assays have been used in combination with molecular biology techniques, such as PCR and real time PCR, gene cloning, and DNA microarrays, to determine the interaction of transcription factor-DNA from a few potential individual targets to genome-wide surveys.

PMCID: PMC2822710 PMID: 18839356 [PubMed - indexed for MEDLINE]

39. Methods Mol Biol. 2009;493:141-62.

Isolation of sphere-forming stem cells from the mouse inner ear.

Oshima K, Senn P, Heller S.

Department of Otolaryngology-HNS, Stanford University School of Medicine, Stanford, CA, USA.

The mammalian inner ear has very limited ability to regenerate lost sensory hair cells. This deficiency becomes apparent when hair cell loss leads to hearing loss as a result of either ototoxic insult or the aging process. Coincidently, with this inability to regenerate lost hair cells, the adult cochlea does not appear to harbor cells with a proliferative capacity that could serve as progenitor cells for lost cells. In contrast, adult mammalian vestibular sensory epithelia display a limited ability for hair cell regeneration, and sphere-forming cells with stem cell features can be isolated from the adult murine vestibular system. The neonatal inner ear, however, does harbor sphere-forming stem cells residing in cochlear and vestibular tissues. Here, we provide protocols to isolate sphere-forming stem cells from neonatal vestibular and cochlear sensory epithelia as well as from the spiral ganglion. We further describe procedures for sphere propagation, cell differentiation, and characterization of inner ear cell types derived from spheres. Sphere-forming stem cells from the mouse inner ear are an important tool for the development of cellular replacement strategies of damaged inner ears and are a bona fide progenitor cell source for transplantation studies.

PMCID: PMC2861714 PMID: 18839346 [PubMed - indexed for MEDLINE]

40. J Vis. 2008 Aug 22;8(11):15.1-10.

Development of visually driven postural reactivity: a fully immersive virtual reality study.

Greffou S, Bertone A, Hanssens JM, Faubert J.

Visual Psychophysics and Perception Laboratory, School of Optometry, University of Montreal, Montreal, Quebec, Canada. selma.greffou@umontreal.ca

The objective of this study was to investigate the development of visually driven postural regulation in typically developing children of different ages. Thirty-two typically developing participants from 5 age groups (5-7 years, 8-11 years, 12-15 years, 16-19 years, or 20-25 years) were asked to stand within a virtual tunnel that oscillated in an anterior-posterior fashion at three different frequencies (0.125, 0.25, and 0.5 Hz). Body sway (BS) and postural perturbations (as measured by velocity root mean squared or vRMS) were measured. Most of the 5- to 7-year-old participants (67%) were unable to remain standing during the dynamic conditions. For older participants, BS decreased significantly with age for all frequencies. Moreover, vRMS decreased significantly from the 8- to 11- through 16- to 19-years age groups (greatest decreases for 0.5 Hz, followed by 0.25-Hz and 0.125-Hz conditions). No difference of frequency or instability was found between the 16- to 19- and 20- to 25-year-old groups for most conditions. Results suggest an over-reliance on visual input relative to proprioceptive and vestibular inputs on postural regulation at young ages (5-7 years). The finding that vRMS decreased significantly with age before stabilizing between 16 and 19 years suggests an important transitory period for sensorimotor development within this age range.

PMID: 18831609 [PubMed - indexed for MEDLINE]

41. Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14609-14. Epub 2008 Sep 15.

A catechol-O-methyltransferase that is essential for auditory function in mice and humans.

Du X, Schwander M, Moresco EM, Viviani P, Haller C, Hildebrand MS, Pak K, Tarantino L, Roberts A, Richardson H, Koob G, Najmabadi H, Ryan AF, Smith RJ, Müller U, Beutler B.

Department of Genetics, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, CA 92037, USA.

We have identified a previously unannotated catechol-O-methyltranferase (COMT), here designated COMT2, through positional cloning of a chemically induced mutation responsible for a neurobehavioral phenotype. Mice homozygous for a missense mutation in Comt2 show vestibular impairment, profound sensorineuronal deafness, and progressive degeneration of the organ of Corti. Consistent with this phenotype, COMT2 is highly expressed in sensory hair cells of the inner ear. COMT2 enzymatic activity is significantly reduced by the missense mutation, suggesting that a defect in catecholamine catabolism underlies the auditory and vestibular phenotypes. Based on the studies in mice, we have screened DNA from human families and identified a nonsense mutation in the human ortholog of the murine Comt2 gene that causes nonsyndromic deafness. Defects in catecholamine modification by COMT have been previously implicated in the development of schizophrenia. Our studies identify a previously undescribed COMT gene and indicate an unexpected role for catecholamines in the function of auditory and vestibular sense organs.

PMCID: PMC2567147 PMID: 18794526 [PubMed - indexed for MEDLINE]

42. J Neurophysiol. 2008 Oct;100(4):2287-99. Epub 2008 Aug 27.

Molecular identity and functional properties of a novel T-type Ca2+ channel cloned from the sensory epithelia of the mouse inner ear.

Nie L, Zhu J, Gratton MA, Liao A, Mu KJ, Nonner W, Richardson GP, Yamoah EN.

Center for Neuroscience, Program in Communication Science, University of California, Davis, 1544 Newton Ct., Davis, CA 95618, USA.

The molecular identity of non-Cav1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca2+-dependent functions is indisputable. Recently, a transient Cav3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in the chicken basilar papilla. The Cav3.1 current promotes spontaneous activity of the developing hair cell, which may be essential for synapse formation. Here, we have isolated and sequenced the full-length complementary DNA of a distinct isoform of Cav3.1 in the mouse inner ear. The channel is derived from alternative splicing of exon14, exon25A, exon34, and exon35. Functional expression of the channel in Xenopus oocytes yielded Ca2+ currents, which have a permeation phenotype consistent with T-type channels. However, unlike most multiion channels, the T-type channel does not exhibit the anomalous mole fraction effect, possibly reflecting comparable permeation properties of divalent cations. The Cav3.1 channel was expressed in sensory and nonsensory epithelia of the inner ear. Moreover, there are profound changes in the expression levels during development. The differential expression of the channel during development and the pharmacology of the inner ear Cav3.1 channel may have contributed to the difficulties associated with identification of the non-Cav1.3 currents.

PMCID: PMC2576198 PMID: 18753322 [PubMed - indexed for MEDLINE]

43. J Neurosci. 2008 Aug 6;28(32):8086-95.

Semicircular canal size determines the developmental onset of angular vestibuloocular reflexes in larval Xenopus.

Lambert FM, Beck JC, Baker R, Straka H.

Laboratoire de Neurobiologie des Réseaux Sensorimoteurs, Centre National de Recherche Scientifique, Unité Mixte de Recherche 7060, Université Paris Descartes, 75270 Paris Cedex 06, France.

Semicircular canals have been sensors of angular acceleration for 450 million years. This vertebrate adaptation enhances survival by implementing postural and visual stabilization during motion in a three-dimensional environment. We used an integrated neuroethological approach in larval Xenopus to demonstrate that semicircular canal dimensions, and not the function of other elements, determines the onset of angular acceleration detection. Before angular vestibuloocular function in either the vertical or horizontal planes, at stages 47 and 48, respectively, each individual component of the vestibuloocular system was shown to be operational: extraocular muscles could be activated, central neural pathways were complete, and canal hair cells were capable of evoking graded responses. For Xenopus, a minimum semicircular canal lumen radius of 60 microm was necessary to permit endolymph displacement sufficient for sensor function at peak accelerations of 400 degrees /s(2). An intra-animal comparison demonstrated that this size is reached in the vertical canals earlier in development than in the horizontal canals, corresponding to the earlier onset of vertical canal-activated ocular motor behavior. Because size constitutes a biophysical threshold for canal-evoked behavior in other vertebrates, such as zebrafish, we suggest that the semicircular canal lumen and canal circuit radius are limiting the onset of vestibular function in all small vertebrates. Given that the onset of gravitoinertial acceleration detection precedes angular acceleration detection by up to 10 d in Xenopus, these results question how the known precise spatial patterning of utricular and canal afferents in adults is achieved during development.

PMCID: PMC2647017 PMID: 18685033 [PubMed - indexed for MEDLINE]

44. Hum Mol Genet. 2008 Nov 1;17(21):3340-56. Epub 2008 Aug 4.

Eya1 gene dosage critically affects the development of sensory epithelia in the mammalian inner ear.

Zou D, Erickson C, Kim EH, Jin D, Fritzsch B, Xu PX.

McLaughlin Research Institute for Biomedical Sciences, Great Falls, MT 59405, USA.

Haploinsufficiency of the transcription co-activator EYA1 causes branchio-oto-renal syndrome, congenital birth defects that account for as many as 2% of profoundly deaf children; however, the underlying cause for its dosage requirement and its specific role in sensory cell development of the inner ear are unknown. Here, an allelic series of Eya1 were generated to study the basis of Eya1 dosage requirements for sensory organ development. Our results show different threshold requirements for the level of Eya1 in different regions of the inner ear. Short and disorganized hair cell sterocilia was observed in wild-type/null heterozygous or hypomorphic/hypomorphic homozygous cochleae. Patterning and gene-marker analyses indicate that in Eya1 hypomorphic/null heterozygous mice, a reduction of Eya1 expression to 21% of normal level causes an absence of cochlear and vestibular sensory formation. Eya1 is initially expressed in the progenitors throughout the epithelium of all six sensory regions, and later on during sensory cell differentiation, its expression becomes restricted to the differentiating hair cells. We provide genetic evidence that Eya1 activity, in a concentration-dependent manner, plays a key role in the regulation of genes known to be important for sensory development. Furthermore, we show that Eya1 co-localizes with Sox2 in the sensory progenitors and both proteins physically interact. Together, our results indicate that Eya1 appears to be upstream of very early events during the sensory organ development, hair cell differentiation and inner-ear patterning. These results also provide a molecular mechanism for understanding how hypomorphic levels of EYA1 cause inner-ear defects in humans.

PMCID: PMC2722896 PMID: 18678597 [PubMed - indexed for MEDLINE]

45. J Comp Neurol. 2008 Oct 1;510(4):378-95.

Comprehensive Wnt-related gene expression during cochlear duct development in chicken.

Sienknecht UJ, Fekete DM.

Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.

The avian cochlear duct houses both a vestibular and auditory sensory organ (the lagena macula and basilar papilla, respectively), which each have a distinct structure and function. Comparative mRNA in situ hybridization mapping conducted over the time course of chicken cochlear duct development reveals that Wnt-related gene expression is concomitant with various developmental processes such as regionalization, convergent extension of the cochlear duct, cell fate specification, synaptogenesis, and the establishment of planar cell polarity. Wnts mostly originate from nonsensory tissue domains, whereas the sensory primordia preferentially transcribe Frizzled receptors, suggesting that paracrine Wnt signaling predominates in the cochlear duct. Superimposed over this is the strong expression of two secreted Frizzled-related Wnt inhibitors that tend to show complementary expression patterns. Frzb (SFRP3) is confined to the nonsensory cochlear duct and the lagena macula, whereas SFRP2 is maintained in the basilar papilla along with Fzd10 and Wnt7b. Flanking the basilar papilla are Wnt7a, Wnt9a, Wnt11, and SFRP2 on the neural side and Wnt5a, Wnt5b, and Wnt7a on the abneural side. The lateral nonsensory cochlear duct continuously expresses Frzb and temporarily expresses Wnt6 and SFRP1. Characteristic for the entire lagena is the expression of Frzb; in the lagena macula are Fzd1, Fzd7, and Wnt7b, and in the nonsensory tissues are Wnt4 and Wnt5a. Auditory hair cells preferentially express Fzd2 and Fzd9, whereas the main receptors expressed in vestibular hair cells are Fzd1 and Fzd7, in addition to Fzd2 and Fzd9.

PMCID: PMC2566905 PMID: 18671253 [PubMed - indexed for MEDLINE]

46. Braz J Otorhinolaryngol. 2008 May-Jun;74(3):342-9.

Audiological study of an elderly Brazilian population.

do Carmo LC, Médicis da Silveira JA, Marone SA, D'Ottaviano FG, Zagati LL, Dias von Söhsten Lins EM.

University of São Paulo Medical School, Brazil.

The Brazilian elderly population is growing, and already represents 8,6% of our total population. Environmental factors, lifestyle, gender and genetics impact the development of presbycusis, which reduces quality of life. AIM: investigate audiologic and vestibular complaints in the elderly; perform tonal audiometry and check to see if there are differences between genders. STUDY: Cross-sectional clinical prospective study. MATERIALS AND METHODS: 320 elderly patients (160 men and 160 women) were submitted to audiologic interview and tonal audiometry. The results were statistically analyzed by the following methods: ANOVA, Mann-Whitney and Chi-Squared. RESULTS: audiologic and vestibular complaints (hearing loss, tinnitus, ear fullness, dizziness) were similar between the genders (except for dizziness: p<0,05); tonal audiometry showed a significant difference, with hearing loss in the high frequencies among men; and among women the curves were descending and flat. These results were statistically significant (P<0,001). CONCLUSION: our results lead us to conclude that, when the genders are compared, hearing loss in the elderly has similar symptoms; however, there are significant differences in tonal audiometry.

PMID: 18661006 [PubMed - indexed for MEDLINE]

47. J Neurosci. 2008 Jun 25;28(26):6633-41.

Jxc1/Sobp, encoding a nuclear zinc finger protein, is critical for cochlear growth, cell fate, and patterning of the organ of corti.

Chen Z, Montcouquiol M, Calderon R, Jenkins NA, Copeland NG, Kelley MW, Noben-Trauth K.

Sections on Neurogenetics, Laboratory of Molecular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, Maryland 20850, USA.

The mouse cochlea emerges from the ventral pole of the otocyst to form a one and three-quarter coil. Little is known about the factors that control the growth of the cochlea. Jackson circler (jc) is a recessive mutation causing deafness resulting from a growth arrest of the cochlea duct at day 13.5 of embryonic development. Here, we identify the vertebrate homolog of the Drosophila Sobp (sine oculis-binding protein) gene (named Jxc1) in the jc locus. Jxc1 encodes a nuclear protein that has two FCS-type zinc finger domains (PS51024) and bears nuclear localization signals and highly conserved sequence motifs. Transiently expressed wild-type protein is targeted to the nucleus, but mutant isoforms were mislocalized in the cytoplasm. In jc mutants, the cellular patterning of the organ of Corti is severely disrupted, exhibiting supernumerary hair cells at the apex, showing mirror-image duplications of tunnel of Corti and inner hair cells, and expressing ectopic vestibular-like hair cells within Kölliker's organ. Jxc1 mRNA was detected in inner ear sensory hair cells, supporting cells, and the acoustic ganglia. Expression was also found in the developing retina, olfactory epithelium, trigeminal ganglion, and hair follicles. Collectively, our data support a role for Jxc1 in controlling a critical step in cochlear growth, cell fate, and patterning of the organ of Corti.

PMCID: PMC2556235 PMID: 18579736 [PubMed - indexed for MEDLINE]

48. J Comp Neurol. 2008 Aug 20;509(6):661-76.

Espin actin-cytoskeletal proteins are in rat type I spiral ganglion neurons and include splice-isoforms with a functional nuclear localization signal.

Sekerková G, Zheng L, Mugnaini E, Bartles JR.

Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA. g-sekerkova@northwestern.edu

The espins are Ca(2+)-resistant actin-bundling proteins that are enriched in hair cell stereocilia and sensory cell microvilli. Here, we report a novel localization of espins to a large proportion of rat type I spiral ganglion neurons (SGNs) and their projections to the cochlear nucleus (CN). Moreover, we show that a fraction of these espins is in the nucleus of SGNs owing to the presence of splice-isoforms that contain a functional nuclear localization signal (NLS). Espin antibody labeled approximately 83% of type I SGNs, and the labeling intensity increased dramatically during early postnatal development. Type II SGNs and vestibular ganglion neurons were unlabeled. In the CN, espin-positive auditory nerve fibers showed a projection pattern typical of type I SGNs, with intense labeling in the nerve root region and posteroventral CN (PVCN). The anteroventral CN (AVCN) showed moderate labeling, whereas the dorsal CN showed weak labeling that was restricted to the deep layer. Espin-positive synaptic terminals were enriched around nerve root neurons and octopus cells in the PVCN and were also found on globular bushy cells and multipolar neurons in the PVCN and AVCN. SGNs expressed multiple espin transcripts and proteins, including splice-isoforms that contain a nonapeptide, which is rich in positively charged amino acids and creates a bipartite NLS. The nonapeptide was necessary to target espin isoforms to the nucleus and was sufficient to target an unrelated protein to the nucleus when joined with the upstream di-arginine-containing octapeptide. The presence of cytoplasmic and nuclear espins in SGNs suggests additional roles for espins in auditory neuroscience. Copyright 2008 Wiley-Liss, Inc.

PMCID: PMC2574652 PMID: 18551532 [PubMed - indexed for MEDLINE]

49. PLoS Genet. 2008 Apr 11;4(4):e1000050.

Bmp4 is essential for the formation of the vestibular apparatus that detects angular head movements.

Chang W, Lin Z, Kulessa H, Hebert J, Hogan BL, Wu DK.

National Institute on Deafness and Other Communication Disorders, NIH, Rockville, Maryland, United States of America.

Angular head movements in vertebrates are detected by the three semicircular canals of the inner ear and their associated sensory tissues, the cristae. Bone morphogenetic protein 4 (Bmp4), a member of the Transforming growth factor family (TGF-beta), is conservatively expressed in the developing cristae in several species, including zebrafish, frog, chicken, and mouse. Using mouse models in which Bmp4 is conditionally deleted within the inner ear, as well as chicken models in which Bmp signaling is knocked down specifically in the cristae, we show that Bmp4 is essential for the formation of all three cristae and their associated canals. Our results indicate that Bmp4 does not mediate the formation of sensory hair and supporting cells within the cristae by directly regulating genes required for prosensory development in the inner ear such as Serrate1 (Jagged1 in mouse), Fgf10, and Sox2. Instead, Bmp4 most likely mediates crista formation by regulating Lmo4 and Msx1 in the sensory region and Gata3, p75Ngfr, and Lmo4 in the non-sensory region of the crista, the septum cruciatum. In the canals, Bmp2 and Dlx5 are regulated by Bmp4, either directly or indirectly. Mechanisms involved in the formation of sensory organs of the vertebrate inner ear are thought to be analogous to those regulating sensory bristle formation in Drosophila. Our results suggest that, in comparison to sensory bristles, crista formation within the inner ear requires an additional step of sensory and non-sensory fate specification.

PMCID: PMC2274953 PMID: 18404215 [PubMed - indexed for MEDLINE]

50. Braz J Otorhinolaryngol. 2008 Jan-Feb;74(1):125-31.

Mobile phones: influence on auditory and vestibular systems.

Balbani AP, Montovani JC.

Faculdade de Medicina de Botucatu, UNESP, SP, Brazil. a_balbani@hotmail.com

Erratum in:

   Rev Bras Otorrinolaringol (Engl Ed). 2008 Mar-Apr;74(2):319.

Telecommunications systems emit radiofrequency, which is an invisible electromagnetic radiation. Mobile phones operate with microwaves (450900 MHz in the analog service, and 1,82,2 GHz in the digital service) very close to the users ear. The skin, inner ear, cochlear nerve and the temporal lobe surface absorb the radiofrequency energy. AIM: literature review on the influence of cellular phones on hearing and balance. STUDY DESIGN: systematic review. METHODS: We reviewed papers on the influence of mobile phones on auditory and vestibular systems from Lilacs and Medline databases, published from 2000 to 2005, and also materials available in the Internet. RESULTS: Studies concerning mobile phone radiation and risk of developing an acoustic neuroma have controversial results. Some authors did not see evidences of a higher risk of tumor development in mobile phone users, while others report that usage of analog cellular phones for ten or more years increase the risk of developing the tumor. Acute exposure to mobile phone microwaves do not influence the cochlear outer hair cells function in vivo and in vitro, the cochlear nerve electrical properties nor the vestibular system physiology in humans. Analog hearing aids are more susceptible to the electromagnetic interference caused by digital mobile phones. CONCLUSION: there is no evidence of cochleo-vestibular lesion caused by cellular phones.

PMID: 18392513 [PubMed - indexed for MEDLINE]

51. J Neurosurg. 2008 Apr;108(4):751-6.

The vestibular aqueduct: site of origin of endolymphatic sac tumors.

Lonser RR, Baggenstos M, Kim HJ, Butman JA, Vortmeyer AO.

Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1414, USA. lonserr@ninds.nih.gov

Comment in:

   J Neurosurg. 2008 Sep;109(3):569-70; author reply 570.

OBJECT: Although endolymphatic sac tumors (ELSTs) frequently destroy the posterior petrous bone and cause hearing loss, the anatomical origin of these neoplasms is unknown. To determine the precise topographic origin of ELSTs, the authors analyzed the imaging, operative, and pathological findings in patients with von Hippel-Lindau disease (VHL) and ELSTs. METHODS: Consecutive VHL patients with small (<or= 1.5 cm) ELSTs who underwent resection at the National Institutes of Health were included. Clinical, imaging, operative, and pathological findings were analyzed. RESULTS: Ten consecutive VHL patients (6 male and 4 female) with 10 small ELSTs (<or= 1.5 cm; 9 left, 1 right) were included. Serial imaging captured the development of 6 ELSTs and revealed that they originated within the intraosseous (vestibular aqueduct) portion of the endolymphatic duct/sac system. Imaging just before surgery demonstrated that the epicenters of 9 ELSTs (1 ELST was not visible on preoperative imaging) were in the vestibular aqueduct. Inspection during surgery established that all 10 ELSTs were limited to the intraosseous endolymphatic duct/sac and the immediately surrounding region. Histological analysis confirmed tumor within the intraosseous portion (vestibular aqueduct) of the endolymphatic duct/sac in all 10 patients. CONCLUSIONS: ELSTs originate from endolymphatic epithelium within the vestibular aqueduct. High-resolution imaging through the region of the vestibular aqueduct is essential for diagnosis. Surgical exploration of the endolymphatic duct and sac is required for complete resection.

PMCID: PMC2770700 PMID: 18377255 [PubMed - indexed for MEDLINE]

52. Acta Otorrinolaringol Esp. 2008 Feb;59(2):76-9.

[Peripheral vertigo classification. Consensus document. Otoneurology committee of the Spanish otorhinolaryngology society (2003-2006)]

[Article in Spanish]

Morera C, Pérez H, Pérez N, Soto A; Comisión de Otoneurología de la Sociedad Española de Otorrinolaringología.

Hospital Universitario la Fe, Universidad de Valencia, Valencia, España.

There are many different vertigo classifications and different denominations are frequently used for the same clinical processes. The Otoneurology Committee of the Spanish Society for Otorhinolaryngology and Head and Neck Pathology proposes an eminently practical classification of peripheral vertigo to facilitate a common terminology that can be easily used by the general ENT practitioners. The methodology used has been by consensus within our Society and especially among the most outstanding work groups in the area of otoneurology in Spain. Initially vertigo is divided into single-episode vertigo and recurring attacks of vertigo, and these are then sub-divided into 2 groups, depending on whether or not hearing loss is present. Acute vertigo without hearing loss corresponds to vestibular neuritis and if it is associated with hearing loss, it is due to labyrinthitis of different aetiologies and cochleo-vestibular neuritis. Recurrent vertigos without hearing loss are classified as induced, either by posture (BPPV) or pressure (perilymphatic fistula), or as spontaneous, including migraine-associated vertigo, metabolic vertigo, childhood paroxysmal vertigo and vertigo of vascular causes (AITs, vertebral-basilar failure). Finally, recurrent vertigo with hearing loss includes Ménière's disease and others such as vertigo-migraine (with hearing loss), autoimmune pathology of the inner ear, syphilitic infection, and perilymphatic fistula (with hearing loss).

PMID: 18341864 [PubMed - indexed for MEDLINE]

53. Development. 2008 Apr;135(8):1427-37. Epub 2008 Mar 13.

A core cochlear phenotype in USH1 mouse mutants implicates fibrous links of the hair bundle in its cohesion, orientation and differential growth.

Lefèvre G, Michel V, Weil D, Lepelletier L, Bizard E, Wolfrum U, Hardelin JP, Petit C.

Unité de Génétique des Déficits Sensoriels, UMRS587 INSERM-Université Paris VI, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris cedex 15, France.

The planar polarity and staircase-like pattern of the hair bundle are essential to the mechanoelectrical transduction function of inner ear sensory cells. Mutations in genes encoding myosin VIIa, harmonin, cadherin 23, protocadherin 15 or sans cause Usher syndrome type I (USH1, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa leading to blindness) in humans and hair bundle disorganization in mice. Whether the USH1 proteins are involved in common hair bundle morphogenetic processes is unknown. Here, we show that mouse models for the five USH1 genetic forms share hair bundle morphological defects. Hair bundle fragmentation and misorientation (25-52 degrees mean kinociliary deviation, depending on the mutant) were detected as early as embryonic day 17. Abnormal differential elongation of stereocilia rows occurred in the first postnatal days. In the emerging hair bundles, myosin VIIa, the actin-binding submembrane protein harmonin-b, and the interstereocilia-kinocilium lateral link components cadherin 23 and protocadherin 15, all concentrated at stereocilia tips, in accordance with their known in vitro interactions. Soon after birth, harmonin-b switched from the tip of the stereocilia to the upper end of the tip link, which also comprises cadherin 23 and protocadherin 15. This positional change did not occur in mice deficient for cadherin 23 or protocadherin 15. We suggest that tension forces applied to the early lateral links and to the tip link, both of which can be anchored to actin filaments via harmonin-b, play a key role in hair bundle cohesion and proper orientation for the former, and in stereociliary elongation for the latter.

PMID: 18339676 [PubMed - indexed for MEDLINE]

54. Dev Dyn. 2008 Apr;237(4):941-52.

The transmembrane inner ear (tmie) gene contributes to vestibular and lateral line development and function in the zebrafish (Danio rerio).

Shen YC, Jeyabalan AK, Wu KL, Hunker KL, Kohrman DC, Thompson DL, Liu D, Barald KF.

Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.

The inner ear is a complex organ containing sensory tissue, including hair cells, the development of which is not well understood. Our long-term goal is to discover genes critical for the correct formation and function of the inner ear and its sensory tissue. A novel gene, transmembrane inner ear (Tmie), was found to cause hearing-related disorders when defective in mice and humans. A homologous tmie gene in zebrafish was cloned and its expression characterized between 24 and 51 hours post-fertilization. Embryos injected with morpholinos (MO) directed against tmie exhibited circling swimming behavior (approximately 37%), phenocopying mice with Tmie mutations; semicircular canal formation was disrupted, hair cell numbers were reduced, and maturation of electrically active lateral line neuromasts was delayed. As in the mouse, tmie appears to be required for inner ear development and function in the zebrafish and for hair cell maturation in the vestibular and lateral line systems as well. (c) 2008 Wiley-Liss, Inc.

PMID: 18330929 [PubMed - indexed for MEDLINE]

55. Behav Neurosci. 2008 Feb;122(1):224-32.

Orbital spaceflight during pregnancy shapes function of mammalian vestibular system.

Ronca AE, Fritzsch B, Bruce LL, Alberts JR.

Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. aronca@wfubmc.edu

Pregnant rats were flown on the NASA Space Shuttle during the early developmental period of their fetuses' vestibular apparatus and onset of vestibular function. The authors report that prenatal spaceflight exposure shapes vestibular-mediated behavior and central morphology. Postflight testing revealed (a) delayed onset of body righting responses, (b) cardiac deceleration (bradycardia) to 70 degrees head-up roll, (c) decreased branching of gravistatic afferent axons, but (d) no change in branching of angular acceleration receptor projections with comparable synaptogenesis of the medial vestibular nucleus in flight relative to control fetuses. Kinematic analyses of the dams' on-orbit behavior suggest that, although the fetal otolith organs are unloaded in microgravity, the fetus' semicircular canals receive high levels of stimulation during longitudinal rotations of the mother's weightless body. Behaviorally derived stimulation from maternal movements may be a significant factor in studies of vestibular sensory development. Taken together, these studies provide evidence that gravity and angular acceleration shape prenatal organization and function within the mammalian vestibular system. Copyright (c) 2008 APA, all rights reserved.

PMCID: PMC2610337 PMID: 18298265 [PubMed - indexed for MEDLINE]

56. J Clin Invest. 2008 Mar;118(3):1176-85.

Mutation of the Cyba gene encoding p22phox causes vestibular and immune defects in mice.

Nakano Y, Longo-Guess CM, Bergstrom DE, Nauseef WM, Jones SM, Bánfi B.

Department of Anatomy and Cell Biology, Inflammation Program, University of Iowa, Iowa City, Iowa, USA.

