IGF2 antisense transcript expression in porcine postnatal muscle is affected by a quantitative trait nucleotide in intron 3.

A paternally expressed quantitative trait locus (QTL) for muscle mass was mapped to the insulin-like growth factor II (IGF2) locus at the distal end of pig chromosome 2p. It was recently demonstrated that a G to A transition at position intron 3-nt 3072 is the quantitative trait nucleotide (QTN) underlying this QTL. In this study we report for the first time the existence of imprinted porcine IGF2 antisense transcripts (IGF2-AS) and demonstrate that their expression in postnatal muscle is also affected by the QTN. A coregulated expression of IGF2 and IGF2-AS RNAs in muscle and liver with decreasing transcription from fetal to adult age was demonstrated. Further, the significant difference found in expression of IGF2-AS in postnatal muscle between individuals with different QTL genotypes and the lack of significant differences in fetal muscle and liver reflect completely what has been found for IGF2 sense transcripts.