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. 2021 May 10;7(1):dvab004.
doi: 10.1093/eep/dvab004. eCollection 2021.

Perinatal DEHP exposure induces sex- and tissue-specific DNA methylation changes in both juvenile and adult mice

Affiliations

Perinatal DEHP exposure induces sex- and tissue-specific DNA methylation changes in both juvenile and adult mice

Siyu Liu et al. Environ Epigenet. .

Abstract

Di(2-ethylhexyl) phthalate (DEHP) is a type of phthalate plasticizer found in a variety of consumer products and poses a public health concern due to its metabolic and endocrine disruption activities. Dysregulation of epigenetic modifications, including DNA methylation, has been shown to be an important mechanism for the pathogenic effects of prenatal exposures, including phthalates. In this study, we used an established mouse model to study the effect of perinatal DEHP exposure on the DNA methylation profile in liver (a primary target tissue of DEHP) and blood (a common surrogate tissue) of both juvenile and adult mice. Despite exposure ceasing at 3 weeks of age (PND21), we identified thousands of sex-specific differential DNA methylation events in 5-month old mice, more than identified at PND21, both in blood and liver. Only a small number of these differentially methylated cytosines (DMCs) overlapped between the time points, or between tissues (i.e. liver and blood), indicating blood may not be an appropriate surrogate tissue to estimate the effects of DEHP exposure on liver DNA methylation. We detected sex-specific DMCs common between 3-week and 5-month samples, pointing to specific DNA methylation alterations that are consistent between weanling and adult mice. In summary, this is the first study to assess the genome-wide DNA methylation profiles in liver and blood at two different aged cohorts in response to perinatal DEHP exposure. Our findings cast light on the implications of using surrogate tissue instead of target tissue in human population-based studies and identify epigenetic biomarkers for DEHP exposure.

Keywords: DEHP exposure; DNA methylation; bisulfite sequencing; blood; liver; mouse model; perinatal.

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Figures

Figure 1:
Figure 1:
overview of the study design. (A) DEHP exposure paradigm showing the duration of the exposure, details of the exposure, and times of tissue collection. (B) Bar plot shows the number of animals in each exposure group per tissue, age, and sex.
Figure 2:
Figure 2:
overview of the number of DMCs between DEHP exposure and control groups. The bar plot shows the number of hypermethylated and hypomethylated DMCs in DEHP separately for each comparison at both PND21 and 5 months.
Figure 3:
Figure 3:
annotated locations of the differentially methylated cytosines (DMCs) and heterogeneity among the animals in blood and liver. (A) Stacked bar plot of 3 week (PND21) DMCs annotated to CpG islands, shores, shelves, and (B) regions relative to genes. (C) Stacked bar plot of 5-month DMCs annotated to CpG islands, shores, shelves, and (D) regions relative to genes. The ‘All’ column indicates all the DMCs tested in each condition. (E) PCA plot showing the distribution of each individual mouse based on the methylation level of DMCs in at least one comparison in blood and (F) in liver.
Figure 4:
Figure 4:
sex- and tissue-stratified genome-wide DNA methylation levels at CpG islands, shores, and shelves at (A) 3 weeks (PND21) and (B) 5 months. Blood shows higher DNA methylation levels than liver in CpG shores and shelves for both sexes, and with tissue differences increasing with mouse age.
Figure 5:
Figure 5:
sex- and tissue-stratified genome-wide DNA methylation levels of imprinted genes at CpG islands, shores, and shelves at (A) 3 weeks (PND21) and (B) 5 months. Blood shows higher DNA methylation levels than liver in CpG shores and shelves for both sexes, and slightly higher level of differences in liver was observed between DEHP and control group compared with the differences in blood.
Figure 6:
Figure 6:
differential gene expression analysis on the same cohort. (A) Bar plot showing the number of upregulated and downregulated genes in blood and liver separately at the two time points. (B) Scatterplot showing all the DMCs that overlapped with upregulated or downregulated genes. The top half represents genes that are significantly upregulated in DEHP exposure groups, and the right half represents hypermethylated DMCs in DEHP exposure groups. Sites that showed opposite direction of DNA methylation and gene expression are labeled with gene symbols.

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