The ICR (2.4 kb BglII fragment with chromatin insulation, promoter silencing and imprinting (differential methylation) function) between the Igf2 and H19 genes was replaced with a loxP site flanked neomycin resistance gene cassette and a 2.4 kb sequence containing two copies of the chicken beta globin chromatin insulator ((ChbetaGI)2). The neo cassette was removed through subsequent cre-mediated recombination. (J:308869)