FGFR3 and achondroplasia: The aforementioned decrease in length of the hypertrophic chondrocyte zones in Evc2 mutants is characteristic of Achondroplasia, the most common form of dwarfism in humans caused by gain of function mutations in FGF receptor 3 (FGFR3) [33, 34] To examine whether Evc2 mutant growth plates have altered FGF signaling, we first examined their phospho-ERK level by immunohistochemistry.