CYP17A1 and polycystic ovary syndrome: DENND1A variant 2 (DENND1A.V2), a truncated splice isoform of DENND1A with a unique C-terminal sequence, is up-regulated in PCOS theca cells, and compelled expression of V2 in normal theca cells results in increased expression of genes encoding cytochrome P450 isoforms (CYP17A1 and CYP11A1) and higher androgen production (81, 82).