Rastreio de estratégias terapêuticas num modelo de ratinho da doença de Machado-Joseph: foco na proteostase

Tese de Doutoramento em Ciências da SaúdeMachado-Joseph Disease (MJD) belongs to the group of nine Polyglutamine (PolyQ) diseases, which are characterized by the appearance of misfolded protein species, protein aggregates, neuronal dysfunction and ultimately cell death, of which is triggered by the presence of an expanded CAG repeat in the respective disease-causing genes. Along with the pathogenic motif, all these disease-associated proteins are widely expressed but the diseases only affect specific subsets of neurons. So far there is no effective treatment available for these disorders. Because the pathogenic mechanism(s) underlying MJD are poorly understood, which might be hampering the progression of effective therapeutical targets, this work focused on the search for new therapies based on hypotheses, that additionally allow the study of molecular mechanism(s) of disease. For this, we used the CMVMJD135 mouse model, which recapitulates the human disease both at the phenotypic and neuropathologic levels. We tested the efficacy of several compounds acting on different aspects of cellular function: (i) molecular chaperone load, (Hsp90 inhibitor - 17-dimethyl aminoethylamino-17-demethoxygeldanamycin hydrochloride - 17-DMAG); (ii) autophagy (lithium chloride and a combination of lithium chloride – LiCl - and temsirolimus - CCI-779); (iii) Endoplasmic reticulum (ER) stress response, (taroursodeoxycholic acid - TUDCA), also known to have multiple actions in the cells, and (iv) the energy status in the cell (creatine). Chronic treatment of CMVMJD mice with 17-DMAG resulted in a delay in progression of the motor coordination deficits and a reduction in neuropathology. While we observed limited induction of heat-shock proteins with treatment, we found evidence that 17-DMAG could be acting through autophagy, as levels of LC3-II and beclin-1 were induced in the brain of treated animals. This resulted in decreased levels of the mutant ataxin-3 (ATXN3) and reduced intranuclear aggregation of this protein. To further test autophagy induction as potential therapeutic approach for MJD, we tested LiCl alone and a combination of LiCl with CCI-779 (m-TOR independent and dependent inducers, respectively). In spite of activating autophagy, as suggested by the increased levels of Beclin-1, Atg7, and LC3- II, and a reduction in the p62 protein levels, lithium had no overall beneficial effects in MJD model concerning motor performance. Furthermore, the combined therapy using LiCl and CCI-779 proved to be deleterious to both WT and transgenic animals, failing to rescue their neurological symptoms in the first and exerting in neurotoxic effects in the latter. TUDCA is an orally bioavailable and BBB permeable bile acid with known neuroprotective action, through its anti-amyloidogenic and chemical chaperone activities and its ability to modulate apoptotic pathways. In addition, TUDCA is FDA-approved for chronic use in humans to treat liver disorders, but has also been shown to be beneficial in several models of different neurodegenerative diseases. In the CMVMJD135 model, TUDCA delayed the onset of disease and improved the motor phenotype, including balance, motor coordination and gait parameters, and ameliorated neurological reflexes, exploratory movement deficits and muscular strength problems. Although TUDCA treatment did not reduce the ATXN3 aggregate load in the brain, it normalized the RNA levels of TNF-α, Il1β and Il10 in the brainstem and reduced the astrogliosis in the substantia nigra and brainstem. These results demonstrated the therapeutic efficacy of TUDCA supplementation for MJD, most likely mediated by its anti-inflammatory properties, making this compound an attractive for the treatment of neurodegenerative diseases, including MJD.Lastly, we tested the efficacy of creatine, another naturally-occurring compound known to balance energy status in the cell. Creatine-supplemented diet led to an overall improvement in the motor phenotype of CMVMJD135 mice, namely improved motor coordination, limb strength and gait quality, and amelioration of some neurological parameters such as tremors and abnormal reflexes. Remarkably, chronic creatine treatment delayed the onset of several symptoms and, in some cases, completely abolished their appearance, supporting creatine supplementation as a useful strategy to slow the progression of MJD. In summary in this work we validated a new MJD mouse model for use in preclinical trials as a powerful tool to study simultaneously pathogenic mechanisms associated with the disease and to develop novel therapeutic strategies. Furthermore, we found that Hsp90 inhibitors, TUDCA and creatine are relevant therapeutic candidates for MJD, some of which could be advanced to clinical trials in MJD patients.A doença de Machado Joseph (DMJ) pertence ao grupo de nove doenças