A novel missense mutation in GTP cyclohydrolase I (GCH1) gene causes dopa‐responsive dystonia in Chinese Han population

Background: Dopa‐responsive dystonia has been shown to be caused by a number of different mutations in the GCH1 gene. Up to now, only several genetic studies of Chinese patients with Dopa‐responsive dystonia (DRD) have been reported. Methods: We performed a genetic analysis by amplifying the entire coding region of GCH1 gene and direct sequencing in four DRD families from mainland China. Results: A novel missense mutation, Gly155Ser, has been identified in a sporadic case from a consanguineous marriage family. Furthermore, two known mutations, Met137Arg and Gly203Arg, have also been detected in the other families. Conclusions: A novel missense mutation in the GCH1 gene can be associated with DRD. Our findings further expanded the mutational spectrum of GCH1 gene associated with DRD.     

Utility of MLPA in deletion analysis of GCH1 in dopa-responsive dystonia

We applied multiple ligation-dependent probe amplification (MLPA) to patients from three families with characteristic dopa-responsive dystonia (DRD) but no base change in the gene GCH1. We found a complete deletion of GCH1 in affected members of family 1, and partial deletions in affected individuals of family 2 (exons 4–6) and of family 3 (exons 2–6). The findings were confirmed by quantitative real-time PCR. Our investigations demonstrate the utility of MLPA for routine deletion analysis of GCH1 in DRD patients with no sequence changes in this gene.An erratum to this article can be found at     

Novel GCH1 mutation in a Brazilian family with dopa‐responsive dystonia

Dopa responsive Dystonia (DRD) was first described in 1971 and typically begins at childhood with gait dysfunction caused by foot dystonia progressing to affect other extremities. There is marked diurnal fluctuation and sustained improvement of symptoms with low dose levodopa therapy. Heterozygous mutation of the gene GCH1 has been shown to cause DRD. We studied GCH1 in nine patients with DRD from six families of Federal University of Minas Gerais Movement Disorders Clinic. We identified three mutations; two affected siblings carried a novel T209P mutation and two siblings from another family were compound heterozygous carriers of Met211Val and Lys224Arg mutations. To our knowledge this is the first report of GCH1 mutations underlying DRD in patients from Brazil. © 2007 Movement Disorder Society     

A novel tyrosine hydroxylase variant in a group of Chinese patients with dopa-responsive dystonia

Dopa-responsive dystonia (DRD) comprises a heterogeneous group of movement disorders. A limited number of studies of Chinese patients with DRD have been reported. In the present study, we investigated the clinical and genetic features of 12 Chinese DRD families. Point mutation analysis of the GTP-cyclohydrolase I (GCH1), tyrosine hydroxylase (TH) and sepiapterin reductase (SPR) genes was conducted by direct sequencing. In addition, multiplex ligation-dependent probe amplification targeting GCH1 and TH was performed in “mutation-free” patients. Three reported mutations (IVS2-2A>G, c.293C>T, c.550C>T) were detected in GCH1, whereas two compound heterozygous variants were identified in TH, one of which was novel (c.1083C>A). Furthermore, this novel variant was not detected in any of the 250 ethnicity-matched, healthy controls. No exon deletions or duplicate mutations in the two genes were found in patients with DRD. No mutation in SPR was found. In addition, one patient with the IVS2-2A>G mutation in GCH1 showed signs of Parkinsonism. In conclusion, we here identified a novel heterozygous variant in TH (c.1083C>A). It is important to perform routine screening of GCH1 and TH for patients with DRD. While for patients with Parkinsonism, GCH1 mutation analysis should be performed after screening of genes like PARKIN, PARK7 (DJ-1) and PINK1.     

