Brain Health Consortium Seed Grant (Bryan Fowler): Vagal Innervation of the Stomach and Duodenum

Brain Health Topic:
 Vagal signaling between the gut and the CNS contributes to appetite regulation. inflammation and immune
 responses. gastrointestinal motility. nausea. emesis. and even mood1-6
 . Therefore. vagal neurons are an
 attractive target for medical interventions. Since vagal signaling may be modulated within the digestive tract.
 drugs need not cross the blood-brain barrier. reducing potential side effects and toxicity. To eventually identify
 potentially drug-able targets within the vagus to improve mental and digestive health. our aim is to identify
 markers for subsets of vagal sensory neurons involved in chemosensation within the stomach and duodenum.
 Proposed Research:
 Recently. a single-cell RNA-seq transcriptome of the neuronal populations within the vagus has been
 published 7
 . This transcriptome provides educated guesses as to the physiological functions for some cell type
 clusters. As these data were collected from dissociated single-cell suspensions. we lack any indication of which
 peripheral targets these neurons once innervated (stomach. lungs. heart. intestines. etc.) or which ganglion (left
 vs. right) the neurons came from. There is evidence for differences between neurons of the left and right
 ganglion: only neurons of the right vagus project to dopaminergic cells within the Substantia Nigra 8
 . We
 hypothesize that nutrient and irritant signaling within the stomach and duodenum is mediated by different
 subsets of vagal sensory neurons. To identify subsets of neurons innervating the stomach or duodenum. we will
 inject retrograde AAV vectors driving the expression of GFP and RFP into the stomach and duodenum.
 respectively. We can then identify neurons innervating these targets by the presence of the virally transduced
 mRNA. To test for lateralization of cell types between left and right vagus we will use Multi-seq 9 to label both
 ganglia. This tag will be identifiable following scRNA-seq. identifying individual cells as having been from the
 left or right vagal ganglion. After data analysis. we will be able to accomplish two major objectives:
 Objective 1: Identify innervation targets of vagal neurons by cell type.
 Objective 2: Identify if specific cell types are located within either the left or right vagal ganglion.
 Potential Significance:
 In future experiments. we will use this data to identify genetic markers of vagal neurons to label. image. and
 manipulate neuronal populations responsible for signaling the presence of nutrients or toxins in a meal. This
 will lead to a better understanding of the circuits by which the vagus promotes and/or inhibits digestion.