title: Microtubule-induced nuclear envelope fluctuations control chromatin dynamics in Drosophila embryos.
abstract: Nuclear shape is different in stem cells and differentiated cells and reflects important changes in the mechanics of the nuclear envelope (NE). The current framework emphasizes the key role of the nuclear lamina in nuclear mechanics and its alterations in disease. Whether active stress controls nuclear deformations and how this stress interplays with properties of the NE to control NE dynamics is unclear. We address this in the early Drosophila embryo, in which profound changes in NE shape parallel the transcriptional activation of the zygotic genome. We show that microtubule (MT) polymerization events produce the elementary forces necessary for NE dynamics. Moreover, large-scale NE deformations associated with groove formation require concentration of MT polymerization in bundles organized by Dynein. However, MT bundles cannot produce grooves when the farnesylated inner nuclear membrane protein Kugelkern (Kuk) is absent. Although it increases stiffness of the NE, Kuk also stabilizes NE deformations emerging from the collective effect of MT polymerization forces concentrated in bundles. Finally, we report that MT-induced NE deformations control the dynamics of chromatin and its organization at steady state. Thus, the NE is a dynamic organelle, fluctuations of which increase chromatin dynamics. We propose that such mechanical regulation of chromatin dynamics by MTs might be important for gene regulation.
authors.affiliation: IBDML, UMR6216 CNRS-Université de la Méditerranée, Campus de Luminy, Case 907, 13288 Marseille Cedex 09, France.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hampoelz
authors.forename: Yannick
authors.initials: Y
authors.lastname: Azou-Gros
authors.forename: Roxane
authors.initials: R
authors.lastname: Fabre
authors.forename: Olga
authors.initials: O
authors.lastname: Markova
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Puech
authors.forename: Thomas
authors.initials: T
authors.lastname: Lecuit
mesh_terms: D000818:Animals; D048430:Cell Shape; D002843:Chromatin; D004331:Drosophila melanogaster / Q000166:cytology* / Q000196:embryology*; D008870:Microtubules; D009685:Nuclear Envelope
chemical_list: D002843:Chromatin