Clinical and genetic evaluation of DYT1 and DYT6 primary dystonia in China

Background: Dystonia is defined as the presence of sustained involuntary muscle contractions, often leading to abnormal posture and movement. DYT1 is caused by a mutation in the TOR1A gene, whilst mutations in THAP1 gene have been identified as responsible for DYT6. The relative frequency and phenotype differences between DYT1 and DYT6 amongst Chinese primary dystonia patients have not been well‐characterized. Patients and methods: One hundred eleven unrelated Chinese patients with primary dystonia were screened for mutations in TOR1A and THAP1 genes, and correlate this with clinical presentation. Exon 5 of TOR1A and all three exons and exon‐intron conjunctions in THAP1 were screened by direct sequencing. Results: Three subjects were found to have the GAG deletion in the TOR1A gene, and two patients were detected with THAP1 gene mutations/variations (c.224A>T, c.449A>C). The overall mutation frequency was 4.5% in this cohort with TOR1A mutations found in 2.7% and THAP1 mutations found in 1.8%. No mutations were detected in the controls composed of 100 normal Chinese subjects. The clinical presentations of the DYT1 cases included onset in the limbs that could progress to the generalized dystonia within several years but without cranial involvement. Whilst in the DYT6 cases, the onset was cranial or cervical and progresses very slowly. Conclusion: The major clinical differences between DYT1 and DYT6 dystonia in China were the cranial involvement in DYT6 and progress to general dystonia within several years in DYT1.     

Heterogeneity in primary dystonia: Lessons from THAP1, GNAL,and TOR1A in Amish‐Mennonites

A founder mutation in the Thanatos‐associated (THAP) domain containing, apoptosis associated protein 1 (THAP1) gene causing primary dystonia was originally described in the Amish‐Mennonites. However, there may be both genotypic and phenotypic heterogeneity of dystonia in this population that may also inform studies in other ethnic groups. Genotyping for THAP1 and for guanine nucleotide binding protein (G protein), α‐activating activity polypeptide, olfactory type (GNAL) mutations and genotype‐phenotype comparisons were performed for 76 individuals of Amish‐Mennonites heritage with primary dystonia. Twenty‐seven individuals had mutations in THAP1—most with the founder indel mutation—but two had different THAP1 mutations, 8 had mutations in GNAL, and 1 had a de novo GAG deletion in torsin 1A (TOR1A) (dystonia 1 [DYT1]). In the primary analysis comparing THAP1 carriers versus all non‐THAP1, non‐GNAL, non‐TOR1A individuals, age at onset was lower in THAP1 carriers (mean age ± standard deviation, 15.5 ± 9.2 years [range, 5‐38 years] vs. 39.2 ± 17.7 years [range, 1‐70 years]; P < 0.001), and THAP1 carriers were more likely to have onset of dystonia in an arm (44.4% vs. 15.0%; P = 0.02) and to have arm involvement (88.9% vs. 22.5%; P < 0.01), leg involvement (51.9% vs. 10.0%; P = 0.01), and jaw/tongue involvement (33.3% vs. 7.5%; P = 0.02) involvement at their final examination. Carriers were less likely to have dystonia restricted to a single site (11.11% in carriers vs. 65.9% in noncarriers; P < 0.01) and were less likely to have dystonia onset in cervical regions (25.9% of THAP1 carriers vs. 52.5% of noncarriers; P = 0.04). Primary dystonia in the Amish‐Mennonites is genetically diverse and includes not only the THAP1 indel founder mutation but also different mutations in THAP1 and GNAL as well as the TOR1A GAG deletion. Phenotype, particularly age at onset combined with final distribution, may be highly specific for the genetic etiology. © 2014 International Parkinson and Movement Disorder Society     

DYT6 dystonia: Mutation screening,phenotype, and response to deep brain stimulation

