The Optic cup is actively shape programmed by independently patterned apical forces

During morphogenesis, initially flat tissues often must transition into complex 3D shapes, reminiscent of shape-programmable systems in physics and engineering. One key question in developmental biology and physics alike is therefore how distinct mechanical inputs interact to produce the correct shape. To investigate this, we here study the onset of optic cup invagination during vertebrate eye development, combining 3D shape analysis, perturbation experiments, and physical modelling inspired by shape-programmable materials. We find that basal invagination is initiated at the apical surfaces through active, patterned cell behaviours. These behaviours generate in-plane strain patterns reshaping the apical surface and thereby bending the tissue basally. Surprisingly, this means that basal shape initiation is driven by apical dynamics. While retinal pigmented epithelium and neuroepithelium exhibit distinct shape transitions, these are temporally coordinated to jointly shape the optic cup. These findings highlight that 3D shape can emerge from local apical activity of two coordinated patterns.