The everting Drosophila wing disc is a shape-programmed material

How complex 3D tissue shape emerges during animal development remains an important open question in biology and biophysics. Although it is well-established that tissue-scale patterns of in-plane cell behaviors can reshape a tissue in 2D, whether and how such patterns could also deform a tissue in 3D remains unclear. Meanwhile, recent advances in materials science, physics, and engineering have enhanced our ability to craft and understand inanimate "shape-programmable" materials capable of undergoing blueprinted 3D shape transformations arising from in-plane gradients of spontaneous strains. Here, we use this conceptual framework to understand eversion of the Drosophila wing disc, a complex 3D tissue reshaping event in wing development. Using quantification of spatial patterns of cell dynamics on an evolving 3D tissue surface, combined with physical modeling and genetic perturbation, we demonstrate that the wing can deform itself in 3D through large-scale patterning of in-plane cellular behaviors, primarily rearrangements. This work shows that concepts from shape-programming can be employed to understand animal tissue morphogenesis and suggests that there exist intricate patterns in nature that could present novel designs for shape-programmable materials. ### Competing Interest Statement The authors have declared no competing interest.