Del(7Ins2-Tel)1Lef

A neomycin resistance gene under the control of a floxed PGK promoter was placed 2.6 kb upstream of the Ins2 gene. After selection, the PGK promoter was removed by transient Cre expression, leaving a single loxP site upstream of the neomycin resistance gene. Chromosomal sequence distal of the Ins2 gene was then deleted by recombinase mediated chromosome truncation. This was done by using a targeting vector that had telomere repeats followed by a GFP expression cassette and a PGK promoter-loxP cassette suitable to activate the silent neo marker. Cre mediated recombination replaced the portion of chromosome 7 distal to the loxP-neo cassette with the targeting vector. ES cells with the intended deletion were selected by southern blotting and FISH analysis. Germline transmission was established through one chimeric male and subsequent genotyping performed by genomic PCR. (J:130399)