The k-fiber breakage occurs under sustained force for minutes, related to Fig. 4. Microneedle manipulation of individual k-fiber for minutes reveals k-fiber breakage instead of detachment from the kinetochore or pole. The microneedle (Alexa 555, yellow) exerts force on the k-fiber (GFP-tubulin, white) for minutes, and the k-fiber bends, lengthens, and ultimately breaks in two. Scale bar, 4 µm. Video was collected using a spinning disk confocal microscope at 1 frame every 10 s. Video has been adjusted to play back at a constant rate of 15 frames/s. Video corresponds to still images from Fig. 4 B.
