Abstract
The centrosome is an unusual organelle that lacks a surrounding membrane, raising the question of what limits its size and shape. Moreover, while electron microscopy (EM) has provided a detailed view of centriole architecture, there has been limited understanding of how the second major component of centrosomes, the pericentriolar material (PCM), is organized. Here, we summarize exciting recent findings from super-resolution fluorescence imaging, structural biology, and biochemical reconstitution that together reveal the presence of ordered layers and complex gel-like scaffolds in the PCM. Moreover, we discuss how this is leading to a better understanding of the process of microtubule nucleation, how alterations in PCM size are regulated in cycling and differentiated cells, and why mutations in PCM components lead to specific human pathologies.
Highlights
The centrosome is a single copy organelle present in the majority of animal cells[1]
Through concentrating proteins required for microtubule nucleation, most notably γ-tubulin and its γ-tubulin ring complex (γ-TuRC) partners, it serves as the primary microtubule organizing center (MTOC) of the cell[2]
We have long known that the pericentriolar material (PCM) is the site from which microtubules are nucleated and that microtubule nucleation capacity can be precisely modulated according to specific cues[3]
Summary
The centrosome is a single copy organelle present in the majority of animal cells[1]. The principle of an ordered proximal layer at the PCM when present in interphase and a more disordered gel-like scaffold in the expanded PCM in mitosis does appear to be universally shared These findings are stimulating specific structure–function studies into, for example, how the proximal layer regulates centrosome size, how the filament proteins are anchored to centriole walls, and how expansion and disassembly of the PCM are regulated by post-translational modifications. The uniformity of organs affected in primordial dwarfism and, the tissue specificity in primary microcephaly are striking and difficult to explain, considering that different mutations in the same protein (Cep152) can give rise to one or other pathology Answering these questions will come at least in part from complementing what we have learnt from superresolution, structural biology, and biochemical reconstitution studies with gene-editing approaches not just in cells and in whole animals. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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