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    The fine structure of human oogonia in foetal ovaries and the stages of folliculogenesis in fertile ovaries are documented with digital images. The human oogonia show progressive changes in fine structure during folliculogenesis and oogenesis until they are ovulated and ready for fertilization. Parallel changes also occur in their relationship with the surrounding follicle cells, which support and nurse the growing and maturing oocytes untill ovulation. The inactivation of the maternal centrosome is the most significant event during human oogenesis
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    We previously discovered a germ cell-specific spermatogenesis and oogenesis basic helix-loop-helix transcription factor, Sohlh2. We generated Sohlh2-deficient mice to understand physiologic consequences of Sohlh2 deletion. We discovered that Sohlh2-knockout adult female mice are infertile due to lack of ovarian follicles. Sohlh2-deficient ovaries can form primordial follicles and, despite limited oocyte growth, do not differentiate surrounding granulosa cells into cuboidal and multilayered structures. Oocytes are rapidly lost in Sohlh2-deficient ovaries, and few are present by 14 days of postnatal life. However, the primordial oocytes are abnormal at the molecular level because they misexpress numerous germ cell- and oocyte-specific genes, including Sohlh1, Nobox, Figla, Gdf9, Pou5f1, Zp1, Zp3, Kit, Oosp1, Nlrp14, H1foo, and Stra8. Our findings show that Sohlh2 is a critical factor for maintenance and differentiation of the oocyte during early oogenesis.
    In perinatal mice, the ovary undergoes drastic morphological changes, as clusters of oocytes called nests break into smaller cysts and subsequently form individual follicles. We studied perinatal oocyte development in MRL/MpJ mice, and compared it to that observed in C57BL/6 mice between embryonic day 18.5 and postnatal day 4. Throughout the observation period, compared to C57BL/6 mice, MRL/MpJ mice displayed significantly fewer oocytes in their ovaries. Morphologically, there were no clear differences between the strains at embryonic day 18.5. However, the beginning of folliculogenesis, as evidenced by the expression of NOBOX oogenesis homeobox (Nobox) transcript and protein, was more enhanced in MRL/MpJ mice than in C57BL/6 mice at embryonic day 18.5 and postnatal day 0. In addition, developed follicles were more frequently observed in MRL/MpJ mice than in C57BL/6 mice between postnatal days 0 and 4. In conclusion, the oocyte development during nest breakdown and folliculogenesis was accelerated in MRL/MpJ mice when compared to that observed in C57BL/6 mice.
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    The stage of folliculogenesis at which the human zona pellucida (ZP) is initiated and the cells responsible for the origin of the ZP continue to be controversial. This study characterizes the development of the ZP during human folliculogenesis using ovarian samples donated from patients requesting ovarian storage.Follicles (from n = 18 patients, 14-40 years old) within fresh tissue and following development in a xenograft system were stained, using immunohistochemical techniques, for the presence of the three human ZP proteins, ZP1, ZP2 and ZP3. Over 500 primordial follicles and >20 follicles at each developmental stage were examined.All three ZP proteins were detected within the oocyte of the primordial follicle. Presence of ZP1 and ZP3 was observed in the majority of primordial oocytes (93% and 95%, respectively), whereas ZP2 was detected in only 32% of these follicles. The three ZP proteins were detected in the cytoplasm of cuboidal granulosa cells and their distribution correlates with developmental stages throughout folliculogenesis.ZP proteins were detected in both the oocyte and the granulosa cells as early as the primordial follicle stage in the human. The detection of ZP proteins in the quiescent primordial follicle suggests that these proteins have been present since oogenesis.
    Zona pellucida glycoprotein
    Citations (71)
    Mammalian folliculogenesis and oogenesis research is an important part of the developmental biology.In this paper,the progression of mammalian folliculogenesis and oogenesis,many key genes such as gdf9,c-kit,BMP4 and TGF involved in the cellular differentiation proceeding from primordial germ cells to oocytes,the interrelationship between oocyte and granulose cells within the growing follicles,the advance of mammalian oogenesis in vitro were reviewed.Molecular regulation processes of oogenesis provide a clue to mechanism of mammalian oogenesis from primordial germ cells to oocytes.
    Growth differentiation factor-9
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