Numbers of bivalent promoters decline as expression becomes sexually dimorphic.

(A) An overview of sex determination and work flow. Briefly, supporting progenitor cells (yellow) are bipotential and indistinguishable between XX and XY gonads. Expression of Sry directs Sertoli cell differentiation in the testis through upregulation of testis-determining genes such as Sox9, Fgf9 and Dmrt1. Absence of Sry leads to upregulation of ovary-determining genes Wnt4, Rspo1, and Foxl2, directing differentiation of pregranulosa cells in the ovary. XY and XX progenitor cells, Sertoli cells, and pregranulosa cells were FACS-purified and submitted to ChIP-seq for H3, H3K4me3 and H3K27me3. Further analysis made use of microarray expression data from E10.5 and E13.5 purified supporting cells [41]. (B-C and E-F) Venn diagrams depicting number of promoters marked by H3K27me3 (red) and H3K4me3 (green) in XX and XY supporting cells at E10.5 (B&C) and E13.5 (E&F). (D&G) Linear correlation between expression profiles of XY (y axis) and XX (x axis) progenitor cells at E10.5 (D), and at E13.5 (G) (expression profiles from [41]).