Live-cell imaging reveals square shape spindles and long mitosis duration in the silkworm holocentric cells

Kinesin-5 and kinesin-14 are partially antagonistic in spindle assembly in the holocentric silkworm B. mori cells

We previously showed that the silkworm holocentric spindles are square-shaped, compared to the canonical oval shape of human monocentric spindles (Vanpoperinghe et al. 2021). Further, while kinesin-5 depletion resulted in monopolar spindles in both cells, kinesin-14 depletion affected only the silkworm cells, resulting in mal-shaped spindles (Vanpoperinghe et al. 2021). We now extend our study to quantify the effect of kinesin-5 and kinesin-14 on spindle assembly dynamics and chromosome segregation in holocentric silkworm BmN4 cells. We find that mal-shaped spindle and prolonged mitosis duration are highly correlated with chromosome segregation error, leading to aneuploidy and cell death in BmN4 cells. Further, double RNAi-mediated depletion of kinesin-5 and kinesin-14 partially rescue the monopolar spindle and mal-shaped spindle phenotypes in kinesin-5 and kinesin 14-depleted cells, respectively.