In humans, hereditary inactivation of either p22(phox) or gp91(phox) leads to chronic granulomatous disease (CGD), a severe immune disorder characterized by the inability of phagocytes to produce bacteria-destroying ROS. Heterodimers of p22(phox) and gp91(phox) proteins constitute the superoxide-producing cytochrome core of the phagocyte NADPH oxidase. In this study, we identified the nmf333 mouse strain as what we believe to be the first animal model of p22(phox) deficiency. Characterization of nmf333 mice revealed that deletion of p22(phox) inactivated not only the phagocyte NADPH oxidase, but also a second cytochrome in the inner ear epithelium. As a consequence, mice of the nmf333 strain exhibit a compound phenotype consisting of both a CGD-like immune defect and a balance disorder caused by the aberrant development of gravity-sensing organs. Thus, in addition to identifying a model of p22(phox)-dependent immune deficiency, our study indicates that a clinically identifiable patient population with an otherwise cryptic loss of gravity-sensor function may exist. Thus, p22(phox) represents a shared and essential component of at least 2 superoxide-producing cytochromes with entirely different biological functions. The site of p22(phox) expression in the inner ear leads us to propose what we believe to be a novel mechanism for the control of vestibular organogenesis.

PMCID: PMC2248803 PMID: 18292807 [PubMed - indexed for MEDLINE]

57. IEEE Rev Biomed Eng. 2008 Jan 1;1:115-142.

Cochlear Implants:System Design, Integration and Evaluation.

Zeng FG, Rebscher S, Harrison WV, Sun X, Feng H.

Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences and Otolaryngology - Head and Neck Surgery, University of California, 364 Med Surg II, Irvine, CA 92697, USA ( fzeng@uci.edu ).

As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120,000 persons worldwide; half of which being pediatric users who are able to develop nearly normal language. Biomedical engineers have played a central role in the design, integration and evaluation of the cochlear implant system, but the overall success is a result of collaborative work with physiologists, psychologists, physicians, educators, and entrepreneurs. This review presents broad yet in-depth academic and industrial perspectives on the underlying research and ongoing development of cochlear implants. The introduction accounts for major events and advances in cochlear implants, including dynamic interplays among engineers, scientists, physicians, and policy makers. The review takes a system approach to address critical issues from design and specifications to integration and evaluation. First, the cochlear implant system design and specifications are laid out. Second, the design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator and electrode arrays. Third, system integration and functional evaluation are presented with respect to safety, reliability, and challenges facing the present and future cochlear implant designers and users. Finally, issues beyond cochlear implants are discussed to address treatment options for the entire spectrum of hearing impairment as well as to use the cochlear implant as a model to design and evaluate other similar neural prostheses such as vestibular and retinal implants.

PMCID: PMC2782849 PMID: 19946565 [PubMed]

58. J Assoc Res Otolaryngol. 2008 Mar;9(1):65-89. Epub 2007 Dec 22.

Sox2 and JAGGED1 expression in normal and drug-damaged adult mouse inner ear.

Oesterle EC, Campbell S, Taylor RR, Forge A, Hume CR.

Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington, CHDD CD176, Box 357923, Seattle, WA 98195-7923, USA. oesterle@u.washington.edu

Inner ear hair cells detect environmental signals associated with hearing, balance, and body orientation. In humans and other mammals, significant hair cell loss leads to irreversible hearing and balance deficits, whereas hair cell loss in nonmammalian vertebrates is repaired by the spontaneous generation of replacement hair cells. Research in mammalian hair cell regeneration is hampered by the lack of in vivo damage models for the adult mouse inner ear and the paucity of cell-type-specific markers for non-sensory cells within the sensory receptor epithelia. The present study delineates a protocol to drug damage the adult mouse auditory epithelium (organ of Corti) in situ and uses this protocol to investigate Sox2 and Jagged1 expression in damaged inner ear sensory epithelia. In other tissues, the transcription factor Sox2 and a ligand member of the Notch signaling pathway, Jagged1, are involved in regenerative processes. Both are involved in early inner ear development and are expressed in developing support cells, but little is known about their expressions in the adult. We describe a nonsurgical technique for inducing hair cell damage in adult mouse organ of Corti by a single high-dose injection of the aminoglycoside kanamycin followed by a single injection of the loop diuretic furosemide. This drug combination causes the rapid death of outer hair cells throughout the cochlea. Using immunocytochemical techniques, Sox2 is shown to be expressed specifically in support cells in normal adult mouse inner ear and is not affected by drug damage. Sox2 is absent from auditory hair cells, but is expressed in a subset of vestibular hair cells. Double-labeling experiments with Sox2 and calbindin suggest Sox2-positive hair cells are Type II. Jagged1 is also expressed in support cells in the adult ear and is not affected by drug damage. Sox2 and Jagged1 may be involved in the maintenance of support cells in adult mouse inner ear.

PMCID: PMC2536811 PMID: 18157569 [PubMed - indexed for MEDLINE]

59. J Neurosci. 2007 Dec 19;27(51):14078-88.

Auditory neurons make stereotyped wiring decisions before maturation of their targets.

Koundakjian EJ, Appler JL, Goodrich LV.

Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Cochlear ganglion neurons communicate sound information from cochlear hair cells to auditory brainstem neurons through precisely wired circuits. Understanding auditory circuit assembly is a significant challenge because of the small size of the otic vesicle and difficulties labeling and imaging embryonic neurons. We used genetic fate mapping in the mouse to visualize the morphologies of individual cochlear ganglion neurons throughout development, from their origin in the Neurogenin1-positive neurogenic domain in the otic vesicle to the formation of connections with targets in the cochlea and in the cochlear nucleus. We found that auditory neurons with different patterns of connectivity arise from discrete populations of Neurogenin1-positive precursors that make stereotyped wiring decisions depending on when and where they are born. Auditory precursors are segregated from vestibular precursors early in neurogenesis. Within this population, cochlear ganglion neurons with type I and type II morphologies are apparent before birth and develop within common pools of precursors. The peripheral projections are initially complex and branched and then become simple and straight after reaching the edge of the sensory epithelium. Subsequently, a small number of projections attain obvious type II morphologies, beginning at embryonic day 16.5 (E16.5), when hair cells begin to differentiate. Centrally, cochlear ganglion axons are topographically organized in the auditory brainstem as early as E15.5, when the cochlear nucleus is still immature. These findings suggest that Neurogenin1 precursors possess intrinsic programs of differentiation that direct early auditory circuit assembly events before the maturation of presynaptic and postsynaptic target cells.

PMID: 18094247 [PubMed - indexed for MEDLINE]

60. Development. 2007 Dec;134(24):4405-15.

Cross-regulation of Ngn1 and Math1 coordinates the production of neurons and sensory hair cells during inner ear development.

Raft S, Koundakjian EJ, Quinones H, Jayasena CS, Goodrich LV, Johnson JE, Segil N, Groves AK.

Gonda Department of Cell and Molecular Biology, House Ear Institute, 2100 West 3rd Street, Los Angeles CA 90057, USA.

Temporal and spatial coordination of multiple cell fate decisions is essential for proper organogenesis. Here, we define gene interactions that transform the neurogenic epithelium of the developing inner ear into specialized mechanosensory receptors. By Cre-loxP fate mapping, we show that vestibular sensory hair cells derive from a previously neurogenic region of the inner ear. The related bHLH genes Ngn1 (Neurog1) and Math1 (Atoh1) are required, respectively, for neural and sensory epithelial development in this system. Our analysis of mouse mutants indicates that a mutual antagonism between Ngn1 and Math1 regulates the transition from neurogenesis to sensory cell production during ear development. Furthermore, we provide evidence that the transition to sensory cell production involves distinct autoregulatory behaviors of Ngn1 (negative) and Math1 (positive). We propose that Ngn1, as well as promoting neurogenesis, maintains an uncommitted progenitor cell population through Notch-mediated lateral inhibition, and Math1 irreversibly commits these progenitors to a hair-cell fate.

PMID: 18039969 [PubMed - indexed for MEDLINE]

61. Int J Dev Biol. 2007;51(6-7):585-95.

Pocket proteins and cell cycle regulation in inner ear development.

Rocha-Sanchez SM, Beisel KW.

Creighton University School of Dentistry, Dept of Oral Biology, Omaha, NE 68178, USA. ssanchez@creighton.edu

Loss of neurosensory cells of the ear, caused by genetic and non-genetic factors, is becoming an increasing problem as people age, resulting in deafness and vestibular disorders. Unveiling useful mechanisms of cell cycle regulation may offer the possibility to generate new cells out of remaining ones, thus providing the cellular basis to induce new hair cell differentiation in the mammalian ear. Here, we provide an overview of cell cycle regulating genes in general and of those studied in the ear in particular. We categorize those genes into regulators that act upstream of the pocket proteins and into those that act downstream of the pocket proteins. The three members of the pocket protein family essentially determine, through interaction with the eight members of the E2F family, whether or not the cell cycle will progress to the S-phase and thus cell division. The abundant presence of one or more members of these families in adult hair cells supports the notion that inhibition of cell cycle progression through these proteins is a lifelong process. Indeed, manipulating some of those proteins, unfortunately, leads to abortive entry into the cell cycle. Combined with recent success to induce hair cell differentiation through molecular therapy, these approaches may provide a viable strategy to restore lost hair cells in the inner ear.

PMID: 17891719 [PubMed - indexed for MEDLINE]

62. Mamm Genome. 2007 Sep;18(9):646-56. Epub 2007 Sep 18.

Targeted knockout and lacZ reporter expression of the mouse Tmhs deafness gene and characterization of the hscy-2J mutation.

Longo-Guess CM, Gagnon LH, Fritzsch B, Johnson KR.

The Jackson Laboratory, Bar Harbor, ME 04609, USA.

The Tmhs gene codes for a tetraspan transmembrane protein that is expressed in hair cell stereocilia. We previously showed that a spontaneous missense mutation of Tmhs underlies deafness and vestibular dysfunction in the hurry-scurry (hscy) mouse. Subsequently, mutations in the human TMHS gene were shown to be responsible for DFNB67, an autosomal recessive nonsyndromic deafness locus. Here we describe a genetically engineered null mutation of the mouse Tmhs gene (Tmhs ( tm1Kjn )) and show that its phenotype is identical to that of the hscy missense mutation, confirming the deleterious nature of the hscy cysteine-to-phenylalanine substitution. In the targeted null allele, the Tmhs promoter drives expression of a lacZ reporter gene. Visualization of beta-galactosidase activity in Tmhs ( tm1Kjn ) heterozygous mice indicates that Tmhs is highly expressed in the cochlear and vestibular hair cells of the inner ear. Expression is first detectable at E15.5, peaks around P0, decreases slightly at P6, and is absent by P15, a duration that supports the involvement of Tmhs in stereocilia development. Tmhs reporter gene expression also was detected in several cranial and cervical sensory ganglia, but not in the vestibular or spiral ganglia. We also describe a new nontargeted mutation of the Tmhs gene, hscy-2J, that causes abnormal splicing from a cryptic splice site within exon 2 and is predicted to produce a functionally null protein lacking 51 amino acids of the wild-type sequence.

PMCID: PMC2613174 PMID: 17876667 [PubMed - indexed for MEDLINE]

63. Development. 2007 Oct;134(20):3615-25. Epub 2007 Sep 12.

Fgf3 is required for dorsal patterning and morphogenesis of the inner ear epithelium.

Hatch EP, Noyes CA, Wang X, Wright TJ, Mansour SL.

Department of Human Genetics, University of Utah, Salt Lake City, UT 84112-5330, USA.

The inner ear, which contains sensory organs specialized for hearing and balance, develops from an ectodermal placode that invaginates lateral to hindbrain rhombomeres (r) 5-6 to form the otic vesicle. Under the influence of signals from intra- and extraotic sources, the vesicle is molecularly patterned and undergoes morphogenesis and cell-type differentiation to acquire its distinct functional compartments. We show in mouse that Fgf3, which is expressed in the hindbrain from otic induction through endolymphatic duct outgrowth, and in the prospective neurosensory domain of the otic epithelium as morphogenesis initiates, is required for both auditory and vestibular function. We provide new morphologic data on otic dysmorphogenesis in Fgf3 mutants, which show a range of malformations similar to those of Mafb (Kreisler), Hoxa1 and Gbx2 mutants, the most common phenotype being failure of endolymphatic duct and common crus formation, accompanied by epithelial dilatation and reduced cochlear coiling. The malformations have close parallels with those seen in hearing-impaired patients. The morphologic data, together with an analysis of changes in the molecular patterning of Fgf3 mutant otic vesicles, and comparisons with other mutations affecting otic morphogenesis, allow placement of Fgf3 between hindbrain-expressed Hoxa1 and Mafb, and otic vesicle-expressed Gbx2, in the genetic cascade initiated by WNT signaling that leads to dorsal otic patterning and endolymphatic duct formation. Finally, we show that Fgf3 prevents ventral expansion of r5-6 neurectodermal Wnt3a, serving to focus inductive WNT signals on the dorsal otic vesicle and highlighting a new example of cross-talk between the two signaling systems.

PMCID: PMC2366212 PMID: 17855431 [PubMed - indexed for MEDLINE]

64. Dev Biol. 2007 Oct 15;310(2):329-40. Epub 2007 Aug 9.

In vivo genetic ablation of the periotic mesoderm affects cell proliferation survival and differentiation in the cochlea.

Xu H, Chen L, Baldini A.

Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030, USA.

Tbx1 is required for ear development in humans and mice. Gene manipulation in the mouse has discovered multiple consequences of loss of function on early development of the inner ear, some of which are attributable to a cell autonomous role in maintaining cell proliferation of epithelial progenitors of the cochlear and vestibular apparata. However, ablation of the mesodermal domain of the gene also results in severe but more restricted abnormalities. Here we show that Tbx1 has a dynamic expression during late development of the ear, in particular, is expressed in the sensory epithelium of the vestibular organs but not of the cochlea. Vice versa, it is expressed in the condensed mesenchyme that surrounds the cochlea but not in the one that surrounds the vestibule. Loss of Tbx1 in the mesoderm disrupts this peri-cochlear capsule by strongly reducing the proliferation of mesenchymal cells. The organogenesis of the cochlea, which normally occurs inside the capsule, was dramatically affected in terms of growth of the organ, as well as proliferation, differentiation and survival of its epithelial cells. This model provides a striking demonstration of the essential role played by the periotic mesenchyme in the organogenesis of the cochlea.

PMCID: PMC2223065 PMID: 17825816 [PubMed - indexed for MEDLINE]

65. Psychosom Med. 2007 Sep-Oct;69(7):700-7. Epub 2007 Aug 31.

Predicting continued dizziness after an acute peripheral vestibular disorder.

Heinrichs N, Edler C, Eskens S, Mielczarek MM, Moschner C.

Institute of Psychology, Technical University of Braunschweig, Spielmannstr. 12a, 38106 Braunschweig, Germany. n.heinrichs@tu-bs.de

OBJECTIVE: To identify individuals at risk of developing ongoing dizziness 3 months after an acute peripheral vestibular disorder episode, which is usually functionally compensated or even healed within a few weeks. METHODS: In a prospective longitudinal study, we assessed fear of bodily sensations and cognitions related to anxiety at the time of hospital admission and 3 months later in 43 patients with an episode of vestibular neuritis (VN) or benign paroxysmal positional vertigo (BPPV). All participants were assessed for mental disorders using a structured clinical interview. RESULTS: Only the interaction between fear of bodily sensations within the first 2 weeks after admission and the type of vestibular disorder predicted the extent of dizzy complaints 3 months later; this accounts for 21% of the variance in a multiple regression analysis. Specifically, the prediction was valid only in patients with VN but not in patients with BPPV. Further analysis demonstrated that the interaction was not due to the peripheral vestibular disorder per se but rather determined by the initial severity of dizziness, which was significantly different in BPPV and VN patients. CONCLUSIONS: The present study demonstrates that, for the development of persistent psychogenic dizziness after a peripheral vestibular disorder, the fear of bodily sensations is only relevant in interaction with the initial severity of dizziness experienced during the acute organic episode. To prevent development of persistent psychogenic dizziness, we feel that our results indicate the need to screen patients with vestibular disorders for at-risk status and offer them psychological support to deal with their symptoms.

PMID: 17766688 [PubMed - indexed for MEDLINE]

66. J Neurosci. 2007 Aug 15;27(33):8940-51.

Dominant-negative inhibition of M-like potassium conductances in hair cells of the mouse inner ear.

Holt JR, Stauffer EA, Abraham D, Géléoc GS.

Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908, USA. jeffholt@virginia.edu

Sensory hair cells of the inner ear express multiple physiologically defined conductances, including mechanotransduction, Ca(2+), Na(+), and several distinct K(+) conductances, all of which are critical for normal hearing and balance function. Yet, the molecular underpinnings and their specific contributions to sensory signaling in the inner ear remain obscure. We sought to identify hair-cell conductances mediated by KCNQ4, which, when mutated, causes the dominant progressive hearing loss DFNA2. We used the dominant-negative pore mutation G285S and packaged the coding sequence of KCNQ4 into adenoviral vectors. We transfected auditory and vestibular hair cells of organotypic cultures generated from the postnatal mouse inner ear. Cochlear outer hair cells and vestibular type I cells that expressed the transfection marker, green fluorescent protein, and the dominant-negative KCNQ4 construct lacked the M-like conductances that typify nontransfected control hair cells. As such, we conclude that the M-like conductances in mouse auditory and vestibular hair cells can include KCNQ4 subunits and may also include KCNQ4 coassembly partners. To examine the function of M-like conductances in hair cells, we recorded from cells transfected with mutant KCNQ4 and injected transduction current waveforms in current-clamp mode. Because the M-like conductances were active at rest, they contributed to the very low potassium-selective input resistance, which in turn hyperpolarized the resting potential and significantly attenuated the amplitude of the receptor potential. Modulation of M-like conductances may allow hair cells the ability to control the amplitude of their response to sensory stimuli.

PMCID: PMC2647843 PMID: 17699675 [PubMed - indexed for MEDLINE]

67. J Physiol. 2007 Sep 15;583(Pt 3):923-43. Epub 2007 Jul 12.

Developmental regulation of the membrane properties of central vestibular neurons by sensory vestibular information in the mouse.

Eugène D, Deforges S, Guimont F, Idoux E, Vidal PP, Moore LE, Vibert N.

Laboratoire de Neurobiologie des Réseaux Sensorimoteurs, UMR 7060, CNRS-Université Paris Descartes, Paris. daniel.eugene@univ-paris5.fr

Comment in:

   J Physiol. 2007 Sep 15;583(Pt 3):815.

The effect of the lack of vestibular input on the membrane properties of central vestibular neurons was studied by using a strain of transgenic, vestibular-deficient mutant KCNE1(-/-) mice where the hair cells of the inner ear degenerate just after birth. Despite the absence of sensory vestibular input, their central vestibular pathways are intact. Juvenile and adult homozygous mutant have a normal resting posture, but show a constant head bobbing behaviour and display the shaker/waltzer phenotype characterized by rapid bilateral circling during locomotion. In juvenile mice, the KCNE1 mutation was associated with a strong decrease in the expression of the calcium-binding proteins calbindin, calretinin and parvalbumin within the medial vestibular nucleus (MVN) and important modifications of the membrane properties of MVN neurons. In adult mice, however, there was almost no difference between the membrane properties of MVN neurons of homozygous and control or heterozygous mutant mice, which have normal inner ear hair cells and show no behavioural symptoms. The expression levels of calbindin and calretinin were lower in adult homozygous mutant animals, but the amount of calcium-binding proteins expressed in the MVN was much greater than in juvenile mice. These data demonstrate that suppression of sensory vestibular inputs during a 'sensitive period' around birth can generate the circling/waltzing behaviour, but that this behaviour is not due to persistent abnormalities of the membrane properties of central vestibular neurons. Altogether, maturation of the membrane properties of central vestibular neurons is delayed, but not impaired by the absence of sensory vestibular information.

PMCID: PMC2277192 PMID: 17627998 [PubMed - indexed for MEDLINE]

68. J Neurophysiol. 2007 Sep;98(3):1549-65. Epub 2007 Jul 11.

Activity of vestibular nuclei neurons during vestibular and optokinetic stimulation in the alert mouse.

Beraneck M, Cullen KE.

Department of Physiology, McGill University, Montreal, Quebec, Canada. Mathieu.beraneck@univ-paris5.fr

As a result of the availability of genetic mutant strains and development of noninvasive eye movements recording techniques, the mouse stands as a very interesting model for bridging the gap among behavioral responses, neuronal response dynamics studied in vivo, and cellular mechanisms investigated in vitro. Here we characterized the responses of individual neurons in the mouse vestibular nuclei during vestibular (horizontal whole body rotations) and full field visual stimulation. The majority of neurons ( approximately 2/3) were sensitive to vestibular stimulation but not to eye movements. During the vestibular-ocular reflex (VOR), these neurons discharged in a manner comparable to the "vestibular only" (VO) neurons that have been previously described in primates. The remaining neurons [eye-movement-sensitive (ES) neurons] encoded both head-velocity and eye-position information during the VOR. When vestibular and visual stimulation were applied so that there was sensory conflict, the behavioral gain of the VOR was reduced. In turn, the modulation of sensitivity of VO neurons remained unaffected, whereas that of ES neurons was reduced. ES neurons were also modulated in response to full field visual stimulation that evoked the optokinetic reflex (OKR). Mouse VO neurons, however, unlike their primate counterpart, were not modulated during OKR. Taken together, our results show that the integration of visual and vestibular information in the mouse vestibular nucleus is limited to a subpopulation of neurons which likely supports gaze stabilization for both VOR and OKR.

PMID: 17625061 [PubMed - indexed for MEDLINE]

69. Gene Expr Patterns. 2007 Aug;7(7):798-807. Epub 2007 May 26.

Expression of LHX3 and SOX2 during mouse inner ear development.

Hume CR, Bratt DL, Oesterle EC.

Department of Otolaryngology - Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, VMBHRC, CHDD, CD176, Box 357923, 1959 NE Pacific, Seattle, WA 98195, USA. hume@u.washington.edu

A cascade of transcription factors is believed to regulate the coordinate differentiation of primordial inner ear cells into the subtypes of hair cells and supporting cells. While candidate genes involved in this process have been identified, the temporal and spatial patterns of expression of many of these have not been carefully described during the extended period of inner ear development and functional maturation. We systematically examined the expression of two such transcription factors, LHX3 and SOX2, from the time of hair cell terminal mitoses into adulthood. We show that LHX3 is expressed specifically in auditory and vestibular hair cells soon after terminal mitoses and persists into the adult in vestibular hair cells. While SOX2 expression is widespread in the inner ear sensory epithelia prior to hair cell differentiation, it has a unique pattern of expression in the mature auditory and vestibular organs.

PMCID: PMC2043117 PMID: 17604700 [PubMed - indexed for MEDLINE]

70. BMC Neurosci. 2007 Jun 18;8:40.

The development of descending projections from the brainstem to the spinal cord in the fetal sheep.

Stockx EM, Anderson CR, Murphy SM, Cooke IR, Berger PJ.

Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia. elaine.stockx@med.monash.edu.au

BACKGROUND: Although the fetal sheep is a favoured model for studying the ontogeny of physiological control systems, there are no descriptions of the timing of arrival of the projections of supraspinal origin that regulate somatic and visceral function. In the early development of birds and mammals, spontaneous motor activity is generated within spinal circuits, but as development proceeds, a distinct change occurs in spontaneous motor patterns that is dependent on the presence of intact, descending inputs to the spinal cord. In the fetal sheep, this change occurs at approximately 65 days gestation (G65), so we therefore hypothesised that spinally-projecting axons from the neurons responsible for transforming fetal behaviour must arrive at the spinal cord level shortly before G65. Accordingly we aimed to identify the brainstem neurons that send projections to the spinal cord in the mature sheep fetus at G140 (term = G147) with retrograde tracing, and thus to establish whether any projections from the brainstem were absent from the spinal cord at G55, an age prior to the marked change in fetal motor activity has occurred. RESULTS: At G140, CTB labelled cells were found within and around nuclei in the reticular formation of the medulla and pons, within the vestibular nucleus, raphe complex, red nucleus, and the nucleus of the solitary tract. This pattern of labelling is similar to that previously reported in other species. The distribution of CTB labelled neurons in the G55 fetus was similar to that of the G140 fetus. CONCLUSION: The brainstem nuclei that contain neurons which project axons to the spinal cord in the fetal sheep are the same as in other mammalian species. All projections present in the mature fetus at G140 have already arrived at the spinal cord by approximately one third of the way through gestation. The demonstration that the neurons responsible for transforming fetal behaviour in early ontogeny have already reached the spinal cord by G55, an age well before the change in motor behaviour occurs, suggests that the projections do not become fully functional until well after their arrival at the spinal cord.

PMCID: PMC1919385 PMID: 17577416 [PubMed - indexed for MEDLINE]

71. J Vestib Res. 2006;16(4-5):179-86.

A critical period for the impact of vestibular sensation on ferret motor development.

Van Cleave S, Shall MS.

Department of Physical Therapy, Virginia Commonwealth University, Richmond, VA 23298-0224, USA.

Children with hearing deficits and hypofunctioning vestibular receptors frequently have delayed motor development. This study focuses on when the vestibular system needs to be active for normal motor behavior development and the maturation of the soleus muscle in the ferret. Both vestibular labyrinths were removed from ferrets at Postnatal day 10 (P10), P21, or P45 and the resulting data were compared with ferrets that had undergone a sham surgery at the same ages. The animals were sacrificed at P120 (young adult ferret). The resulting data from these ferrets revealed that standing and walking balance was significantly affected when the vestibular system was eliminated at or before P21. The soleus of P10 and P21 animals generally had smaller diameter muscle fibers and proportionally less type I Myosin Heavy Chain (MHC) and more type IIX MHC. The twitch contraction time of the soleus of the P21 group was significantly slower than the other groups. It appears that the vestibular system is important to motor and muscle fiber development in the ferret during the period before P21. The eyes are still closed at that age and all of the vestibular receptors are not fully mature. These findings imply a "critical period" for vestibular sensation and the development of a muscle that is important to standing balance.

PMCID: PMC2034323 PMID: 17538206 [PubMed - indexed for MEDLINE]

72. Pain Physician. 2007 May;10(3):467-72.

Hydrocodone use and sensorineural hearing loss.

Ho T, Vrabec JT, Burton AW.

Baylor College of Medicine, Houston, TX, USA.

BACKGROUND: The hydrocodone/acetaminophen combination is one of the most commonly used analgesic preparations. Isolated incidences of suspected association between hydrocodone abuse and rapidly progressive hearing loss have been reported. In this study, we describe the clinical characteristics of 5 patients presenting with progressive hearing loss and a history of hydrocodone use. METHODS: Patients presenting with rapidly progressive bilateral hearing loss who had a documented history of hydrocodone use were selected for the study. The presentation, audiologic findings, associated comorbidities, and treatment outcomes were reviewed. RESULTS: All patients displayed rapidly progressive sensorineural hearing loss without vestibular symptoms. Hearing loss was asymmetric in 3 patients at initial presentation, but progressed to profound loss, usually within months. Steroid treatment has no effect on the progression of the hearing loss. The admitted quantity of hydrocodone consumed ranged from 10 to 300 mg per day. Hepatitis C was the most common comorbidity, present in 60% of the patients. All patients underwent cochlear implantation with satisfactory results. CONCLUSIONS: The chronic use of hydrocodone can be associated with progressive sensorineural hearing loss. Successful auditory rehabilitation can be achieved with cochlear implantation. Genetic polymorphisms of drug metabolizing enzymes as well as associated comorbidities such as hepatitis C infection may be significant in the development of hydrocodone ototoxicity, though additional investigations are necessary.

PMID: 17525781 [PubMed - indexed for MEDLINE]

73. Braz J Otorhinolaryngol. 2007 Jan-Feb;73(1):100-5.

Otoneurologic findings in Type 1 Diabetes mellitus patients.

Rigon R, Rossi AG, Cóser PL.

Federal University of Santa Maria, Santa Maria, RS, Brazil. rafarigon@hotmail.com

Metabolic alterations, as they occur in Diabetes mellitus, have been mentioned in the development and maintenance of complaints related to the vestibular and auditory organs. AIM: To investigate the vestibular system in Type 1 Diabetic mellitus population. MATERIAL AND METHOD: The present study was developed with 19 individuals, being 10 females (52.6%) and 9 males (47.3%), with ages varying from 8 to 25 years old, with medical diagnosis of Type 1 Diabetes mellitus. For result comparison, a control group was selected with others 19 individuals, matching the study group in age and gender. The evaluation protocol encompassed interview, otoscopic inspection, dynamic and static balance evaluation, cerebellar tests and vectoelectronystagmographic evaluation. STUDY DESIGN: Clinical prospective. RESULTS: Alteration in the vectoelectronystagmographic evaluation were found in 36.84% (n=7) Type 1 Diabetes mellitus individuals, being 21.06% (n=4) Peripheral Deficiency Vestibular Syndrome and 15.79% (n=3) Peripheral Irritative Vestibular Syndrome. CONCLUSION: We conclude that Type 1 Diabetes mellitus individuals can have their vestibular organ affected, even if there are no otoneurologic complaints.

