A targeting vector was designed to replace exons 2-4 with a loxP-flanked neomycin resistance (pgk-neo) cassette. This mutation introduced a stop codon before the coiled-coil region (CR1) region of the gene. In order to remove the floxed pgk-neo cassette, heterozygous mutant females were crossed to a CMV-cre male on a mixed C57BL/6-129SV background. (J:126871)