The 43 kDa TAR DNA binding protein (TDP-43) has been identified as one of the major proteins that accumulates in the cytoplasm of brain and spinal cord from the patients affected with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Under basal conditions, TDP-43 localizes in nucleus functioning as an RNA binding protein to regulate different aspects of RNA metabolism, such as alternative splicing of messenger RNA. In ALS/FTLD brains and spinal cords, TDP-43 forms well-defined cytoplasmic granules, the behavior very similar to stress granule (SG) proteins, but the mechanisms are poorly understood. To investigate the mechanism of TDP-43 granule formation and to identify potential therapeutic targets by inhibiting the granule formation, our laboratory screened a chemical library of 75,000 compounds using the inducible PC12 cells that express EGFP-tagged wild-type human TDP-43. We used the biological effect of cycloheximide on SGs as a basis for the screen, since it is known to prevent the formation of SGs and TDP-43 granules, pointing to a novel biological pathway that regulates TDP-43 granule formation. One of the candidate compounds, Compound 8 (C8) and its analog C8j dose- dependently decreased the arsenite-induced TDP-43 granules without cytotoxicity, and reduced the protein levels of full-length, truncated, high molecular weight and phosphorylated TDP-43. In addition, we found C8j reduced the phosphorylation at novel, previously unknown Thr103-Ser104 amino acid residues of human TDP-43 under arsenite stress. The phospho-mimetic mutations at these sites induced spontaneous intracellular TDP-43 granules, indicating their regulatory role in TDP-43 granule formation. We also performed a series of gene expression analysis combined with the systems biology algorithm, mode of action by network identification (MNI), to identify the mode of action of C8, and found C8 potentially targets protein metabolism and modification processes to reduce the TDP-43 granules. Our study identified a family of non-cytotoxic chemical compounds that reduces the formation of arsenite-induced TDP-43 granules and their potential mode of action. Furthermore, we identified previously unknown TDP-43 phosphorylation sites Thr103- Ser104 that are involved in the TDP-43 granule formation. We anticipate this study will elucidate the biological pathways regulating TDP-43 aggregation and potential therapeutics for ALS/FTLD-U.

Les troubles neurodégénératifs, tels que la sclérose latérale amyotrophique (SLA) et la démence frontotemporale (DFT), ont été associés aux protéines de liaison à l'ARN (RBP). Les principales caractéristiques de la SLA sont l'agrégation d'une protéine de liaison à l'ARN appelée protéine de liaison TAR (TDP-43). Il a été démontré que TDP-43 se lie à G3BP1, un facteur de nucléation pour l'assemblage des granules de stress, pour le stabiliser. Les granules de stress sont des structures séparées par phases qui se forment dans des conditions stressantes et favorisent la survie cellulaire. Une altération de l’assemblage des granules de stress et une réduction du G3BP1 sont signalées dans la SLA. Cette réduction est due à un défaut dans les transcriptions codantes pour G3BP1 stabilisant TDP-43. Par conséquent, une réponse défaillante des granules de stress pourrait jouer un rôle majeur dans la maladie. Ainsi, ce projet de recherche se concentre sur la restauration de G3BP1, dont la déplétion est liée à la perte de fonction de TDP-43. En utilisant des composés de petites molécules identifiés lors d'une campagne de dépistage de médicaments, nous cherchons à augmenter l'expression de G3BP1, rétablissant ainsi le mécanisme SG endogène et favorisant la survie neuronale. La découverte de candidats principaux (NPX-047, NPX-000-115 et NPX-001-280) qui sauvent efficacement l'expression et la fonction de G3BP1 est prometteuse pour des thérapies potentielles contre la SLA. Ces composés ont été testés sur des cellules SHSY5Y traitées avec du si-TDP, mais aucune récupération de l'ARNm de G3BP1 n'a été observée malgré des niveaux plus élevés de signaux de luciférase. Ainsi, une enquête approfondie sur les divergences dans nos résultats constitue notre prochaine étape, ce qui n’a pas été possible pendant la durée limitée de cette mémoire. De plus, les cibles non ciblées de ces composés seront étudiées à l’aide du séquençage Bru Chase. Dans