The Flagellar Arginine Kinase in Trypanosoma brucei Is Important for Infection in Tsetse Flies

African trypanosomes are flagellated parasites that cause sleeping sickness. Parasites are transmitted from one mammalian host to another by the bite of a tsetse fly. Trypanosoma brucei possesses three different genes for arginine kinase (AK) including one (AK3) that encodes a protein localised to the flagellum. AK3 is characterised by the presence of a unique amino-terminal insertion that specifies flagellar targeting. We show here a phylogenetic analysis revealing that flagellar AK arose in two independent duplication events in T. brucei and T. congolense, the two species of African trypanosomes that infect the tsetse midgut. In T. brucei, AK3 is detected in all stages of parasite development in the fly (in the midgut and in the salivary glands) as well as in bloodstream cells, but with predominance at insect stages. Genetic knockout leads to a slight reduction in motility and impairs parasite infectivity towards tsetse flies in single and competition experiments, both phenotypes being reverted upon expression of an epitope-tagged version of AK3. We speculate that this flagellar arginine kinase is important for T. brucei infection of tsetse, especially in the context of mixed infections and that its flagellar targeting relies on a system equivalent to that discovered for calflagins, a family of trypanosome flagellum calcium binding proteins

Research on rare diseases:ten years of progress and challenges at IRDiRC

The International Rare Diseases Research Consortium (IRDiRC) is a global collaborative initiative launched in 2011, aimed at tackling rare diseases through research. Here, we summarize IRDiRC’s vision and goals and highlight achievements and prospects after its first decade.</p

Advancing diagnosis and research for rare genetic diseases in indigenous peoples

Achieving a diagnosis for Indigenous people living with a rare, often genetic, disease is crucial for equitable healthcare. The International Rare Disease Research Consortium convened a global Task Force to bridge the gap in diagnosing Indigenous rare diseases, and identify solutions to tackle the health inequity faced by Indigenous people.The IRDiRC Indigenous Population Task Force was supported by the Scientific Secretariat of IRDiRC, funded by the European Union through the European Joint Programme on Rare Disease (EJP RD) under the European Union’s Horizon 2020 Research and Innovation Programme.https://www.nature.com/ng2024-08-08hj2024BiochemistryGeneticsMicrobiology and Plant PathologySDG-03:Good heatlh and well-beingSDG-10:Reduces inequalitie

A cytological, genetic and physical analysis of the process of swarming in Bacillus subtilis

Le phénomène de "swarming", c'est-à-dire la migration en masse, coordonnée et rapide, des cellules sur une surface, a été observé chez de nombreuses bactéries. Cependant, le mécanisme du contrôle de ce processus de développement reste inconnu. Il était donc important de définir précisément les conditions requises pour le processus de "swarming" chez Bacillus subtilis en analysant chacune des étapes au niveau macroscopique et microscopique, grâce à la vidéo en time-lapse, in situ, sans perturber les cellules. Ce travail a permis de mettre en évidence de nombreux caractères nouveaux du processus de "swarming", qui, dans le cas de B. subtilis, est remarquablement complexe. Les résultats ont montré des vagues successives de migration avec formation de dendrites ramifiées complexes. Des groupes de cellules étroitement associées et avançant de manière coopérative ont été observés à l'extrémité des dendrites. Trois types de cellules ont été observés dans la communauté, y compris des "rafts" formant une monocouche de type "cristallin", à la base inférieure des dendrites matures. Grâce à une approche génétique, j'ai démontré que la surfactine produite par B. subtilis est essentiel pour le processus de "swarming" sur milieu synthétique B. J'ai aussi démontré l'existence d'un deuxième voie indépendante de la surfactine, sur milieu riche. L'analyse de mutants défectifs pour des systèmes de "quorum sensing", a démontré que la voie dépendante de la surfactine dépend vraisemblablement de molécules de signalisation. Enfin, les études concernant les propriétés physiques de la surfactine montrent que la surfactine purifiée s'étale en formant des "dendrites".Many bacteria have been shown to swarm, that is the cooperative rapid mass migration of cells over a surface. However, the mechanism underlying the control of this developmental process or the basis of coordinated behaviour that facilitates rapid migration, remains completely unclear. Therefore, in my studies, it was important to define precisely the conditions required for swarming in Bacillus subtilis, documenting each stage, both macroscopically and microscopically, by manual and time-lapse photography of the expanding community, in situ, without disturbing the cells. This has yielded many novel features of the swarming process, which in B. subtilis is particularly remarkable and complex. On a synthetic medium, successive waves of swarming, followed by consolidation, were observed, forming highly intricate branching patterns of dendrites. Packs of closely associated bacteria, advancing cooperatively, were observed at the tips of dendrites. At least three types of cells were observed in the community, including crystalline' arrays of closely packed rafts of cells, at the base of mature dendrites. Using a genetic approach I have demonstrated that surfactin produced in B. subtilis, is essential for swarming on the synthetic B medium. I also demonstrated a surfactin independent pathway for swarming on a rich medium. Analysis of mutants defective in quorum sensing demonstrated that the surfactin independent pathway is likely dependent on signalling molecules. Finally, in studies concerning the physical properties of surfactin and its role in swarming, the results included the demonstration that pure surfactin when spreading forms dendrites'.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

