Honors Theses
Date of Award
Spring 5-11-2024
Document Type
Undergraduate Thesis
Department
Chemistry and Biochemistry
First Advisor
Kristine Willett
Second Advisor
John Rimoldi
Third Advisor
Courtney Roper
Relational Format
Dissertation/Thesis
Abstract
The objectives of this study were to determine the sex-dependent contributions to developmental and behavioral effects of preconceptional exposure to benzo[a]pyrene (BaP). BaP is implicated in numerous adverse outcomes in offspring of exposed parents, but the molecular mechanisms for the developmental and multigenerational effects associated with BaP exposures have yet to be fully elucidated. To assess the role of the aryl hydrocarbon receptor (Ahr), a waterborne exposure of the offspring of ahr heterozygous (ahr+/-) parents was conducted. At 120 hpf, BaP treated fish moved significantly less in the dark phase regardless of genotype. At 3 wpf, there were no longer significant differences in behavior. In another experiment, wildtype 5D zebrafish were fed 1% of their bodyweight of 708 ± 24 μg BaP/g food twice per day, resulting in 14 μg BaP/g fish/day for 21 days. Fish were then spawned using a crossover design, resulting in F1 cohorts of control and three crosses from BaP-exposed parents. Behavioral effects were measured at 96 hpf in the F1 fish using the light:dark assay. Significant hyperactivity was observed in both crosses from BaP-exposed male parents. Using an open field test, female F1 adult offspring from the BaP male x BaP female cross were also significantly hyperactive. To assess parental sex-dependent molecular mechanisms that could be contributing to toxicity, gene expression and DNA methylation changes in F0 sperm and eggs and 10 hpf F1 embryos were measured using RNAseq and reduced representation bisulfite sequencing (RRBS), respectively. Embryos resulting from the BaP male and control female cross had the most differentially methylated regions (DMRs) and differentially expressed genes. Some DMRs were associated with genes encoding chromatin modifying enzymes suggesting regulation of chromatin conformation by DNA methylation. Parental dietary BaP exposure caused persistent behavioral changes wherein the male germline contributed most significantly to the multigenerational adverse outcomes.
Recommended Citation
Sturgis, Caroline, "Benzo[a]pyrene-Induced Multigenerational Gene Expression and DNA Methylation Changes are Influenced by Paternal Epigenome" (2024). Honors Theses. 3043.
https://egrove.olemiss.edu/hon_thesis/3043