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Fasciculation axonale et dynamique du cône de croissance en environnement confiné

Abstract : Precise navigation of axons is crucial to establish in vivo neuronal networks. It relies on proper guidance of the growth cone (GC), an actin-rich dynamic structure located at the axonal tip. In vivo, axons ofter progress toward their target by forming bundles. In this study, we use a microfluidic chip composed of axonal microchannels of various widths to induce and study the phenomenon of fasciculation. We show that bundles are built from two populations of axons, i.e. pioneers and followers, characterized by distinct behaviors and GC morphologies. Pioneer axons display an explorative behavior, characterized by a discontinuous growth due to alternance of advancing and pausing periods, while follower axons exhibit a higher growth rate with less frequent pauses. Besides, morphological analysis of GCs reveals that these structures are wider in pioneer axons, while GCs of followers display more elongated shapes. Curiously, confined pioneer GCs into 2 μm wide channels adopt both follower morphologies and dynamics. These results prompting us to wonder about the nature of the link between GC shape and dynamics, we adress this question by investigating the organization and dynamics of the actin filaments (AF) using Spt-PALM. Preliminary results suggest that filament orientation defines a narrower angle in followers and highly confined pioneers than in unconfined pioneers. In addition, measurements of the actin retrograde flow rate (ARF) in GCs reveal a faster flow for unconfined pioneers. The speed of the ARF being inversely proportional to the cell migration speed, these results would explain the respective behaviors of pioneers and followers. Further investigations into quantifying the quantity or density of AF, as well as their coupling to cell adhesion molecules, will allow us to improve our understanding of the molecular mechanisms involved in these two axon populations.
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Submitted on : Friday, April 16, 2021 - 12:36:13 PM
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  • HAL Id : tel-03200222, version 1

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Audric Jan. Fasciculation axonale et dynamique du cône de croissance en environnement confiné. Biologie cellulaire. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLT012⟩. ⟨tel-03200222⟩

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