165. PLASTICITY IN IMPRINTING OF BOVINE IGF2R CORRELATES WITH TOTAL EXPRESSION LEVELS IN FETAL TISSUES

Abstract

The multifunctional insulin-like growth factor 2 receptor (IGF2R) facilitates endocytosis and subsequent clearance or activation of a variety of ligands involved in cell growth and motility. Thus, the IGF2R gene has a major role in embryonic development and fetal growth. Murine Igf2r is subject to genomic imprinting and maternally expressed in peripheral fetal tissues. However, data on imprinting of IGF2R in human is still controversial with biallelic expression, partial imprinting, and monoallelic expression reported for fetal tissues [1, 2, 3]. Data from additional species may help to understand fetal IGF2R expression. The bovine is similar to human in that it is outbred and monotocous. We have analysed bovine Day 153 fetuses (55% to term, n=40) with Bos primigenius indicus and B. p. taurus genetics to determine the imprinting status of IGF2R in fetal brain, liver and skeletal muscle. Sequencing of PCR amplicons from IGF2R exon 48 revealed a polymorphic microsatellite and 14 SNPs. These were used to identify 15 heterozygous fetuses informative for imprinting analysis. We found biallelic expression of IGF2R in fetal brain and predominantly maternal expression in fetal liver and skeletal muscle. However, we observed considerable plasticity in imprinting in liver and skeletal muscle with paternal expression levels of 7%-21% and 4%-21%, respectively. Fetal liver samples with B. p. indicus maternal genetics showed significantly higher mean paternal expression levels than those with B. p. taurus maternal genetics (P<0.05). Real-time qPCR showed a significant relationship between imprinting and total IGF2R expression level within both tissues (P<0.05). Our data indicate plasticity in imprinting of IGF2R that could fine tune expression levels in fetal tissues.