Browsing by Author "Baker, Phillip Austin"

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    Investigation of Enteric Neural Crest Cell Differentiation, Proliferation Dynamics and Hirschsprung Disease Manifestation During Zebrafish Enteric Nervous System Development
    (2022-04-22) Baker, Phillip Austin; Uribe, Rosa A; Wagner, Dan S
    The enteric nervous system (ENS) is a vast intrinsic network of neurons and glia within the gastrointestinal tract that is largely derived from enteric neural crest cells (ENCCs) that emigrate into the gut during vertebrate embryonic development. Study of ENCC migration dynamics and their genetic regulators provides great insights into fundamentals of collective cell migration and nervous system formation and are a pertinent subject for study due to their relevance to the human congenital disease, Hirschsprung disease (HSCR). To accomplish these studies contained within my thesis, I used the zebrafish model to investigate early enteric nervous system development in its endogenous context. My first study set out to bridge our gap in understanding between zebrafish and mammalian enteric nervous system cell diversity and structure. For this investigation, I utilized immunohistochemical detection of axonal and glial cell profiles in the larval gut to reveal novel details about zebrafish ENS architecture and maturation. Specifically, I observed that the zebrafish larval enteric plexus is histologically distinct by 7 dpf and contains axon and glial cell profiles that encircle the intestinal epithelium, the details of which had yet to be described in zebrafish. My second study profiling the transcriptomes of migratory ENCCs uncovered evolutionarily conserved and novel transcriptional signatures of differentiating enteric neuron cell types, thereby expanding our knowledge of ENS development. I further detected the presence of opioid receptor transcripts within the ENS at 68–70 hpf, a time when immature enteric neurons are continuing to migrate and pattern within the developing embryo. This discovery of opioid transcripts, oprl1 and oprd1b in migrating enteric neuroblasts, represents the earliest stage in which they have been shown to be expressed within the early developing ENS. Lastly, my final study in which I performed in toto imaging of ENS development in heterozygotic deficient ret mutant zebrafish led to novel findings pertaining to ENCC migration and proliferation dynamics in a Hirschsprung Disease relevant context. Specifically, I discovered proliferation dependent migration behaviors downstream of Ret. These findings suggest that Ret signaling may function to regulate maintenance of a stem-state in enteric neural progenitors.