Exposure to Polychlorinated Biphenyl 153 Affects Circadian Rhythm Behavior and Gene Expression in Zebrafish

Environmental chemicals are known to impact the health of organisms in marine, aquatic, and terrestrial ecosystems. Chemicals that are persistent in the environment have the ability to accumulate in organisms and cause physiological changes early in development. One of these persistent chemicals is polychlorinated biphenyls (PCBs). A significant congener of PCBs is PCB153, which is ortho-substituted and shown to persist within the food chain. As a lipophilic molecule, PCB153 is found in fat stores and can be exposed to children before birth. However, the developmental effects of PCB153 are not well known. Studies have shown that exposure to PCB153 caused genes associated with the circadian rhythm to be differentially expressed. After 5 days of exposure to 1 μM PCB153, circadian behavior is disrupted in zebrafish. The aim of this study was to determine the significant developmental windows of exposure that were necessary to create an effect in circadian behavior of zebrafish larvae. Zebrafish were used as a model organism due to their transparent embryos and quick development. There was one experimental treatment (1 μM PCB153) and a control (DMSO). Zebrafish were exposed to treatments from 4-24 hpf (hours post fertilization), 4-48 hpf, 4-72 hpf, and 4-120 hpf. Behavior assays were done after 5 days post fertilization using Noldus DanioVision. Exposure to 1 μM PCB153 for a minimum of 4-72hpf demonstrated similar circadian behavior disruption to data from 4-120hpf exposure. Quantitative PCR assays were done to confirm previous RNAseq data showing differential expression of genes associated with the circadian rhythm in PCB153 exposed zebrafish. We are currently conducting studies to determine whether PCB153 exposure affects circadian pattern of expression of clock and period genes.