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Résumé |
Many biological patterns are thought to arise from Turing reaction–diffusion
system, where morphogen interactions generate spatial organization, as seen in
hair, feathers, and other skin appendages. However, not all patterns can be
explained by chemical pre-patterning alone. In this talk, I will present the
mammalian rhinarium (naked nose) as a case where patterning instead emerges from a
mechanical self-organization process. Using volumetric imaging across development,
we showed that polygonal grooves arise from constrained epidermal growth and
buckling, with folds precisely aligned to an underlying network of stiff blood
vessels. Numerical simulations reveal that these vessels act as rigid anchors that
concentrate stress and set the characteristic length scale of the pattern. This
supports the concept of mechanical positional information, whereby tissue
mechanics locally guide an otherwise global self-organized process. Finally,
analyses of genetical clones and pathological cases highlight the roles of
stochasticity and altered material properties, emphasizing how mechanical and
chemical frameworks provide complementary routes to biological pattern formation. |