PMID: 17505607 [PubMed - indexed for MEDLINE]

74. Am J Hum Genet. 2007 Jun;80(6):1076-89. Epub 2007 Apr 24.

A mutation in CCDC50, a gene encoding an effector of epidermal growth factor-mediated cell signaling, causes progressive hearing loss.

Modamio-Hoybjor S, Mencia A, Goodyear R, del Castillo I, Richardson G, Moreno F, Moreno-Pelayo MA.

Unidad de Genetica Molecular, Hospital Ramon y Cajal, Madrid, Spain.

We previously mapped a novel autosomal dominant deafness locus, DFNA44, by studying a family with postlingual, progressive, nonsyndromic hearing loss. We report here on the identification of a mutation in CCDC50 as the cause of hearing loss in the family. CCDC50 encodes Ymer, an effector of epidermal growth factor (EGF)-mediated cell signaling that is ubiquitously expressed in different organs and has been suggested to inhibit down-regulation of the EGF receptor. We have examined its expression pattern in mouse inner ear. Western blotting and cell transfection results indicate that Ymer is a soluble, cytoplasmic protein, and immunostaining shows that Ymer is expressed in a complex spatiotemporal pattern during inner ear development. In adult inner ear, the expression of Ymer is restricted to the pillar cells of the cochlea, the stria vascularis, and the vestibular sensory epithelia, where it shows spatial overlap with the microtubule-based cytoskeleton. In dividing cells, Ymer colocalizes with microtubules of the mitotic apparatus. We suggest that DFNA44 hearing loss may result from a time-dependent disorganization of the microtubule-based cytoskeleton in the pillar cells and stria vascularis of the adult auditory system.

PMCID: PMC1867096 PMID: 17503326 [PubMed - indexed for MEDLINE]

75. Int J Dev Biol. 2007;51(3):201-9.

Cell proliferation during the early compartmentalization of the Xenopus laevis inner ear.

Quick QA, Serrano EE.

Department of Biology, New Mexico State University, Las Cruces, New Mexico 88033, USA.

The auditory and vestibular endorgans of the inner ear which are essential for the senses of hearing and balance form early during development when the otocyst undergoes a period of rapid growth and compartmentalization. Here we show the spatial and temporal patterns of proliferating cells in the Xenopus laevis inner ear as this organ develops from an otic vesicle at stage 31 until stage 47, an age at which compartmentalization and the initial appearance of sensory structures are evident. Sites of new cell production were identified in specimens at stages 31, 37, 42, 45 and 47 using immunohistochemical methods to detect bromodeoxyuridine (BrdU) incorporation three hours after exposure to this thymidine analogue. Cells undergoing terminal mitosis at stages 37, 42 and 45 were detected by exposing specimens at these stages to BrdU and permitting development to proceed until stage 47. Our results show that while newly replicating cells are uniformly distributed throughout the stage 31 otic vesicle, they are spatially restricted in stages 37 through 45, with few dividing cells visible in the central patches of the emerging sensory epithelia. In contrast, no clear proliferative pattern was discerned at stage 47. BrdU-positive cells that had undergone terminal mitosis at stage 37, 42 and 45 were detected in the central regions of nascent sensory epithelia at stage 47. These findings are consistent with a developmental mechanism in which cells undergoing terminal mitosis during early X. laevis stages contribute to sensory epithelia and in which cell mixing and migration are features of inner ear compartmentalization.

PMID: 17486540 [PubMed - indexed for MEDLINE]

76. Development. 2007 May;134(9):1713-22. Epub 2007 Mar 29.

Opposing gradients of Gli repressor and activators mediate Shh signaling along the dorsoventral axis of the inner ear.

Bok J, Dolson DK, Hill P, Rüther U, Epstein DJ, Wu DK.

National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA.

Organization of the vertebrate inner ear is mainly dependent on localized signals from surrounding tissues. Previous studies demonstrated that sonic hedgehog (Shh) secreted from the floor plate and notochord is required for specification of ventral (auditory) and dorsal (vestibular) inner ear structures, yet it was not clear how this signaling activity is propagated. To elucidate the molecular mechanisms by which Shh regulates inner ear development, we examined embryos with various combinations of mutant alleles for Shh, Gli2 and Gli3. Our study shows that Gli3 repressor (R) is required for patterning dorsal inner ear structures, whereas Gli activator (A) proteins are essential for ventral inner ear structures. A proper balance of Gli3R and Gli2/3A is required along the length of the dorsoventral axis of the inner ear to mediate graded levels of Shh signaling, emanating from ventral midline tissues. Formation of the ventral-most otic region, the distal cochlear duct, requires robust Gli2/3A function. By contrast, the formation of the proximal cochlear duct and saccule, which requires less Shh signaling, is achieved by antagonizing Gli3R. The dorsal vestibular region requires the least amount of Shh signaling in order to generate the correct dose of Gli3R required for the development of this otic region. Taken together, our data suggest that reciprocal gradients of GliA and GliR mediate the responses to Shh signaling along the dorsoventral axis of the inner ear.

PMID: 17395647 [PubMed - indexed for MEDLINE]

77. J Neurosci. 2007 Mar 21;27(12):3139-47.

Asymmetric distribution of prickle-like 2 reveals an early underlying polarization of vestibular sensory epithelia in the inner ear.

Deans MR, Antic D, Suyama K, Scott MP, Axelrod JD, Goodrich LV.

Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Vestibular hair cells have a distinct planar cell polarity (PCP) manifest in the morphology of their stereocilia bundles and the asymmetric localization of their kinocilia. In the utricle and saccule the hair cells are arranged in an orderly array about an abrupt line of reversal that separates fields of cells with opposite polarity. We report that the putative PCP protein Prickle-like 2 (Pk2) is distributed in crescents on the medial sides of vestibular epithelial cells before the morphological polarization of hair cells. Despite the presence of a line of polarity reversal, crescent position is not altered between hair cells of opposite polarity. Frizzled 6 (Fz6), a second PCP protein, is distributed opposite Pk2 along the lateral side of vestibular support cells. Similar to Pk2, the subcellular localization of Fz6 does not differ between cells located on opposite sides of the line of reversal. In addition, in Looptail/Van Gogh-like2 mutant mice Pk2 is distributed asymmetrically at embryonic day 14.5 (E14.5), but this localization is not coordinated between adjacent cells, and the crescents subsequently are lost by E18.5. Together, these results support the idea that a conserved PCP complex acts before stereocilia bundle development to provide an underlying polarity to all cells in the vestibular epithelia and that cells on either side of the line of reversal are programmed to direct the kinocilium in opposite directions with respect to the polarity axis defined by PCP protein distribution.

PMID: 17376975 [PubMed - indexed for MEDLINE]

78. J Physiol. 2007 Jun 15;581(Pt 3):1101-12. Epub 2007 Mar 1.

Developmental changes in potassium currents at the rat calyx of Held presynaptic terminal.

Nakamura Y, Takahashi T.

Department of Neurophysiology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

During early postnatal development, the calyx of Held synapse in the auditory brainstem of rodents undergoes a variety of morphological and functional changes. Among ionic channels expressed in the calyx, voltage-dependent K+ channels regulate transmitter release by repolarizing the nerve terminal. Here we asked whether voltage-dependent K+ channels in calyceal terminals undergo developmental changes, and whether they contribute to functional maturation of this auditory synapse. From postnatal day (P) 7 to P14, K+ currents became larger and faster in activation kinetics, but did not change any further to P21. Likewise, presynaptic action potentials became shorter in duration from P7 to P14 and remained stable thereafter. The density of presynaptic K+ currents, assessed from excised patch recording and whole-cell recordings with reduced [K+]i, increased by 2-3-fold during the second postnatal week. Pharmacological isolation of K+ current subtypes using tetraethylammonium (1 mM) and margatoxin (10 nM) revealed that the density of Kv3 and Kv1 currents underwent a parallel increase, and their activation kinetics became accelerated by 2-3-fold. In contrast, BK currents, isolated using iberiotoxin (100 nM), showed no significant change during the second postnatal week. Pharmacological block of Kv3 or Kv1 channels at P7 and P14 calyceal terminals indicated that the developmental changes of Kv3 channels contribute to the establishment of reliable action potential generation at high frequency, whereas those of Kv1 channels contribute to stabilizing the nerve terminal. We conclude that developmental changes in K+ currents in the nerve terminal contribute to maturation of high-fidelity fast synaptic transmission at this auditory relay synapse.

PMCID: PMC2170855 PMID: 17331991 [PubMed - indexed for MEDLINE]

79. J Neurosci. 2007 Feb 28;27(9):2163-75.

A forward genetics screen in mice identifies recessive deafness traits and reveals that pejvakin is essential for outer hair cell function.

Schwander M, Sczaniecka A, Grillet N, Bailey JS, Avenarius M, Najmabadi H, Steffy BM, Federe GC, Lagler EA, Banan R, Hice R, Grabowski-Boase L, Keithley EM, Ryan AF, Housley GD, Wiltshire T, Smith RJ, Tarantino LM, Müller U.

Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037, USA.

Deafness is the most common form of sensory impairment in the human population and is frequently caused by recessive mutations. To obtain animal models for recessive forms of deafness and to identify genes that control the development and function of the auditory sense organs, we performed a forward genetics screen in mice. We identified 13 mouse lines with defects in auditory function and six lines with auditory and vestibular defects. We mapped several of the affected genetic loci and identified point mutations in four genes. Interestingly, all identified genes are expressed in mechanosensory hair cells and required for their function. One mutation maps to the pejvakin gene, which encodes a new member of the gasdermin protein family. Previous studies have described two missense mutations in the human pejvakin gene that cause nonsyndromic recessive deafness (DFNB59) by affecting the function of auditory neurons. In contrast, the pejvakin allele described here introduces a premature stop codon, causes outer hair cell defects, and leads to progressive hearing loss. We also identified a novel allele of the human pejvakin gene in an Iranian pedigree that is afflicted with progressive hearing loss. Our findings suggest that the mechanisms of pathogenesis associated with pejvakin mutations are more diverse than previously appreciated. More generally, our findings demonstrate that recessive screens in mice are powerful tools for identifying genes that control the development and function of mechanosensory hair cells and cause deafness in humans, as well as generating animal models for disease.

PMID: 17329413 [PubMed - indexed for MEDLINE]

80. Arch Otolaryngol Head Neck Surg. 2007 Feb;133(2):162-8.

The influence of mutations in the SLC26A4 gene on the temporal bone in a population with enlarged vestibular aqueduct.

Madden C, Halsted M, Meinzen-Derr J, Bardo D, Boston M, Arjmand E, Nishimura C, Yang T, Benton C, Das V, Smith R, Choo D, Greinwald J.

Department of Audiovestibular Medicine, Manchester Royal Infirmary, Manchester, England.

Erratum in:

   Arch Otolaryngol Head Neck Surg. 2007 Jun;133(6):607.

OBJECTIVE: To correlate genetic and audiometric findings with a detailed radiologic analysis of the temporal bone in patients with enlarged vestibular aqueduct (EVA) to ascertain the contribution of SLC26A4 gene mutations to this phenotype. DESIGN: A retrospective review of patients with EVA identified in a database of pediatric hearing-impaired patients. SETTING: A tertiary care pediatric referral center. PATIENTS: Seventy-one children with EVA and screening results for SLC26A4 mutations. MAIN OUTCOME MEASURES: Genetic screening results, audiometric thresholds, and radiographic temporal bone measurements. RESULTS: Seventy-one children with EVA were screened for SLC26A4 mutations. Mutations were found in 27% of children overall, while only 8% had biallelic mutations. The mean initial pure-tone average (PTA) was 59 dB; the mean final PTA was 67 dB. A bilateral EVA was found in 48 (67%) of the children; a unilateral EVA was found in 23 (33%). Progressive hearing loss (in at least 1 ear) was seen in 29 (41%) of the patients. The strongest genotype-phenotype interaction was seen in children with a bilateral EVA. Among children with SLC26A4 mutations, there was a significantly wider vestibular aqueduct at the midpoint and a wider vestibule width (P < .05) than in children without the mutation. Among patients with a bilateral EVA, children with any SLC26A4 mutation were more likely to have a more severe final PTA (64 dB vs 32 dB), larger midpoint measurement (2.1 vs 1.1 mm), and larger operculum measurement (3.0 vs 2.0 mm) than those without the mutation in their better-hearing ear (P < .05). CONCLUSIONS: In a population of pediatric patients with an EVA and hearing loss, SLC26A4 mutations are a contributor to the phenotype. Our data suggest that other genetic factors also have important contributions to this phenotype. The presence of an abnormal SLC26A4 allele, even in the heterozygous state, was associated with greater enlargement of the vestibular aqueduct, abnormal development of the vestibule, and possibly a stable hearing outcome.

PMID: 17309986 [PubMed - indexed for MEDLINE]

81. Sheng Li Xue Bao. 2007 Feb 25;59(1):71-8.

Changes of amino acid concentrations in the rat medial vestibular nucleus following unilateral labyrinthectomy.

Yu HL, An Y, Jiang HY, Jin QH, Jin YZ.

Department of Pharmacology, Yanbian University College of Medicine, Yanji 133000, China.

To understand the neurochemical mechanisms underlying the vestibular compensation, we determined the levels of amino acids such as aspartate, glutamate, glutamine, glycine, taurine, alanine in the medial vestibular nucleus (MVN) following unilateral labyrinthectomy (UL), by using in vivo brain microdialysis and high-performance liquid chromatography technique. Rats were pretreated by infusing 2% lidocaine 1.2 mL or 10 mg arsanilic acid into the tympanic cavity to obstruct uni-periphery vestibular organ, and then the levels of amino acids were determined in MVN of normal control and ipsilateral or contralateral lesional (ipsi-/contra-lesional) rats. In the control experiment, the levels of aspartate, glutamate, glutamine, glycine, taurine, and alanine were (6.15 +/- 0.59), (18.13 +/- 1.21), (33.73 +/- 1.67), (9.26 +/- 0.65), (9.56 +/- 0.77) and (10.07 +/- 0.83) pmol/8 muL sample, respectively. The concentrations of aspartate and glutamate decreased, while the concentration of taurine increased in the ipsi-lesional MVN of rats 10 min after infusing 2% lidocaine into middle ear to obstruct uni-periphery vestibular organ. Whereas the concentration of glutamate increased, the concentrations of glycine and alanine decreased in the contra-lesional MVN, accompanied by imbalances of glutamate, glycine and alanine in the bilateral nuclei. In contrast, the levels of glutamate and alanine decreased, the level of glutamine increased in the ipsi-lesional MVN, and the level of glutamate decreased in the contra-lesional MVN of rats 2 weeks after infusing 10 mg arsanilic acid into the tympanic cavity to obstruct uni-periphery vestibular organ. Furthermore, the level of glutamine in the ipsi-lesional MVN was obviously higher than that in the contra-lesional MVN. These results demonstrate that an imbalance of different amino acids appeared in bilateral MVN after UL, and this imbalance decreased after the development of vestibular compensation. Whereas the imbalance of glutamine release in bilateral nuclei appeared after vestibular compensation.

PMID: 17294045 [PubMed - in process]

82. Proc Natl Acad Sci U S A. 2007 Feb 20;104(8):2997-3002. Epub 2007 Feb 9.

Differentiation of ES cells into cerebellar neurons.

Salero E, Hatten ME.

Laboratory of Developmental Neurobiology, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399, USA.

The neuronal circuits of the cerebellar cortex are essential for motor and sensory learning, associative memory formation, and the vestibular ocular reflex. In children and young adults, tumors of the granule cell, the medulloblastomas, represent 40% of brain tumors. We report the differentiation of E14 ES cells into mature granule neurons by sequential treatment with secreted factors (WNT1, FGF8, and RA) that initiate patterning in the cerebellar region of the neural tube, bone morphogenic proteins (BMP6/7 and GDF7) that induce early granule cell progenitor markers (MATH1, MEIS1, ZIC1), mitogens (SHH, JAG1) that control proliferation and induce additional granule cell markers (Cyclin D2, PAX2/6), and culture in glial-conditioned medium to induce markers of mature granule neurons (GABAalpha(6)r), including ZIC2, a unique marker for granule neurons. Differentiated ES cells formed classic "T-shaped" granule cell axons in vitro, and implantation of differentiated Pde1c-Egfp-BAC transgenic ES cells into the external granule cell layer of neonatal mice resulted in the extension of parallel fibers, migration across the molecular layer, incorporation into the internal granule cell layer, and extension of short dendrites, typical of young granule cells forming synaptic connections with afferent mossy fibers. These results underscore the utility of treating ES cells with local, inductive signals that regulate CNS neuronal development in vivo as a strategy for cell replacement therapy of defined neuronal populations.

PMCID: PMC1796781 PMID: 17293457 [PubMed - indexed for MEDLINE]

83. Brain Res. 2007 Mar 30;1139:117-25. Epub 2007 Jan 8.

Developmental expression of Kcnq4 in vestibular neurons and neurosensory epithelia.

Rocha-Sanchez SM, Morris KA, Kachar B, Nichols D, Fritzsch B, Beisel KW.

Department of Oral Biology, Creighton University School of Dentistry, 2500 California Plaza, Omaha, NE 68178, USA. ssanchez@creighton.edu

Sensory signal transduction of the inner ear afferent neurons and hair cells (HCs) requires numerous ionic conductances. The KCNQ4 voltage-gated M-type potassium channel is thought to set the resting membrane potential in cochlear HCs. Here we describe the spatiotemporal expression patterns of Kcnq4 and the associated alternative splice forms in the HCs of vestibular labyrinth. Whole mount immunodetection, qualitative and quantitative RT-PCR were performed to characterize the expression patterns of Kcnq4 transcripts and proteins. A topographical expression and upregulation of Kcnq4 during development was observed and indicated that Kcnq4 is not restricted to either a specific vestibular structure or cell type, but is present in afferent calyxes, vestibular ganglion neurons, and both type I and type II HCs. Of the four alternative splice variants, Kcnq4_v1 transcripts were the predominant form in the HCs, while Kcnq4_v3 was the major variant in the vestibular neurons. Differential quantitative expression of Kcnq4_v1 and Kcnq4_v3 were respectively detected in the striolar and extra-striolar regions of the utricle and saccule. Analysis of gerbils and rats yielded results similar to those obtained in mice, suggesting that the spatiotemporal expression pattern of Kcnq4 in the vestibular system is conserved among rodents. Analyses of vestibular HCs of Bdnf conditional mutant mice, which are devoid of any innervation, demonstrate that regulation of Kcnq4 expression in vestibular HCs is independent of innervation.

PMCID: PMC1858668 PMID: 17292869 [PubMed - indexed for MEDLINE]

84. J Neurosci. 2007 Feb 7;27(6):1474-8.

Sphingosine 1-phosphate (S1P) signaling is required for maintenance of hair cells mainly via activation of S1P2.

Herr DR, Grillet N, Schwander M, Rivera R, Müller U, Chun J.

Department of Molecular Biology, Helen L. Dorris Institute for Neurological and Psychiatric Disorders, La Jolla, California 92037, USA.

Hearing requires the transduction of vibrational forces by specialized epithelial cells in the cochlea known as hair cells. The human ear contains a finite number of terminally differentiated hair cells that, once lost by noise-induced damage or toxic insult, can never be regenerated. We report here that sphingosine 1-phosphate (S1P) signaling, mainly via activation of its cognate receptor S1P2, is required for the maintenance of vestibular and cochlear hair cells in vivo. Two S1P receptors, S1P2 and S1P3, were found to be expressed in the cochlea by reverse transcription-PCR and in situ hybridization. Mice that are null for both these receptors uniformly display progressive cochlear and vestibular defects with hair cell loss, resulting in complete deafness by 4 weeks of age and, with complete penetrance, balance defects of increasing severity. This study reveals the previously unknown role of S1P signaling in the maintenance of cochlear and vestibular integrity and suggests a means for therapeutic intervention in degenerative hearing loss.

PMID: 17287522 [PubMed - indexed for MEDLINE]

85. J Biol Chem. 2007 Apr 6;282(14):10690-6. Epub 2007 Feb 6.

Deafness and stria vascularis defects in S1P2 receptor-null mice.

Kono M, Belyantseva IA, Skoura A, Frolenkov GI, Starost MF, Dreier JL, Lidington D, Bolz SS, Friedman TB, Hla T, Proia RL.

Genetics of Development and Disease Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1821, USA.

The S1P(2) receptor is a member of a family of G protein-coupled receptors that bind the extracellular sphingolipid metabolite sphingosine 1-phosphate with high affinity. The receptor is widely expressed and linked to multiple G protein signaling pathways, but its physiological function has remained elusive. Here we have demonstrated that S1P(2) receptor expression is essential for proper functioning of the auditory and vestibular systems. Auditory brainstem response analysis revealed that S1P(2) receptor-null mice were deaf by one month of age. These null mice exhibited multiple inner ear pathologies. However, some of the earliest cellular lesions in the cochlea were found within the stria vascularis, a barrier epithelium containing the primary vasculature of the inner ear. Between 2 and 4 weeks after birth, the basal and marginal epithelial cell barriers and the capillary bed within the stria vascularis of the S1P(2) receptor-null mice showed markedly disturbed structures. JTE013, an S1P(2) receptor-specific antagonist, blocked the S1P-induced vasoconstriction of the spiral modiolar artery, which supplies blood directly to the stria vascularis and protects its capillary bed from high perfusion pressure. Vascular disturbance within the stria vascularis is a potential mechanism that leads to deafness in the S1P(2) receptor-null mice.

PMID: 17284444 [PubMed - indexed for MEDLINE]

86. Conf Proc IEEE Eng Med Biol Soc. 2005;7:7380-5.

Electrical stimulation to restore vestibular function development of a 3-d vestibular prosthesis.

Della Santina C, Migliaccio A, Patel A.

Departments of Otolaryngology-Head & Neck Surgery and Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA.

Patients who fail to compensate for bilateral loss of vestibular sensory function are disabled by disequilibrium and illusory movement of the visual field during head movement. An implantable prosthesis that restores vestibular sensation could significantly improve quality of life for these patients. To be effective, such a device should encode head rotation in all 3 dimensions. We describe the 3-dimensional angular vestibulo-ocular reflex of normal chinchillas and vestibular-deficient chinchillas undergoing functional electrical stimulation of the vestibular nerve. We also describe the design and fabrication of a head-mounted, 8 electrode vestibular prosthesis that encodes head movement in 3 dimensions.

PMCID: PMC2767263 PMID: 17281986 [PubMed - in process]

87. Mol Cell Neurosci. 2007 Mar;34(3):468-80. Epub 2007 Feb 2.

Novel regional and developmental NMDA receptor expression patterns uncovered in NR2C subunit-beta-galactosidase knock-in mice.

Karavanova I, Vasudevan K, Cheng J, Buonanno A.

Section on Molecular Neurobiology, National Institute of Child Health and Human Development, Bldg. 35, Room 2C-1000, 35 Lincoln Drive, National Institutes of Health, Bethesda, MD 20892, USA.

NMDA receptor "knock-in" mice were generated by inserting the nuclear beta-galactosidase reporter at the NR2C subunit translation initiation site. Novel cell types and dynamic patterns of NR2C expression were identified using these mice, which were unnoticed before because reagents that specifically recognize NR2C-containing receptors are non-existent. We identified a transition zone from NR2C-expressing neurons to astrocytes in an area connecting the retrosplenial cortex and hippocampus. We demonstrate that NR2C is expressed in a subset of S100beta-positive/GFAP-negative glial cells in the striatum, olfactory bulb and cerebral cortex. We also demonstrate novel areas of neuronal expression such as retrosplenial cortex, thalamus, pontine and vestibular nuclei. In addition, we show that during cerebellar development NR2C is expressed in transient caudal-rostral gradients and parasagittal bands in subsets of granule cells residing in the internal granular layer, further demonstrating heterogeneity of granule neurons. These results point to novel functions of NR2C-containing NMDA receptors.

PMCID: PMC1855159 PMID: 17276696 [PubMed - indexed for MEDLINE]

88. Development. 2007 Feb;134(4):647-58.

Tissue/planar cell polarity in vertebrates: new insights and new questions.

Wang Y, Nathans J.

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. ywang@mail.jhmi.edu

This review focuses on the tissue/planar cell polarity (PCP) pathway and its role in generating spatial patterns in vertebrates. Current evidence suggests that PCP integrates both global and local signals to orient diverse structures with respect to the body axes. Interestingly, the system acts on both subcellular structures, such as hair bundles in auditory and vestibular sensory neurons, and multicellular structures, such as hair follicles. Recent work has shown that intriguing connections exist between the PCP-based orienting system and left-right asymmetry, as well as between the oriented cell movements required for neural tube closure and tubulogenesis. Studies in mice, frogs and zebrafish have revealed that similarities, as well as differences, exist between PCP in Drosophila and vertebrates.

PMID: 17259302 [PubMed - indexed for MEDLINE]

89. J Neurosci. 2007 Jan 24;27(4):782-90.

Multiple mechanosensory modalities influence development of auditory function.

Horowitz SS, Tanyu LH, Simmons AM.

Department of Psychology, Brown University, Providence, Rhode Island 02912, USA.

Sensory development can be dependent on input from multiple modalities. During metamorphic development, ranid frogs exhibit rapid reorganization of pathways mediating auditory, vestibular, and lateral line modalities as the animal transforms from an aquatic to an amphibious form. Here we show that neural sensitivity to the underwater particle motion component of sound follows a different developmental trajectory than that of the pressure component. Throughout larval stages, cells in the medial vestibular nucleus show best frequencies to particle motion in the range from 15 to 65 Hz, with displacement thresholds of <10 mum. During metamorphic climax, best frequencies significantly increase, and sensitivity to lower-frequency (<25 Hz) stimuli tends to decline. These findings suggest that continued sensitivity to particle motion may compensate for the considerable loss of sensitivity to pressure waves observed during the developmental deaf period. Transport of a lipophilic dye from peripheral end organs to the dorsal medulla shows that fibers from the saccule in the inner ear and from the anterior lateral line both terminate in the medial vestibular nucleus. Saccular projections remain stable across larval development, whereas lateral line projections degenerate during metamorphic climax. Sensitivity to particle motion may be based on multimodal input early in development and on saccular input alone during the transition to amphibious life.

PMID: 17251417 [PubMed - indexed for MEDLINE]

90. J Anat. 2007 Jan;210(1):78-88.

Neurotrophin and Trk neurotrophin receptors in the inner ear of Salmo salar and Salmo trutta.

Catania S, Germanà A, Cabo R, Ochoa-Erena FJ, Guerrera MC, Hannestad J, Represa J, Vega JA.

Dipartimento di Morfologia, Biochimica, Fisiologia e Produzione Animale, Università di Messina, Italy.

Neurotrophins (NTs) and their signal transducing Trk receptors play a critical role in the development and maintenance of specific neuronal populations in the nervous system of higher vertebrates. They are responsible for the innervation of the inner ear cochlear and vestibular sensory epithelia. Neurotrophins and Trks are also present in teleosts but their distribution in the inner ear is unknown. Thus, in the present study, we used Western-blot analysis and immunohistochemistry to investigate the expression and cell localization of both NTs and Trk receptors in the inner ear of alevins of Salmo salar and Salmo trutta. Western-blot analysis revealed the occurrence of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), but not nerve growth factor (NGF), as well as all three Trk receptors, i.e. TrkA, TrkB and TrkC, the estimated molecular weights of which were similar to those expected for mammals. Specific immunoreactivity for neurotrophins was detected mainly in the sensory epithelia. In particular, BDNF immunoreactivity was found in the maculae of the utricle and saccule, whereas NT-3 immunoreactivity was present in the sensory epithelium of the cristae ampullaris. As a rule the sensory epithelia of the inner ear lacked immunoreactivity for Trks, thus excluding possible mechanisms of autocrinia and/or paracrinia. By contrast, overlapping subpopulations of neurons in the statoacoustic ganglion expressed TrkA (about 15%), TrkB (about 65%) and TrkC (about 45%). The present results demonstrate that, as in mammals and birds, the inner ear of teleosts expresses the components of the neurotrophin-Trk system, but their roles remain to be elucidated.

PMCID: PMC2100255 PMID: 17229285 [PubMed - indexed for MEDLINE]

91. J Assoc Res Otolaryngol. 2007 Mar;8(1):18-31. Epub 2006 Dec 14.

Differential distribution of stem cells in the auditory and vestibular organs of the inner ear.

Oshima K, Grimm CM, Corrales CE, Senn P, Martinez Monedero R, Géléoc GS, Edge A, Holt JR, Heller S.

Department of Otolaryngology-Head & Neck Surgery, Stanford University School of Medicine, 801 Welch Road, Stanford, CA 94305-5739, USA.

