DYT1 mutation in a cohort of Taiwanese primary dystonias

A Clinical and Integrated Genetic Study of Isolated and Combined Dystonia in Taiwan

Dystonia is a clinically and genetically heterogeneous movement disorder. However, genetic causes of dystonia remain largely unknown in Asian subjects. To address this, we applied an integrated two-step approach that included gene dosage analysis and a next-generation sequencing panel containing 72 known genes causative for dystonia and related movement disorders to 318 Taiwanese patients with isolated or combined dystonia. Whole-genome sequencing was performed for one multiplex family with no known causative variant. The panel confirmed the genetic diagnosis in 40 probands (12.6%). A genetic diagnosis was more likely with juvenile onset compared with adult onset (24.2% vs 10.8%; P = 0.03) and those with combined features, especially with myoclonus, compared with isolated dystonia (35.3% vs 10.5%; P = 0.004). The most common causative genes were SGCE followed by GCH1, TH, CACNA1B, PRRT2, MR1, CIZ1, PLA2G6, and PRKN. Genetic causes were identified from single cases in TOR1A, TUBB4A, THAP1, ATP1A3, ANO3, GNAL, KMT2B, SLC6A3, ADCY5, CYP27A1, PANK2, C19orf12, and SPG11. The whole-genome sequencing analysis identified a novel intragenic deletion in OPHN1 in a multiplex family with X-linked dystonia and intellectual delay. Our findings delineate the genetic architecture and clinical spectrum of dystonia-causing pathogenic variants in an Asian population.

Investigating DYT1 in a Taiwanese dystonia cohort

BACKGROUND/PURPOSE

A heterozygous three-nucleotide (GAG) in-frame deletion in the TOR1A gene causes the rare disease, dystonia (DYT1), which typically presents as focal limb dystonia during adolescence, then spreads to other limbs. This study investigated the frequency and clinical features of DYT1 in a Taiwanese dystonia cohort.

METHODS

We performed targeted next generation sequencing in 318 patients with primary dystonia. We identified one DYT1 family with various types of dystonia, and we described the clinical presentations observed in this family during a 30-year follow-up. We compared the clinical characteristics to those reported in previous studies on DYT1 from 2000 to 2020.

RESULTS

Among 318 patients, we identified only one DYT1 patient (0.3%) with an autosomal dominant family history of dystonia. The proband was a 43-year-old man that experienced progressive onset of focal lower limb dystonia from age 11 years. The disease spread caudal-rostrally to the upper limbs and cervical muscles. Prominent cervical dystonia was noted during follow-up, which was an atypical presentation of DYT1. Clinical assessments of other family members showed intrafamily variability. The proband's father and an affected sibling demonstrated only mild right-hand writer's cramp. A systematic review of previously reported DTY1 cases showed that Asian patients had a higher frequency of cervical dystonia (44.8%) than groups of Ashkenazi Jews (35%) and Non-Jewish Caucasians (30.5%) (P = 0.04).

CONCLUSION

Our findings revealed that DYT1 is rare in a Taiwanese dystonia cohort. The presentation of marked cervical dystonia could be the main feature of Asian patients with DYT1.

Epidemiology of DYT1 dystonia: Estimating prevalence via genetic ascertainment

Objective

To estimate the prevalence of TOR1A sequence variants associated with DYT1 dystonia.

Methods

We determined the frequency of the common trinucleotide deletion that causes DYT1 in the Genome Aggregation Database and the Penn Medicine Biobank, totaling exomes from over 135,000 individuals. We also evaluated the prevalence of other possible pathogenic variants in this gene and asked whether the D216H polymorphism is linked to a higher diagnostic rate for dystonia independent of the DYT1-causing mutation.

Results

The estimated range of prevalence of the most common pathogenic variant that causes DYT1 is ∼17.6–26.1 carriers per 100,000 individuals. Based on the different data sets used, we predict that there are between 54,366 and 80,891 mutation carriers in the United States, which, due to the reduced penetrance of this variant, would translate into 16,475–24,513 DYT1 patients.

