Machado-Joseph Disease Research Articles

RNA Interference Therapy for Machado–Joseph Disease: Long-Term Safety Profile of Lentiviral Vectors Encoding Short Hairpin RNAs Targeting Mutant Ataxin-3

Machado-Joseph disease (MJD) or spinocerebellar ataxia type 3 is a neurodegenerative disorder caused by an abnormal repetition of a CAG codon in the MJD1 gene. This expansion translates into a long polyglutamine tract, leading to the misfolding of the mutant protein ataxin-3, which abnormally accumulates in the nucleus, thus leading to neurodegeneration in specific brain regions. No treatment able to modify the progression of the disease is available. However, it has previously been shown that specific silencing of mutant ataxin-3 by RNA interference with viral vectors is a promising therapeutic strategy for MJD. Nevertheless, reports of cytotoxic effects of this technology led to the safety profile of the previously tested lentiviral vectors encoding short hairpin (sh)RNAs (LV-shmutatx3) targeting mutant ataxin-3 upon brain injection being investigated. For this purpose, the vectors were injected in the mouse striata, and neuronal dysfunction, degeneration, gliosis, off-target effects, and saturation of the RNA interference machinery were evaluated. It was found that: (1) LV-shmutatx3 mediated stable and long-term expression of the shRNA in neurons of the mouse striatum; (2) neuronal dysfunction evaluated by darpp-32, NeuN, and cresyl violet staining, initially more pronounced, became indistinguishable from the phosphate-buffered saline group at 8 weeks and resolved within 20 weeks; (3) astrocytic activation was present, which resolved within 8 weeks; (4) microglial activity and proinflammatory cytokines release were present, which resolved and normalized within 20 weeks; and (5) there were no off-target effects or saturation of the endogenous RNA interference processing machinery in the mouse striatum. The data show that injection of lentiviral vectors encoding a shRNA targeting mutant ataxin-3 in the mouse brain induce transient dysfunctions, which resolve within 20 weeks. Importantly, long-term expression (up to 20 weeks post injection) of this shRNA (driven by H1 promoter) led to no toxic effect in vivo. This study thus constitutes an additional step in a future translation of gene silencing as a therapy for MJD.

Ibuprofen enhances synaptic function and neural progenitors proliferation markers and improves neuropathology and motor coordination in Machado-Joseph disease models.

Machado-Joseph disease or spinocerebellar ataxia type 3 is an inherited neurodegenerative disease associated with an abnormal glutamine over-repetition within the ataxin-3 protein. This mutant ataxin-3 protein affects several cellular pathways, leading to neuroinflammation and neuronal death in specific brain regions resulting in severe clinical manifestations. Presently, there is no therapy able to modify the disease progression. Nevertheless, anti-inflammatory pharmacological intervention has been associated with positive outcomes in other neurodegenerative diseases. Thus, the present work aimed at investigating whether ibuprofen treatment would alleviate Machado-Joseph disease. We found that ibuprofen-treated mouse models presented a significant reduction in the neuroinflammation markers, namely Il1b and TNFa mRNA and IKB-α protein phosphorylation levels. Moreover, these mice exhibited neuronal preservation, cerebellar atrophy reduction, smaller mutant ataxin-3 inclusions and motor performance improvement. Additionally, neural cultures of Machado-Joseph disease patients' induced pluripotent stem cells-derived neural stem cells incubated with ibuprofen showed increased levels of neural progenitors proliferation and synaptic markers such as MSI1, NOTCH1 and SYP. These findings were further confirmed in ibuprofen-treated mice that display increased neural progenitor numbers (Ki67 positive) in the subventricular zone. Furthermore, interestingly, ibuprofen treatment enhanced neurite total length and synaptic function of human neurons. Therefore, our results indicate that ibuprofen reduces neuroinflammation and induces neuroprotection, alleviating Machado-Joseph disease-associated neuropathology and motor impairments. Thus, our findings demonstrate that ibuprofen treatment has the potential to be used as a neuroprotective therapeutic approach in Machado-Joseph disease.

