Current Biology
Volume 30, Issue 15, 3 August 2020, Pages 3016-3023.e3
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Microtubule Growth Rates Are Sensitive to Global and Local Changes in Microtubule Plus-End Density

https://doi.org/10.1016/j.cub.2020.05.056Get rights and content
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Highlights

  • Xenopus egg extract can be isolated into discrete volumes at the cellular scale

  • Microtubule plus-end growth is sensitive to the proximity of other plus ends

  • Microtubule growth rates negatively correlate with global and local plus-end density

Summary

The microtubule cytoskeleton plays critically important roles in numerous cellular functions in eukaryotes, and it does so across a functionally diverse and morphologically disparate range of cell types [1]. In these roles, microtubule assemblies must adopt distinct morphologies and physical dimensions to perform specific functions [2, 3, 4, 5]. As such, these macromolecular assemblies—as well as the dynamics of the individual microtubule polymers from which they are made—must scale and change in accordance with cell size, geometry, and function. Microtubules in cells typically assemble to a steady state in mass, leaving enough of their tubulin subunits soluble to allow rapid growth and turnover. This suggests some negative feedback that limits the extent of assembly, for example, decrease in growth rate, or increase in catastrophe rate, as the soluble subunit pool decreases. Although these ideas have informed the field for decades, they have not been observed experimentally. Here, we describe the application of an experimental approach that combines cell-free extracts with photo-patterned hydrogel micro-enclosures as a means to investigate microtubule dynamics in cytoplasmic volumes of defined size and shape. Our measurements reveal a negative correlation between microtubule plus-end density and microtubule growth rates and suggest that these rates are sensitive to the presence of nearby growing ends.

Keywords

microfluidics
cytoskeleton
microtubules
Xenopus extracts
microtubule dynamics
tubulin
microtubule aster

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