Title: Mechanochemical bistability of intestinal organoids enables robust morphogenesis

Abstract: How pattern and form are generated in a reproducible manner during embryogenesis remains poorly understood. Intestinal organoid morphogenesis involves a number of mechanochemical regulators, including cell-type specific cytoskeletal forces and osmotically-driven lumen volume changes. However, whether and how these forces are coordinated in time and space via feedbacks to ensure robust morphogenesis remains unclear. Here, we propose a minimal physical model of organoid morphogenesis with local cellular mechano-sensation, where lumen volume changes can impact epithelial shape via both direct mechanical (passive) and indirect mechanosensitive (active) mechanisms. We show how mechano-sensitive feedbacks on cytoskeletal tension generically give rise to morphological bistability, where both bulged (open) and budded (closed) crypt states are possible and dependent on the history of volume changes. Such bistability can explain several paradoxical experimental observations, such as the importance of the timing of lumen shrinkage and robustness of the final morphogenetic state to mechanical perturbations. More quantitatively, we performed mechanical and pharmacological experiments to validate the key modelling assumptions and make quantitative predictions on organoid morphogenesis. This suggests that bistability arising from feedbacks between cellular tensions and fluid pressure could be a general mechanism to allow for the coordination of multicellular shape changes in developing systems.