The adult mammalian cochlea lacks regenerative capacity, which is the main reason for the permanence of hearing loss. Vestibular organs, in contrast, replace a small number of lost hair cells. The reason for this difference is unknown. In this work we show isolation of sphere-forming stem cells from the early postnatal organ of Corti, vestibular sensory epithelia, the spiral ganglion, and the stria vascularis. Organ of Corti and vestibular sensory epithelial stem cells give rise to cells that express multiple hair cell markers and express functional ion channels reminiscent of nascent hair cells. Spiral ganglion stem cells display features of neural stem cells and can give rise to neurons and glial cell types. We found that the ability for sphere formation in the mouse cochlea decreases about 100-fold during the second and third postnatal weeks; this decrease is substantially faster than the reduction of stem cells in vestibular organs, which maintain their stem cell population also at older ages. Coincidentally, the relative expression of developmental and progenitor cell markers in the cochlea decreases during the first 3 postnatal weeks, which is in sharp contrast to the vestibular system, where expression of progenitor cell markers remains constant or even increases during this period. Our findings indicate that the lack of regenerative capacity in the adult mammalian cochlea is either a result of an early postnatal loss of stem cells or diminishment of stem cell features of maturing cochlear cells.

PMCID: PMC2538418 PMID: 17171473 [PubMed - indexed for MEDLINE]

92. Braz J Biol. 2006 Aug;66(3):907-17.

Notes on the biology of Trypoxylon (Trypargilum) opacum Brèthes (Hymenoptera; Crabronidae) in Southern Brazil.

Buschini ML, Wolff LL.

Depto de Biologia, UNICENTRO, Guarapuava, PR, Brazil. isatunes@yahoo.com.br

The present study investigated the abundance, seasonality and various life-history traits of Trypoxylon (Trypargilum) opacum. Using trap-nests, 320 nests of T. opacum were collected in the Parque Municipal das Araucárias in Southern Brazil (25 degrees 23' 36" S and 51 degrees 27' 19" W) over a 3 year period. Nesting was more frequent during the warm season. Nests consisted of a linear series of 1 to 8 brood cells separated by mud partitions, usually followed by an empty vestibular cell and final-closure mud plug. Brood cells were most commonly provisioned with spiders of the family Araneidae. Sex-ratio was strongly female biased, 3.4:1 females:males. Natural enemies attacking nests T. opacum included chrysidids, ichneumonids, sarcophagids, bombyliids and ants.

PMID: 17119839 [PubMed - indexed for MEDLINE]

93. Dev Dyn. 2007 Jan;236(1):306-13.

Comparative analysis of Gata3 and Gata2 expression during chicken inner ear development.

Lilleväli K, Haugas M, Pituello F, Salminen M.

Institute of Biotechnology, University of Helsinki, Helsinki, Finland.

The inner ear is a complex sensory organ with hearing and balance functions. Gata3 and Gata2 are expressed in the inner ear, and to gain more insight into their roles in otic development, we made a detailed expression analysis in chicken embryos. At early stages, their expression was highly overlapping. At later stages, Gata2 expression became prominent in vestibular and cochlear nonsensory epithelia. In contrast to Gata2, Gata3 was mainly expressed in the developing sensory epithelia, reflecting the importance of this factor in the sensory-neural development of the inner ear. While the later expression patterns of both Gata3 and Gata2 were highly conserved between chicken and mouse, important differences were observed especially with Gata3 during early otic development, providing indications of divergent molecular control during placode invagination in mice and chickens. We also found indications that the regulatory hierarchy observed in mouse, where Gata3 is upstream of Gata2 and Fgf10, could be conserved in chicken.

PMID: 17103399 [PubMed - indexed for MEDLINE]

94. J Assoc Res Otolaryngol. 2006 Dec;7(4):383-98. Epub 2006 Oct 31.

Electrophysiological validation of a human prototype auditory midbrain implant in a guinea pig model.

Lenarz M, Lim HH, Patrick JF, Anderson DJ, Lenarz T.

Otorhinolaryngology Department, Medical University of Hannover, Hannover, Lower Saxony 30625, Germany.

The auditory midbrain implant (AMI) is a new treatment for hearing restoration in patients with neural deafness or surgically inaccessible cochleae who cannot benefit from cochlear implants (CI). This includes neurofibromatosis type II (NF2) patients who, due to development and/or removal of vestibular schwannomas, usually experience complete damage of their auditory nerves. Although the auditory brainstem implant (ABI) provides sound awareness and aids lip-reading capabilities for these NF2 patients, it generally only achieves hearing performance levels comparable with a single-channel CI. In collaboration with Cochlear Ltd. (Lane Cove, Australia), we developed a human prototype AMI, which is designed for electrical stimulation along the well-defined tonotopic gradient of the inferior colliculus central nucleus (ICC). Considering that better speech perception and hearing performance has been correlated with a greater number of discriminable frequency channels of information available, the ability of the AMI to effectively activate discrete frequency regions within the ICC may enable better hearing performance than achieved by the ABI. Therefore, the goal of this study was to investigate if our AMI array could achieve low-threshold, frequency-specific activation within the ICC, and whether the levels for ICC activation via AMI stimulation were within safe limits for human application. We electrically stimulated different frequency regions within the ICC via the AMI array and recorded the corresponding neural activity in the primary auditory cortex (A1) using a multisite silicon probe in ketamine-anesthetized guinea pigs. Based on our results, AMI stimulation achieves lower thresholds and more localized, frequency-specific activation than CI stimulation. Furthermore, AMI stimulation achieves cortical activation with current levels that are within safe limits for central nervous system stimulation. This study confirms that our AMI design is sufficient for ensuring safe and effective activation of the ICC, and warrants further studies to translate the AMI into clinical application.

PMCID: PMC2504634 PMID: 17075701 [PubMed - indexed for MEDLINE]

95. J Neurophysiol. 2007 Feb;97(2):1684-704. Epub 2006 Oct 25.

Developmental changes in two voltage-dependent sodium currents in utricular hair cells.

Wooltorton JR, Gaboyard S, Hurley KM, Price SD, Garcia JL, Zhong M, Lysakowski A, Eatock RA.

Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.

Two kinds of sodium current (I(Na)) have been separately reported in hair cells of the immature rodent utricle, a vestibular organ. We show that rat utricular hair cells express one or the other current depending on age (between postnatal days 0 and 22, P0-P22), hair cell type (I, II, or immature), and epithelial zone (striola vs. extrastriola). The properties of these two currents, or a mix, can account for descriptions of I(Na) in hair cells from other reports. The patterns of Na channel expression during development suggest a role in establishing the distinct synapses of vestibular hair cells of different type and epithelial zone. All type I hair cells expressed I(Na,1), a TTX-insensitive current with a very negative voltage range of inactivation (midpoint: -94 mV). I(Na,2) was TTX sensitive and had less negative voltage ranges of activation and inactivation (inactivation midpoint: -72 mV). I(Na,1) dominated in the striola at all ages, but current density fell by two-thirds after the first postnatal week. I(Na,2) was expressed by 60% of hair cells in the extrastriola in the first week, then disappeared. In the third week, all type I cells and about half of type II cells had I(Na,1); the remaining cells lacked sodium current. I(Na,1) is probably carried by Na(V)1.5 subunits based on biophysical and pharmacological properties, mRNA expression, and immunoreactivity. Na(V)1.5 was also localized to calyx endings on type I hair cells. Several TTX-sensitive subunits are candidates for I(Na,2).

PMID: 17065252 [PubMed - indexed for MEDLINE]

96. J Neurosci. 2006 Oct 4;26(40):10253-69.

M-like K+ currents in type I hair cells and calyx afferent endings of the developing rat utricle.

Hurley KM, Gaboyard S, Zhong M, Price SD, Wooltorton JR, Lysakowski A, Eatock RA.

The Bobby R. Alford Department of Otorhinolaryngology, Head and Neck Surgery, Baylor College of Medicine, Houston, Texas 77030, USA.

Type I vestibular hair cells have large K+ currents that, like neuronal M currents, activate negative to resting potential and are modulatable. In rodents, these currents are acquired postnatally. In perforated-patch recordings from rat utricular hair cells, immature hair cells [younger than postnatal day 7 (P7)] had a steady-state K+ conductance (g(-30)) with a half-activation voltage (V1/2) of -30 mV. The size and activation range did not change in maturing type II cells, but, by P16, type I cells had added a K conductance that was on average fourfold larger and activated much more negatively. This conductance may comprise two components: g(-60) (V1/2 of -60 mV) and g(-80) (V1/2 of -80 mV). g(-80) washed out during ruptured patch recordings and was blocked by a protein kinase inhibitor. M currents can include contributions from KCNQ and ether-a-go-go-related (erg) channels. KCNQ and erg channel blockers both affected the K+ currents of type I cells, with KCNQ blockers being more potent at younger than P7 and erg blockers more potent at older than P16. Single-cell reverse transcription-PCR and immunocytochemistry showed expression of KCNQ and erg subunits. We propose that KCNQ channels contribute to g(-30) and g(-60) and erg subunits contribute to g(-80). Type I hair cells are contacted by calyceal afferent endings. Recordings from dissociated calyces and afferent endings revealed large K+ conductances, including a KCNQ conductance. Calyx endings were strongly labeled by KCNQ4 and erg1 antisera. Thus, both hair cells and calyx endings have large M-like K+ conductances with the potential to control the gain of transmission.

PMID: 17021181 [PubMed - indexed for MEDLINE]

97. J Neurosci. 2006 Oct 4;26(40):10188-98.

The chloride intracellular channel protein CLIC5 is expressed at high levels in hair cell stereocilia and is essential for normal inner ear function.

Gagnon LH, Longo-Guess CM, Berryman M, Shin JB, Saylor KW, Yu H, Gillespie PG, Johnson KR.

The Jackson Laboratory, Bar Harbor, Maine 04609, USA.

Although CLIC5 is a member of the chloride intracellular channel protein family, its association with actin-based cytoskeletal structures suggests that it may play an important role in their assembly or maintenance. Mice homozygous for a new spontaneous recessive mutation of the Clic5 gene, named jitterbug (jbg), exhibit impaired hearing and vestibular dysfunction. The jbg mutation is a 97 bp intragenic deletion that causes skipping of exon 5, which creates a translational frame shift and premature stop codon. Western blot and immunohistochemistry results confirmed the predicted absence of CLIC5 protein in tissues of jbg/jbg mutant mice. Histological analysis of mutant inner ears revealed dysmorphic stereocilia and progressive hair cell degeneration. In wild-type mice, CLIC5-specific immunofluorescence was detected in stereocilia of both cochlear and vestibular hair cells and also along the apical surface of Kolliker's organ during cochlear development. Refined immunolocalization in rat and chicken vestibular hair cells showed that CLIC5 is limited to the basal region of the hair bundle, similar to the known location of radixin. Radixin immunostaining appeared reduced in hair bundles of jbg mutant mice. By mass spectrometry and immunoblotting, CLIC5 was shown to be expressed at high levels in stereocilia of the chicken utricle, in an approximate 1:1 molar ratio with radixin. These results suggest that CLIC5 associates with radixin in hair cell stereocilia and may help form or stabilize connections between the plasma membrane and the filamentous actin core.

PMID: 17021174 [PubMed - indexed for MEDLINE]

98. Dev Dyn. 2006 Nov;235(11):3026-38.

Zebrafish pax5 regulates development of the utricular macula and vestibular function.

Kwak SJ, Vemaraju S, Moorman SJ, Zeddies D, Popper AN, Riley BB.

Biology Department, Texas A&M University, College Station, Texas, USA.

The zebrafish otic vesicle initially forms with only two sensory epithelia, the utricular and saccular maculae, which primarily mediate vestibular and auditory function, respectively. Here, we test the role of pax5, which is preferentially expressed in the utricular macula. Morpholino knockdown of pax5 disrupts vestibular function but not hearing. Neurons of the statoacoustic ganglion (SAG) develop normally. Utricular hair cells appear to form normally but a variable number subsequently undergo apoptosis and are extruded from the otic vesicle. Dendrites of the SAG persist in the utricle but become disorganized after hair cell loss. Hair cells in the saccule develop and survive normally. Otic expression of pax5 requires pax2a and fgf3, mutations in which cause vestibular defects, albeit by distinct mechanisms. Thus, pax5 works in conjunction with fgf3 and pax2a to establish and/or maintain the utricular macula and is essential for vestibular function. (c) 2006 Wiley-Liss, Inc.

PMID: 17013878 [PubMed - indexed for MEDLINE]

99. Development. 2006 Oct;133(19):3837-46.

Ephrin A/EphA controls the rostral turning polarity of a lateral commissural tract in chick hindbrain.

Zhu Y, Guthrie S, Murakami F.

SORST, Japan Science and Technology, Japan. yan.zhu@fbs.osaka-u.ac.jp

Most post-crossing commissural axons turn into longitudinal paths to make synaptic connections with their targets. Mechanisms that control their rostrocaudal turning polarity are still poorly understood. We used the hindbrain as a model system to investigate the rostral turning of a laterally located commissural tract, identified as the caudal group of contralateral cerebellar-projecting second-order vestibular neurons (cC-VC). We found that the caudal hindbrain possessed a graded non-permissive/repulsive activity for growing cC-VC axons. This non-permissiveness/repulsion was in part mediated by glycosyl-phosphatidylinositol (GPI)-anchored ephrin A. We further demonstrated that ephrin A2 was distributed in a caudal-high/rostral-low gradient in the caudolateral hindbrain and cC-VC axons expressed EphA receptors. Finally, perturbing ephrin A/EphA signalling both in vitro and in vivo led to rostrocaudal pathfinding errors of post-crossing cC-VC axons. These results suggest that ephrin A/EphA interactions play a key role in regulating the polarity of post-crossing cC-VC axons as they turn into the longitudinal axis.

PMID: 16968816 [PubMed - indexed for MEDLINE]

100. J Med Genet. 2007 Feb;44(2):153-60. Epub 2006 Sep 8.

Development of a genotyping microarray for Usher syndrome.

Cremers FP, Kimberling WJ, Külm M, de Brouwer AP, van Wijk E, te Brinke H, Cremers CW, Hoefsloot LH, Banfi S, Simonelli F, Fleischhauer JC, Berger W, Kelley PM, Haralambous E, Bitner-Glindzicz M, Webster AR, Saihan Z, De Baere E, Leroy BP, Silvestri G, McKay GJ, Koenekoop RK, Millan JM, Rosenberg T, Joensuu T, Sankila EM, Weil D, Weston MD, Wissinger B, Kremer H.

Department of Human Genetics, and Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. F.Cremers@antrg.umcn.nl

BACKGROUND: Usher syndrome, a combination of retinitis pigmentosa (RP) and sensorineural hearing loss with or without vestibular dysfunction, displays a high degree of clinical and genetic heterogeneity. Three clinical subtypes can be distinguished, based on the age of onset and severity of the hearing impairment, and the presence or absence of vestibular abnormalities. Thus far, eight genes have been implicated in the syndrome, together comprising 347 protein-coding exons. METHODS: To improve DNA diagnostics for patients with Usher syndrome, we developed a genotyping microarray based on the arrayed primer extension (APEX) method. Allele-specific oligonucleotides corresponding to all 298 Usher syndrome-associated sequence variants known to date, 76 of which are novel, were arrayed. RESULTS: Approximately half of these variants were validated using original patient DNAs, which yielded an accuracy of >98%. The efficiency of the Usher genotyping microarray was tested using DNAs from 370 unrelated European and American patients with Usher syndrome. Sequence variants were identified in 64/140 (46%) patients with Usher syndrome type I, 45/189 (24%) patients with Usher syndrome type II, 6/21 (29%) patients with Usher syndrome type III and 6/20 (30%) patients with atypical Usher syndrome. The chip also identified two novel sequence variants, c.400C>T (p.R134X) in PCDH15 and c.1606T>C (p.C536S) in USH2A. CONCLUSION: The Usher genotyping microarray is a versatile and affordable screening tool for Usher syndrome. Its efficiency will improve with the addition of novel sequence variants with minimal extra costs, making it a very useful first-pass screening tool.

PMCID: PMC2598068 PMID: 16963483 [PubMed - indexed for MEDLINE]

Semicircular Canal Development

1. CHARGE Syndrome.

Lalani SR, Hefner MA, Belmont JW, Davenport SLH. In: Pagon RA, Bird TC, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle; 1993-. 2006 Oct 02.

Disease characteristics. CHARGE is a mnemonic that stands for coloboma, heart defects, choanal atresia, retarded growth and development, genital abnormalities, and ear anomalies. CHARGE syndrome is characterized by unilateral or bilateral coloboma of the iris, retina-choroid, and/or disc with or without microphthalmos (80%-90% of individuals); unilateral or bilateral choanal atresia or stenosis (50%-60%); cranial nerve dysfunction resulting in hyposmia or anosmia, unilateral or bilateral facial palsy (40%), impaired hearing and/or swallowing problems (70%-90%); abnormal outer ears, ossicular malformations, Mondini defect of the cochlea and absent or hypoplastic semicircular canals (>90%); cryptorchidism in males and hypogonadotrophic hypogonadism in both males and females; developmental delay; cardiovascular malformations (75%-85%); growth deficiency (70%-80%); orofacial clefts (15%-20%); and tracheoesophageal fistula (15%-20%). Neonates with CHARGE syndrome often have multiple life-threatening medical conditions. Feeding difficulties are a major cause of morbidity in all age groups. Diagnosis/testing. The diagnosis of CHARGE syndrome is based on clinical findings and temporal bone imaging. CHD7, encoding the chromodomain helicase DNA binding protein, is the only gene currently known to be associated with CHARGE syndrome. Sequence analysis of the CHD7 coding region detects mutations in approximately 60%-70% of individuals with CHARGE syndrome. Management. Treatment of manifestations: Neonates require immediate evaluation of the airway, feeding, heart, and hearing. Management involves: tracheostomy and surgical correction of choanal atresia as needed; a multidisciplinary approach to feeding therapy including specialists in speech-language pathology, occupational therapy, and nutrition and gastrostomy as needed; routine care for heart defects; and hearing aids and hearing habilitation as soon as hearing loss is documented. Psychological/school evaluations should be performed by a team that includes specialists in deafblindness when dual sensory loss is present. Prevention of secondary complications: special attention to potential airway problems associated with anesthesia. Surveillance: regular ophthalmologic and audiologic evaluations; testing for hypogonadotropic hypogonadism if puberty has not occurred by age 13-14 years. Genetic counseling. CHARGE syndrome, caused by mutation of CHD7, is inherited in an autosomal dominant manner. Most individuals diagnosed with CHARGE syndrome represent simplex cases (i.e., a single occurrence in a family). If a parent of the proband has CHARGE syndrome or has a CHD7 mutation, the risk to the sibs of inheriting the mutation is 50%. If neither parent is affected, the empiric risk to sibs of a proband is approximately 1%-2%, most likely attributable to germline mosaicism. Prenatal diagnosis for pregnancies at increased risk is possible if the disease-causing CHD7 mutation has been identified in an affected family member.

PMID: 20301296 [PubMed]

2. Dev Dyn. 2010 Apr;239(4):1102-12.

Long-term consequences of Sox9 depletion on inner ear development.

Park BY, Saint-Jeannet JP.

Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

The transcription factor Sox9 has been implicated in inner ear formation in several species. To investigate the long-term consequences of Sox9 depletion on inner ear development we analyzed the inner ear architecture of Sox9-depleted Xenopus tadpoles generated by injection of increasing amounts of Sox9 morpholino antisense oligonucleotides. We found that Sox9-depletion resulted in major defects in the development of vestibular structures, semicircular canals and utricle, while the ventrally located saccule was less severely affected in these embryos. Consistent with this phenotype, we observed a specific loss of the dorsal expression of Wnt3a expression in the otic vesicle of Sox9 morphants, associated with an increase in cell death and a reduction in cell proliferation in the region of the presumptive otic epithelium. We propose that, in addition to its early role in placode specification, Sox9 is also required for the maintenance of progenitors in the otic epithelium.

PMCID: PMC2847000 PMID: 20201105 [PubMed - in process]

3. PLoS One. 2010 Feb 1;5(2):e8981.

Vertebrate Lrig3-ErbB interactions occur in vitro but are unlikely to play a role in Lrig3-dependent inner ear morphogenesis.

Abraira VE, Satoh T, Fekete DM, Goodrich LV.

Department of Neurobiology and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts, United States of America.

BACKGROUND: The Lrig genes encode a family of transmembrane proteins that have been implicated in tumorigenesis, psoriasis, neural crest development, and complex tissue morphogenesis. Whether these diverse phenotypes reflect a single underlying cellular mechanism is not known. However, Lrig proteins contain evolutionarily conserved ectodomains harboring both leucine-rich repeats and immunoglobulin domains, suggesting an ability to bind to common partners. Previous studies revealed that Lrig1 binds to and inhibits members of the ErbB family of receptor tyrosine kinases by inducing receptor internalization and degradation. In addition, other receptor tyrosine kinase binding partners have been identified for both Lrig1 and Lrig3, leaving open the question of whether defective ErbB signaling is responsible for the observed mouse phenotypes. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report that Lrig3, like Lrig1, is able to interact with ErbB receptors in vitro. We examined the in vivo significance of these interactions in the inner ear, where Lrig3 controls semicircular canal formation by determining the timing and extent of Netrin1 expression in the otic vesicle epithelium. We find that ErbB2 and ErbB3 are present in the early otic epithelium, and that Lrig3 acts cell-autonomously here, as would be predicted if Lrig3 regulates ErbB2/B3 activity. However, inhibition of ErbB activation in the chick otic vesicle has no detectable effect on Netrin gene expression or canal morphogenesis. CONCLUSIONS/SIGNIFICANCE: Our results suggest that although both Lrig1 and Lrig3 can interact with ErbB receptors in vitro, modulation of Neuregulin signaling is unlikely to contribute to Lrig3-dependent processes of inner ear morphogenesis. These results highlight the similar binding properties of Lrig1 and Lrig3 and underscore the need to determine how these two family members bind to and regulate different receptors to affect diverse aspects of cell behavior in vivo.

PMCID: PMC2813878 PMID: 20126551 [PubMed - in process]

4. Dev Biol. 2010 Feb 1;338(1):38-49. Epub 2009 Nov 10.

Requirement for Lmo4 in the vestibular morphogenesis of mouse inner ear.

Deng M, Pan L, Xie X, Gan L.

University of Rochester Flaum Eye Institute, University of Rochester, Rochester, NY 14642, USA.

During development, compartmentalization of an early embryonic structure produces blocks of cells with distinct properties and developmental potentials. The auditory and vestibular components of vertebrate inner ears are derived from defined compartments within the otocyst during embryogenesis. The vestibular apparatus, including three semicircular canals, saccule, utricle, and their associated sensory organs, detects angular and linear acceleration of the head and relays the information through vestibular neurons to vestibular nuclei in the brainstem. How the early developmental events manifest vestibular structures at the molecular level is largely unknown. Here, we show that LMO4, a LIM-domain-only transcriptional regulator, is required for the formation of semicircular canals and their associated sensory cristae. Targeted disruption of Lmo4 resulted in the dysmorphogenesis of the vestibule and in the absence of three semicircular canals, anterior and posterior cristae. In Lmo4-null otocysts, canal outpouches failed to form and cell proliferation was reduced in the dorsolateral region. Expression analysis of the known otic markers showed that Lmo4 is essential for the normal expression of Bmp4, Fgf10, Msx1, Isl1, Gata3, and Dlx5 in the dorsolateral domain of the otocyst, whereas the initial compartmentalization of the otocyst remains unaffected. Our results demonstrate that Lmo4 controls the development of the dorsolateral otocyst into semicircular canals and cristae through two distinct mechanisms: regulating the expression of otic specific genes and stimulating the proliferation of the dorsolateral part of the otocyst.

PMCID: PMC2812651 PMID: 19913004 [PubMed - indexed for MEDLINE]

5. Theor Biol Med Model. 2009 Sep 1;6:19.

A model analysis of static stress in the vestibular membranes.

Pender DJ.

Department of Otolaryngology, Columbia University Medical Center New York, USA. djp2@columbia.edu

BACKGROUND: The scheme of the core vestibular membranes, consisting of serially connected utricle, ampulla and semicircular canal, first appeared hundreds of millions of years ago in primitive fish and has remained largely unchanged during the subsequent course of evolution. The labyrinths of higher organisms build on this core structure, with the addition of the phylogenetically newer membrane structures, namely, saccule, lagena and cochlea. An analysis of static stress in these core vestibular membranes may contribute to a better understanding of the role of stress in the evolution of derivative membrane structures over the long term as well as the short-term membrane distortions seen in Meniere's disease. METHODS: A model of these core vestibular membranes is proposed in order to analyze the distribution of stress in the walls of the component chambers. The model uses basic geometrical elements of hollow cylinders and spheres to emulate the actual structures. These model elements lend themselves to a mathematical analysis of static stress in their membranes. RESULTS: Hoop stress, akin to the stress in hoops used to reinforce barrel walls, is found to be the predominant stress in the model membranes. The level of hoop stress depends not only on pressure but as well on a geometric stress factor that incorporates membrane shape, thickness and curvature. This result implies that hoop stress may be unevenly distributed in the membranes of the several vestibular chambers due to variations in these dimensional parameters. These results provide a theoretical framework for appraising hoop stress levels in any vestibular labyrinth whose dimensions are known. CONCLUSION: Static hoop stress disparities are likely to exist in the vestibular membranes given their complex physical configurations. Such stress disparities may contribute to the development of membrane pathologies as seen in Meniere's Disease. They may also factor in the evolutionary development of other derivative membrane structures such as the saccule, the lagena, and the cochlea found in higher animals.

PMCID: PMC2745365 PMID: 19723316 [PubMed - indexed for MEDLINE]

6. Dev Biol. 2009 Apr 15;328(2):285-96. Epub 2009 Feb 2.

Catweasel mice: a novel role for Six1 in sensory patch development and a model for branchio-oto-renal syndrome.

Bosman EA, Quint E, Fuchs H, Hrabé de Angelis M, Steel KP.

The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.

Large-scale mouse mutagenesis initiatives have provided new mouse mutants that are useful models of human deafness and vestibular dysfunction. Catweasel is a novel N-ethyl-N-nitrosourea (ENU)-induced mutation. Heterozygous catweasel mutant mice exhibit mild headtossing associated with a posterior crista defect. We mapped the catweasel mutation to a critical region of 13 Mb on chromosome 12 containing the Six1, -4 and -6 genes. We identified a basepair substitution in exon 1 of the Six1 gene that changes a conserved glutamic acid (E) at position 121 to a glycine (G) in the Six1 homeodomain. Cwe/Cwe animals lack Preyer and righting reflexes, display severe headshaking and have severely truncated cochlea and semicircular canals. Cwe/Cwe animals had very few hair cells in the utricle, but their ampullae and cochlea were devoid of any hair cells. Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion. Lastly we show that Six1 genetically interacts with Jag1. We propose that the catweasel phenotype is due to a hypomorphic mutation in Six1 and that catweasel mice are a suitable model for branchio-oto-renal syndrome. In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

PMCID: PMC2682643 PMID: 19389353 [PubMed - indexed for MEDLINE]

7. BMC Neurosci. 2009 Mar 25;10:27.

Proteomic and functional analysis of NCS-1 binding proteins reveals novel signaling pathways required for inner ear development in zebrafish.

Petko JA, Kabbani N, Frey C, Woll M, Hickey K, Craig M, Canfield VA, Levenson R.

Department of Pharmacology, Penn State College of Medicine, 500 University Drive, Hershey PA 17033, USA. jac554@psu.edu

BACKGROUND: The semicircular canals, a subdivision of the vestibular system of the vertebrate inner ear, function as sensors of angular acceleration. Little is currently known, however, regarding the underlying molecular mechanisms that govern the development of this intricate structure. Zebrafish represent a particularly tractable model system for the study of inner ear development. This is because the ear can be easily visualized during early embryogenesis, and both forward and reverse genetic techniques are available that can be applied to the discovery of novel genes that contribute to proper ear development. We have previously shown that in zebrafish, the calcium sensing molecule neuronal calcium sensor-1 (NCS-1) is required for semicircular canal formation. The function of NCS-1 in regulating semicircular canal formation has not yet been elucidated. RESULTS: We initiated a multistep functional proteomic strategy to identify neuronal calcium sensor-1 (NCS-1) binding partners (NBPs) that contribute to inner ear development in zebrafish. By performing a Y2H screen in combination with literature and database searches, we identified 10 human NBPs. BLAST searches of the zebrafish EST and genomic databases allowed us to clone zebrafish orthologs of each of the human NBPs. By investigating the expression profiles of zebrafish NBP mRNAs, we identified seven that were expressed in the developing inner ear and overlapped with the ncs-1a expression profile. GST pulldown experiments confirmed that selected NBPs interacted with NCS-1, while morpholino-mediated knockdown experiments demonstrated an essential role for arf1, pi4kbeta, dan, and pink1 in semicircular canal formation. CONCLUSION: Based on their functional profiles, the hypothesis is presented that Ncs-1a/Pi4kbeta/Arf1 form a signaling pathway that regulates secretion of molecular components, including Dan and Bmp4, that are required for development of the vestibular apparatus. A second set of NBPs, consisting of Pink1, Hint2, and Slc25a25, are destined for localization in mitochondria. Our findings reveal a novel signalling pathway involved in development of the semicircular canal system, and suggest a previously unrecognized role for NCS-1 in mitochondrial function via its association with several mitochondrial proteins.