Mutations in THAP1, a gene encoding a nuclear pro‐apoptotic protein, have been associated with DYT6 dystonia. First reports on the phenotype of DYT6 dystonia show an early onset dystonia with predominant cranio‐cervical and laryngeal involvement. Here we assessed the frequency and phenotype of THAP1 mutation carriers in a large Dutch cohort of adult‐onset (≥26 years) dystonia (n = 388) and early‐onset dystonia (n = 67) patients. We describe the phenotype of DYT6 dystonia patients and their response on GPi DBS. Overall, 3 nonsynonymous heterozygous mutations were detected in the early‐onset group (4.5%). Two DYT6 families were identified, showing a heterozygous phenotype. All patients had segmental or generalized dystonia, often associated with profound oromandibular and laryngeal involvement. No nonsynonymous mutations were found in patients with adult‐onset focal dystonia. Rare synonymous variants were identified in conserved regions of THAP1, two in the adult‐onset cervical dystonia group and one in the control group. Four DYT6 dystonia patients were treated with GPi DBS with moderate to good response on motor function but marginal benefit on speech. © 2010 Movement Disorder Society     

Prevalence of THAP1 sequence variants in German patients with primary dystonia

Primary dystonias are a clinically and genetically heterogeneous group of movement disorders, but only for two of them, i.e., dystonia 1 and dystonia 6, the disease causing gene has been identified. Dystonia 1 is characterized by an early onset and is caused by a mutation in the TOR1A gene. Only recently, mutations in THAP1 have been shown to be the cause of DYT6 dystonia. We analyzed 610 patients with various forms of dystonia for sequence variants in the THAP1 gene by means of high resolution melting to delineate the prevalence of sequence variants and phenotypic variability. We identified seven sequence variants in patients and one sequence variant in a control. The sequence variants were not detected in 537 healthy controls. Four patients present with generalized dystonia with speech involvement of early onset, another three patients suffered exclusively from cervical dystonia of adult onset. These findings suggest that THAP1 sequence variations seem to be associated with different ages of onset and distribution of symptoms. Consequently, the phenotypic spectrum might be broader than previously assumed. © 2010 Movement Disorder Society     

A rare variant in TOR1A exon 5 associated with isolated dystonia in southwestern Chinese

Background: TOR1A has been proposed as an important genetic factor in early‐onset isolated dystonia. Variants located in the 3′ untranslated region of TOR1A are of particular importance because they may influence gene expression, although related studies are limited. The objectives of the present study focused on variants in the TOR1A 3′ untranslated region. Methods: The last exon of TOR1A was sequenced in 229 cases with isolated dystonia and in 210 controls. In addition, 471 controls were tested to determine the frequency of the variants in the 3′ untranslated region. Results: Except for c.904_906delGAG, 3 rare sequence variants (NM_000113.2:c.*454T>A, NM_000113.2:c.860C>A [rs766483672], and NM_000113.2:c.*302T>A [rs563498119]) were found only in the patients. The c.*302T>A variant was located in the conserved region of the human microRNA (hsa‐miR‐494) binding site. A luciferase reporter assay showed that c.*302T>A significantly altered gene expression. Conclusions: Population frequencies, computational analyses, and function experiments in this study implied that c.*302T>A is associated with dystonia. © 2017 International Parkinson and Movement Disorder Society     

Clinical neuroimaging and electrophysiological assessment of three DYT6 dystonia families

