STK11 mutation causes spindle misorientation in vivo.

Tissue immunofluorescence was done on upper gastrointestinal tumors from STK11/LKB1 heterozygous mutant mice and corresponding gastrointestinal tissue from wild-type littermates. A) Representative images from STK11/LKB1 wild-type tissues and STK11/LKB1 mutant polyps. The brush border at the apical cell surface is at the top of each panel (arrowhead at left and arrow at right) and the spindles were rotated in three dimensions to place both spindle poles in a single plane. Microtubules are green, actin is red, and DNA is blue. Spindle angle was measured as the angle between the spindle axis and the apical surface. The wild-type spindle is oriented parallel to the apical surface, and the three STK11/LKB1 mutant spindles lack this planar orientation. B) Quantification of spindle angles. Each dot represents a single spindle angle measurement. Blue bars represent means and standard error of the mean. See text for numbers. P<0.0001 for the difference. C) Data from (B) presented as the % of angles that range from 0° to 30°, 30° to 60°, and 60° to 90°. D) Spindles from STK11 mutant cells contain astral microtubules. White arrows show astral microtubules of misoriented spindles in STK11/LKB1 mutant polyps. These spindles are from the original data set used to calculate spindle angle, but the confocal stacks were adjusted, rotated, and processed differently from (A) to show astral microtubules optimally, and spindle angle cannot be appreciated from them. Scale bars, 10 µm.