PMCID: PMC2679751 PMID: 19320994 [PubMed - indexed for MEDLINE]

8. Acta Otorrinolaringol Esp. 2009 Jan-Feb;60(1):49-53.

[Contribution of the vestibular evoked myogenic potentials to the study of the vestibular neuritis]

[Article in Spanish]

Lesmas Navarro MJ, Pérez Garrigues H, Morera Pérez C, Piqueras A.

Servicio de Otorrinolaringología, Hospital Universitario La Fe, Valencia, España.

INTRODUCTION: Until recently, the only tests available to provide information about vestibular function were caloric and kinetic tests, which only give us information about the external semicircular canal and the superior vestibular nerve. In recent years the development of vestibular evoked myogenic potentials has allowed us to assess the saccule and the inferior vestibular nerve. Our aim is, by studying the caloric test results as well as the vestibular evoked myogenic potentials in patients with Vestibular Neuritis, to determine whether they have involvement of the superior, inferior or both vestibular nerves. MATERIAL AND METHODS: Retrospective study of 9 patients with Vestibular Neuritis admitted to a tertiary care hospital. We studied them by means of anamnesis, otoneurological clinical examination, caloric test and vestibular evoked myogenic potentials. Their clinical progress after admission and any residual instability were also studied. RESULTS: Women were more affected (66.6 %) than males. The mean age for presentation of the disease was 53.8 +/- 14.0 years. Hospital stays lasted for 5.7 +/- 3.2 days. After their crises, they suffered from instability for 122 +/- 114 days. Four cases were diagnosed as Complete Vestibular Neuritis and five as Superior Vestibular Neuritis. P13 wave latency was normal in all cases. There were no differences between the groups in terms of the length of hospital stay nor residual instability. CONCLUSIONS: Nowadays, vestibular evoked myogenic potentials make it possible to advance further in the study of Vestibular Neuritis. Complete and superior vestibular neuritis are much more frequent than inferior vestibular neuritis. Clinical behaviour is similar in the sub-types found.

PMID: 19268130 [PubMed - indexed for MEDLINE]

9. J Exp Biol. 2009 Mar;212(Pt 5):639-47.

Plasma membrane calcium ATPase required for semicircular canal formation and otolith growth in the zebrafish inner ear.

Cruz S, Shiao JC, Liao BK, Huang CJ, Hwang PP.

Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan.

Fish otoliths consist of >90% calcium carbonate, the accretion of which depends on acellular endolymph. This study confirms the presence of plasma membrane calcium ATPase 1a isoform (Atp2b1a) in the auditory and vestibular system of a teleost fish. As shown by in situ hybridization, zebrafish atp2b1a is expressed mainly in larval otic placode and lateral-line neuromast as well as in the hair cells within the adult zebrafish inner ear chamber. Zebrafish atp2b1a knockdown by antisense morpholinos reduced the number of hair cells and produced malformation of semicircular canals and smaller otoliths. These defects coincide with unbalanced body orientation. The formation of smaller otoliths in atp2b1a morphants may stem from an impairment of calcium supply in the endolymph. However, otolith formation persists in most morphants, suggesting that other zebrafish Atp2b isoforms or paracellular pathways may also transport calcium into the endolymph. These results suggest that Atp2b1a plays an important role for normal development of the auditory and vestibular system as well as calcium transport in the inner ear of zebrafish.

PMID: 19218514 [PubMed - indexed for MEDLINE]

10. J Assoc Res Otolaryngol. 2009 Jun;10(2):161-72. Epub 2009 Feb 11.

A mouse model for degeneration of the spiral ligament.

Kada S, Nakagawa T, Ito J.

Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.

Previous studies have indicated the importance of the spiral ligament (SL) in the pathogenesis of sensorineural hearing loss. The aim of this study was to establish a mouse model for SL degeneration as the basis for the development of new strategies for SL regeneration. We injected 3-nitropropionic acid (3-NP), an inhibitor of succinate dehydrogenase, at various concentrations into the posterior semicircular canal of adult C57BL/6 mice. Saline-injected animals were used as controls. Auditory function was monitored by measurements of auditory brain stem responses (ABRs). On postoperative day 14, cochlear specimens were obtained after the measurement of the endocochlear potential (EP). Animals that were injected with 5 or 10 mM 3-NP showed a massive elevation of ABR thresholds along with extensive degeneration of the cochleae. Cochleae injected with 1 mM 3-NP exhibited selective degeneration of the SL fibrocytes but alterations in EP levels and ABR thresholds were not of sufficient magnitude to allow for testing functional recovery after therapeutic interventions. Animals injected with 3 mM 3-NP showed a reduction of around 50% in the EP along with a significant loss of SL fibrocytes, although degeneration of spiral ganglion neurons and hair cells was still present in certain regions. These findings indicate that cochleae injected with 3 mM 3-NP may be useful in investigations designed to test the feasibility of new therapeutic manipulations for functional SL regeneration.

PMCID: PMC2674195 PMID: 19212789 [PubMed - indexed for MEDLINE]

11. PLoS One. 2009;4(2):e4368. Epub 2009 Feb 3.

A late role for bmp2b in the morphogenesis of semicircular canal ducts in the zebrafish inner ear.

Hammond KL, Loynes HE, Mowbray C, Runke G, Hammerschmidt M, Mullins MC, Hildreth V, Chaudhry B, Whitfield TT.

MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom.

BACKGROUND: The Bone Morphogenetic Protein (BMP) genes bmp2 and bmp4 are expressed in highly conserved patterns in the developing vertebrate inner ear. It has, however, proved difficult to elucidate the function of BMPs during ear development as mutations in these genes cause early embryonic lethality. Previous studies using conditional approaches in mouse and chicken have shown that Bmp4 has a role in semicircular canal and crista development, but there is currently no direct evidence for the role of Bmp2 in the developing inner ear. METHODOLOGY/PRINCIPAL FINDINGS: We have used an RNA rescue strategy to test the role of bmp2b in the zebrafish inner ear directly. Injection of bmp2b or smad5 mRNA into homozygous mutant swirl (bmp2b(-/-)) embryos rescues the early patterning defects in these mutants and the fish survive to adulthood. As injected RNA will only last, at most, for the first few days of embryogenesis, all later development occurs in the absence of bmp2b function. Although rescued swirl adult fish are viable, they have balance defects suggestive of vestibular dysfunction. Analysis of the inner ears of these fish reveals a total absence of semicircular canal ducts, structures involved in the detection of angular motion. All other regions of the ear, including the ampullae and cristae, are present and appear normal. Early stages of otic development in rescued swirl embryos are also normal. CONCLUSIONS/SIGNIFICANCE: Our findings demonstrate a critical late role for bmp2b in the morphogenesis of semicircular canals in the zebrafish inner ear. This is the first demonstration of a developmental role for any gene during post-embryonic stages of otic morphogenesis in the zebrafish. Despite differences in the early stages of semicircular canal formation between zebrafish and amniotes, the role of Bmp2 in semicircular canal duct outgrowth is likely to be conserved between different vertebrate species.

PMCID: PMC2629815 PMID: 19190757 [PubMed - indexed for MEDLINE]

12. Development. 2008 Dec;135(24):4091-9. Epub 2008 Nov 12.

Cross-repressive interactions between Lrig3 and netrin 1 shape the architecture of the inner ear.

Abraira VE, Del Rio T, Tucker AF, Slonimsky J, Keirnes HL, Goodrich LV.

Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.

The sense of balance depends on the intricate architecture of the inner ear, which contains three semicircular canals used to detect motion of the head in space. Changes in the shape of even one canal cause drastic behavioral deficits, highlighting the need to understand the cellular and molecular events that ensure perfect formation of this precise structure. During development, the canals are sculpted from pouches that grow out of a simple ball of epithelium, the otic vesicle. A key event is the fusion of two opposing epithelial walls in the center of each pouch, thereby creating a hollow canal. During the course of a gene trap mutagenesis screen to find new genes required for canal morphogenesis, we discovered that the Ig superfamily protein Lrig3 is necessary for lateral canal development. We show that this phenotype is due to ectopic expression of the axon guidance molecule netrin 1 (Ntn1), which regulates basal lamina integrity in the fusion plate. Through a series of genetic experiments, we show that mutually antagonistic interactions between Lrig3 and Ntn1 create complementary expression domains that define the future shape of the lateral canal. Remarkably, removal of one copy of Ntn1 from Lrig3 mutants rescues both the circling behavior and the canal malformation. Thus, the Lrig3/Ntn1 feedback loop dictates when and where basement membrane breakdown occurs during canal development, revealing a new mechanism of complex tissue morphogenesis.

PMID: 19004851 [PubMed - indexed for MEDLINE]

13. Dev Dyn. 2009 Feb;238(2):358-66.

Fgf16(IRESCre) mice: a tool to inactivate genes expressed in inner ear cristae and spiral prominence epithelium.

Hatch EP, Urness LD, Mansour SL.

Department of Human Genetics, University of Utah, Salt Lake City, Utah, USA.

Fibroblast growth factors play important roles in inner ear development. Previous studies showed that mouse Fgf16 is expressed asymmetrically during the otic cup and vesicle stages of development, suggesting roles in regulating or responding to anteroposterior axial cues. Here, we studied otic Fgf16 expression throughout embryonic development and found transcripts in the developing cristae and in a few cells in the lateral wall of the cochlear duct. To determine the otic function of Fgf16 and to follow the fate of Fgf16-expressing cells, we generated an Fgf16(IRESCre) allele. We show that Fgf16 does not have a unique role in inner ear development and that the Fgf16 lineage is found throughout the three cristae, in portions of the semicircular canal ducts, and in the cochlear spiral prominence epithelial cells. This strain will be useful for gene ablations in these tissues.

PMCID: PMC2692467 PMID: 18773497 [PubMed - indexed for MEDLINE]

14. J Neurosci. 2008 Aug 6;28(32):8086-95.

Semicircular canal size determines the developmental onset of angular vestibuloocular reflexes in larval Xenopus.

Lambert FM, Beck JC, Baker R, Straka H.

Laboratoire de Neurobiologie des Réseaux Sensorimoteurs, Centre National de Recherche Scientifique, Unité Mixte de Recherche 7060, Université Paris Descartes, 75270 Paris Cedex 06, France.

Semicircular canals have been sensors of angular acceleration for 450 million years. This vertebrate adaptation enhances survival by implementing postural and visual stabilization during motion in a three-dimensional environment. We used an integrated neuroethological approach in larval Xenopus to demonstrate that semicircular canal dimensions, and not the function of other elements, determines the onset of angular acceleration detection. Before angular vestibuloocular function in either the vertical or horizontal planes, at stages 47 and 48, respectively, each individual component of the vestibuloocular system was shown to be operational: extraocular muscles could be activated, central neural pathways were complete, and canal hair cells were capable of evoking graded responses. For Xenopus, a minimum semicircular canal lumen radius of 60 microm was necessary to permit endolymph displacement sufficient for sensor function at peak accelerations of 400 degrees /s(2). An intra-animal comparison demonstrated that this size is reached in the vertical canals earlier in development than in the horizontal canals, corresponding to the earlier onset of vertical canal-activated ocular motor behavior. Because size constitutes a biophysical threshold for canal-evoked behavior in other vertebrates, such as zebrafish, we suggest that the semicircular canal lumen and canal circuit radius are limiting the onset of vestibular function in all small vertebrates. Given that the onset of gravitoinertial acceleration detection precedes angular acceleration detection by up to 10 d in Xenopus, these results question how the known precise spatial patterning of utricular and canal afferents in adults is achieved during development.

PMCID: PMC2647017 PMID: 18685033 [PubMed - indexed for MEDLINE]

15. Tohoku J Exp Med. 2008 Jul;215(3):207-17.

Epithelial-mesenchymal transition as a possible mechanism of semicircular canal morphogenesis in chick inner ear.

Kobayashi Y, Nakamura H, Funahashi J.

Department of Molecular Neurobiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.

Semicircular canals are sensory organs for balance, consisting of fluid-filled tubules that are arranged perpendicularly to each other in inner ear. The precise mechanism of the morphogenesis of this unique organ is still under investigation. Semicircular canals arise from the flattened pouch of epithelium. The centers of two apposing wall of the pouch approach each other and form a fusion plate. The clearing of the fusion plate makes a hole and leaves the remaining tissue as semicircular canals. Three mechanisms have been proposed for this clearing: programmed cell death, epithelial-mesenchymal transition, and retraction of the cells in the fusion plate to surrounding semicircular canals. Previous studies have revealed programmed cell death in the fusion plate, although other two hypotheses were not disproved. Here we examined the contribution of epithelial-mesenchymal transition and epithelial retraction to the morphogenesis of semicircular canals. We analyzed immunohistochemically the structural change in the epithelium of the developing fusion plate using molecular markers, basal lamina component laminin, cytoskeletal F-actin, and cellular junctional marker beta-catenin. Our observation revealed that fusion plate epithelium lost its apico-basal polarity and intermingled with facing fusion plate cells, associated with the disruption of basal lamina. Moreover, there were several cells with mesenchymal appearance adjacent to the torn basal lamina. We also found the merging of apposing basal laminae at the border between forming canal and breaking fusion plate. These observations suggest that the epithelial-mesenchymal transition, rather than the epithelial retraction, may be responsible for clearing fusion plate cells.

PMID: 18648181 [PubMed - indexed for MEDLINE]

16. PLoS Genet. 2008 Apr 11;4(4):e1000050.

Bmp4 is essential for the formation of the vestibular apparatus that detects angular head movements.

Chang W, Lin Z, Kulessa H, Hebert J, Hogan BL, Wu DK.

National Institute on Deafness and Other Communication Disorders, NIH, Rockville, Maryland, United States of America.

Angular head movements in vertebrates are detected by the three semicircular canals of the inner ear and their associated sensory tissues, the cristae. Bone morphogenetic protein 4 (Bmp4), a member of the Transforming growth factor family (TGF-beta), is conservatively expressed in the developing cristae in several species, including zebrafish, frog, chicken, and mouse. Using mouse models in which Bmp4 is conditionally deleted within the inner ear, as well as chicken models in which Bmp signaling is knocked down specifically in the cristae, we show that Bmp4 is essential for the formation of all three cristae and their associated canals. Our results indicate that Bmp4 does not mediate the formation of sensory hair and supporting cells within the cristae by directly regulating genes required for prosensory development in the inner ear such as Serrate1 (Jagged1 in mouse), Fgf10, and Sox2. Instead, Bmp4 most likely mediates crista formation by regulating Lmo4 and Msx1 in the sensory region and Gata3, p75Ngfr, and Lmo4 in the non-sensory region of the crista, the septum cruciatum. In the canals, Bmp2 and Dlx5 are regulated by Bmp4, either directly or indirectly. Mechanisms involved in the formation of sensory organs of the vertebrate inner ear are thought to be analogous to those regulating sensory bristle formation in Drosophila. Our results suggest that, in comparison to sensory bristles, crista formation within the inner ear requires an additional step of sensory and non-sensory fate specification.

PMCID: PMC2274953 PMID: 18404215 [PubMed - indexed for MEDLINE]

17. Dev Dyn. 2008 Apr;237(4):941-52.

The transmembrane inner ear (tmie) gene contributes to vestibular and lateral line development and function in the zebrafish (Danio rerio).

Shen YC, Jeyabalan AK, Wu KL, Hunker KL, Kohrman DC, Thompson DL, Liu D, Barald KF.

Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan 48109-2200, USA.

The inner ear is a complex organ containing sensory tissue, including hair cells, the development of which is not well understood. Our long-term goal is to discover genes critical for the correct formation and function of the inner ear and its sensory tissue. A novel gene, transmembrane inner ear (Tmie), was found to cause hearing-related disorders when defective in mice and humans. A homologous tmie gene in zebrafish was cloned and its expression characterized between 24 and 51 hours post-fertilization. Embryos injected with morpholinos (MO) directed against tmie exhibited circling swimming behavior (approximately 37%), phenocopying mice with Tmie mutations; semicircular canal formation was disrupted, hair cell numbers were reduced, and maturation of electrically active lateral line neuromasts was delayed. As in the mouse, tmie appears to be required for inner ear development and function in the zebrafish and for hair cell maturation in the vestibular and lateral line systems as well. (c) 2008 Wiley-Liss, Inc.

PMID: 18330929 [PubMed - indexed for MEDLINE]

18. Behav Neurosci. 2008 Feb;122(1):224-32.

Orbital spaceflight during pregnancy shapes function of mammalian vestibular system.

Ronca AE, Fritzsch B, Bruce LL, Alberts JR.

Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. aronca@wfubmc.edu

Pregnant rats were flown on the NASA Space Shuttle during the early developmental period of their fetuses' vestibular apparatus and onset of vestibular function. The authors report that prenatal spaceflight exposure shapes vestibular-mediated behavior and central morphology. Postflight testing revealed (a) delayed onset of body righting responses, (b) cardiac deceleration (bradycardia) to 70 degrees head-up roll, (c) decreased branching of gravistatic afferent axons, but (d) no change in branching of angular acceleration receptor projections with comparable synaptogenesis of the medial vestibular nucleus in flight relative to control fetuses. Kinematic analyses of the dams' on-orbit behavior suggest that, although the fetal otolith organs are unloaded in microgravity, the fetus' semicircular canals receive high levels of stimulation during longitudinal rotations of the mother's weightless body. Behaviorally derived stimulation from maternal movements may be a significant factor in studies of vestibular sensory development. Taken together, these studies provide evidence that gravity and angular acceleration shape prenatal organization and function within the mammalian vestibular system. Copyright (c) 2008 APA, all rights reserved.

PMCID: PMC2610337 PMID: 18298265 [PubMed - indexed for MEDLINE]

19. J Clin Endocrinol Metab. 2008 Mar;93(3):920-4. Epub 2007 Dec 18.

Endocrine and radiological studies in patients with molecularly confirmed CHARGE syndrome.

Asakura Y, Toyota Y, Muroya K, Kurosawa K, Fujita K, Aida N, Kawame H, Kosaki K, Adachi M.

Department of Endocrinology and Metabolism, 2-138-4 Mutsukawa Minamiku Yokohamashi, Kanagawa Children's Medical Center, Kanagawa 232-8555, Japan. yumi79@mvb.biglobe.ne.jp

CONTEXT: CHARGE syndrome is a complex of congenital malformations, and CHD7 has been reported as a major gene involved in the etiology. OBJECTIVE: We performed endocrine and radiological studies to determine whether endocrinological disorders such as hypogonadotropic hypogonadism, GH deficiency, or hypothyroidism are involved and also whether olfactory bulb hypoplasia and semicircular canal aplasia are major signs in patients with molecularly confirmed CHARGE syndrome. DESIGN: Clinical features, endocrinological assessments, and radiological abnormalities in eight children (five boys and three girls) whose molecular analyses were available were evaluated among 15 children clinically diagnosed with CHARGE syndrome at our institute. RESULTS: We identified heterozygous CHD7 mutations in all patients screened for mutations. Four boys had micropenis and/or cryptorchidism. One was diagnosed with GH deficiency, and the other was diagnosed with hypothyroidism. Computed tomography findings revealed aplasia of the semicircular canals. Magnetic resonance imaging studies of the olfactory bulb region revealed abnormal olfactory sulci and bulb development in all children. CONCLUSION: We suggest that hypogonadism, GH deficiency, and hypothyroidism could be possible endocrinological defects in patients with CHD7 mutations and that olfactory bulb hypoplasia as well as semicircular canal aplasia should be considered as a major sign for CHARGE syndrome and recommend a computed tomography scan of the temporal bone and magnetic resonance imaging study of the olfactory bulb region.

PMID: 18089695 [PubMed - indexed for MEDLINE]

20. J Acoust Soc Am. 2007 Aug;122(2):943-51.

A mechano-acoustic model of the effect of superior canal dehiscence on hearing in chinchilla.

Songer JE, Rosowski JJ.

Eaton-Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA. jocelyns@paradoxical.net

Superior canal dehiscence (SCD) is a pathological condition of the ear that can cause a conductive hearing loss. The effect of SCD (a hole in the bony wall of the superior semicircular canal) on chinchilla middle- and inner-ear mechanics is analyzed with a circuit model of the dehiscence. The model is used to predict the effect of dehiscence on auditory sensitivity and mechanics. These predictions are compared to previously published measurements of dehiscence related changes in chinchilla cochlear potential, middle-ear input admittance and stapes velocity. The comparisons show that the model predictions are both qualitatively and quantitatively similar to the physiological results for frequencies where physiologic data are available. The similarity supports the third-window hypothesis of the effect of superior canal dehiscence on auditory sensitivity and mechanics and provides the groundwork for the development of a model that predicts the effect of superior canal dehiscence syndrome on auditory sensitivity and mechanics in humans.

PMCID: PMC2254311 PMID: 17672643 [PubMed - indexed for MEDLINE]

21. Development. 2007 May;134(9):1713-22. Epub 2007 Mar 29.

Opposing gradients of Gli repressor and activators mediate Shh signaling along the dorsoventral axis of the inner ear.

Bok J, Dolson DK, Hill P, Rüther U, Epstein DJ, Wu DK.

National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA.

Organization of the vertebrate inner ear is mainly dependent on localized signals from surrounding tissues. Previous studies demonstrated that sonic hedgehog (Shh) secreted from the floor plate and notochord is required for specification of ventral (auditory) and dorsal (vestibular) inner ear structures, yet it was not clear how this signaling activity is propagated. To elucidate the molecular mechanisms by which Shh regulates inner ear development, we examined embryos with various combinations of mutant alleles for Shh, Gli2 and Gli3. Our study shows that Gli3 repressor (R) is required for patterning dorsal inner ear structures, whereas Gli activator (A) proteins are essential for ventral inner ear structures. A proper balance of Gli3R and Gli2/3A is required along the length of the dorsoventral axis of the inner ear to mediate graded levels of Shh signaling, emanating from ventral midline tissues. Formation of the ventral-most otic region, the distal cochlear duct, requires robust Gli2/3A function. By contrast, the formation of the proximal cochlear duct and saccule, which requires less Shh signaling, is achieved by antagonizing Gli3R. The dorsal vestibular region requires the least amount of Shh signaling in order to generate the correct dose of Gli3R required for the development of this otic region. Taken together, our data suggest that reciprocal gradients of GliA and GliR mediate the responses to Shh signaling along the dorsoventral axis of the inner ear.

PMID: 17395647 [PubMed - indexed for MEDLINE]

22. Hear Res. 2007 Mar;225(1-2):71-9. Epub 2006 Dec 28.

The role of bone morphogenetic protein 4 in inner ear development and function.

Blauwkamp MN, Beyer LA, Kabara L, Takemura K, Buck T, King WM, Dolan DF, Barald KF, Raphael Y, Koenig RJ.

Cellular and Molecular Biology Program, 2966 Taubman Medical Library, University of Michigan, Ann Arbor, MI 48109-0619, USA. mousman@med.umich.edu

Bone Morphogenetic Protein 4 (BMP4) is a member of the TGF-beta superfamily and is known to be important for the normal development of many tissues and organs, including the inner ear. Bmp4 homozygous null mice die as embryos, but Bmp4 heterozygous null (Bmp4(+/-)) mice are viable and some adults exhibit a circling phenotype, suggestive of an inner ear defect. To understand the role of BMP4 in inner ear development and function, we have begun to study C57BL/6 Bmp4(+/-) mice. Quantitative testing of the vestibulo-collic reflex, which helps maintain head stability, demonstrated that Bmp4(+/-) mice that exhibit circling behavior have a poor response in the yaw axis, consistent with semicircular canal dysfunction. Although the hair cells of the ampullae were grossly normal, the stereocilia were greatly reduced in number. Auditory brainstem responses showed that Bmp4(+/-) mice have elevated hearing thresholds and immunohistochemical staining demonstrated decreased numbers of neuronal processes in the organ of Corti. Thus Bmp4(+/-) mice have structural and functional deficits in the inner ear.

PMCID: PMC1868473 PMID: 17275231 [PubMed - indexed for MEDLINE]

23. J Cell Sci. 2006 Dec 15;119(Pt 24):5169-77.

Cadherin-2 participates in the morphogenesis of the zebrafish inner ear.

Babb-Clendenon S, Shen YC, Liu Q, Turner KE, Mills MS, Cook GW, Miller CA, Gattone VH 2nd, Barald KF, Marrs JA.

Department of Medicine, Indiana University Medical Center, 950 West Walnut Street, Indianapolis, IN 46202, USA.

Molecular mechanisms that control inner ear morphogenesis from the placode to the three-dimensional functional organ are not well understood. We hypothesize that cell-cell adhesion, mediated by cadherin molecules, contributes significantly to various stages of inner ear formation. Cadherin-2 (Cdh2) function during otic vesicle morphogenesis was investigated by examining morpholino antisense oligonucleotide knockdown and glass onion (glo) (Cdh2 mutant) zebrafish embryos. Placode formation, vesicle cavitation and specification occurred normally, but morphogenesis of the otic vesicle was affected by Cdh2 deficiency: semicircular canals were reduced or absent. Phalloidin staining of the hair cell stereocillia demonstrated that cadherin-2 (cdh2) loss-of-function did not affect hair cell number, but acetylated tubulin labeling showed that hair cell kinocilia were shorter and irregularly shaped. Statoacoustic ganglion size was significantly reduced, which suggested that neuron differentiation or maturation was affected. Furthermore, cdh2 loss-of-function did not cause a general developmental delay, since differentiation of other tissues, including eye, proceeded normally. These findings demonstrate that Cdh2 selectively affects epithelial morphogenetic cell movements, particularly semicircular canal formation, during normal ear mophogenesis.

PMID: 17158919 [PubMed - indexed for MEDLINE]

24. Proc Natl Acad Sci U S A. 2006 Jun 13;103(24):9069-74. Epub 2006 Jun 5.

Mutation of the atrophin2 gene in the zebrafish disrupts signaling by fibroblast growth factor during development of the inner ear.

Asai Y, Chan DK, Starr CJ, Kappler JA, Kollmar R, Hudspeth AJ.

Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399, USA.

The development of the vertebrate inner ear depends on the precise expression of fibroblast growth factors. In a mutagenesis screen for zebrafish with abnormalities of inner-ear development and behavior, we isolated a mutant line, ru622, whose phenotypic characteristics resembled those of null mutants for the gene encoding fibroblast growth factor 8 (Fgf8): an inconsistent startle response, circular swimming, fused otoliths, and abnormal semicircular canals. Positional cloning disclosed that the mutant gene encodes the transcriptional corepressor Atrophin2. Both the Fgf8 protein and zebrafish "similar expression to fgf genes" protein (Sef), an antagonist of fibroblast growth factors induced by Fgf8 itself, were found to be overexpressed in ru622 mutants. We therefore hypothesized that an excess of Sef eliminates Fgf8 signals and produces an fgf8 null phenotype in ru622 mutants. In support of this idea, we could rescue larvae whose atrophin2 expression had been diminished with morpholinos by reducing the expression of Sef as well. We propose that Atrophin2 plays a role in the feedback regulation of Fgf8 signaling. When mutation of the atrophin2 gene results in the overexpression of both Fgf8 and Sef, the excessive Sef inhibits Fgf8 signaling. The resultant imbalance of Fgf8 and Sef signals then underlies the abnormal aural development observed in ru622.

PMCID: PMC1474007 PMID: 16754885 [PubMed - indexed for MEDLINE]

25. Anat Rec A Discov Mol Cell Evol Biol. 2006 Apr;288(4):482-9.

Evolutionary changes in the cochlea and labyrinth: Solving the problem of sound transmission to the balance organs of the inner ear.

Carey J, Amin N.

Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA. jcarey@jhmi.edu

This review article examines the evolutionary adaptations in the vertebrate inner ear that allow selective activation of auditory or vestibular hair cells, although both are housed in the same bony capsule. The problem of separating acoustic stimuli from the vestibular end organs in the inner ear has recently reemerged with the recognition of clinical conditions such as superior canal dehiscence syndrome and enlarged vestibular aqueduct syndrome. In these syndromes, anatomical defects in the otic capsule alter the functional separation of auditory and vestibular stimuli and lead to pathological activation of vestibular reflexes in response to sound. This review demonstrates that while the pars superior of the labyrinth (utricle and semicircular canals) has remained fairly constant throughout evolution, the pars inferior (saccule and other otolith, macular, and auditory end organs) has seen considerable change as many adaptations were made for the development of auditory function. Among these were a relatively rigid membranous labyrinth wall, a variably rigid otic capsule, immersion of the membranous labyrinth in perilymph, a perilymphatic duct to channel acoustic pressure changes away from the vestibular organs, and different operating frequencies for vestibular versus auditory epithelia. Even in normal human ears, acoustic sensitivity of the labyrinth to loud clicks or tones is retained enough to be measured in a standard clinical test, the vestibular-evoked myogenic potential test. Copyright 2006 Wiley-Liss, Inc.

PMID: 16552774 [PubMed - indexed for MEDLINE]

26. Development. 2006 Apr;133(7):1347-57. Epub 2006 Mar 1.

The developing lamprey ear closely resembles the zebrafish otic vesicle: otx1 expression can account for all major patterning differences.

