A cDNA encoding amino acids 198-695 with a valine to alanine amino acid substitution at position 490 (V490A) and a floxed neo cassette were knocked into exon d. The neo cassette was removed by cre-mediated recombination following a cross to a cre deleter strain (Tg(CMV-cre)1Cgn). The modification to the coding region is thought to interfere with protein-protein interactions with Met. Expression of the mutant protein confirmed by western blot analysis on protein extracts from E12 embryos was reduced by 40% to 50% relative to levels in wild-type mice. (J:125303)