l’ensemble, cette étude explore de nouvelles stratégies pour restaurer l’expression de G3BP1, offrant ainsi une voie potentielle d’intervention thérapeutique dans la SLA. / Neurodegenerative disorders, such as Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD), have been associated with RNA-binding proteins (RBPs). Major hallmark of ALS is aggregation of an RNA-binding protein called TAR binding protein (TDP-43). TDP-43 has shown to bind to G3BP1, a nucleating factor for stress granule assembly, to stabilize it. Stress granules (SGs) are phase separated structures that form under stressful conditions and promote cell survival. Impaired stress granules assembly and reduced G3BP1 is reported in ALS. This reduction is due to a defect in TDP-43 stabilizing G3BP1 encoding transcripts; thus, a failed stress granule response could have a major role in the disease. Thus, this research focuses on restoring G3BP1, whose depletion is linked to TDP-43 loss of function. By utilizing small-molecule compounds identified through a drug screening campaign, we seek to increase G3BP1 expression, consequently reinstating the endogenous SG mechanism and promoting neuronal survival. The discovery of lead candidates (NPX-047, NPX-000-115, and NPX-001-280) that effectively rescue G3BP1 expression and function offers promise for potential ALS therapies. These compounds were tested on SH-SY5Y cells treated with si-TDP however no rescue of G3BP1 mRNA was observed despite higher levels of luciferase signals. Thus, in-depth investigation of discrepancies in our results is our next step which was not possible during the limited timeline of this thesis. In addition, off-targets of these compounds will be investigated using BruChase-sequencing. Overall, this study explores novel strategies to restore G3BP1 expression, providing a potential avenue for therapeutic intervention in ALS.

As the most common motor neuron disease, Amyotrophic lateral sclerosis (ALS) affects around 4 in every 100,000 people worldwide with reports of increasing prevalence over the years. Characterized by progressive degeneration of motor neurons, ALS patients suffer impairments of movement and typically die from respiratory failure 2-5 years after diagnosis. Curiously, ALS exists on a disease continuum with Frontotemporal Dementia (FTD) where 30-50% of patients will be diagnosed with both diseases. In FTD, degeneration of cortical neurons results in diverse behavioural changes including deficits in executive and social skills as well as language and memory. A central connection between ALS and FTD is TDP-43 (encoded by TARDBP), an essential DNA/RNA binding protein known to serve critical functions in numerous cellular processes. Despite mutations in TARDBP constituting a small percentage of familial cases, TDP 43 nuclear-to-cytoplasmic mislocalization is a pathological hallmark of most ALS-FTD cases. Therefore, therapeutic targets to rectify pathology and disease may be uncovered by identifying factors that regulate TDP-43. While it is currently established TDP-43 is ubiquitinated and phosphorylated in diseased states, our lab recently found TDP-43 is SUMOylated in response to stress. Of note, perturbations in the stress response are becoming increasingly implicated in neurodegenerations. Furthermore, TDP-43 plays critical roles in the stress response which become perturbed in ALS/FTD. We developed a TDP-43 "SUMO dead" mouse allele to gain an understanding of how disrupting this may contribute to the pathogenesis of ALS-FTD. Longitudinal characterization of the model explored behavioural and histological in vivo consequences following loss of TDP-43 SUMOylation. However, the phenotypes observed in the mutant mice were less robust in comparison to established ALS/FTD mouse models. Mutant mice did not have consistent differences in tests for similar outcomes, trials of the same test, or across age. Female mutant mice presented with early hyperactivity and disinhibition along with altered social grooming behaviour. At later age, these female mice developed impairments in spatial working memory. Male mice developed apathetic behaviour and motor deficits at the middle age timepoint. Histologically, various forms of pathological TDP-43 were observed in the absence of neurodegeneration. These data reveal that TDP-43 SUMOylation may play an important role in ALS/FTD pathogenesis.

