Cre-mediated excision of the parental Wwtr1tm1Hmc allele to generate global deletion of loxP flanked exon 2 of the Wwtr1 gene leaving a single loxP site and FRT-flanked neo cassette inserted in intron 2. CMV-cre transgnee was subsequently removed by crossing with wildtype mice. It is a null allele. (J:258407)