Séminaire externe : Chaitanya Athale

Séminaire externe : Chaitanya Athale (Faculty from IISER Pune, India) 

"Collective Activity of Microtubule-Motor Systems Sense Cellular Geometry"

Résumé :

In eukaryotic cells, microtubules (MTs) generate a system of polarised tracks along which plus- (kinesins) and minus-ended (dyneins) molecular motors transport vesicles and maintain and modulate cell polarity. At the same time, cell shape itself is likely to play a role in the patterns produced, as seen in the arrangement of MTs in the axon.
Here, I will describe the patterns formed in response to cellular geometry by radial MT arrays or asters in combination with molecular motors. While in previous model simulations we had shown the need in a cell free system for a gradient of MT regulators to produce directional aster transport [1], in mouse oocyte cells the gradient model does not explain experimental data. Instead a force-gradient due to dynein localisation around chromosomes, combined with self- organized clustering of asters by tetrameric dyneins, is required to reproduce the experimental data [2]. We extend this model to a general system of circular cells that confine multiple asters while cortical dyneins result in centrifugal forces due to MT pulling, resulting in spontaneous self- organized rotation that is achiral [3]. We examine this model in terms similar to the models of flocking behaviour by Viscek and find differences from the general class of models. At the same time we attempt to find the minimal rules determining the emergence of multi-aster patterns in cell confinement [4].
In summary these simulations present a picture of the ability of multi-MT complexes like asters to sense cellular geometry, determining the patterns formed. These calculations can explain available data and predict novel regimes of pattern formation not seen so far.
References

[1] Athale C.A.*, Dinarina A., Nedelec F. and Karsenti E. (2014) Collective behavior of minus- ended motors in mitotic microtubule asters gliding towards DNA. Phys. Biol. 11: 016008
[2] Khetan N. and Athale C.A.* (2016) A Motor-Gradient and Clustering Model of the Centripetal Motility of MTOCs in Meiosis I of Mouse Oocytes PLoS Comput Biol 12(10): e1005102.
[3] Khetan N and Athale C.A. (2020) Aster Swarming by Symmetry Breaking of Cortical Dynein Transport and Coupling Kinesins. Soft Matter 2020,16, 8554-8564
[4] Khetan N, Pruliere G, Hebras C, Chenevert J, Chaitanya A. Athale (2021) Self-organized optimal packing of kinesin-5-driven microtubule asters scales with cell size. J Cell Sci. 134(10):jcs257543.

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