title: The spatial arrangement of chromosomes during prometaphase facilitates spindle assembly.
abstract: Error-free chromosome segregation requires stable attachment of sister kinetochores to the opposite spindle poles (amphitelic attachment). Exactly how amphitelic attachments are achieved during spindle assembly remains elusive. We employed photoactivatable GFP and high-resolution live-cell confocal microscopy to visualize complete 3D movements of individual kinetochores throughout mitosis in nontransformed human cells. Combined with electron microscopy, molecular perturbations, and immunofluorescence analyses, this approach reveals unexpected details of chromosome behavior. Our data demonstrate that unstable lateral interactions between kinetochores and microtubules dominate during early prometaphase. These transient interactions lead to the reproducible arrangement of chromosomes in an equatorial ring on the surface of the nascent spindle. A computational model predicts that this toroidal distribution of chromosomes exposes kinetochores to a high density of microtubules which facilitates subsequent formation of amphitelic attachments. Thus, spindle formation involves a previously overlooked stage of chromosome prepositioning which promotes formation of amphitelic attachments.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, NY 12201-509, USA.
authors.forename: Valentin
authors.initials: V
authors.lastname: Magidson
authors.forename: Christopher B
authors.initials: CB
authors.lastname: O'Connell
authors.forename: Jadranka
authors.initials: J
authors.lastname: Lončarek
authors.forename: Raja
authors.initials: R
authors.lastname: Paul
authors.forename: Alex
authors.initials: A
authors.lastname: Mogilner
authors.forename: Alexey
authors.initials: A
authors.lastname: Khodjakov
mesh_terms: D000818:Animals; D002460:Cell Line; D002503:Centromere / Q000378:metabolism; D002875:Chromosomes / Q000378:metabolism*; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D051379:Mice; D008870:Microtubules / Q000378:metabolism; D008958:Models, Molecular; D049468:Prometaphase; D008941:Spindle Apparatus / Q000378:metabolism*