Hammond KL, Whitfield TT.

Department of Biomedical Science, Centre for Developmental and Biomedical Genetics, University of Sheffield, Sheffield S10 2TN, UK.

The inner ear of adult agnathan vertebrates is relatively symmetric about the anteroposterior axis, with only two semicircular canals and a single sensory macula. This contrasts with the highly asymmetric gnathostome arrangement of three canals and several separate maculae. Symmetric ears can be obtained experimentally in gnathostomes in several ways, including by manipulation of zebrafish Hedgehog signalling, and it has been suggested that these phenotypes might represent an atavistic condition. We have found, however, that the symmetry of the adult lamprey inner ear is not reflected in its early development; the lamprey otic vesicle is highly asymmetric about the anteroposterior axis, both morphologically and molecularly, and bears a striking resemblance to the zebrafish otic vesicle. The single sensory macula originates as two foci of hair cells, and later shows regions of homology to the zebrafish utricular and saccular maculae. It is likely, therefore, that the last common ancestor of lampreys and gnathostomes already had well-defined otic anteroposterior asymmetries. Both lamprey and zebrafish otic vesicles express a target of Hedgehog signalling, patched, indicating that both are responsive to Hedgehog signalling. One significant distinction between agnathans and gnathostomes, however, is the acquisition of otic Otx1 expression in the gnathostome lineage. We show that Otx1 knockdown in zebrafish, as in Otx1(-/-) mice, gives rise to lamprey-like inner ears. The role of Otx1 in the gnathostome ear is therefore highly conserved; otic Otx1 expression is likely to account not only for the gain of a third semicircular canal and crista in gnathostomes, but also for the separation of the zones of the single macula into distinct regions.

PMID: 16510503 [PubMed - indexed for MEDLINE]

27. Radiographics. 2006 Jan-Feb;26(1):115-24.

Middle and inner ear: improved depiction with multiplanar reconstruction of volumetric CT data.

Lane JI, Lindell EP, Witte RJ, DeLone DR, Driscoll CL.

Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55902, USA. lane.john@mayo.edu

Many anatomic structures of the middle and inner ear are not optimally depicted at computed tomography (CT) with image reconstruction in the standard axial and coronal planes. Recent advances in multidetector CT, including the development of scanners with 32 detector rows, allow the acquisition of isotropic voxels that can be reconstructed in any plane of section. This technique gives radiologists the opportunity to visualize the anatomic structures of the middle and inner ear (the ossicular chain, stapedial footplate-oval window complex, round window, cochlea, vestibular aqueduct, and bones of the superior semicircular canal and facial nerve canal) in greater detail and may help increase the accuracy of CT for the diagnosis of diseases of the middle and inner ear. (c) RSNA, 2006.

PMID: 16418247 [PubMed - indexed for MEDLINE]

28. Hum Mol Genet. 2005 Nov 15;14(22):3463-76. Epub 2005 Oct 5.

Multiple mutations in mouse Chd7 provide models for CHARGE syndrome.

Bosman EA, Penn AC, Ambrose JC, Kettleborough R, Stemple DL, Steel KP.

Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK.

Mouse ENU mutagenesis programmes have yielded a series of independent mutations on proximal chromosome 4 leading to dominant head-bobbing and circling behaviour due to truncations of the lateral semicircular canal of the inner ear. Here, we report the identification of mutations in the Chd7 gene in nine of these mutant alleles including six nonsense and three splice site mutations. The human CHD7 gene is known to be involved in CHARGE syndrome, which also shows inner ear malformations and a variety of other features with varying penetrance and appears to be due to frequent de novo mutation. We found widespread expression of Chd7 in early development of the mouse in organs affected in CHARGE syndrome including eye, olfactory epithelium, inner ear and vascular system. Closer inspection of heterozygous mutant mice revealed a range of defects with reduced penetrance, such as cleft palate, choanal atresia, septal defects of the heart, haemorrhages, prenatal death, vulva and clitoral defects and keratoconjunctivitis sicca. Many of these defects mimic the features of CHARGE syndrome. There were no obvious features of the gene that might make it more mutable than other genes. We conclude that the large number of mouse mutants and human de novo mutations may be due to the combination of the Chd7 gene being a large target and the fact that many heterozygous carriers of the mutations are viable individuals with a readily detectable phenotype.

PMID: 16207732 [PubMed - indexed for MEDLINE]

29. J Med Genet. 2006 Apr;43(4):306-14. Epub 2005 Sep 9.

CHARGE syndrome: the phenotypic spectrum of mutations in the CHD7 gene.

Jongmans MC, Admiraal RJ, van der Donk KP, Vissers LE, Baas AF, Kapusta L, van Hagen JM, Donnai D, de Ravel TJ, Veltman JA, Geurts van Kessel A, De Vries BB, Brunner HG, Hoefsloot LH, van Ravenswaaij CM.

Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands.

BACKGROUND: CHARGE syndrome is a non-random clustering of congenital anomalies including coloboma, heart defects, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies, and deafness. A consistent feature in CHARGE syndrome is semicircular canal hypoplasia resulting in vestibular areflexia. Other commonly associated congenital anomalies are facial nerve palsy, cleft lip/palate, and tracheo-oesophageal fistula. Specific behavioural problems, including autistic-like behaviour, have been described. The CHD7 gene on chromosome 8q12.1 was recently discovered as a major gene involved in the aetiology of this syndrome. METHODS: The coding regions of CHD7 were screened for mutations in 107 index patients with clinical features suggestive of CHARGE syndrome. Clinical data of the mutation positive patients were sampled to study the phenotypic spectrum of mutations in the CHD7 gene. RESULTS: Mutations were identified in 69 patients. Here we describe the clinical features of 47 of these patients, including two sib pairs. Most mutations were unique and were scattered throughout the gene. All patients but one fulfilled the current diagnostic criteria for CHARGE syndrome. No genotype-phenotype correlations were apparent in this cohort, which is best demonstrated by the differences in clinical presentation in sib pairs with identical mutations. Somatic mosaicism was detected in the unaffected mother of a sib pair, supporting the existence of germline mosaicism. CONCLUSIONS: CHD7 mutations account for the majority of the cases with CHARGE syndrome, with a broad clinical variability and without an obvious genotype-phenotype correlation. In one case evidence for germline mosaicism was provided.

PMCID: PMC2563221 PMID: 16155193 [PubMed - indexed for MEDLINE]

30. Development. 2005 May;132(10):2309-18. Epub 2005 Apr 13.

Gbx2 is required for the morphogenesis of the mouse inner ear: a downstream candidate of hindbrain signaling.

Lin Z, Cantos R, Patente M, Wu DK.

Laboratory of Molecular Biology, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20850, USA.

Gbx2 is a homeobox-containing transcription factor that is related to unplugged in Drosophila. In mice, Gbx2 and Otx2 negatively regulate each other to establish the mid-hindbrain boundary in the neural tube. Here, we show that Gbx2 is required for the development of the mouse inner ear. Absence of the endolymphatic duct and swelling of the membranous labyrinth are common features in Gbx2-/- inner ears. More severe mutant phenotypes include absence of the anterior and posterior semicircular canals, and a malformed saccule and cochlear duct. However, formation of the lateral semicircular canal and its ampulla is usually unaffected. These inner ear phenotypes are remarkably similar to those reported in kreisler mice, which have inner ear defects attributed to defects in the hindbrain. Based on gene expression analyses, we propose that activation of Gbx2 expression within the inner ear is an important pathway whereby signals from the hindbrain regulate inner ear development. In addition, our results suggest that Gbx2 normally promotes dorsal fates such as the endolymphatic duct and semicircular canals by positively regulating genes such as Wnt2b and Dlx5. However, Gbx2 promotes ventral fates such as the saccule and cochlear duct, possibly by restricting Otx2 expression.

PMID: 15829521 [PubMed - indexed for MEDLINE]

31. Dev Dyn. 2005 May;233(1):177-87.

Identification of cis-element regulating expression of the mouse Fgf10 gene during inner ear development.

Ohuchi H, Yasue A, Ono K, Sasaoka S, Tomonari S, Takagi A, Itakura M, Moriyama K, Noji S, Nohno T.

Department of Biological Science and Technology, Faculty of Engineering, University of Tokushima, 2-1 Minami-Jyosanjima-cho, Tokushima City 770-8506, Japan. hohuchi@bio.tokushima-u.ac.jp

Fibroblast growth factor (FGF) signaling is crucial for the induction and growth of the ear, a sensory organ that involves intimate tissue interactions. Here, we report the abnormality of Fgf10 null ear and the identification of a cis-regulatory element directing otic expression of Fgf10. In Fgf10 null inner ears, we found that the initial development of semicircular, vestibular, and cochlear divisions is roughly normal, after which there are abnormalities of semicircular canal/cristae and vestibular development. The mutant semicircular disks remain without canal formation by the perinatal stage. To elucidate regulation of the Fgf10 expression during inner ear development, we isolated a 6.6-kb fragment of its 5'-upstream region and examined its transcriptional activity with transgenic mice, using a lacZ-reporter system. From comparison of the mouse sequences of the 6.6-kb fragment with corresponding sequences of the human and chicken Fgf10, we identified a 0.4-kb enhancer sequence that drives Fgf10 expression in the developing inner ear. The enhancer sequences have motifs for many homeodomain-containing proteins (e.g., Prx, Hox, Nkx), in addition to POU-domain factors (e.g., Brn3), zinc-finger transcription factors (e.g., GATA-binding factors), TCF/LEF-1, and a SMAD-interacting protein. Thus, FGF10 signaling is dispensable for specification of otic compartment identity but is required for hollowing the semicircular disk. Furthermore, the analysis of a putative inner ear enhancer of Fgf10 has disclosed a complicated regulation of Fgf10 during inner ear development by numerous transcription factors and signaling pathways. Copyright 2005 Wiley-Liss, Inc.

PMID: 15765517 [PubMed - indexed for MEDLINE]

32. Acta Otorrinolaringol Esp. 2005 Jan;56(1):6-11.

[Superior semicircular canal dehiscence syndrome. Embryological and surgical consideration]

[Article in Spanish]

Crovetto de la Torre MA, Whyte Orozco J, Cisneros Gimeno AI, Basurko Aboitz JM, Oleaga Zufiria L, Sarrat Torreguitart R.

Servicios de Otorrinolaringología y Radiología, Hospital de Basurto, Bilbao. macdl@camaranet.com

OBJECTIVE: Presenting the first case of superior semicircular canal dehiscence syndrome in the Spanish literature and to establish, using embryological studies, the period in wich superior semicircular canal dehiscence originates. MATERIAL AND METHODS: 52 embryos and foetuses, from 6 mm to foetal maturity, were studied. The case of a patient suffering from superior semicircular canal dehiscence syndrome is presented. RESULTS: The superior semicircular canal and the intracranial space are communicated through bony lacunae, in the period between the 24th and 28th week of foetal development, but this communication is discontinued in the 30th week. Permeability of these lacunae, later in life, could result in the development of superior semicircular canal dehiscence syndrome. The clinical results of the surgical repair of this abnormal communication, in this particular case, using a middle fossa approach and a transmastoid approach is presented. CONCLUSIONS: Superior Semicircular Canal Dehiscence Syndrome could be due to an abnormality in foetal development and its genesis, therefore, could be prenatal. Surgical repair via transmastoid approach is a reasonable alternative treatment to the middle fossa approach.

PMID: 15747717 [PubMed - indexed for MEDLINE]

33. Arch Otolaryngol Head Neck Surg. 2005 Jan;131(1):41-5.

Abnormal mesenchymal differentiation in the superior semicircular canal of brn4/pou3f4 knockout mice.

Sobol SE, Teng X, Crenshaw EB 3rd.

Division of Pediatric Otolaryngology and Mammalian Neurogenetics Group, The Center for Childhood Communication, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.

OBJECTIVE: To examine the developmental time course of the mutant phenotype and cellular mechanisms that result in malformations of the superior semicircular canal (SSCC) in Brn4 knockout mice. Mutations in the Brn4/Pou3f4 gene result in characteristic inner ear abnormalities in mutant mouse pedigrees, and the findings in these mice are similar to those in human X-linked deafness type III. DESIGN: Mutant and control mice were killed at various neonatal time points to assess the development of the SSCC. Measurements of SSCC diameter were made on paint-perfused specimens at postnatal day (P) 0, P7, P10, and P14. Histologic evaluation of the SSCC was made on hematoxylin-eosin-stained sections at P10. RESULTS: A dysmorphic constriction of the superior arc of the SSCC in Brn4 knockout mice was initially detectable at P14. Interestingly, the mutant SSCC is indistinguishable from control mice at earlier neonatal time points. In mutant neonates, there is persistence of immature woven bone with high cellularity surrounding the perilymphatic space of the SSCC. These findings are not present in control animal specimens, which demonstrate appropriate lamellar bony architecture. CONCLUSIONS: In Brn4 knockout mice, constriction of the SSCC with narrowing of the bony labyrinth develops in the postnatal period at approximately P14. The persistence of immature bone in affected mice indicates that signaling abnormalities disrupt normal mesenchymal differentiation in the SSCC.

PMID: 15655183 [PubMed - indexed for MEDLINE]

34. Arterioscler Thromb Vasc Biol. 2005 Feb;25(2):315-20. Epub 2004 Dec 2.

Prostaglandin E synthases in zebrafish.

Pini B, Grosser T, Lawson JA, Price TS, Pack MA, FitzGerald GA.

Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia 19104-6084, USA.

OBJECTIVE: Prostaglandin E synthases (PGESs) are being explored as antiinflammatory drug targets as alternatives to cyclooxygenase (COX)-2. Located downstream of the cyclooxygenases, PGESs catalyze PGE(2) formation, and deletion of microsomal (m)-PGES-1 abrogates inflammation. We sought to characterize the developmental expression of COX and PGES in zebrafish. METHODS AND RESULTS: We cloned zebrafish cytosolic (c) and m-PGES orthologs and mapped them to syntenic regions of chromosomes 23 and 5. cPGES was widely expressed during development and was coordinately regulated with zCOX-1 in the inner ear, the pronephros, and intestine. COX-2 and mPGES-1 exhibited restricted expression, dominantly in the vasculature of the aortic arch. However, the enzymes were anatomically segregated within the vessel wall. Experiments with antisense morpholinos and with nonsteroidal antiinflammatory drugs suggest that these genes may not be critical for development. CONCLUSIONS: mPGES-1 is developmentally coregulated with COX-2 in vasculature. Given the high fecundidity and translucency of the zebrafish, this model may afford a high throughput system for characterization of novel PGES inhibitors. Microsomal prostaglandin E synthase (mPGES)-1, located downstream of COX-2, may represent a novel antiinflammatory drug target. Zebrafish cytosolic (c) PGES-1 and COX-1 were coordinately expressed; mPGES-1 and COX-2 were expressed particularly in the vasculature. Zebrafish may afford a high throughput system for detection of novel PGES inhibitors.

PMID: 15576635 [PubMed - indexed for MEDLINE]

35. J Biol Chem. 2005 Feb 4;280(5):3613-20. Epub 2004 Nov 17.

Insulin-like growth factor-binding protein-3 plays an important role in regulating pharyngeal skeleton and inner ear formation and differentiation.

Li Y, Xiang J, Duan C.

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.

Insulin-like growth factor-binding protein (IGFBP)-3 is the major insulin-like growth factor (IGF) carrier protein in the bloodstream. IGFBP-3 prolongs the half-life of circulating IGFs and prevents their potential hypoglycemic effect. IGFBP-3 is also expressed in many peripheral tissues in fetal and adult stages. In vitro, IGFBP-3 can inhibit or potentiate IGF actions and even possesses IGF-independent activities, suggesting that local IGFBP-3 may also have paracrine/autocrine function(s). The in vivo function of IGFBP-3, however, is unclear. In this study, we elucidate the developmental role of IGFBP-3 using the zebrafish model. IGFBP-3 mRNA expression is first detected in the migrating cranial neural crest cells and subsequently in pharyngeal arches in zebrafish embryos. IGFBP-3 mRNA is also persistently expressed in the developing inner ears. To determine the role of IGFBP-3 in these tissues, we ablated the IGFBP-3 gene product using morpholino-modified antisense oligonucleotides (MOs). The IGFBP-3 knocked down embryos had delayed pharyngeal skeleton morphogenesis and greatly reduced pharyngeal cartilage differentiation. Knockdown of IGFBP-3 also significantly decreased inner ear size and disrupted hair cell differentiation and semicircular canal formation. Furthermore, reintroduction of a MO-resistant form of IGFBP-3 "rescued" the MO-induced defects. These findings suggest that IGFBP-3 plays an important role in regulating pharyngeal cartilage and inner ear development and growth in zebrafish.

PMID: 15550380 [PubMed - indexed for MEDLINE]

36. Dev Dyn. 2004 Dec;231(4):766-74.

OC29 is preferentially expressed in the presumptive sensory organ region of the otocyst.

Nishida AT, Kobuke K, Kojima K, Ito J, Honjo T, Tashiro K.

Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Kyoto, Japan.

The mammalian inner ear derives from the otocyst. Molecular mechanisms underlying inner ear development are largely unknown. We have isolated a secreted molecule, OC29, from a rat otocyst cDNA library by the signal sequence trap method. OC29 was revealed to be a rat homologue of human WFIKKN. OC29 is preferentially expressed in the developing inner ear and the dorsal neural tube. In the inner ear, the expression of OC29 is first detectable at embryonic day 11.5 (E11.5), broadly in the dorsolateral region of the otocyst, which gives rise to the vestibular organ. At E12.5, the expression of OC29 becomes restricted to the presumptive sensory region, mainly to the BMP4-positive presumptive cristae, and expression becomes reduced at later stages. These results suggest that OC29 may have a role in the early development of the inner ear sensory organ, particularly in the formation of the cristae of the semicircular canals. Copyright (c) 2004 Wiley-Liss, Inc.

PMID: 15497143 [PubMed - indexed for MEDLINE]

37. Development. 2004 Sep;131(17):4201-11. Epub 2004 Jul 27.

The development of semicircular canals in the inner ear: role of FGFs in sensory cristae.

Chang W, Brigande JV, Fekete DM, Wu DK.

National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA.

In the vertebrate inner ear, the ability to detect angular head movements lies in the three semicircular canals and their sensory tissues, the cristae. The molecular mechanisms underlying the formation of the three canals are largely unknown. Malformations of this vestibular apparatus found in zebrafish and mice usually involve both canals and cristae. Although there are examples of mutants with only defective canals, few mutants have normal canals without some prior sensory tissue specification, suggesting that the sensory tissues, cristae, might induce the formation of their non-sensory components, the semicircular canals. We fate-mapped the vertical canal pouch in chicken that gives rise to the anterior and posterior canals, using a fluorescent, lipophilic dye (DiI), and identified a canal genesis zone adjacent to each prospective crista that corresponds to the Bone morphogenetic protein 2 (Bmp2)-positive domain in the canal pouch. Using retroviruses or beads to increase Fibroblast Growth Factors (FGFs) for gain-of-function and beads soaked with the FGF inhibitor SU5402 for loss-of-function experiments, we show that FGFs in the crista promote canal development by upregulating Bmp2. We postulate that FGFs in the cristae induce a canal genesis zone by inducing/upregulating Bmp2 expression. Ectopic FGF treatments convert some of the cells in the canal pouch from the prospective common crus to a canal-like fate. Thus, we provide the first molecular evidence whereby sensory organs direct the development of the associated non-sensory components, the semicircular canals, in vertebrate inner ears.

PMID: 15280215 [PubMed - indexed for MEDLINE]

38. J Anat. 2004 Feb;204(2):71-92.

Prenatal growth and development of the modern human labyrinth.

Jeffery N, Spoor F.

Department of Human Anatomy and Cell Biology, University of Liverpool, UK. njeffery@liverpool.ac.uk

The modern human bony labyrinth is morphologically distinct from that of all other primates, showing derived features linked with vestibular function and the overall shape of the cranial base. However, little is known of how this unique morphology emerges prenatally. This study examines in detail the developing fetal human labyrinth, both to document this basic aspect of cranial biology, and more specifically, to gain insight into the ontogenetic basis of its phylogenetically derived morphology. Forty-one post-mortem human fetuses, ranging from 9 to 29 weeks gestation, were investigated with high-resolution magnetic resonance imaging. Quantitative analyses of the labyrinthine morphology revealed a number of interesting age-related trends. In addition, our findings show that: (1) the prenatal labyrinth attains an adult equivalent size between 17 and 19 weeks gestation; (2) within the period investigated, shape changes to all or most of the labyrinth cease after the 17-19-week size maturation point or after the otic capsule ossifies; (3) fetal cochlea development correlates with the surrounding petrosal morphology, but not with the midline basicranium; (4) gestational age-related rotations of the ampullae and cochlea relative to the lateral canal, and posterior canal torsion are similar to documented phylogenetic trends whereas other trends remain distinct. Findings are discussed in terms of the ontogenetic processes and mechanisms that most likely led, in part, to the emergence of the phylogenetically derived adult modern human labyrinth.

PMCID: PMC1571245 PMID: 15032915 [PubMed - indexed for MEDLINE]

39. Dev Dyn. 2004 Feb;229(2):219-30.

DAN directs endolymphatic sac and duct outgrowth in the avian inner ear.

Gerlach-Bank LM, Cleveland AR, Barald KF.

Department of Cell and Developmental Biology, Cell and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan 48109, USA.

Bone morphogenetic proteins (BMPs) are expressed in the developing vertebrate inner ear and participate in inner ear axial patterning and the development of its sensory epithelium. BMP antagonists, such as noggin, chordin, gremlin, cerberus, and DAN (differential screening-selected gene aberrative in neuroblastoma) inhibit BMP activity and establish morphogenetic gradients during the patterning of many developing tissues and organs. In this study, the role of the BMP antagonist DAN in inner ear development was investigated. DAN-expressing cell pellets were implanted into the otocyst and the periotic mesenchyme to determine the effects of exogenous DAN on otic development. Similar to the effects on the inner ear seen after exposure of otocysts to the BMP4 antagonist noggin, semicircular canals were truncated or eliminated based upon the site of pellet implantation. Unique to the DAN implantations, however, were effects on the developing endolymphatic duct and sac. In DAN-treated inner ears, endolymphatic ducts and sacs were merged with the crus or grew into the superior semicircular canal. Both the canal and endolymphatic duct and sac effects were rescued by joint implantation of BMP4-expressing cells. Electroporation of DAN antisense morpholinos into the epithelium of stage 15-17 otocysts, blocking DAN protein synthesis, resulted in enlarged endolymphatic ducts and sacs as well as smaller semicircular canals in some cases. Taken together, these data suggest a role for DAN both in helping to regulate BMP activity spatially and temporally and in patterning and partitioning of the medial otic tissue between the endolymphatic duct/sac and medially derived inner ear structures. Copyright 2003 Wiley-Liss, Inc.

PMID: 14745948 [PubMed - indexed for MEDLINE]

40. Development. 2004 Feb;131(4):943-51. Epub 2004 Jan 21.

The deafness gene dfna5 is crucial for ugdh expression and HA production in the developing ear in zebrafish.

Busch-Nentwich E, Söllner C, Roehl H, Nicolson T.

Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35, 72076 Tübingen, Germany.

Over 30 genes responsible for human hereditary hearing loss have been identified during the last 10 years. The proteins encoded by these genes play roles in a diverse set of cellular functions ranging from transcriptional regulation to K(+) recycling. In a few cases, the genes are novel and do not give much insight into the cellular or molecular cause for the hearing loss. Among these poorly understood deafness genes is DFNA5. How the truncation of the encoded protein DFNA5 leads to an autosomal dominant form of hearing loss is not clear. In order to understand the biological role of Dfna5, we took a reversegenetic approach in zebrafish. Here we show that morpholino antisense nucleotide knock-down of dfna5 function in zebrafish leads to disorganization of the developing semicircular canals and reduction of pharyngeal cartilage. This phenotype closely resembles previously isolated zebrafish craniofacial mutants including the mutant jekyll. jekyll encodes Ugdh [uridine 5'-diphosphate (UDP)-glucose dehydrogenase], an enzyme that is crucial for production of the extracellular matrix component hyaluronic acid (HA). In dfna5 morphants, expression of ugdh is absent in the developing ear and pharyngeal arches, and HA levels are strongly reduced in the outgrowing protrusions of the developing semicircular canals. Previous studies suggest that HA is essential for differentiating cartilage and directed outgrowth of the epithelial protrusions in the developing ear. We hypothesize that the reduction of HA production leads to uncoordinated outgrowth of the canal columns and impaired facial cartilage differentiation.

PMID: 14736743 [PubMed - indexed for MEDLINE]

41. Dev Dyn. 2003 Nov;228(3):386-92.

Differential expression of Na,K-ATPase alpha and beta subunit genes in the developing zebrafish inner ear.

Blasiole B, Degrave A, Canfield V, Boehmler W, Thisse C, Thisse B, Mohideen MA, Levenson R.

Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania 17033, USA.

We have used whole-mount in situ hybridization to analyze Na,K-ATPase alpha and beta subunit gene expression in the developing zebrafish ear. Four alpha1-like (alpha1a.1, alpha1a.2, alpha1a.4, and alpha1a.5) and two beta (beta1a and beta2b) subunit genes are expressed in ear beginning at mid-somitogenesis. Each gene exhibits a distinct spatial and temporal expression pattern. The alpha1a.1 gene was ubiquitously expressed in the otic epithelium from mid-somitogenesis to 24 hr postfertilization (hpf). Expression of this gene was gradually reduced and by 48 hpf, alpha1a.1 transcripts were no longer detectable in the ear. The alpha1a.2 and alpha1a.5 genes were expressed in regions that correspond to the anterior macula, lateral crista, and semicircular canal projections up to 48 hpf. At later stages, expression of these genes was limited to cells in the dorsolateral septum and semicircular canal projections. alpha1a.4 and beta1a transcripts were ubiquitously expressed during ear development and were present in most otic tissues at 5 days postfertilization (dpf). Expression of the beta2b gene, on the other hand, was restricted to subsets of cells that form sensory epithelia. These results strongly suggest different functional roles for individual Na,K-ATPase genes in zebrafish ear development. Na,K-ATPase genes are likely to represent useful markers for the analysis of zebrafish otogenesis. Copyright 2003 Wiley-Liss, Inc.

PMID: 14579377 [PubMed - indexed for MEDLINE]

42. Development. 2003 Sep;130(17):3989-4000.

The role of Six1 in mammalian auditory system development.

Zheng W, Huang L, Wei ZB, Silvius D, Tang B, Xu PX.

McLaughlin Research Institute for Biomedical Sciences, 1520 23rd Street South, Great Falls, MT 59405, USA.

The homeobox Six genes, homologues to Drosophila sine oculis (so) gene, are expressed in multiple organs during mammalian development. However, their roles during auditory system development have not been studied. We report that Six1 is required for mouse auditory system development. During inner ear development, Six1 expression was first detected in the ventral region of the otic pit and later is restricted to the middle and ventral otic vesicle within which, respectively, the vestibular and auditory epithelia form. By contrast, Six1 expression is excluded from the dorsal otic vesicle within which the semicircular canals form. Six1 is also expressed in the vestibuloacoustic ganglion. At E15.5, Six1 is expressed in all sensory epithelia of the inner ear. Using recently generated Six1 mutant mice, we found that all Six1(+/-) mice showed some degree of hearing loss because of a failure of sound transmission in the middle ear. By contrast, Six1(-/-) mice displayed malformations of the auditory system involving the outer, middle and inner ears. The inner ear development in Six1(-/-) embryos arrested at the otic vesicle stage and all components of the inner ear failed to form due to increased cell death and reduced cell proliferation in the otic epithelium. Because we previously reported that Six1 expression in the otic vesicle is Eya1 dependent, we first clarified that Eya1 expression was unaffected in Six1(-/-) otic vesicle, further demonstrating that the Drosophila Eya-Six regulatory cassette is evolutionarily conserved during mammalian inner ear development. We also analyzed several other otic markers and found that the expression of Pax2 and Pax8 was unaffected in Six1(-/-) otic vesicle. By contrast, Six1 is required for the activation of Fgf3 expression and the maintenance of Fgf10 and Bmp4 expression in the otic vesicle. Furthermore, loss of Six1 function alters the expression pattern of Nkx5.1 and Gata3, indicating that Six1 is required for regional specification of the otic vesicle. Finally, our data suggest that the interaction between Eya1 and Six1 is crucial for the morphogenesis of the cochlea and the posterior ampulla during inner ear development. These analyses establish a role for Six1 in early growth and patterning of the otic vesicle.

PMID: 12874121 [PubMed - indexed for MEDLINE]

43. Dev Dyn. 2003 Jul;227(3):422-30.

Three-dimensional morphology of inner ear development in Xenopus laevis.

Bever MM, Jean YY, Fekete DM.

Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.

