The transgenic construct is composed of a Cre recombinase coding sequence under the control of the Pdx1 promoter. Cre expression is thus directed to islet cells of the pancreas. Line 6 was inserted into chromosome 8 about 48 kb upstream of Zfp423 (chr8:90,531,639; NCBI37/mm9) with elements of human ACTB 3'UTR and polyA signal, and a 1.5 kb genomic duplication at the integration site.