The loxP sequence and Neo cassette flanked by two frt sites were inserted into a site 331 bp upstream of exon 12. An internal ribosomal entry site (IRES) sequence and splice donor (SD) sequence from exon 8 of the mouse Hprt gene were inserted downstream of the Neo cassette for the poly-A trapping strategy. The other loxP site was introduced into a site 185 bp downstream of exon 12 to eliminate the putative transmembrane domain after Cre-mediated recombination. (J:279639)