α-cat-ΔM1 monolayers show enhanced binucleation rate over wild-type and other α-cat mutants. (A) Confocal en face view (maximum z-projection; grayscale inverted) images showing GFP-α-catΔM1 expressing cells exhibit polyploidy after 12 days grown on filters. GFP-α-cat (green) and LZTS2 (magenta), multinucleated cells (outlined, yellow dashed line). Representative images from four independent experiments are shown. Scale bar, 40 μm. (B) Quantification of multinucleation rate in different GFP-α-cat constructs expressing MDCK α-cat KO cells. Two-tailed unpaired t test, **P < 0.01, ***P < 0.001, ****P < 0.0001. Graph indicates mean ± SD. Data from three independent experiments. (C) The rectangular regions framed in white in A are enlarged to show detail. Scale bar, 20 μm. Yellow arrows denote bi- or multinucleated cells. (D) Model: LZTS2 is a mechanosensitive target of α-catenin required during normal cell division. α-cat M-domain unfurling enhances LZTS2 proximity. Direct binding between α-cat and LZTS2 has not been formally tested. (E) α-cat mechanosensitive mutants used in this study favor recruitment of LZTS2 to adherens junctions (right). Cytokinesis failures seen for these mutants occur either by limiting LZTS2 enrichment at the midbody region of the intercellular bridge, or by sequestering LZTS2 from possible microtubule-directed roles in the cytoplasm. Schematic designed with BioRender.