LoxP sites and a neomycin selection cassette were inserted into the flanking regions of exon 5. Mice heterozygous for the targeted allele were crossed with protamine-Cre transgenic mice to remove the neomycin cassette and exon 5. Deletion of exon 5 induced a frameshift and disrupted expression of the encoded protein. Expression of both the long form and the short form of the encoded protein was affected.