Conclusions

Our data provide a prevalence estimate of the most common DYT1 mutation in the general population. This information is specifically important for those with interest in the development of precision therapeutics for dystonia.

Atypical phenotypes of DYT1 dystonia in three children

DYT-1 dystonia is the most common primary dystonia seen in childhood. It is an autosomal dominantly inherited disorder caused by deletion of a GAG triplet in exon 5 of the DYT1 gene. It characteristically starts in a distal limb during late childhood, subsequently spreads to involve other body regions sparing oromandibular muscles. However, clinical presentation can vary remarkably with respect to age, site of onset and progression. In this study we present three early-onset DYT-1 dystonia patients who are atypical according to age of onset and localization. Dystonia has started at 2, 3 and 7years of age and generalized to involve other limbs in all patients and also oromandibular muscles in one patient. None of them have benefited from medical treatments including L-dopa. All had normal brain MRI scan, a history of normal birth without significant perinatal asphyxia, infection or trauma and all are neurodevelopmentally otherwise normal.

CONCLUSION

In children with dystonia; if brain imaging is unremarkable and when there is no history of CNS disorders such as perinatal asphyxia, infections, drug exposure or trauma; genetic analysis for GAG deletion of DYT-1 gene may be performed even if dystonia starts at a very young age or it spreads to involve oromandibular muscles.

Association of rs1182 polymorphism of the DYT1 gene with primary dystonia in Chinese population

BACKGROUND

The deletion mutation of glutamate codon (GAG) in the TOR1A gene is a major cause of primary generalized dystonia. Recent genetic studies suggest that the rs1182 polymorphism in the same gene may represent a risk factor for primary dystonia. However, this finding has been inconsistent. Furthermore, no data on such an association in a Chinese population have been published.

METHODS

A total of 291 patients with primary dystonia from the Department of Neurology, West China Hospital of Sichuan University were included. From the same region, 294 healthy individuals were recruited as a control group. The SNP was identified by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

In the present study, focal dystonia was the most common presented form. No difference was found in the genotype frequency, minor allele frequencies, and "G" allele frequency between all dystonia patients and controls. No difference was found either, between early- and late-onset dystonia patients, patients with and without a positive family history, patients with pain and without pain, and patients with and without sensory trick. Moreover, no significant differences in the genotype and allele frequencies were found among different dystonia subtypes.

CONCLUSION

No association of the rs1182 of TOR1A with Chinese primary dystonia was found. More studies on such an association involving a larger number of participants, especially from Asian populations, are needed to confirm the present findings.

Clinical features, DYT1 mutation screening and genotype-phenotype correlation in patients with dystonia from Iran

OBJECTIVE

To test Iranian patients with primary torsion dystonia to determine the frequency of 904-906 del GAG mutation in the DYT1 (TOR1A) gene and to investigate the genotype-phenotype association for this disease.

SUBJECTS AND METHODS

Sixty-three patients with primary dystonia were investigated. DNA was extracted from peripheral blood and these samples were subjected to PCR-sequencing for exon 5 of the DYT1 gene.

RESULTS

Of the 63 patients, 10 (15.9%) carried the triplet GAG deletion mutation; this is a high DYT1-positive rate in comparison with other populations and the type of dystonia in this positive group was generalized in all except 1. In our patients, limbs were the most severely involved site at the time of onset and in most cases it developed to generalized form. The majority of DYT1-positive cases showed higher leg onset (5 patients, 62.5%) in comparison with higher arm onset in negative patients (20 patients, 50%). Also, the progression to generalized dystonia in DYT1-positive patients was significantly higher than in DYT1-negative patients. The mean age at onset was 8.6 ± 1.6 years (7-12 years) in DYT1-positive patients, while mean age at onset in patients with no GAG deletion mutation was higher (15.7 ± 11.5 years).

CONCLUSIONS

The DYT1 904-906 del GAG mutation is responsible for some of Iranian dystonia patients, and screening for the DYT1 deletion is significant in cases with the generalized type of primary dystonia. Also, patients with leg or arm onset at a younger age are more likely to be DYT1-positive among primary torsion dystonia cases.

