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Updated: Jul 31, 2026

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
Ran-GTP coordinates regulation of microtubule nucleation and dynamics during mitotic-spindle assembly
R E Carazo-Salas1, O J Gruss, I W Mattaj
1European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. carazosa@embl-heidelberg.de
Abstract:
It was recently reported that GTP-bound Ran induces microtubule and pseudo-spindle assembly in mitotic egg extracts in the absence of chromosomes and centrosomes, and that chromosomes induce the assembly of spindle microtubules in these extracts through generation of Ran-GTP. Here we examine the effects of Ran-GTP on microtubule nucleation and dynamics and show that Ran-GTP has independent effects on both the nucleation activity of centrosomes and the stability of centrosomal microtubules. We also show that inhibition of Ran-GTP production, even in the presence of duplicated centrosomes and kinetochores, prevents assembly of a bipolar spindle in M-phase extracts.
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In most cells, centrosomes are the primary microtubule nucleation centers. In the centrosome-mediated pathway, the G2-prophase transition triggers centrosome maturation and increased microtubule nucleation. Progressive nucleation results in a microtubule array...

