EMB is essential for enteric nervous system development mediated by PI3K signaling

The enteric nervous system (ENS), which arises from enteric neural crest cells (ENCCs), plays important roles in many aspects of gastrointestinal tract function, including motility, secretions, blood flow and hormone release. Defects in ENS development could lead to a broad range of disorders, including Hirschsprung's disease (HSCR), which is characterized by missing nerve cells in the distal segment of the colon. Here, we identify EMB as an evolutionarily conserved regulator of ENS development.

We first examined EMB expression in human and mouse intestines using scRNA-seq data and immunofluorescence staining. To investigate its role in ENS development, we constructed Emb-knockout zebrafish and mouse models. To explore the underlying mechanisms, we focused on ENCCs and analyzed their proliferation and migration using migration assays in explant guts and organoid cultures. Finally, we assessed rare EMB variants in a cohort of HSCR patients.

In zebrafish, loss of emb leads to a decrease number of enteric neurons and impaired intestinal transit ability. In mice, knockout of Emb causes HSCR-like phenotypes and defects. In vitro experiments, including explant mouse gut and organoid cultures, show that EMB is required for both the proliferation and migration of ENCCs. Mechanistically, EMB binds to and recruits the phosphatase complex PP2A to the cellular membrane to facilitate the activation of PI3K-AKT pathway, thereby promoting ENCCs development. Indeed, application of PI3K or AKT agonists partially restores the ENS developmental defects in zebrafish emb mutants. Furthermore, rare variants of EMB may potentially contribute to the pathology of HSCR in humans.

EMB is required for ENS development by regulating the proliferation and migration of the ENCCs. Mechanistically, EMB recruits PP2A to the cell membrane, reducing cytoplasmic dephosphorylation activity and promoting the activation of the PI3K signaling pathway.