Lineage analysis and identification of novel genes involved in differentiation processes in the zebrafish enteric nervous system

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Intestinal dysfunction is a serious health and societal problem that can make individuals miserable and be expensive to treat. Some intestinal dysfunction results from improper development and function of the enteric nervous system (ENS), which regulates essential gut functions such as motility, blood flow, and homeostasis. The ENS is composed of diverse subtypes of neurons and of glia. Abnormal ENS development causes well-studied human diseases such as Hirschsprung disease, in which the distal gut is uninnervated and nonmotile, and probably also many other human intestinal diseases that are less well-described. Most research using vertebrate genetic systems as models to understand the causes of human ENS diseases has focused on early events in ENS development, such as how ENS progenitors navigate to the gut. However, little is known about later events of ENS development. For example, lineage relationships between progenitors and the differentiated neurons and glia they generate remain elusive and control of the process of ENS differentiation remains largely unknown. I propose to exploit the experimental tractability of zebrafish to 1) investigate lineages that lead to normal development of ENS neurons and glia, 2) analyze the potential of different subpopulations of enteric progenitors, and 3) isolate novel genes involved in this process by characterizing and cloning mutations that affect the generation of ENS neurons. In my project, I will use genetic inducible fate mapping of enteric progenitors and their progeny to generate a comprehensive lineage analysis of the ENS. Genetically labeling the individual subpopulations of enteric progenitors and following their progeny over time will reveal differences in potential of different enteric progenitor subpopulations. The zebrafish model is exceptionally well-suited for lineage tracing studies due to its optical clarity during development which allows tracking of precursors and their derivatives in the intact embryo or larva in vivo. My characterization of ENS mutants and cloning with next-generation high throughput sequencing methods will reveal novel genes and pathways that play a role in ENS development. Understanding the lineages of the ENS as well as finding novel genes that control differentiation processes in the ENS is critical both for basic knowledge and for developing new therapies to treat gut dysfunction resulting from abnormal ENS differentiation.