Cell Division: NuMA Bears the Load in the Spindle Helder Maiato, António J. Pereira  Current Biology  Volume 27, Issue 15, Pages R765-R767 (August 2017) DOI: 10.1016/j.cub.2017.06.060 Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 Mitotic spindle coupling and load bearing. (A) Time-lapse sequence of a Drosophila S2 cell depleted of Ncd/kinesin-14 by RNAi, illustrating the relevance of spindle pole focusing for accurate chromosome segregation (image credit: Sara Moutinho-Pereira/CID Lab). Time is in min:sec after nuclear envelope breakdown. Scale bar = 5 μm. (B) Mechanical coupling between neighbor k-fibers in grasshopper spermatocytes. From [8] © 1982 Nicklas et al. Journal of Cell Biology, DOI:http://dx.doi.org/10.1083/jcb.95.1.91. The dashed arrow indicates the direction of the micromanipulated chromosome, while the arrowhead indicates the bending of an adjacent k-fiber. P indicates the spindle pole. (C) Severing of a k-fiber leads to decreased tension across the corresponding centromere. In a coupled-spindle scenario, it could be expected that this would decrease the load on the force-generating mechanisms, eventually resulting in a poleward sliding response and increased stretching of neighbor centromeres. (D) Possible models of NuMA-mediated coupling based on the data by Elting et al. [6]. On the left side, NuMA bears load by cross-linking k-fibers with parallel interpolar microtubules. Whether this relies directly on its microtubule-binding properties, or on the recruitment of dynein to microtubules remains unclear. On the right side, NuMA is shown to bear load as part of an insoluble spindle matrix (orange box) (based on data from [20]). Current Biology 2017 27, R765-R767DOI: (10.1016/j.cub.2017.06.060) Copyright © 2017 Elsevier Ltd Terms and Conditions