Talk:Integumentary System - Nail Development

2010

Incomplete development of the nail of the hallux in the newborn

Dermatol Online J. 2010 Jun 15;16(6):1.

Milano A, Cutrone M, Laforgia N, Bonifazi E.

Unit of Paediatric Dermatology, University of Bari, Bari, Italy. Abstract Between March and October 2008, the nails of 541 (252 females, 289 males) consecutively born neonates with an average age of 3.2 days were examined in the Neonatology Unit. Of these newborns with nail disorders, 36 were re-examined after a period that ranged from seven days to six months. The most frequent nail alteration was the incomplete development of the hallux nail, which was triangular - sometimes trapezoidal - shaped. This alteration, which had been previously reported in the literature as congenital hypertrophy of the lateral folds of the hallux, spontaneously regressed within one to three months in the infants re-examined. There was no associated inflammation or onychocryptosis at any time. The apparent hypertrophy of the nail folds seemed to be secondary to the lack of pressure of the nail lamina.

PMID: 20579456

http://www.ncbi.nlm.nih.gov/pubmed/20579456

http://dermatology.cdlib.org/1606/1_originals/1_10-00107/bonifazi.html

Dermatology Online Journal was created in an effort to explore the educational potential of distributed hypermedia served via the World Wide Web. The journal is attempting to serve the dual role of providing relevant information and improving the way scholarly content is shared. Dermatology Online Journal © The Regents of the University of California, Davis campus. Individual articles © by their authors. All material is available under the Creative Commons BY-NC-ND license. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License

2008

Lyonization pattern of normal human nails

Genes Cells. 2008 May;13(5):421-8.

Okada M, Nishimukai H, Okiura T, Sugino Y.

Department of Medical Technology, Ehime Prefectural University of Health Sciences, Tako-oda, Tobe, Ehime 791-2101, Japan. mokada@epu.ac.jp

Abstract

To examine the X-inactivation patterns of normal human nails, we performed the human androgen receptor gene assay of DNA samples extracted separately from each finger and toe nail plates of nine female volunteers. The X-inactivation pattern of each nail was unique and constant for at least 2 years. The frequency of nails with one of the two X-chromosomes exclusively inactivated was 25.9%. In the nails composed of two types of cells with either one X-chromosome inactivated, the two cell types were distributed in patchy mosaics. These findings suggest that the composition of precursor cells of each nail is maintained at each site at least through several cycles of regeneration time, and that the nail plate has a longitudinal band pattern, each band consisting of cells with only one of the two X-chromosomes inactivated. Using the frequency of nails with one of two X-chromosomes exclusively inactivated, we estimated the number of progenitor cells that gave rise to the nail plate during development to be about 3, under the assumption that the process follows the binominal distribution model. A strong correlation observed among the big, index and little fingers, and among the corresponding toes suggests an interesting interpretation concerning their morphogenetic process.

PMID: 18429815

2001

Development and evolution of the mammalian limb: adaptive diversification of nails, hooves, and claws

Evol Dev. 2001 Sep-Oct;3(5):355-63.

Hamrick MW.

Department of Anthropology & School of Biomedical Sciences, Kent State University, OH 44242, USA. mhamrick@kent.edu Abstract Paleontological evidence indicates that the evolutionary diversification of mammals early in the Cenozoic era was characterized by an adaptive radiation of distal limb structures. Likewise, neontological data show that morphological variation in distal limb integumentary appendages (e.g., nails, hooves, and claws) can be observed not only among distantly related mammalian taxa but also among closely related species within the same clade. Comparative analysis of nail, claw, and hoof morphogenesis reveals relatively subtle differences in mesenchymal and epithelial patterning underlying these adult differences in distal limb appendage morphology. Furthermore, studies of regulatory gene expression during vertebrate claw development demonstrate that many of the signaling molecules involved in patterning ectodermal derivatives such as teeth, hair, and feathers are also involved in organizing mammalian distal limb appendages. For example, Bmp4 signaling plays an important role during the recruitment of mesenchymal cells into the condensations forming the terminal phalanges, whereas Msx2 affects the length of nails and claws by suppressing proliferation of germinal epidermal cells. Evolutionary changes in the form of distal integumentary appendages may therefore result from changes in gene expression during formation of mesenchymal condensations (Bmp4, posterior Hox genes), induction of the claw fold and germinal matrix (shh), and/or proliferation of epidermal cells in the claw matrix (Msx1, Msx2). The prevalence of convergences and parallelisms in nail and claw structure among mammals underscores the existence of multiple morphogenetic pathways for evolutionary change in distal limb appendages.

PMID: 11710767 http://www.ncbi.nlm.nih.gov/pubmed/11710767