Les gènes TDP-43 (TAR DNA Binding Protein 43) et FUS/TLS (Fused in Sarcoma/Translocated in Liposarcoma) sont actuellement à l’étude quant à leurs rôles biologiques dans le développement de diverses neuropathies telles que la Sclérose Latérale Amyotrophique (SLA). Étant donné que TDP-43 et FUS sont conservés au cours de l’évolution, nous avons utilisé l’organisme modèle C. elegans afin d’étudier leurs fonctions biologiques. Dans ce mémoire, nous démontrons que TDP-1 fonctionne dans la voie de signalisation Insuline/IGF pour réguler la longévité et la réponse au stress oxydatif. Nous avons développé des lignées C. elegans transgéniques mutantes TDP-43 et FUS qui présentent certains aspects de la SLA tels que la dégénérescence des motoneurones et la paralysie adulte. La protéotoxicité causée par ces mutations de TDP- 43 et FUS associées à la SLA, induit l’expression de TDP-1. À l’inverse, la délétion de tdp-1 endogène protège contre la protéotoxicité des mutants TDP-43 et FUS chez C. elegans. Ces résultats suggèrent qu’une induction chronique de TDP-1/TDP-43 sauvage propagerait la protéotoxicité liée à la protéine mutante. Nous avons aussi entrepris un criblage moléculaire pilote afin d’isoler des suppresseurs de toxicité neuronale des modèles transgéniques mutants TDP-43 et FUS. Nous avons ainsi identifié le bleu de méthylène et le salubrinal comme suppresseurs potentiels de toxicité liée à TDP-43 et FUS via réduction de la réponse au stress du réticulum endoplasmique (RE). Nos résultats indiquent que l’homéostasie de repliement des protéines dans le RE représente une cible pour le développement de thérapies pour les maladies neurodégénératives. / Two recently discovered causative genes for ALS, TDP-43 (TAR DNA Binding Protein 43) and FUS/TLS (Fused in Sarcoma/Translocated in Liposarcoma) are under further investigation regarding their biological roles in neuropathies such as Amyotrophic Lateral Sclerosis (ALS). Since TDP-43 and FUS are evolutionarily conserved we turned to the model organism C. elegans to learn more about their biological functions. Here we report that TDP-1 functions in the Insulin/IGF pathway to regulate longevity and the oxidative stress response. We have generated mutant TDP-43 and FUS transgenic lines in C. elegans that recapitulate certain aspects of ALS including motor neuron degeneration and adult-onset paralysis. Proteotoxicity caused by ALS- associated mutations in TDP-43 or FUS also induce TDP-1 expression and consistently, deletion of endogenous tdp-1 rescues mutant TDP-43 and FUS proteotoxicity in C. elegans. These results suggest that chronic induction of wild type TDP-1/TDP-43 by proteotoxicity may actively promote neurodegeneration. We also screened for small- molecule suppressors of mutant TDP-43 and FUS neuronal toxicity in transgenic C. elegans and identified methylene blue and salubrinal as potent suppressors of TDP-43 and FUS toxicity in our models through induction of the endoplasmic reticulum (ER) stress response. Our results indicate that protein folding homeostasis in the ER may be an important target for therapeutic development in neurodegenerative diseases.

