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). Here, CD9 is linked to polycystic ovary syndrome.