A targeting vector was designed to flank exons 8-10 with loxP sites. Cre mediated recombination resulted in the excision of those exons. Northern blot detected a truncated transcript in mutant brain samples. RT-PCR and sequencing revealed that the correct exons were deleted and that most mutants were lacking exon 7 due to alternative splicing. The deletions created a frameshift mutation beyond exon 6 or 7, resulting in truncated proteins beyond those exons. (J:106803)