Ins2^tm1Lef

This allele was generated by Cre recombinase mediated modification of Ins2tm1.1Nagy in ES cells. A Pgk promoter preceded by a loxP site was inserted to reactivate the promoterless loxP-neo-pA insertion residing 2.6 kb upstream of the Ins2 transcription initiation site in that mutation. The new insertion also contains a 1.6 kb array of telomere repeats and a CAG-EGFP reporter gene, which consists of the enhanced green fluorescent protein coding sequence, with a polyadenylation signal, under control of the "CAG promoter," which comprises the cytomegalovirus immediate early (CMV-IE) enhancer followed by the promoter, first exon and first intron of the chicken beta-actin gene, with the 3' splice junction sequence replaced by that of the rabbit hemoglobin beta gene. EGFP expression in the embryo is regulated by genomic imprinting from Chr 7 imprinting center 1 (IC1) and occurs only when the reporter gene is maternally inherited. In contrast, EGFP is expressed in heterozygous plancentae regardless of its maternal or paternal transmission. (J:154092)