FIG. 3.

Phenotype of the 17.5-dpc fetuses inheriting the four CTCF site mutations in the H19/Igf2 ICR. (A) Reverse transcription-PCR single-nucleotide primer extension assays. In the −(M)/+ and +/+ lanes, the top row is the presumptive inactive allele. For the +/−(P) lanes (in boxes), these fetuses were obtained from the reciprocal mating, and hence the bottom row is the presumptive inactive allele. Parental origin of alleles is on the right. The value above each band is the amount of RNA contributed by the presumptive inactive allele as a percentage of the total. (B) Northern blotting results. Values under bands are the mean relative amounts of RNA standardized according to Gapd mRNA. Each lane represents an individual embryo. For Igf2 only the shortest transcript is shown, but the value represents the total of all transcripts.