Milestones in dystonia

The last 25 years have seen remarkable advances in our understanding of the genetic etiologies of dystonia, new approaches into dissecting underlying pathophysiology, and independent progress in identifying effective treatments. In this review we highlight some of these advances, especially the genetic findings that have taken us from phenomenological to molecular-based diagnoses. Twenty DYT loci have been designated and 10 genes identified, all based on linkage analyses in families. Hand in hand with these genetic findings, neurophysiological and imaging techniques have been employed that have helped illuminate the similarities and differences among the various etiological dystonia subtypes. This knowledge is just beginning to yield new approaches to treatment including those based on DYT1 animal models. Despite the lag in identifying genetically based therapies, effective treatments, including impressive benefits from deep brain stimulation and botulinum toxin chemodenervation, have marked the last 25 years. The challenge ahead includes continued advancement into understanding dystonia's many underlying causes and associated pathology and using this knowledge to advance treatment including preventing genetic disease expression.

Genetic and clinical features of primary torsion dystonia

Primary torsion dystonia (PTD) is defined as a syndrome in which dystonia is the only clinical sign (except for tremor), and there is no evidence of neuronal degeneration or an acquired cause by history or routine laboratory assessment. Seven different loci have been recognized for PTD but only two of the genes have been identified. In this review we will describe the phenotypes associated with these loci and discuss the responsible gene. This article is part of a Special Issue entitled "Advances in dystonia".

Restoration of motor inhibition through an abnormal premotor-motor connection in dystonia

To clarify the rationale for using rTMS of dorsal premotor cortex (PMd) to treat dystonia, we examined how the motor system reacts to an inhibitory form of rTMS applied to the PMd in healthy subjects and in a group of patients with focal hand dystonia and DYT1 gene carriers. Continuous theta burst transcranial magnetic stimulation (cTBS) with 300 and 600 pulses (cTBS300 and cTBS600) was applied to PMd, and its after-effects were quantified by measuring the amplitude of MEPs evoked by single pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1), short interval intracortical inhibition/facilitation (SICI/ICF) within M1, the third phase of spinal reciprocal inhibition (RI), and writing tests. In addition, in DYT1 gene carriers, the effects of cTBS300 over M1 and PMd on MEPs were studied in separate experiments. In healthy subjects, cTBS300 and cTBS600 over PMd suppressed MEPs for 30 min or more and cTBS600 decreased SICI and RI. In contrast, neither form of cTBS over PMd had any significant effect on MEPs, while cTBS600 increased effectiveness of SICI and RI and improved writing in patients with writer's cramp. NMDYT1 had a normal response to cTBS300 over left PMd. We suggest that the reduced PMd to M1 interaction in dystonic patients is likely to be due to reduced excitability of PMd-M1 connections. The possible therapeutic effects of premotor rTMS may therefore involve indirect effects of PMd on SICI and RI, which this study has shown can be normalised by cTBS.

High frequency of multiexonic deletion of the GCH1 gene in a Taiwanese cohort of dopa-response dystonia

Large deletions in the GCH1 gene have been reported in a minority of cases of dopa-responsive dystonia (DRD). In this study, we performed an extensive clinical and genetic investigation of 22 affected members in eight families. Sequence analysis revealed five different mutations in five families (n = 10); Ser81Pro (novel), Ser76X, Gly203Arg, 249del A, and IVS5 + 3insT. Applying multiple ligation-dependent probe amplification analysis, we detected a large heterozygous deletion of exons 1-3 in the remaining three families (n = 12), which was verified by quantitative real-time PCR analysis. Therefore, the large deletion accounted for 37.5% of the total families and 55% of our DRD population. The deletion appeared to have high penetrance and was associated with multifocal dystonia and adult onset in males. Adult-onset patients were commonly presenting with resting tremor, rigidity, and bradykinesia, indistinguishable from those in Parkinson's disease. In conclusion, a high frequency of multiexonic deletion of GCH1 was identified in the Taiwanese DRD population. By dosage analysis, we were able to detect a mutation in all patients. Our study demonstrates that dosage analysis is necessary for molecular diagnostics in DRD patients of Han Chinese ethnicity.

