Re-expression of inactive Igf2 allele in aging mouse tissues. A, DLP tissues were microdissected from aging mice (3, 11, 19, and 24 mo) and the maternal and paternal allelic expression was measured using FluPE. The ratio of the inactive allele (Ai) to active allele (Aa) was calculated for each aging cohort (n = 6). All DLP samples in the 11-, 19-, and 24-month cohorts have significantly higher Ai/Aa ratios when compared with the 3-mo-old cohort (**, P < 0.01; *, P < 0.05). B, Igf2 imprinting is maintained with aging in the VP and other mouse tissues. Allelic expression from the liver, kidney, and VP was determined using FluPE. Tissues from 3- and 19-mo-old cohorts (n = 6) were compared and no age-associated relaxation of Igf2 imprinting was seen.