Fgfr3tm1Iwa animals carry a lysine to methionine substitution at residue 644 (K644M) of exon 10 and a floxed neo cassette in intron 10. The neo cassette was removed by crossing Fgfr3tm1Iwa mutants to the cre expressing line, TgN(EIIa-cre)C5379Lmgd. Northern blot analysis of brain RNA from mutant animals showed a similar level of gene expression as wild-type. (J:70061)