The three-dimensional morphology of the membranous labyrinth of Xenopus laevis is presented from embryonic through late tadpole development (stages 28 to 52, inclusive). This was accomplished by paint-filling the endolymphatic spaces of Xenopus ears at a series of stages, beginning with the embryonic otic vesicle and ending with the complex ear of the late tadpole. At stage 52, the inner ear has expanded approximately 23-fold in its anterior/posterior dimension compared with stage 28 and it is a miniature of the adult form. The paint-filling technique illustrates the dramatic changes required to convert a simple ear vesicle into the elaborate form of the adult, including semicircular canal formation and genesis of vestibular and auditory organs, and it can serve as a basis for phenotype identification in experimentally or genetically manipulated ears. Copyright 2003 Wiley-Liss, Inc.

PMID: 12815629 [PubMed - indexed for MEDLINE]

44. J Neurophysiol. 2003 Aug;90(2):1266-78. Epub 2003 Apr 17.

Na+ currents in vestibular type I and type II hair cells of the embryo and adult chicken.

Masetto S, Bosica M, Correia MJ, Ottersen OP, Zucca G, Perin P, Valli P.

Dipartimento di Scienze Fisiologiche-Farmacologiche Cellulari-Molecolari-Sez. di Fisiologia Generale e Biofisica Cellulare, Università di Pavia, 27100 Pavia, Italy. smasetto@unipv.it

In birds, type I and type II hair cells differentiate before birth. Here we describe that chick hair cells, from the semicircular canals, begin expressing a voltage-dependent Na current (INa) from embryonic day 14 (E14) and continue to express the current up to hatching (E21). During this period, INa was present in most (31/43) type I hair cells irrespective of their position in the crista, in most type II hair cells located far from the planum semilunatum (48/63), but only occasionally in type II hair cells close to the planum semilunatum (2/35). INa activated close to -60 mV, showed fast time- and voltage-dependent activation and inactivation, and was completely, and reversibly, blocked by submicromolar concentrations of tetrodotoxin (Kd = 17 nM). One peculiar property of INa concerns its steady-state inactivation, which is complete at -60 mV (half-inactivating voltage = -96 mV). INa was found in type I and type II hair cells from the adult chicken as well, where it had similar, although possibly not identical, properties and regional distribution. Current-clamp experiments showed that INa could contribute to the voltage response provided that the cell membrane was depolarized from holding potentials more negative than -80 mV. When recruited, INa produced a significant acceleration of the cell membrane depolarization, which occasionally elicited a large rapid depolarization followed by a rapid repolarization (action-potential-like response). Possible physiological roles for INa in the embryo and adult chicken are discussed.

PMID: 12702715 [PubMed - indexed for MEDLINE]

45. Mol Cell Biol. 2003 Apr;23(7):2277-86.

Retinoic acid repression of bone morphogenetic protein 4 in inner ear development.

Thompson DL, Gerlach-Bank LM, Barald KF, Koenig RJ.

Department of Internal Medicine, Endocrinology Division, University of Michigan, Ann Arbor, Michigan 48109-0678, USA.

Bone morphogenetic protein 4 (BMP4) and retinoic acid are important for normal development of the inner ear, but whether they are linked mechanistically is not known. BMP4 antagonists disrupt semicircular canal formation, as does exposure to retinoic acid. We demonstrate that retinoic acid directly down-regulates BMP4 transcription in a mouse inner ear-derived cell line, and we identify a novel promoter in the second intron of the BMP4 gene that is a target of this regulation both in the cell line and in the mouse embryonic inner ear in vivo. The importance of this down-regulation is demonstrated in chicken embryos by showing that the retinoic acid effect on semicircular canal development can be overcome by exogenous BMP4.

PMCID: PMC150746 PMID: 12640113 [PubMed - indexed for MEDLINE]

46. J Neurophysiol. 2002 Dec;88(6):3175-93.

Responses of primate caudal parabrachial nucleus and Kölliker-fuse nucleus neurons to whole body rotation.

Balaban CD, McGee DM, Zhou J, Scudder CA.

Collaborators: Balaban CD.

Department of Otolaryngology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. cbalaban@pitt.edu

The caudal aspect of the parabrachial (PBN) and Kölliker-Fuse (KF) nuclei receive vestibular nuclear and visceral afferent information and are connected reciprocally with the spinal cord, hypothalamus, amygdala, and limbic cortex. Hence, they may be important sites of vestibulo-visceral integration, particularly for the development of affective responses to gravitoinertial challenges. Extracellular recordings were made from caudal PBN cells in three alert, adult female Macaca nemestrina through an implanted chamber. Sinusoidal and position trapezoid angular whole body rotation was delivered in yaw, roll, pitch, and vertical semicircular canal planes. Sites were confirmed histologically. Units that responded during rotation were located in lateral and medial PBN and KF caudal to the trochlear nerve at sites that were confirmed anatomically to receive superior vestibular nucleus afferents. Responses to whole-body angular rotation were modeled as a sum of three signals: angular velocity, a leaky integration of angular velocity, and vertical position. All neurons displayed angular velocity and integrated angular velocity sensitivity, but only 60% of the neurons were position-sensitive. These responses to vertical rotation could display symmetric, asymmetric, or fully rectified cosinusoidal spatial tuning about a best orientation in different cells. The spatial properties of velocity and integrated velocity and position responses were independent for all position-sensitive neurons; the angular velocity and integrated angular velocity signals showed independent spatial tuning in the position-insensitive neurons. Individual units showed one of three different orientations of their excitatory axis of velocity rotation sensitivity: vertical-plane-only responses, positive elevation responses (vertical plane plus ipsilateral yaw), and negative elevation axis responses (vertical plane plus negative yaw). The interactions between the velocity and integrated velocity components also produced variations in the temporal pattern of responses as a function of rotation direction. These findings are consistent with the hypothesis that a vestibulorecipient region of the PBN and KF integrates signals from the vestibular nuclei and relay information about changes in whole-body orientation to pathways that produce homeostatic and affective responses.

PMID: 12466439 [PubMed - indexed for MEDLINE]

47. Brain. 2002 Sep;125(Pt 9):2081-8.

Vestibular-evoked postural responses in the absence of somatosensory information.

Day BL, Cole J.

MRC Human Movement Group, Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK. b.day@ion.ucl.ac.uk

In order to investigate the ways in which sensory channels interact to control balance, we measured the postural response evoked by galvanic vestibular stimulation (GVS) in a rare subject (I. W.) with a large-fibre sensory neuronopathy. I. W. has no sensations of cutaneous light touch and movement/position sense below the neck, and without vision he has no knowledge of where his limbs and body are in space. He was tested with and without vision while seated. With eyes closed, I. W.'s responses to pure vestibular stimuli were an order of magnitude larger than those of healthy controls. In other respects his responses were normal. Part of this phenomenon may have been due to lack of response modification by somatosensory feedback. However, the initial development of his ground reaction force, which is the earliest mechanical indicator of the response, differed from that of a control subject from its beginning. Similarly, opening his eyes resulted in a reduction (>50%) of the response from its beginning. We propose that these early changes reflect changes in initial response selection, possibly by alterations in the gain of vestibulopostural channels. We suggest that similar gain changes operate in healthy subjects and occur through a fast dynamic process. A model is put forward in which the weight of each sensory channel is adjusted continuously in a competitive manner according to the balance-relevant information content of the other sensory channels. As a secondary issue, the nature of I. W.'s head and trunk tilt response provides insight into the question of which vestibular afferents are recruited by GVS. I. W.'s responses consisted of an initial, relatively fast tilt followed by a slower, continuous tilt. When the stimulus was turned off, his body partially tilted back at an intermediate velocity. We modelled this behaviour as the algebraic sum of a position response and a constant velocity response. We suggest that these two components arise from stimulation of otolith and semicircular canal afferents, respectively.

PMID: 12183353 [PubMed - indexed for MEDLINE]

48. Dev Dyn. 2002 Apr;223(4):536-43.

Atlas of the developing inner ear in zebrafish.

Bever MM, Fekete DM.

Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA. mbever@bilbo.bio.purdure.edu

This report provides a description of the normal developing inner ear of the zebrafish, Danio rerio, with special focus on the pars inferior. Zebrafish specimens, ranging in age from 3 to 30 days postfertilization (dpf), were processed for standard histologic sections or with a paint-fill method to show three-dimensional morphogenesis of the membranous labyrinth. Adult zebrafish (age 2 years) were also processed for inner ear paint-fills. Although development of the semicircular canals occurs rapidly (by 3 dpf), the pars inferior develops more gradually during days 5-20 postfertilization. A rudimentary endolymphatic duct emerges by 8 dpf. Differentiated hair cells of the lagenar macula are evident by 15 dpf, in a chamber located lateral and posterior to the saccule. By 20 dpf, the saccule itself is separated from the utricle, but remains connected by means of the utriculosaccular foramen. The maculae neglectae, each with differentiated hair cells, lie on the floor of the utricle near this foramen. A medial connection between the sacculi of right and left ears, the transverse canal, is also complete by 20 dpf. A ridge of mesenchyme, previously undescribed, bisects the saccule in zebrafish fry at 20-30 dpf. The images in the paint-fill atlas should provide a baseline for future studies of mutant zebrafish ears. Copyright 2002 Wiley-Liss, Inc.

PMID: 11921341 [PubMed - indexed for MEDLINE]

49. Dev Dyn. 2002 Apr;223(4):517-25.

Vestibular dysgenesis in mice lacking Abr and Bcr Cdc42/RacGAPs.

Kaartinen V, Nagy A, Gonzalez-Gomez I, Groffen J, Heisterkamp N.

Developmental Biology Program, Department of Pathology and Laboratory Medicine, Childrens Hospital Los Angeles Research Institute, Los Angeles, California 90027, USA. vkaartinen@chla.usc.edu

The inner ear develops from a simple epithelium (otic placode) into the complex structures specialized for balance (vestibule) and sound (cochlea) detection. Abnormal vestibular and cochlear development is associated with many birth defects. During recent years, considerable progress has been made in understanding the molecular bases of these conditions. To determine the biological function of two closely related GTPase activating proteins for the Cdc42/Rac GTPases, Abr and Bcr, we generated a mouse strain deficient in both of these proteins. Double null mutant mice exhibit hyperactivity, persistent circling, and are unable to swim. These phenotypes are typically found in mice with vestibular defects. Indeed, adult double null mutants display abnormal dysmorphic structures of both the saccule and utricle. Moreover, a total loss of otoconia can be seen in the utricle, whereas in the saccule, otoconia are either missing or their number is drastically decreased and they are abnormally large. Interestingly, both the cochlea and semicircular canals are normal and the double null mutant mice are not deaf. These data demonstrate that Abr and Bcr play important complementary roles during vestibular morphogenesis and that a function of Cdc42/RacGAPs and, therefore, that of the small Rho-related GTPases is critically important for balance and motor coordination. Copyright 2002 Wiley-Liss, Inc.

PMID: 11921339 [PubMed - indexed for MEDLINE]

50. Mol Cell Biol. 2002 Feb;22(3):935-45.

The nuclear receptor Nor-1 is essential for proliferation of the semicircular canals of the mouse inner ear.

Ponnio T, Burton Q, Pereira FA, Wu DK, Conneely OM.

Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.

Nor-1 belongs to the nur subfamily of nuclear receptor transcription factors. The precise role of Nor-1 in mammalian development has not been established. However, recent studies indicate a function for this transcription factor in oncogenesis and apoptosis. To examine the spatiotemporal expression pattern of Nor-1 and the developmental and physiological consequences of Nor-1 ablation, Nor-1-null mice were generated by insertion of the lacZ gene into the Nor-1 genomic locus. Disruption of the Nor-1 gene results in inner ear defects and partial bidirectional circling behavior. During early otic development, Nor-1 is expressed exclusively in the semicircular canal forming fusion plates. After formation of the membranous labyrinth, Nor-1 expression in the vestibule is limited to nonsensory epithelial cells localized at the inner edge of the semicircular canals and to the ampullary and utricular walls. In the absence of Nor-1, the vestibular walls fuse together as normal; however, the endolymphatic fluid space in the semicircular canals is diminished and the roof of the ampulla appears flattened due to defective continual proliferative growth of the semicircular canals.

PMCID: PMC133552 PMID: 11784868 [PubMed - indexed for MEDLINE]

51. Hum Mol Genet. 2001 Mar 1;10(5):507-12.

The mouse slalom mutant demonstrates a role for Jagged1 in neuroepithelial patterning in the organ of Corti.

Tsai H, Hardisty RE, Rhodes C, Kiernan AE, Roby P, Tymowska-Lalanne Z, Mburu P, Rastan S, Hunter AJ, Brown SD, Steel KP.

MRC Mammalian Genetics Unit and Mouse Genome Centre, Harwell, Oxon OX11 ORD, UK.

The Notch signalling pathway has recently been implicated in the development and patterning of the sensory epithelium in the cochlea, the organ of Corti. As part of an ongoing large-scale mutagenesis programme to identify new deaf or vestibular mouse mutants, we have identified a novel mouse mutant, slalom, which shows abnormalities in the patterning of hair cells in the organ of Corti and missing ampullae, structures that house the sensory epithelia of the semicircular canals. We show that the slalom mutant carries a mutation in the Jagged1 gene, implicating a new ligand in the signalling processes that pattern the inner ear neuro-epithelium.

PMID: 11181574 [PubMed - indexed for MEDLINE]

52. Neural Plast. 2000;7(3):193-203.

Vestibular deprivation and the development of dendrite bundles in the rat.

Geisler HC, IJkema-Paassen J, Westerga J, Gramsbergen A.

Department of Pediatrics, Free University of Berlin, Hindenburgdamm 30, 12220 Berlin, Germany.

Motoneuronal pools of muscles that subserve postural tasks contain dendrite bundles. We investigated in the rat the development of these bundles in the pools of the long back muscles and related this to postural development. Motoneurons and their dendrites were retrogradely labeled by injecting unconjugated cholera toxin subunit B (CTB) into the muscles of 54 normal rats from birth until adulthood and into 18 rats that were vestibularly deprived from the 5th postnatal day (P5). Dendrite bundles coursing in a transverse direction already occurred at P1. From P4, the first longitudinal bundles could be observed, but the major spurt in development occurred between P6 and P9, when conspicuous bundles developed coursing in rostro-caudal and transverse directions. This is the age when rats become able to stand freely and walk a few steps. Around P20, the dendrite bundles attained their adult characteristics. Vestibular deprivation by plugging both semicircular horizontal canals did not lead to a retarded development of dendrite bundles nor to a changed morphology. This finding is remarkable, as behavioral analysis showed a delay in postural development by about 3 days. We hypothesize that dendrite bundles in the pools of the long back muscles function to synchronize the motoneurons in different spinal cord segments.

PMCID: PMC2565352 PMID: 11147461 [PubMed - indexed for MEDLINE]

53. J Neurophysiol. 2000 May;83(5):2740-56.

Membrane properties of chick semicircular canal hair cells in situ during embryonic development.

Masetto S, Perin P, Malusà A, Zucca G, Valli P.

Dipartimento di Scienze Fisiologiche-Farmacologiche Cellulari-Molecolari, Sez. di Fisiologia Generale e Biofisica Cellulare, 27100 Pavia, Italy.

The electrophysiological properties of developing vestibular hair cells have been investigated in a chick crista slice preparation, from embryonic day 10 (E10) to E21 (when hatching would occur). Patch-clamp whole-cell experiments showed that different types of ion channels are sequentially expressed during development. An inward Ca(2+) current and a slow outward rectifying K(+) current (I(K(V))) are acquired first, at or before E10, followed by a rapid transient K(+) current (I(K(A))) at E12, and by a small Ca-dependent K(+) current (I(KCa)) at E14. Hair cell maturation then proceeds with the expression of hyperpolarization-activated currents: a slow I(h) appears first, around E16, followed by the fast inward rectifier I(K1) around E19. From the time of its first appearance, I(K(A)) is preferentially expressed in peripheral (zone 1) hair cells, whereas inward rectifying currents are preferentially expressed in intermediate (zone 2) and central (zone 3) hair cells. Each conductance conferred distinctive properties on hair cell voltage response. Starting from E15, some hair cells, preferentially located at the intermediate region, showed the amphora shape typical of type I hair cells. From E17 (a time when the afferent calyx is completed) these cells expressed I(K, L), the signature current of mature type I hair cells. Close to hatching, hair cell complements and regional organization of ion currents appeared similar to those reported for the mature avian crista. By the progressive acquisition of different types of inward and outward rectifying currents, hair cell repolarization after both positive- and negative-current injections is greatly strengthened and speeded up.

PMID: 10805673 [PubMed - indexed for MEDLINE]

54. Arch Otolaryngol Head Neck Surg. 2000 Feb;126(2):137-47.

Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey.

Carey JP, Minor LB, Nager GT.

Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.

OBJECTIVE: To determine the incidence and etiology of dehiscences of bone overlying the superior semicircular canal in a temporal bone archive. DESIGN: A microscopic study was performed of 1000 temporal bones from 596 adults in a university hospital registry. Specimens were sectioned vertically in the plane of the superior semicircular canal. Measurements of minimum bone thickness over the superior canal were made in a subset of 108 randomly chosen specimens. All bones were examined for thinning or dehiscence relative to these norms. Clinical histories, when available, were reviewed. RESULTS: Complete dehiscence of the superior canal was identified in 5 specimens (0.5%), at the middle fossa floor (n = 1) and where the superior petrosal sinus was in contact with the canal (n = 4). In 14 other specimens (1.4%), the bone at the middle fossa floor (n = 8) or superior petrosal sinus (n = 6) was no thicker than 0.1 mm, significantly less than values measured in the control specimens (P<.001). Abnormalities were typically bilateral. Specimens from infants demonstrated uniformly thin bone over the superior canal in the middle fossa at birth, with gradual thickening until 3 years of age. CONCLUSIONS: Dehiscence of bone overlying the superior canal occurred in approximately 0.5% of temporal bone specimens (0.7% of individuals). In an additional 1.4% of specimens (1.3% of individuals), the bone was markedly thin (< or =0.1 mm), such that it might appear dehiscent even on ultra-high-resolution computed tomography of the temporal bone. Sites affected were in the middle fossa floor or a deep groove for the superior petrosal sinus, often bilaterally. These abnormalities may arise from failure of postnatal bone development. Thin areas of bone over the superior canal may be predisposed to disruption by trauma.

PMID: 10680863 [PubMed - indexed for MEDLINE]

55. Development. 2000 Jan;127(1):45-54.

Addition of the BMP4 antagonist, noggin, disrupts avian inner ear development.

Gerlach LM, Hutson MR, Germiller JA, Nguyen-Luu D, Victor JC, Barald KF.

Program in Cellular and Molecular Biology, Center for Organogenesis, University of Michigan Medical School, Ann Arbor 48109-0616, USA.

Bone morphogenetic protein 4 (BMP4) is known to regulate dorsoventral patterning, limb bud formation and axis specification in many organisms, including the chicken. In the chick developing inner ear, BMP4 expression becomes localized in two cell clusters at the anterior and posterior edges of the otic epithelium beginning at stage 16/17 and is expressed in presumptive sensory tissue at later stages. This restricted spatiotemporal pattern of expression occurs just prior to the otocyst's transition to a more complex three-dimensional structure. To further analyze the role of BMP4 in avian otic morphogenesis, cells expressing BMP4 or its antagonist, noggin, were grown on agarose beads and implanted into the periotic mesenchyme surrounding the chick otocyst. Although the BMP4-producing cells had no effect on the mature inner ear structure when implanted alone, noggin-producing cells implanted adjacent to the BMP4 cell foci prevented normal semicircular canal development. Beads implanted at the anterior BMP4 focus eliminated the anterior and/or the horizontal canals. Noggin cells implanted at the posterior focus eliminated the posterior canal. Canal loss was prevented by co-implantation of BMP4 cell beads next to noggin beads. An antibody to the chick hair cell antigen (HCA) was used to examine sensory cell distribution, which was abnormal only in the affected tissues of noggin-exposed inner ears. These data suggest a role for BMP4 in the accurate and complete morphological development of the semicircular canals.

PMID: 10654599 [PubMed - indexed for MEDLINE]

56. Development. 2000 Jan;127(1):13-22.

Netrin 1 is required for semicircular canal formation in the mouse inner ear.

Salminen M, Meyer BI, Bober E, Gruss P.

Department of Molecular Cell Biology, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.

The morphogenetic development of the mammalian inner ear is a complex multistep process, the molecular and cellular details of which are only beginning to be unraveled. We show here that mouse netrin 1, known to be involved in axon guidance and cell migration in the central nervous system, also plays a critical morphogenetic role during semicircular canal formation. netrin 1 is expressed at high levels in the otic epithelium, in cells that will come together to form a fusion plate, a prerequisite for the formation of semicircular canals. In netrin 1 mutant mice, fusion plate formation is severely affected resulting in a reduced anterior semicircular canal and the complete lack of the posterior and lateral canals. Our results suggest that netrin 1 facilitates semicircular canal formation through two different mechanisms: (1) it participates in the detachment of the fusion plate epithelia from the basement membrane, and (2) it stimulates proliferation of the periotic mesenchymal cells which then push the epithelial cell walls together to form the fusion plate.

PMID: 10654596 [PubMed - indexed for MEDLINE]

57. Development. 1999 Sep;126(17):3831-46.

Dlx5 regulates regional development of the branchial arches and sensory capsules.

Depew MJ, Liu JK, Long JE, Presley R, Meneses JJ, Pedersen RA, Rubenstein JL.

Nina Ireland Laboratory of Developmental Neurobiology, Center for Neurobiology and Psychiatry, Department of Psychiatry and Programs in Neuroscience, Developmental Biology, Oral Biology and Biomedical Sciences, University of California at San Fran.

We report the generation and analysis of mice homozygous for a targeted deletion of the Dlx5 homeobox gene. Dlx5 mutant mice have multiple defects in craniofacial structures, including their ears, noses, mandibles and calvaria, and die shortly after birth. A subset (28%) exhibit exencephaly. Ectodermal expression of Dlx5 is required for the development of olfactory and otic placode-derived epithelia and surrounding capsules. The nasal capsules are hypoplastic (e.g. lacking turbinates) and, in most cases, the right side is more severely affected than the left. Dorsal otic vesicle derivatives (e. g. semicircular canals and endolymphatic duct) and the surrounding capsule, are more severely affected than ventral (cochlear) structures. Dlx5 is also required in mandibular arch ectomesenchyme, as the proximal mandibular arch skeleton is dysmorphic. Dlx5 may control craniofacial development in part through the regulation of the goosecoid homeobox gene. goosecoid expression is greatly reduced in Dlx5 mutants, and both goosecoid and Dlx5 mutants share a number of similar craniofacial malformations. Dlx5 may perform a general role in skeletal differentiation, as exemplified by hypomineralization within the calvaria. The distinct focal defects within the branchial arches of the Dlx1, Dlx2 and Dlx5 mutants, along with the nested expression of their RNAs, support a model in which these genes have both redundant and unique functions in the regulation of regional patterning of the craniofacial ectomesenchyme.

PMID: 10433912 [PubMed - indexed for MEDLINE]

58. J Neurosci. 1999 Jul 15;19(14):5980-9.

Targeted mutagenesis of the POU-domain gene Brn4/Pou3f4 causes developmental defects in the inner ear.

Phippard D, Lu L, Lee D, Saunders JC, Crenshaw EB 3rd.

Department of Neuroscience, Head and Neck Surgery, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6074, USA.

Targeted mutagenesis in mice demonstrates that the POU-domain gene Brn4/Pou3f4 plays a crucial role in the patterning of the mesenchymal compartment of the inner ear. Brn4 is expressed extensively throughout the condensing mesenchyme of the developing inner ear. Mutant animals displayed behavioral anomalies that resulted from functional deficits in both the auditory and vestibular systems, including vertical head bobbing, changes in gait, and hearing loss. Anatomical analyses of the temporal bone, which is derived in part from the otic mesenchyme, demonstrated several dysplastic features in the mutant animals, including enlargement of the internal auditory meatus. Many phenotypic features of the mutant animals resulted from the reduction or thinning of the bony compartment of the inner ear. Histological analyses demonstrated a hypoplasia of those regions of the cochlea derived from otic mesenchyme, including the spiral limbus, the scala tympani, and strial fibrocytes. Interestingly, we observed a reduction in the coiling of the cochlea, which suggests that Brn-4 plays a role in the epithelial-mesenchymal communication necessary for the cochlear anlage to develop correctly. Finally, the stapes demonstrated several malformations, including changes in the size and morphology of its footplate. Because the stapes anlage does not express the Brn4 gene, stapes malformations suggest that the Brn4 gene also plays a role in mesenchymal-mesenchymal signaling. On the basis of these data, we suggest that Brn-4 enhances the survival of mesodermal cells during the mesenchymal remodeling that forms the mature bony labyrinth and regulates inductive signaling mechanisms in the otic mesenchyme.

PMID: 10407036 [PubMed - indexed for MEDLINE]

59. Development. 1999 Jun;126(11):2335-43.

Otx1 and Otx2 activities are required for the normal development of the mouse inner ear.

Morsli H, Tuorto F, Choo D, Postiglione MP, Simeone A, Wu DK.

National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA.

The Otx1 and Otx2 genes are two murine orthologues of the Orthodenticle (Otd) gene in Drosophila. In the developing mouse embryo, both Otx genes are expressed in the rostral head region and in certain sense organs such as the inner ear. Previous studies have shown that mice lacking Otx1 display abnormal patterning of the brain, whereas embryos lacking Otx2 develop without heads. In this study, we examined, at different developmental stages, the inner ears of mice lacking both Otx1 and Otx2 genes. In wild-type inner ears, Otx1, but not Otx2, was expressed in the lateral canal and ampulla, as well as part of the utricle. Ventral to the mid-level of the presumptive utricle, Otx1 and Otx2 were co-expressed, in regions such as the saccule and cochlea. Paint-filled membranous labyrinths of Otx1-/- mutants showed an absence of the lateral semicircular canal, lateral ampulla, utriculosaccular duct and cochleosaccular duct, and a poorly defined hook (the proximal part) of the cochlea. Defects in the shape of the saccule and cochlea were variable in Otx1-/- mice and were much more severe in an Otx1-/-;Otx2(+/)- background. Histological and in situ hybridization experiments of both Otx1-/- and Otx1-/-;Otx2(+/)- mutants revealed that the lateral crista was absent. In addition, the maculae of the utricle and saccule were partially fused. In mutant mice in which both copies of the Otx1 gene were replaced with a human Otx2 cDNA (hOtx2(1)/ hOtx2(1)), most of the defects associated with Otx1-/- mutants were rescued. However, within the inner ear, hOtx2 expression failed to rescue the lateral canal and ampulla phenotypes, and only variable rescues were observed in regions where both Otx1 and Otx2 are normally expressed. These results suggest that both Otx genes play important and differing roles in the morphogenesis of the mouse inner ear and the development of its sensory organs.

PMID: 10225993 [PubMed - indexed for MEDLINE]

60. Arch Otolaryngol Head Neck Surg. 1999 Mar;125(3):342-7.

Vestibular function in children with the CHARGE association.

Wiener-Vacher SR, Amanou L, Denise P, Narcy P, Manach Y.

Department of Otorhinolaryngology, Hôpital Robert Debré, University of Paris VII, France. sylvette.wiener@rdb.ap-hop-paris.fr

BACKGROUND: Histopathological examinations and computed tomographic scans of the temporal bone in patients with the CHARGE association (a malformative syndrome that includes coloboma, heart disease, choanal atresia, retarded development, genital hypoplasia, and ear anomalies, including hypoplasia of the external ear and hearing loss) have shown an absence of semicircular canals and a Mondini form of cochlear dysplasia. Until recently, no information was available concerning a possible loss of vestibular function, which could be a factor in retarded posturomotor development. To our knowledge, this is the first report of otolith tests done on patients with the CHARGE association. OBJECTIVE: To test residual vestibular function in patients with the CHARGE association. STUDY DESIGN: In 7 patients with the CHARGE association, we made electro-oculographic recordings of vestibulo-ocular responses to earth-vertical and off-vertical axis rotations to evaluate the function of the canal and the otolith-vestibular systems. RESULTS: None of the 7 patients had semicircular canals in the computed tomographic scan, and none had canal vestibulo-ocular responses to earth-vertical axis rotation, but all had normal otolith vestibulo-ocular responses to the off-vertical axis rotation test. CONCLUSIONS: These results support the hypothesis of a residual functional otolith organ in the hypoplastic posterior labyrinth of children with the CHARGE association. The severe delays in psychomotor development presented by these children are more likely a consequence of multiple factors: canal vestibular deficit, visual impairment, and environmental conditions (long hospital stays and breathing and feeding problems). The remaining sensitivity of the otolith system to gravity and linear acceleration forces in these children could be exploited in early education programs to improve their posturomotor development.

PMID: 10190809 [PubMed - indexed for MEDLINE]

61. Development. 1999 Apr;126(7):1417-26.

Differential transcriptional control as the major molecular event in generating Otx1-/- and Otx2-/- divergent phenotypes.

Acampora D, Avantaggiato V, Tuorto F, Barone P, Perera M, Choo D, Wu D, Corte G, Simeone A.

