Ref HAL: hal-03291847_v1
PMID 31732791
DOI: 10.1007/s00018-019-03372-2
WoS: 000560212600012
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Résumé:

During embryogenesis of all vertebrates, haematopoietic stem/progenitor cells (HSPCs) extrude from the aorta by a complex process named endothelial-to-haematopoietic transition (EHT). HSPCs will then colonize haematopoietic organs allowing haematopoiesis throughout adult life. The mechanism underlying EHT including the role of each aortic endothelial cell (EC) within the global aorta dynamics remains unknown. In the present study, we show for the first time that EHT involves the remodelling of individual cells within a collective migration of ECs which is tightly orchestrated, resulting in HSPCs extrusion in the sub-aortic space without compromising aorta integrity. By performing a cross-disciplinary study which combines high-resolution 4D imaging and theoretical analysis based on the concepts of classical mechanics, we propose that this complex developmental process is dependent on mechanical instabilities of the aorta preparing and facilitating the extrusion of HSPCs.

Commentaires: NOTICE A REPRENDRE PAS DE CLE UT AU 15/07

Ref HAL: hal-01996796_v1
DOI: 10.1101/509190
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Résumé:

During embryogenesis of all vertebrates, haematopoietic stem/progenitor cells 16 (HSPCs) extrude from the aorta by a complex process named Endothelial-to-17 Haematopoietic Transition (EHT). HSPCs will then colonize haematopoietic organs 18 allowing haematopoiesis throughout adult life. The mechanism underlying EHT 19 including the role of each aortic endothelial cell within the global aorta dynamics 20 remains unknown. In the present study, we show for the first time that EHT involves the 21 remodelling of individual cells within a collective migration of endothelial cells which is 22 tightly orchestrated, resulting in HSPCs extrusion in the sub-aortic space without 23 compromising aorta integrity. By performing a cross-disciplinary study which combines 24 high resolution 4D imaging and theoretical analysis based on the concepts of classical 25 mechanics, we propose that this complex developmental process is dependent on 26 mechanical instabilities of the aorta preparing and facilitating the extrusion of HSPCs. 27 28 29 We dedicate this work to the memory of our friend and colleague, V. Lorman. 30 31 All rights reserved. No reuse allowed without permission. (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

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We model the ParABS system, which is a bacterial DNA Segregation Apparatus.

Ref HAL: hal-01493262_v1
Ref Arxiv: 1702.07372
DOI: 10.1103/PhysRevLett.119.028101
WoS: 000405367800016
Ref. & Cit.: NASA ADS
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14 Citations
Résumé:

Efficient bacterial chromosome segregation typically requires the coordinated action of a three-component machinery, fueled by adenosine triphosphate, called the partition complex. We present a phenomenological model accounting for the dynamic activity of this system that is also relevant for the physics of catalytic particles in active environments. The model is obtained by coupling simple linear reaction-diffusion equations with a proteophoresis, or “volumetric” chemophoresis, force field that arises from protein-protein interactions and provides a physically viable mechanism for complex translocation. This minimal description captures most known experimental observations: dynamic oscillations of complex components, complex separation, and subsequent symmetrical positioning. The predictions of our model are in phenomenological agreement with and provide substantial insight into recent experiments. From a nonlinear physics view point, this system explores the active separation of matter at micrometric scales with a dynamical instability between static positioning and traveling wave regimes triggered by the dynamical spontaneous breaking of rotational symmetry.

Commentaires: 6 pages, 3 figures

Ref HAL: hal-01950249_v1
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Bacteria, a few μm in length, have the feature to store the genome in a subvolume of the cell without membrane. The bacterial cell cycle relies on a series of essential processes such as DNA replication, transcription and segregation. The mechanisms driving segregation of the genome are still unclear, mainly because the processes overlap in time and take place in the same cellular compartment. The active ParABS partition system is the only type known on chromosomes and is prevalent on low-copy number plasmids,namely the F-plasmid involved in bacterial resistance to antibiotics. ParABS is composed of three components: the proteins ParA and ParB, respectively a molecular motor (ATPase) and a binding protein, and parS, a sequence of specific binding sites. We describe the organization and architecture of the partition complex. Our model is supported by experimental data from ChIP-sequencing (LMGM, Toulouse) and super resolution microscopy techniques (CBS, Montpellier).

Ref HAL: hal-01950151_v1
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We model the ParABS system, which is a bacterial DNA Segregation Apparatus.

Ref HAL: hal-01529981_v1
PMID 28000047
DOI: 10.1140/epje/i2016-16128-0
WoS: 000397028700001
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The tubular lipid membranes (TLMs) pulled out from vesicles are often used in in vitro studies of the interactions between curvature-inducing proteins and highly curved membranes. The protein molecules adsorbed at the membrane surface deform the TLM and couple with each other due to the induced strain. Here we propose an approach which models the single curvature-inducing protein action on the lipid bilayer by the multipole, the superposition of the point forces applied to the membrane in the region of the protein adsorption. We show that to be localized in the area of the protein size at the TLM surface, the force multipoles satisfying the mechanical equilibrium conditions should be composed of three or more point forces. The protein coupling energy mediated by the membrane strain is studied in detail. In the region of the tubular membrane stability the maximal distance between two neighboring interacting protein-induced force multipoles is estimated to be of the order of the TLM cross section perimeter. In the vicinity of the TLM instability in the region of the vanishing stretching force applied to the TLM, the interaction radius increases drastically. The high affinity of the single curvature-inducing protein molecule to the regions in the vicinity of the TLM ends is explained and related to the boundary conditions in the experimental set-ups. The reasons for the aggregate formation on the membrane surface are also discussed.