Nutrtional Genetics during Zebrafish Development
Date of Award
Doctor of Philosophy (PhD)
Structural birth defects are a major source of morbidity and mortality and result from detrimental interactions of genetic susceptibilities and environmental circumstances, with nutritional intake representing an important component of environmental variability. As gene products are required for the transport and metabolism of micronutrients while simultaneously relying on micronutrients as cofactors, the interplay of genetic and nutritional factors is complex such that the phenotypic consequences of genetic variation must be interpreted in the nutritional context, and vice versa. Models permitting the experimental manipulation of both nutrition and gene function are necessary to elucidate the effects of genotype on nutritional requirements, though such models are lacking. In these studies we have utilized the zebrafish embryo as a model of copper or oxygen deficiency to identify the genetic, biochemical, and metabolic factors that determine the impact of these deficiencies on developmental processes. Copper deficiency produces a hierarchical and pleiotropic phenotype including loss of melanin pigmentation, an undulating notochord, and neural degeneration. We interrogated a genetic screen for embryos phenocopied by copper deficiency, identifying calamity, a mutant defective in the zebrafish ortholog of the Menkes disease gene (atp7a). Human ATP7A restores copper metabolism in calamity and transplantation experiments reveal that atp7a functions cell autonomously. The gene dosage of atp7a determines the sensitivity to copper deprivation, revealing that specific genetic factors inform the developmental hierarchy of copper metabolism. Oxygen deficiency—anoxia—causes a developmental arrest that is reversible upon the return to normoxia. The duration of viability in anoxia depends on the developmental stage, temperature, and anaerobic metabolic rate. A viable developmental arrest can be recapitulated in normoxia by inhibiting mitochondrial oxidative phosphorylation, revealing that arrest is primarily a response to energy deprivation. Conditions causing arrest activate the AMP-activated protein kinase pathway. Furthermore, arrest can occur before the midblastula transition independent of zygotic transcription, though the yolk syncytial nuclei are uniquely unregulated by energy status at these early stages. Acute anoxia is also accompanied by characteristic changes in the proteome. Taken together, these studies demonstrate the potential of the zebrafish embryo to reveal the interactions of genetic and nutritional variation in the dynamic processes of development.
Chair and Committee
Susan Dutcher, Stephen Johnson, Louis Mulgia, Joshua Rubin, James Skeath
Mendelsohn, Bryce Abram, "Nutrtional Genetics during Zebrafish Development" (2010). Arts & Sciences Electronic Theses and Dissertations. 112.