Thèse Décryptage du Rôle de la Polyglutamylation Post-Traductionnelle des Microtubules dans la Neurodégénérescence Liée à la Protéine Tau H/F - Doctorat.Gouv.Fr

Établissement : Université Paris-Saclay GS Life Sciences and Health École doctorale : Signalisations et Réseaux Intégratifs en Biologie Laboratoire de recherche : Genome, ARN et cancer Direction de la thèse : Maria Magdalena MAGIERA ORCID 0000000348473053 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-05-05T23:59:59 Ce projet propose de déchiffrer le rôle de la polyglutamylation de la tubuline, une modification post-traductionnelle (MPT) du cytosquelette microtubulaire, dans la genèse de la neurodégénérescence liée à la protéine tau. Les microtubules exercent une grande variété de fonctions dans les neurones et doivent être continuellement régulées pour assurer l'homéostasie neuronale. Un concept émergent suggère que les différentes fonctions du cytosquelette microtubulaire sont régulées de manière sélective par les MPT de la tubuline. Nous avons découvert qu'une perturbation de la polyglutamylation de la tubuline entraîne la neurodégénérescence, ce qui suggère que cette modification est essentielle pour le maintien des fonctions des microtubules neuronaux. Nous avons également démontré que les niveaux de polyglutamylation régulent les interactions entre les protéines associées aux microtubules (MAP) et les microtubules. L'une de ces MAP, sensible aux niveaux de polyglutamylation, est la protéine tau, impliquée dans la pathogenèse d'un groupe de troubles neurodégénératifs appelés tauopathies. Nous avons montré que l'absence de polyglutamylation raccourcit encore la durée de vie des souris surexprimant une protéine tau mutante liée à une tauopathie, ce qui suggère que la polyglutamylation pourrait être un facteur méconnu dans le développement de ces maladies. Le projet actuel abordera cette hypothèse en caractérisant de nouveaux modèles murins déjà disponibles dans notre laboratoire, en étudiant les effets sur les neurones primaires dérivés de ces modèles et en analysant le matériel provenant de patients. Nos résultats jetteront les bases du développement de stratégies thérapeutiques pour les maladies neurodégénératives liées aux microtubules et les tauopathies. The microtubule cytoskeleton and its interacting proteins are instrumental for virtually every aspect of neuronal biology. A long-standing question is how the numerous microtubule functions are continuously and precisely coordinated and re-adjusted in morphologically complex and long-lived neurons. Unravelling this issue is of prime importance, as perturbation of microtubule functions is a well-known factor leading to neurodegeneration.
One mechanism allowing to regulate microtubule properties and alter their interaction landscape with effector proteins are tubulin posttranslational modifications. One modification which is particularly highly enriched on neuronal microtubules is polyglutamylation. Our team has shown that controlled levels of this modification are essential for neuronal survival, as both excessive and reduced polyglutamylation lead to neurodegenerative phenotypes. On a mechanistic level we have shown that polyglutamylation controls axonal transport and the interaction between the microtubules and various microtubule -associated protein (MAPs). One of the MAPs sensitive to polyglutamylation is tau, the protein responsible for a group of neurodegenerative diseases called tauopathies.
However, limitations of our previous mouse models of perturbed polyglutamylation prevented us from unequivocally demonstrating the causal link between polyglutamylation levels and neurodegeneration, and from investigating the mechanisms at play. To overcome this, we have now developed novel genetic models (see Methods) which will allow us to investigate the direct link between polyglutamylation and neurodegeneration, and in particular its role in the development of tauopathies. We will also explore whether changing polyglutamylation levels by manipulating polyglutamylating enzymes can mitigate the degenerative phenotypes. This will be relevant for our investigation of therapeutic utility of polyglutamylation modulators in human neurodegenerative diseases. To gain first insights into the potential implication of polyglutamylation in humans, we will also quantify the levels of polyglutamylation in samples from patients of neurodegenerative disorders. The present project aims at determining the causal relationship between perturbed posttranslational polyglutamylation of microtubule and neurodegeneration, and has four main objectives:
1. Analyse the effect of excessive polyglutamylation on brain regions affected by human age-onset neurodegenerative disorders (cortex, hippocampus) using a novel mouse model of locally restricted hyperglutamylation
2. Characterise the impact of reduced polyglutamylation on tauopathy-related neurodegenerative phenotypes in a mouse model of tau mutation linked to frontotemporal dementia (tau P301S).
