Trends in Cell Biology
Volume 11, Issue 10, 1 October 2001, Pages 413-419
Journal home page for Trends in Cell Biology

Opinion
The centrosome in vertebrates: more than a microtubule-organizing center

https://doi.org/10.1016/S0962-8924(01)02085-2Get rights and content

Abstract

The somatic cells of all higher animals contain a single minute organelle called the centrosome. For years, the functions of the centrosome were thought to revolve around its ability to nucleate and organize the various microtubule arrays seen in interphase and mitosis. But the centrosome is more than just a microtubule-organizing center. Recent work reveals that this organelle is essential for cell-cycle progression and that this requirement is independent of its ability to organize microtubules. Here, we review the various functions attributed to the centrosome and ask which are essential for the survival and reproduction of the cell, the organism, or both.

Section snippets

Centrioles and the centrosome

We begin our argument with a definition of what a centrosome is in vertebrates. Despite recent advances in light microscopy, in the living cell, this organelle still appears as one or two dots, usually located near the nucleus (Fig. 1a). To appreciate fully its structural complexity, the centrosome must be viewed by electron microscopy. With this technique, it is seen to contain two ‘centrioles’, each of which comprises a pinwheel of nine triplet MT ‘blades’ distributed evenly around the

Centrosome functions based on microtubule nucleation

The MTOC activity of the centrosome includes the nucleation and organization of those MTs that form the interphase cytoplasmic MT array (Fig. 1c) and the mitotic spindle (Fig. 1d), as well as cilia (Fig. 1b,f). The first two activities are centred on the nucleation of MTs by sites inside the pericentriolar material, whereas the last activity involves the nucleation of MTs directly from the centriole.

Centrosome function(s) unrelated to MTOC activity

When the centrosome is surgically removed from BSC-1 cells during S phase 13, or destroyed in CV-1 or PtK1 cells during G2 phase by laser ablation 12, the cells continue to progress into and complete mitosis, but the resultant progeny arrest in G1 (Fig. 3a). Importantly, this G1 arrest occurs in spite of the fact that the (now) acentrosomal cells appear to contain normal amounts of microtubules that are organized in a way similar to those of controls. Furthermore, when the MTs in CV-1 (Fig. 4)

Concluding remarks

Traditionally, research on the centrosome in higher animals has focused its ability to nucleate and organize MT arrays during interphase and mitosis. It is now evident, however, that the centrosome is more than just an MTOC. In fact, although the MTOC functions of this organelle are its most visible activity, we argue that they are not essential for the survival and reproduction of individual cells. This is because, with the exception of cilia/flagella formation, functional MT arrays can be

Acknowledgements

C.L.R. and A.K. are supported, in part, by NIH-GMS grants 40198 and 59363.

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