Igf2^tm1Wrk

Sequence encompassing the second placenta-specific exon (U2) and the first differentially methylated region (DMR1 or Rr15), located 3 kb upstream of the first fetal promoter (P1), was replaced by a single loxP site following cre-mediated recombination. In contrast to the wild-type allele, which is silenced soon after birth, both maternally and paternally transmitted alleles continued to be transcribed postnatally. In addition to the loss of imprinting, the deletion resulted in the ablation of placenta-specific transcript. Transcript was undetected by in situ hybridization of placentae from heterozygous mice carrying a paternally transcribed mutant allele. (J:65001)