Indeed, several genes regulating sex development have been shown to exert a dose-dependent effect such as duplications of FGF9, SOX3 or SOX9 in 46,XX DSD and of DAX1 or WNT4 in 46,XY DSD as well as deletions of ATRX, DMRT1, EMX2 or WT1 in 46,XY DSD (Table 1). This evidence concerns the gene FGF9 and disorder of sexual differentiation.