Fig. 7

Summary of epigenetic regulation of non-canonical imprinting in embryonic development. Schematic diagram showing the allelic epigenetic regulation of a non-canonically imprinted gene by an ERVK LTR element (top) and the dynamic regulation of non-canonically imprinted ERVK LTRs across pre- and post-implantation development (bottom). In the pre-implantation embryo, inherited H3K27me3 from the oocyte silences the maternal allele. In the post-implantation embryo, maternal H3K27me3 transitions to imprinted maternal DNA methylation in extra-embryonic lineages, thereby retaining the imprinted paternal expression of the ERVK LTR. Alternatively, in the embryonic lineages, both the maternal and paternal alleles acquire DNA methylation, consequently silencing the ERVK LTR transcription. The maternal allele is shown in red, and paternal allele is shown in blue. In the allelic enrichment plot, the solid line is the level of H3K27me3, and the dashed line is the level of DNA methylation. Embryonic day (E) is shown on the x-axis for each respective stage of embryogenesis