Figure 5.

Summary schematic depiction showing dynamic regulation of Igf2r and Airn in the embryonic lineage. In the EPI, Igf2r is biallelic and Airn is not expressed. During gastrulation, maternal methylation at DMR2 spreads, followed by initiation of paternal Airn expression and then silencing of paternal Igf2r. In the extraembryonic lineage (right side), reciprocal imprinting of Igf2r and Airn is already established in VE at E6.5. DMR2 methylation spreads but does not correlate with changes in allelic expression in extraembryonic lineage. Paternal specific binding of Ctcf occurs at DMR2 in the extraembyronic lineage, but not in the embryo. Additionally, lineage- and allele-specific histone modifications are present at DMR1 and DMR2 suggesting an epiblast-specific mechanism required to establish imprinted expression.