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Impact of exposures to persistent endocrine disrupting compounds on the sperm methylome in regions associated with neurodevelopmental disorders

ABSTRACT: Although autism spectrum disorder (ASD) is among the most heritable of neurodevelopmental disorders, the rapidly rising prevalence of ASD suggests that environmental factors may interact with genetic risk for ASD. Environmental factors may impact both gene expression and phenotypes in ASD through epigenetic modifications that, in turn, could lead to intergenerational effects influencing risk for ASDs. Endocrine disrupting compounds (EDCs), such as the long-lived organochlorines, are of particular interest with respect to risk for autism because of their ability to interfere with sex hormones that have been implicated in the regulation of RORA, a dysregulated gene in ASD that is a master regulator of many other ASD risk genes. The specific aims of this study are to: 1) investigate whether high versus low exposures to the persistent organochlorine 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) are associated with differentially methylated regions (DMRs) in sperm from a Faroese cohort whose natural diet of pilot whale meat and blubber exposes them to higher than average levels of organic pollutants; 2) determine if genes associated with DDE DMRs are enriched for ASD risk genes; 3) identify pathways and functions over-represented among genes associated with DMRs. Whole genome bisulfite sequencing (WGBS) was used to identify genome-wide DMRs in sperm from individuals divided by high and low exposure levels. Gene ontology and pathway analyses were used to determine enrichment in functional relationships to ASD. Genes in DMRs not only could discriminate between high and low exposures to DDE, but also were enriched in autism risk genes. Gene ontology and pathway analyses of these genes show significant enrichment for neurodevelopmental processes frequently impacted by ASD. Results of this study show that elevated exposure to certain organochlorines is associated with genome-wide DNA methylation patterns in sperm affecting genes involved in neurological functions and developmental disorders, including ASD.

ORGANISM(S): Homo sapiens

PROVIDER: GSE165915 | GEO | 2022/08/31

REPOSITORIES: GEO

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Project description:Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex heritability and higher prevalence in males. The neonatal epigenome has the potential to reflect past interactions between genetic and environmental factors during early development and influence future health outcomes. We performed whole-genome bisulfite sequencing of 152 umbilical cord blood samples from the MARBLES and EARLI high-familial risk prospective cohorts to identify an epigenomic signature of ASD at birth. Samples were split into discovery and replication sets and stratified by sex, and their DNA methylation profiles were tested for differentially methylated regions (DMRs) between ASD and typically developing control cord blood samples. DMRs were mapped to genes and assessed for enrichment in gene function, tissue expression, chromosome location, and overlap with prior ASD studies. DMR coordinates were tested for enrichment in chromatin states and transcription factor binding motifs. Results were compared between discovery and replication sets and between males and females. We identified DMRs stratified by sex that discriminated ASD from control cord blood samples in discovery and replication sets. At a region level, 7 DMRs in males and 31 DMRs in females replicated across two independent groups of subjects, while 537 DMR genes in males and 1762 DMR genes in females replicated by gene association. These DMR genes were significantly enriched for brain and embryonic expression, X chromosome location, and identification in prior epigenetic studies of ASD in post-mortem brain. In males and females, autosomal ASD DMRs were significantly enriched for promoter and bivalent chromatin states across most cell types, while sex differences were observed for X-linked ASD DMRs. Lastly, these DMRs identified in cord blood were significantly enriched for binding sites of methyl-sensitive transcription factors relevant to fetal brain development. At birth, prior to the diagnosis of ASD, a distinct DNA methylation signature was detected in cord blood over regulatory regions and genes relevant to early fetal neurodevelopment. Differential cord methylation in ASD supports the developmental and sex-biased etiology of ASD and provides novel insights for early diagnosis and therapy.

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Impact of exposures to persistent endocrine disrupting compounds on the sperm methylome in regions associated with neurodevelopmental disorders

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