Gillespiе syndrome, caused by previously undescribed mutation in the gene <i>ITPR1<i>

Gillespie syndrome is one of the rare monogenic syndromes characterized by a combination of congenital muscular hypotonia, delayed psychomotor and speech development, ataxia and hypoplasia of the iris. The cause of disease – homozygous, compound heterozygous and heterozygous mutations in the gene ITPR1.We described a case history of a child of 1 year and 8 months whose parents were complaining of severe delay in psychomotor and speech development, and a violation of the functions of the visual analyzer. Neurological and ophthalmologic examinations were performed according to a standard procedure. Search for mutations was carried out using high-performance exome sequencing on NextSeg 500 (Illumina, USA) with an average coverage of at least 70–100x.Clinical and genetic characteristics of the patient with Gillespie syndrome due to the newly identified heterozygous missense mutation are presented. Mutation 1865T˃S in the 18 exon of the ITPR1 gene was found during the new generation sequencing of the exome. In the future, these data can be used to predict the characteristics of clinical manifestations and the severity of Gillespie syndrome, when a similar nucleotide substitution will be found in other patients.

Twenty Years of a Pre-Symptomatic Testing Protocol for Late-Onset Neurological Diseases in Portugal.

The national protocol of genetic counselling and pre-symptomatic testing for late-onset neurological diseases began in Portugal in 1995. Initially, it was accessible only to adults at-risk for Machado-Joseph disease, but was later extended to other hereditary ataxias, to Huntington's disease and to familial amyloid polyneuropathy caused by Val30Met mutation at the transthyretin gene. The aim of this study was to describe the profile of the population seeking pre-symptomatic testing, while also reflecting on the experience of conducting the protocol of multidisciplinary sessions since 1996. We conducted a retrospective study and collected data from clinical records of consultands who requested pre-symptomatic testing at our centre in Porto (Portugal) during the first twenty years of practice (1996 - 2015). A total of 1446 records were reviewed. The most common reason for testing was to reduce uncertainty (41.7%). The rate of withdrawals before results disclosure was lower (16%) than reported in other international experiences with pre-symptomatic testing, while 45% of the consultands dropped out the protocol after learning the test results (73.5% of them were non-carriers). As far as the mutation carriers were concerned, 29.6% adhered to the protocol a year after test disclosure. Consultands that had learned about presymptomatic testing through healthcare professionals tended to adhere more to pre-symptomatic testing consultations. The profile of Portuguese consultands at risk for late-onset neurological diseases is similar to those reported in other international programs. The largest group in this data set was the one comprising the subjects at risk for familial amyloid polyneuropathy caused by Val30Met mutation at the transthyretin gene, and it is likely that therapeutic options for this condition may have influenced this result. Adherence to pre-symptomatic testing may change in the future since effective therapies are available (or given the fact that people think effective treatments are imminent). This study reflects the first comprehensive description of a Portuguese experience with pre-symptomatic testing for late onset neurological diseases. The development of innovative approaches to improve the consultands' experience with pre-symptomatic testing and their engagement in genetic departments is still a challenge in Portuguese genetics healthcare departments. A better coordination among primary care and genetics healthcare services is needed.

Non-coding repeats in the ATXN8OS gene are expanded in Japanese patients with amyotrophic lateral sclerosis (P3.7-005)

Non-coding repeats in the ATXN8OS gene are expanded in Japanese patients with amyotrophic lateral sclerosis (P3.7-005)

'Staying strong on the inside and outside' to keep walking and moving around: Perspectives from Aboriginal people with Machado Joseph Disease and their families from the Groote Eylandt Archipelago, Australia.

