The targeting vector contained homology arms flanking a nuclear localization signal (NLS) fused to a fragment encoding cre recombinase with a polyadenylation signal. Red/ET recombination in bacterial cells inserted the NLS-cre sequence at the translation initiation site in exon 2 of the Ins1 gene located in a BAC (RP23-181I21). The engineered BAC was linearized and injected into pronuclei of fertilized C57BL/6N oocytes. Five founders had the inserted transgnene (#'s 7, 24, 25, 28 and 32). Line 25 was used further as recombinase reporter activity in the pancreas in F1 crosses was greater than that from other founders. (J:205139, J:208032)