Extended Data Figure 4: Astral microtubules contact Mud at the TCJ.
From: Epithelial tricellular junctions act as interphase cell shape sensors to orient mitosis
a, a′, Time-lapse images of ChFP–Mud (green in a and top panels of a′, white in bottom panel of a′) and of Jupiter–GFP (red in a and top panels of a′, white in middle panel of a′) in dividing cells (n = 11) in the Drosophila pupal notum tissue. The panels in a′ are magnifications of the boxed region in a. Yellow arrow indicates an astral microtubule that contacts ChFP–Mud at the cortex and shortens concomitant to the spindle pole movement towards the TCJ and spindle rotation. The dashed line corresponds to the initial spindle orientation and the solid lines correspond to its orientation at the final time point (see Supplementary Video 2). Similar results were obtained in cells expressing GFP–Mud and αTub–RFP to label the microtubules (data not shown). b, Schematic of the laser-ablation assay used to estimate the origin and magnitude of forces on astral microtubules required for spindle orientation in the Drosophila pupal dorsal thorax epithelium. Upon ablation (red lines, top), pulling forces (green arrows, left column) or pushing forces (green arrows, right column) yield recoil away (grey arrow, left column) or towards the ablation site (grey arrow, right column), respectively. Scale bars, 1 μm.
