Targeting vector HTGRS6013_A_D10 from the Knock-out Mouse Project inserted an FRT flanked IRES-lacZ-pA cassette linked to a strong splice acceptor signal, together with a loxP flanked neomycin selection cassette into intron 6 and an additional loxP site into intron 7, thus flanking exon 7 with loxP sites. The lacZ cassette was removed via flp-mediated recombination. Exon 7 was deleted via cre-mediated recombination in the germline.