Physics-Biology interface seminar

Held every second Wednesday at 11am in the Blandin amphitheatre at LPS (not LPTMS!) in Orsay, this seminar series aims to be a central forum for the Physics/Biology interface in the south of Paris.

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Other seminars and conferences you might be interested in:

Paris-Saclay Biomechanics seminar - last Thu. of the month in Palaiseau (subscribe to their announcements)
Seminar of the Physical Chemistry Laboratory - in Orsay

Informations for speakers
Past seminars
Contact the organizer

How to set the proper size and shape of metaphase spindles.

Jan Brugues (MPI of Molecular Cell Biology and Genetics & MPI for Physics of Complex Systems, 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.

Location: Amphi BLANDIN du LPS de la Faculté des Sciences d’Orsay (Bâtiment 510)

Stéphanie Bonneau (Laboratoire Jean Perrin, Paris)

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay

Shiladitya Banerjee (UCL, UK)

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay

Pere Roca-Cusachs (Institute for Bioengineering of Catalonia, Universitat de Barcelona, Spain)

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay

Mechano-sensitive adhesion in cell spreading and crawling

Pierre Sens (Institut Curie, Paris)

Crawling cell motility is powered by actin polymerization and acto-myosin contraction. When moving over a flat and rigid substrate, cells usually develop thin and broad protrusions at their front, called lamellipodia, where actin polymerisation generates a protrusive force pushing the front edge of the cell forward. The lamellipodium displays interesting dynamics, including normal and lateral waves, possibly relevant to cell polarisation and the initiation of motion. I will discuss a stochastic model of mechano-sensitive cell adhesion, and discuss its relevance for symmetry breaking, cell polarisation, and motility. I will then discuss a generic model of micro-crawlers, built as an extension of low Reynolds number micro-swimmers, that highlights the crucial role of mechano-sensitive adhesion for the active crawling of cells and biomimetic objects.

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay

Emmanuel de Langre (École polytechnique, Palaiseau, France)

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay

David Bensimon (LPS-ENS, Paris, France)

Location: Moyen Amphi, Building 510, Université Paris-Sud Orsay