Tuning the adhesive geometry of neurons: length and polarity control.

International audienceNeurons acquire their functional and morphological axo-dendritic polarity by extending, from competing minor processes (neurites), one long axon among numerous dendrites. We employed complementary sets of micropatterns built from 2 and 6 μm wide stripes of various lengths to constrain hippocampal neuron shapes. Using these geometries, we have (i) limited the number of neuronal extensions to obtain a minimal in vitro system of bipolar neurons and (ii) controlled the neurite width during growth by the generation of a progressive cell shape asymmetry on either side of the cellular body. From this geometrical approach, we gained a high level of control of each neurite length and of the localization of axonal specification. To analyze these results, we developed a model based on a width and polarization dependent neurite elongation rate and on the existence of a critical neurite length that sets the axonal fate. Our data on the four series of micro-patterns developed for this study are described by a single set of growth parameters, well supported by experiments. The control of neuronal shapes by adhesive micro-patterns thereby offers a novel paradigm to follow the dynamical process of neurite lengthening and competition through the process of axonal polarization

Geometrical Determinants of Neuronal Actin Waves

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Curvature in Biological Systems: Its Quantification, Emergence, and Implications across the Scales

© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology is supported by numerous experimental and theoretical investigations in recent years. In this review, first, a brief introduction to the key ideas of surface curvature in the context of biological systems is given and the challenges that arise when measuring surface curvature are discussed. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent. On the other hand, summarizing current findings also shows that both single cells and entire cell sheets, tissues or organisms respond to curvature by modulating their shape and their migration behavior. Finally, the interplay between the distribution of morphogens or micro-organisms and the emergence of curvature across length scales is addressed with examples demonstrating these key mechanistic principles of morphogenesis. Overall, this review highlights that curved interfaces are not merely a passive by-product of the chemical, biological, and mechanical processes but that curvature acts also as a signal that co-determines these processes.A.P.G.C. and P.R.F. acknowledge the funding from Fundação para a Ciência e Tecnologia (Portugal), through IDMEC, under LAETA project UIDB/50022/2020. T.H.V.P. acknowledges the funding from Fundação para a Ciência e Tecnologia (Portugal), through Ph.D. Grant 2020.04417.BD. A.S. acknowledges that this work was partially supported by the ATTRACT Investigator Grant (no. A17/MS/11572821/MBRACE, to A.S.) from the Luxembourg National Research Fund. The author thanks Gerardo Ceada for his help in the graphical representations. N.A.K. acknowledges support from the European Research Council (grant 851960) and the Gravitation Program “Materials Driven Regeneration,” funded by the Netherlands Organization for Scientific Research (024.003.013). M.B.A. acknowledges support from the French National Research Agency (grant ANR-201-8-CE1-3-0008 for the project “Epimorph”). G.E.S.T. acknowledges funding by the Australian Research Council through project DP200102593. A.C. acknowledges the funding from the Deutsche Forschungsgemeinschaft (DFG) Emmy Noether Grant CI 203/-2 1, the Spanish Ministry of Science and Innovation (PID2021-123013O-BI00) and the IKERBASQUE Basque Foundation for Science.Peer reviewe

Patologie ermeneutiche ai fini della responsabilita civile dei magistrati

La prima parte del lavoro pone alcune premesse teoriche utili allo svolgimento dell’intero lavoro. In particolare, la candidata ricostruisce in termini teorici il concetto di responsabilità, differenziandone le varie forme di responsabilità giuridica, politica e morale. Propone, dunque, una propria definizione di responsabilità giuridica posta come premessa allo studio dello specifico tema della responsabilità civile dei magistrati. L’analisi prosegue ricostruendo, in termini storici e avendo riguardo ai principii costituzionali rilevanti per la tematica trattata, il ruolo dell’ordine giudiziario e la specifica conformazione dell’attività giudiziaria, anche alla luce delle diverse teorie dell’interpretazione. Infine, viene trattato, mediante una ricostruzione storico-teoretica, il tema della responsabilità dei magistrati nelle forme della responsabilità politica e della responsabilità disciplinare, rinviando al prosieguo del lavoro la trattazione dello specifico versante della responsabilità civile. Nella seconda parte della tesi viene ricostruita l’evoluzione normativa della responsabilità civile dei magistrati, a partire dalla disciplina contenuta nel codice di procedura civile del 1865 fino alle più recenti modifiche del 2015. La ricostruzione normativa tiene conto dei diversi fattori che storicamente hanno influito sulla disciplina in parola: vengono approfondite, in particolare, la giurisprudenza costituzionale dal 1968 fino alle decisioni più recenti e la giurisprudenza sovranazionale, tanto euro-unitaria quanto convenzionale. Nella terza ed ultima parte della tesi la candidata si concentra, con una trattazione critico-evolutiva, sulle teorie del precedente giurisprudenziale, analizzando tutte le diverse decisioni giurisprudenziali riconducibili, anche problematicamente, alla categoria dei precedenti. Vengono prese in considerazione le decisioni della Corte di cassazione, della Corte costituzionale, della Corte di giustizia dell’Unione europea e della Corte europea dei diritti dell’uomo, mettendone in evidenza le peculiarità e gli elementi in comune. Infine, la candidata si interroga sulla funzione che il regime di responsabilità civile del magistrato può assumere per prevenire le patologie ermeneutiche di cui le decisioni giudiziarie possano essere affette, mediante una valorizzazione del ruolo delle decisioni preliminarmente analizzate, evidenziando alcuni aspetti problematici della disciplina in vigore e proponendo puntuali ed alternative soluzioni. In tale prospettiva, inoltre, viene esposta una preferenza per la funzione di “guida” delle interpretazioni qualificate da valorizzare, secondo la posizione della candidata, al fine di garantire, anche per il tramite della legislazione sulla responsabilità civile dei magistrati, la certezza del diritto e, in un’ottica di più ampia portata, il rafforzamento qualitativo della giurisprudenza interna nel dialogo con le Corti sovranazionali