The purpose of the study was to delineate clinical and electrophysiological characteristics as well as laryngoscopical and transcranial ultrasound (TCS) findings in THAP1 mutation carriers (MutC). According to recent genetic studies, DYT6 (THAP1) gene mutations are an important cause of primary early‐onset dystonia. In contrast to DYT1 mutations, THAP1 mutations are associated with primary early‐onset segmental or generalised dystonia frequently involving the craniocervical region and the larynx. Blood samples from twelve individuals of three German families with DYT6 positive index cases were obtained to test for THAP1 mutations. Eight THAP1 MutC were identified. Of these, six (three symptomatic and three asymptomatic) THAP1 MutC could be clinically evaluated. Laryngoscopy was performed to evaluate laryngeal dysfunction in patients. Brainstem echogenicity was investigated in all MutC using TCS. Two of the patients had undergone bilateral pallidal DBS. In all three symptomatic MutC, early‐onset laryngeal dystonia was a prominent feature. Laryngeal assessment demonstrated adductor‐type dystonia in all of them. On clinical examination, the three asymptomatic MutC also showed subtle signs of focal or segmental dystonia. TCS revealed increased substantia nigra (SN) hyperechogenicity in all MutC. Intraoperative microelectrode recordings under general anesthesia in two of the patients showed no difference between THAP1 and previously operated DYT1 MutC. The presence of spasmodic dysphonia in patients with young‐onset segmental or generalised dystonia is a hallmark of DYT6 dystonia. SN hyperechogenicity on TCS may represent an endophenotype in these patients. Pallidal DBS in two patients was unsatisfactory. © 2010 Movement Disorder Society     

Homozygous THAP1 mutations as cause of early‐onset generalized dystonia

To identify the underlying genetic cause in a consanguineous family with apparently recessively inherited dystonia, we performed genome‐wide homozygosity mapping. This revealed 2 candidate regions including the THAP1 gene, where heterozygous mutations cause dystonia 6. A homozygous missense mutation in THAP1 (c.95T>A; p.Leu32His) was found in all 3 affected siblings. Symptoms started in childhood in the legs and became generalized within a few years. Three heterozygous mutation carriers were unaffected. Because THAP1 regulates the expression of the DYT1 gene, we used reporter gene assays to show that DYT1 expression was significantly increased for Leu32His. However, this increase was less pronounced than for other THAP1 mutations that cause dystonia in the heterozygous state. Our data suggest that homozygous THAP1 mutations cause dystonia and may be associated with a less severe dysfunction of the encoded protein compared with heterozygous disease‐causing mutations. © 2011 Movement Disorder Society     

Mutation screening of GNAL gene in patients with primary dystonia from Northeast China

BackgroundMutations in GNAL have recently been identified as responsible for primary dystonia, however, GNAL mutations in Chinese patients with primary dystonia are not well characterized.Patients and methodsFifty-nine unrelated patients with cervical onset or cervical involved primary dystonia and 120 neurologically normal controls from Northeast China without mutations of TOR1A and THAP1 were all screened for mutation of GNAL gene.ResultsOne subject with adult-onset generalized dystonia was found have a novel nonsense GNAL mutation (c.284C>T, p.Ser95X). Another subject with adult-onset cervical dystonia was found harbor the c.932-7T>G tentative splice site mutation. Although another seventeen sequence variants were identified in both patients and controls, no disease association was found among these sequence variants.ConclusionsMutations in GNAL gene can cause adult-onset primary dystonia in Chinese patients, and the mutation frequency is 3.4% in cervical onset or cervical involved primary dystonia. This paper identifies the first case of GNAL dystonia in the Chinese population.     

Mutation screening of the DYT6/THAP1 gene in Italy

Mutations in the THAP1 gene on chromosome 8p21‐p22 (DYT6 locus) have been recently reported as causative of autosomal dominant primary torsion dystonia (PTD) in four Amish–Mennonite families and in 12 additional probands of different ancestry. We sequenced the THAP1 gene in 158 patients with DYT1‐negative PTD who had onset of symptoms below 30 years and/or positive family history. One sporadic Greek male patient, aged 57 years, was found to carry a novel heterozygous missense variant in THAP1 exon 3 (p.Cys170Arg), of likely pathogenic significance. This subject first presented with right writer's cramp at age of 10 years and, subsequently, developed left arm dystonia and an extremely severe left laterocollis, without further spreading to other body districts. Our findings expand the genotypic spectrum of THAP1 and strengthen the association with upper body involvement, including the cranial and cervical districts that are usually spared in DYT1‐PTD. © 2009 Movement Disorder Society     

