Cellular Signaling Mechanisms in Oocyte Maturation

During mammalian oocyte maturation, a finely tuned interplay between somatic signals from surrounding granulosa cells and intrinsic oocyte pathways governs the transition from meiotic arrest to fertilisation readiness. High intra-oocyte concentrations of cyclic nucleotides, particularly cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), maintain arrest at prophase I by inhibiting the maturation-promoting factor (MPF). The preovulatory surge of luteinising hormone (LH) elicits a cascade in cumulus and mural granulosa cells, resulting in reduced gap junction permeability, diminished cGMP transfer to the oocyte and activation of MPF. Key mediators include epidermal growth factor (EGF)-like ligands such as amphiregulin and epiregulin, which bind to the epidermal growth factor receptor (EGFR) on cumulus cells and engage MAPK/ERK, PI3K–AKT and PKC pathways to drive cumulus expansion, germinal vesicle breakdown (GVBD), chromatin remodelling and cytoplasmic maturation. Concurrent post-translational histone modifications and selective degradation of maternal mRNAs further refine oocyte competence. Emerging studies highlight chemokine receptors as intermediates in the ovulatory cascade and detailed temporal control of connexin 43 phosphorylation to fine-tune gap junction intercellular communication (GJIC). This integrative signalling network synchronises nuclear and cytoplasmic events, safeguarding oocyte quality, fertilisation potential and subsequent embryonic development.

Research from Nature Portfolio

Recent studies have elucidated the role of histone deacetylase 3 in maintaining meiotic arrest by repressing transcription of EGF-like growth factors in preovulatory granulosa cells. LH-induced downregulation of this deacetylase permits histone H3K14 acetylation and rapid induction of amphiregulin, triggering oocyte maturation independent of further hormonal input. Another investigation has defined a somatic-cell autonomous mechanism for germ-soma uncoupling at ovulation: EGFR activation in granulosa cells provokes ERK-dependent calpain activation and Arp2/3-mediated filopodial retraction, physically releasing the oocyte from its supportive niche. Both findings underscore how precise temporal control of chromatin state and cytoskeletal dynamics in the follicular soma governs the oocyte’s transition towards fertilisation readiness.

Cellular Signaling Mechanisms in Oocyte Maturation publication trend

The graph below shows the total number of articles in cellular signaling mechanisms in oocyte maturation across all publications each year (not limited to Nature Index journals).

Technical terms

Luteinising hormone (LH): A pituitary gonadotrophin that triggers ovulation and meiotic resumption in oocytes.

Cyclic adenosine monophosphate (cAMP): A second messenger within oocytes that maintains meiotic arrest by inhibiting MPF activity.

Maturation-promoting factor (MPF): A cyclin-dependent kinase complex that drives the oocyte through meiotic divisions.

Gap junction intercellular communication (GJIC): Direct cytoplasmic connections between oocyte and cumulus cells mediated by connexins.

Germinal vesicle breakdown (GVBD): The first visible sign of oocyte meiotic resumption marked by dissolution of the nuclear envelope.

Connexin 43 (Cx43): A gap junction protein in granulosa cells whose phosphorylation state regulates intercellular communication.

References

1. The molecular regulatory mechanisms of meiotic arrest and resumption in Oocyte development and maturation. Reproductive Biology and Endocrinology (2023).
2. Application of amphiregulin in IVM culture of immature human oocytes and pre-insemination culture for COCs in IVF cycles. Frontiers in Endocrinology (2024).
3. Interaction between epidermal growth factor receptor and C-C motif chemokine receptor 2 in the ovulatory cascade. Frontiers in Cell and Developmental Biology (2023).
4. Betacellulin regulates gap junction intercellular communication by inducing the phosphorylation of connexin 43 in human granulosa-lutein cells. Journal of Ovarian Research (2023).
5. Mechanisms of Oocyte Maturation and Related Epigenetic Regulation. Frontiers in Cell and Developmental Biology (2021).
6. HDAC3 maintains oocyte meiosis arrest by repressing amphiregulin expression before the LH surge. Nature Communications (2019).
7. Epidermal growth factor receptor signaling uncouples germ cells from the somatic follicular compartment at ovulation. Nature Communications (2021).