poliglutaminas em que o gene causador da doença possui uma expansão anómala do codão CAG. A presença desta expansão conduz ao aparecimento de espécies proteicas com conformação incorreta, agregados proteicos, disfunção neuronal e consequentemente, morte celular. Para além da expansão, todos os genes associados a este grupo de doenças possuem expressão ubíqua apesar de só afetarem subconjuntos específicos de neurónios. Atualmente, não existe tratamento eficaz para a DMJ. Uma das razões pelas quais há um atraso no desenvolvimento de alvos terapêuticos está relacionada com o conhecimento incompleto do(s) mecanismo(s) de patogénese associados à DMJ. Assim sendo, o objetivo deste estudo centrou-se na procura de novas terapias, usando uma abordagem baseada em hipóteses, que pode também permitir o estudo dos mecanismo(s) moleculares da doença. Para tal, foi usado o modelo de ratinho CMVMJD135 que recapitula a doença humana a vários níveis, nomeadamente fenotípico e neuropatológico. Testámos a eficácia de diversos compostos com alvos terapêuticos relacionados com diferentes funções celulares: (i) níveis de chaperones moleculares (inibidor de Hsp90 – 17-dimetil aminoetillamino 17- demetoxigeldanamicina - 17-DMAG); (ii) autofagia (cloreto de lítio e combinação de cloreto de lítico –LiCL e temsirolimus - CCI-779); (iii) resposta ao stress do retículo endoplasmático (ácido tauroursodesoxicólico – TUDCA), com múltiplas acções celulares, e (iv) estado energético celular (creatina). O tratamento crónico com 17-DMAG no ratinho CMVMJD135 resultou num atraso da progressão da descoordenação motora e redução da neuropatologia. Apesar de ter sido observada uma indução limitada das chaperonas moleculares, este tratamento poderá ter atuado a nível da autofagia na medida em que houve indução dos níveis de LC3-II e beclina-1 no cérebro de animais tratados. Esta indução resultou na diminuição dos níveis de ataxina-3 (ATXN3) e uma redução da agregação intranuclear desta proteína. Para testar mais aprofundadamente a indução da autofagia como potencial terapia para a DMJ, foi testado LiCl isoladamente e em combinação com CCI-779 (atuando de forma independente e dependente da sinalização mTOR, respectivamente). Apesar da ativação da autofagia, sugerida pelos níveis aumentados de beclina-1, Atg7, LC3-II e redução dos níveis proteicos de p62, o tratamento do modelo DMJ com lítio foi de uma forma geral ineficaz ao nível do desempenho motor. Além disso, a terapia combinada de LiCl e CCI-779 revelou-se prejudicial em ambos os ratinhos WT e transgénicos, falhando na recuperação de sintomas neurológicos e sendo neurotóxico. O TUDCA é um ácido biliar com administração oral e permeável à BBB com funções neuroprotectoras conhecidas, através da sua capacidade anti-amiloidogénica, actividade de chaperona química e de modulação de vias apoptóticas. Adicionalmente, o TUDCA é um composto aprovado pela FDA para administração crónica no tratamento de doenças hepáticas, sendo também benéfico em diversos modelos de doenças neurodegenerativas. No modelo CMVMJD135, o tratamento com TUDCA atrasou o início da doença e melhorou o fenótipo motor incluindo equilíbrio, coordenação motora, e parâmetros da marcha, reduziu os reflexos neurológicos anómalos, melhorou os défices no movimento exploratório e força muscular. Apesar de o tratamento com este composto não ter reduzido os níveis de agregação da proteína ATXN3, foi eficaz na redução dos níveis de expressão de TNF-α, Il1β e Il10, tendo também reduzido a astrogliose no tronco cerebral e substantia nigra. Estes resultados demonstram a eficácia terapêutica da suplementação com TUDCA na DMJ, muito provavelmente através das suas capacidades anti-inflamatórias, o que torna este composto atrativo no tratamento de doenças neurodegenerativas, incluindo a DMJ. Por fim foi testada a creatina, outro composto natural reconhecido pela eficácia em restabelecer o equilíbrio energético na célula. A dieta suplementada com creatina conduziu a uma melhoria geral no fenótipo motor do ratinho CMVMJD135; nomeadamente, melhorou a coordenação motora, força nos membros e qualidade da marcha. Também teve impacto positivo em parâmetros neurológicos como os tremores e reflexos anormais. Surpreendentemente, o tratamento crónico com creatina atrasou o início do aparecimento de diversos sintomas e até aboliu a presença de alguns, o que reinforça a suplementação com creatina como uma estratégica eficaz no atraso na progressão de DMJ. Em conclusão, este estudo validou o novo modelo DMJ de ratinho para ensaios pré-clínicos como uma ferramenta valiosa para estudar simultaneamente mecanismos patogénicos associado à doença e para desenvolver novas estratégias terapêuticas. Além disso foi demonstrado que inibidores da Hsp90, TUDCA e creatina são candidatos terapêuticos relevantes para a DMJ, alguns dos quais com possibilidade de avançarem para ensaios clínicos em doentes.Fundação para a Ciência e a Tecnologia (FCT) SFRH/BD/78388/201

