Retroviral insertion of a transgene carrying a neo cassette with a 5' loxP site was used to create the TIGRE loci at chromosome 9 qA3 between AB124611 and Carm1. Cre-mediated cassette exchange was used to introduce a Apoe gene with a 5' loxP site prior to the neo cassette. The Apoe gene is inducible and floxed. (J:136987)