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J Cell Biol. 2014 Jul 21;206(2):231-43. doi: 10.1083/jcb.201401090. Epub 2014 Jul 14.

Direct kinetochore-spindle pole connections are not required for chromosome segregation.

Author information

1
Wadsworth Center, New York State Department of Health, Albany, NY 12201.
2
Rockefeller University, New York, NY 10021.
3
Institut Curie, 75248 Paris, France.
4
Stanford School of Medicine, Stanford, CA 94305.
5
Wadsworth Center, New York State Department of Health, Albany, NY 12201 Rensselaer Polytechnic Institute, Troy, NY 12180 alexey.khodjakov@health.ny.gov.

Abstract

Segregation of genetic material occurs when chromosomes move to opposite spindle poles during mitosis. This movement depends on K-fibers, specialized microtubule (MT) bundles attached to the chromosomes' kinetochores. A long-standing assumption is that continuous K-fibers connect every kinetochore to a spindle pole and the force for chromosome movement is produced at the kinetochore and coupled with MT depolymerization. However, we found that chromosomes still maintained their position at the spindle equator during metaphase and segregated properly during anaphase when one of their K-fibers was severed near the kinetochore with a laser microbeam. We also found that, in normal fully assembled spindles, K-fibers of some chromosomes did not extend to the spindle pole. These K-fibers connected to adjacent K-fibers and/or nonkinetochore MTs. Poleward movement of chromosomes with short K-fibers was uncoupled from MT depolymerization at the kinetochore. Instead, these chromosomes moved by dynein-mediated transport of the entire K-fiber/kinetochore assembly. Thus, at least two distinct parallel mechanisms drive chromosome segregation in mammalian cells.

PMID:
25023516
PMCID:
PMC4107786
DOI:
10.1083/jcb.201401090
[Indexed for MEDLINE]
Free PMC Article

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