Exon 2 was replaced by a mutated form of human cDNA, in which the Lys833 was converted into Arg, followed by a neomycin resistance gene (Neor) cassette flanked by loxP sequences. Heterozygous mice were crossed with Balancer cre mice to delete the Neor cassette. RT-PCR revealed exclusive production of mutant mRNA. (J:91945)