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Updated: Jul 17, 2026
Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary
Published on: June 19, 2018
Switch from BAX-dependent to BAX-independent germ cell loss during the development of fetal mouse ovaries
Michelle Alton1, Teruko Taketo
1Department of Biology, McGill University, Montreal, Quebec, H3A 1A1, Canada.
Abstract:
Female reproductive life is limited by the oocyte/follicle pool, which has been determined by the number of germ cells to enter meiosis and subsequent loss of oocytes. It has been suggested that apoptosis accounts for the elimination of germ cells throughout oogenesis. However, female germ cells are lost continuously while they undergo distinct cell cycles in fetal and neonatal life. No convincing evidence has yet been provided to show apoptotic death of oocytes during meiotic prophase in vivo. In this study, we examined the change in the germ cell population in mice deficient of BAX, a key proapoptotic molecule. The number of germ cells, identified by GCNA1 immunolabeling, approximately doubled in ovaries of Bax(-/-) mice compared with ovaries of heterozygous Bax(+/-) mice and wild-type Bax(+/+) mice by 14.5 days post coitum (d.p.c.) and remained higher up to 24.5 d.p.c. However, there was a rapid loss of germ cells in Bax(-/-) ovaries, paralleling that in Bax(+/-) and Bax(+/+) ovaries from 14.5-24.5 d.p.c., a period in which most germ cells entered and progressed in meiotic prophase. These results suggest that, while progressing through meiotic prophase, oocytes are eliminated by a BAX-independent mechanism.
Insights
Female germ cell loss during oogenesis occurs independently of the BAX protein, a key molecule in apoptosis. This suggests a BAX-independent mechanism eliminates oocytes during meiotic prophase.
Area of Science:
- Reproductive biology
- Developmental biology
- Cell biology
Background:
- Female reproductive lifespan is determined by the finite oocyte/follicle pool.
- Oocyte loss throughout oogenesis is critical, with apoptosis previously suggested as a primary elimination mechanism.
- Evidence for oocyte apoptosis during meiotic prophase in vivo remains limited.
Purpose of the Study:
- To investigate the role of BAX, a proapoptotic molecule, in female germ cell elimination during oogenesis.
- To determine if BAX-dependent apoptosis accounts for oocyte loss during meiotic prophase.
Main Methods:
- Analysis of germ cell populations in ovaries of mice deficient in BAX (Bax(-/-)) compared to heterozygous (Bax(+/-)) and wild-type (Bax(+/+)) mice.
- Germ cells were identified using GCNA1 immunolabeling at various stages of fetal and neonatal development (up to 24.5 days post coitum).
Main Results:
- Ovary germ cell numbers were approximately doubled in Bax(-/-) mice by 14.5 days post coitum compared to controls.
- Despite initial higher numbers, germ cell loss in Bax(-/-) ovaries paralleled that in control ovaries from 14.5 to 24.5 days post coitum.
- This period corresponds to the entry and progression of most germ cells into meiotic prophase.
Conclusions:
- Oocyte elimination during meiotic prophase proceeds via a BAX-independent mechanism.
- Apoptosis mediated by BAX does not appear to be the primary driver of germ cell loss during this critical developmental stage.
