Architecture of spindles in nocodazole-treated cells. (A) Immunofluorescence images showing three major spindle morphologies in nocodazole-treated cells. A small minority of the cells had ambiguous morphologies and were not classified. The percentage belonging to each class is printed in the bottom row (n = 227). (B) Cryotomographic slices (10 nm) of spindle and cytoplasmic MTs. The plus end is oriented upward in each panel. Green arrows: Dam1C/DASH densities. (C) Model of a nocodazole-disrupted spindle with complete Dam1C/DASH rings associated with short MTs. Part of the bottommost Dam1C/DASH ring (black arrow) could not be modeled because it was located near the cryosection’s surface. Green arrow: Dam1C/DASH ring that is enlarged in D. Inset: schematic showing the effect of nocodazole treatment. (D) Left, cryotomographic slice (8 nm) showing the front view of a complete Dam1C/DASH ring on a short kMT. Right, the same cryotomographic slice, but annotated with green dashes over the Dam1C/DASH densities and magenta dashes over the MT densities. (E) Model of unattached Dam1C/DASH oligomers and MT fragments in the nucleoplasm. Green arrow: partial Dam1C/DASH ring that is enlarged in F. (F) Left, cryotomographic slice (8 nm) showing unattached Dam1C/DASH partial rings. Right, the same cryotomographic slice but annotated with green dashes overlaying the Dam1C/DASH densities.