Approximately 3.1 kb of upstream sequence was replaced with the equivalent region upstream of the human insulin gene. IRES sequence and an EGFP reporter gene cassette were inserted into the 3' UTR. The loxP site flanked neomycin resistance gene cassette that was also inserted was removed through subsequent cre-mediated recombination. In this allele the human INS promoter drives expression of the mouse Ins2 gene and the EGFP reporter. Immunofluorescence experiments confirmed that the allele is expressed in neonatal insulin-positive pancreatic islet core beta cells only. (J:308553)