Developmental and sexual dimorphic atlas of the prenatal mouse external genitalia at the single cell level

Before the onset of sexual differentiation, male and female external genitalia are morphologically indistinguishable. After the onset of sex-specific production of sex steroids by the gonads, the male and female external genitalia differentiate into either a penis or clitoris. Here we use single cell sequencing to investigate the similarities and differences of cell populations in the external genitalia during the critical sexual differentiation window in the mouse embryo. We found the male and female genitalia are largely similar in cell composition and gene expression at the bipotential stage of development. As sexual differentiation ensues, sex steroid-dependent and -independent differences in cell populations arise, leading to dimorphic establishment of the external genitalia. Male and Female External Genitalia at stages E14.5, E16.5, and E18.5