Pharmacological therapies for Machado-Joseph disease

Machado-Joseph disease (MJD), also known as Spinocerebellar Ataxia type 3 (SCA3), is the most common autosomal dominant ataxia worldwide. MJD integrates a large group of disorders known as polyglutamine diseases (polyQ). To date, no effective treatment exists for MJD and other polyQ diseases. Nevertheless, researchers are making efforts to find treatment possibilities that modify the disease course or alleviate disease symptoms. Since neuroimaging studies in mutation carrying individuals suggest that in nervous system dysfunction begins many years before the onset of any detectable symptoms, the development of therapeutic interventions becomes of great importance, not only to slow progression of manifest disease but also to delay, or ideally prevent, its onset. Potential therapeutic targets for MJD and polyQ diseases can be divided into (i) those that are aimed at the polyQ proteins themselves, namely gene silencing, attempts to enhance mutant protein degradation or inhibition/prevention of aggregation; and (ii) those that intercept the toxic downstream effects of the polyQ proteins, such as mitochondrial dysfunction and oxidative stress, transcriptional abnormalities, UPS impairment, excitotoxicity, or activation of cell death. The existence of relevant animal models and the recent contributions towards the identification of putative molecular mechanisms underlying MJD are impacting on the development of new drugs. To date only a few preclinical trials were conducted, nevertheless some had very promising results and some candidate drugs are close to being tested in humans. Clinical trials for MJD are also very few to date and their results not very promising, mostly due to trial design constraints. Here, we provide an overview of the pharmacological therapeutic strategies for MJD studied in animal models and patients, and of their possible translation into the clinical practice.(undefined

Insights into pathology and neurodegeneration features in a transgenic mouse model of Machado-Joseph disease

