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| Poster #110 Mammalian chemosensory bile acid detection supports gut microbiome evaluation |
| Varun Haran1, Mari Morimoto1,2, Leena S.F. Rouyer1, Julian P. Meeks1 1University of Rochester, Rochester, NY, United States 2City College of New York, New York, NY, United States |
The rodent accessory olfactory system (AOS) plays a key role in detecting environmental chemosignals and guiding social and survival-oriented behaviors. Bile acids found in mouse feces act as AOS chemosensory ligands, activating vomeronasal sensory neurons (VSNs) and potentially serving as mammalian pheromones and kairomones. However, only a small number of molecules in this class of AOS ligands have been studied to date. Using live volumetric Ca2+ imaging, we screened naturally occurring bile acids for their ability to activate peripheral vomeronasal sensory neurons (VSNs). We found that taurine-conjugated bile acids (tauro-BAs), including taurine-conjugates of cholic acid, deoxycholic acid, lithocholic acid, and chenodeoxycholic acid (TCA, TDCA, TLCA, TCDCA, respectively), activate larger populations of VSNs at sub-micromolar concentrations than their unconjugated and glycine-conjugated counterparts. Tauro-BAs were not detected in conventional mouse fecal extracts, but they were present in germ-free mouse feces extracts. VSN Ca2+ imaging confirmed that the tauro-BA ligands identified in germ-free mouse feces activated a large proportion of germ-free feces-responsive VSNs. Importantly, germ-free and conventional mouse fecal extracts activated almost exclusively non-overlapping populations of VSNs. To investigate the impact of tauro-BAs on behavior, we studied TDCA, which displayed particularly strong potency in Ca2+ imaging experiments. Fecal extracts spiked with TDCA acted as an aversive stimulus in both non-social and social behavior contexts. These studies establish that the gut microbiome plays an essential role in the secretion of social chemosignals and that VSN detection of taurine-conjugated bile acids supports gut microbiome evaluation. |