Chromatin regions, genes and pathways that confer susceptibility to chemical-induced DNA damage
ABSTRACT
Genetic variability has a major impact on susceptibility to common diseases, responses to drugs and toxicants,
and influences disease-related outcomes. In addition, the links between genetic variability, toxicity outcomes and
epigenetics are being actively explored. However, studies of Gene × Environment × Epigenetics are difficult as
they involve interrogation of multiple individuals, exposure doses/times, tissue types, -omics endpoints and
various toxicity phenotypes. This proposal aims to identify and validate chromatin regions, genes and
pathways that confer susceptibility to environmental chemical-induced and metabolism-associated DNA
damage. We will perform a series of proof-of-principle studies of the interplay between DNA damage induced
by 1,3-butadiene, a genotoxic carcinogen, genetics, and epigenetics. We have extensive experience performing
toxicology studies in the mouse (Collaborative Cross, CC) and human (1000 Genomes lymphoblast cell lines)
population-based models. First, we will determine expression and chromatin quantitative trait loci (QTL) of
butadiene genotoxicity in mouse tissues. We will test the hypothesis that strain- and tissue-specific variation in
butadiene-induced DNA damage is controlled by the genetic variability-dependent background states in
chromatin and gene expression. We will use tissues (liver, lung and kidney) from a study of 50 CC strains
exposed to butadiene and will evaluate butadiene DNA damage and identify regions of active/repressed
enhancers and promoters. Second, we will determine dose- and time-effects of butadiene-induced DNA damage
in the context of background and treatment-induced chromatin and transcriptional states. We will test the
hypothesis that butadiene exposure modifies strain- and tissue-specific epigenetic states in a dose-dependent
manner and that DNA damage-associated effects on chromatin persist. We will examine inter- vs intra-strain
variability, dose- and time-dependency in select CC strains. Third, we will characterize the extent of population
variability in response to butadiene metabolites in a human in vitro population model. We will test the hypothesis
that human lymphoblasts can be used to map susceptibility loci for butadiene genotoxicity. Fourth, we will
validate the discoveries of the transcriptional and epigenetic mediators of strain-dependent DNA damage by
butadiene in a human in vitro population-based model. We will test the hypothesis that genetic background-
dependent transcriptional and epigenetic states confer susceptibility/resistance to butadiene-induced DNA
damage. We will evaluate chromatin states and expression coupled with assays for DNA adducts. Overall, this
work will demonstrate the interplay among environment (i.e., chemical exposure), genetics, and epigenetics by
studying effects of 1,3-butadiene, an industrial toxicant and model genotoxic carcinogen. Human relevance and
feasibility are justified by the focus on a fundamental mechanism of toxicity and carcinogenesis, the fact that
butadiene is a known human and rodent carcinogen, and our previous work demonstrating butadiene effects of
chromatin, histone modifications and other epigenetic states in a strain- and tissue-dependent manner.