Dissertação de mestrado em Genética MolecularMachado-Joseph disease (MJD), also known as Spinocerebellar Ataxia 3 (SCA3), is the most common autosomal dominant ataxia worldwide, and is caused by a CAG repeat expansion within the coding region of the ATXN3 gene. The clinical variability of the disease phenotype as well as the age of onset depend on the length of the expanded repeat. The anticipation phenomenon is most frequently associated with repeat expansions in paternal transmission. MJD patients with a repeat expansion above 44 CAGs in the ATXN3 gene present cytoplasmic and/or intranuclear ataxin-3 aggregates and neuronal cell loss in specific areas of the brain. However, some questions remains unanswered in this disease: why only some subpopulations of neurons are affected, although ataxin- 3 is everywhere; what underlies this selective neuronal vulnerability; are these neurons dysfunctional or dying? In an attempt to address these issues, we took advantage of studying a cDNA transgenic mouse model (CMVMJD) expressing the mutant human ataxin-3 under the regulation of the CMV promoter (pCMV), previously generated in our lab. This transgenic mouse model shows an important overlap with genetic and clinical features of MJD, namely genetic instability of the expanded CAG repeat and a motor impairment phenotype. In this work, we performed an extensive pathological analysis of MJD mouse brains, that revealed a significant atrophy in the thalamus and in the dentate neurons. Increased GFAP immunostaining with reactive astrocytes was observed in the vestibular nuclei and substantia nigra of transgenic mice. Regarding cell death, we have searched for evidence of different cell death types (apoptosis and necrosis) by TUNEL assay, caspase-3 analysis and Fluoro-Jade B staining. We did not find any differences between wild-type and MJD transgenic mice, suggesting that probably the affected neurons are not dying, at least by apoptosis or necrosis, instead, they might just be dysfunctional. We also analysed of the somatic mosaicism in neuronal and non-neuronal tissues through aging revealed a significant increase in the mosaicism index of specific brain regions such as the pons, substantia nigra, cerebellar cortex, hipocampus, striatum, deep cerebellar nuclei and hypothalamus with age. However, there was no correlation between the extent of the mosaicism and the pathological involvement of a given region. The results allow us to conclude that the pCMVMJD94 mouse is a good model to study the pathogenic mechanisms of MJD, mimicking an early stage of the disease.A doença de Machado-Joseph, também conhecida por Ataxia Espinocerebelosa tipo 3 (SCA3), é a ataxia autossómica dominante mais comum em todo o mundo, causada por uma repetição de CAGs na região codificante do gene ATXN3. A variabilidade no fenótipo da doença assim como a idade de surgimento dos sintomas depende no tamanho da repetição expandida. O fenómeno de antecipação está mais frequentemente associado a transmissões paternas. Pacientes com DMJ com expansões acima de 44 CAGs revelam agregados citoplasmáticos e /ou nucleares e perda neuronal em áreas do cérebro específicas. Algumas questões chave permanecem por esclarecer. Por exemplo, nesta doença apenas algumas subpopulações de neurónios são afectadas, embora a ataxina-3 seja expressa em todas as áreas. O que está por detrás desta vulnerabilidade neuronal selectiva? Estarão estes neurónios a morrer ou estarão disfuncionais? Numa tentativa de responder a estas perguntas, utilizámos um modelo em ratinho que expressa o cDNA da ataxina-3 humana mutada, sob a regulação do promotor CMV (pCMV), previamente gerado no nosso laboratório. Neste trabalho, fizemos uma extensa análise patológica de cérebros de ratinho DMJ que revelaram uma atrofia relevante no tálamo e núcleos denteados. Também se observou um aumento da proteína GFAP, revelando um aumento da reactividade dos astrócitos, nos núcleos vestibular e substantia nigra dos ratinhos transgénicos. Também fizemos um rastreio de diferentes tipos de morte celular (apoptose e necrose) por TUNEL, análise da activação da caspase-3 (imunohistoquímica e western-blot) e coloração com Fluoro-Jade B. Não encontrámos diferenças significativas entre ratinhos do tipo selvagem e transgénicos, sugerindo que provavelmente estes neurónios não estarão a morrer, pelo menos por apoptose ou necrose, estando possivelmente disfuncionais. Para além disso, a repetição de CAG expandida, variou em mais de 50% das transmissões nos ratinhos transgénicos, com expansões típica transmitidas em meioses paternas e contracções em maternas. A análise do mosaicismo somático em tecidos neuronais e periféricos, durante o envelhecimento, revelou um aumento no índex de mosaicismo em regiões específicas do cérebro e mostrou ser dependente da idade. Este ratinho transgénico apresenta características genéticas e clínicas importantes que se sobrepõem às da DMJ, nomeadamente instabilidade intergeracional da expansão de CAGs, características patológicas da doença (astrogliose e neurónios atrofiados, nas regiões relevantes) e um fenótipo de descoordenação motora. Estes resultados permitiram-nos concluir que o ratinho pCMVMJD94 é um bom modelo para estudar os mecanismos patogénicos da DMJ, mimetizando estadios precoces da doença

