A targeting construct consisting of introns 3-8 was constructed with a nucleotide change (A to G) in exon 5 to mutate amino acid 88 from a glycine to a glutamic acid (G88E). A loxP-flanked neomycin resistance cassette was also introduced into intron 5. Founder mice were bred with EIIa-cre mice to excise the selection cassette, leaving behind a single loxP site in intron 5. Expression of the mutant gene was confirmed by RT-PCR and by immunohistochemistry on inner ear sections.