2026 年 21 巻 3 号 p. 26-00144
The three-dimensional morphogenesis of epithelial tissues is governed by robust physical mechanisms. Examples of this process include the folding of insect imaginal discs and cerebral convolutions. Reaction-diffusion theories have historically focused on chemical aspects to explain these structures. However, recent mechanobiological studies indicate that geometric constraints are equally pivotal. In this study, we investigate how the intrinsic curvature of a tissue substrate directs the buckling morphogenesis driven by cell division. Using a three-dimensional cell-center model, we simulated epithelial proliferation on spherical and ellipsoidal surfaces. Our results reveal a curvature-dependent mode transition on spherical surfaces. Specifically, the buckling pattern shifts from a dot-like state to a labyrinthine state as the radius increases. Crucially, we observed that tissue geometry regulates the spatial orientation of the buckling patterns. On prolate ellipsoids, the tissue spontaneously generates “Yoshimura pattern-like folds” (zig-zag patterns). This topological structure is similar to the folding of beetle horns. Conversely, on oblate ellipsoids, the tissue robustly forms concentric ring patterns. This morphology resembles the folding of Drosophila leg discs. We propose that this physical pattern selection arises from geometric confinement rather than solely from molecular pre-patterning. Specifically, the high-curvature poles of prolate ellipsoids generate effective axial compression. In contrast, the high-curvature equator of oblate ellipsoids induces radial compression. These findings suggest that morphogenetic outcomes are robustly “encoded” in the macroscopic geometry of the developing primordium. Therefore, this macroscopic geometry serves as a geometric bifurcation parameter to regulate the transition between ordered and disordered patterns.
