Adaptive scans allow 3D-targeted laser-dissection to probe the mechanics of cell sheets

The mechanical actuation of cells by active forces from the cytoskeleton drives tissue morphogenesis. To understand these forces, multicellular laser dissection has become an essential tool for severing tissue locally and inferring tension from the recoil of surrounding structures. However, conventional laser dissection is limited by 2D steering, which is inadequate for embryos and developing tissues that are intrinsically 3D structures. In this study, we introduce a flexible near-infrared (NIR) fs-pulsed laser dissection system that allows for dissection trajectories to proceed in 3D and adapt to the curved surfaces of cell sheets, which are prominent structures in embryos. Trajectories are computed through an unsupervised search for the surface of interest. Using this technique, we demonstrate sectioning of multicellular domains on curved tissue, which was not possible with regular NIR laser scanning. We apply the developed strategy to map mechanical stresses in the imaginal disc of the developing Drosophila wing. Our targeted, adaptive scans can be used in other non-linear processes, such as two-photon fluorescence imaging or optogenetics. Overall, this new laser dissection system offers an innovative solution for studying complex 3D structures and their mechanical properties.