title: Lead (Pb) exposure reduces global DNA methylation level by non-competitive inhibition and alteration of dnmt expression.
abstract: Low-dose exposure to lead (Pb) is connected to developmental neurological alterations by inducing molecular changes, such as aberrant gene expression patterns. The attributing molecular mechanism, however, is not well-elucidated. In this study, we revealed epigenetic features and mechanisms that can alter gene expression patterns by identifying changes in DNA methyltransferase (DNMT) activity, expression pattern and DNA methylation level using moelcular studies and a zebrafish animal model. We characterized the effects of Pb on the activities of various DNMTs in vitro and determined the molecular role of Pb in modulating DNMT activity via kinetic experiments. An exposure of 100 or 500 ppb of Pb was found to significantly lower the activity of maintenance DNMTs. The inhibition mechanism can be described using non-competitive Michaelis-Menten kinetics. A zebrafish animal model was then used to assess the biological significance of our findings. An embryonic exposure to 100 or 500 ppb Pb resulted in a significant change in global methylation levels consistent with previous studies using human and rodent model. Our study also suggests that Pb exposure in zebrafish alters the expression patterns of dnmt3 and dnmt4 which are human DNMT3b orthologs. The knowledge from this study suggests that Pb exposure can affect the activity of maintenance DNMTs via non-competitive inhibition, which has not been reported previously. Meanwhile, the expression pattern of de novo methyltransferases can also be altered. Collectively, they result in a reduction in global DNA methylation level in Pb-exposed zebrafish model, which can be compared to findings in human and rodent studies.
authors.affiliation: School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA. cyuan@purdue.edu.
authors.forename: Oscar F
authors.identifier: 0000-0003-2237-0945
authors.initials: OF
authors.lastname: Sanchez
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA. jfreema@purdue.edu.
authors.forename: Jinyoung
authors.initials: J
authors.lastname: Lee
authors.affiliation: School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA. cyuan@purdue.edu.
authors.forename: Nathaphon
authors.initials: N
authors.lastname: Yu King Hing
authors.affiliation: School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA. cyuan@purdue.edu.
authors.forename: Seong-Eun
authors.initials: SE
authors.lastname: Kim
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA. jfreema@purdue.edu.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Freeman
authors.affiliation: School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA. cyuan@purdue.edu.
authors.forename: Chongli
authors.initials: C
authors.lastname: Yuan
mesh_terms: D000818:Animals; D019175:DNA Methylation / Q000187:drug effects*; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007854:Lead / Q000633:toxicity*; D008780:Methyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics; D011401:Promoter Regions, Genetic; D020218:Response Elements; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D029961:Zebrafish Proteins; D007854:Lead; D008780:Methyltransferases