Fig. 9

Organization of MT bundles in metaphase S2 cells. a, b Serial optical sections (a) and maximum projection (b) of a metaphase cell stained for tubulin, the centromere marker Cid, and DNA (DAPI). Some MT bundles are running continuously between the two spindle poles without encountering the centromeres (interpolar bundles), while other bundles end at kinetochores (k-fibers). Note that MT bundles attached to different kinetochores and interpolar bundles are closely apposed (and/or intermingled) in the regions between the centromeres and the spindle poles. Scale bars: 5 μm. c Maximum intensity projections of confocal images of early (top) and late (bottom) anaphase cells showing interpolar MT bundles. Scale bar: 5 μm. d A model for the MT–kinetochore interaction during late prometaphase and metaphase. The model depicts a portion of a late prometaphase/metaphase cell that includes only two chromosomes. Grey MT bundles are k-fibers. Green and red MTs are interpolar MT bundles running laterally to kinetochores. The scheme does not imply that the k-fibers are as numerous as the interpolar MT bundles. k-fibers A and B are attached to the kinetochores of two neighboring chromosomes. Note that k-fiber A is a lateral MT bundle for kinetochore B (kB)