Marie-Christine Galas

Beneficial effects of exercise in a transgenic mouse model of Alzheimer's disease-like Tau pathology.

Tau pathology is encountered in many neurodegenerative disorders known as tauopathies, including Alzheimers disease. Physical activity is a lifestyle factor affecting processes crucial for memory and synaptic plasticity. Whether long-term voluntary exercise has an impact on Tau pathology and its pathophysiological consequences is currently unknown. To address this question, we investigated the effects of long-term voluntary exercise in the THY-Tau22 transgenic model of Alzheimers disease-like Tau pathology, characterized by the progressive development of Tau pathology, cholinergic alterations and subsequent memory impairments. Three-month-old THY-Tau22 mice and wild-type littermates were assigned to standard housing or housing supplemented with a running wheel. After 9 months of exercise, mice were evaluated for memory performance and examined for hippocampal Tau pathology, cholinergic defects, inflammation and genes related to cholesterol metabolism. Exercise prevented memory alterations in THY-Tau22 mice. This was accompanied by a decrease in hippocampal Tau pathology and a prevention of the loss of expression of choline acetyltransferase within the medial septum. Whereas the expression of most cholesterol-related genes remained unchanged in the hippocampus of running THY-Tau22 mice, we observed a significant upregulation in mRNA levels of NPC1 and NPC2, genes involved in cholesterol trafficking from the lysosomes. Our data support the view that long-term voluntary physical exercise is an effective strategy capable of mitigating Tau pathology and its pathophysiological consequences.

Amyloid Precursor Protein (APP) Metabolites APP Intracellular Fragment (AICD), Aβ42, and Tau in Nuclear Roles

Amyloid precursor protein (APP) metabolites (amyloid-β (Aβ) peptides) and Tau are the main components of senile plaques and neurofibrillary tangles, the two histopathological hallmarks of Alzheimer disease. Consequently, intense research has focused upon deciphering their physiological roles to understand their altered state in Alzheimer disease pathophysiology. Recently, the impact of APP metabolites (APP intracellular fragment (AICD) and Aβ) and Tau on the nucleus has emerged as an important, new topic. Here we discuss (i) how AICD, Aβ, and Tau reach the nucleus and how AICD and Aβ control protein expression at the transcriptional level, (ii) post-translational modifications of AICD, Aβ, and Tau, and (iii) what these three molecules have in common.

Atypical, non-standard functions of the microtubule associated Tau protein

Since the discovery of the microtubule-associated protein Tau (MAPT) over 40 years ago, most studies have focused on Tau’s role in microtubule stability and regulation, as well as on the neuropathological consequences of Tau hyperphosphorylation and aggregation in Alzheimer’s disease (AD) brains. In recent years, however, research efforts identified new interaction partners and different sub-cellular localizations for Tau suggesting additional roles beyond its standard function as microtubule regulating protein. Moreover, despite the increasing research focus on AD over the last decades, Tau was only recently considered as a promising therapeutic target for the treatment and prevention of AD as well as for neurological pathologies beyond AD e.g. epilepsy, excitotoxicity, and environmental stress. This review will focus on atypical, non-standard roles of Tau on neuronal function and dysfunction in AD and other neurological pathologies providing novel insights about neuroplastic and neuropathological implications of Tau in both the central and the peripheral nervous system.

Tau monoclonal antibody generation based on humanized yeast models: impact on Tau oligomerization and diagnostics.

Background: Oligomers of protein Tau are associated with neurodegenerative diseases. Results: New antibodies were generated and validated that recognize different degrees of oligomerization of protein Tau. Conclusion: Low order and higher order oligomers differ in C-terminal Tau phosphorylation and reflect consecutive stages in disease progression. Significance: Antibodies recognizing Tau oligomers provide insight into disease etiology and are promising diagnostic tools. A link between Tau phosphorylation and aggregation has been shown in different models for Alzheimer disease, including yeast. We used human Tau purified from yeast models to generate new monoclonal antibodies, of which three were further characterized. The first antibody, ADx201, binds the Tau proline-rich region independently of the phosphorylation status, whereas the second, ADx215, detects an epitope formed by the Tau N terminus when Tau is not phosphorylated at Tyr18. For the third antibody, ADx210, the binding site could not be determined because its epitope is probably conformational. All three antibodies stained tangle-like structures in different brain sections of THY-Tau22 transgenic mice and Alzheimer patients, and ADx201 and ADx210 also detected neuritic plaques in the cortex of the patient brains. In hippocampal homogenates from THY-Tau22 mice and cortex homogenates obtained from Alzheimer patients, ADx215 consistently stained specific low order Tau oligomers in diseased brain, which in size correspond to Tau dimers. ADx201 and ADx210 additionally reacted to higher order Tau oligomers and presumed prefibrillar structures in the patient samples. Our data further suggest that formation of the low order Tau oligomers marks an early disease stage that is initiated by Tau phosphorylation at N-terminal sites. Formation of higher order oligomers appears to require additional phosphorylation in the C terminus of Tau. When used to assess Tau levels in human cerebrospinal fluid, the antibodies permitted us to discriminate patients with Alzheimer disease or other dementia like vascular dementia, indicative that these antibodies hold promising diagnostic potential.

