An FRT site and a loxP site were inserted in intron 10 and a neomycin resistance cassette followed by a second loxP site was inserted following exon 11. Finally, a second exon 11 with a stop codon in codon 367 (AAG to TAG change) was inserted after the second loxP site. Excision of the first copy of exon 11 by cre expression results in expression from the second copy of exon 11 which contains a premature stop codon leading to a truncated protein lacking the final 24 amino acids.