MAP3K5 and polycystic ovary syndrome: Key up- and downregulated DEGs in PCOS in stroma 1 and stroma 2, which were not differentially expressed in any other subpopulation, included PIK3C2G (downregulated), a gene associated with granulosa cell tumor29, MAP3K5 (upregulated), a marker of human endometrial receptivity30, and the collagen gene COL7A1 (upregulated), a component of the basement membrane and surrounding vasculature that plays an important role in regulating tissue remodeling and homeostasis31 (Fig. 3e and Supplementary Table 2a–c).