Tau/DDX6 interaction increases microRNA activity

Tauopathies, such as Alzheimers disease, are characterized by intracellular aggregates of insoluble Tau proteins. Originally described as a microtubule binding protein, recent studies demonstrated additional physiological roles for Tau. The fact that a single protein can regulate multiple cellular functions has posed challenge in terms of understanding mechanistic cues behind the pathology. Here, we used tandem-affinity purification methodology coupled to mass spectrometry to identify novel interaction partners. We found that Tau interacts with DDX6, a DEAD box RNA helicase involved in translation repression and mRNA decay as well as in the miRNA pathway. Our results demonstrate that Tau increases the silencing activity of the miRNA let-7a, miR-21 and miR-124 through DDX6. Importantly, Tau mutations (P301S, P301L) found in the inherited tauopathies, frontotemporal dementia and parkinsonism linked to chromosome 17, disrupt Tau/DDX6 interaction and impair gene silencing by let-7a. Altogether, these data demonstrated a new unexpected role for Tau in regulating miRNA activity.

P1-20 Effets de l’exercice volontaire à long terme dans un modèle de souris transgénique THY-Tau22 développant une pathologie Tau similaire à celle observée dans la maladie d’Alzheimer

Introduction La maladie d’Alzheimer est une maladie neurodegenerative caracterisee par des depots amyloides et une degenerescence neurofibrillaire (DNF). Cette derniere est constituee d’agregats de proteines Tau hyper- et anormalement phosphorylees et sa progression est correlee avec celle des deficits cognitifs. Afin de modeliser la pathologie Tau, nous avons genere un nouveau modele de souris transgenique Tau (THY-Tau22) dans lequel nous testons certains paradigmes. Ainsi, l’activite physique previent le declin cognitif et retarde le debut des demences. Materiels et methodes La lignee Thy-Tau22 a ete caracterisee dans une cinetique d’un point de vue comportemental (Y maze). Des etudes immunohistochimiques sur la pathologie Tau et le systeme cholinergique ont ete realisees. Des souris THY-Tau22 et “littermates” âgees de 3 mois ont ete soumises a l’exercice volontaire ad libitum durant 9 mois. Les memes etudes ont ensuite ete realisees. Resultats Dans les Thy-Tau22, la DNF se developpe progressivement dans l’hippocampe A l’âge de 12 mois, les souris THYTau22 presentent une pathologie Tau septo-hippocampique accompagnee par une alteration du transport retrograde au sein de ce tractus. Une perte des neurones cholinergiques est egalement observee. Nous avons evalue les effets de l’exercice volontaire dans notre lignee THY-Tau22. Apres cette periode d’exercice, nous avons observe, par le test du Y-maze, que les souris THY-Tau22 ayant acces a une roue presentaient une amelioration mnesique significative par rapport aux souris THY-Tau22 ne pratiquant pas d’exercice. Cette amelioration de la memoire est accompagnee d’une forte augmentation des niveaux de BDNF hippocampique suggerant que ce facteur puisse jouer un role important. De plus, la perte des neurones cholinergiques observee chez les souris THY-Tau22 est prevenue par l’exercice volontaire. L’analyse de l’agregation de la proteine Tau chez les souris THY-Tau22 sera presentee. Conclusions Dans l’ensemble, nos resultats montrent que l’exercice physique a long terme est capable d’ameliorer les deficits cognitifs engendres par la pathologie Tau et suggerant un effet benefique potentiel dans la maladie d’Alzheimer ainsi que dans les autres Tauopathies. Ce travail a beneficie du support du CNRS, Inserm, Region Nord/Pas-de-Calais, Univ. Lille2, CHU-Lille, Communaute Europeenne (FP7 MEMOSAD) et ANR (ADONTAGE et AMYTOXTAU).

P1-7 La synphiline-1 favorise l’agrégation et la toxicité de l’α-synucléine dans un modèle de levure de la maladie de Parkinson

Introduction La maladie de Parkinson se caracterise par une perte neuronale dans la substance noire due a l’agregation intraneuronale de proteines. Ces agregats appeles des corps de Lewy sont principalement composes d’α-synucleine, une proteine pre-synaptique liee a la maladie de Parkinson en raison de la duplication, triplication ou de la presence de mutation (A30P, A53T, E49K) dans des familles de patients. Materiels et methodes Afin d’etudier des aspects fondamentaux de la maladie de Parkinson, nous avons developpe des modeles de levures bases sur l’expression heterologue d’α-synucleine humaine. Ces modeles ont ete utilises pour etudier l’agregation, des modifications post-traductionnelles et la toxicite de cette proteine. Afin d’approfondir l’analyse de l’implication de l’α-synucleine et les evenements conduisant a la maladie de Parkinson, nous avons co-exprime la synphiline-1 dans nos modeles. La synphiline-1 est un partenaire connu de l’α-synucleine presente dans les corps de Lewy et est mutee dans une famille allemande presentant une pathologie de Parkinson. Les modeles sont bases sur l’expression de synphiline-1 mutee ou sauvage, avec ou sans co-expression d’α-synucleine dans des levures Saccharomyces cerevisiae. Resultats Quand elle est exprimee dans des levures, l’α-synucleine est localisee au niveau de la membrane plasmique ou elle interagit avec des “domaines membranaires resistants aux detergents” (DRMD), forment des inclusions β-sheet positive et induit une toxicite. La synphiline-1 est principalement cytoplasmique. Cependant cette proteine forme egalement des inclusions dans une sous-population de levures ou elle interagit avec les DRMD. De plus, la synphiline-1 augmente la formation d’inclusion et la toxicite induite par l’α-synucleine dans les levures. Les effets de la synphiline-1 sur l’agregation d’α-synucleine suggerent que la synphiline-1 pourrait etre un facteur de risque supplementaire dans la pathogenese de la maladie de Parkinson.