Primary cilia dynamics in pancreatic duct network development

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Pancreatic cysts have been reported in a subset of ciliopathies, but the function of primary cilia in the pancreas is poorly understood, particularly in the fetus, when the cystic phenotypes are initiated. During development, ciliated progenitors of the exocrine and endocrine cells form the walls of the pancreatic duct network. This network remodels from a mesh to a tree optimized for fluid transport, presumably in response to flow. By analogy with other systems, we hypothesize that the primary cilia on the progenitors and cilia flow sensing play an essential role in the morphogenesis of the pancreatic ducts during development. Using complementary expertise in pancreas development (Grapin-Botton) and mathematical modeling of biological hydrodynamics and signaling (Friedrich), we propose to use the pancreas as a new model to understand the role of primary cilia dynamics in tubular network formation across time-scales. At the (sub)second time scale, we will test whether cilia are flow sensors in pancreatic ducts and characterize cilia flow sensing in terms of a quantitative input-output relationships that link the magnitudes of both steady and oscillatory external fluid flow to dynamic cilia signaling, focusing primarily on calcium. We further hypothesize that flow may lead to changes in the cilia proteome, as observed for chemical signaling but so far unexplored for flow sensing. To gain mechanistic insights into the cilia proteome in pancreatic progenitors and changes in the intracilliary protein composition upon stimulation, we will use proximity labelling using NPHP3 as a bait. At the time scale of days, we will systematically investigate the proportion of cells with cilia, their length and orientation and map this morphometric data on skeletonized ductal network structures. This will enable us to establish whether cilia presence and length change with developmental time, duct diameter, and position in the pancreas duct network. Finally, we will connect the insight on ciliary mechanical sensing in the pancreas at the (sub)second scale to the physiologically relevant process of pancreas duct network remodeling during embryonic development, which takes place over days. To do so, we will monitor the flow in vivo and impose it in perfused pancreas organoids, investigating whether it triggers remodeling. Taken together, our work will offer mechanistic insights into mechanical sensing by primary cilia in the pancreas. In addition, our results will lay the foundation to unravel the implications of impaired pancreatic cilia signaling in ciliopathies.