TGM6 might not be a specific causative gene for spinocerebellar ataxia resulting from genetic analysis and functional study.

OBJECTIVE: To investigate whether TGM6 is a specific causative gene for spinocerebellar ataxia type 35 (SCA35). MATERIALS AND METHODS: The next-generation sequencing (NGS) data consisted of 47 SCA, 762 non-SCA patients and 2827 normal controls were analyzed. The allele frequencies of low frequent and deleterious TGM6 variants were compared. Functional studies were performed in five widely distributed variants (V314M, R342Q, P347L, V391M, L517W). RESULTS: Two TGM6 detrimental variants were identified in one SCA patient, 14 in non-SCA patients and 43 in normal controls, the allele frequencies of TGM6 variants did not differ among the SCA and other controls. Seven reported pathogenic variants (c.7 + 1G > T, c.331C > T, c.1171G > A, c.1478C > T, c.1528G > C, c.1550 T > G and c.1722_1724delAGA) were identified in patients with various neurologic diseases or normal controls. All the 5 widely distributed variants led to destabilization and significantly reduction of enzymatic activity of TG6 as the reported pathogenic mutations. CONCLUSIONS: TGM6 might not be a specific causative gene for SCA35, the relevant clinical consult or diagnostic should be pay more attention.

Inhibition of NF-κB signaling in IKKßF/F;LysM Cre mice causes motor deficits but does not alter pathogenesis of Spinocerebellar ataxia type 1.

Spinocerebellar Ataxia type 1 (SCA1) is a fatal neurodegenerative genetic disease that is characterized by pronounced neuronal loss and gliosis in the cerebellum. We have previously demonstrated microglial activation, measured as an increase in microglial density in cerebellar cortex and an increase in the production of pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-α), in the cerebellum of the ATXN1[82Q] transgenic mouse model of SCA1. To examine the role of activated state of microglia in SCA1, we used a Cre-Lox approach with IKKßF/F;LysM Cre mice intended to reduce inflammatory NF-κB signaling, selectively in microglia. ATXN1[82Q];IKKßF/F;LysM Cre mice showed reduced cerebellar microglial density and production of TNFα compared to ATXN1[82Q] mice, yet reducing NF-κB did not ameliorate motor impairments and cerebellar cellular pathologies. Unexpectedly, at 12 weeks of age, control IKKßF/F;LysM Cre mice showed motor deficits equal to ATXN1[82Q] mice that were dissociated from any obvious neurodegenerative changes in the cerebellum, but were rather associated with a developmental impairment that presented as a retention of climbing fiber synaptic terminals on the soma of Purkinje neurons. These results indicate that NF-κB signaling is required for increase in microglial numbers and TNF-α production in the cerebella of ATXN1[82Q] mouse model of SCA1. Furthermore, these results elucidate a novel role of canonical NF-κB signaling in pruning of surplus synapses on Purkinje neurons in the cerebellum during development.

Ca2+ signaling and spinocerebellar ataxia.

Spinocerebellar ataxia (SCA) is a neural disorder, which is caused by degenerative changes in the cerebellum. SCA is primarily characterized by gait ataxia, and additional clinical features include nystagmus, dysarthria, tremors and cerebellar atrophy. Forty-four hereditary SCAs have been identified to date, along with >35 SCA-associated genes. Despite the great diversity and distinct functionalities of the SCA-related genes, accumulating evidence supports the occurrence of a common pathophysiological event among several hereditary SCAs. Altered calcium (Ca2+) homeostasis in the Purkinje cells (PCs) of the cerebellum has been proposed as a possible pathological SCA trigger. In support of this, signaling events that are initiated from or lead to aberrant Ca2+ release from the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1), which is highly expressed in cerebellar PCs, seem to be closely associated with the pathogenesis of several SCA types. In this review, we summarize the current research on pathological hereditary SCA events, which involve altered Ca2+ homeostasis in PCs, through IP3R1 signaling.

[Advance in research on spinocerebellar ataxia 2].

Spinocerebellar ataxia type 2 (SCA2) is a rare autosomal dominant progressive degenerative disease of the nervous system, which is characterized by a progressive cerebellar syndrome associated with saccadic eye scan, peripheral neuropathy, cognitive disorders, and other multisystem features. The gene predisposing to SCA2 has been mapped, which encodes the ataxin 2 protein. A CAG repeat expansion in the coding region of ATXN2 gene can cause extension of polyglutamine chain in the protein. This paper reviews recent progress made in the research on SCA2 in regard to its clinical features, pathology, etiology, pathogenesis and treatment.

Spinocerebellar ataxia type 12: clues to pathogenesis.

