ESR1 and polycystic ovary syndrome: When classified into biological function, these three miRNAs were enriched for several pathways known to be crucial in the process of oocyte development and maturation such as TGF-beta signaling pathway, MAPK signaling pathway, estrogen signaling pathway and oocyte maturation, etc. The functional annotation of differentially expressed miRNAs in our study was in agreement with other studies that have found that defects in the TGF-beta and estrogen receptors signalling cascades may contribute to the reduced oocyte developmental competence in PCOS [18, 26].