The sequence for icre was inserted into a BAC (RP24-298N3) by recombineering techniques, replacing the sequence between the start codon in exon 2 and the stop codon in exon 6 of the mouse Gip locus. The modified BAC was purified and injected into fertilized oocytes. Three founder lines (-117, -122, and -125) were established (estimated transgene
copy numbers were 1; 1, and 2). Line 117 was used in all experiments.