# PHA-4/FoxA controls the function of pharyngeal and extrapharyngeal enteric neurons in C. elegans

## TL;DR

This study shows that the PHA-4/FoxA transcription factor is essential for the function of gut-related neurons in C. elegans, both during development and in adulthood.

## Contribution

The study reveals that PHA-4/FoxA is continuously required for the function of multiple types of enteric neurons, beyond its known role in gut development.

## Key findings

- PHA-4/FoxA is required for terminal differentiation and lifelong function of postmitotic enteric neurons in C. elegans.
- PHA-4/FoxA is expressed in extrapharyngeal neurons like AVL, DVB, RIS, and PVT, which control gut behaviors.
- PHA-4/FoxA is the only known transcription factor required for the function of all types of enteric neurons in a nervous system.

## Abstract

In this study, Walker et al. show that the FoxA transcription factor PHA-4 is required for terminal differentiation and function of postmitotic enteric neurons in C. elegans. PHA-4 function goes beyond its pioneer activity during gut development, with continuous expression being a universal requirement for the activity of distinct enteric neurons in controlling various gut behaviors.

FoxA transcription factors pattern gut tissue across animal phylogeny. Beyond their early patterning function, little is known about whether they control the terminal differentiation and/or function of the fully mature enteric nervous system, the intrinsic nervous system of the gut. We show here that the expression and function of the sole Caenorhabditis elegans FoxA homolog, PHA-4, reach beyond its previously described pioneer factor roles in patterning the foregut. Through the engineering of neuron-specific cis-regulatory alleles, Cre-mediated cell-specific knockouts, and degron-mediated, temporally controlled PHA-4/FoxA removal in postmitotic neurons, we found that PHA-4/FoxA is required not only to initiate the terminal differentiation program of foregut-associated enteric neurons but also to maintain their functional properties throughout the life of the animal. Moreover, we discovered novel sites of expression of PHA-4/FoxA in extrapharyngeal enteric neurons that innervate the hindgut (AVL and DVB), a GABAergic interneuron that controls foregut function during sleep (RIS), and a peptidergic neuron (PVT) that we implicate here in controlling defecation behavior. We show that while PHA-4/FoxA is not required for the developmental specification of AVL, DVB, RIS, and PVT, it is required to enable these neurons to control enteric functions. Taken together, PHA-4/FoxA is the only transcription factor known to date that is expressed in and required for the proper function of all distinct types of enteric neurons in a nervous system.