PURPOSE OF REVIEW: Spinocerebellar ataxia type 12 (SCA12) is a rare autosomal dominant neurodegenerative disease characterized by tremor, gait abnormalities, and neuropsychiatric syndromes. The location of the causative CAG/CTG expansion mutation in PPP2R2B, a gene encoding regulatory units of the protein phosphatase 2A, may provide unique insights into the pathogenesis of neurodegeneration. RECENT FINDINGS: The first neuropathological examination of a brain from an SCA12 patient revealed both cerebellar and cerebral cortical atrophy, with a noted loss of Purkinje cells and no evidence of polyglutamine aggregates. Molecular investigations have demonstrated considerable complexity of PPP2R2B, which appears to encode at least eight isoforms each with a different N-terminal region. The repeat potentially influences PPP2R2B expression, and is itself included in several splice variants, falling within an open reading frame of at least one of these variants. SUMMARY: The current data suggest at least two nonmutually exclusive hypotheses of SCA12 neurodegeneration. First, the repeat may influence PPP2R2B expression, by altering promoter activity, splicing, or transcript stability. This hypothesis would predict that the mutation changes the regulation of protein phosphatase 2A, with implications for the phosphoproteome. Alternatively, the repeat itself may be expressed and have toxic properties, though perhaps not through polyglutamine tracts. Either hypothesis may provide novel insight into the pathogenesis of neurodegeneration.

Secondary orthostatic tremor in the setting of cerebellar degeneration.

Orthostatic tremor (OT) and cerebellar ataxia are uncommon and difficult to treat. We present two patients with OT and cerebellar degeneration, one of whom had spinocerebellar ataxia type 2 and a good treatment response.

Spinocerebellar ataxia 7 (SCA7) in Indian population: predilection of ATXN7-CAG expansion mutation in an ethnic population.

BACKGROUND & OBJECTIVES: Spinocerebellar ataxia 7 (SCA7) is a rare form of neurodegenerative disorder with the clinical manifestation of cerebellar ataxia and retinal degeneration. In this study we describe the clinico-genetic characteristics of nine SCA7 families of Indian origin and cross compare these with other available worldwide studies. METHODS: Thirty five individuals from nine SCA7 families were clinico-genetically characterized and CAG repeat distribution analysis was carried out in 382 control DNA samples from healthy controls (derived from 21 diverse Indian populations based on ethnic and linguistic and geographical location). RESULTS: Of the nine families studied, 22 affected individuals and one asymptomatic carrier were identified. The average age at disease onset was 23.4±12.6 yr. The length of expanded CAG ranged from 40-94 with mean value of 53.2±13.9. The main clinical findings in affecteds individuals included cerebellar ataxia, and retinal degeneration along with hyper-reflexia (95%), slow saccades (85%) and spasticity (45%). Analysis of the association of number of CAG repeats with disease onset revealed that <49 repeats were associated with earlier age at onset in South East Asians compared to European populations. Further analysis of CAG repeats from 21 diverse Indian populations showed pre-mutable repeats (28-34) alleles in the IE-N-LP2 population. Six of the nine families identified in this study belonged to the same ethnic population. INTERPRETATIONS & CONCLUSION: Our results show that presenece of SCA7 is relatively rare and confined to one ethnic group from Haryana region of India. We observed a homogeneous phenotypic expression of SCA7 mutation as described earlier and an earlier age of onset in our patients with CAG <49. The identification of pre-mutable allele in IE-N-LP2 suggests this population to be at the risk of SCA7.

Comparing speech characteristics in spinocerebellar ataxias type 3 and type 6 with Friedreich ataxia.

Patterns of dysarthria in spinocerebellar ataxias (SCAs) and their discriminative features still remain elusive. Here we aimed to compare dysarthria profiles of patients with (SCA3 and SCA6 vs. Friedreich ataxia (FRDA), focussing on three particularly vulnerable speech parameters (speaking rate, prosodic modulation, and intelligibility) in ataxic dysarthria as well as on a specific oral non-speech variable of ataxic impairment, i.e., the irregularity of oral motor diadochokinesis (DDK). 30 Patients with SCA3, SCA6, and FRDA, matched for group size (n = 10 each), disease severity, and disease duration produced various speech samples and DDK tasks. A discriminant analysis was used to differentiate speech and non-speech parameters between groups. Regularity of DDK was specifically impaired in SCA3, whereas impairments of speech parameters, i.e., rate and modulation were stronger affected in SCA6. Speech parameters are particularly vulnerable in SCA6, while non-speech oral motor features are notably impaired in SCA3.

Insights from cerebellar transcriptomic analysis into the pathogenesis of ataxia.