Introdução: A demência frontotemporal (DFT) inclui a variante comportamental da demência frontotemporal (vcDFT), a variante semântica da afasia progressiva primária (vsAPP), e a variante não fluente da APP (vnfAPP). Os genes em que são encontradas mutações causadoras de DFT mais frequentemente são: GRN (que codifica a progranulina), MAPT (que codifica a proteína tau) e C9orf72. Métodos: Foram incluídos probandos diagnosticados com vcDFT, vsAPP ou vnfAPP, com base com os critérios diagnósticos mais recentes, e um grupo de indivíduos cognitivamente normais. Os éxons 2-12 de GRN e os éxons 1, 9-13 de MAPT foram sequenciados pelo método de Sanger, e foi realizada dosagem de progranulina no plasma. Resultados: foram incluídos 62 probandos, sendo 44 com vcDFT, 9 com vsAPP, e 9 com vnfAPP. Antecedente familiar de demência foi positivo em 45,1% dos probandos, e de DFT, em 24,1%. Os 60 indivíduos do grupo controle tinham idade média de 60,8±8,5 anos. Foram identificadas seis mutações nulas em GRN (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) e uma mutação patogênica em MAPT (p.N279K). A dosagem média de progranulina plasmática nos pacientes com mutações de GRN foi de 29,8±11,9ng/ml Conclusões: A frequência de mutações patogênicas em GRN nesta casuística foi de 9,6%, e a de mutações em MAPT foi de 1,6%. Entre casos familiais de DFT, a frequência de mutações em GRN foi de 33,3%, e em MAPT foi de 6,7%. Duas das mutações encontradas em GRN (p.Q130X e p.D317Afs*11) ainda não foram descritas em casos de DFT. O valor de corte de 70ng/ml identificou as mutações nulas de GRN com sensibilidade e especificidade de 100% / Introduction: Frontotemporal dementia (FTD) encompasses behavioral variant of frontotemporal dementia (bvFTD), semantic variant of primary progressive aphasia (svPPA), and nonfluent variant PPA (nfvPPA). The genes in which FTD-causing mutations are most frequently found are: GRN (which encodes progranulin), MAPT (which encodes tau protein) and C9orf72. Methods: We included probands diagnosed with bvFTD, svPPA or nfvPPA, based on the most recent diagnostic criteria, and a group of cognitively normal individuals. GRN exons 2-12 and MAPT exons 1, 9-13 were sequenced by the Sanger method, and plasma progranulin levels were measured. Results: we included 62 probands (44 with bvFTD, 9 with svPPA, and 9 with nfvPPA). Family history of dementia was positive in 45.1% of probands, and of DFT, in 24.1%. The control group of 60 individuals had a mean age of 60.8±8.5 years. Six null GRN mutations were identified in (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) and one MAPT pathogenic mutation (p.N279K). The mean plasma progranulin level in patients with GRN mutations was 29.8±11,9ng/ml. Conclusions: The frequency of pathogenic mutations in GRN was 9.6%, and of MAPT mutations was 1.6%. Among cases of familial FTD, the frequency of GRN mutations was 33.3%, and of MAPT mutations was 6.7%. Two of the mutations found in GRN (p.Q130X and p.D317Afs*11) are novel. The cutoff value of 70ng/ml identified null GRN mutations with sensitivity and specificity of 100%

Atualmente, as demências tornam-se mais prevalentes e constituem-se como um importante problema de saúde pública mundial. A Degeneração Lobar Frontotemporal (DLFT) e a Doença de Alzheimer (DA) são as de maior incidência. A investigação dos fatores de risco para as demências degenerativas inscreve-se entre os temas mais relevantes das neurociências e a avaliação dos fatores de risco de natureza genética tem produzido contribuições importantes. Na DLFT, mutações no gene TARDBP, codificador da proteína nuclear TDP-43, estão entre as ocorrências genéticas mais descritas, enquanto que para a DA, o alelo 4 do gene da apolipoproteína E (APOE) é o principal fator de risco. Pacientes com diagnóstico clínico de DLFT (n=47) e de DA provável (n=30) recebidos do ambulatório do Grupo de Neurologia Cognitiva e do Comportamento (GNCC) da Clínica Neurológica do HC-FMUSP foram convidados a participar do estudo. Amostras de sangue