Project description:Methylmercury (MeHg) is a ubiquitous environmental toxicant that is often detected in the tissues of fish-eating species. It has been well established that prenatal exposure to MeHg can lead to widespread brain damage and impaired neurological development resulting in defects ranging from severe cerebral palsy and cognitive deficits to impaired motor and sensory function. A wide range of environmental toxicants have been shown to induce transgenerational inheritance of diseases via changes in DNA methylation—a well-known epigenetic modification. Our previous research has demonstrated that developmental MeHg exposure may yield transgenerational inheritance of neurological dysfunction in adult F3-lineage zebrafish via quantitative neurobehavioral assays that evaluated the visual startle response, retinal electrophysiology, and locomotor function. The objective of the current study was to examine the correlation between neurobehavioral phenotypes and the transcriptome activity in the brain and retina of F3 zebrafish by RNA sequencing (RNAseq). Transcriptomic analyses of F3 generation MeHg-treated zebrafish (compared to control) revealed significant gene dysregulation in both the brain and retina. There were 1648 and 138 differentially expressed genes in the retina and brain, respectively (FDR <0.05). Thirty-five genes were commonly dysregulated in both organs. Gene set enrichment analysis revealed significantly enriched pathways including: neurodevelopment, visual functions, phototransduction, and motor movement. Moreover, commonly dysregulated genes were associated with circadian rhythm and metabolic pathways, as well as arginine and proline metabolism. To our knowledge, this is the first evidence of a transgenerational transcriptome induced by ancestral developmental exposure to MeHg in any species. If the transgenerational phenotypes, transcriptome, homologous biomarkers, or similar molecular pathways hold true for human populations, our findings have significant impact on global public health in terms of identifying the susceptible populations using biomarkers and preventing transgenerational inheritance of MeHg-induced neurobehavioral deficits.

Project description:The transgenerational inheritance of epigenetic information is an attractive mechanism by which the phenotypic consequences of exposure of parents to certain environmental conditions could be transmitted to the next generation. Although this phenomenon is well described in yeast and plants, and in some invertebrates, such as the D. melanogaster and C. elegans, the evidence for transgenerational inheritance in vertebrates is scarce. Among the mechanisms that are known or suspected to be involved in mediating the propagation of epigenetic information to subsequent generations, the process of enzymatic DNA methylation is of particular interest. During DNA replication, the methylation pattern of the parental strand is faithfully copied onto the daughter strand by the maintenance methylase DNMT1, although methylation patterns can be changed through the action of de novo methylases and mechanisms of active and passive demethylation. In the context of epigenetic inheritance, the induction of aberrant methylation patterns in gametes may set the stage for transmission into future generations. Here, we describe a viable hypomorphic allele of dnmt1 in zebrafish that causes widespread demethylation of CpG dinucleotides in sperm and somatic tissues. Surprisingly, homozygous mutants present with an essentially normal phenotype, with the exception of drastically impaired lymphopoiesis, affecting both larval and adult phases of T cell development. Male but not female mutants are fertile. The phenotype of impaired larval (but not adult) T cell development is transmitted to subsequent generations by about 50% of fish that are genotypically wildtype. Whole genome bisulfite sequencing of sperm DNA of transmitting and non-transmitting males identified about 200 differentially methylated regions, including hypermethylated sites associated with runx3 and rptor genes. Knock-down of these two genes leads to impaired larval T cell development. Our results raise the possibility of an epigenetic origin of certain immunodeficiency syndromes in animals and humans.

			Action	DRS
	SRR10292773_1.fastq.gz	Fastqsanger.gz
	SRR10292773_2.fastq.gz	Fastqsanger.gz
	SRR10292774_1.fastq.gz	Fastqsanger.gz
	SRR10292774_2.fastq.gz	Fastqsanger.gz
	SRR10292775_1.fastq.gz	Fastqsanger.gz

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Danio rerio

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