Machado Joseph Disease (MJD) (spinocerebellar ataxia 3) is a hereditary neurodegenerative disease causing progressive ataxia and loss of mobility. It is the most common spinocerebellar ataxia worldwide. Among Aboriginal families of Groote Eylandt and related communities across Australia’s Top End, MJD is estimated to be more prevalent than anywhere else in the world. This study explored lived experiences of individuals and families with MJD to determine what is important and what works best to keep walking and moving around. A collaborative qualitative exploratory study, drawing from constructivist grounded theory methods, was undertaken for data collection and analysis. Semi-structured in-depth interviews were conducted with individuals with MJD (n = 8) and their family members (n = 4) from the Groote Eylandt Archipelago where ~1500 Aboriginal people (Warnumamalya) live. Interviews were led by Warnumamalya community research partners in participants’ preferred language(s). Participants described their experience of living with MJD, from ‘knowing about MJD’, ‘protecting yourself from MJD’ and ‘adjusting to life with MJD’. While the specific importance of walking and moving around differed widely between participants, all perceived that walking and moving around enabled them to do what mattered most to them in life. ‘Staying strong on the inside and outside’ (physically, mentally, emotionally, spiritually) was perceived to work best to keep walking and moving around as long as possible. A framework that included personal and environmental strategies for staying strong emerged: ‘Exercising your body’, ‘having something important to do’, ‘keeping yourself happy’, ‘searching for good medicine’, ‘families helping each other’ and ‘going country’. This study, the first to explore lived experiences of MJD in Australia, highlights the importance of maintaining mobility as long as possible. Strategies perceived to work best address physical and psychosocial needs in an integrated manner. Services supporting families with MJD need flexibility to provide individualised, responsive and holistic care.

Is the High Frequency of Machado-Joseph Disease in China Due to New Mutational Origins?

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia 3 or SCA3) is the most common dominant ataxia worldwide, with an overall average prevalence of 1–5/100,000. To this date, two major ancestral lineages have been found throughout the world. In China, the relative frequency of MJD among the SCAs reaches as high as 63%, however, little is known about its mutational origin in this country. We analyzed 50 families with MJD patients in two or more generations to study the hypothesis that new mutational events have occurred in this population. Haplotypes based on 20 SNPs have shown new genetic backgrounds segregating with MJD mutations in our cohort from China. We found the “Joseph-derived” lineage (Joseph lineage with a G variant in rs56268847) to be very common among Chinese MJD patients. Moreover, we estimated the time for the origin of this MJD SNP background based on STR diversity flanking the (CAG)n of ATXN3. It was surprising to find that the Chinese MJD population originated from 8,000 to 17,000 years ago, far earlier than the previous literature reports, which will be an important evidence to explain the origin, spread and founder effects of MJD.

A Pipeline to Assess Disease-Associated Haplotypes in Repeat Expansion Disorders: The Example of MJD/SCA3 Locus.

At least 40 human diseases are associated with repeat expansions; yet, the mutational origin and instability mechanisms remain unknown for most of them. Previously, genetic epidemiology and predisposing backgrounds for the instability of some expanding loci have been studied in different populations through the analysis of diversity flanking the respective pathogenic repeats. Here, we aimed at developing a pipeline to assess disease-associated haplotypes at oligonucleotide repeat loci, combining analysis of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs). Machado-Joseph disease (MJD/SCA3), the most frequent dominant ataxia worldwide, was used as an example of a detailed procedure. Thus, to identify genetic backgrounds that segregate with expanded/mutated alleles in MJD, we selected a set of 26 SNPs and 7 STRs flanking the causative CAG repeat. Key criteria and steps for this selection are described, and included (1) haplotype blocks minimizing the occurrence of recombination (for SNPs); and (2) match scores to increase potential for polymorphic information content of repetitive sequences found in Tandem Repeats Finder (for STRs). To directly assess SNP haplotypes in phase with MJD expansions, we optimized a strategy with preferential amplification of normal over expanded alleles, in addition to SNP allele-specific amplifications; this allowed the identification of disease-associated SNP haplotypes, even when only the proband is available in a given family. To infer STR haplotypes, we optimized a multiplex PCR, including 7 STRs plus the MJD_CAG repeat, followed by analysis of segregation or the use of the PHASE software. This protocol is a ready-to-use tool to assess MJD haplotypes in different populations. The pipeline designed can be used to assess disease-associated haplotypes in other repeat-expansion diseases. This should be of great utility to study (1) genetic epidemiology (population-of-origin, age and spreading routes of mutations) and (2) mechanisms responsible for de novo expansions, in these neurological diseases; (3) to detect predisposing haplotypes and (4) phenotype modifiers; (5) to help solving cases of apparent homoallelism (two same-size normal alleles) in diagnosis; and (6) to identify the best targets for the development of allele-specific therapies in ethnically diverse patient populations.

