Role of non-kinetochore microtubules in spindle elongation in mitotic PtK1 cells

Eur J Cell Biol. 1986 Jan;39(2):373-9.


PtK1 metaphase cells were treated with varying concentrations of nocodazole to reduce spindle microtubule number and spindle length. The range of concentrations employed reduced spindle length from approximately 47% to 82% of the original pole-pole distance. Electron microscopy of cells treated with the lowest concentration of nocodazole employed (0.01 microgram/ml) showed a small decrease in the number of non-kinetochore microtubules (nkMTs), particularly evident in the astral region, with no significant effect on kinetochore microtubule number. Metaphase cells treated with 1 microgram/ml nocodazole for 2 min demonstrated a reduction in spindle length and loss of most non-kinetochore microtubules with little effect on the number and arrangement of the kinetochore class of microtubules. Following nocodazole treatment, the cells were perfused with 0.5 M sucrose dissolved in tissue culture medium, a treatment which has previously been shown to induce spindle elongation in metaphase cells. In cells where nocodazole effected a large decrease in non-kinetochore microtubule number with a concomitant decrease in spindle length, sucrose treatment had a reduced effect in inducing spindle elongation. In cells treated with lower concentrations of nocodazole, where numerous non-kinetochore microtubules remained, sucrose had a greater effect in inducing spindle elongation. These data suggest that the non-kinetochore population of microtubules is responsible for the extent of sucrose-induced spindle elongation. An explanation of these data is provided which suggests that the role of non-kinetochore microtubules is to trap energy in the developing spindle, such that it can be used to separate spindle poles during anaphase B.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Benzimidazoles / pharmacology
  • Cell Line
  • Centromere / drug effects
  • Centromere / physiology*
  • Centromere / ultrastructure
  • Chromosomes / physiology*
  • Macropodidae
  • Metaphase / drug effects
  • Microscopy, Electron
  • Microtubules / physiology*
  • Mitosis* / drug effects
  • Nocodazole
  • Rats
  • Spindle Apparatus / drug effects
  • Spindle Apparatus / physiology*
  • Spindle Apparatus / ultrastructure
  • Sucrose / pharmacology


  • Benzimidazoles
  • Sucrose
  • Nocodazole