Apoptosis and Meiotic Regulation in Mammalian Oocytes

Oocyte development in mammals is governed by a delicate balance between survival signals and programmed cell death pathways. Meiotic progression is halted at discrete checkpoints—most notably at metaphase II—until the arrival of fertilising sperm or appropriate activation stimuli. This arrest is maintained by cytostatic factors that inhibit the anaphase-promoting complex/Cyclosome (APC/C), preserving Maturation-Promoting Factor (MPF) activity. Should this regulatory network fail or should intrinsic damage accumulate, apoptotic programmes are triggered, eliminating defective oocytes through caspase activation, mitochondrial cytochrome c release and DNA fragmentation. Granulosa cells provide critical support, supplying nutrients, growth factors and paracrine cues such as acetylcholine, while also modulating oxidative stress. Dysregulation of either meiotic arrest or apoptotic clearance underlies diminished ovarian reserve, follicular atresia and age-related fertility decline. Understanding these processes informs assisted reproductive technologies, fertility preservation and the management of reproductive ageing across species.

Research from Nature Portfolio

Recent studies have illuminated non-apoptotic cell-death pathways in primate follicles. In macaque organotypic culture, enhancing intra-follicular acetylcholine levels by blocking acetylcholinesterase, or inhibiting necroptosis with specific kinase blockers, did not alter overall follicle survival but promoted the transition from secondary to small antral stages. This work identifies regulated necrosis as a complementary determinant of oocyte competence and suggests that fine-tuning cholinergic signalling alongside necroptosis inhibition could improve follicular growth and oocyte quality in primates.

Apoptosis and Meiotic Regulation in Mammalian Oocytes publication trend

The graph below shows the total number of articles in apoptosis and meiotic regulation in mammalian oocytes across all publications each year (not limited to Nature Index journals).

Technical terms

Apoptosis: Programmed cell-death mechanism characterised by caspase activation, DNA fragmentation and membrane blebbing.

Meiotic arrest: Suspension of oocyte cell cycle at metaphase I or II, maintained by cytostatic factors and high MPF activity until fertilisation or activation.

Granulosa cell: Somatic ovarian cell that surrounds the oocyte, providing metabolic support, paracrine signals and structural integrity.

Anaphase-Promoting Complex/Cyclosome (APC/C): Ubiquitin ligase that targets cyclin B for degradation, enabling anaphase onset and exit from meiotic arrest.

Emi2: Egg-specific inhibitor of the APC/C that stabilises MPF and enforces metaphase II arrest until calcium-triggered degradation after fertilisation.

References

1. How eggs arrest at metaphase II: MPF stabilisation plus APC/C inhibition equals Cytostatic Factor. Cell Division (2007).
2. Acetylcholine and necroptosis are players in follicular development in primates. Scientific Reports (2018).
3. Honghua Xiaoyao tablet combined with estradiol improves ovarian function in D-galactose-induced aging mice by reducing apoptosis and affecting the release of reproductive hormones: an in vivo study. Frontiers in Pharmacology (2024).
4. The C-terminal domain of Emi2 conjugated to cell-penetrating peptide activates mouse oocyte. Frontiers in Cell and Developmental Biology (2025).
5. Oocyte Spontaneous Activation: An Overlooked Cellular Event That Impairs Female Fertility in Mammals. Frontiers in Cell and Developmental Biology (2021).