A neomycin resistance cassette in which the coding sequence and polyadenylation site are flanked by loxP sites (PGK-loxP-neo-pA-loxP) was inserted 4.34 kb 3' of (centromeric to) the third, last coding exon of Ascl2, between Chr 7 imprinting center 1 (IC1/H19 DMR) and IC2/KvDMR1. Cre recombinase deletion of the floxed segment left the PGK promoter and a loxP site. (J:153719)