foram coletadas para a realização da extração de DNA linfocitário. Os éxons de 1-6 do gene TARDBP foram amplificados por PCR e seus produtos foram sequenciados em sequenciador automático. Os polimorfismos do gene APOE foram determinados através da técnica de PCR em tempo real. A análise do gene da TDP-43 em pacientes com DLFT mostrou a presença de uma mutação na região do éxon 6 do TARDBP (g.14935A>G) em um paciente do sexo masculino, com idade de 54 anos e diagnóstico de demência semântica. Na genotipagem dos pacientes de DA, foi observado que a metodologia utilizada, através de PCR em tempo real mostrou-se eficiente em detectar os polimorfismos do gene APOE, fornecendo resultados compatíveis quando comparados aos demais estudos brasileiros publicados anteriormente / Brazil is one of the developing countries that are undergoing a process of demographic transition in which the elderly represents a significant proportion of the total population. Neurodegenerative illnesses most commonly appear at such ages. Frontotemporal lobar degeneration (FTLD) and Alzheimers disease (AD) are the most frequent causes for dementia. The investigation of risk factors for degenerative dementia is a relevant subject of neurosciences and the evaluation of the nature of genetic risk factors has produced the most important contributions. Mutations in TARDBP gene, the encoder of the TDP-43 nuclear protein, appear as the most frequent genetic occurrences for FTLD, whereas, in DA, the 4 allele of the apolipoprotein E (APOE) is the major genetic risk factor. Patients with clinical diagnosis of FTLD types of families and sporadic (n=47) and probable AD (n=30) from the ambulatory of Cognitive Neurology Group and Behavior (CNGB) of Neurological Clinic of HC-FMUSP were invited to participate in this study. Blood samples were collected for lymphocytic DNA extraction. The APOE gene polymorphisms are being determined through the real time PCR technique. The 1-6 exons of TARDBP gene were amplified by PCR and their products were sequenced in automated sequencer. The TDP-43 gene analysis in patients with FTLD showed the presence of one mutation in the region of exon 6 TARDBP gene in a male patient of 54 years old, with diagnoses of semantic dementia. Regarding DA patients genotyping, the real time methodology has been shown as an efficient approach to detect APOE polymorphisms, presenting data similar to those observed in other Brazilian studies

No description available.

Les gènes TDP-43 (TAR DNA Binding Protein 43) et FUS/TLS (Fused in Sarcoma/Translocated in Liposarcoma) sont actuellement à l’étude quant à leurs rôles biologiques dans le développement de diverses neuropathies telles que la Sclérose Latérale Amyotrophique (SLA). Étant donné que TDP-43 et FUS sont conservés au cours de l’évolution, nous avons utilisé l’organisme modèle C. elegans afin d’étudier leurs fonctions biologiques. Dans ce mémoire, nous démontrons que TDP-1 fonctionne dans la voie de signalisation Insuline/IGF pour réguler la longévité et la réponse au stress oxydatif. Nous avons développé des lignées C. elegans transgéniques mutantes TDP-43 et FUS qui présentent certains aspects de la SLA tels que la dégénérescence des motoneurones et la paralysie adulte. La protéotoxicité causée par ces mutations de TDP- 43 et FUS associées à la SLA, induit l’expression de TDP-1. À l’inverse, la délétion de tdp-1 endogène protège contre la protéotoxicité des mutants TDP-43 et FUS chez C. elegans. Ces résultats suggèrent qu’une induction chronique de TDP-1/TDP-43 sauvage propagerait la protéotoxicité liée à la protéine mutante. Nous avons aussi entrepris un criblage moléculaire pilote afin d’isoler des suppresseurs de toxicité neuronale des modèles transgéniques mutants TDP-43 et FUS. Nous avons ainsi identifié le bleu de méthylène et le salubrinal comme suppresseurs potentiels de toxicité liée à TDP-43 et FUS via réduction de la réponse au stress du réticulum endoplasmique (RE). Nos résultats indiquent que l’homéostasie de repliement des protéines