Project description Gut epithelium is the principal site in which neural, immune, microbial and dietary factors interact. This multi-system interaction critically regulates whole-body physiology including metabolism, immunity, and neurodegenerative diseases. At the basis of this interaction is the healthy and balanced gut epithelium. As one of largest exposed surfaces of the body, billions of cells are shed from the human gut epithelium every day. These lost cells are replenished by intestine stem cells to maintain gut homeostasis and functions. Deciphering the regulatory mechanisms of gut homeostasis is therefore important for understanding normal gut functions as well as gastrointestinal disorders including colorectal cancer. Although genetic programs that control gut homeostasis have been extensively studied, very little is known about how mechanical forces–– generated by gut peristalsis and food passing could regulate intestine stem cell behavior. Here, we use the adult Drosophila midgut as a simple but robust system to dissect how shear stress as a natural force of the gut lumen could regulate gut homeostasis and gut homeostasis. Our pilot studies have made novel findings that shear stress activates Ca2+ signals in enteroendocrine cells through the Ca2+ channel TrpA1. Moreover, disruption of TrpA1 markedly reduced intestine stem cell proliferation. Based on these exciting results, we hypothesize that: 1) shear stress regulates gut homeostasis through TrpA1-dependent activation of EEs and subsequent release of signaling molecules from EEs, 2) shear stress activates TrpA1 by regulation of the intrinsic property of cell membrane. In this collaborative project, we plan to test these hypotheses by leveraging the power of Drosophila genetics and combining it with new mechanobiological analysis and stem cell biology. Because TrpA1 is expressed in mammalian EEs, and because we find that mammalian TrpA1 is also activated by shear stress, our proposed studies will likely have a broad impact in gut physiology including that of mammals.