SPP1 and polycystic ovary syndrome: We then investigated the methylation level of each CpG site or cluster in the promoters of the other 13 DEGs verified by qPCR (ANGPTL4, CD9, NR4A1, EDN2, PTX3, LIF, SLC12A8, PEX3, CYP17A1, SERPINE1, DIRAS3, BNIP3, SPP1) in 16 GC DNA samples (8 PCOS women and 8 controls, the first cohort).