Cellules primaires du cerveau en microenvironnements contrôlés in vitro

The complex structure of the brain is explored by various methods, such as neurophysiology and cognitive neuroscience. This exploration occurs at different scales, from the observation of this organ as a whole entity to molecules involved in biological processes. Here, we propose a study at the cellular scale that focuses on two building elements of brain: neurons and glial cells. Our approach reachs biophysics field for two main reasons: tools that are used and the physical approach to the issues. The originality of our work is to keep close to the in vivo by using primary brain cells in in vitro systems, where chemical and physical environments are controled at micrometric scale. Microelectronic tools are employed to provide a reliable control of the physical and chemical cellular environment. This work focuses on two aspects of brain cell biology: neuronal polarization and glial cell sensitivity to mechanical properties of their environment. As an example, these two issues are involved in injured brains. The first is crucial for the directionality of the transmission of electrical and chemical signals and is associated to a break of symmetry in neuron morphology. The second occurs in recolonization mechanisms of lesions, whose mechanical properties are impaired. During this thesis, quantitative studies are performed on these two cell types, focusing on their growth and their response to geometrical and mechanical constraints. The final aim is to elucidate some molecular mechanisms underlying changes of the cellular structure, and therefore of the cytoskeleton. A significant outcome of this work is the control of the neuronal polarization by a simple control of cell morphology. This result opens the possibility to develop controlled neural architectures in vitro with a single cell precision.Du fait de sa complexité, le fonctionnement du cerveau est exploré par des méthodes très diverses, telles que la neurophysiologie et les neurosciences cognitives, et à des échelles variées, allant de l'observation de l'organe dans son ensemble jusqu'aux molécules impliquées dans les processus biologiques. Ici, nous proposons une étude à l'échelle cellulaire qui s'intéresse à deux briques élémentaires du cerveau : les neurones et les cellules gliales. L'approche choisie est la biophysique, de part les outils utilisés et les questions abordées sous l'angle de la physique. L'originalité de ce travail est d'utiliser des cellules primaires du cerveau dans un souci de proximité avec l'in vivo, au sein de systèmes in vitro dont la structure chimique et physique est contrôlé à l'échelle micrométrique. Utilisant les outils de la microélectronique pour un contrôle robuste des paramètres physico-chimiques de l'environnement cellulaire, ce travail s'intéresse à deux aspects de la biologie du cerveau : la polarisation neuronale, et la sensibilité des cellules gliales aux propriétés mécaniques de leur environnement. A noter que ces deux questions sont étroitement imbriquées lors de la réparation d'une lésion. La première est cruciale pour la directionalité de la transmission de signaux électriques et chimiques et se traduit par une rupture de symétrie dans la morphologie du neurone. La seconde intervient dans les mécanismes de recolonisation des lésions, dont les propriétés mécaniques sont altérées., Les études quantitatives menées au cours de cette thèse portent essentiellement sur la phénoménologie de la croissance de ces deux types de cellules et leur réponse à des contraintes géométriques ou mécaniques. L'objectif in fine est d'élucider quelques mécanismes moléculaires associés aux modifications de la structure cellulaire et donc du cytosquelette. Un des résultats significatifs de ce travail est le contrôle de la polarisation neuronale par le simple contrôle de la morphologie cellulaire. Ce résultat ouvre la possibilité de développer des architectures neuronales contrôlées in vitro à l'échelle de la cellule individuelle

Bending toward differentiation

International audienceBoth biochemical and mechanical signals coordinate all processes at the origin of the formation of functional organs, including tissue folding, cell shape, and differentiation. In this issue of Developmental Cell, Blonski et al. establish a direct consequence of epithelial monolayer folding on nuclear shape and gene expression

Brain cells and neuronal networks: Encounters with controlled microenvironments

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