The cause of amyotrophic lateral sclerosis (ALS), a cruel neurodegenerative disease, remains unclear. Trans-activating response region (TAR) DNA-binding protein of 43 kDa (TDP-43) has been suggested to have an important role in ALS pathogenesis. In this thesis, we show that a disease linked mutation in matrin 3 (MATR3), a DNA/RNA-binding protein, corresponds to an increased tendency for TDP-43 to aggregate into large and more numerous cytoplasmic inclusions that are the hallmark of ALS. Immunocytochemistry experiments show that MATR3 colocalizes with TDP-43 in vitro. These experiments also show TDP-43 is a component of both MATR3 granules and stress granules, and that MATR3 inclusions are directly adjacent to stress granules or eIF3α inclusions. We hypothesize that, while not being a part of stress granule complex, MATR3 granules are involved in RNA processing via the stress granule pathway by relaying crucial components such as TDP-43. We have also found that compound 8J is able to disaggregate and relocate TDP-43 and MATR3 positive inclusions in vitro. While the mechanism of action of compound 8J remains unclear, fluorescence activated cell sorting (FACS) experiment showed that there was a significant increase in viability in double wild type (matrin 3 and TDP-43) cells when treated with C8J (p-value <.001), which suggests that the TDP-43 and MATR3 cytoplasmic inclusions that were previously observed have a net cytotoxic effect. Together with the in vitro result on C8J, this result also suggests that C8J enhances the survivability of cells by restoring TDP-43 back to the nucleus. MATR3 biochemistry seems to connect to neurodegenerative diseases in several ways. Identifying the pathological connections between MATR3 and TDP-43 physiology will provide us with a greater understanding of ALS pathology.

No description available.

Les dégénérescences lobaires frontotemporales (DLFT) représentent la deuxième étiologie neurodégénérative chez l’adulte de moins de 65 ans. Les DLFT sont constituées d’un ensemble hétérogène de phénotypes cliniques et sont fréquemment héréditaires. Leurs particularités neuropathologiques communes reposent sur une atrophie des lobes frontaux et/ou temporaux associée à la présence d’inclusions de protéines agrégées parmi lesquelles la protéine TAR DNA binding protein 43 (TDP43). Actuellement, aucun marqueur protéique n’est validé pour diagnostiquer les DLFT du vivant du patient.Une cohorte de cas certains DLFT-TDP43 a été constituée grâce au développement d’outils spécifiques de diagnostic moléculaire. Une analyse des concentrations pondérales de protéine TDP43 dans le liquide cérébrospinal (LCS) a été réalisée dans cette cohorte, puis comparée à des cohortes bien caractérisées sur le plan clinique et neuropathologique. Finalement, les profils qualitatifs de la protéine TDP43 ont été étudiés dans différents compartiments accessibles du vivant du patient : les profils des formes solubles (LCS et plasma) et des formes intracellulaires (éléments figurés du sang) de la protéine TDP43 ont été comparés aux profils protéiques obtenus sur des tissus cérébraux présentant des inclusions de protéine TDP43. Les profils protéiques des culots plaquettaires présentent des similitudes avec le tissu cérébral et pourraient devenir un marqueur candidat pour le diagnostic probabiliste des DLFT / Frontotemporal lobar degeneration (FTLD) syndrome is the second most common of presenile dementia. FTLD is a clinically heterogeneous syndrome and comprises many hereditary cases. Common neuropathological features rely on a degeneration of the frontal and/or anterior temporal lobes, associated to specific inclusions of aggregated proteins including TAR DNA binding protein 43 (TDP43). Unfortunately, no practical protein marker is currently validated to improve FTLD diagnosis in living patients.A cohort of FTLD patients with definite TDP43 pathology was defined with the development of specific genetic testing. An analysis of TDP43 concentrations in cerebrospinal fluid (CSF) was performed in this cohort and then compared to other cohorts well-characterized on clinical and neuropathological features. Finally, qualitative patterns of TDP43 were studied in compartments accessible from the patient’s living: profiles of soluble TDP43 protein (in CSF or in plasma) and intracellular TDP43 protein (in the formed elements of blood) were compared to protein patterns observed in brain tissues with TDP43 protein inclusions. Platelet samples exhibit similar characteristics to brain tissue and could become a candidate biomarker for FTLD probabilistic diagnosis

No description available.