dans le RE représente une cible pour le développement de thérapies pour les maladies neurodégénératives. / Two recently discovered causative genes for ALS, TDP-43 (TAR DNA Binding Protein 43) and FUS/TLS (Fused in Sarcoma/Translocated in Liposarcoma) are under further investigation regarding their biological roles in neuropathies such as Amyotrophic Lateral Sclerosis (ALS). Since TDP-43 and FUS are evolutionarily conserved we turned to the model organism C. elegans to learn more about their biological functions. Here we report that TDP-1 functions in the Insulin/IGF pathway to regulate longevity and the oxidative stress response. We have generated mutant TDP-43 and FUS transgenic lines in C. elegans that recapitulate certain aspects of ALS including motor neuron degeneration and adult-onset paralysis. Proteotoxicity caused by ALS- associated mutations in TDP-43 or FUS also induce TDP-1 expression and consistently, deletion of endogenous tdp-1 rescues mutant TDP-43 and FUS proteotoxicity in C. elegans. These results suggest that chronic induction of wild type TDP-1/TDP-43 by proteotoxicity may actively promote neurodegeneration. We also screened for small- molecule suppressors of mutant TDP-43 and FUS neuronal toxicity in transgenic C. elegans and identified methylene blue and salubrinal as potent suppressors of TDP-43 and FUS toxicity in our models through induction of the endoplasmic reticulum (ER) stress response. Our results indicate that protein folding homeostasis in the ER may be an important target for therapeutic development in neurodegenerative diseases.

Atualmente, as demências tornam-se mais prevalentes e constituem-se como um importante problema de saúde pública mundial. A Degeneração Lobar Frontotemporal (DLFT) e a Doença de Alzheimer (DA) são as de maior incidência. A investigação dos fatores de risco para as demências degenerativas inscreve-se entre os temas mais relevantes das neurociências e a avaliação dos fatores de risco de natureza genética tem produzido contribuições importantes. Na DLFT, mutações no gene TARDBP, codificador da proteína nuclear TDP-43, estão entre as ocorrências genéticas mais descritas, enquanto que para a DA, o alelo 4 do gene da apolipoproteína E (APOE) é o principal fator de risco. Pacientes com diagnóstico clínico de DLFT (n=47) e de DA provável (n=30) recebidos do ambulatório do Grupo de Neurologia Cognitiva e do Comportamento (GNCC) da Clínica Neurológica do HC-FMUSP foram convidados a participar do estudo. Amostras de sangue foram coletadas para a realização da extração de DNA linfocitário. Os éxons de 1-6 do gene TARDBP foram amplificados por PCR e seus produtos foram sequenciados em sequenciador automático. Os polimorfismos do gene APOE foram determinados através da técnica de PCR em tempo real. A análise do gene da TDP-43 em pacientes com DLFT mostrou a presença de uma mutação na região do éxon 6 do TARDBP (g.14935A>G) em um paciente do sexo masculino, com idade de 54 anos e diagnóstico de demência semântica. Na genotipagem dos pacientes de DA, foi observado que a metodologia utilizada, através de PCR em tempo real mostrou-se eficiente em detectar os polimorfismos do gene APOE, fornecendo resultados compatíveis quando comparados aos demais estudos brasileiros publicados anteriormente / Brazil is one of the developing countries that are undergoing a process of demographic transition in which the elderly represents a significant proportion of the total population. Neurodegenerative illnesses most commonly appear at such ages. Frontotemporal lobar degeneration (FTLD) and Alzheimers disease (AD) are the most frequent causes for dementia. The investigation of risk factors for degenerative dementia is a relevant subject of neurosciences and the evaluation of the nature of genetic risk factors has produced the most important contributions. Mutations in TARDBP gene, the encoder of the TDP-43 nuclear protein, appear as the most frequent genetic occurrences for FTLD, whereas, in DA, the 4 allele of the apolipoprotein E (APOE) is