Spatiotemporal organization of branched microtubule networks

Abstract

To understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We use Xenopus egg extracts to study the nucleation and dynamics of MTs in branched networks, a process that is critical for spindle assembly. Surprisingly, new branched MTs preferentially originate near the minus-ends of pre-existing MTs. A sequential reaction model, consisting of deposition of nucleation sites on an existing MT, followed by rate-limiting nucleation of branches, reproduces the measured spatial profile of nucleation, the distribution of MT plus-ends and tubulin intensity. By regulating the availability of the branching effectors TPX2, augmin and γ-TuRC, combined with single-molecule observations, we show that first TPX2 is deposited on pre-existing MTs, followed by binding of augmin/γ-TuRC to result in the nucleation of branched MTs. In sum, regulating the localization and kinetics of nucleation effectors governs the architecture of branched MT networks.

The Dictyostelium Centrosome

“…Augmin, also called HAUS complex, is an eight-subunit complex capable of binding laterally to pre-existing spindle microtubules, and of recruiting γTuRCs via NEDD1/GDP-WD (see above). TPX2 also plays a role in this process, since it binds to pre-existing microtubules before recruiting augmin [230,231]. Augmin activity strongly increases microtubule number and, thus, the probability that kinetochores capture microtubule plus ends.…”

Learning from Embryo Development to Engineer Self‐organizing Materials

“…However, filament length may be stabilized by using drugs, such as taxol for microtubules and phalloidin for actin filaments. In vitro, these filaments may form homogeneous solutions and liquid crystals, respectively at low and high monomer concentration [41], bundles of filaments in the presence of crowding agents [95], branched networks in the presence of branching proteins [10,124], or crosslinked gels with the help of cross-linking proteins [10].…”

The SON RNA splicing factor is required for intracellular trafficking that promotes centriole assembly

“…Genes from the centrosome database and satellite proximity lists whose splicing is affected by SON were then sorted by their differential expression (Table S4). Within the top 50 genes in this list were several with known functions at centrosomes, including TUBG1 (tubulin), PCNT (Pericentrin), CEP131, HAUS4 (augmin complex member) and CNTROB (Centrobin) (Delaval & Doxsey, 2010;Staples et al, 2012;Thawani et al, 2019;Zou et al, 2005).…”