A) Overview of sex determination and work flow. Briefly, supporting progenitor cells (yellow) are bipotential and indistinguishable between XX and XY gonads at E10.5. Expression of the Y-linked Sry gene (at E11.5) directs Sertoli cell differentiation in the testis (XY, blue). Absence of Sry directs differentiation of granulosa cells in the ovary (XX, pink). XX and XY progenitor cells (E10.5), Sertoli cells (E13.5), and granulosa cells (E13.5) were FACS-purified and used for ATAC-seq and ChIP-seq for H3K27ac. Further analysis made use of microarray expression data from purified supporting cells (Jameson et al., 2012b). B) Percent (and number) of H3K27ac-negative (grey) and H3K27ac-postive (green) NDRs in XX and XY cells at E10.5 (left) and E13.5 (right). C) Venn diagrams of all NDRs in XX (pink) and XY (blue) supporting cells at E10.5 (left) and E13.5 (right). D) Percent of NDRs that are shared between XX and XY cells at E10.5 (purple) and at E13.5 (orange), or specific to either XX or XY cells at E10.5 (black) or at E13.5 (grey). The purple and black bars at E13.5 represent NDRs that were retained from E10.5, while the orange and grey represent newly acquired NDRs.