Cardiovascular Gene Expression Profiles of Dioxin Exposure in Zebrafish Embryos

Abstract

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental contaminant that causes altered heart morphology, circulatory impairment, edema, hemorrhage, and early life stage mortality in fish. TCDD toxicity is dependent, in large part, on the aryl hydrocarbon receptor (AHR), but understanding of the molecular mechanism of cardiovascular embryotoxicity remains incomplete. To identify genes potentially involved in cardiovascular effects, we constructed custom cDNA microarrays consisting of 4896 zebrafish adult heart cDNA clones and over 200 genes with known developmental, toxicological and housekeeping roles. Gene expression profiles were obtained for 3-day-old zebrafish after early embryonic exposure to either 0.5 or 5.0 nM TCDD. In all, 516 clones were significantly differentially expressed (p < 0.005) under at least one treatment condition; 123 high-priority clones were selected for further investigation. Cytochromes P450 1A and 1B1, and other members of the AHR gene battery, were strongly and dose-dependently induced by TCDD. Importantly, altered expression of cardiac sarcomere components, including cardiac troponin T2 and multiple myosin isoforms, was consistent with the hypothesis that TCDD causes dilated cardiomyopathy. Observed increases in expression levels of mitochondrial energy transfer genes also may be related to cardiomyopathy. Other TCDD-responsive genes included fatty acid and steroid metabolism enzymes, ribosomal and signal-transduction proteins, and 18 expressed sequence tags (ESTs) with no known protein homologs. As the first broad-scale study of TCDD-modulated gene expression in a non-mammalian system, this work provides an important perspective on mechanisms of TCDD toxicity.

Development of the morpholino gene knockdown technique in Fundulus heteroclitus: A tool for studying molecular mechanisms in an established environmental model

“…Gene knockdown continues well into the larval stage, as seen in zebrafish. One additional point to note with regard to morpholino duration is that the gene we selected for evaluation of MO technologies in Fundulus (CYP1A) is highly inducible (Handley-Goldstone et al, 2005;Timme-Laragy et al, 2007). As such, it provides a very rigorous test of the duration of morpholino action.…”

Functional properties of the four Atlantic salmon (Salmo salar) aryl hydrocarbon receptor type 2 (AHR2) isoforms

“…Heart was also identified as the primary site of AHR2β expression. Several studies have identified the heart as a principal target organ for TCDD toxicity in fishes, resulting in altered gene expression and cardiovascular impairments (Carney et al 2006;Handley-Goldstone et al 2005;Hornung et al 1999;Spitsbergen et al 1991). The expression of all four salmon AHR2 forms in heart could indicate that this organ is at higher risk of toxicity after TCDD exposure.…”

Retene causes multifunctional transcriptomic changes in the heart of rainbow trout ( Oncorhynchus mykiss ) embryos

“…They are groups that may have large and divergent downstream effects, and an early response to AhR agonists is typically seen in genes belonging to these GO groups (Fletcher et al, 2005,Handley-Goldstone et al, 2005,Carney et al, 2006. Furthermore, the effect of AhR agonists on multiple signaling cascades is consistent with previous transcriptomic studies in the early life stages of zebrafish (Handley-Goldstone et al, 2005,Carney et al, 2006.…”