RUNX2 and polycystic ovary syndrome: On one hand, during folliculogenesis, E2F1/SF-1 mediated miR-320-induced suppression of GC proliferation and of GC steroidogenesis; On the other hand, in PCOS patients, miR-320 decreases in GC and this down-regulation is thought to cause relative estrogen deficiency via targeting RUNX2, implying the potential therapeutic role of this miRNA in PCOS by regulating steroidogenesis.