Centrosome age regulates kinetochore-microtubule stability and biases chromosome mis-segregation.

Ivana Gasic,Patrick Meraldi,Purnima Nerurkar

doi:10.7554/elife.07909

Abstract

The poles of the mitotic spindle contain one old and one young centrosome. In asymmetric stem cell divisions, the age of centrosomes affects their behaviour and their probability to remain in the stem cell. In contrast, in symmetric divisions, old and young centrosomes are thought to behave equally. This hypothesis is, however, untested. In this study, we show in symmetrically dividing human cells that kinetochore-microtubules associated to old centrosomes are more stable than those associated to young centrosomes, and that this difference favours the accumulation of premature end-on attachments that delay the alignment of polar chromosomes at old centrosomes. This differential microtubule stability depends on cenexin, a protein enriched on old centrosomes. It persists throughout mitosis, biasing chromosome segregation in anaphase by causing daughter cells with old centrosomes to retain non-disjoint chromosomes 85% of the time. We conclude that centrosome age imposes via cenexin a functional asymmetry on all mitotic spindles.

Highlights

The bipolar spindle has a symmetric appearance; it contains two centrosomes of different ages, as every centrosome is duplicated once during the cell cycle, resulting in the presence of an old and young centrosome at mitotic onset (Nigg and Stearns, 2011)
To distinguish between old and young centrosomes, we used untransformed hTert-RPE1 and transformed HeLa cell lines expressing eGFP-centrin1, a centriolar protein whose abundance correlates with centriole age, or an anti-cenexin antibody, a marker for old centrosomes (Figure 1A,B, Kuo et al, 2011; Lange and Gull, 1995)
We investigated the possible involvement of ninein, as it is essential for cell fate determination in asymmetric cell divisions of neuronal progenitors and preferentially localizes to old centrosomes in asymmetric cell division (Wang et al, 2009), and of cenexin itself, the classical marker for old centrosomes (Figure 3K—note that ninein levels could not be compared on old and young mitotic centrosomes, as it is only present at very low levels (Logarinho et al, 2012))

Summary

Introduction

The bipolar spindle has a symmetric appearance; it contains two centrosomes of different ages, as every centrosome is duplicated once during the cell cycle, resulting in the presence of an old and young centrosome at mitotic onset (Nigg and Stearns, 2011). The oldest centriole within the old centrosome contains distal and subdistal appendages: the first are necessary for centrioles to become basal bodies that can contact the plasma membrane (Graser et al, 2007; Hoyer-Fender, 2010), while the latter are involved in the organization of the interphase microtubule network, due to the presence of ninein, a key microtubuleanchoring protein (Mogensen et al, 2000) Both structures require the presence of cenexin, the oldest known marker for old centrosomes and appendages (Lange and Gull, 1995; Ishikawa et al, 2005).

Methods

Results

Conclusion