Combined therapy with m-TOR-dependent and -independent autophagy inducers causes neurotoxicity in a mouse model of Machado-Joseph disease

A major pathological hallmark in several neurodegenerative disorders, like polyglutamine disorders (polyQ), including Machado-Joseph disease (MJD), is the formation of protein aggregates. MJD is caused by a CAG repeat expansion in the ATXN3 gene, resulting in an abnormal protein, which is prone to misfolding and forms cytoplasmic and nuclear aggregates within neurons, ultimately inducing neurodegeneration. Treatment of proteinopathies with drugs that up-regulate autophagy has shown promising results in models of polyQ diseases. Temsirolimus (CCI-779) inhibits the mammalian target of rapamycin (m-TOR), while lithium chloride (LiCl) acts by inhibiting inositol monophosphatase, both being able to induce autophagy. We have previously shown that chronic treatment with LiCl (10.4 mg/kg) had limited effects in a transgenic MJD mouse model. Also, others have shown that CCI-779 had mild positive effects in a different mouse model of the disease. It has been suggested that the combination of mTOR-dependent and -independent autophagy inducers could be a more effective therapeutic approach. To further explore this avenue toward therapy, we treated CMVMJD135 transgenic mice with a conjugation of CCI-779 and LiCl, both at concentrations known to induce autophagy and not to be toxic. Surprisingly, this combined treatment proved to be deleterious to both wild-type (wt) and transgenic animals, failing to rescue their neurological symptoms and actually exerting neurotoxic effects. These results highlight the possible dangers of manipulating autophagy in the nervous system and suggest that a better understanding of the potential disruption in the autophagy pathway in MJD is required before successful long-term autophagy modulating therapies can be developed.Fundação para a Ciência e Tecnologia through the projects [FEDER/FCT, POCI/SAU-MMO/60412/2004], [PTDC/SAU-GMG/64076/2006]. This work was supported by Fundação para a Ciência e Tecnologi

Differential mtDNA damage patterns in a transgenic mouse model of Machado-Joseph disease (MJD/SCA3)

Mitochondrial dysfunction has been associated with late onset neurodegenerative disorders, among which is Machado-Joseph disease (MJD/SCA3). In a previous study, using a transgenic mouse model of MJD, we reported a decrease in mitochondrial DNA (mtDNA) copy number and an accumulation of the 3876-bp deletion with age and with phenotype development. We extended this study by analyzing the pattern of mtDNA depletion and the accumulation of the 3876-bp deletion in 12 older transgenic (TG) and 4 wild-type (wt) animals, and by investigating the accumulation of somatic mutations in the D-loop region in 76 mice (42 TG and 34 wt). mtDNA damage was studied in TG and wt mice at different ages and tissues (blood, pontine nuclei, and hippocampus). Results for older mice demonstrate an accumulation of the mtDNA 3867-bp deletion with age, which was more pronounced in TG animals. Furthermore, the tendency for mtDNA copy number decrease with age, in all analyzed tissues of TG and wt animals, was also confirmed. No point mutations were detected in the D-loop, neither in TG nor wt animals, in any of the tissues analyzed. Due to the absence of mtDNA somatic mutations, we can suggest that mtDNA point mutation accumulation cannot be used to monitor the development and progression of the phenotype in this mouse model and likely in any MJD mice model. The present results further confirm not only the association between mtDNA alterations (copy number and deletions) and age, but also between such alterations and the expression of the mutant ataxin-3 in TG mice.NK and AR are a Fundo Regional para a Ciencia postdoctoral fellow (M3.1.7/F/002/2008 and M3.1.7/F/031/2011). This work was partially supported by Generalitat de Catalunya (SGR 2009-566)

