Next seminar : Physics-Biology interface seminar: Jan Brugues

Wednesday, November 21 2018 at 11:00:00

How to set the proper size and shape of metaphase spindles

Jan Brugues (MPI Dresden, Germany)

Regulation of size and growth is a fundamental problem in biology. A prominent example is the formation of the mitotic spindle, where protein concentration gradients around chromosomes are thought to regulate spindle growth by controlling microtubule nucleation. Previous evidence suggests that microtubules nucleate throughout the spindle structure. However, the mechanisms underlying microtubule nucleation and its spatial regulation are still unclear. In the first part of the talk I will present an assay based on laser ablation to directly probe microtubule nucleation events in Xenopus laevis egg extracts. Combining this method with theory and quantitative microscopy, we show that the size of a spindle is controlled by autocatalytic growth of microtubules, driven by microtubule-stimulated microtubule nucleation. The autocatalytic activity of this nucleation system is spatially regulated by the limiting amounts of active microtubule nucleators, which decrease with distance from the chromosomes. This mechanism provides an upper limit to spindle size even when resources are not limiting. Once the necessary amounts of microtubules are created, the activities of motors lead to the proper shape and architecture of spindles. In the second part of the talk I will discuss the origin of motor-mediated stress in spindles.

Last Highlight : C’est chaud une ville la nuit

Il tend à faire plus chaud en centre-ville qu’en banlieue, mais certains centres chauffent davantage que d’autres. Une équipe de recherche internationale vient d’établir que la disposition des immeubles conditionne la température nocturne des villes – une découverte clé pour l’urbanisme de demain.

Voir la suite de l'article sur  CNRS - le journal

Ref. : J. M. Sobstyl, T. Emig, M. J. Abdolhosseini Qomi, F.-J. Ulm et R. J.-M. Pellenq, Role of City Texture in Urban Heat Islands at Nighttime, Phys. Rev. Lett. 120, 108701 (2018)

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