Longitudinal analysis of contrast acuity in Friedreich ataxia

Objective

To determine the natural history of contrast acuity in Friedreich ataxia.

Methods

In the Friedreich Ataxia–Clinical Outcome Measures Study, participants (n = 764) underwent binocular high- and low-contrast visual acuity testing at annual study visits. Mixed-effects linear regression was used to model visual acuity as a function of time, with random intercepts and slopes to account for intraindividual correlation of repeated measurements. A time-varying covariate was used to adjust for diabetes, and interaction terms were used to assess for effect modification by GAA repeat length, disease duration, and other variables.

Results

Across a median of 4.4 years of follow-up, visual acuity decreased significantly at 100% contrast (−0.37 letters/y, 95% confidence interval [CI]: −0.52 to −0.21), 2.5% contrast (−0.81 letters/year, 95% CI: −0.99 to −0.65), and 1.25% contrast (−1.12 letters/y, 95% CI: −1.29 to −0.96 letters/year). There was a significant interaction between time and GAA repeat length such that the rate of decrease in visual acuity was greater for patients with higher GAA repeat lengths at 2.5% contrast (p = 0.018) and 1.25% contrast (p = 0.043) but not 100% contrast. There was no effect modification by age at onset after adjusting for GAA repeat length.

Conclusions

Low-contrast visual acuity decreases linearly over time in Friedreich ataxia, and the rate of decrease is greater at higher GAA repeat lengths. Contrast sensitivity has the potential to serve as a biomarker and surrogate outcome in future studies of Friedreich ataxia.

The Initial Symptom and Motor Progression in Spinocerebellar Ataxias

The aim of this study is to determine whether the initial symptom associates with motor progression in spinocerebellar ataxias (SCAs). SCAs are clinically heterogeneous and the initial presentation may represent different subtypes of SCA with different motor progression. We studied 317 participants with SCAs1, 2, 3, and 6 from the Clinical Research Consortium for SCAs (CRC-SCA) and repeatedly measured the severity of ataxia for 2 years. SCA patients were divided into gait-onset and non-gait-onset (speech, vision, and hand dexterity) groups based on the initial presentation. In addition to demographic comparison, we employed regression models to study ataxia progression in these two groups after adjusting for age, sex, and pathological CAG repeats. The majority of SCA patients had gait abnormality as an initial presentation. The pathological CAG repeat expansions were similar between the gait-onset and non-gait-onset groups. In SCA1, gait-onset group progressed slower than non-gait-onset group, while gait-onset SCA6 group progressed faster than their counterpart. In addition, the disease presented 9 years later for SCA2 gait-onset group than non-gait-onset group. Initial symptoms of SCA3 did not influence age of onset or disease progression. The initial symptom in each SCA has a different influence on age of onset and motor progression. Therefore, gait and non-gait-onset groups of SCAs might represent different subtypes of the diseases.

Comprehensive systematic review summary: Treatment of cerebellar motor dysfunction and ataxia: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology

OBJECTIVE

To systematically review evidence regarding ataxia treatment.

METHODS

A comprehensive systematic review was performed according to American Academy of Neurology methodology.

CONCLUSIONS

For patients with episodic ataxia type 2, 4-aminopyridine 15 mg/d probably reduces ataxia attack frequency over 3 months (1 Class I study). For patients with ataxia of mixed etiology, riluzole probably improves ataxia signs at 8 weeks (1 Class I study). For patients with Friedreich ataxia or spinocerebellar ataxia (SCA), riluzole probably improves ataxia signs at 12 months (1 Class I study). For patients with SCA type 3, valproic acid 1,200 mg/d possibly improves ataxia at 12 weeks. For patients with spinocerebellar degeneration, thyrotropin-releasing hormone possibly improves some ataxia signs over 10 to 14 days (1 Class II study). For patients with SCA type 3 who are ambulatory, lithium probably does not improve signs of ataxia over 48 weeks (1 Class I study). For patients with Friedreich ataxia, deferiprone possibly worsens ataxia signs over 6 months (1 Class II study). Data are insufficient to support or refute the use of numerous agents. For nonpharmacologic options, in patients with degenerative ataxias, 4-week inpatient rehabilitation probably improves ataxia and function (1 Class I study); transcranial magnetic stimulation possibly improves cerebellar motor signs at 21 days (1 Class II study). For patients with multiple sclerosis-associated ataxia, the addition of pressure splints possibly has no additional benefit compared with neuromuscular rehabilitation alone (1 Class II study). Data are insufficient to support or refute use of stochastic whole-body vibration therapy (1 Class III study).