IMPORTANCE: The core clinical and neuropathological feature of the autosomal dominant spinocerebellar ataxias (SCAs) is cerebellar degeneration. Mutations in the known genes explain only 50% to 60% of SCA cases. To date, no effective treatments exist, and the knowledge of drug-treatable molecular pathways is limited. The examination of overlapping mechanisms and the interpretation of how ataxia genes interact will be important in the discovery of potential disease-modifying agents. OBJECTIVES: To address the possible relationships among known SCA genes, predict their functions, identify overlapping pathways, and provide a framework for candidate gene discovery using whole-transcriptome expression data. DESIGN, SETTING, AND PARTICIPANTS: We have used a systems biology approach based on whole-transcriptome gene expression analysis. As part of the United Kingdom Brain Expression Consortium, we analyzed the expression profile of 788 brain samples obtained from 101 neuropathologically healthy individuals (10 distinct brain regions each). Weighted gene coexpression network analysis was used to cluster 24 SCA genes into gene coexpression modules in an unsupervised manner. The overrepresentation of SCA transcripts in modules identified in the cerebellum was assessed. Enrichment analysis was performed to infer the functions and molecular pathways of genes in biologically relevant modules. MAIN OUTCOMES AND MEASURES: Molecular functions and mechanisms implicating SCA genes, as well as lists of relevant coexpressed genes as potential candidates for novel SCA causative or modifier genes. RESULTS: Two cerebellar gene coexpression modules were statistically enriched in SCA transcripts (P = .021 for the tan module and P = 2.87 × 10-5 for the light yellow module) and contained established granule and Purkinje cell markers, respectively. One module includes genes involved in the ubiquitin-proteasome system and contains SCA genes usually associated with a complex phenotype, while the other module encloses many genes important for calcium homeostasis and signaling and contains SCA genes associated mostly with pure ataxia. CONCLUSIONS AND RELEVANCE: Using normal gene expression in the human brain, we identified significant cell types and pathways in SCA pathogenesis. The overrepresentation of genes involved in calcium homeostasis and signaling may indicate an important target for therapy in the future. Furthermore, the gene networks provide new candidate genes for ataxias or novel genes that may be critical for cerebellar function.

The evaluation of swallowing in patients with spinocerebellar ataxia and oropharyngeal dysphagia: A comparison study of videofluoroscopic and sonar doppler

Introduction: Spinocerebellar ataxia (SCA) is a degenerative disease that can cause loss of coordination of voluntary muscle movement such as that required for swallowing. Aims: The purposes of this cross-sectional and comparative case study were: (1) to assess the severity of dysphagia through a videofluoroscopic swallow study, and (2) to compare differences in frequency, intensity, and duration of sound waves produced during swallowing in normal and SCA patients by using sonar Doppler. Method: During swallow evaluation using videofluoroscopy, a sonar Doppler transducer was placed on the right side of the neck, at the lateral edge of the trachea, just below the cricoid cartilage to capture the sounds of swallowing in 30 SCA patients and 30 controls. Result: The prevalence in the dynamic evaluation of swallowing videofluoroscopy was by changes in the oral phase of swallowing. The analysis of variance of the averages found in each variable - frequency, intensity and duration of swallowing - shows there was a significant correlation when compared to the healthy individual curve. Conclusion: The study demonstrates the prevalence of oral dysphagia observed in dynamic videofluoroscopic swallow evaluation. In patients with SCA, the mean initial frequency (IF), initial intensity (II), and final intensity (FI) were higher and the time (T) and peak frequency (PF) were lower, demonstrating a pattern of cricopharyngeal opening very close to that found in normal populations...

Role of the CCAAT-binding protein NFY in SCA17 pathogenesis.

Spinocerebellar ataxia 17 (SCA17) is caused by expansion of the polyglutamine (polyQ) tract in human TATA-box binding protein (TBP) that is ubiquitously expressed in both central nervous system and peripheral tissues. The spectrum of SCA17 clinical presentation is broad. The precise pathogenic mechanism in SCA17 remains unclear. Previously proteomics study using a cellular model of SCA17 has revealed reduced expression of heat shock 70 kDa protein 5 (HSPA5) and heat shock 70 kDa protein 8 (HSPA8), suggesting that impaired protein folding may contribute to the cell dysfunction of SCA17 (Lee et al., 2009). In lymphoblastoid cells, HSPA5 and HSPA8 expression levels in cells with mutant TBP were also significantly lower than that of the control cells (Chen et al., 2010). As nuclear transcription factor Y (NFY) has been reported to regulate HSPA5 transcription, we focused on if NFY activity and HSPA5 expression in SCA17 cells are altered. Here, we show that TBP interacts with NFY subunit A (NFYA) in HEK-293 cells and NFYA incorporated into mutant TBP aggregates. In both HEK-293 and SH-SY5Y cells expressing TBP/Q(61~79), the level of soluble NFYA was significantly reduced. In vitro binding assay revealed that the interaction between TBP and NFYA is direct. HSPA5 luciferase reporter assay and endogenous HSPA5 expression analysis in NFYA cDNA and siRNA transfection cells further clarified the important role of NFYA in regulating HSPA5 transcription. In SCA17 cells, HSPA5 promoter activity was activated as a compensatory response before aggregate formation. NFYA dysfunction was indicated in SCA17 cells as HSPA5 promoter activity reduced along with TBP aggregate formation. Because essential roles of HSPA5 in protection from neuronal apoptosis have been shown in a mouse model, NFYA could be a target of mutant TBP in SCA17.

