The endogenous allele was released from imprint-mediated regulation by deleting the CpG rich sequences of region 2 using molecular techniques. A 3.7 kb fragment was replaced with a floxed hygro cassette which was subsequently excised in vitro via cre mediated recombination. Slot blot and RNAse protection assay analyses showed normal transcript to be produced from the targeted locus. (J:68721)