Assessment of Bone Mineral Density of Patients with Spinocerebellar Ataxia Type 3.

ObjectiveMachado-Joseph disease (MJD) is a spinocerebellar ataxia, and osteoporosis is a multifactor disease that may affect patients with neurologic conditions. The frequency of osteoporosis among MJD patients, however, has not been studied. The purpose of this study is to evaluate bone mineral density (BMD) and identify correlations between clinical factors and frequency of vertebral fractures in patients with MJD.MethodsClinical data, lumbar X-rays and BMD data were obtained in 30 patients with MJD.ResultsTen patients (33.3%) showed low BMD in at least one of the sites studied based on Z-scores. The Z-score correlated directly with body mass index, and the femoral neck Z-score was inversely correlated with cytosine-adenine-guanine (CAG) expansion. There was no correlation between BMD and other clinical factors. Forty-three percent of the patients reported previous pathologic fractures. Five patients (16.7%) had at least one fracture detected by lumbar X-ray.ConclusionLow BMD and fractures are frequent among MJD patients, and careful management of BMD may be beneficial for these patients.

Facial grimacing and clinical correlates in spinocerebellar ataxia type 3

IntroductionSpinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common spinocerebellar ataxia (SCA) worldwide. SCA3 presents with cerebellar ataxia in association with pyramidal signs, peripheral amyotrophy, nystagmus, ophthalmoparesis, fasciculations of the face and tongue, dystonia and parkinsonism. Oromandibular dystonia (OMD) with facial grimacing (FG) in SCA3 has seldom been reported in the literature and in series of SCA3 patients. MethodsWe evaluated 104 patients with SCA (59 patients with SCA3, 20 with SCA2, 20 with SCA7 and 5 with SCA6) and assessed dystonia frequency and types. ResultsThirteen cases of SCA3, one of SCA2 and two of SCA7 had dystonia. OMD in the form of FG was present in seven SCA3 patients (11.9%). Patients with FG were significantly younger, had earlier disease onset and a significantly higher CAG repetition length when compared to the SCA3 sample. Parkinsonism, dysphagia and pyramidal signs were significantly more frequent in the FG group than the non-FG group of the SCA3 sample. ConclusionPatients with SCA3 presenting with FG are younger, with earlier disease onset and higher CAG repetition length. They present with parkinsonism, dysphagia and pyramidal signs more frequently than SCA3 patients without FG.

