Coordination of villus formation during embryonic development is essential for the correct formation and function of the adult intestine. In the mouse, villus emergence is preceded by the formation of mesenchymal signalling clusters, but what triggers these mesenchymal clusters to form in a precise pattern is currently unclear. Recent data from the chick suggest that mechanical forces are at play, but whether this applies to mammalian species has not yet been addressed. Now, on p. , Deborah Gumucio and colleagues report that, unlike in chick, mouse villification is not patterned by mechanical forces but instead is driven by Bmp signalling. The authors demonstrate how different patterns of cluster distribution and villus outgrowth can be generated simply by changing the concentration of Bmp ligands or Bmp modulators that are expressed by the clusters, or by altering Bmp signal transduction. Indeed, epithelial deformation follows cluster formation in the mouse, whereas the opposite is true in the chick, highlighting the distinct villus patterning processes in the two species. Interestingly, the authors use mathematical modelling to demonstrate that their findings are consistent with Turing field patterning, adding mammalian villus formation to the list of Turing system-patterned developmental processes.
