|dc.contributor.author||Handley, Heather Martin||
|dc.description||Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003||en||
|dc.description.abstract||2,3,7,8-Tetrachlorodibenzo-ρ-dioxin (TCDD) is a potent teratogen that impacts the
developing cardiovascular system. Hallmarks of embryonic exposure include cardiac
malformation, impaired circulation, loss of erythrocytes, pericardial and yolk sac edema,
and early life stage mortality. However, the mechanism of TCDD cardiovascular
embryotoxicity is poorly understood. The primary goal of this thesis was to identify
TCDD-responsive genes likely to be involved in processes of toxicity.
We constructed microarrays using cDNA libraries derived from zebrafish embryonic
and adult heart tissue. Embryonic heart arrays were used for protocol development. The
resulting workflow was employed in the production of adult heart microarrays containing
~2800 unique cardiovascular genes.
These arrays were used to establish gene expression profiles of zebrafish embryos
exposed to 1.84±0.42 or 10.74±0.38 ng TCDD/g embryo. Alterations in cardiovascular
gene expression were limited; 44 genes or ESTs were significantly differentially
expressed ≥1.8-fold (p-values ≤5x10-4), and only CYP1A and CYP1B1 were induced >4-
fold. Transcriptional responses to TCDD were highly dose-dependent, and adaptive
responses were a prevalent feature of TCDD-modulated gene expression.
Microarray analyses indicated induction of genes in three major functional classes - xenobiotic
detoxification, sarcomere structure, and energy transfer. TCDD-modulation
of selected genes was verified by RT-PCR. Induction of mitochondrial electron transfer
genes was variable and modest; such induction provides a possible pathway to reactive
oxygen generation and cardiac pathology. Sarcomere genes were generally robustly
induced, but RT-PCR indicated suppression of cardiac troponin T2. The current data
suggest that TCDD causes cardiomyopathy in zebrafish embryos.
Investigation of a TCDD-induced EST cluster led to the discovery of a novel
retroelement, EZR1. EZR1 elements lack genes necessary for autonomous
retrotransposition, but are highly expressed in normal and TCDD-exposed cardiac tissue.
Putative regulatory elements in LTR sequences may account for observed expression
patterns. The function, if any, of EZR1 remains open to speculation.||en||
|dc.description.sponsorship||This research was supported in part by the WHOI Academic Programs Office, an
NSF Coastal Research Traineeship, NIH Superfund Basic Research Program grant
5-P42-ES07381, EPA grant R827102-01-0, and WHOI Ocean Life Institute and Coastal
Ocean Institute grant 39591300.||en||
|dc.publisher||Massachusetts Institute of Technology and Woods Hole Oceanographic Institution||en||
|dc.title||Zebrafish cardiovascular cDNA microarrays : expression profiling and gene discovery in embryos exposed to 2,3,7,8-Tetrachlorodibenzo-ρ-dioxin||en||