Patterns of mitochondrial DNA damage in blood and brain tissues of a transgenic mouse model of Machado-Joseph disease

BACKGROUND: Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar ataxia caused by a CAG tract expansions in the ATXN3 gene. Patterns of mitochondrial damage associated with pathological findings of brain tissues could provide molecular biomarkers of this disorder. OBJECTIVE: The potential of mitochondrial DNA (mtDNA) damage as a biomarker of MJD progression was investigated using a transgenic mouse model. METHODS: DNA was obtained from affected (pontine nuclei) and nonaffected tissues (hippocampus and blood) of transgenic animals of three distinct age groups: 8 weeks, before onset of the phenotype; 16 weeks, at onset, and 24 weeks, at well-established phenotype. Wild-type littermate mice, serving as controls, were analyzed for the same tissues and age groups. mtDNA damage was studied by fluorescence-based quantitative PCR in 84 transgenic and 93 wild-type samples. RESULTS: A clear pattern of decrease in mtDNA copy number with age and accumulation of 3,867-bp deletions at the initial stages (both being more pronounced in transgenic mice) was observed. Pontine nuclei, the affected tissue in transgenic mice, displayed 1.5 times less copies of mtDNA than nonaffected brain tissue hippocampus (odds ratio = 1.21). Pontine nuclei displayed the highest percentage of mtDNA deletions (6.05% more in transgenic mice). CONCLUSION: These results suggest that mtDNA damage is related to the initiation of the phenotype in transgenic mice; mtDNA 3,867-bp deletions may be a biomarker of the initial stages of the disease.This study was supported by the following grants: DRCT Postdoctoral fellowship to N.K. (M3.1.7/F/002/2008), FCT Postdoctoral fellowship to T.C. (SFRH/BPD/38659/2007) and C.B. (SFRH/BPD/63121/2009), FCT research grants to S.S. (PTDC/SAU-GMG/64076/2006) and A.S.F. (PIC/IC/83013/2007)

Intrathecal injection of the secretome from ALS motor neurons regulated for miR-124 expression prevents disease outcomes in SOD1-G93A mice