the major genetic risk factor. Patients with clinical diagnosis of FTLD types of families and sporadic (n=47) and probable AD (n=30) from the ambulatory of Cognitive Neurology Group and Behavior (CNGB) of Neurological Clinic of HC-FMUSP were invited to participate in this study. Blood samples were collected for lymphocytic DNA extraction. The APOE gene polymorphisms are being determined through the real time PCR technique. The 1-6 exons of TARDBP gene were amplified by PCR and their products were sequenced in automated sequencer. The TDP-43 gene analysis in patients with FTLD showed the presence of one mutation in the region of exon 6 TARDBP gene in a male patient of 54 years old, with diagnoses of semantic dementia. Regarding DA patients genotyping, the real time methodology has been shown as an efficient approach to detect APOE polymorphisms, presenting data similar to those observed in other Brazilian studies

Introdução: A demência frontotemporal (DFT) inclui a variante comportamental da demência frontotemporal (vcDFT), a variante semântica da afasia progressiva primária (vsAPP), e a variante não fluente da APP (vnfAPP). Os genes em que são encontradas mutações causadoras de DFT mais frequentemente são: GRN (que codifica a progranulina), MAPT (que codifica a proteína tau) e C9orf72. Métodos: Foram incluídos probandos diagnosticados com vcDFT, vsAPP ou vnfAPP, com base com os critérios diagnósticos mais recentes, e um grupo de indivíduos cognitivamente normais. Os éxons 2-12 de GRN e os éxons 1, 9-13 de MAPT foram sequenciados pelo método de Sanger, e foi realizada dosagem de progranulina no plasma. Resultados: foram incluídos 62 probandos, sendo 44 com vcDFT, 9 com vsAPP, e 9 com vnfAPP. Antecedente familiar de demência foi positivo em 45,1% dos probandos, e de DFT, em 24,1%. Os 60 indivíduos do grupo controle tinham idade média de 60,8±8,5 anos. Foram identificadas seis mutações nulas em GRN (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) e uma mutação patogênica em MAPT (p.N279K). A dosagem média de progranulina plasmática nos pacientes com mutações de GRN foi de 29,8±11,9ng/ml Conclusões: A frequência de mutações patogênicas em GRN nesta casuística foi de 9,6%, e a de mutações em MAPT foi de 1,6%. Entre casos familiais de DFT, a frequência de mutações em GRN foi de 33,3%, e em MAPT foi de 6,7%. Duas das mutações encontradas em GRN (p.Q130X e p.D317Afs*11) ainda não foram descritas em casos de DFT. O valor de corte de 70ng/ml identificou as mutações nulas de GRN com sensibilidade e especificidade de 100% / Introduction: Frontotemporal dementia (FTD) encompasses behavioral variant of frontotemporal dementia (bvFTD), semantic variant of primary progressive aphasia (svPPA), and nonfluent variant PPA (nfvPPA). The genes in which FTD-causing mutations are most frequently found are: GRN (which encodes progranulin), MAPT (which encodes tau protein) and C9orf72. Methods: We included probands diagnosed with bvFTD, svPPA or nfvPPA, based on the most recent diagnostic criteria, and a group of cognitively normal individuals. GRN exons 2-12 and MAPT exons 1, 9-13 were sequenced by the Sanger method, and plasma progranulin levels were measured. Results: we included 62 probands (44 with bvFTD, 9 with svPPA, and 9 with nfvPPA). Family history of dementia was positive in 45.1% of probands, and of DFT, in 24.1%. The control group of 60 individuals had a mean age of 60.8±8.5 years. Six null GRN mutations were identified in (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) and one MAPT pathogenic mutation (p.N279K). The mean plasma progranulin level in patients with GRN mutations was 29.8±11,9ng/ml. Conclusions: The frequency of pathogenic mutations in GRN was 9.6%, and of MAPT mutations was 1.6%. Among cases of familial FTD, the frequency of GRN mutations was 33.3%, and of MAPT mutations was 6.7%. Two of the mutations found in GRN (p.Q130X and p.D317Afs*11) are novel. The cutoff value of 70ng/ml identified null GRN mutations with sensitivity and specificity of 100%