COVID-19 and rare diseases: reflections and recommendations by the International Rare Diseases Research Consortium

Aim: The ambitious goals set by the International Rare Diseases Research Consortium (IRDiRC) by 2027 to fulfill the vision of providing diagnosis and treatments to rare diseases (RDs) patients within one year of coming to medical attention have been challenged by the COVID-19 pandemic. This article aims to identify the needs and challenges of the RD community during the COVID-19 pandemic and to understand whether the pandemic would hinder achievement of the IRDiRC goals.Methods: A survey was developed in 2020 to answer key issues related to the potential impact of the pandemic on RD research and distributed to all 96 IRDiRC Constituent Committee members and Scientific Committee experts.Results: The overall participation rate was 46%, with the highest response rates from the Patient Advocates, Funders, and Therapies Committees. Most respondents reported impacts on various aspects of RD research including decreased access to healthcare, clinical trials, and diagnostics for patients, as well as disrupted operations for patient and funding organizations and restrictions in access to workplaces for researchers. Despite these challenges, there was overall optimism that the IRDiRC goals could still be met by 2027, although there would be an inevitable slowdown in RD research activities.Conclusions: Maintaining funding for RD research and implementing new workflows to ensure that patients have continued access to diagnostics, therapies, and clinical trials will be key to ensuring that IRDiRC meets it goals by 2027

Flagellar adhesion in Trypanosoma brucei relies on interactions between different skeletal structures in the flagellum and cell body

International audienceThe Trypanosoma brucei flagellum is an essential organelle anchored along the surface of the cell body through a specialized structure called the flagellum attachment zone (FAZ). Adhesion relies on the interaction of the extracellular portion of two transmembrane proteins, FLA1 and FLA1BP. Here, we identify FLAM3 as a novel large protein associated with the flagellum skeleton whose ablation inhibits flagellum attachment. FLAM3 does not contain transmembrane domains and its flagellar localization matches closely, but not exactly, that of the paraflagellar rod, an extra-axonemal structure present in the flagellum. Knockdown of FLA1 or FLAM3 triggers similar defects in motility and morphogenesis, characterized by the assembly of a drastically reduced FAZ filament. FLAM3 remains associated with the flagellum skeleton even in the absence of adhesion or a normal paraflagellar rod. However, the protein is dispersed in the cytoplasm when flagellum formation is inhibited. By contrast, FLA1 remains tightly associated with the FAZ filament even in the absence of a flagellum. In these conditions, the extracellular domain of FLA1 points to the cell surface. FLAM3 is essential for proper distribution of FLA1BP, which is restricted to the most proximal portion of the flagellum upon knockdown of FLAM3. We propose that FLAM3 is a key component of the FAZ connectors that link the axoneme to the adhesion zone, hence it acts in an equivalent manner to the FAZ filament complex, but on the side of the flagellum

Ethical, legal, and social issues (ELSI) in rare diseases: a landscape analysis from funders

Recent interest in personalized medicine has highlighted the importance of research in ethical, legal, and social issues (ELSI). Issues in ELSI research may be magnified in the rare diseases population (i.e., small numbers of affected individuals, challenges in maintaining confidentiality, and paucity of treatments for diseases where natural history information may be limited). More than other areas of research, potential barriers include the lack of funding opportunities and appropriate review processes for applications to funding agencies. The ELSI Working Group of the International Rare Diseases Research Consortium (IRDiRC) performed an informal survey on ELSI funding initiatives to learn more about different funding mechanisms and to identify potential gaps in funding opportunities. The Working Group discusses these challenges and highlights the role of funding agencies and partners such as patient advocacy groups, specialists in social sciences and humanities, and clinicians to advance ELSI research in rare diseases