Figure 10

Mitotic orientation in pre-cystic tubules of Cd79a-Tsc1 knockout (KO) kidneys. (a) 3D reconstruction of the mitotic orientation of dividing epithelial cells in pre-cystic, normal-looking tubules. Sections of control and Cd79a-Tsc1 KO kidneys were stained with phospho-histone H3 (pHH3, green) and DBA (red), markers for condensing chromosomes in dividing cells and the distal tubule/collecting duct, respectively. Representative images from 3 independent tubules are shown. Mitotic angles and the difference in orientation between mitotic chromosomes and the tubular axis were measured. (b) Time-course changes in the distribution of mitotic angles in the dividing tubular cells of the kidney. At P0, Cd79a-Tsc1 KO tubule cells oriented their mitotic spindles along the tubule axis in a manner indistinguishable from that of controls (n = 11 vs n = 48 control, ns). At P7, the mitotic spindle of dividing control tubules was oriented more parallel to the tubular axis: 70% of angles were smaller than 34°, with an average of 11°, are were no longer random. By contrast, the distribution of the mitotic orientation in CD79a-KO tubule cells was significantly distorted, with a more random distribution compared with controls (P < 0.001, n = 185 vs control n = 85). These data were obtained from a minimum of 6 kidneys from at least 3 litters. Statistical differences were determined by the Kolmogorov–Smirnov and Mann–Whitney U tests.