Intestinal Phenotypes of Zebrafish Enteric Nervous System Double Mutants
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Date
2019
Authors
Carroll, Lillian Alice
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
The enteric nervous system (ENS) innervates the intestine and regulates the dynamic intestinal environment. In humans, ENS reduction causes Hirschsprung disease (HSCR), a genetically complex disorder that results in intestinal dysmotility and, in many patients, intestinal inflammation. The zebrafish is an excellent model in which to study the relationship between inflammation and genes linked to HSCR. Zebrafish homozygous for a mutation in one HSCR gene, sox10, have fewer enteric neurons and develop microbiota-dependent intestinal inflammation. Zebrafish homozygous for a mutation in another HSCR gene, ret, also have fewer ENS neurons but do not exhibit increased intestinal inflammation. To investigate the opposing intestinal inflammation phenotypes of sox10 and ret mutants, I analyzed intestinal phenotypes of sox10;ret double mutants. Because sox10 acts early in neural crest cells that form the ENS and ret acts later, within ENS cells themselves, I hypothesized that intestinal inflammatory phenotypes of sox10;ret double mutants would resemble those of sox10 mutants. To test this hypothesis, I quantified intestinal inflammation in sox10;ret double mutants by counting intestinal neutrophils and enumerating intestinal bacteria and recently-proliferated intestinal epithelial cells. Surprisingly, I observed a wild-type (WT) neutrophil abundance phenotype in sox10;ret mutants, suggesting that a cell type outside of the ENS is involved in determining the intestinal inflammatory phenotypes of ENS mutants. This result led me to investigate intestinal enterochromaffin cells, which express ret but not sox10. I hypothesized that sox10;ret double mutants would exhibit the same decreased enterochromaffin cell phenotype as ret mutants. However, sox10;ret mutants had more enterochromaffin cells than ret mutants and were similar to WT. This result prompts further exploration of potential interactions between the sox10 and ret genes to gain insights into how these genes interact to regulate intestinal development and the role of the ENS in the maintenance of intestinal health.
Description
49 pages
Keywords
Biology, Zebrafish, Intestine, Development, Nervous System, SOX10 Gene