NOTCH2 and polycystic ovary syndrome: To determine whether ER stress, which is activated in granulosa cells of antral follicles in PCOS, is associated with induction of Notch2 signaling in these cells, we measured the mRNA expression levels of Notch2 and Hey2 following treatment with an ER stress inducer, tunicamycin or thapsigargin, in cultured human GLCs.