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     

Novel non‐sense GCH1 mutation in a South African family diagnosed with dopa‐responsive dystonia

Background: Dopa‐responsive dystonia (DRD), a movement disorder characterized by onset in early childhood and a dramatic response to low doses of levodopa, has been shown to be caused by a number of different mutations in the GCH1 gene. Methods: We identified a South African family which presented with DRD in three family members. Polymerase chain reaction (PCR) primers were designed to span all six exons of GCH1 and the PCR products were screened for pathogenic mutations using direct sequencing. Results: A novel non‐sense mutation (c.233delT; p.I78fsX79) was identified in the DRD patients, which would produce a markedly truncated protein of only 78 amino acids. This mutation was also present in a number of asymptomatic family members. Conclusions: A novel non‐sense mutation in the GCH1 gene can be associated with DRD and reduced penetrance in South African patients.     

Frequency of GCH1 deletions in Dopa-responsive dystonia

We performed a systematic study on the frequency of point mutations and deletions of the gene GCH1 in dopa-responsive dystonia (DRD). A total of 136 dystonia patients were studied. Fifty of these had a sustained response to oral L-Dopa therapy (group 1: definite diagnosis of DRD), whereas the response to L-Dopa was incomplete or not tested in 86 patients (group 2: possible diagnosis of DRD). We found a GCH1 point mutation in 27 patients of group 1 (54%) and in four patients of group 2 (5%). Of these, nine single and one double mutation have not been described before. GCH1 deletions were detected in four patients of group 1 (8%) and in one patient of group 2 (1%). Among GCH1 point-mutation-negative patients with a definite diagnosis of DRD (group 1), the frequency of GCH1 deletions was 17% (4/23). We conclude that GCH1 deletion analysis should be incorporated into the routine molecular diagnosis of all patients with DRD with a sustained response to L-Dopa.     

Utility of MLPA in deletion analysis of <Emphasis Type="Italic">GCH1</Emphasis> in dopa-responsive dystonia

We applied multiple ligation-dependent probe amplification (MLPA) to patients from three families with characteristic dopa-responsive dystonia (DRD) but no base change in the gene GCH1. We found a complete deletion of GCH1 in affected members of family 1, and partial deletions in affected individuals of family 2 (exons 4-6) and of family 3 (exons 2-6). The findings were confirmed by quantitative real-time PCR. Our investigations demonstrate the utility of MLPA for routine deletion analysis of GCH1 in DRD patients with no sequence changes in this gene.     

“Jerky” dystonia in children: Spectrum of phenotypes and genetic testing

Hyperkinetic dystonia is characterized by phasic, tremulous, and “jerky” movements in addition to twisting postures. We studied longitudinally 23 index patients with hyperkinetic dystonia from a quaternary pediatric movement disorder clinic in Ireland. Four clinical categories emerged: (1) Eight patients were diagnosed with myoclonus‐dystonia, of whom seven carried heterozygous epsilon sarcoglycan (SGCE) mutations, including a novel deletion of exon 10. Gait disorder, unsteadiness, or frequent falls before 18 months were detected in all SGCE mutation carriers, whereas the typical neck‐predominant presentation developed only years later. (2) One patient classified as benign hereditary chorea, because jerks were choreiform and continuous rather than action‐induced, carried a heterozygous stop mutation of the TITF‐1 gene (Y114X, exon 2). (3) Three mutation‐negative patients were grouped as “myoclonic dystonia” with jerks only in the body regions affected by dystonia. (4) Eleven patients presented with a novel combination of dystonia and low amplitude poly‐mini myoclonus of the upper limbs and pectoral muscles (D‐PMM). In early childhood up to 3 years of age, an initial presentation with predominant gait impairment with only subtle jerks should prompt consideration of SGCE mutation analysis in addition to testing for DYT1 mutations. A causative gene for D‐PMM remains to be identified. © 2008 Movement Disorder Society     

Dopa-responsive dystonia due to a large deletion in the GTP cyclohydrolase I gene

Although it is assumed that most patients with autosomal dominant dopa-responsive dystonia (DRD) have a GTP cyclohydrolase I dysfunction, conventional genomic DNA sequencing of the gene (GCH1) coding for this enzyme fails to reveal any mutations in about 40% of DRD patients, which makes molecular genetic diagnosis difficult. We found a large heterozygous GCH1 deletion, which cannot be detected by the usual genomic DNA sequence analysis, in a three-generation DRD family and conclude that a large genomic deletion in GCH1 may account for some "mutation-negative" patients with dominantly inherited DRD.     

