Tissue and cellular architecture in embryos with non-deformable nuclei. (A) 3D reconstruction of cell membranes (pink) and nuclei (blue) from live imaging data of control (luciferase shRNA, top panel) and kuk shRNA (bottom panel) embryos. The slanted view shows kuk embryos with round deformation-resistant nuclei and smoother nuclear surfaces (left), side view reveals that kuk nuclei accommodate themselves in different apical–basal planes and partially deform cell shapes (mid), and the top view shows nuclear packing and potential overlaps (right) compared with the control (related to Video 5). (B) Still images from kuk embryos showing greater dispersion of nuclei, indicated by cell cross-sections without nuclei (marked by asterisks). These rounded nuclei resist deformation even while cell shapes are becoming increasingly irregular. Image slice from ∼11 µm below the apical surface. (C) Measurement of nuclear sphericity in control and kuk embryos during GBE. (C′) SD of nucleus sphericity for control (red) and kuk (dark blue) embryos showing kuk nuclei resisting deformation throughout GBE. The light blue background indicates GBE. For C and C′, n = 605 control nuclei and n = 876 kuk nuclei from k = 3 embryos for each background. (D) Orthogonal view of control (luciferase) and kuk nuclei showing greater dispersion in kuk embryos. (E) Probability of absolute position of nuclear midplane along the apical–basal axis at 0 and 20 min of GBE for control (luciferase) and kuk embryos; for control, n = 116 nuclei for 0 min and n = 81 nuclei for 20 min, for kuk, n = 81 for 0 min and n = 79 for 20 min from k = 1 embryo for each background. For B and D, scale bar = 5 and 10 μm, respectively. Statistical significance in C was calculated using Student’s t test. ****P < 0.0001.