Hsuan-Yuan Lin

Genetic testing in spinocerebellar ataxia in Taiwan: Expansions of trinucleotide repeats in SCA8 and SCA17 are associated with typical Parkinson's disease

DNA tests in normal subjects and patients with ataxia and Parkinsons disease (PD) were carried out to assess the frequency of spinocerebellar ataxia (SCA) and to document the distribution of SCA mutations underlying ethnic Chinese in Taiwan. MJD/SCA3 (46%) was the most common autosomal dominant SCA in the Taiwanese cohort, followed by SCA6 (18%) and SCA1 (3%). No expansions of SCA types 2, 10, 12, or dentatorubropallidoluysian atrophy (DRPLA) were detected. The clinical phenotypes of these affected SCA patients were very heterogeneous. All of them showed clinical symptoms of cerebellar ataxia, with or without other associated features. The frequencies of large normal alleles are closely associated with the prevalence of SCA1, SCA2, MJD/SCA3, SCA6, and DRPLA among Taiwanese, Japanese, and Caucasians. Interestingly, abnormal expansions of SCA8 and SCA17 genes were detected in patients with PD. The clinical presentation for these patients is typical of idiopathic PD with the following characteristics: late onset of disease, resting tremor in the limbs, rigidity, bradykinesia, and a good response to levodopa. This study appears to be the first report describing the PD phenotype in association with an expanded allele in the TATA‐binding protein gene and suggests that SCA8 may also be a cause of typical PD.

Dystonia as a presenting sign of spinocerebellar ataxia type 1

We report on a 39‐year‐old man who presented initially with marked blepharospasm, oromandibular dystonia and retrocollis and one year later developed mild ataxia. Our findings suggest that dystonia can be a disabling presenting sign of SCA1 and support the clinical heterogeneity of SCA1, highlighting the importance of considering this entity in patients combining dystonia and cerebellar ataxia.

Spinocerebellar ataxia type 8 larger triplet expansion alters histone modification and induces RNA foci.

BackgroundSpinocerebellar ataxia type 8 (SCA8) involves the expression of an expanded CTG/CAG combined repeats (CR) from opposite strands producing CUG expansion transcripts (ataxin 8 opposite strand, ATXN8OS) and a polyglutamine expansion protein (ataxin 8, ATXN8). The pathogenesis of SCA8 is complex and the spectrum of clinical presentations is broad.ResultsUsing stably induced cell models expressing 0, 23, 88 and 157 CR, we study the role of ATXN8OS transcripts in SCA8 pathogenesis. In the absence of doxycycline, the stable ATXN8OS CR cell lines exhibit low levels of ATXN8OS expression and a repeat length-related increase in staurosporine sensitivity and in the number of annexin positive cells. A repeat length-dependent repression of ATXN8OS expression was also notable. Addition of doxycycline leads to 25~50 times more ATXN8OS RNA expression with a repeat length-dependent increase in fold of ATXN8OS RNA induction. ChIP-PCR assay using anti-dimethyl-histone H3-K9 and anti-acetyl-histone H3-K14 antibodies revealed increased H3-K9 dimethylation and reduced H3-K14 acetylation around the ATXN8OS cDNA gene in 157 CR line. The repeat length-dependent increase in induction fold is probably due to the increased RNA stability as demonstrated by monitoring ATXN8OS RNA decay in cells treated with the transcriptional inhibitor, actinomycin D. In cells stably expressing ATXN8OS, RNA FISH experiments further revealed ribonuclear foci formation in cells carrying expanded 88 and 157 CR.ConclusionThe present study demonstrates that the expanded CUG-repeat tracts are toxic to human cells and may affect ATXN8OS RNA expression and stability through epigenetic and post-transcriptional mechanisms.

Analysis of polyglutamine-coding repeats in the TATA-binding protein in different neurodegenerative diseases

Summary.Trinucleotide repeat (TNR) expansion in the gene for TATA binding protein (TBP) has recently been described as causal for spinocerebellar ataxia type 17. The normal number of repeats has been considered to be 42 or less. An intermediate range with reduced penetrance has been assumed to be 43–47 CAA/CAG repeats. We examined this gene in 30 patients with autosomal-dominant cerebellar ataxia (ADCA), 35 patients with sporadic ataxia, 11 patients with Huntington’s disease (HD), 351 patients with idiopathic Parkinson’s disease (PD), 105 patients with Alzheimer’s disease (AD), and 291 controls with no history of neurodegenerative disease. Three patients (one with sporadic PD and two with AD) carrying more than 42 TNRs in the TBP gene were identified. This reveals that the phenotype associated with CAG/CAA expansion in the TBP gene may be heterogeneous.

