Paternal obesity alters the sperm epigenome and is associated with changes in the placental transcriptome and cellular composition

Summary Paternal obesity has been implicated in adult-onset metabolic disease in offspring. However, the molecular mechanisms driving these paternal effects and the developmental processes involved remain poorly understood. One underexplored possibility is the role of paternally driven gene expression in placenta function. To address this, we investigated paternal high-fat diet-induced obesity in relation to sperm epigenetic signatures, the placenta transcriptome and cellular composition. C57BL6/J males were fed either a control or high-fat diet for 10 weeks beginning at 6 weeks of age. Males were timed-mated with control-fed C57BL6/J females to generate pregnancies, followed by collection of sperm, and placentas at embryonic day (E)14.5. Chromatin immunoprecipitation targeting histone H3 lysine 4 tri-methylation (H3K4me3) followed by sequencing (ChIP-seq) was performed on sperm to define obesity-associated changes in enrichment. Paternal obesity corresponded with altered sperm H3K4me3 enrichment at imprinted genes, and at promoters of genes involved in metabolism and development. Notably, sperm altered H3K4me3 was localized at placental enhancers and genes implicated in placental development and function. Bulk RNA-sequencing on placentas detected paternal obesity-induced sex-specific changes in gene expression associated with hypoxic processes such as angiogenesis, nutrient transport and imprinted genes. Paternal obesity was also linked to placenta development; specifically, a deconvolution analysis revealed altered trophoblast cell lineage specification. These findings implicate paternal obesity-effects on placenta development and function as one mechanism underlying offspring metabolic disease. Summary sentence Paternal obesity impacts the sperm epigenome at genes implicated in placenta development and is associated with an altered placenta transcriptome and trophoblast cell lineage specification.