GDNF and Fraser syndrome: Because such mutated Fraser syndrome-related genes encode proteins that functionally converge on the glial cell-derived neutotrophic factor (GDNF)-RET/BMP signaling pathways at the interface of the ureteric bud and metanephric mesenchyme [1], these results also supported our hypothesis that alterations in the BMP/SMAD signaling pathway may cause renal maldevelopment with ipsilateral cryptorchidism.