The aqueous extract of Glycyrrhiza inflata can upregulate unfolded protein response-mediated chaperones to reduce tau misfolding in cell models of Alzheimer’s disease

Background Alzheimer’s disease (AD) and several neurodegenerative disorders known as tauopathies are characterized by misfolding and aggregation of tau protein. Although several studies have suggested the potential of traditional Chinese medicine (TCM) as treatment for neurodegenerative diseases, the role of TCM in treating AD and tauopathies have not been well explored. Materials and methods Tau protein was coupled to the DsRed fluorophore by fusing a pro-aggregation mutant of repeat domain of tau (ΔK280 tauRD) with DsRed. The ΔK280 tauRD-DsRed fusion gene was then used to generate Tet-On 293 and SH-SY5Y cell clones as platforms to test the efficacy of 39 aqueous extracts of TCM in reducing tau misfolding and in neuroprotection. Results Seven TCM extracts demonstrated a significant reduction in tau misfolding and reactive oxidative species with low cytotoxicity in the ΔK280 tauRD-DsRed 293 cell model. Glycyrrhiza inflata and Panax ginseng also demonstrated the potential to improve neurite outgrowth in the ΔK280 tauRD-DsRed SH-SY5Y neuronal cell model. G. inflata further rescued the upregulation of ERN2 (pro-apoptotic) and downregulation of unfolded-protein-response-mediated chaperones ERP44, DNAJC3, and SERP1 in ΔK280 tauRD-DsRed 293 cells. Conclusion This in vitro study provides evidence that G. inflata may be a novel therapeutic for AD and tauopathies. Future applications of G. inflata on animal models of AD and tauopathies are warranted to corroborate its effect of reducing misfolding and potential disease modification.

Internal Ribosome Entry Segment Activity of ATXN8 Opposite Strand RNA

Spinocerebellar ataxia type 8 (SCA8) involves the expansion of CTG/CAG repeats from the overlapping ataxin 8 opposite strand (ATXN8OS) and ataxin 8 (ATXN8) genes located on chromosome 13q21. Although being transcribed, spliced and polyadenylated in the CTG orientation, ATXN8OS does not itself appear to be protein coding, as only small open reading frames (ORFs) were noted. In the present study we investigated the translation of a novel 102 amino acids containing-ORF in the ATXN8OS RNA. Expression of chimeric construct with an in-frame ORF-EGFP gene demonstrated that ATXN8OS RNA is translatable. Using antiserum raised against ORF, ATXN8OS ORF expression was detected in various human cells including lymphoblastoid, embryonic kidney 293, neuroblastoma IMR-32, SK-N-SH, SH-SY5Y cells and human muscle tissue. The biological role of the ATXN8OS ORF and its connection to SCA8 remains to be determined.

Establishment of spinocerebellar ataxia type 8 transgenic mouse model

factors may play roles in the development of AD and/or VaD. In this study, odd ratios (ORs) and 95% confidence intervals (CIs) for apolipoprotein E (APOE), angiotensin-converting enzyme (ACE) and kallikrein (KLK1) polymorphisms were computed to test their association with the disease by a case–control study and a promoter functional assay. The analysis of genotype or allele frequency distribution of KLK1 −130 GN showed no statistically significant difference between cases and controls. The overall APOE genotype distribution was significantly different between the AD cases and controls (p < 0.0001), with significantly more 3 4 (35.8% versus 16.8%, p = 0.0010) and 4 4 (8.6% versus 0.0%, p = 0.0002) genotypes among AD cases and the association of the 4 allele with AD was evident (p < 0.0001; OR: 3.73; 95% CI: 2.38–5.98). The above difference was not observed between the VaD cases and controls. The risk of AD was also significant for people with ACE DD genotype, D allele or T–D haplotype [OR (95% CI) = 4.29 (1.96–10.23), 1.90 (1.35–2.70) or 2.91 (1.71–5.10), respectively]. The above association between ACE-VaD was also strong (p = 0.0012, 0.0050, 0.0007, respectively). Reporter constructs containing the −240 A or T allele displayed similar transcriptional activity in both HEK-293 and IMR-32 cells. Thus, another putative pathogenic marker that is linked with the Alu D allele might affect the risk of AD and VaD in Taiwan.

Plausible pathogenesis of SCA8 CTG trinucleotide repeats expansion

cells transfected with expanded TBP revealed reduced oxidative tolerance upon t-butylhydroperoxide treatment. The reduced oxidative stress tolerance was also observed using lymphoblastoid cell lines from SCA17 patients. Proteomics analysis on transiently transfected 293 and lymphoblastoid cells with TBP expansion further suggests the involvement of proteins assisting folding and metabolism on the disease pathogenesis. The identified abnormalities in neurodegeneration may be used as a “biomarker” for assessing the efficacy of potential therapeutic strategies for SCAs and other polyglutamine diseases.