Sciences de la matière et microgravité

J. Phys. IV France 11 (2001) Pr6-239-Pr6-246
DOI: 10.1051/jp4:2001628

The effect of gravity on microtubule self-organisation

J. Tabony¹, N. Glade^{1, 2}, C. Papaseit¹ and J. Demongeot<sup>2

1</sup>  Commissariat à l'Énergie Atomique, Département de Biologie Moléculaire et Structurale, Laboratoire de Résonance Magnétique en Biologie Métabolique, DSV, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France
²  Institut d'Informatique et Mathématique Appliquées de Grenoble, Laboratoire de Technique de l'Imagerie de la Modélisation et de la Cognition, Faculté de Médecine, Domaine de la Merci, 38706 La Tronche cedex, France

Abstract
The molecular processes by which gravity biological systems are effected by gravity are not understood. Theoreticians have proposed this might mise through the bifurcation properties of certain types of non-linear chemical reactions that self-organise by reaction and diffusion. We have found that in-vitro preparations of microtubules, an important element of the cellular skeleton, show this type of behaviour. The solutions self-organise and the morphology that arises depend upon the sample orientation, with respect to gravity, at a critical moment at an early stage in the development of the self-organised state. As predicted by theories of this type, no self-organisation occurs when the microtubules are assembled under low gravity conditions. At a molecular level this behaviour results fiom an interaction of gravity with macroscopic concentration and density fluctuations arising from processes of microtubule contraction and elongation. Numerical simulations of reaction and diffusion in a population of microtubules, leads to macroscopic self-organisation when a small effect somehow creates an asymmetry in the direction of microtubule growth. This can arise either by a force that slightly favours some microtubule orientations or by an asymmetry in molecular transport and diffusion such as may arise in the presence of gravity.

© EDP Sciences 2001