Recombination-mediated cassette exchange (RMCE) was used to replace exons 76 through 89 with an frt-flanked cassette containing a cDNA for exons 76 through 89 and a floxed neo gene. The cDNA contains mutations in exon 89 that result in amino acid substitutions of NPVY with AAVA and disrupt the NPXY2 site and YXXL motif. (J:144146)