Correction to: SPG7 and Impaired Emotional Communication

The original version of this article unfortunately contained an incorrect assignment of affiliations of Linwei Zhang and Tetsuo Ashizawa.

Dystonia and ataxia progression in spinocerebellar ataxias

BACKGROUND

Dystonia is a common feature in spinocerebellar ataxias (SCAs). Whether the presence of dystonia is associated with different rate of ataxia progression is not known.

OBJECTIVES

To study clinical characteristics and ataxia progression in SCAs with and without dystonia.

METHODS

We studied 334 participants with SCA 1, 2, 3 and 6 from the Clinical Research Consortium for Spinocerebellar Ataxias (CRC-SCA) and compared the clinical characteristics of SCAs with and without dystonia. We repeatedly measured ataxia progression by the Scale for Assessment and Rating of Ataxia every 6 months for 2 years. Regression models were employed to study the association between dystonia and ataxia progression after adjusting for age, sex and pathological CAG repeats. We used logistic regression to analyze the impact of different repeat expansion genes on dystonia in SCAs.

RESULTS

Dystonia was most commonly observed in SCA3, followed by SCA2, SCA1, and SCA6. Dystonia was associated with longer CAG repeats in SCA3. The CAG repeat number in TBP normal alleles appeared to modify the presence of dystonia in SCA1. The presence of dystonia was associated with higher SARA scores in SCA1, 2, and 3. Although relatively rare in SCA6, the presence of dystonia was associated with slower progression of ataxia.

CONCLUSIONS

The presence of dystonia is associated with greater severity of ataxia in SCA1, 2, and 3, but predictive of a slower progression in SCA6. Complex genetic interactions among repeat expansion genes can lead to diverse clinical symptoms and progression in SCAs.

Postural Tremor and Ataxia Progression in Spinocerebellar Ataxias

BACKGROUND

Postural tremor can sometimes occur in spinocerebellar ataxias (SCAs). However, the prevalence and clinical characteristics of postural tremor in SCAs are poorly understood, and whether SCA patients with postural tremor have different ataxia progression is not known.

METHODS

We studied postural tremor in 315 patients with SCA1, 2, 3, and 6 recruited from the Clinical Research Consortium for Spinocerebellar Ataxias (CRC-SCA), which consists of 12 participating centers in the United States, and we evaluated ataxia progression in these patients from January 2010 to August 2012.

RESULTS

Among 315 SCA patients, postural tremor was most common in SCA2 patients (SCA1, 5.8%; SCA2, 27.5%; SCA3, 12.4%; SCA6, 16.9%; p = 0.007). SCA3 patients with postural tremor had longer CAG repeat expansions than SCA3 patients without postural tremor (73.67 ± 3.12 vs. 70.42 ± 3.96, p = 0.003). Interestingly, SCA1 and SCA6 patients with postural tremor had a slower rate of ataxia progression (SCA1, β = -0.91, p < 0.001; SCA6, β = -1.28, p = 0.025), while SCA2 patients with postural tremor had a faster rate of ataxia progression (β = 1.54, p = 0.034). We also found that the presence of postural tremor in SCA2 patients could be influenced by repeat expansions of ATXN1 (β = -1.53, p = 0.037) and ATXN3 (β = 0.57, p = 0.018), whereas postural tremor in SCA3 was associated with repeat lengths in TBP (β = 0.63, p = 0.041) and PPP2R2B (β = -0.40, p = 0.032).

DISCUSSION

Postural tremor could be a clinical feature of SCAs, and the presence of postural tremor could be associated with different rates of ataxia progression. Genetic interactions between ataxia genes might influence the brain circuitry and thus affect the clinical presentation of postural tremor.

SPG7 and Impaired Emotional Communication

The goal of this report is to describe the genetic mutations of a patient with cerebellar degeneration who had ataxia and impaired emotional communication that led to damage of family relationships. We extracted genomic DNA from peripheral blood lymphocytes and performed whole exome sequencing (WES) in this patient and his unaffected parents and siblings. Found mutations were confirmed by Sanger sequencing in each individual. We found compound heterozygous mutations in the paraplegin (SPG7) gene. One mutated allele has been previously described as a disease-causing missense mutation for spastic paraplegia type 7 (SPG7) (c.1529C > T, p.Ala510Val). The second mutated allele involved a single nucleotide deletion which results in a frameshift in the coding sequence (c.2271delG, p.Met757fs*65). The second allele is similar to, but unique from, other described, SPG7-linked truncation mutations. The abnormal emotional communication in this patient broadens the phenotypic boundary of SPG7.