Intrafamilial variability of the primary dystonia DYT6 phenotype caused by p.Cys5Trp mutation in THAP1 gene

Mutations localized in THAP1 gene, locus 18p11.21 have been reported as causative of primary dystonia type 6 (DYT6). Disease which is characterized mainly by focal dystonia, frequently involving the craniocervical region, however associated also with early-onset generalized dystonia and spasmodic dysphonia. Here we report a novel mutation in the THAP1 gene identified in a Polish family with DYT6 phenotype – the c.15C > G substitution in exon 1 introducing the missense mutation p.Cys5Trp within the N-terminal THAP domain. The mutation was described in two generations, in patients showing a broad spectrum of focal and generalized dystonia symptoms of variable onset. Our results indicate that certain mutations in the THAP1 gene may lead to primary dystonia with remarkable intrafamilial clinical variability.     

DRD1 rare variants associated with tardive-like dystonia: A pilot pathway sequencing study in dystonia

The dystonias are a clinical heterogeneous group with a complex genetic background. To gain more insight in genetic risk factors in dystonia we used a pathway sequence approach in patients with an extreme dystonia phenotype (n = 26). We assessed all coding and non-coding variants in candidate genes in D1-like subclass of dopamine receptor genes (DRD1, DRD5) and the synaptic vesicle pathway linked to torsinA (TOR1A, STON2, SNAPIN, KLC1 and THAP1), spanning 96 Kb.Two rare missense variants in DRD1 were found: c.68G>A(p.Arg23His) in the screening group and c.776C>A(p.Ser259Tyr) in an additional screen of 15 selected dystonia patients. Genetic burden analysis of DRD1 rare variants in patients (4.8%) versus European American controls from ESP (0.72%) reveals an OR 5.35 (95% CI 1.29–23.1). No rare missense SNVs in the synaptic vesicle pathway were found. Sequencing of TOR1A showed variant enrichment in haplotype 2, possibly accountable for contradictive results in previous association studies. Two new rare SNVs were detected in THAP1, including a nonsense mutation (p.Gln167Ter) and a splice site variant (c.72-1G>A). Screening for rare SNV of candidate pathways in a phenotype extreme population appears to be a promising alternative method to identify genetic risk factors in complex disorders like primary torsion dystonia. These findings indicate a role for rare genetic variation in dopamine processing genes in dystonia pathophysiology.     

Four novel mutations in the GCH1 gene of Chinese patients with dopa‐responsive dystonia

Mutation detection in the guanosine triphosphate cyclohydrolase I gene (GCH1) was performed from 4 female patients with dopa‐responsive dystonia (DRD). DNA sequencing revealed the presence of four novel mutations including c.2T>C(M1T), c.239G>A(S80N), c.245T>C(L82P), and IVS5+3 del AAGT. These four mutations were not found in 100 genetically unrelated healthy controls with the same ethnic background band. In all 3 childhood‐onset patients, DRD started in the legs, and missense mutations were located in the coding region of GCH1. Deletion mutation in the fifth exon–intron boundary of GCH1 was detected in the adult‐onset patient. Although the data presented here do not provide sufficient evidence to establish a genotype–phenotype correlation of DRD, it is important to know the clinic features and genetic defects of DRD patients, which will help prenatal diagnosis, early diagnosis, evaluate the prognosis, and facilitate causal therapy with levodopa. © 2010 Movement Disorder Society     

Screening of Brazilian families with primary dystonia reveals a novel THAP1 mutation and a de novo TOR1A GAG deletion

