Blunted Lsm14b activation disrupts maternal mRNA remodeling during the GV-to-MII transition in a mouse model of polycystic ovary syndrome.

INTRODUCTION

Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility and is consistently associated with poor oocyte developmental competence, yet the molecular basis of this qualitative defect remains poorly defined. Because the germinal vesicle (GV)-to-metaphase II (MII) transition occurs under global transcriptional silence and depends entirely on the post-transcriptional remodeling of pre-stored maternal mRNAs, we hypothesized that PCOS may selectively disrupt this regulatory program rather than impose a constitutive transcriptomic lesion.

METHODS

To test this, we established a DHEA-induced PCOS mouse model, validated by estrous acyclicity, hyperandrogenism, and polycystic ovarian morphology, and performed parallel Smart-seq2 profiling of oocytes at both the GV and MII stages. Integrated analyses combining differential expression, maturation trajectory modeling, weighted gene co-expression network analysis (WGCNA), and protein-protein interaction mapping, together with independent RT-qPCR validation of four hub transcripts, were used to dissect stage-specific transcriptomic dynamics.

RESULTS

Control and PCOS oocytes were largely similar at the single-gene level at the GV stage (35 differentially expressed genes), with subtle network-level perturbations detectable only by co-expression analysis, but diverged dramatically upon meiotic maturation (292 differentially expressed genes), with the majority of dynamic transcripts diverted into pathological trajectories. This maturation-coupled collapse manifested as a dual-layered post-transcriptional failure: aberrant retention of maternal mitochondrial OXPHOS transcripts (Sdhb, Cox6a1) reflecting impaired mRNA clearance, and concurrent hyper-depletion of oocyte identity genes (Figla, Zp3). Mechanistically, Lsm14b, an essential P-body assembly factor, failed to execute its physiological upregulation during the GV-to-MII transition in PCOS oocytes (1.49-fold induction in PCOS versus 9.63-fold in controls; an ∼6.5-fold reduction), providing a proximal explanation for the global decay-machinery failure. RT-qPCR independently confirmed stage-specific dysregulation, including ∼34-fold excessive depletion of Figla exclusively at the MII stage. Western blot analysis of Lsm14b, Sdhb, and Figla proteins in GV and MII oocytes confirmed that all three key transcriptomic findings are recapitulated at the protein level, establishing that the mRNA-level dysregulation has functional consequences for protein output.

DISCUSSION: These findings reframe PCOS-associatedoocyte dysfunction as a stage-specific failure of post-transcriptional remodeling competence and identify the Lsm14b-P-body axis as a candidate molecular target for improving oocyte quality in assisted reproduction.