Medioapical Patronin foci depend on actomyosin contraction. (A) ROCK inhibitor disrupts apical Patronin localization in the mesoderm. Images are maximum-intensity Z-projections of mesoderm cells from representative live embryos expressing Patronin::GFP (apical surface) and Gap43::mCH (subapical section) injected with water (top) or Y-27632 (50 mM; bottom). (B) ROCK inhibitor decreases Patronin::GFP apical intensity. Quantification of average maximum Patronin::GFP intensity in a region that spans the apical cortex (n = 7 measurements per embryo, four embryos per condition; **, P < 0.0001, unpaired t test). Error bars represent one standard deviation. (C) RhoA inhibition disrupts medioapical Patronin localization. Images are maximum-intensity Z-projections from representative live embryos expressing Patronin::GFP (apical surface) and Gap43::mCH (subapical section) injected with PBS (top) or the C3 exoenzyme (1 mg/ml; bottom). (D) RhoA inhibition decreases apical Patronin::GFP intensity. Quantification of average maximum Patronin::GFP intensity in a region that spans the apical cortex (n = 7 measurements per embryo, four embryos per condition; **, P < 0.0001, unpaired t test). Error bars represent one standard deviation. (E) Disrupting the apical F-actin network disrupts medioapical Patronin foci formation. Time-lapse images are maximum-intensity Z-projections from live embryos expressing Patronin::GFP (apical surface) and Gap43::mCH (subapical section) injected with DMSO (left) and CytoD (0.125 mg/ml; right). (F) fog signaling is sufficient to form ectopic medioapical Patronin foci in the ectoderm. Images are maximum-intensity projections of control and fog-overexpressed embryos expressing Patronin::GFP. The tissue regions shown in the images are highlighted by yellow boxes in the cartoon diagrams. Scale bars represent 15 µm (F) and 5 µm (A–E).