Clinical feature and DYT1 mutation screening in primary dystonia patients from South-West China

BACKGROUND

Clinical presentation and DYT1 status amongst Chinese patients with primary dystonia have not been well studied.

METHODS

One hundred and twenty patients with primary dystonia from South-West China were studied in a prospective survey for 3.5 years. Severity and the resulting disability were assessed using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). Health related quality of life (HRQL) was measured through the 36-item short-form (SF-36). The Hospital Anxiety and Depression Scale (HADS) was utilized to identify and quantify depression and anxiety. Mutations in the DYT1 exon 5 were screened by direct sequencing.

RESULTS

Cervical dystonia was found to be the most frequent form of focal dystonia and was discovered to occur at an early age. Pain and tremor were the common associated symptoms. Family history was positive in 19.5% of the cases, with a trend of earlier onset. Depression (14.5%) and anxiety (6.6%) were the main HRQL impairments. Multiple linear regression analysis suggested that gender, depression, anxiety and functional disability were amongst the principal determinants of lower HRQL. Only one instance of DYT1 GAG deletion (1.4%) was detected in 71 patients.

CONCLUSION

Our data on a cohort of Chinese patients show some difference from descriptions in other ethnic groups. This includes an earlier age of onset, a lower incidence of depression and female serving as a predictor factor of a HRQL. Similar to other cohorts, DYT1 gene mutations are rare.

High-throughput mutational analysis of TOR1A in primary dystonia

Background

Although the c.904_906delGAG mutation in Exon 5 of TOR1A typically manifests as early-onset generalized dystonia, DYT1 dystonia is genetically and clinically heterogeneous. Recently, another Exon 5 mutation (c.863G>A) has been associated with early-onset generalized dystonia and some ΔGAG mutation carriers present with late-onset focal dystonia. The aim of this study was to identify TOR1A Exon 5 mutations in a large cohort of subjects with mainly non-generalized primary dystonia.

Methods

High resolution melting (HRM) was used to examine the entire TOR1A Exon 5 coding sequence in 1014 subjects with primary dystonia (422 spasmodic dysphonia, 285 cervical dystonia, 67 blepharospasm, 41 writer's cramp, 16 oromandibular dystonia, 38 other primary focal dystonia, 112 segmental dystonia, 16 multifocal dystonia, and 17 generalized dystonia) and 250 controls (150 neurologically normal and 100 with other movement disorders). Diagnostic sensitivity and specificity were evaluated in an additional 8 subjects with known ΔGAG DYT1 dystonia and 88 subjects with ΔGAG-negative dystonia.

Results

HRM of TOR1A Exon 5 showed high (100%) diagnostic sensitivity and specificity. HRM was rapid and economical. HRM reliably differentiated the TOR1A ΔGAG and c.863G>A mutations. Melting curves were normal in 250/250 controls and 1012/1014 subjects with primary dystonia. The two subjects with shifted melting curves were found to harbor the classic ΔGAG deletion: 1) a non-Jewish Caucasian female with childhood-onset multifocal dystonia and 2) an Ashkenazi Jewish female with adolescent-onset spasmodic dysphonia.

Conclusion

First, HRM is an inexpensive, diagnostically sensitive and specific, high-throughput method for mutation discovery. Second, Exon 5 mutations in TOR1A are rarely associated with non-generalized primary dystonia.

