Association of mitochondria with spindle poles facilitates spindle alignment  Nadine Krüger, Iva M. Tolić-Nørrelykke  Current Biology  Volume 18, Issue 15, Pages R646-R647 (August 2008) DOI: 10.1016/j.cub.2008.06.069 Copyright © 2008 Elsevier Ltd Terms and Conditions

Figure 1 Association of mitochondria with spindle poles attenuates spindle rotation in wild-type cells. (A) Electron micrograph of a wild-type S. pombe cell in mid-mitosis. A mitochondrion (Mi) is found in close proximity to each spindle pole body (SPB). (B) A typical wild-type cell shows persistent association of mitochondria with the spindle poles throughout mitosis, and only modest rotation of the spindle. (C) A rare wild-type cell, in which mitochondria–spindle pole interactions are lost, shows extensive spindle rotation. Scale bars, 2 μm. (D) Maximum spindle angle (|α|, see inset) is shown as a measure of spindle rotation. Associated wild-type spindles (red) showed smaller maximum angles than free wild-type spindles (green; p = 8·10−4). (E) Distance (Δx, see inset) covered by each spindle pole during the time interval when one pole was associated and the other one was free, for the six free spindles shown in (D). The free pole (green) moved a larger distance than the associated pole (red; p = 6·10−3). The length of the spindles in (D) and (E) was smaller than 4 μm; the numbers of cells are shown in the bars; error bars represent standard error of the mean (s.e.m.). Current Biology 2008 18, R646-R647DOI: (10.1016/j.cub.2008.06.069) Copyright © 2008 Elsevier Ltd Terms and Conditions

Figure 2 Dissociation of mitochondria in mto1Δ cells correlates with large spindle rotation. (A) In a typical mto1Δ cell (strain KN002), mitochondria are less associated with spindle poles, and the spindle rotates more than in wild type. Scale bar represents 2 μm. (B) Associated mto1Δ spindles (red) showed smaller maximum angles than free mto1Δ spindles (green; p = 0.003). The numbers of cells are shown in the bars; error bars represent s.e.m. (C) Mitochondria decrease spindle rotation and thus promote spindle alignment. Left: The spindle (green) is initially aligned with the cell axis. Mitochondria (red), which are associated with the spindle poles, decrease the rotation of the spindle and thus help the spindle to remain aligned with the cell axis. Right: Spindles that are not associated with mitochondria, as found occasionally in wild-type cells and often in mto1Δ cells, rotate and lose their initial alignment. The resulting spindle misalignment may be fatal, leading to chromosome mis-segregation if spindle elongation is impaired. Current Biology 2008 18, R646-R647DOI: (10.1016/j.cub.2008.06.069) Copyright © 2008 Elsevier Ltd Terms and Conditions