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New insights on Intraflagellar Transport and flagellum length control in Trypanosoma brucei

Abstract : Cilia and flagella are essential organelles in most eukaryotes including humans. They share a canonical cylindrical structure composed of nine doublets of microtubules called the axoneme that is conserved during evolution. They are built by an active mechanism termed Intraflagellar Transport or IFT. Despite some variations in composition and length between different types of cilia, the length for a given cell type is tightly controlled. Any defect in flagellum length or IFT machinery can lead to serious cellular dysfunctions, including in humans where it is associated to genetic diseases called ciliopathies. During my thesis, we have first investigated the role and functioning of IFT in Trypanosoma brucei a flagellated protozoan parasite that is a powerful model to investigate cilia. Using Focus Ion Beam-Scanning Electron Microscopy (FIB-SEM), we have demonstrated that IFT trains are present almost exclusively on only two out of nine microtubules doublets of the axoneme. Then, the use of high-resolution microscopy allowed us to observe in live cells that two tracks are actually used for bidirectional IFT trafficking. We have investigated mechanisms controlling flagellum length and propose a new model named “grow and lock” where the flagellum elongates at a constant growth-rate until a signal blocks further elongation or shortening. Finally this and other models have been investigated during the parasite cycle, when trypanosomes construct flagella with very different lengths.
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Submitted on : Thursday, October 31, 2019 - 11:27:23 AM
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  • HAL Id : tel-02341168, version 1


Eloïse Bertiaux. New insights on Intraflagellar Transport and flagellum length control in Trypanosoma brucei. Cellular Biology. Sorbonne Université, 2018. English. ⟨NNT : 2018SORUS113⟩. ⟨tel-02341168⟩



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