A new mutation of GCH1 in triplets family with dopa‐responsive dystonia

Background: Dopa‐responsive dystonia (DRD) is associated with mutations of the GCH1. We first report four female siblings with DRD from one family, including three monozygotic triplets patients clinically and genetically. Methods: We performed GCH1 analysis by direct sequencing of PCR product amplified with primers designed to cover the entire exons of GCH1 in those four patients and their mother. Results: In all four patients with DRD, a new frameshift mutation (c.729delG; p.A190fsX191) was identified in the exon 5 of GCH1. Conclusions: The frameshift mutation results in truncated GCH1 protein which is suspected to result in loss of function of the catalytic GTP‐cyclohydrol domain.     

Mutations of <Emphasis Type="Italic">GCH1</Emphasis> in Dopa-responsive dystonia

Summary. Dopa responsive dystonia (DRD) is an autosomal dominant dystonia caused by mutations in the gene GCH1 in about 50% of cases. GCH1 codes for GTP cyclohydrolase I, a rate limiting enzyme in the synthesis of tetrahydrobiobterin (BH₄) from GTP. There is reduced penetrance and pronounced variation in expressivity of GCH1 mutations in families with DRD. Correlations between given mutations in GCH1 and phenotypes cannot be established. Mutations in GCH1 appear to function as dominant-negatives but the exact mechanism remains unclear. Additional open questions in DRD include the molecular mechanisms resulting in highly variable expressivity of symptoms and the more likely occurrence of symptoms in a female than in a male carrier of a GCH1 mutation. Received February 9, 2001; accepted March 15, 2001     

Novel GCH-1 mutations and unusual long-lasting dyskinesias in Korean families with dopa-responsive dystonia

ObjectiveTo describe the long-term follow-up data of Korean patients with GTP cyclohydrolase (GTPCH) I deficient dopa-responsive dystonia (DRD) with novel mutations and unusual long-lasting dyskinesias.MethodsClinical features and genetic testing results of GCH1 from 19 patients that included 4 families who have been followed-up for up to 25 years were analyzed.ResultsGCH1 mutations were confirmed in all our symptomatic subjects including 3 novel point mutations. All the subjects except for one family had typical manifestations of autosomal dominant GTPCH-I deficient DRD including early childhood onset dystonia predominantly in the legs, marked diurnal variation, intact cognition, no other systemic symptoms, and excellent sustained response to levodopa. The one family who was the exception had two gene positive members of DRD and one with dopa-unresponsive cervical dystonia with negative GCH1 mutation. One family and a sporadic case had been reported as gene negative in a previous study, but they typically had preserved dopamine transporter binding and low neopterin levels in cerebrospinal fluids; thus, GCH-1 mutation had been highly suspected, which was now confirmed by repeating the genetic testing this time. An early childhood-onset patient developed choreiform dyskinesias right after administration of levodopa. The dyskinesia had lasted for more than 4 years regardless of the levodopa dosages and then subsided while maintaining levodopa.ConclusionThis report emphasizes the usefulness of the neopterin level in cerebrospinal fluids and dopamine transporter imaging in the differential diagnosis of DRD syndromes and a possible mechanism of levodopa-induced-dyskinesia in early childhood onset case.     

