LSD1 maintains oocyte quality by epigenetically repressing CAMK2β to control granulosa cell-oocyte communication.

BACKGROUND: Poor ovarian response (POR) is a major challenge in assisted reproduction, yet its molecular basis remains poorly understood. Communication between granulosa cells (GCs) and oocytes is critical for folliculogenesis, but how it is regulated epigenetically is unclear. METHODS: We generated granulosa cell-specific Lsd1 knockout mice. Human GCs from POR patients (classified by Poseidon criteria) and controls were analyzed. Mechanistic studies employed RNA-seq, ChIP-seq, TEM, calcium imaging, and actin polymerization assays. LSD1 was knocked out in KGN cells via CRISPR/Cas9. RESULTS: LSD1 was significantly downregulated in GCs of POR patients. Its loss in mice recapitulated the POR phenotype: reduced fertility, low estrogen levels, impaired antral follicle formation, poor response to gonadotropins, and defective oocytes with meiotic and spindle abnormalities. Mechanistically, Lsd1 deficiency increased H3K4me2 enrichment at the Camk2β promoter, elevating CAMK2β expression. This led to elevated cytoplasmic Ca(2+), enhanced F-actin binding, aberrant transzonal projections (TZPs) formation, and disrupted GC-oocyte communication. CellChat analysis confirmed altered signaling between GCs and oocytes. Restoring calcium homeostasis (with BAPTA-AM) or inhibiting CAMK2β (with API) rescued antral follicle formation and oocyte maturation. CONCLUSIONS: Our findings reveal that GC LSD1 epigenetically represses Camk2β to maintain calcium signaling, actin dynamics, and TZPs integrity, thereby ensuring functional GC-oocyte communication and oocyte competence. Downregulation of LSD1 and upregulation of CAMK2β in GCs is a hallmark of POR, identifying this pathway as a potential diagnostic biomarker and therapeutic target. CAMK2β inhibition represents a promising strategy for treating ovarian dysfunction.