A loxP site was inserted in intron 6 upstream of exon 7, a neomycin selection cassette flanked by FRT sites in intron 9 followed by a loxP site. The neomycin cassette and exons 7-9 were removed via cre-mediated recombination. Excision of exons 7-9 removes the first RNA Recognition Motif and places the remaining transcript out of frame, generating a null allele. (J:226997)