Comorbid Medical Conditions in Friedreich Ataxia: Association With Inflammatory Bowel Disease and Growth Hormone Deficiency

Friedreich ataxia is a progressive degenerative disease with neurologic and cardiac involvement. This study characterizes comorbid medical conditions in a large cohort of patients with Friedreich ataxia. Patient diagnoses were collected in a large natural history study of 641 subjects. Prevalence of diagnoses in the cohort with Friedreich ataxia was compared with prevalence in the population without Friedreich ataxia. Ten patients (1.6%) had inflammatory bowel disease, 3.5 times more common in this cohort of individuals with Friedreich ataxia than in the general population. Four subjects were growth hormone deficient, reflecting a prevalence in Friedreich ataxia that is 28 times greater than the general population. The present study identifies specific diagnoses not traditionally associated with Friedreich ataxia that are found at higher frequency in this disease. These associations could represent coincidence, shared genetic background, or potentially interactive disease mechanisms with Friedreich ataxia.

Genome modification leads to phenotype reversal in human myotonic dystrophy type 1 induced pluripotent stem cell-derived neural stem cells

Myotonic dystrophy type 1 (DM1) is caused by expanded CTG repeats in the 3'-untranslated region (3' UTR) of the DMPK gene. Correcting the mutation in DM1 stem cells would be an important step toward autologous stem cell therapy. The objective of this study is to demonstrate in vitro genome editing to prevent production of toxic mutant transcripts and reverse phenotypes in DM1 stem cells. Genome editing was performed in DM1 neural stem cells (NSCs) derived from human DM1 induced pluripotent stem (iPS) cells. An editing cassette containing SV40/bGH polyA signals was integrated upstream of the CTG repeats by TALEN-mediated homologous recombination (HR). The expression of mutant CUG repeats transcript was monitored by nuclear RNA foci, the molecular hallmarks of DM1, using RNA fluorescence in situ hybridization. Alternative splicing of microtubule-associated protein tau (MAPT) and muscleblind-like (MBNL) proteins were analyzed to further monitor the phenotype reversal after genome modification. The cassette was successfully inserted into DMPK intron 9 and this genomic modification led to complete disappearance of nuclear RNA foci. MAPT and MBNL 1, 2 aberrant splicing in DM1 NSCs were reversed to normal pattern in genome-modified NSCs. Genome modification by integration of exogenous polyA signals upstream of the DMPK CTG repeat expansion prevents the production of toxic RNA and leads to phenotype reversal in human DM1 iPS-cells derived stem cells. Our data provide proof-of-principle evidence that genome modification may be used to generate genetically modified progenitor cells as a first step toward autologous cell transfer therapy for DM1.

Repetitive finger movement performance differs among Parkinson's disease, Progressive Supranuclear Palsy, and spinocerebellar ataxia

Background

Differentiating movement disorders is critical for appropriate treatment, prognosis, and for clinical trials. In clinical trials this is especially important as effects can be diluted by inclusion of inappropriately diagnosed participants. In early disease duration phases, disorders often have overlapping clinical features, such as impairments in repetitive finger movement, making diagnosis challenging. The purpose of this pilot study was to examine and compare repetitive finger movement performance in participants diagnosed with idiopathic Parkinson’s disease, Progressive Supranuclear Palsy, and spinocerebellar ataxias.

Methods

Participants completed an unconstrained index finger flexion/extension movement (i.e. finger tap) in time with an incremental acoustic tone. Measures of movement rate, movement amplitude, and coefficient of variation were compared among groups.

Results

Significant differences between groups were revealed for movement rate at faster tone rates. Participants with Parkinson’s disease tended to tap faster than the tone rate while participants with Progressive Supranuclear Palsy and spinocerebellar ataxia tended to tap slower. No significant differences were revealed for movement amplitude, but participants with spinocerebellar ataxia demonstrated greater variance in amplitude than participants with Parkinson’s disease.

Conclusion

Quantitative analysis of repetitive finger movement performance at faster rates may be helpful to differentiate Parkinson’s Disease, Progressive Supranuclear Palsy and spinocerebellar ataxia.

