Fig. 6

Midbody microtubule organization is impaired in Kif5b deficient cells. a Immunofluorescence of α-tubulin in primary chondrocytes in late cytokinesis. Scale bar: 10 μm. b Quantification of tubulin intensity in midbody in primary chondrocytes (Kif5b^fl/+ cells: n = 24; Col2cre; Kif5b^fl/− cells: n = 27). ***P < 0.0001; two-tailed Mann–Whitney U-test. The whisker plot shows median (lines), interquartile range (boxes) and 10% to 90% percentile (whiskers). c Electron micrographs of midbody regions from sh-ctl and sh-Kif5b ATDC5 cells. Red lines denote the region of Flemming body. Yellow arrows and boxes denote the broken regions in Flemming body. Scale bar: 0.5 μm. d Quantification of the length of Flemming body in sh-ctl and sh-Kif5b cells (sh-ctl cells: n = 12; sh-Kif5b cells: n = 9). ***P < 0.0001; unpaired two-tailed t-test. Data are mean ± S.D. e Live imaging of sh-ctl and sh-Kif5b cells expressing GFP-tubulin in cytokinesis. Scale bar: 10 μm. f Quantification of the bi- and multi-nucleation rate in sh-Kif5b cells transiently expressing GFP, GFP-Kif5b and GFP-Kif5bΔMT (n = 5 independent experiments). ***P < 0.0001; NS, P = 0.4039; unpaired two-tailed t-test. Data are mean ± S.D. g A model showing the function of KIF5B in cytokinesis. In late cytokinesis, KIF5B alone or together with other unknown molecules cross-links microtubules in the midbody, and therefore the structure of midbody can be stably maintained