Changes in DNA methylation over the growing season differ between North Carolina farmworkers and non-farmworkers

Abstract

Purpose The occupational risk to farmworkers, particularly chronic exposure to pesticides, is an acknowledged environmental and work-related health problem. Epigenetics has recently been shown to contribute to a number of complex diseases and traits, including measures of cognitive function and preclinical neurodegenerative disease. We sought to determine if changes in DNA methylation existed between farmworker and non-farmworker populations, and to identify the genes most likely involved in those changes. Methods Eighty-three farmworkers and 60 non-farmworkers were selected from PACE4, a community-based, participatory research project comparing occupational exposures between immigrant Latino farmworker and non-farmworker manual workers. Measurements of DNA methylation were performed with the Infinium HumanMethylation450 BeadChip, at the beginning and end of the 2012 growing season. Bonferroni adjustment was used to identify significant findings (p=1.03 × 10−7, based on 485,000 tested methylation sites), although less stringent criteria (i.e., p≤1 × 10−6) were used to identify sites of interest. Expression quantitative trait locus (eQTL) databases were used to help identify the most likely functional genes for each associated methylation site. Results Methylation at 36 CpG sites, located in or near 72 genes, differed between the two groups (p≤1 × 10−6). The difference between the two groups was generally due to an increase in methylation in the farmworkers, and a slight decrease in methylation in the non-farmworkers. Enrichment was observed in several biological pathways, including those involved in the immune response, as well as Growth Hormone Signaling, Role of BRCA1 in DNA Damage Response, p70S6K signaling, and PI3K Signaling in B Lymphocytes. Conclusions We identified considerable changes in DNA methylation at 36 CpG sites over the growing season that differed between farmworkers and non-farmworkers. Dominant pathways included immune-related (HLA) processes, as well as a number of diverse biological systems. Further studies are necessary to determine which exposures or behaviors are responsible for the observed changes, and whether these changes eventually lead to disease related phenotypes in this population.

Occupational exposure to pesticides as a possible risk factor for the development of chronic diseases in humans

“…The authors for the first time analysed gene-specific, genome-wide DNA methylation in subjects occupationally exposed to pesticides, and their results suggest that there is a single epigenetic profile in farmworkers over the growing season, compared to non-farmworkers. A variety of 72 genes may be involved, supporting the hypothesis that alterations in DNA methylation may affect several biologicalpathways and potential disease development (63). …”

Epigenome-wide association study for pesticide (Permethrin and DEET) induced DNA methylation epimutation biomarkers for specific transgenerational disease

“…This could be particularly important among populations known to experience higher and more chronic levels of exposure to pesticides, such as military and minority populations [12,22,32]. DNA methylation alterations are found in the sperm of agricultural workers [27], another population known to experience higher levels of pesticides exposure. These epigenetic biomarkers associated with disease among ancestrally exposed populations will potentially provide a crucial tool for assessing the health effects in later life for the current generation and the health prospects for future generations.…”

“…The direct exposure to pesticides is more prevalent among some populations, particularly agricultural laborers. Among such a population, increased methylation in or near 72 genes was found as a result of exposure to pesticides, mostly involving immune response genes [27]. Prenatal exposure to persistent pollutants yields hypomethylation in fetal blood [28].…”

Pesticide Exposure Modifies DNA Methylation of Coding Region of WRAP53α, an Antisense Sequence of p53, in a Mexican Population

“…Previously, published data have described changes in DNA methylation by pesticide exposure. − However, no studies have been conducted concerning the WRAP53 methylation in a population exposed to environmental pollutants. Indeed, the information related to humans exposed to pesticides and epigenetic modifications is still limited.…”

“…Some studies have evaluated gene-specific DNA methylation in populations exposed to pesticides. ,,, Specifically, Howard et al identified changes in DNA methylation at 36 CpG sites, located in or near to 72 genes, in farmworkers compared with nonfarmworkers. Lee et al observed a hypomethylation in the Alu assay for men and global DNA hypermethylation in LINE-1 for women in a population exposed to persistent organic pollutant, including organochlorine pesticides.…”