Spinocerebellar ataxia: a rational approach to aetiological diagnosis.

The objective of this study was to determine the main causal diagnosis for spinocerebellar ataxia (SCA) in a geographically defined population of ataxia patients and to suggest a rational basis for choosing appropriate clinical and paraclinical assessments. Given the many aetiologies responsible for SCA, the diagnosis requires the performance of a wide range of paraclinical analyses. At present, there is no consensus on the diagnostic value of these examinations. Furthermore, most of the currently available data gathered by reference centres suffer from selection bias. We performed a prospective study of consecutive cerebellar ataxia patients referred by their family doctors to a university hospital in northern France. Multiple system atrophy and obvious secondary causes (e.g. alcoholism) were excluded by our screening process. The patient's family members were also assessed. Of the 204 patients examined, 47% presented autosomal dominant ataxia and 33% presented sporadic ataxia. Autosomal recessive ataxia was rare (8%) and age at onset was significantly earlier for this condition than for other forms. An aetiological diagnosis was established in 44% of patients, a plausible hypothesis could be formed in 13% of cases, and no diagnosis was made in the remaining 44%. Established diagnoses included SCA1, SCA2, SCA3 and SCA6 mutations, Friedreich's ataxia, and one rare case of ataxia associated with anti-glutamic acid decarboxylase antibodies. Two families presented ataxia associated with autosomal, dominant, optic atrophy with an OPA1 mutation. Mitochondrial diseases were suspected in about 10% of patients. In SCA, reliable determination of the transmission mode always requires the assessment of family members. Mitochondrial disease may be an emerging cause of ataxia. Metabolite assays appeared to be of little value when systematically performed and so should be prescribed only by metabolic disorder specialists in selected cases of sporadic and recessive ataxia. Ophthalmological examination was the most helpful physiological assessment.

Role of inositol 1,4,5-trisphosphate receptors in pathogenesis of Huntington's disease and spinocerebellar ataxias.

Huntington's disease (HD) and spinocerebellar ataxias (SCAs) are autosomal-dominant neurodegenerative disorders. HD is caused by polyglutamine (polyQ) expansion in the amino-terminal region of a protein huntingtin (Htt) and primarily affects medium spiny striatal neurons (MSN). Many SCAs are caused by polyQ-expansion in ataxin proteins and primarily affect cerebellar Purkinje cells. The reasons for neuronal dysfunction and death in HD and SCAs remain poorly understood and no cure is available for the patients. Our laboratory discovered that mutant huntingtin, ataxin-2 and ataxin-3 proteins specifically bind to the carboxy-terminal region of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1), an intracellular Ca(2+) release channel. Moreover, we found that association of mutant huntingtin or ataxins with IP(3)R1 causes sensitization of IP(3)R1 to activation by IP(3) in planar lipid bilayers and in neuronal cells. These results suggested that deranged neuronal Ca(2+) signaling might play an important role in pathogenesis of HD, SCA2 and SCA3. In support of this idea, we demonstrated a connection between abnormal Ca(2+) signaling and neuronal cell death in experiments with HD, SCA2 and SCA3 transgenic mouse models. Additional data in the literature indicate that abnormal neuronal Ca(2+) signaling may also play an important role in pathogenesis of SCAl, SCA5, SCA6, SCA14 and SCA15/16. Based on these results I propose that IP(3)R and other Ca(2+) signaling proteins should be considered as potential therapeutic targets for treatment of HD and SCAs.

Two novel homozygous SACS mutations in unrelated patients including the first reported case of paternal UPD as an etiologic cause of ARSACS.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay, more commonly known as ARSACS, is an early-onset cerebellar ataxia with spasticity, amyotrophy, nystagmus, dysarthria, and peripheral neuropathy. SACS is the only gene known to be associated with the ARSACS phenotype. To date, 55 mutations have been reported; of these, only five in Italian patients. We found two novel homozygous nonsense mutations in the giant exon of SACS gene in two unrelated patients with classical ARSACS phenotype. Characterization of the homozygous nature of the mutations through genotyping of the parents, quantitative DNA analysis and indirect STS studies permitted us to confirm in one of the cases that uniparental isodisomy of the paternal chromosome 13 carrying the mutated SACS gene played an etiologic role in the disease.