3. Explore the therapeutic potential of manipulating polyglutamylation on the neurodegenerative phenotypes of tauopathy murine models
4. Investigate the levels of microtubule polyglutamylation in neurodegeneration/tauopathy patient samples.
In this project, we will characterise novel mouse models of perturbed polyglutamylation, use primary neurons derived from those models, and analyse patient samples.
1) To explore the impact of hyperglutamylation on neurodegeneration (Aim 1), we will characterise the CCP1Flox/CCP6Flox/EMX1-cre mouse strain, in which the loss of the two deglutamylase enzymes, and thus hyperglutamylation, is limited to the cerebral cortex and the hippocampus. This alleviates the life-shortening ataxic phenotype of previous hyperglutamylation models (CCP1KO/CCP6KO). It will allow us to investigate long-term effects of excessive polyglutamylation on brain regions associated with human age-onset neurodegenerative disorders (neocortex and hippocampus). These mice have already been generated and are aging. We will:
- Perform the (immuno)histochemical analysis of young (2-month-old) and old (1- and 2-year-old) mouse brains to identify the appearance of degenerative phenotypes,
- Evaluate the behaviour of the animals using the semi-automated Intellicage system.
2) To address the specific impact of polyglutamylation levels on tau pathology (Aim 2), we will take advantage of the frontotemporal dementia-associated mutated tau model (tau P301S), which develops tau pathology and has a highly reduced lifespan. We will first explore microtubule polyglutamylation status in this model. For this we will:
- Quantify the levels of polyglutamylation in tau P301S mice of different ages using the electrochemiluminescence-based Elisa method, which offers high precision and reproducibility
- Quantify the expression levels of the different polyglutamylases (TTLLs) and deglutamylases (CCPs) in different brain regions of the mice of different ages using qPCR and spatial transcriptomics
3) We have shown that lowering polyglutamylation by knocking out TTLL1 polyglutamylase in the context of mutated tau protein (tau P301S) further reduces the lifespan of the animals, suggesting that perturbed polyglutamylation potentiates the development of tauopathic degeneration. To establish whether reduced polyglutamylation causes earlier demise of the tau P301S mice through accelerated tau pathology, we will:
- Compare the progression of the tau pathology in tau P301S and tauP301S/TTLL1KO mice by immunohistochemistry
- Investigate the cognitive behaviour of these mice at different ages in the Intellicage system
- Analyse the primary neurons derived from those mice for microtubule-related phenotypes, such as neurite branching, cargo transport, synapse formation, neuronal activity and redistribution of different MAPs.
4) In aim 3, we will investigate how the modulation of polyglutamylation levels in our mouse models could alleviate the progression of neurodegeneration. To do this, we will:
- Inject adenoviruses expressing TTLLs and CCPs in specific brain regions of tau mutant mice (tau P301S) in change polyglutamylation levels and study the impact on disease progression
- Deplete or overexpress various MAPs that we have shown to be regulated by polyglutamylation levels. Their sensitivity to polyglutamylation could be the cause of the observed degeneration, which is why a re-adjustment of their levels might provide a compensatory effect and alleviate neurodegeneration
- For all tested treatments, we will evaluate the progression of neurodegeneration and cognitive decline.
5) In aim 4, we will characterise samples from human patients of tauopathies by quantifying the levels of microtubule posttranslational modifications using the electrochemiluminescence-based Elisa. This highly sensitive method established in our lab allows us to gain an unbiased quantitative measure of tubulin modifications, and should allow us to pin down whether changes in polyglutamylation are linked to human disorders.

Le candidat retenu aura une formation en biologie cellulaire et en neurosciences, de préférence avec une certaine connaissance du cytosquelette. Il/elle doit avoir un intérêt marqué pour les analyses d'images et les techniques de microscopie de pointe. Il/elle doit être motivé(e) et autonome, et être capable de travailler au sein d'un collectif.