Altered activation of the tibialis anterior in individuals with Pompe disease: Implications for motor unit dysfunction

INTRODUCTION

Pompe disease is a progressive disease that affects skeletal muscles and leads to loss of ambulation. We investigated the activation of the tibialis anterior (TA) in late-onset Pompe disease (LOPD) individuals during maximal voluntary contraction (MVC) and evoked involuntary responses.

METHODS

Four LOPD patients and matched control subjects performed MVC of the TA using dorsiflexion and TA evoked responses. Activation of the TA was recorded with surface electromyography.

RESULTS

The Pompe patients exhibited greater power at frequencies below 60 Hz and reduced power above 100 Hz. They also exhibited a reduced increase in M-wave and prolonged M-wave latency and duration in response to stimulation.

CONCLUSIONS

These results provide evidence that LOPD individuals have an altered activation pattern of the TA during maximal contractions. The observed activation pattern may reflect impairments in voluntary command, neuromuscular junction pathology, or compensatory drive due to a reduced number of functional motoneurons.

Force dysmetria in spinocerebellar ataxia 6 correlates with functional capacity

Spinocerebellar ataxia type 6 (SCA6) is a genetic disease that causes pure cerebellar degeneration affecting walking, balance, and coordination. One of the main symptoms of SCA6 is dysmetria. The magnitude of dysmetria and its relation to functional capacity in SCA6 has not been studied. Our purpose was to quantify dysmetria and determine the relation between dysmetria and functional capacity in SCA6. Ten individuals diagnosed and genetically confirmed with SCA6 (63.7 ± 7.02 years) and nine age-matched healthy controls (65.9 ± 8.5 years) performed goal-directed isometric contractions with the ankle joint. Dysmetria was quantified as the force and time error during goal-directed contractions. SCA6 functional capacity was determined by ICARS and SARA clinical assessments. We found that SCA6 participants exhibited greater force dysmetria than healthy controls (P < 0.05), and reduced time dysmetria than healthy controls (P < 0.05). Only force dysmetria was significantly related to SCA6 functional capacity, as measured with ICARS kinetic score (R² = 0.63), ICARS total score (R² = 0.43), and SARA total score (R² = 0.46). Our findings demonstrate that SCA6 exhibit force dysmetria and that force dysmetria is associated to SCA6 functional capacity. Quantifying force and time dysmetria in individuals with SCA6 could provide a more objective evaluation of the functional capacity and disease state in SCA6.

Vascular risk factors and clinical progression in spinocerebellar ataxias

Background

The contributions of vascular risk factors to spinocerebellar ataxia (SCA) are not known.

Methods

We studied 319 participants with SCA 1, 2, 3, and 6 and repeatedly measured clinical severity using the Scale for Assessment and Rating of Ataxia (SARA) for 2 years. Vascular risk factors were summarized by CHA₂DS₂-VASc scores as the vascular risk factor index. We employed regression models to study the effects of vascular risk factors on ataxia onset and progression after adjusting for age, sex, and pathological CAG repeats. Our secondary analyses took hyperlipidemia into account.

Results

Nearly 60% of SCA participants were at low vascular risks with CHA₂DS₂-VASc = 0, and 31% scored 2 or greater. Higher CHA₂DS₂-VASc scores were not associated with either earlier onset or faster progression of ataxia. These findings were not altered after accounting for hyperlipidemia.

Discussion

Vascular risks are not common in SCAs and are not associated with earlier onset or faster ataxia progression.

Coenzyme Q10 and spinocerebellar ataxias

The aim of this study was to investigate the association between drug exposure and disease severity in SCA types 1, 2, 3 and 6. The Clinical Research Consortium for Spinocerebellar Ataxias (CRC-SCA) enrolled 319 participants with SCA1, 2, 3, and 6 from 12 medical centers in the United States and repeatedly measured clinical severity by the Scale for Assessment and Rating of Ataxia (SARA), the Unified Huntington's Disease Rating Scale part IV (UHDRS-IV), and the 9-item Patient Health Questionnaire during July 2009 to May 2012. We employed generalized estimating equations in regression models to study the longitudinal effects of coenzyme Q10 (CoQ10), statin, and vitamin E on clinical severity of ataxia after adjusting for age, sex, and pathological CAG repeat number. Cross-sectionally, exposure to CoQ10 was associated with lower SARA and higher UHDRS-IV scores in SCA1 and 3. No association was found between statins, vitamin E, and clinical outcome. Longitudinally, CoQ10, statins, and vitamin E did not change the rates of clinical deterioration indexed by SARA and UHDRS-IV scores within 2 years. CoQ10 is associated with better clinical outcome in SCA1 and 3. These drug exposures did not appear to influence clinical progression within 2 years. Further studies are warranted to confirm the association.

