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bioRxiv · 10.1101/2025.08.16.670680

The centriculum, a membrane that surrounds C. elegans centrosomes, acts as a microtubule filter

Maheshwari, R.·Rahman, M. M.·Ruddick, A.·Drey, S.·Cohen-Fix, O.
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Abstract

Centrosomes are cytoplasmic microtubule-nucleating structures. They are considered membraneless organelles, but in several cell types they are surrounded by ER-derived membrane. In C. elegans early embryos, this membrane forms a dense membrane reticulum, named the centriculum, that affects centrosome structure and microtubule nucleating capacity. The centriculum is adjacent to the centrosomes pericentriolar material (PCM) and to abundant, short peri-centrosomal microtubules. Here we show that when microtubule abundance is reduced, centriculum and PCM size decrease, while the density of the PCM protein SPD-5 increases, suggesting that the PCM can be compacted. We further show that centriculum size is determined by microtubules, and that the centriculum likely limits the length of peri-centrosomal microtubules. Finally, we find that the centriculum is more porous where spindle microtubules pass compared to where astral microtubules pass. These data are consistent with the centriculum serving as a microtubule filter, blocking the extension of most, but not all, centrosome-nucleated microtubules. Finally, if microtubule-centriculum collisions result in microtubule catastrophe, the filter function of the centriculum could also explain the high concentration of soluble tubulin at the C. elegans centrosome. Summary StatementThe centriculum is a centrosome-associated membrane reticulum in C. elegans embryos. This study shows that its size depends on microtubules and that it may act as a filter, limiting microtubule growth.

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Maheshwari, R., Rahman, M. M., Ruddick, A., Drey, S., Cohen-Fix, O.. 2025-08-18. The centriculum, a membrane that surrounds C. elegans centrosomes, acts as a microtubule filter. https://doi.org/10.1101/2025.08.16.670680

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