Morg1 controls apico-basal polarity during cyst development. (A–C) Representative confocal images of MDCK cells transfected with control RNA, Morg1 siRNA, or Cdc42 siRNA. Cells were grown for 48 or 72 h in 3D culture and stained as indicated. (D–F) Quantification of normally oriented cysts with a solitary lumen (D, normal cysts), cysts with inverted orientation (E), or cysts with multiple lumens (F) in 3D culture of MDCK cells transfected with the indicated RNA. Values are means ± SD from three independent experiments (n ≥ 100 cysts/experiment). *, P < 0.05 (Welch’s t test); ***, P < 0.001 (Student’s t test). (G–I) Representative confocal images of control MDCK or Morg1 kd #1-1 cells. Cells were grown for 48 h in 3D culture and stained as indicated. (J–L) Quantification of normally oriented cysts with a solitary lumen (J, normal cysts), cysts with inverted orientation (K), or cysts with multiple lumens (L) in Morg1-depleted cells. Values are means ± SD from three independent experiments (n ≥ 100 cysts/experiment). ***, P < 0.001 (Dunnett’s test). (M) Representative confocal microscopy images of control MDCK or Morg1 kd #1-1 cells in mitosis. Cells were grown for 48 h in 3D culture and stained with the indicated antibodies. Arrowheads and white lines indicate spindle poles and spindle axes, respectively. (N) Scatter diagrams and box-and-whisker plots of metaphase spindle angles in control MDCK and Morg1 kd #1-1 cells (n = 25 cysts/experiment). ***, P < 0.001 (Wilcoxon rank sum test). Bar, 10 µm.