Physiological and pathophysiological characteristics of ataxin-3 isoforms

Ataxin-3 is a deubiquitinating enzyme and the affected protein in the neurodegenerative disorder Machado-Joseph disease (MJD). The ATXN3 gene is alternatively spliced, resulting in protein isoforms that differ in the number of ubiquitin-interacting motifs. Additionally, nonsynonymous SNPs in ATXN3 cause amino acid changes in ataxin-3, and one of these polymorphisms introduces a premature stop codon in one isoform. Here, we examined the effects of different ataxin-3 isoforms and of the premature stop codon on ataxin-3's physiological function and on main disease mechanisms. At the physiological level, we show that alternative splicing and the premature stop codon alter ataxin-3 stability and that ataxin-3 isoforms differ in their enzymatic deubiquitination activity, subcellular distribution, and interaction with other proteins. At the pathological level, we found that the expansion of the polyglutamine repeat leads to a stabilization of ataxin-3 and that ataxin-3 isoforms differ in their aggregation properties. Interestingly, we observed a functional interaction between normal and polyglutamine-expanded ATXN3 allelic variants. We found that interactions between different ATXN3 allelic variants modify the physiological and pathophysiological properties of ataxin-3. Our findings indicate that alternative splicing and interactions between different ataxin-3 isoforms affect not only major aspects of ataxin-3 function but also MJD pathogenesis. Our results stress the importance of considering isoforms of disease-causing proteins and their interplay with the normal allelic variant as disease modifiers in MJD and autosomal-dominantly inherited diseases in general.

State biomarkers for Machado Joseph disease: Validation, feasibility and responsiveness to change.

Machado-Joseph disease (SCA3/MJD) is the most common spinocerebellar ataxia worldwide, and particularly so in Southern Brazil. Due to an expanded polyglutamine at ataxin-3, SCA3/MJD presents a relentless course with no current disease modifying treatment. Clinical scales used to measure SCA3/MJD progression present moderate effect sizes, a major drawback for their use as main outcomes in clinical trials, given the rarity and slow progression of the disease. This limitation might be overcome by finding good surrogate markers. We present here a review of studies on peripheral and neurophysiological markers in SCA3/MJD that can be candidates for state biomarkers. Data on markers already studied were summarized, giving emphasis on validation against clinical scale, and responsiveness to change. While some biological fluid compounds and neurophysiological parameters showed poor responsiveness, others seemed to be good candidates. Some potential candidates that are waiting for responsiveness studies were serum levels of neuron specific enolase, vestibulo-ocular reflex and video-oculography. Candidates evaluated by RNA and microRNA expression levels need further studies to improve their measurements. Data on peripheral levels of Beclin-1 and DNAJB1 are promising but still incipient. We conclude that several potential candidates should follow onto validating studies for surrogate state biomarkers of SCA3/MJD.

Pre-Clinical Assessment of Mesenchymal Stem Cell-Based Therapies in Spinocerebellar Ataxia Type 3

Motor uncoordination is one of the symptoms of spinocerebellar ataxia type 3/ Machado-Joseph disease (MJD), for which there is no effective treatment. In recent years, stem-cell related therapies begun to be explored for the treatment of neurodegenerative diseases. Beyond their potential for cell replacement therapies, stem cells also act as immunomodulators and neuroprotectors. Despite the evidence of beneficial outcomes in this context, the short duration of the pre and clinical trials and the fact that most patients regressed to the disease stage prior to treatment, highlights the urgency to assess therapeutic efficacy in a chronic fashion. The purpose of this study was to compare the therapeutic efficacy of hMSC transplantation versus administration of their secretome in different disease-relevant regions of the CNS, using a mouse model of MJD. We observed a more marked and sustained therapeutic benefit with hMSC transplantation into the cerebellum when compared to substantia nigra/ striatum or the spinal cord, or to administration of MSC secretome. Funding Statement: This work has been funded the National Ataxia Foundation (NAF), by FEDER, through the Competitiveness Factors Operational Programme (COMPETE), project NORTE-01-0145-FEDER-000013, supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, and by National funds through the Foundation for Science and Technology (FCT) under the scope of the project UID/Multi/50026/2019 and fellowships to A.N-C., B. M-P., J. S. C., F. G. T., N. S., R. L., and S. D-S. (SFRH/BPD/118779/2016, SFRH/BD/120124/2016, SFRH/BD/140624/2018, SFRH/BPD/118408/2016, CEECIND/04794/2017, PD/BDE/127836/2016 and PTDC/NEUNMC/3648/2014). Declaration of Interests: The authors have no conflict of interests to report. Ethics Approval Statement: All procedures were conducted in accordance with European regulations (European Union Directive 86/609/EEC). Animal facilities and the people directly involved in animal experiments (A.N.C, B.M.P, J.S.C., S.D.S, S.M., F.G.T, F.L., R.L., N.A.S) as well as the principal investigators (A.J.S. and P.M.) were certified by the Portuguese regulatory entity Direcao Geral de Alimentacao e Veterinaria. All the protocols performed were approved by the Animal Ethics Committee of the Life and Health Sciences Research Institute, University of Minho (Braga, Portugal) and by the national regulatory agency, Direcao Geral de Alimentacao e Veterinaria (DGAV 020317).

