Granulosa cell mevalonate pathway abnormalities contribute to oocyte meiotic defects and aneuploidy [HiC GGOH-treatment]

The mechanisms of aging-related oocyte aneuploidy remain elusive. Hi-C and SMART-seq revealed aging-related decreases in chromosome condensation, particularly for genomic regions proximal to the centromeres, accompanied with disrupted meiosis-associated gene expression in metaphase I (MI) aged oocytes. Further transcriptomic analysis showed that oocyte meiotic maturation was correlated with robust increases in mevalonate (MVA) pathway gene expression in young oocyte-surrounding granulosa cells (GCs), which was largely downregulated in aged GCs. Inhibtion of MVA metabolism in GCs by statins resulted in marked meiotic defects and aneuploidy in young cumulus-oocyte complexes (COCs). Conversely, supplementation with the MVA isoprenoid geranylgeraniol ameliorated meiotic defects and aneuploidy in aged COCs. Meanwhile, geranylgeraniol also activated LHR/EGF signaling in aged GCs and then enhanced the meiosis-associated gene expression in oocytes. Generally, the MVA pathway in GCs is a critical regulator of meiotic maturation and euploidy in oocytes. In this study, the dynamics of chromatin structure of oocytes and the overall transcriptomic landscape of oocytes and GCs throughout oocyte meiosis (growing phase, full-grown phase, metaphase I phase, metaphase II phase) in vivo from control or GGOH-treated aged mice were depicted.