The transgenic construct was designed with a CMV-IE enhancer/chicken beta-actin/rabbit beta-globin hybrid promoter (CAG), a loxP-flanked STOP cassette, the mouse Fgfr3 (fibroblast growth factor receptor 3) cDNA containing a lysine to glutamic acid substitution at residue 650 (K650E) rendering Fgfr3 constitutively active, followed by an IRES-eGFP fluorescent protein sequence. (J:212260)