Trypanosome Cell Biology - CNRS URA 2581  


  HEADDr. BASTIN Philippe / philippe.bastin@pasteur.fr
  MEMBERSBLISNICK Thierry (experimental officer) / BUISSON Johanna (PhD student) / COZANET Anne (secretary) / HUET Diego (PhD student) / Dr. JULKOWSKA Daria (post-doc) / Dr. MARANDE William (post-doc, collaboration with the Museum of Natural History) / Dr. ROTUREAU Brice (post-doc) / SUBOTA Ines (PhD student) / Dr. VINCENSINI Laetitia (post-doc)


  Annual Report

Trypanosomes are flagellated parasites responsible for various tropical diseases, including sleeping sickness in Central Africa caused by Trypanosoma brucei and transmitted by the bite of the tsetse fly. During their life cycle, these parasites have to adapt to changing environments (mammalian bloodstream, insect gut and salivary glands) and undergo profound morphological and biochemical modifications. Trypanosomes also represent exciting model organisms as they exhibit unique cellular features and are amenable to modern reverse genetics technology. Our group is interested in two topics: (1) flagellum formation and function and (2) the dynamics of trypanosome infections in vivo.

Flagellum formation and functions. The flagellum is a cylindrical organelle made of microtubules and composed of more than 200 proteins. We previously demonstrated that the flagellum is critical for the trypanosome cell cycle and that it is constructed by a specific process called intraflagellar transport (IFT). We have visualised IFT for the first time in trypanosomes and have quantified IFT rates of both anterograde and retrograde transport. Our work has revealed the existence of two distinct populations of anterograde particles. Remarkably, these two populations can interact while trafficking, showing large amounts of fusion and fission events. FRAP analysis revealed the dynamics of exchange of IFT proteins between the basal body and the flagellum compartment. We have identified 4 different sub-units of the retrograde motors and discovered their organisation and their role in the entry of various IFT proteins in the flagellum. We discovered a couple of small G proteins that could act as regulators of IFT.

Dynamics of trypanosome infections. In addition to its functions in motility and morphogenesis, the flagellum has been proposed to act as a sensory organelle. We have now purified intact flagella and analysed the content of their membrane and matrix fraction, revealing exciting candidates that are currently under investigation. We identified some putative RNA binding proteins and revealed their importance during the parasite cycle, especially at various stages of trypanosome development in tsetse flies. We have identified a novel step in trypanosome development taking place in the salivary glands. The data demonstrate that trypanosomes use a mixture of symmetric and asymmetric divisions to colonise the epithelium and to produce continuously infective parasites in the saliva. A molecular marker has been identified, showing increased abundance exclusively in the new flagellum of the differentiating cell.

Trypanosome as a model for genetic diseases. Several genetic diseases are linked to defects in cilia and flagella function. Trypanosomes are an excellent model to study these diseases as mammalian, insect or nematode ciliated cells do not propagatein vitro and are poorly amenable to transfection. We are working with clinical groups to understand the role of cilia and flagella in several ciliopathies. We apply our morphological expertise to investigate the structure of cilia in human or mouse cell lines used as models for the comprehension of pathology in nephronophtisis.

Keywords: Trypanosome, flagellum, cytoskeleton, tsetse fly, primary ciliary diskynesia, Bardet-Biedl Syndrome, nephronophtisis

bastin.jpg

Left, ODA7 (green), a cytoplasmic protein involved in flagellum formation with DAPI staining (blue)(L. Vincensini); Middle, section of the base of two trypanosome flagella (J. Buisson); Right, tsetse fly (B. Rotureau)



  Publications

1.Rotureau B, Subota I, Bastin P. (2010) Molecular bases of cytoskeleton plasticity during the Trypanosoma brucei parasite cycle.Cell Microbiol.2010 Dec 16. doi: 10.1111/j.1462-5822.2010.01566.x. PMID: 21159115.

2.Molla-Herman A, Ghossoub R, Blisnick T, Meunier A, Serres C, Silbermann F, Emmerson C, Romeo K, Bourdoncle P, Schmitt A, Saunier S, Spassky N, Bastin P, Benmerah A. (2010).The ciliary pocket: an endocytic membrane domain at the base of primary and motile cilia.

J Cell Sci.2010 May 15;123(Pt 10):1785-95. Epub 2010 Apr 27 (4th most down-loaded paper of the year). PMID: 20427320

3.Demonchy R, Blisnick T, Deprez C, Toutirais G, Loussert C, Marande W, Grellier P, Bastin P, Kohl L. (2009)Kinesin 9 family members perform separate functions in the trypanosome flagellum.J Cell Biol. 187:615-22.PMID: 19948486.

4.ABSALON S., BLISNICK T., BONHIVERS, M., KOHL L., CAYET N., TOUTIRAIS G., BUISSON J., ROBINSON D.R., BASTIN P. (2008) Flagellum elongation is required for correct structure, orientation and function of the flagellar pocket in Trypanosoma brucei. J. Cell Sci., 121, 704-3716. Front cover. PMID: 18940910.

5.ABSALON S., BLISNICK T., KOHL L., TOUTIRAIS G., DORE G., JULKOSWSKA D., TAVENET, A., BASTIN P. (2008) Intraflagellar Transport and Functional Analysis of Genes Required for Flagellum Formation in Trypanosomes. Mol. Biol. Cell19, 929-944. Cited on F1000. PMID: 18094047.





Activity Reports 2010 - Institut Pasteur
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