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with short life expectancy and no effective therapy. We previously identified upregulated miR-124 in NSC-34-motor neurons (MNs) expressing human SOD1-G93A (mSOD1) and established its implication in mSOD1 MN degeneration and glial cell activation. When anti-miR-124-treated mSOD1 MN (preconditioned) secretome was incubated in spinal cord organotypic cultures from symptomatic mSOD1 mice, the dysregulated homeostatic balance was circumvented. To decipher the therapeutic potential of such preconditioned secretome, we intrathecally injected it in mSOD1 mice at the early stage of the disease (12-week-old). Preconditioned secretome prevented motor impairment and was effective in counteracting muscle atrophy, glial reactivity/dysfunction, and the neurodegeneration of the symptomatic mSOD1 mice. Deficits in corticospinal function and gait abnormalities were precluded, and the loss of gastrocnemius muscle fiber area was avoided. At the molecular level, the preconditioned secretome enhanced NeuN mRNA/protein expression levels and the PSD-95/TREM2/IL-10/arginase 1/MBP/PLP genes, thus avoiding the neuronal/glial cell dysregulation that characterizes ALS mice. It also prevented upregulated GFAP/Cx43/S100B/vimentin and inflammatory-associated miRNAs, specifically miR-146a/miR-155/miR-21, which are displayed by symptomatic animals. Collectively, our study highlights the intrathecal administration of the secretome from anti-miR-124-treated mSOD1 MNs as a therapeutic strategy for halting/delaying disease progression in an ALS mouse model.This research was funded by Santa Casa da Misericórdia de Lisboa: ELA-2015-002 (to DB); Fundação para a Ciência e a Tecnologia (FCT): PTDC/MED-NEU/31395/2017 (to D.B.), UIDB/UIDP/04138/2020, and UID/DTP/04138/2019-2020 (to iMed.ULisboa); Programa Operacional Regional de Lisboa and the Programa Operacional Competitividade e Internacionalização LISBOA-01-0145-FEDER-031395 (to D.B.); La Caixa Foundation and Francisco Luzón Foundation through project HR21-00931 (to D.B.); and an individual fellowship from FCT: SFRH/BD/129586/2017 (to M.B.). This work was also funded by the ICVS Scientific Microscopy Platform, a member of the national infrastructure of PPBI—Portuguese Platform of Bioimaging (PPBI-POCI-01-0145-FEDER-022122)

Selective impact of Tau loss on nociceptive primary afferents and pain sensation

Tau protein hyperphosphorylation and consequent malfunction are hallmarks of Alzheimer's disease pathology; importantly, pain perception is diminished in these patients. In physiological conditions, Tau contributes to cytoskeletal dynamics and in this way, influences a number of cellular mechanisms including axonal trafficking, myelination and synaptic plasticity, processes that are also implicated in pain perception. However, there is no in vivo evidence clarifying the role of Tau in nociception. Thus, we tested Tau-null (Tau-/-) and Tau+/+ mice for acute thermal pain (Hargreaves' test), acute and tonic inflammatory pain (formalin test) and mechanical allodynia (Von Frey test). We report that Tau-/- animals presented a decreased response to acute noxious stimuli when compared to Tau+/+ while their pain-related behavior is augmented under tonic painful stimuli. This increased reactivity to tonic pain was accompanied by enhanced formalin-evoked c-fos staining of second order nociceptive neurons at Tau-null dorsal horn. In addition, we analyzed the primary afferents conveying nociceptive signals, estimating sciatic nerve fiber density, myelination and nerve conduction. Ultrastructural analysis revealed a decreased C-fiber density in the sciatic nerve of Tau-null mice and a hypomyelination of myelinated fibers (Ad-fibers) - also confirmed by western blot analysis - followed by altered conduction properties of Tau-null sciatic nerves. To our knowledge, this is the first in vivo study that demonstrates that Tau depletion negatively affects the main systems conveying nociceptive information to the CNS, adding to our knowledge about Tau function(s) that might also be relevant for understanding peripheral neurological deficits in different Tauopathies.We would like to thank Drs Joao Relvas, Joana Paes de Faria Monteiro and Nuno Dias for their comments in this work. Many thanks to Dr Joao Relvas for the MBP antibody. The work was supported by grants "SFRH/BPD/80118/2011", "PTDC/SAU-NMC/113934/2009" funded by FCT - Portuguese Foundation for Science and Technology and project DoIT - Desenvolvimento e Operacionalizacao da Investigacao de Translacao (No. do projeto 13853), funded by Fund Europeu de Desenvolvimento Regional (FEDER) through the Programa Operacional Fatores de Competitividade (POFC). Author's contributions: experimental design - IS, HA, VP, AA, and NS; performed research - IS, HA, VP, AL, SL, SS, SP, AC, FPR, and RF; data analyses - IS, HA, AL, VP, SC, and FPR; and manuscript preparation - IS, HA, VP, and NS

Microglial depletion has no impact on disease progression in a mouse model of machado–joseph disease

