A New Transgenic Tool to Study the Ret Signaling Pathway in the Enteric Nervous System.

The receptor tyrosine kinase Ret plays a critical role in regulating enteric nervous system (ENS) development. Ret is important for proliferation, migration, and survival of enteric progenitor cells (EPCs). Ret also promotes neuronal fate, but its role during neuronal differentiation and in the adult ENS is less well understood. Inactivating RET mutations are associated with ENS diseases, e.g., Hirschsprung Disease, in which distal bowel lacks ENS cells. Zebrafish is an established model system for studying ENS development and modeling human ENS diseases. One advantage of the zebrafish model system is that their embryos are transparent, allowing visualization of developmental phenotypes in live animals. However, we lack tools to monitor Ret expression in live zebrafish. Here, we developed a new BAC transgenic line that expresses GFP under the promoter. We find that EPCs and the majority of ENS neurons express during ENS development. In the adult ENS, GFP neurons are equally present in females and males. In homozygous mutants of and -another important ENS developmental regulator gene-GFP ENS cells are absent. In summary, we characterize a transgenic line as a new tool to visualize and study the Ret signaling pathway from early development through adulthood.