Blood-brain barrier dysfunction as a neuropathological feature in Machado-Joseph Disease: results from human and mouse samples

Blood-brain barrier dysfunction as a neuropathological feature in Machado-Joseph Disease: results from human and mouse samples

Autophagy activation induced by let-7 microRNA overexpression counteracts disease phenotype in Machado-Joseph disease mouse models

Autophagy activation induced by let-7 microRNA overexpression counteracts disease phenotype in Machado-Joseph disease mouse models

Population medical genetics: translating science to the community.

Rare genetic disorders are currently in the spotlight due to the elevated number of different conditions and significant total number of affected patients. The study of these disorders is extremely helpful for the elucidation of physiological processes related with complex disorders. Isolated populations are instrumental for the study of genetic disorders, considering their homogeneity and high proportion of affected patients in a small geographic area. These favorable conditions lead to the creation of a new discipline, known as “population medical genetics”, which integrates medical genetics, population genetics, epidemiological genetics and community genetics. In order to develop practical activities in this new discipline, the National Institute of Population Medical Genetics (INaGeMP) was created in 2008 in Brazil. INaGeMP has developed several tools and funded numerous research activities. In this review, we highlight three successful projects developed in the first 10 years of INaGeMP activities (2008-2018): a newborn screening pilot study for MPS VI in Northeast Brazil, the study of Machado-Joseph disease in Brazilian families with Azorian ancestry, and the high twinning rate in a small town in southern Brazil. The results of these projects in terms of scientific output and contributions to the affected communities highlight the success and importance of INaGeMP.

Choosing not to know: accounts of non-engagement with pre-symptomatic testing for Machado-Joseph disease.

This paper reports accounts from people at-risk for, or affected by, Machado-Joseph disease, and their family members, about their decisions not to seek pre-symptomatic testing, therefore remaining (for the time) uninformed about their genetic status. We draw on individual and family semi-structured interviews with participants recruited through a national patient's association (n = 25). Qualitative thematic analysis revealed three main categories of accounts: (1) justifying the decision "not to know", because either no clinical benefit was expected or predictive knowledge was anticipated as psychologically burdensome; (2) prioritizing everyday life, maintaining hope and the goal of living a valid life; and (3) the wish to know: ambivalence and conflict within the family. Findings suggest the value of genetic information is often questioned when no effective treatment or cure is available; and that people have different tolerance thresholds for predictive information, and this impacts individuals within the family differently. We discuss this in the context of the making of "responsible" decisions, and of the tensions that may arise within families between the best interests or wishes of a person and those of other family members. We hope this will clarify the reasoning of those who opt for non-engagement with medical genetic services and, more specifically, pre-symptomatic testing. Further, we hope it will be relevant for the provision of genetic counselling and psychosocial support to such families.