Machado–Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), is an autosomal dominant neurodegenerative disorder (ND). While most research in NDs has been following a neuron-centric point of view, microglia are now recognized as crucial in the brain. Previous work revealed alterations that point to an increased activation state of microglia in the brain of CMVMJD135 mice, a MJD mouse model that replicates the motor symptoms and neuropathology of the human condition. Here, we investigated the extent to which microglia are actively contributing to MJD pathogenesis and symptom progression. For this, we used PLX3397 to reduce the number of microglia in the brain of CMVMJD135 mice. In addition, a set of statistical and machine learning models were further implemented to analyze the impact of PLX3397 on the morphology of the surviving microglia. Then, a battery of behavioral tests was used to evaluate the impact of microglial depletion on the motor phenotype of CMVMJD135 mice. Although PLX3397 treatment substantially reduced microglia density in the affected brain regions, it did not affect the motor deficits seen in CMVMJD135 mice. In addition to reducing the number of microglia, the treatment with PLX3397 induced morphological changes suggestive of activation in the surviving microglia, the microglia of wild-type animals becoming similar to those of CMVMJD135 animals. These results suggest that microglial cells are not key contributors for MJD progression. Furthermore, the impact of PLX3397 on microglial activation should be taken into account in the interpretation of findings of ND modification seen upon treatment with this CSF1R inhibitor.Fundação para a Ciência e a Tecnologia (FCT) (PTDC/NEUNMC/3648/2014) and COMPETE-FEDER (POCI-01-0145-FEDER-016818). It was also supported by Portuguese funds through FCT in the framework of the Project POCI-01-0145-FEDER-031987 (PTDC/MED-OUT/31987/2017). A.B.C. was supported by a doctoral fellowship from FCT (PD/BD/127828/2016). B.C. was also supported by FCT (2020.03898.CEECIND). This work was funded by ICVS Scientific Microscopy Platform, member of the national infrastructure PPBI (Portuguese Platform of Bioimaging) (PPBIPOCI-01-0145-FEDER-022122), and by National funds, through FCT—project UIDB/50026/2020 and UIDP/50026/2020

Motor uncoordination and neuropathology in a transgenic mouse model of Machado-Joseph disease lacking intranuclear inclusions and ataxin-3 cleavage products

Machado-Joseph disease (MJD) is a late-onset neurodegenerative disorder caused by a polyglutamine (polyQ) expansion in the ataxin-3 protein. We generated two transgenic mouse lineages expressing the expanded human ataxin-3 under the control of the CMV promoter: CMVMJD83 and CMVMJD94, carrying Q83 and Q94 stretches, respectively. Behavioral analysis revealed that the CMVMJD94 transgenic mice developed motor uncoordination, intergenerational instability of the CAG repeat and a tissue-specific increase in the somatic mosaicism of the repeat with aging. Histopathological analysis of MJD mice at early and late stages of the disease revealed neuronal atrophy and astrogliosis in several brain regions; however, we found no signs of microglial activation or neuroinflammatory response prior to the appearance of an overt phenotype. In our model, the appearance of MJD-like symptoms was also not associated with the presence of ataxin-3 cleavage products or intranuclear aggregates. We propose the transgenic CMVMJD94 mice as a useful model to study the early stages in the pathogenesis of MJD and to explore the molecular mechanisms involved in CAG repeat instability.We would like to thank to Dr. Henry Paulson for providing the anti-ataxin-3 serum, Dr. Monica Sousa for the pCMV vector and to Eng. Lucilia Goreti Pinto for technical assistance. AS-F., M.C.C., S.S. and C.B. received FCT fellowships (SFRH/BD/15910/2005; SFRH/BPD/28560/2006; PTDC/SAU-GMG/64076/2006; SFRH/BPD/20987/2004). This research was funded by Fundacao para a Ciencia e Tecnologia through projects FEDER/FCT, POCI/SAU-MMO/60412/2004, PTDC/SAU-GMG/64076/2006; and Ataxia MJD Research Project