Transgenerational Disease Specific Epigenetic Sperm Biomarkers after Ancestral Exposure to Dioxin

Dioxin is one of the most common historic industrial contaminants with several major industry and government accidents having exposed large numbers of the worldwide population over the past century. Previous rat studies have demonstrated the ability of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)) exposure to promote the epigenetic transgenerational inheritance of disease susceptibility in subsequent generations. The types of disease observed include testis, ovary, kidney, prostate and obesity pathologies. The current study was designed to use an epigenome-wide association study (EWAS) to identify potential sperm DNA methylation biomarkers for specific transgenerational diseases. The transgenerational F3 generation dioxin lineage male rats with and without a specific disease were compared to identify differential DNA methylation regions (DMRs). The genomic features of the DMRs are characterized. Observations demonstrate that disease specific epimutation DMRs exist for the transgenerational dioxin lineage rats that can potentially be used as epigenetic biomarkers for testis, ovary, kidney, prostate and obesity diseases. These disease specific DMRs were associated with genes that have previously been shown to be linked with these diseases. This EWAS for transgenerational disease identified epigenetic biomarkers and provides the proof of concept of the potential to develop similar biomarkers for humans to diagnose disease susceptibilities and facilitate preventative medicine. Analysis of the transgenerational actions of dioxin used outbred Sprague Dawley female rats (F0 generation) transiently exposed (TCDD 100 ng/kg BW/day) during days 8 to 14 of gestation. The F1 generation animals (direct fetal exposure) were bred to generate the F2 generation (direct germline exposure), which were bred to generate the F3 generation (transgenerational so no direct exposure). The dioxin lineage was aged to 1 year and euthanized for pathology and sperm epigenetic analysis. No sibling or cousin breedings (crosses) were used to avoid any inbreeding artifacts. Generally 6–8 founder gestating females from different litters were bred and 25–50 individuals of each sex obtained for each generation.