FGFR2 and hypospadias: Loss-of-function mutations or deletions of Fgfr2 in the ectoderm result in the most severe hypospadias; the Fgfr2 mutant mice exhibit an open urethra [3,16,48], and the morphology of the developing GT looks similar to that of guinea pig [3] and human [44] GTs at the proximal-open stage, while the distal remains closed (Figure 9A,B,E).