Maternal-biased H3K27me3 correlates with paternal-specific gene expression in the human morula

Genomic imprinting is an epigenetic mechanism by which genes are expressed in a parental-origin-dependent manner. We recently discovered that, like DNA methylation, oocyte-inherited H3K27me3 can also serve as an imprinting mark in mouse pre-implantation embryos. In this study, we found H3K27me3 is strongly biased toward the maternal allele with some associated with DNA methylation-independent paternally expressed genes (PEGs) in human morulae. The H3K27me3 domains largely overlap with DNA partially methylated domains (PMDs), and occupy developmental gene promoters. Thus, our study not only reveals the H3K27me3 landscape but also establishes a correlation between maternal-biased H3K27me3 and PEGs in human morulae. Overall design: We conducted RNA-seq and H3K27me3 ChIP-seq in human morula embryos. To trace parental origin of reads, we performed exome sequencing and/or whole genome sequencing in maternal cumulus cells.