Figure 1. Comparative representation of molecular structure of the IGF2 gene in four different mammalian species.

(A) Numbered red rectangles represent exons, promoter regions are indicated as P1–P4 and intragenic differentially methylated regions as DMR below a rectangle. The mouse IGF2 gene consists of six exons and two additional pseudo-exons²⁸,²⁹. The human³⁰ and pig³¹,³² IGF2 gene consists of ten exons. The bovine IGF2 gene consists of ten exons, transcription of the gene is initiated from four promoters (P1–P4) and transcripts are alternatively spliced³³,³⁴,³⁵,³⁶. Exon 10 contains a DMR that is hypermethylated on the paternal allele²⁷,³⁷. (B) The QTN is indicated with an arrow and the surrounding sequence is shown for four mammals (CpGs are highlighted in red; SNPs are highlighted in blue; a palindromic sequence is underlined).