Exposure to the Heavy-Metal Lead Induces DNA Copy Number Alterations in Zebrafish Cells

Abstract

DNA copy number variants are associated with the development of complex neurological diseases and disorders including autism spectrum disorder, schizophrenia, Alzheimer's disease, and Parkinson's disease. Exposure to multiple environmental chemicals including various heavy metals is suggested as a risk factor in these neurological diseases and disorders, but few studies have addressed if heavy-metal exposure can result in de novo DNA copy number changes as a genetic mechanism contributing to these disease outcomes. In this study to further investigate the relationship between heavy-metal exposure and de novo copy number alterations (CNAs), zebrafish fibroblast cells were exposed to the neurotoxicant lead (Pb). A crystal violet assay was first used to determine exposure concentrations with >80% cell confluency. Then a zebrafish-specific array comparative genomic hybridization platform was used to detect CNAs following a 72 h Pb exposure (0.24, 2.4, or 24 μM). The Pb exposure resulted in 72 CNA amplifications ranging in size from 5 to 329 kb. No deletions were detected. CNAs resulted in 15 CNA regions (CNARs), leaving 7 singlet CNAs. Two of the singlets were within high repeat genomic locations. The number of CNAs tended to increase in a concentration-dependent manner. Several CNARs encompassed genes previously reported to have altered expression with Pb exposure, suggesting a mechanistic link. In addition, almost all genes are associated within a molecular network with amyloid precursor protein, a key molecular target associated with the pathophysiology of Alzheimer's disease. Overall, these findings show that Pb exposure results in de novo CNAs that could serve as a mechanism driving adverse health outcomes associated with Pb toxicity including neurological disease pathogenesis for further study.

Zebrafish as model organisms for toxicological evaluations in the field of food science

“…Tian et al (2020) found that parental zebrafish exposure to 1 µM Cd for 60 days resulted in malformed offspring and reduced levels of 3,5,3′-triiododenosine (T3) and thyrox-ine (T4), which caused reproductive toxicity and thyroid endocrine system developmental toxicity. Exposure to the heavy metal Pb causes intestinal microbiota imbalance, liver metabolism disorders (Xia et al, 2018), developmental toxicity, and neurotoxicity in zebrafish (Lee & Freeman, 2020). Chen et al (2012) confirmed that the exposure of zebrafish embryos to Pb can cause malformations, change the spontaneous movement and behavior of larvae in a dose-dependent manner, and result in learning and memory deficits in adulthood.…”

“…(2020) found that parental zebrafish exposure to 1 µM Cd for 60 days resulted in malformed offspring and reduced levels of 3,5,3′‐triiododenosine (T3) and thyroxine (T4), which caused reproductive toxicity and thyroid endocrine system developmental toxicity. Exposure to the heavy metal Pb causes intestinal microbiota imbalance, liver metabolism disorders (Xia et al., 2018), developmental toxicity, and neurotoxicity in zebrafish (Lee & Freeman, 2020). Chen et al.…”

Advances of Zebrafish in Neurodegenerative Disease: From Models to Drug Discovery

“…This indicates that aluminuminduced AD is due to increased AChE activity. A recent study assessed the neurotoxic role of lead (Pb), a heavy metal, in zebrafish fibroblast cells (Lee and Freeman, 2020). The findings suggested that Pb exposure results in de novo DNA copy number alterations in a dose-dependent manner.…”

Pb Transfer Preference of Arbuscular Mycorrhizal Fungus Rhizophagus irregularis in Morus alba under Different Light Intensities

“…As a non-essential element, lead (Pb) accumulated in soils has become an immense risk for animals and humans due to its toxicity even at low concentrations [3][4][5]. Short-term exposure to Pb can cause brain and kidney damage, while long-term exposure can harm the central nervous and reproductive system, which can even lead to death [6][7][8]. China has the second largest Pb reserves in the world, producing an estimated two million metric tons of Pb in 2021 [9].…”