A Regulatory Switch Alters Chromosome Motions at the Metaphase-to-Anaphase Transition

Abstract

SummaryTo achieve chromosome segregation during mitosis, sister chromatids must undergo a dramatic change in their behavior to switch from balanced oscillations at the metaphase plate to directed poleward motion during anaphase. However, the factors that alter chromosome behavior at the metaphase-to-anaphase transition remain incompletely understood. Here, we perform time-lapse imaging to analyze anaphase chromosome dynamics in human cells. Using multiple directed biochemical, genetic, and physical perturbations, our results demonstrate that differences in the global phosphorylation states between metaphase and anaphase are the major determinant of chromosome motion dynamics. Indeed, causing a mitotic phosphorylation state to persist into anaphase produces dramatic metaphase-like oscillations. These induced oscillations depend on both kinetochore-derived and polar ejection forces that oppose poleward motion. Thus, our analysis of anaphase chromosome motion reveals that dephosphorylation of multiple mitotic substrates is required to suppress metaphase chromosome oscillatory motions and achieve directed poleward motion for successful chromosome segregation.

Hec1 Tail Phosphorylation Differentially Regulates Mammalian Kinetochore Coupling to Polymerizing and Depolymerizing Microtubules

“…1–2), the coupling to depolymerizing microtubules can never be probed directly as it is always resisted by its sister. Anaphase kinetochores could provide a solution, but kinetochore biochemistry changes between metaphase and anaphase [21]. Hence, we turned to laser ablation to physically separate sister kinetochores: after ablating one sister, the remaining sister moves towards its pole as its k-fiber depolymerizes [1,22] (Fig.…”

The dynamics of centromere motion through the metaphase-to-anaphase transition reveal a centromere separation order

“…The dynamics of centromere motion during metaphase has been the focus of many quantitative studies [13][14][15][16][17][18][19] . The development of automated centromere tracking, advanced image analysis, and datadriven mathematical modelling has provided novel mechanistic and molecular insights into metaphase centromere dynamics 20,21 .…”

“…However, the dynamic behaviour of centromeres during the metaphase-toanaphase transition and during anaphase has been largely overlooked due of the lack of appropriate quantitative tools. Recently the differences in kinetochore phosphorylation states between metaphase and anaphase and how they relate to anaphase chromosome motion has been studied 19 . Here, we have developed a Bayesian statistical model of centromere intersister distance to objectively determine the point of centromere separation via automated tracking of centromeres and to characterise centromere dynamics during and beyond the metaphase-anaphase transition.…”

Anaphase A: Disassembling Microtubules Move Chromosomes toward Spindle Poles

“…If kinetochore-attached microtubules were similarly stabilized, the effect on anaphase A would be antagonistic, potentially slowing chromosome-to-pole movement by retarding disassembly at both plus and minus ends. However, evidence from budding yeast [206] and human tissue culture cells [208] indicates that the dephosphorylation associated with deactivation of CDK1 (or with activation of its antagonizing phosphatase, Cdc15) helps to promote, rather than antagonize anaphase A. In human cells, chemical inhibition of dephosphorylation converts the normally smooth chromosome-to-pole motion, with few reversals, into a much more oscillatory motion, with frequent reversals [208].…”