Changes in prometaphase chromosome motion are dependent on experimentally induced changes in kinetochore structure.

ABSTRACT Prometaphase PtK1 cells are treated with low concentrations of sucrose in order to analyze its effects on kinetochore structure, microtubule (MT) associations with the developing kinetochore and chromosome congression. Prometaphase cells treated with 0.15M sucrose slows chromosome congression, yet chromosomes form a metaphase configuration. However, 0.2M sucrose treatment prevents chromosome congression and affects some of the kinetochore MT linkages with the kinetochore, resulting in loss of chromosome congression. We use time lapse video microscopy and ultrastructural analysis to correlate changes in the linkages in the kinetochore MTs and the kinetochore to explain these findings. It appears hyperosmotic shock treatment can produce non‐functional linkages between kinetochore MTs and kinetochores such that chromosome congression is affected. When non‐functional linkages are formed, the presence of both a corona and matrix‐like material is also present, proximal to the kinetochore. The role of this material and its organization at the klnetochore is discussed in its relation to generating mitotic forces.