A neomycin resistance cassette in which the phosphoglycerate kinase promoter alone is flanked by loxP sites (loxP-PGK-loxP-neo-pA) was inserted 2.6 kb upstream of (distal to) and in the same orientation as the insulin 2 gene on Chromosome 7, between the domain of influence of Chr 7 imprinting center (IC) 1 (H19 DMR) and that of IC2 (KvDMR1).