ELK1 regulates BMPR1B transcriptional activity in ovine granulosa cells.

BMPR1B, a type I receptor in the BMP/Smad signaling pathway, was the first major gene identified in sheep (Ovis aries) to regulate key reproductive traits such as ovulation rate (OR) and litter size (LS). Despite its critical role in reproductive performance, the transcriptional regulatory mechanisms governing ovine BMPR1B expression remain poorly understood. This study identified the promoter region of the BMPR1B gene and revealed that transcription factor ELK1 regulates its transcriptional activity. Luciferase reporter assays identified the region from -438 bp to -208 bp relative to the essential promoter of the BMPR1B gene as a critical regulatory element. Notably, candidate ELK1-binding elements (EBS) were detected in this promoter region. Interestingly, ELK1 significantly enhances BMPR1B transcriptional activity by binding to specific sites in the promoter region. Further analysis in ovine granulosa cells showed that ELK1 modulates BMPR1B expression and influences granulosa cell apoptosis through the BMPR1B signaling pathway. These findings provide new key targets and mechanistic insights into the molecular regulatory network of ovarin granulosa cell apoptosis, advancing our understanding of reproductive biology in sheep.