DYT1 mutations in early onset primary torsion dystonia and Parkinson disease patients in Chinese populations

Torsion dystonia is an autosomal dominant movement disorder characterized by involuntary, repetitive muscle contractions and twisted postures. The most severe early onset form of dystonia has been linked to mutations in the human DYT1 (TOR1A) gene encoding a protein termed torsinA. Moreover, dystonia and Parkinson disease share the common feature of reduced dopamine neurotransmission in the striatum, so we assumed that mutations in the DYT1 gene might have the same role in cases of early onset primary torsion dystonia (EOPTD) and early onset Parkinson disease (EOPD) that present dystonia. In this present study, 17 patients with EOPTD, 221 patients with EOPD and 164 control subjects were screened for mutations of the DYT1 gene by denaturing high performance liquid chromatography (DHPLC), polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and DNA sequencing. Our results showed that the GAG deletion was identified in 7 EOPTD patients, which results in Glu302del of DYT1 gene. No mutations were found in EOPD patients and control subjects. By carefully reviewing the available literature on studies of sporadic, non-Ashkenazi Jewish populations, the results showed that the prevalence rate of DYT1 mutation was not significantly different (p=0.267) between European (27.3%) and Asian (22.2%) patients with early onset primary torsion dystonia.

TorsinA and DYT1 early-onset dystonia

Early-onset torsion dystonia is a severe generalized form of primary dystonia, with most cases caused by a specific mutation (ΔGAG) in the DYT1 gene encoding torsinA. This mutation is autosomal dominant and is thought to result in reduced torsinA activity. TorsinA is an AAA protein located in the lumen of the endoplasmic reticulum and nuclear envelope of most cells (with high levels in some brain neurons). It is thought to serve as a chaperone protein and/or a link between these membranes and the cytoskeleton. Other sequence variations in DYT1 can affect penetrance of the ΔGAG mutation and may be associated with more common, late-onset focal forms of dystonia. Animal models of DYT1 dystonia are emerging that will allow preclinical evaluation of drugs that can be used to prevent or treat this non-neurodegenerative neurologic disease.

Clinical characterization and evaluation of DYT1 gene in Indian primary dystonia patients

OBJECTIVES

Dystonia is a common movement disorder. The purpose of this study is to examine the relative distribution of the primary dystonia subtypes and identify mutation (s) in the DYT1 gene in Indian patients.

MATERIALS AND METHODS

Primary dystonia patients (n = 178) and controls (n = 63), lacking any symptoms of the disease, were recruited for the study from eastern India. The nucleotide variants in the DYT1 gene were identified by carrying out polymerase chain reaction, single stranded conformation polymorphism, and DNA sequencing.

RESULTS

Unlike other reports, pain and/or tremor was more common in our sporadic patients than in familial cases. Three reported and two novel changes were identified in this gene. The homozygous genotype (G,G) for a missense variant (c.646G > C; Asp216His) was significantly over-represented in the patients compared with controls (P < 0.05). However, the commonly reported 3 bp deletion (904-906delGAG) was not detected.

CONCLUSION

Our results suggest that the DYT1 gene might have a limited role in causation of dystonia in the Indian population.

DYT1 mutations amongst adult primary dystonia patients in Singapore with review of literature comparing East and West

BACKGROUND

Dystonia is a heterogenous group of movement disorders whose clinical spectrum is very wide. At least 13 different genes and gene loci have been reported. While a 3-bp deletion in the DYT1 gene is the most frequent cause of early limb-onset, generalized dystonia, it has also been found in non-generalized forms of sporadic dystonia. An 18-bp deletion in the DYT1 gene has also been reported.

OBJECTIVES

We screened for the 3-bp and 18-bp deletions in the DYT1 gene among our sporadic, adult-onset primary dystonia patients in Singapore. We reviewed the literature to compare the frequency of DYT1 mutation between the East and the West.

METHODS

We screened 54 patients with primary dystonia (focal: n=41; segmental: n=11; multifocal: n=1; generalized: n=1) for the deletions in the DYT1 gene. A careful review of all published literature on DYT1 screening among sporadic, non-familial, non-Ashkenazi Jewish patients was done.

RESULTS

We did not detect any mutations in the exon 5 of the DYT1 gene in any of our patients. The frequency of DYT1 mutation amongst Asians (1.0%) was comparable to the West (1.56%) (p=NS).

CONCLUSIONS

DYT1 mutations are uncommon amongst adult primary dystonia patients in Singapore.