Accumulation of short microtubules near kinetochores during NEB. (A) Selected 70-nm section from a full AT series (see Fig. S1 A). Dim spots of α-tubulin are apparent in the immediate proximity of some Hec1 spots if image contrast is increased (linear intensity stretch). (A′) Full series of sections through centromeres boxed in A. Notice that α-tubulin spots are adjacent to but not precisely colocalized with Hec1 spots. (B) Histograms of α-tubulin intensities near kinetochores (Ks) in the two reconstructed cells (cell 1 is the cell shown in A–A′). Intensities are normalized to the brightest spot in each cell. Number of α-tubulin spots detected in each cell is shown. (C) 70-nm EM section depicting chromosomes inside a partially perforated nucleus (see Fig. S1 B). (C′) Full series of EM sections through the centromere boxed in C. Numerous variably oriented microtubules are adjacent to the kinetochores. Most microtubules are short (arrows), but some exceed 1-µm length (arrowheads).