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> Stages de M2 > Liste des stages proposés pour l’année 2017-2018 > Rôle de l’enveloppe nucléaire durant la meiose

Rôle de l’enveloppe nucléaire durant la meiose

proposé par Julien DUMONT , Institut Jacques Monod 15 rue Hélène Brion75013 Paris

Projet de stage : It is generally accepted that in most species the nuclear envelope does not reassemble between the two meiotic divisions (Dumont and Desai, 2012). Instead, chromosomes stay in a condensed configuration and rapidly realign on the metaphase II plate. However, by performing electron microscopy 3D tomographic reconstructions of anaphase I meiotic spindles in the C. elegans oocyte, we noticed the presence of a membranous structure, reminiscent of a nuclear envelope, on the external surface of the segregating chromosomes. We then followed fluorescently tagged nuclear envelope markers (including inner nuclear envelope or Nuclear Pore Complex (NPC) components) by live imaging during the two rounds of meiotic divisions. We found that several nuclear envelope and NPC components (but not all of them) rapidly reappeared at the external surface of chromosomes after anaphase I onset. Altogether, these preliminary results suggest that a nuclear envelope of partial composition reassembles between meiosis I and II on the external surface of chromosomes in the C. elegans oocyte. The master 2 student will test the potential function of this partial nuclear envelope reformation in meiotic chromosome segregation. We suspect that it may help in mechanically maintaining the chromosomes together by preventing their spatial dispersion during the atypical chromosome segregation that takes place in oocytes (Dumont et al., 2010 ; Laband et al, 2017 in revision). We will first characterize the exact composition and temporal recruitment of components of the partially reforming nuclear envelope. For this we have set up a collaboration with Dr. Peter Askjaer (CABD, Seville, Spain), expert of the nuclear envelope, who has all the necessary tools available. We will then deplete by RNAi key nuclear envelope components alone or in combination and test the effect on meiotic chromosome segregation and partial nuclear envelope reformation in the C. elegans oocyte. We will use a combination of live confocal imaging and 3D electron microscopy assays (Davies et al., 2017 ; Gigant et al., 2017). Overall, the master 2 student will analyze an atypical behavior of nuclear envelope components and potentially identify an unexpected function of the nuclear envelope during meiosis in oocytes.

Techniques mises en œuvre par le stagiaire :
 Utilisation du modèle expérimental C. elegans
 Micro-injection
 Microscopy confocale spinning disc
 Méthodes de transgenèse par MosSci et CRISPR/cas9
 Méthode de clonage rapide par Gibson assembly

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