Talk:Oocyte Development

2010

Downregulation of both gene expression and activity of Hsp27 improved maturation of mouse oocyte in vitro

Liu JJ, Ma X, Cai LB, Cui YG, Liu JY. Reprod Biol Endocrinol. 2010 May 14;8:47.

BACKGROUND: Heat shock protein 27 (Hsp27), a member of the small heat shock protein family, is an apoptosis regulator. Our previous proteomic study showed that Hsp27 mainly expressed in human oocyte, and that Hsp27 expression was downregulated in the ovaries derived from women with the polycystic ovary syndrome (PCOS), a well known endocrinal disorder with abnormal apoptotic activity and folliculogenesis. However, the exact effects of Hsp27 downregulation on oocyte development have not yet been clarified.

CONCLUSIONS: Downregulation of Hsp27 improved the maturation of mouse oocytes, while increased early stage of apoptosis in oocytes by inducing the activation of extrinsic, caspase 8-mediated pathway.

PMID: 20465849

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890611/?tool=pubmed

http://www.rbej.com/content/8/1/47

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

(good annexin and cleaved caspase immunofluorecence images)

Three-dimensional in vitro follicle growth: overview of culture models, biomaterials, design parameters and future directions

Reprod Biol Endocrinol. 2010 Oct 14;8(1):119.

Desai N, Alex A, Abdelhafez F, Calabro A, Goldfarb J, Fleischman A, Falcone T.

Abstract ABSTRACT: In vitro ovarian follicle culture is a new frontier in assisted reproductive technology with tremendous potential, especially for fertility preservation. Folliculogenesis within the ovary is a complex process requiring interaction between somatic cell components and the oocyte. Conventional two-dimensional culture on tissue culture substrata impedes spherical growth and preservation of the spatial arrangements between oocyte and surrounding granulosa cells. Granulosa cell attachment and migration can leave the oocyte naked and unable to complete the maturation process. Recognition of the importance of spatial arrangements between cells has spurred research in to three-dimensional culture system. Such systems may be vital when dealing with human primordial follicles that may require as long as three months in culture. In the present work we review pertinent aspects of in vitro follicle maturation, with an emphasis on tissue-engineering solutions for maintaining the follicular unit during the culture interval. We focus primarily on presenting the various 3-dimensional culture systems that have been applied for in vitro maturation of follicle:oocyte complexes. We also try to present an overview of outcomes with various biomaterials and animal models and also the limitations of the existing systems.

PMID: 20946661

http://www.ncbi.nlm.nih.gov/pubmed/20946661 http://www.rbej.com/content/8/1/119/abstract

Loss of maternal ATRX results in centromere instability and aneuploidy in the mammalian oocyte and pre-implantation embryo

PLoS Genet. 2010 Sep 23;6(9). pii: e1001137.

Baumann C, Viveiros MM, De La Fuente R.

Female Germ Cell Biology Group, Department of Clinical Studies, University of Pennsylvania, Kennett Square, Pennsylvania, United States of America. Abstract

The α-thalassemia/mental retardation X-linked protein (ATRX) is a chromatin-remodeling factor known to regulate DNA methylation at repetitive sequences of the human genome. We have previously demonstrated that ATRX binds to pericentric heterochromatin domains in mouse oocytes at the metaphase II stage where it is involved in mediating chromosome alignment at the meiotic spindle. However, the role of ATRX in the functional differentiation of chromatin structure during meiosis is not known. To test ATRX function in the germ line, we developed an oocyte-specific transgenic RNAi knockdown mouse model. Our results demonstrate that ATRX is required for heterochromatin formation and maintenance of chromosome stability during meiosis. During prophase I arrest, ATRX is necessary to recruit the transcriptional regulator DAXX (death domain associated protein) to pericentric heterochromatin. At the metaphase II stage, transgenic ATRX-RNAi oocytes exhibit abnormal chromosome morphology associated with reduced phosphorylation of histone 3 at serine 10 as well as chromosome segregation defects leading to aneuploidy and severely reduced fertility. Notably, a large proportion of ATRX-depleted oocytes and 1-cell stage embryos exhibit chromosome fragments and centromeric DNA-containing micronuclei. Our results provide novel evidence indicating that ATRX is required for centromere stability and the epigenetic control of heterochromatin function during meiosis and the transition to the first mitosis.

PMID: 20885787

http://www.ncbi.nlm.nih.gov/pubmed/20885787

2009

Chromatin configurations in the germinal vesicle of mammalian oocytes

Mol Hum Reprod. 2009 Jan;15(1):1-9. Epub 2008 Nov 18.

Tan JH, Wang HL, Sun XS, Liu Y, Sui HS, Zhang J.

Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, Shandong Province 271018, Peolple's Republic of China. tanjh@sdau.edu.cn

Abstract In all the studied mammalian species, chromatin in the germinal vesicle (GV) is initially decondensed with the nucleolus not surrounded by heterochromatin (the NSN configuration). During oocyte growth, the GV chromatin condenses into perinucleolar rings (the SN configuration) or other corresponding configurations with or without the perinucleolar rings, depending on species. During oocyte maturation, the GV chromatin is synchronized in a less condensed state before germinal vesicle breakdown (GVBD) in species that has been minutely studied. Oocytes may also take on a SN/corresponding configuration during early atresia, but they undergo GVBD at the advanced stage of atresia. As not all the species show the SN configuration while in all the species, gene transcription always stops at the late stage of oocyte growth, it is suggested that not the formation of perinucleolar rings but a thorough condensation of GV chromatin is essential for transcriptional repression. The GV chromatin configuration is highly correlated with oocyte competence; oocytes must end the NSN configuration before they gain the full meiotic competence, and they must take on the SN/corresponding configurations and stop gene transcription before they acquire the competence for early embryonic development. While factors inhibiting follicle atresia tend to synchronize oocytes in a chromatin configuration toward maturation, factors inducing follicle atresia tend to synchronize oocytes in a chromatin configuration reminiscent of early atresia. Furthermore, although condensation of GV chromatin is associated with transcriptional repression, both processes may not be associated with histone deacetylation during oocyte growth.

PMID: 19019837 http://www.ncbi.nlm.nih.gov/pubmed/19019837

2007

Germline stem cells and neo-oogenesis in the adult human ovary

Dev Biol. 2007 Jun 1;306(1):112-20. Epub 2007 Mar 12. Liu Y, Wu C, Lyu Q, Yang D, Albertini DF, Keefe DL, Liu L.

College of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China. Abstract It remains unclear whether neo-oogenesis occurs in postnatal ovaries of mammals, based on studies in mice. We thought to test whether adult human ovaries contain germline stem cells (GSCs) and undergo neo-oogenesis. Rather than using genetic manipulation which is unethical in humans, we took the approach of analyzing the expression of meiotic marker genes and genes for germ cell proliferation, which are required for neo-oogenesis, in adult human ovaries covering an age range from 28 to 53 years old, compared to testis and fetal ovaries served as positive controls. We show that active meiosis, neo-oogenesis and GSCs are unlikely to exist in normal, adult, human ovaries. No early meiotic-specific or oogenesis-associated mRNAs for SPO11, PRDM9, SCP1, TERT and NOBOX were detectable in adult human ovaries using RT-PCR, compared to fetal ovary and adult testis controls. These findings are further corroborated by the absence of early meiocytes and proliferating germ cells in adult human ovarian cortex probed with markers for meiosis (SCP3), oogonium (OCT3/4, c-KIT), and cell cycle progression (Ki-67, PCNA), in contrast to fetal ovary controls. If postnatal oogenesis is confirmed in mice, then this species would represent an exception to the rule that neo-oogenesis does not occur in adults.

PMID: 17428461

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How eggs arrest at metaphase II: MPF stabilisation plus APC/C inhibition equals Cytostatic Factor http://www.celldiv.com/content/2/1/4

Balbiani body

• (Henneguy, 1887) is a cytoplasmic structure present in young immature oocytes in mammals and many other species
• transient structure composed of a large number of mitochondria, Golgi complexes, endoplasmic reticulum.
• ill-defined electron-dense granulofibrillar material that congregates at a perinuclear location
• as the oocyte matures it moves to a peripheral location in the oocyte cortex (in some species corresponding to the future vegetal pole) and disperses (reviewed by Kloc et al., 2004).

Function

• in some species contribute to the assembly and transportation of the germ plasm determinants to the cortex of the mature oocyte
• In mammals ( “inductive”, “regulative” or “epigenetic” mode of germ cell formation) do not have germ plasm determinants, the function remains largely obscure may include
  • the controlled amplification of mitochondria or the creation of an asymmetry or polarity in the oocyte.

Reference: http://www.hh.um.es/pdf/Vol_25/25_2/de-Sousa-Lopes-25-267-276-2010.pdf

Henneguy F. (1887). Note sur la vesicle de Balbiani. C. R. Hebd. Seances Soc. Biol. Ses. Fil. 39, 69.

Kloc M., Bilinski S. and Etkin L.D. (2004). The Balbiani body and germ cell determinants: 150 years later. Curr. Top. Dev. Biol. 59, 1-36.

References

Egg coat proteins activate calcium entry into mouse sperm via CATSPER channels

Xia J, Ren D. Biol Reprod. 2009 Jun;80(6):1092-8. Epub 2009 Feb 11. PMID: 19211808

ZP2 and ZP3 traffic independently within oocytes prior to assembly into the extracellular zona pellucida

Hoodbhoy T, Avilés M, Baibakov B, Epifano O, Jiménez-Movilla M, Gauthier L, Dean J. Mol Cell Biol. 2006 Nov;26(21):7991-8. PMID: 17047254