The TOR1A and THAP1 genes were screened for mutations in a cohort of 21 Brazilian patients with Primary torsion dystonia (PTD). We identified a de novo delGAG mutation in the TOR1A gene in a patient with a typical DYT1 phenotype and a novel c.1A > G (p.Met1?) mutation in THAP1 in a patient with early onset generalized dystonia with speech involvement. Mutations in these two known PTD genes, TOR1A and THAP1, are responsible for about 10% of the PTD cases in our Brazilian cohort suggesting genetic heterogeneity and supporting the role of other genes in PTD. © 2010 Movement Disorder Society     

Lower limb involvement in adult‐onset primary dystonia: frequency and clinical features

Background and purpose: Despite the growing number of reports describing adult‐onset primary lower limb dystonia (LLD) this entity has never been systematically evaluated in the general population of patients with primary adult‐onset dystonia. Methods: From outpatients with adult‐onset primary dystonia attending nine Italian University centres for movement disorders we consecutively recruited 579 patients to undergo a standardized clinical evaluation. Results: Of the 579 patients assessed, 11 (1.9%) (8 women, 3 men) had LLD, either alone (n = 4, 0.7%) or as part of a segmental/multifocal dystonia (n = 7, 1.2%). The age at onset of LLD (47.9 ± 17 years) was significantly lower than the age at onset of cranial dystonias (57.9 ± 10.7 years for blepharospasm, and 58.9 ± 11.8 years for oromandibular dystonia) but similar to that of all the other adult‐onset primary dystonias. The lower limb was either the site of dystonia onset (36.4%) or the site of dystonia spread (63.6%). In patients in whom LLD was a site of spread, dystonia seemed to spread following a somatotopic distribution. Only one patient reported a recent trauma involving the lower limb whereas 36.4% of the patients reported pain at the site of LLD. Only 64% of our patients needed treatment for LLD, and similarly to previously reported cases, the most frequently tried treatments was botulinum toxin and trihexyphenidyl. Conclusion: The lower limb is an uncommon but possible topographical site of dystonia in adulthood that should be kept in consideration during clinical evaluation.     

Blepharospasm and limb dystonia caused by Mohr‐Tranebjaerg syndrome with a novel splice‐site mutation in the deafness/dystonia peptide gene

Mohr‐Tranebjaerg syndrome (MTS) is an X‐linked disorder characterized by childhood‐onset progressive deafness, dystonia, spasticity, mental deterioration, and blindness. It is due to mutations in the deafness/dystonia peptide (DDP1) gene. We describe a sporadic 42‐year‐old man with MTS presenting with postlingual deafness, adult‐onset progressive dystonia with marked arm tremor, mild spasticity of the legs, and visual disturbance due to a novel mutation (g to a transition at the invariant gt of the 5′ splice donor site of exon 1) in the DDP1 gene. This case, and a review of previously reported cases, highlights a variety of potential diagnostic pitfalls in this condition. © 2007 Movement Disorder Society     

Epileptic encephalopathy with features of rapid‐onset dystonia Parkinsonism and alternating hemiplegia of childhood: a novel combination phenotype associated with ATP1A3 mutation

Mutations in ATP1A3 have been found to cause rapid‐onset dystonia Parkinsonism, alternating hemiplegia of childhood, epileptic encephalopathy and other syndromes. We report a four‐year, nine‐month‐old boy with episodes of frequent and recurrent status epilepticus, who first began having generalized tonic‐clonic seizures at four months of age. Development was normal until the age of four months, and markedly slowed down after the onset of seizures. Between the age of seven months and two and a half years, the patient had recurrent attacks of unilateral and bilateral hemiplegia. At the age of 21 months, after a febrile illness with status epilepticus, he regressed and developed continuous severe dystonia and bradykinesia with superimposed intermittent painful dystonic spasms. Extensive neurological and genetic workup revealed a de novo p.V589F ATP1A3 mutation (NM_152296.5:c.1765G>T, NC_000019.9:g.42482344C>A). This is a novel mutation associated with a novel phenotype that shares features with epileptic encephalopathy, alternating hemiplegia of childhood, and rapid‐onset dystonia Parkinsonism.