Date of Award

1-1-2007

Embargo Period

1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

Margaret L. Kirby

Second Advisor

Robert Gourdie

Third Advisor

Edward L. Krug

Fourth Advisor

Steve Kubalak

Fifth Advisor

David Sedmera

Sixth Advisor

Roger Markwald

Abstract

The zebrafish is becoming an almost ubiquitously accepted model for the study of comparative developmental biology, its utility coming to rival that of the fruitfly, frog, chick and mouse. Unfortunately, however, it is widely held belief that the zebrafish cardiac outflow tract makes it unusual as a model of comparative cardiogenesis and this is based, in part, on the report that bulbus arteriosus undergoes a developmental myocardium-to-smooth muscle phenotypic transition. This would imply that the zebrafish may be poorly suited to the study of human cardiac outflow abnormalities. While the use of chamber-specific molecular markers has allowed extensive characterization of the development of the zebrafish atrium and ventricle, the lack of any bulbus-specific markers has meant that this structure specifically and the cardiac outflow tract more generally are poorly characterized and quite possibly misunderstood. I have discovered that the fluorescent nitric oxide indicator, 4,5-diaminofluorescein diacetate (DAF-2DA), specifically labels the bulbus throughout development and into adulthood. Therefore, using DAF-2DA and an immunohistochemical approach, I present a characterization of bulbus arteriosus development and demonstrate that no such phenotypic transition occurs, that, contrary to current thinking, aspects of zebrafish outflow tract development are evolutionarily conserved, and that the bulbus should not be considered a chamber, being more akin to the arterial trunk of phylogenetically more advanced vertebrates. Furthermore, in an attempt to validate the zebrafish as a model to understand systemic cardiac outflow malformations, I present a characterization of an extreme phenotype induced by a model environmental contaminant, PCB126, which causes outflow- and ventricle-specific dysmorphogenesis in this species. Such contaminants have also been casually linked to a human congenital cardiovascular malformation known as hypoplastic left heart syndrome, a condition of poorly understood etiology that effects the systemic ventricle and causes a suite of arterial trunk malformations. I introduce the potential for a paradigm shift in our understanding of such contaminants by demonstrating a novel link to cell cycle checkpoint protein, p53, and thus provide evidence that the zebrafish may be an ideal model by which human congenital malformations specifically affecting the systemic cardiac outflow may be understood.

Rights

All rights reserved. All rights reserved. Copyright is held by the author.

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