FGFR2 knockout is an embryonic lethal mutation and blocks limb bud initiation.

Fibroblast Growth Factor Receptor 2 (FGFR2) is a high affinity receptor for several members of the FGF family. The FGFR2 gene was inactivated by deleting the entire immunoglobulin-like domain of the receptor which is critical for FGF binding and FGFR2 activity. Embryos that lack this domain die at E10-11.5 owing to a failure in chorioallantoic fusion or placental formation. The deletion also blocks limb bud initiation, establishing FGFR2 as the major receptor that mediates FGF signals during limb induction.