Apraxia in anti-glutamic acid decarboxylase-associated stiff person syndrome: link to corticobasal degeneration?

Corticobasal syndrome (CBS) is associated with asymmetrical rigidity as well as asymmetrical limb-kinetic and ideomotor apraxia. Stiff person syndrome (SPS) is characterized by muscle stiffness and gait difficulties. Whereas patients with CBS have several forms of pathology, many patients with SPS have glutamic acid decarboxylase antibodies (GAD-ab), but these 2 disorders have not been reported to coexist. We report 2 patients with GAD-ab-positive SPS who also had signs suggestive of CBS, including asymmetrical limb rigidity associated with both asymmetrical limb-kinetic and ideomotor apraxia. Future studies should evaluate patients with CBS for GAD-ab and people with SPS for signs of CBS.

Affective communication deficits associated with cerebellar degeneration

The cerebellum has extensive connections with the frontal lobes. Cerebellar injury has been reported to induce frontal-executive cognitive dysfunction and blunting of affect. We examined a patient with idiopathic cerebellar degeneration with impaired family relationships attributed to an "emotional disconnection." Examination revealed ataxia, dysmetria, and adiadochokinesia more severe on the left and frontal-executive dysfunction; memory and cognitive functions were otherwise normal. Testing of emotional communication included assessments of emotional semantic knowledge, emotional prosody, and emotional facial expressions. Comprehension was normal but expression was severely impaired. Cerebellar dysfunction can cause a defect in facial and prosodic emotional communication.

Clinical characteristics of patients with spinocerebellar ataxias 1, 2, 3 and 6 in the US; a prospective observational study

Background

All spinocerebellar ataxias (SCAs) are rare diseases. SCA1, 2, 3 and 6 are the four most common SCAs, all caused by expanded polyglutamine-coding CAG repeats. Their pathomechanisms are becoming increasingly clear and well-designed clinical trials will be needed.

Methods

To characterize the clinical manifestations of spinocerebellar ataxia (SCA) 1, 2, 3 and 6 and their natural histories in the United States (US), we conducted a prospective multicenter study utilized a protocol identical to the European consortium study, using the Scale for the Assessment and Rating of Ataxia (SARA) score as the primary outcome, with follow-ups every 6 months up to 2 years.

Results

We enrolled 345 patients (60 SCA1, 75 SCA2, 138 SCA3 and 72 SCA6) at 12 US centers. SCA6 patients had a significantly later onset, and SCA2 patients showed greater upper-body ataxia than patients with the remaining SCAs. The annual increase of SARA score was greater in SCA1 patients (mean ± SE: 1.61 ± 0.41) than in SCA2 (0.71 ± 0.31), SCA3 (0.65 ± 0.24) and SCA6 (0.87 ± 0.28) patients (p = 0.049). The functional stage also worsened faster in SCA1 than in SCA2, 3 and 6 (p = 0.002).

Conclusions

The proportions of different SCA patients in US differ from those in the European consortium study, but as in the European patients, SCA1 progress faster than those with SCA2, 3 and 6. Later onset in SCA6 and greater upper body ataxia in SCA2 were noted. We conclude that progression rates of these SCAs were comparable between US and Europe cohorts, suggesting the feasibility of international collaborative clinical studies.

Generation of neural cells from DM1 induced pluripotent stem cells as cellular model for the study of central nervous system neuropathogenesis

Dystrophia myotonica type 1 (DM1) is an autosomal dominant multisystem disorder. The pathogenesis of central nervous system (CNS) involvement is poorly understood. Disease-specific induced pluripotent stem cell (iPSC) lines would provide an alternative model. In this study, we generated two DM1 lines and a normal iPSC line from dermal fibroblasts by retroviral transduction of Yamanaka's four factors (hOct4, hSox2, hKlf4, and hc-Myc). Both DM1 and control iPSC clones showed typical human embryonic stem cell (hESC) growth patterns with a high nuclear-to-cytoplasm ratio. The iPSC colonies maintained the same growth pattern through subsequent passages. All iPSC lines expressed stem cell markers and differentiated into cells derived from three embryonic germ layers. All iPSC lines underwent normal neural differentiation. Intranuclear RNA foci, a hallmark of DM1, were detected in DM1 iPSCs, neural stem cells (NSCs), and terminally differentiated neurons and astrocytes. In conclusion, we have successfully established disease-specific human DM1 iPSC lines, NSCs, and neuronal lineages with pathognomonic intranuclear RNA foci, which offer an unlimited cell resource for CNS mechanistic studies and a translational platform for therapeutic development.

