A floxed neomycin selection cassette was inserted in intron 2 and a third loxP was inserted in intron 4. The neomycin selection cassette was then removed by transient cre expression leaving exons 3 and 4 floxed. Subsequently, mice were crossed to Tg(EIIa-cre)C5379Lmgd mice to excise exons 3 and 4 creating a knockout allele. (J:161993)