Effect of the transient pharmacological inhibition of Mapk3/1 pathway on ovulation in mice.
Authors: Siddappa Dayananda, Beaulieu Élaine, Gévry Nicolas, Roux Philippe P, Bordignon Vilceu, Duggavathi Raj
Journal: PloS one
Summary
# Editorial Summary: MAPK3/1 Signalling and Ovulation in Mice The luteinising hormone (LH) surge triggers a complex cascade of molecular events within ovarian follicles, but the precise transcriptional mechanisms governing gene expression during ovulation remain incompletely characterised. Dayananda and colleagues used superovulated mice treated with the MAPK3/1 inhibitor PD0325901 to investigate whether this signalling pathway controls ovulation through regulation of ovulation-associated genes, combining pharmacological inhibition with granulosa cell gene expression analysis, chromatin immunoprecipitation, and RNA interference techniques. Complete blockade of MAPK3/1 phosphorylation in granulosa cells prevented ovulation entirely, whilst vehicle-treated controls ovulated normally; inhibitor-treated mice showed significantly reduced mRNA abundance of multiple LH-responsive genes including prostaglandin-endoperoxide synthase 2 (Ptgs2), alongside diminished expression of the transcription factor early growth response 1 (Egr1). Through chromatin immunoprecipitation and siRNA knockdown experiments, the authors established that Egr1 directly binds the Ptgs2 promoter and that reducing Egr1 expression suppresses Ptgs2 transcription, demonstrating a critical mechanistic link between MAPK3/1 signalling, Egr1 activation, and prostaglandin synthesis. Whilst these findings are rodent-based, understanding the MAPK3/1–Egr1–Ptgs2 axis may ultimately inform strategies in equine reproduction, particularly regarding ovulation synchronisation or induction protocols where prostaglandin physiology is central to follicular rupture and oocyte release.
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Practical Takeaways
- •This fundamental research on ovulation mechanisms in mice has limited direct application to equine practice, but contributes to understanding reproductive endocrinology
- •Knowledge of the MAPK3/1 signaling pathway and its role in gonadotropin responsiveness may inform future therapeutic approaches to reproductive disorders
- •While conducted in mice, the conserved nature of ovulatory signaling pathways suggests relevance to understanding reproductive function across species
Key Findings
- •Pharmacological inhibition of MAPK3/1 pathway with PD0325901 completely abolished ovulation in superovulated mice
- •MAPK3/1 inhibition prevented hCG-driven upregulation of Ptgs2 and other ovulation-related genes in granulosa cells
- •Transcription factor Egr1 was identified as a downstream target of MAPK3/1 that directly binds to the Ptgs2 promoter
- •Knockdown of Egr1 expression in primary granulosa cells reduced Ptgs2 expression, confirming the MAPK3/1-Egr1-Ptgs2 signaling cascade