The two models that are often used for preclinical testing are: (1) the knock-in model of the thanatophoric dysplasia type I (TDI) mutation Y367C into the mouse Fgfr3 gene, which displays an achondroplasia phenotype14, and (2) the transgenic model expressing mouse Fgfr3 containing the achondroplasia mutation G380R under the type II collagen (Col2) promoter (Ach)12. Here, FGFR3 is linked to achondroplasia.