(26a) An Auto-Catalytic Cell Intercalation Mechanism to Understand Tissue Elongation during Morphogenesis

Within the topic of morphogenesis, tissue elongation is a necessary process in all metazoans to shape and implement their body plans. Besides recent advances the mechanisms underlying tissue elongation are not fully understood. For example, in the particular case of the limb, it has been shown that tissue elongation cannot be explained by either a localized proliferation of cells or their oriented divisions and, surprisingly, the tissue elongates perpendicular to the direction along which cell grow. Here we propose a mechanism of tissue elongation to address this conundrum. Our model couples the mechanical properties of cells with the concept of positional information to modulate the former in a location-dependent manner. To illustrate our proposal, we use the French flag model (morphogen gradient thresholds) as the mean used by cells to “know” their relative positions within a primordium. Our numerical simulations are based on the so-called vertex model that describes the energetics of tissues and we use elasticity theory to analyze different properties of our simulations. In this context, we show that if the cell-cell adhesion is modulated as a function of the location of cells within a primordium, an auto-catalytic cell intercalation process develops and the tissue elongates. Moreover, our results reveal that cells grow perpendicular to the elongation direction as experimentally reported. Altogether, our results shed light on the tissue elongation problem and paves the way to better understand morphogenesis.