Severe dystonic encephalopathy without hyperphenylalaninemia associated with an 18‐bp deletion within the proximal GCH1 promoter

In a recent GCH1 mutation screen, an 18‐bp deletion was identified within the proximal promoter in two patients with early‐onset Parkinson's disease. The mutation removes cAMP response element critical for adequate GTP cyclohydrolase I activity in selected cell types, including dopaminergic neurons, but its biological significance was unclear as it was also detected in one control individual. We present an 11‐year‐old boy with infantile‐onset severe dystonic encephalopathy without hyperphenylalaninemia whom we found compound heterozygous for the same promoter GCH1 deletion and another common missense mutation associated with classical dopa‐responsive dystonia. Extensive diagnostic work up excluded other causes of dystonia, and comprehensive mutation scan did not reveal any additional GCH1 sequence variations, supporting the association between the promoter deletion and disease phenotype. © 2010 Movement Disorder Society     

Defining the Epsilon‐Sarcoglycan (SGCE) Gene Phenotypic Signature in Myoclonus‐Dystonia: A Reappraisal of Genetic Testing Criteria

Mutations or exon deletions of the epsilon‐sarcoglycan (SGCE) gene cause myoclonus‐dystonia (M‐D), but a subset of M‐D patients are mutation‐negative and the sensitivity and specificity of current genetic testing criteria are unknown. We screened 46 newly enrolled M‐D patients for SGCE mutations and deletions; moreover, 24 subjects previously testing negative for SGCE mutations underwent gene dosage analysis. In our combined cohorts, we calculated sensitivity, specificity, positive and negative predictive values, and area under the curve of 2 published sets of M‐D diagnostic criteria. A stepwise logistic regression was used to assess which patients' characteristics best discriminated mutation carriers and to calculate a new mutation predictive score (“new score”), which we validated in previously published cohorts. Nine of 46 (19.5%) patients of the new cohort carried SCGE mutations, including 5 novel point mutations and 1 whole‐gene deletion; in the old cohort, 1 patient with a complex phenotype carried a 5.9‐Mb deletion encompassing SGCE. Current diagnostic criteria had a poor ability to discriminate SGCE‐positive from SGCE‐negative patients in our cohort; conversely, age of onset, especially if associated with psychiatric features (as included in the new score), showed the best discriminatory power to individuate SGCE mutation carriers, both in our cohort and in the validation cohort. Our results suggest that young age at onset of motor symptoms, especially in association with psychiatric disturbance, are strongly predictive for SGCE positivity. We suggest performing gene dosage analysis by multiple ligation‐dependent probe amplification (MLPA) to individuate large SGCE deletions that can be responsible for complex phenotypes. © 2013 Movement Disorder Society     

Phenocopies in a large GCH1 mutation positive family with dopa responsive dystonia: confusing the picture?

BACKGROUND: Dopa responsive dystonia (DRD) is a disorder characterised by childhood onset dystonia but a wide range of clinical presentations has now been described. OBJECTIVE: To study a large Canadian family with presumed DRD. METHODS: The clinical features of the family were collected before molecular genetic mutational analysis. RESULTS: All nine individuals in whom a clinical diagnosis of DRD was definite or probable were heterozygous for a GCH1 gene deletion. However, eight of nine possibly clinically affected members did not carry the GCH1 mutation. CONCLUSIONS: Great care must be taken in diagnosing DRD even in families with the classic phenotype, because of potential phenocopies of the disease.     

