Mechanically driven checkerboard patterning of the intestinal crypt

The intestinal crypt consists of two cell types: Stem cells are neatly interspersed with the niche-maintaining Paneth cells that support them in a so-called checkerboard pattern, effectively maxizing the Paneth-Stem cell surface. This pattern is generally thought to be established through a cell signaling mechanism called lateral inhibition, where Paneth cells inhibit the Paneth fate in their neighbors. Indeed, lateral inhibition is responsible for similar checkerboard patterns throughout animal development. In contrast, we find that pattern formation through lateral inhibition is impossible in the intestinal crypt. During long term live imaging of organoids, we see that the constant stem cell divisions disturb the patterning faster than lateral inhibition can establish it. Instead our automated cell tracking data suggests that neighboring Paneth cells actively separate from each other. We validate this hypothesis by disturbing the patterning by targeted photo-ablation, and following pattern reestablishment. In these experiments we indeed see fast shrinking of Paneth-Paneth interfaces and uncover major differences between the mechanical properties of stem and Paneth cells. Using computational models of organoid mechanics, we conclude that it are these differential mechanical properties that give rise to the checkerboard-like pattern. Our research thus establishes a new mechanically-driven way to form checkerboard-patterns that, in contrast to lateral inhibition, can function in highly dynamic environments.