title: Active diffusion positions the nucleus in mouse oocytes.
abstract: In somatic cells, the position of the cell centroid is dictated by the centrosome. The centrosome is instrumental in nucleus positioning, the two structures being physically connected. Mouse oocytes have no centrosomes, yet harbour centrally located nuclei. We demonstrate how oocytes define their geometric centre in the absence of centrosomes. Using live imaging of oocytes, knockout for the formin 2 actin nucleator, with off-centred nuclei, together with optical trapping and modelling, we discover an unprecedented mode of nucleus positioning. We document how active diffusion of actin-coated vesicles, driven by myosin Vb, generates a pressure gradient and a propulsion force sufficient to move the oocyte nucleus. It promotes fluidization of the cytoplasm, contributing to nucleus directional movement towards the centre. Our results highlight the potential of active diffusion, a prominent source of intracellular transport, able to move large organelles such as nuclei, providing in vivo evidence of its biological function.
authors.affiliation: CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe Labellisée Ligue Contre le Cancer, Paris F-75005, France.
authors.forename: Maria
authors.initials: M
authors.lastname: Almonacid
authors.affiliation: 1] Institut Curie, Centre de Recherche, Laboratoire Physico-Chimie, Paris F-75248, France [2] CNRS-UMR168, Paris F-75248, France [3] UPMC, 4 Place Jussieu, Paris F-75005, France.
authors.forename: Wylie W
authors.initials: WW
authors.lastname: Ahmed
authors.affiliation: 1] Institut Curie, Centre de Recherche, Laboratoire Physico-Chimie, Paris F-75248, France [2] CNRS-UMR168, Paris F-75248, France [3] UPMC, 4 Place Jussieu, Paris F-75005, France.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bussonnier
authors.affiliation: CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe Labellisée Ligue Contre le Cancer, Paris F-75005, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Mailly
authors.affiliation: 1] Institut Curie, Centre de Recherche, Laboratoire Physico-Chimie, Paris F-75248, France [2] CNRS-UMR168, Paris F-75248, France [3] UPMC, 4 Place Jussieu, Paris F-75005, France.
authors.forename: Timo
authors.initials: T
authors.lastname: Betz
authors.affiliation: UMR7600-CNRS/UPMC, 4 Place Jussieu Paris F-75005, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Voituriez
authors.affiliation: Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Nir S
authors.initials: NS
authors.lastname: Gov
authors.affiliation: CIRB, Collège de France, and CNRS-UMR7241 and INSERM-U1050, Equipe Labellisée Ligue Contre le Cancer, Paris F-75005, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Verlhac
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000502:physiology*; D018699:Coated Vesicles / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology*; D003595:Cytoplasmic Streaming / Q000187:drug effects / Q000502:physiology*; D005260:Female; D000080865:Formins; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics* / Q000494:pharmacology; D008870:Microtubules / Q000502:physiology; D024462:Myosin Type II / Q000378:metabolism; D024701:Myosin Type V / Q000378:metabolism; D009419:Nerve Tissue Proteins; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics* / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology*; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D000199:Actins; D000080865:Formins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D050257:Tubulin Modulators; C549436:formin 2 protein, mouse; D024462:Myosin Type II; D024701:Myosin Type V; D015739:Nocodazole