Dopa-responsive dystonia and Tourette syndrome in a large Danish family

BACKGROUND: Guanosine triphosphate cyclohydrolase I (GTPCH) catalyzes the first step in the synthesis of tetrahydrobiopterin (BH4). Autosomal dominantly inherited defects in the GTPCH gene (GCH1) cause a form of dystonia that is responsive to treatment with levodopa (dopa-responsive dystonia [DRD]). OBJECTIVE: To investigate molecular and clinical aspects of DRD in a large Danish family. METHODS: For analysis of the GCH1 gene, a mutation-scanning method based on denaturing gradient gel electrophoresis (DGGE) was used. A novel mutation, X251R, was identified in the GCH1 gene of 2 distantly related Danish patients with DRD, one of whom also had Tourette syndrome (TS). Thirty-five additional family members were investigated for this mutation, and 16 of them underwent clinical neurological examination. RESULTS: A total of 18 patients were heterozygous for the X251R allele, 16 of whom had neurological complaints spanning from very mild parkinsonism to severe invalidism due to dystonia. Of 13 symptomatic heterozygotes who had been neurologically examined, 10 had signs of dystonia or parkinsonism. Sixteen of the heterozygotes were treated with levodopa, and 13 reported a treatment benefit. Three of the symptomatic heterozygotes had signs of TS. CONCLUSIONS: This study confirms the large variability in DRD symptoms and emphasizes the usefulness of molecular analysis for diagnosis and treatment of DRD. The presence of TS is suggested to be coincidental, though the development of TS-like symptoms due to mutations in GCH1 cannot be excluded.     

Novel mutations in the guanosine triphosphate cyclohydrolase 1 gene associated with DYT5 dystonia

OBJECTIVES: To better understand the relationship between mutation of the guanosine triphosphate cyclohydrolase I (GCH1) gene and the etiology of DYT5 dystonia and to accumulate data on the mutation in the Japanese population for genetic diagnosis of the disease. SETTING: Japanese population. Patients Eight Japanese patients with suspected DYT5 dystonia were analyzed. Intervention Direct genomic sequencing of 6 exons of GCH1 was performed. MAIN OUTCOME MEASURES: For patients who did not exhibit any abnormality in the sequence analysis, the possibility of exon deletions was examined. In cases for which cerebrospinal fluid was available, the concentrations of neopterin and biopterin were measured as an index of GCH1 enzyme activity. RESULTS: In 2 patients, we found a new T106I mutation in exon 1 of GCH1, a position involved in the helix-turn-helix structure of the enzyme. In the third patient, we found a new mutation (a 15-base pair nucleotide deletion) in exon 5 that may cause a frameshift involving the active site. In the fourth patient, we detected a known nucleotide G>A substitution in the splice site of intron 5, which has been reported to produce exon 5-skipped messenger RNA. The concentrations of both neopterin and biopterin in the cerebrospinal fluid of the third and fourth patients were markedly lower than the normal range, indicating that the GCH1 enzyme was functionally abnormal in these mutations. Gene dosage analysis showed that the fifth patient had a deletion of both exon 3 and exon 4, whereas the sixth patient had a deletion of exon 3. CONCLUSIONS: We found several novel, as well as known, GCH1 mutations in Japanese patients with DYT5 dystonia. In some of them, the GCH1 enzyme activity was proved to be impaired.     

Occurrence of GCH1 gene mutations in a group of Indian dystonia patients

The aim of this study is to examine the role of GCH1 among Indians affected with dopa responsive dystonia (DRD) and early onset Parkinson’s disease (EOPD). The patients (n?=?76 including 19 DRD and 36 EOPD) and controls (n?=?138) were screened for variants in GCH1 by PCR amplification of exons, splice junctions and 1?kb upstream region followed by SSCP and DNA sequencing. Four novel variants (p.Met1Val, p.Val204_205del, IVS3+68A>G, and IVS5?6T>G) were identified in 10 patients but not in the controls. In addition to two nonsynonymous changes, identified in four DRD patients in heterozygous condition, one intronic variant (IVS5?6T>G) could be linked to pathogenesis of the disease since it has the potential of altering the splice site as assessed by in silico analysis. Patients carrying different nonsynonymous variants had remarkable variation in clinical phenotype. Consistent with earlier reports, severity of clinical phenotype and the age of onset varied among family members harboring the same mutation. No mutation was detected in the EOPD patients. Three novel mutations in GCH1 gene have been found and are shown to be associated with variable clinical phenotypes mostly within the spectrum of DRD. The mutations identified represent 15.79% (3/19) of east Indian DRD patient cohort.