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

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 <i>Caenorhabditis elegans</i> FoxA homolog, PHA-4, reach beyond its previously described pioneer factor roles in patterning the foregut. Through the engineering of neuron-specific <i>cis</i>-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.