Abstract
Aberrant centrosome activities in mutants of Dictyostelium discoideum result in anomalies of mitotic spindles that affect the reliability of chromosome segregation. Genetic instabilities caused by these deficiencies are tolerated in multinucleate cells, which can be produced by electric-pulse induced cell fusion as a source for aberrations in the mitotic apparatus of the mutant cells. Dual-color fluorescence labeling of the microtubule system and the chromosomes in live cells revealed the variability of spindle arrangements, of centrosome-nuclear interactions, and of chromosome segregation in the atypical mitoses observed.
Highlights
In Dictyostelium as in many other cells, reliable chromosome segregation during mitosis depends on the association of one centrosome with the nucleus, the division of this centrosome, and the formation of an elongating spindle between the daughter centrosomes
The notion that aberrations in centrosome function result in unreliable chromosome segregation, causing genetic instability, has a long history
To visualize spindle aberrations caused by impaired centrosome–nuclear interactions, we used mutants of Dictyostelium in which these interactions were destabilized, and labeled the cells with two fluorescence markers, one for the microtubule system including the centrosomes, the other for the chromosomes
Summary
In Dictyostelium as in many other cells, reliable chromosome segregation during mitosis depends on the association of one centrosome with the nucleus, the division of this centrosome, and the formation of an elongating spindle between the daughter centrosomes. The notion that aberrations in centrosome function result in unreliable chromosome segregation, causing genetic instability, has a long history. Theodor Bovery emphasized in 1914 that tumor cells may be derived from genetic alterations that were caused by the impaired function of centrosomes [1]. To visualize spindle aberrations caused by impaired centrosome–nuclear interactions, we used mutants of Dictyostelium in which these interactions were destabilized, and labeled the cells with two fluorescence markers, one for the microtubule system including the centrosomes, the other for the chromosomes. To induce spindle formation, the centrosome translocates from its position at the outer nuclear membrane into the nucleus and divides there; the two daughter centrosomes build the two poles of the spindle [3]
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