Functional development of the enteric nervous system in larval zebrafish

Abstract

The enteric nervous system (ENS) controls various functions of the gastrointestinal tract and interacts with the gut microbiome. It communicates with the brain in multiple ways, through endocrine and immune signalling, and direct neuronal signalling via the vagus nerve. Patients with psychiatric (anxiety, depression) or neurological disorders (autism spectrum disorders, Parkinson’s disease) often show gastrointestinal comorbidities. Furthermore, several correlative studies have implicated the gut-brain axis in effects on behaviour and cognition. From these studies, the ENS is the interface between gut, microbiome and brain, however the causal links between the different factors remain elusive. This provides the motivation to study the functional development of the ENS in zebrafish larvae and investigate the influence of the gut microbiome on its development. This might prove to be the first step leading to the dramatic effects on behaviour that are observed at later time points. In this project, we started out with the first step wherein we characterized the functional development of the ENS in wildtype zebrafish larvae. We employed light-sheet microscopy to image the activity of the ENS in 2-7 days post fertilization larvae using a genetically encoded calcium indicator, GCaMP6s. We examined the properties of growth of the ENS network, gained insights into the developmental trajectory it follows and characterised the patterns of activity it exhibits, which correspond to the waves of peristalsis that it brings about. This is the first-ever study of its kind and serves as the first step towards understanding the functional development of the ENS.