New NBIA subtype: genetic, clinical, pathologic, and radiographic features of MPAN

OBJECTIVE

To assess the frequency of mutations in C19orf12 in the greater neurodegeneration with brain iron accumulation (NBIA) population and further characterize the associated phenotype.

METHODS

Samples from 161 individuals with idiopathic NBIA were screened, and C19orf12 mutations were identified in 23 subjects. Direct examinations were completed on 8 of these individuals, and medical records were reviewed on all 23. Histochemical and immunohistochemical studies were performed on brain tissue from one deceased subject.

RESULTS

A variety of mutations were detected in this cohort, in addition to the Eastern European founder mutation described previously. The characteristic clinical features of mitochondrial membrane protein-associated neurodegeneration (MPAN) across all age groups include cognitive decline progressing to dementia, prominent neuropsychiatric abnormalities, and a motor neuronopathy. A distinctive pattern of brain iron accumulation is universal. Neuropathologic studies revealed neuronal loss, widespread iron deposits, and eosinophilic spheroidal structures in the basal ganglia. Lewy neurites were present in the globus pallidus, and Lewy bodies and neurites were widespread in other areas of the corpus striatum and midbrain structures.

CONCLUSIONS

MPAN is caused by mutations in C19orf12 leading to NBIA and prominent, widespread Lewy body pathology. The clinical phenotype is recognizable and distinctive, and joins pantothenate kinase-associated neurodegeneration and PLA2G6-associated neurodegeneration as one of the major forms of NBIA.

Generation of human-induced pluripotent stem cells to model spinocerebellar ataxia type 2 in vitro

Spinocerebellar ataxia type 2 (SCA2) is caused by triple nucleotide repeat (CAG) expansion in the coding region of the ATAXN2 gene on chromosome 12, which produces an elongated, toxic polyglutamine tract, leading to Purkinje cell loss. There is currently no effective therapy. One of the main obstacles that hampers therapeutic development is lack of an ideal disease model. In this study, we have generated and characterized SCA2-induced pluripotent stem (iPS) cell lines as an in vitro cell model. Dermal fibroblasts (FBs) were harvested from primary cultures of skin explants obtained from a SCA2 subject and a healthy subject. For reprogramming, hOct4, hSox2, hKlf4, and hc-Myc were transduced to passage-3 FBs by retroviral infection. Both SCA2 iPS and control iPS cells were successfully generated and showed typical stem cell growth patterns with normal karyotype. All iPS cell lines expressed stem cell markers and differentiated in vitro into cells from three embryonic germ layers. Upon in vitro neural differentiation, SCA2 iPS cells showed abnormality in neural rosette formation but successfully differentiated into neural stem cells (NSCs) and subsequent neural cells. SCA2 and normal FBs showed a comparable level of ataxin-2 expression; whereas SCA2 NSCs showed less ataxin-2 expression than normal NSCs and SCA2 FBs. Within the neural lineage, neurons had the most abundant expression of ataxin-2. Time-lapsed neural growth assay indicated terminally differentiated SCA2 neural cells were short-lived compared with control neural cells. The expanded CAG repeats of SCA2 were stable throughout reprogramming and neural differentiation. In conclusion, we have established the first disease-specific human SCA2 iPS cell line. These mutant iPS cells have the potential for neural differentiation. These differentiated neural cells harboring mutations are invaluable for the study of SCA2 pathogenesis and therapeutic drug development.

Clinical challenges in the ataxias

Ataxias are rare diseases and the etiologic heterogeneity make individual entities even rarer. There are still substantial numbers of patients who are still poorly understood. Available assessment techniques still point to large numbers of patients needed for clinical trials and the need for cooperative efforts, better assessment tools and novel trial designs. Better understanding of neural circuitry abnormalities may lead to more effective symptomatic therapy. Opportunities exist for targeting at risk individuals for effective therapies but how this can be done is not clear. Preventive strategies may become feasible in many ataxias.