A loxP site and an Sph I site were inserted upstream of the distal enhancer element and the 450 bp proximal enhancer element was replaced with an FRT flanked neo cassette and a loxP site. Recombinase mediated recombination removed the neo cassette and a 3.1 kb region including the distal and the ectodermal enhancer elements. RT-PCR analysis indicates reduced pancreatic expression in homozygous mice at E15.5. (J:182769)