Loss of Fgfr2 leads to partial XY sex reversal.

In mammals, sex is determined in the bipotential embryonic gonad by a balanced network of gene actions which when altered causes disorders of sexual development (DSD, formerly known as intersex). In the XY gonad, presumptive Sertoli cells begin to differentiate when SRY up-regulates SOX9, which in turn activates FGF9 and PGDS to maintain its own expression. This study identifies a new and essential component of FGF signaling in sex determination.