Mitochondrial DNA haplogroups and age at onset of Machado–Joseph disease/spinocerebellar ataxia type 3: a study in patients from multiple populations

Mitochondrial dysfunction has been implicated in the pathogenesis of several neurodegenerative disorders, including Machado-Joseph disease (MJD), an autosomal dominant late-onset polyglutamine ataxia that results from an unstable expansion of a CAG tract in the ATXN3 gene. The size of the CAG tract only partially explains age at onset (AO), highlighting the existence of disease modifiers. Mitochondrial DNA (mtDNA) haplogroups have been associated with clinical presentation in other polyglutamine disorders, constituting potential modifiers of MJD phenotype. A cross-sectional study, using 235 unrelated patients from Portugal, Brazil, India and Japan, was performed to investigate if mtDNA haplogroups contribute to AO of MJD. mtDNA haplogroups were obtained after sequencing the mtDNA hypervariable region I. Patients were classified in 15 phylogenetically related haplogroup clusters. The AO was significantly different among populations, implying the existence of other non-CAG factors, which seem to be population specific. In the Portuguese population, patients classified as belonging to haplogroup JT presented the earliest onset (estimated onset 34.6years of age). Haplogroups W and X seem to have a protective effect, causing a delay in onset (estimated onset 47years of age). No significant association between haplogroup clusters and AO was detected in the other populations or when all patients were pooled. Although haplogroup JT has already been implicated in other neurodegenerative disorders, no previous reports of an association between haplogroups W and X and disease were found. These findings suggest that haplogroups JT, W and X modify AO in MJD. Replication studies should be performed in European populations, where the frequency of the candidate modifiers is similar.

Polymorphisms in DNA methylation–related genes are linked to the phenotype of Machado-Joseph disease

DNA methylation has been reported as an important regulator of genomic structure stability, including large tandem repeats. To test the modulation effect of variants in DNA methylation–related genes on distribution of expanded (CAG)n alleles and age at onset (AO) of patients with Machado-Joseph disease (MJD), we conducted an association analysis on 23 selected SNPs in these genes in 613 patients with MJD and 581 controls. There were significant differences in the distribution of rs12957023 between patients and controls (OR = 1.296, p = 0.007 and OR = 1.206, p = 0.008, for genotype and alleles, respectively). The distribution of (CAG)n size was also different between patients carrying a CC and the other genotypes (TT and TC, p = 0.011 for expanded (CAG)n and p = 0.012 for normal size alleles), indicating that DNA methylation might modulate the (CAG)n instability. We found also that rs13420827 in DNMT3A and rs7354779 in DNMT3L contribute to AO of MJD (p = 0.019 and p = 0.008, respectively). In conclusion, our data provide the first evidence that SNPs in DNA methylation–related genes may contribute to (CAG)n instability and modulate the AO of this disease.

Pharmacological enhancement of retinoid-related orphan receptor α function mitigates spinocerebellar ataxia type 3 pathology

Cerebellar Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex, and damage to PCs results in motor deficits. Spinocerebellar ataxia type 3 (SCA3, also known as Machado–Joseph disease), a hereditary neurodegenerative disease, is caused by an abnormal expansion of the polyglutamine tract in the causative ATXN3 protein. SCA3 affects a wide range of cells in the central nervous system, including those in the cerebellum. To unravel SCA3 pathology, we used adeno-associated virus serotype 9 (AAV9) vectors to express full-length ATXN3 with an abnormally expanded 89 polyglutamine stretch (ATXN3[Q89]) in cerebellar neurons of mature wild-type mice. Mice expressing ATXN3[Q89] exhibited motor impairment in a manner dependent on the viral titer. Immunohistochemistry of the cerebellum showed ubiquitinated nuclear aggregates in PCs; degeneration of PC dendrites; and a significant decrease in multiple proteins including retinoid-related orphan receptor α (RORα), a transcription factor, and type 1 metabotropic glutamate receptor (mGluR1) signaling molecules. Patch clamp analysis of ATXN3[Q89]-expressing PCs revealed marked defects in mGluR1 signaling. Notably, the emergence of behavioral, morphological, and functional defects was inhibited by a single injection of SR1078, an RORα/γ agonist. These results suggest that RORα plays a key role in mutant ATXN3-mediated aberrant phenotypes and that the pharmacological enhancement of RORα could function as a method for therapeutic intervention in SCA3.