A loxP site within intron 2 and the neomycin cassette flanked by Frt sites and an additional loxP site within intron 3 are inserted by homologous recombination. The conditional allele was generated by breeding with a germline Flp deleter strain Gt(ROSA)26Sor to delete the Neo cassette leaving a single loxP and Frt sites in intron 3. Although the cre-mediated deletion is predicted to result in the production of an in-frame transcript, the gene product from this allele is predicted to be non functional. (J:168155)