Genetic Encoding of an Esophageal Motor Circuit

Motor control of the striated esophagus originates in the nucleus ambiguus (nAmb), a vagal motor nucleus which also contains upper airway motor neurons and parasympathetic preganglionic neurons for the heart and lungs. We disambiguate nAmb neurons based on their genome-wide expression profiles, efferent circuitry, and ability to control esophageal muscles. Our single-cell RNA-sequencing analysis predicts three molecularly distinct nAmb neuron subtypes and annotates them by subtype-specific marker genes: Crhr2, Vipr2, and Adcyap1. Mapping the axon projections of the nAmb neuron subtypes reveals that Crhr2nAmb neurons innervate the esophagus, raising the possibility that they control esophageal muscle function. Accordingly, focal optogenetic stimulation of cholinergic Crhr2+ fibers in the esophagus results in contractions. Activating Crhr2nAmb neurons has no effect on heart rate, a key parasympathetic function of the nAmb, whereas activating all nAmb neurons robustly suppresses heart rate. Together these results reveal a genetically defined circuit for motor control of the esophagus. Overall design: Single-nuclei RNA-Seq (sNuc-Seq) analysis of 288 samples isolated from the nucleus ambiguus of 27 week old Chat-IRES-cre male mice (C57Bl6/j background) 4 weeks after injection of AAV-DIO-H2b-mCherry into the ventrolateral medulla.