International Institute of Genetics and Biophysics, CNR, Via G. Marconi 12, Italy. simeone@iigbna.iigb.na.cnr.it

Otx1 and Otx2, two murine homologs of the Drosophila orthodenticle (otd) gene, show a limited amino acid sequence divergence. Their embryonic expression patterns overlap in spatial and temporal profiles with two major exceptions: until 8 days post coitum (d.p.c. ) only Otx2 is expressed in gastrulating embryos, and from 11 d.p.c. onwards only Otx1 is transcribed within the dorsal telencephalon. Otx1 null mice exhibit spontaneous epileptic seizures and multiple abnormalities affecting primarily the dorsal telencephalic cortex and components of the acoustic and visual sense organs. Otx2 null mice show heavy gastrulation abnormalities and lack the rostral neuroectoderm corresponding to the forebrain, midbrain and rostral hindbrain. In order to define whether these contrasting phenotypes reflect differences in expression pattern or coding sequence of Otx1 and Otx2 genes, we replaced Otx1 with a human Otx2 (hOtx2) full-coding cDNA. Interestingly, homozygous mutant mice (hOtx2(1)/hOtx2(1)) fully rescued epilepsy and corticogenesis abnormalities and showed a significant improvement of mesencephalon, cerebellum, eye and lachrymal gland defects. In contrast, the lateral semicircular canal of the inner ear was never recovered, strongly supporting an Otx1-specific requirement for the specification of this structure. These data indicate an extended functional homology between OTX1 and OTX2 proteins and provide evidence that, with the exception of the inner ear, in Otx1 and Otx2 null mice contrasting phenotypes stem from differences in expression patterns rather than in amino acid sequences.

PMID: 10068635 [PubMed - indexed for MEDLINE]

62. Proc Natl Acad Sci U S A. 1999 Jan 19;96(2):529-34.

Characterization of otoconin-95, the major protein of murine otoconia, provides insights into the formation of these inner ear biominerals.

Verpy E, Leibovici M, Petit C.

Unité de Génétique des Déficits Sensoriels, Centre National de la Recherche Scientifique Unité de Recherche Associée 1968, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris cedex 15, France.

During the course of a study aimed at identifying inner ear-specific transcripts, a 1,906-bp murine cDNA predicted to encode a secreted 469-aa protein with two domains of homology with the secreted phospholipases A2 was isolated. This transcript is specifically expressed in the inner ear from embryonic day 9.5. The encoded 95-kDa glycoprotein is the major protein of the utricular and saccular otoconia and thus was named otoconin-95. By immunohistofluorescence, otoconin-95 also was detected in the cupulae of the semicircular canals and in previously undescribed transient granular structures of the cochlea. Otoconin-95 was found to be synthesized by various nonsensory cell types, but not by the supporting cells of the sensory epithelia, which produce the otoconial precursor vesicles. In addition, multiple isoforms generated by differential splicing were observed in different combinations during development. Based on the present results, we propose a model for the formation of the otoconia.

PMCID: PMC15170 PMID: 9892667 [PubMed - indexed for MEDLINE]

63. Development. 1998 Feb;125(4):621-34.

Inner ear and maternal reproductive defects in mice lacking the Hmx3 homeobox gene.

Wang W, Van De Water T, Lufkin T.

Brookdale Center for Development and Molecular Biology, Mount Sinai School of Medicine, New York, NY 10029-6574, USA.

The Hmx homeobox gene family is of ancient origin, being present in species as diverse as Drosophila, sea urchin and mammals. The three members of the murine Hmx family, designated Hmx1, Hmx2 and Hmx3, are expressed in tissues that suggest a common functional role in sensory organ development and pregnancy. Hmx3 is one of the earliest markers for vestibular inner ear development during embryogenesis, and is also upregulated in the myometrium of the uterus during pregnancy. Targeted disruption of the Hmx3 gene results in mice with abnormal circling behavior and severe vestibular defects owing to a depletion of sensory cells in the saccule and utricle, and a complete loss of the horizontal semicircular canal crista, as well as a fusion of the utricle and saccule endolymphatic spaces into a common utriculosaccular cavity. Both the sensory and secretory epithelium of the cochlear duct appear normal in the Hmx3 null animals. The majority of Hmx3 null females have a reproductive defect. Hmx3 null females can be fertilized and their embryos undergo normal preimplantation development, but the embryos fail to implant successfully in the Hmx3 null uterus and subsequently die. Transfer of preimplantation embryos from mutant Hmx3 uterine horns to wild-type pseudopregnant females results in successful pregnancy, indicating a failure of the Hmx3 null uterus to support normal post-implantation pregnancy. Molecular analysis revealed the perturbation of Hmx, Wnt and LIF gene expression in the Hmx3 null uterus. Interestingly, expression of both Hmx1 and Hmx2 is downregulated in the Hmx3 null uterus, suggesting a hierarchical relationship among the three Hmx genes during pregnancy.

PMID: 9435283 [PubMed - indexed for MEDLINE]

64. J Appl Physiol. 1998 Feb;84(2):450-3.

Neck afferents and muscle sympathetic activity in humans: implications for the vestibulosympathetic reflex.

Ray CA, Hume KM.

Department of Exercise Science, University of Georgia, Athens 30602, USA. caray@coe.uga.edu

We have shown previously that head-down neck flexion (HDNF) in humans elicits increases in muscle sympathetic nerve activity (MSNA). The purpose of this study was to determine the effect of neck muscle afferents on MSNA. We studied this question by measuring MSNA before and after head rotation that would activate neck muscle afferents but not the vestibular system (i.e., no stimulation of the otolith organs or semicircular canals). After a 3-min baseline period with the head in the normal erect position, subjects rotated their head to the side (approximately 90%) and maintained this position for 3 min. Head rotation was performed by the subjects in both the prone (n = 5) and sitting (n = 6) positions. Head rotation did not elicit changes in MSNA. Average MSNA, expressed as burst frequency and total activity, was 13 +/- 1 and 13 +/- 1 bursts/min and 146 +/-34 and 132 +/- 27 units/min during baseline and head rotation, respectively. There were no significant changes in calf blood flow (2.6 +/- 0.3 to 2.5 +/- 0.3 ml.100 ml-1.min-1, n = 8) and calf vascular resistance (39 +/- 4 to 41 +/- 4 units; n = 8). Heart rate (64 +/- 3 to 66 +/- 3 beats/min; P = 0.058) and mean arterial pressure (90 +/- 3 to 93 +/- 3; P < 0.05) increased slightly during head rotation. Additional neck flexion studies were performed with subjects lying on their side (n = 5), MSNA, heart rate, and mean arterial pressure were unchanged during this maneuver, which also does not engage the vestibular system. HDNF was tested in 9 of the 13 subjects. MSNA was significantly increased by 79 +/- 12% (P < 0.001) during HDNF. These findings indicate that neck afferents activated by horizontal neck rotation or flexion in the absence of significant force development do not elicit changes in MSNA. These findings support the concept that HDNF increases MSNA by the activation of the vestibular system.

PMID: 9475851 [PubMed - indexed for MEDLINE]

65. Development. 1998 Jan;125(1):33-9.

Nkx5-1 controls semicircular canal formation in the mouse inner ear.

Hadrys T, Braun T, Rinkwitz-Brandt S, Arnold HH, Bober E.

Technical University Braunschweig, Department of Cell and Molecular Biology, Germany.

The inner ear develops from the otic vesicle, a one-cell-thick epithelium, which eventually transforms into highly complex structures including the sensory organs for balance (vestibulum) and hearing (cochlea). Several mouse inner ear mutations with hearing and balance defects have been described but for most the underlying genes have not been identified, for example, the genes controlling the development of the vestibular organs. Here, we report the inactivation of the homeobox gene, Nkx5-1, by homologous recombination in mice. This gene is expressed in vestibular structures throughout inner ear development. Mice carrying the Nkx5-1 null mutation exhibit behavioural abnormalities that resemble the typical hyperactivity and circling movements of the shaker/waltzer type mutants. The balance defect correlates with severe malformations of the vestibular organ in Nkx5-1(-/-) mutants, which fail to develop the semicircular canals. Nkx5-1 is the first ear-specific molecule identified to play a crucial role in the formation of the mammalian vestibular system.

PMID: 9389661 [PubMed - indexed for MEDLINE]

66. Development. 1998 Jan;125(1):11-20.

Axial specification for sensory organs versus non-sensory structures of the chicken inner ear.

Wu DK, Nunes FD, Choo D.

National Institute on Deafness and Other Communication Disorders, Rockville, MD 20850, USA. dwu@pop.nidcd.nih.gov

A mature inner ear is a complex labyrinth containing multiple sensory organs and nonsensory structures in a fixed configuration. Any perturbation in the structure of the labyrinth will undoubtedly lead to functional deficits. Therefore, it is important to understand molecularly how and when the position of each inner ear component is determined during development. To address this issue, each axis of the otocyst (embryonic day 2.5, E2.5, stage 16-17) was changed systematically at an age when axial information of the inner ear is predicted to be fixed based on gene expression patterns. Transplanted inner ears were analyzed at E4.5 for gene expression of BMP4 (bone morphogenetic protein), SOHo-1 (sensory organ homeobox-1), Otx1 (cognate of Drosophila orthodenticle gene), p75NGFR (nerve growth factor receptor) and Msx1 (muscle segment homeobox), or at E9 for their gross anatomy and sensory organ formation. Our results showed that axial specification in the chick inner ear occurs later than expected and patterning of sensory organs in the inner ear was first specified along the anterior/posterior (A/P) axis, followed by the dorsal/ventral (D/V) axis. Whereas the A/P axis of the sensory organs was fixed at the time of transplantation, the A/P axis for most non-sensory structures was not and was able to be re-specified according to the new axial information from the host. The D/V axis for the inner ear was not fixed at the time of transplantation. The asynchronous specification of the A/P and D/V axes of the chick inner ear suggests that sensory organ formation is a multi-step phenomenon, rather than a single inductive event.

PMID: 9389659 [PubMed - indexed for MEDLINE]

67. Development. 1997 Jun;124(12):2451-61.

Involvement of programmed cell death in morphogenesis of the vertebrate inner ear.

Fekete DM, Homburger SA, Waring MT, Riedl AE, Garcia LF.

Department of Biology, Boston College, Chestnut Hill, MA 02167, USA. dfekete@bilbo.bio.purdue.edu

An outstanding challenge in developmental biology is to reveal the mechanisms underlying the morphogenesis of complex organs. A striking example is the developing inner ear of the vertebrate, which acquires a precise three-dimensional arrangement of its constituent epithelial cells to form three semicircular canals, a central vestibule and a coiled cochlea (in mammals). In generating a semicircular canal, epithelial cells seem to 'disappear' from the center of each canal. This phenomenon has been variously explained as (i) transdifferentiation of epithelium into mesenchyme, (ii) absorption of cells into the expanding canal or (iii) programmed cell death. In this study, an in situ DNA-end labeling technique (the TUNEL protocol) was used to map regions of cell death during inner ear morphogenesis in the chicken embryo from embryonic days 3.5-10. Regions of cell death previously identified in vertebrate ears have been confirmed, including the ventromedial otic vesicle, the base of the endolymphatic duct and the fusion plates of the semicircular canals. New regions of cell death are also described in and around the sensory organs. Reducing normal death using retrovirus-mediated overexpression of human bcl-2 causes abnormalities in ear morphogenesis: hollowing of the center of each canal is either delayed or fails entirely. These data provide new evidence to explain the role of cell death in morphogenesis of the semicircular canals.

PMID: 9199371 [PubMed - indexed for MEDLINE]

68. AJNR Am J Neuroradiol. 1997 Apr;18(4):773-5.

Absence of the common crus in Goldenhar syndrome.

Manfré L, Genuardi P, Tortorici M, Lagalla R.

Department of Radiology, P. Cignolini, University of Palermo, Italy.

We describe an unusual labyrinthine malformation in a case of Goldenhar syndrome studied with CT and steady-state MR imaging. A single posterosuperior semicircular canal was found with no common crus formation. The malformation could not be attributed to any embryologic development. Nosologic considerations are discussed.

PMID: 9127048 [PubMed - indexed for MEDLINE]

69. Development. 1996 Dec;123:275-83.

Mutations affecting development of the zebrafish ear.

Malicki J, Schier AF, Solnica-Krezel L, Stemple DL, Neuhauss SC, Stainier DY, Abdelilah S, Rangini Z, Zwartkruis F, Driever W.

Cardiovascular Research Center, Massachusetts General Hospital, Charlestown 02129, USA.

In a large scale screen for genetic defects in zebrafish embryogenesis we identified mutations affecting several aspects of ear development, including: specification of the otic placode, growth of the otic vesicle (otocyst), otolith formation, morphogenesis of the semicircular canals and differentiation of the otic capsule. Here we report initial phenotypic and genetic characterization of 20 of these mutations defining 13 independent loci. Embryos mutant at the quadro locus display abnormal specification of the otic placode. As revealed by dlx-3 expression, the otic field in the mutant embryos is smaller or split into two fields. At later stages of development the ear of quadro mutants is frequently divided into two smaller, incomplete units. Four loci affect ear shape shortly after formation of the otic vesicle. All of them also display abnormal brain morphology. Mutations in five loci result in the absence of otolith formation; two of these also produce changes of ear morphology. Two loci, little richard and golas, affect morphology of the otic vesicle shortly before formation of the semicircular canals. In both cases the morphogenesis of the semicircular canals is disrupted. Finally, the antytalent locus is involved in late expansion of the ear structure. Analysis of mutations presented here will strengthen our understanding of vertebrate ear morphogenesis and provide novel entry points to its genetic analysis.

PMID: 9007247 [PubMed - indexed for MEDLINE]

70. Development. 1996 Dec;123:241-54.

Mutations affecting development of the zebrafish inner ear and lateral line.

Whitfield TT, Granato M, van Eeden FJ, Schach U, Brand M, Furutani-Seiki M, Haffter P, Hammerschmidt M, Heisenberg CP, Jiang YJ, Kane DA, Kelsh RN, Mullins MC, Odenthal J, Nüsslein-Volhard C.

ICRF Developmental Biology Unit, Department of Zoology, Oxford, UK. whitfiel@icrf.icnet.uk

Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996) Development 123, 1-36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996) Development, 123, 399-413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs.

PMID: 9007244 [PubMed - indexed for MEDLINE]

71. Int J Dev Biol. 1996 Oct;40(5):953-64.

Co-culture of contiguous developmental fields in a serumless, chemically-defined medium: an in vitro model permissive for coordinate development of the mouse ear.

Hoffman DS, Bringas P Jr, Slavkin HC.

Department of Otolaryngology, Head and Neck Surgery, University of Southern California School of Medicine, Los Angeles, USA.

Pattern formation is intrinsically hierarchical, increasing in complexity from the first early embryonic inductive tissue interactions to the eventual integration of multiple organ systems. Viewed as a problem in pattern formation, the vertebrate ear is an exceedingly complex organ system in which normal morphogenesis requires multiple inductive interactions between a variety of adjacent tissues. In order to model the process of higher level pattern formation, we have developed a method for organ culture of the embryonic murine ear. E10.5 mouse embryos (38 to 42 somite pairs) were microdissected into explants that consist of the first and second branchial arches, the otocyst, and the adjacent neural tube. The growth of these explants in a serumless, chemically-defined medium was compared to medium supplemented with 10% fetal calf serum. After 6 days in culture using serumless medium, we observed that this environment was permissive for the formation of pinnae, rudimentary semicircular canals and cochlear ducts, chondrogenesis of the otic capsule and elongation of the endolymphatic ducts. Posterior elements of Meckel's and Reichert's cartilages were identified as ossicular anlagen. All of these structures maintained appropriate anatomic interrelationships during in vitro development. Furthermore, no significant differences were observed in explants grown in serum-supplemented medium. We conclude that during ear development several histogenetic and morphogenetic processes, including aspects of higher level pattern formation, are mediated primarily by paracrine and/or autocrine factors. The development of an organ culture model using serumless medium should facilitate the discovery of intrinsic factors which regulate the coordinate development of inner, middle and external ear structures.

PMID: 8946243 [PubMed - indexed for MEDLINE]

72. AJNR Am J Neuroradiol. 1996 Sep;17(8):1467-77.

Imaging findings of the developing temporal bone in fetal specimens.

Nemzek WR, Brodie HA, Chong BW, Babcook CJ, Hecht ST, Salamat S, Ellis WG, Seibert JA.

Department of Radiology, University of California Davis Medical Center, Sacramento, USA.

PURPOSE: To trace the development of the normal fetal temporal bone by means of plain radiography, MR, and CT. METHODS: Eighteen formalin-fixed fetal specimens, 13.5 to 24.4 weeks' gestational age, were examined with a mammographic plain film technique, CT, and MR imaging at 1.5 T. Temporal bone development and ossification were assessed. RESULTS: The membranous labyrinth grows with amazing rapidity and attains adult size by the middle of the gestation period. The cochlea, vestibule, and semicircular canals are very prominent and easily recognized on MR images. The otic capsule develops from a cartilage model. Ossification of the otic capsule proceeds rapidly between 18 and 24 weeks from multiple ossification centers that replace the cartilaginous framework. The mastoid, internal auditory canal, vestibular aqueduct, and external auditory canal continue to grow after birth. CONCLUSION: The study of fetal developmental anatomy may lead to a better understanding of congenital disorders of the ear. Faster MR scanning techniques may provide a method for in utero evaluation of the fetal temporal bone.

PMID: 8883642 [PubMed - indexed for MEDLINE]

73. Development. 1996 Jun;122(6):1965-73.

Degeneration of vestibular neurons in late embryogenesis of both heterozygous and homozygous BDNF null mutant mice.

Bianchi LM, Conover JC, Fritzsch B, DeChiara T, Lindsay RM, Yancopoulos GD.

Regeneron Pharmaceuticals Inc., Tarrytown, NY 10591, USA.

The generation of mice lacking specific neurotrophins permits evaluation of the trophic requirements of particular neuronal populations throughout development. In the present study, we examined the developing vestibulocochlear system to determine the time course of neurotrophin dependence and to determine whether competition occurred among developing cochlear or vestibular neurons for available amounts of either brain-derived neurotrophic factor (BDNF) or neurotrophin-4/5 (NT-4/5). Both cochlear and vestibular neurons were present in mice lacking NT-4/5. In contrast, vestibular neurons decreased in number beginning at mid-stages of inner ear development, in mice lacking BDNF. Early in development (E12.5-13), the size of the vestibular ganglion was normal in bdnf -/- mice. Decreased innervation to vestibular sensory epithelia was detected at E13.5-15, when progressive loss of all afferent innervation to the semicircular canals and reduced innervation to the utricle and saccule were observed. At E16.5-17, there was a reduction in the number of vestibular neurons in bdnf -/- mice. A further decrease in vestibular neurons was observed at P1 and P15. Compared to bdnf -/- mice, mice heterozygous for the BDNF null mutation (bdnf +/-) showed an intermediate decrease in the number of vestibular neurons from E16.5-P15. These data indicate a late developmental requirement of vestibular neurons for BDNF and suggest competition among these neurons for limited supplies of this factor.

PMID: 8674435 [PubMed - indexed for MEDLINE]

74. J Anat. 1993 Dec;183 ( Pt 3):463-74.

Fine structure and development of ionocyte areas in the labyrinth of the trout (Salmo trutta fario).

Becerra M, Anadón R.

Department of Fundamental Biology, University of Santiago de Compostela, Spain.

The distribution of ionocyte areas in the trout labyrinth (in the semicircular canal ampullae, crus communis and utricular vesicle) is very similar to that of areas of dark cells in mammals. In all 3 regions, ionocytes begin to develop after hatching, and are cuboid at fry stages and prismatic in juveniles and adults. On electron microscopy, 3 types of cell can be seen in adult ionocyte areas: ionocytes, associate cells and basal cells. Ionocytes possess many mitochondria, occupying approximately 28% of the cytoplasmic volume, and a well-developed tubulomembranous system which opens on the basal surface at some points. These ultrastructural features, very similar to those of chloride cells, strongly suggest that ionocytes are involved in ion transport. Unlike mammalian dark cells, there are no basal or lateral infoldings of the plasma membrane in trout ionocytes. Trout associate cells have a well developed vacuolar system, few mitochondria and bundles of cytoplasmic filaments. Although less specialised than ionocytes, they may be involved in endolymph secretion.

PMCID: PMC1259873 PMID: 8300428 [PubMed - indexed for MEDLINE]

75. J Anat. 1992 Apr;180 ( Pt 2):247-53.

The structure and development of the 'plana semilunata' of the labyrinth of the trout.

Becerra M, Anadón R.

Department of Fundamental Biology, University of Santiago de Compostela, Spain.

Five plana semilunata consisting of tall epithelial cells were found in the semicircular canal ampullae of the trout labyrinth. All these areas began to develop after hatching. Their cells were cuboid at fry stages and prismatic in juveniles and adults. Cell outlines were smooth, with no basal infoldings of the plasma membrane or apical microvilli. The cell nucleus occupied basal locations in juveniles but migrated centrally in adults. The most conspicuous organelle, the smooth endoplasmic reticulum, was continuous with a well-developed vacuolar system. These cells stored numerous glycogen granules. The ultrastructural features of the plana semilunata strongly suggest their involvement in endolymph secretion.

PMCID: PMC1259670 PMID: 1506279 [PubMed - indexed for MEDLINE]

76. Development. 1991 Oct;113(2):455-70.

Expression of nerve growth factor (NGF) receptors in the developing inner ear of chick and rat.

von Bartheld CS, Patterson SL, Heuer JG, Wheeler EF, Bothwell M, Rubel EW.

Hearing Development Laboratories RL-30, University of Washington School of Medicine, Seattle 98195.

The expression of nerve growth factor receptors (NGFRs) was studied in the developing inner ear with in situ hybridization in chick embryos and with immunocytochemistry in rat embryos to determine sites of possible functions of NGF or NGF-like molecules in inner ear development. NGFR expression in the chick otocyst and acoustic ganglion is compared with epithelial differentiation and the onset of afferent innervation as determined with fluorescent carbocyanine tracers. In the inner ear of the chick embryo, NGFR mRNA expression shows an alternating pattern in mesenchymal and epithelial tissues. NGFR mRNA is heavily expressed in the mesenchyme surrounding the otocyst (E2-3), ceases at E3-5, and reappears in a thin layer of mesenchymal cells surrounding the membraneous epithelia (E5-13). In the otocyst epithelium, NGFR mRNA expression develops in one anterior and one posterior focus at E3-4.5. NGFR mRNA is expressed in the primordia of the ampullary cristae (E5-7) and possibly the anlage of the utricle; label transiently concentrates in the planum semilunatum of the cristae ampullares and in superior portions of the semicircular canals at E9, but is not seen in differentiating hair cells. In the acoustic ganglion, NGFR mRNA expression begins at E4; at the same time, the first peripheral acoustic nerve processes penetrate the otic epithelium (E4-4.5). The acoustic ganglia remain weakly NGFR mRNA-labeled in the posthatch animal. In the rat embryo, NGFR immunoreactivity is present in the auditory placode at E9, in the periotic mesenchyme at E9-10, and in the medial half of the otocyst at E10-11. At E12, epithelial NGFR expression becomes restricted anteriorly and posteriorly in a pattern similar to that of the chick otocyst and ceases at E13. NGFR immunoreactivity appears transiently in pillar cells of the cochlea in the third week of gestation. NGFR and NGFR mRNA is expressed after E11 in the acoustic ganglia. While NGFR transcripts are expressed in the cochlear ganglion cell bodies, NGFR protein becomes restricted to neuronal processes by the third week of gestation. The vestibular, but not the cochlear (spiral) ganglia remain NGFR-labeled in the adult rat. Onset of NGFR mRNA expression in the acoustic ganglion during the period of afferent fiber ingrowth into the otocyst epithelium is consistent with the hypothesis that NGF-like molecules may have a neurotrophic function for acoustic ganglion cells. Transient expression of NGFRs in secretory cells of the vestibular endorgan and pillar cells in the organ of Corti implicate a role for neurotrophins in the differentiation of these epithelial cell types.

PMID: 1664321 [PubMed - indexed for MEDLINE]

77. Development. 1991 Jun;112(2):541-50.

Hyaluronan as a propellant for epithelial movement: the development of semicircular canals in the inner ear of Xenopus.

Haddon CM, Lewis JH.

Imperial Cancer Research Fund, Department of Zoology, University of Oxford, UK.

The membranous labyrinth of the inner ear, with its three semicircular canals, originates from a simple spheroidal otic vesicle. The process is easily observed in Xenopus. The vesicle develops three dorsal outpocketings; from the two opposite faces of each outpocketing pillars of tissue are protruded into the lumen; and these paired 'axial protrusions' eventually meet and fuse, to form a column of tissue spanning the lumen of the outpocketing like the hub of a wheel, with a tube of epithelium forming the semicircular canal around the periphery. Each axial protrusion consists of epithelium encasing a core of largely cell-free extracellular matrix that stains strongly with alcian blue. In sections, at least 60% of the stainable material is removed by treatment with Streptomyces hyaluronidase. When Streptomyces hyaluronidase is microinjected into the core of a protrusion in vivo, the protrusion collapses and the corresponding semicircular canal fails to form. Hyaluronan (hyaluronic acid) in the core of the protrusion therefore seems to be essential in driving the extension of the protrusion. Autoradiography with tritiated glucosamine indicates that the hyaluronan-rich matrix is synthesised by the epithelium covering the tip of the protrusion; the basal lamina here appears to be discontinuous. These findings indicate that the epithelium of the axial protrusion propels itself into the lumen of the otocyst by localised synthesis of hyaluronan. Hyaluronan may be used in a similar way in the development of other organs, such as the heart and the secondary palate.

PMID: 1794322 [PubMed - indexed for MEDLINE]

78. J Neurosci. 1988 Aug;8(8):2836-43.

The induction and compensation of asymmetric eye movements following unilateral blockage of a horizontal semicircular canal in the rabbit.

Barmack NH, Pettorossi VE.

Department of Ophthalmology, Good Samaritan Hospital and Medical Center, Portland, Oregon 97209.

The influence of unilateral plugs of the left horizontal semicircular canal (LHC plugs) of rabbits on the development and compensation of asymmetric eye movements evoked by horizontal vestibular stimulation was studied. LHC plugs caused an immediate reduction of 50-65% in the gain of the horizontal vestibuloocular reflex (HVOR). This reduction in gain was achieved without altering the symmetry of the HVOR, and was accompanied by a change in the axial alignment of eye movements evoked by vestibular stimulation about the vertical (HVOR) and longitudinal (VVOR) axes. Postoperative asymmetry of eye movements developed 12-48 hr after the plugging operation. The development of asymmetry was reduced if the rabbit was restrained for 24 hr, thereby minimizing vestibular stimulation following the plugging operation. Over a 3-4 week period, the normal symmetry of eye movements was restored and the axial alignments of the HVOR and VVOR returned to the preoperative values. The gain of the HVOR did not recover. The horizontal cervicoocular reflex (HCOR) was examined before the plugging operation and after compensation of asymmetry was complete. The gain and phase of the HCOR were not altered. A relatively simple set of explanations at a cellular level is proposed to account for the induction and compensation of asymmetric eye movements following a unilateral plug of the horizontal semicircular canal.

PMID: 3411357 [PubMed - indexed for MEDLINE]

79. J Neurosci. 1985 Feb;5(2):317-29.

Directional asymmetries of optokinetic nystagmus: developmental changes and relation to the accessory optic system and to the vestibular system.

Wallman J, Velez J.

To investigate the relation of the directional organization of the accessory optic system (AOS) to that of its principal behavioral output, optokinetic nystagmus (OKN), we measured the eye velocity during OKN in response to 14 directions of stimulus motion, including horizontal, vertical, cyclorotational (rotations about the optic axis), and intermediate directions in both neonatal and older chickens. We found substantial and consistent OKN asymmetries between opposite directions of stimulus motion when the stimuli were viewed monocularly; the asymmetries were largest to combinations of cyclorotational and vertical stimulus motion and to horizontal stimulus motion. The highest gain of OKN in the older animals was in response to two directions of stimulus motion: horizontal temporal-to-nasal and a combination of excyclorotation and downward. In addition, OKN to upward moving stimuli was consistently better than to downward stimuli. The association of high OKN gain in the older animals with the pattern of visual motion produced by head movements exciting the contralateral anterior semicircular canal suggests a possible vestibular organization of the optokinetic system. The response pattern of the newly hatched chickens differed in three ways from that of the older animals: in the non-horizontal stimulus directions the best direction was to upward and excyclorotational stimulus motion; the horizontal asymmetry was somewhat less strong; and the OKN gain to high velocity horizontal stimulus motion was lower. The change in directional pattern of OKN over the first weeks of life appears related to a corresponding change in anatomy of the AOS.

PMID: 3871841 [PubMed - indexed for MEDLINE]

80. J Nutr. 1967 Apr;91(4):453-60.

Anomalous development of otoliths associated with postural defects in manganese-deficient guinea-pigs.

Shrader RE, Everson GJ.

PMID: 4227163 [PubMed - indexed for MEDLINE]