Réorganisation des compartiments intracellulaires membranaires pendant la mitose

Abstract

Le mécanisme de répartition mitotique du réticulum endoplasmique et des organites à copie unique qui en sont issus, l’appareil de Golgi et l’enveloppe nucléaire, est sujet à controverse. Les approches biochimiques et morphologiques classiques suggéraient que ces organites restaient différenciés pendant toute la mitose, mais sous forme fragmentée, les fragments étant répartis de façon stochastique et passive entre les cellules filles où ils servaient de matrice pour la régénération des organites. Ce modèle est actuellement contesté par l’utilisation de nouvelles techniques d’imagerie permettant l’étude dynamique in vivo des différents compartiments cellulaires. Des résultats récents suggèrent une résorption mitotique de l’appareil de Golgi et de l’enveloppe nucléaire dans le réticulum qui est ensuite réparti dans les cellules filles avant reémergence post-mitotique de ces deux organites. Nous effectuons dans cet article une analyse critique de ces modèles contradictoires.

We discuss the mitotic segregation mechanism of the endoplasmic reticulum, the nuclear envelope and the Golgi apparatus. The results from classical biochemical and morphological studies have suggested that these organites remain distinct during mitosis, although highly fragmented. These fragments were thought to be segregated in a stochatic and passive manner in the two daughter cells where they act as a matrix for the reassembly of the organites. This model has been recently challenged by results obtained using new techniques such as living cells imaging that allow, in real time, studies of the different cell compartments. These results show that the segregation of the mitotic Golgi fragments is an active mechanism involving the spindle microtubules. Furthermore, new results also suggest that the Golgi apparatus and the nuclear envelope lose their identity during mitosis. At the onset of mitosis, they are both absorbed in the endoplasmic reticulum. That is followed by the segregation of this latter organite in the two daughter cells where the two former organites reemerge post-mitotically. Here, we critically analyse these two contradictory models. We also discuss the molecular pathways by which are achieved the disassembly and the reassembly of the nuclear envelope and the Golgi apparatus during mitosis.