UCLA

The enteric nervous system (ENS) is essential for normal gastrointestinal function, and defects in the ENS define several difficult to treat conditions ranging from Hirschsprung disease to esophageal achalasia. While the developmental origin of the ENS from neural crest cells is well understood, there is conflicting evidence regarding postnatal enteric neurogenesis and neuronal homeostasis. Using zebrafish as a model due to its simplified ENS which is amenable to live-imaging, we sought to explore the origin of enteric neurons that arise in post-embryonic life in both normal development and upon injury, and tested effects of the 5HT4 receptor agonist, prucalopride, in this process.

To assess for putative resident neuronal precursors, we performed in situ hybridization, immunohistochemistry, and confocal imaging of transgenic lines (live larvae and dissected adult intestine). To detect post-embryonic enteric neurogenesis, we photoconverted enteric neurons within the intestines of a Phox2b-kaede transgenic line such that all resident neurons turned from green to red. We then performed live time-lapse imaging to assess for the emergence of new, green-only neurons. In other experiments, resident enteric neurons were removed using two-photon laser ablation. To follow the potential contribution of neural crest-derived cells to the gut, lineage tracing was performed with neural tube injections of a lipophilic dye as well as with an inducible Sox10-Cre transgenic line. Lastly, post-embryonic zebrafish were exposed to prucalopride to test this drug’s effect on enteric neurogenesis both during normal development and after injury.

Our results suggest that the post-embryonic zebrafish intestine lacks resident neurogenic precursors, and indeed appears to have no enteric glia. Despite this, enteric neurogenesis persists post-embryonically both during normal development and after injury. Our data suggest that new enteric neurons arise from trunk neural crest-derived Schwann cell precursors that migrate along nerves to the intestine. Prucalopride increases enteric neurogenesis in normal development as well as after injury if exposure occurs prior to injury. This study provides evidence that SCPs originating from the trunk neural crest mediate this neurogenesis in post-embryonic life and can be pharmacologically manipulated, which could have significant clinical implications for several enteric neuropathies.