An FRT-flanked neo cassette with a 5' loxP site was inserted in intron 6. A mutation at the end of intron 7 was introduced with an A-to-G mutation in the splice acceptor site of exon 8 (c.919-2A>G). This point mutation results in the abolition of the splice site and consequently the exclusion of out-of-frame exon 8 from transcripts and the introduction of a stop codon at codon position 348. Flp-mediated recombination removed the neo cassette.