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.     

GCH1 mutation and clinical study of Chinese patients with dopa‐responsive dystonia

Dopa‐responsive dystonia (DRD) is typically caused by heterozygous mutations in GTP cyclohydrolase 1 gene (GCH1). Our aim was to investigate the clinical and genetic features of Chinese DRD patients. We analyzed a cohort of Chinese DRD patients' clinical data. Mutation of the GCH1 gene was screened by direct sequencing. Additionally, multiplex ligation‐dependent probe amplification (MLPA) assay targeting the GCH1 and the TH gene to evaluate large exon deletion or duplicate mutation of the genes were performed in point mutation‐negative patients. Ten sporadic DRD patients and two pedigrees including six patients were included in the study. The onset age ranged from 3 to 15 years old. All patients initially presented with walking problems due to lower limb dystonia. The delay between onset and diagnosis ranged from 1 to 42 years old. The symptoms were completely or near‐completely abolished with low dose levodopa treatment (dosages ranged from 25 mg to 400 mg/day). Direct sequencing in 14 patients found two known mutations (Gly203Arg in exon 5 in four unrelated patients and Met102Lys in exon 1 in one patient) and one new mutation (Thr186Ile mutation in exon 5 in two unrelated pedigrees). A heterozygous exon 2 deletion in the GCH1 gene was found in one of three point mutation‐negative patients by MLPA analysis. Our clinical findings in DRD patients were consistent with other studies. GCH1 gene mutations were quite common in Chinese patients. MPLA should be performed in routine deletion analysis of GCH1 in point mutation‐negative DRD patients. © 2010 Movement Disorder Society     

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.     

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.     

多巴反应性肌张力障碍患者的GCH1基因突变检测

目的分析多巴反应性肌张力障碍(dopa responsive dystonia,DRD)患者的GCH1基因突变。方法我们抽取21例来自医院门诊及住院的散发型多巴反应性肌张力障碍患者的肘静脉血,并提取外周血全基因组DNA。Primer3设计GCH1基因6个外显子的引物,PCR扩增GCH1基因的外显子及周边部分内含子序列,并对PCR产物进行测序。测序结果与正常序列进行比对,发现碱基变异后进行序列分析以确定是否多态。结果成功扩增21位DRD患者GCH1基因的6个外显子。经过分析,GCH1基因外显子序列未发现基因突变。仅在4个患者的1号外显子发现1个单核苷酸多态(SNP)c.68CT,该SNP没有产生氨基酸的改变。结论本地区多巴反应性肌张力障碍患者未发现GCH1基因突变,DRD患者可能存在其他致病基因。GCH1基因突变检测目前仍不能作为早期诊断的依据。     

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 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     

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.     

Wide expressivity variation and high but no gender‐related penetrance in two dopa‐responsive dystonia families with a novel GCH‐I mutation

We describe the clinical and molecular correlates in two Italian families with dopa‐responsive dystonia (DRD) and the same novel mutation of GTP‐cyclohydrolase I (GCH‐I) gene. Thirty‐five subjects were examined and the genotype correlated to phenotype. Childhood onset foot dystonia is present in 7 subjects currently under the age of 40. In 1 patient bilateral foot dystonia was evident at birth suggesting that dystonia may be active as early as in utero. In another patient, dystonia spontaneously remitted in adolescence, to relapse 8 years later, as writer's cramp. Dystonia and parkinsonian signs are present in 5 other patients. In 2 subjects an isolated parkinsonism started over the age of 45. A 5‐base pair insertion at codon 242 within exon 6 of GTP‐cyclohydrolase I (GCH‐I) gene that shifts the reading frame and results in a premature stop at codon 247 with truncation of the polypeptide has been detected in 21 subjects. Considering dystonia and parkinsonism the overall penetrance is 0.71 and not significantly different in men (0.69) and women (0.75). Genealogical studies seem to exclude that these families are related but haplotype analysis suggests a single founder. Our findings in subjects with the same mutation indicate a wide intrafamilial variation in expressivity and high penetrance in DRD but do not confirm the reported influence of gender on GCH‐I gene mutation penetrance. © 2004 Movement Disorder Society     

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.     

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.     

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.     

A novel missense mutation of the GTP cyclohydrolase I gene in a Korean family with hereditary progressive dystonia/dopa-responsive dystonia

Hereditary progressive dystonia with marked diurnal fluctuation/dopa-responsive dystonia (HPD/DRD) shows the considerable heterogeneity of clinical phenotypic expression and a dramatic sustained response to levodopa. The autosomal dominant HPD/DRD is caused by mutations in the gene coding GTP cyclohydrolase I (GCH I), the enzyme that catalyzes the first step in the biosynthesis of tetrahydrobiopterin. Previous studies suggested that normal [18F]Dopa positron emission tomography or [123I]beta-CIT single-photon emission computed tomography (SPECT) imaging, indicating intact structural integrity of nigrostriatal neurons, may be useful for differentiating HPD/DRD from clinically similar conditions such as juvenile Parkinson's disease with dystonia that have a considerably poorer prognosis. We here report a Korean family affected with HPD/DRD due to a novel missense mutation of the GCH I gene (T-->G mutation in exon 2), Met 137 Arg, which may change the conformation of the binding site of GCH I. The clinical features are considerably variable within the family. We documented normal striatal uptake of [123I]IPT, a dopamine transporter ligand with fast washout kinetics, in our patients by using SPECT. This method can be helpful in diagnosing HPD/DRD in uncertain cases.     

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.     

Dopa-responsive dystonia is induced by a dominant-negative mechanism

Dopa-responsive dystonia (DRD) is induced by a deficiency of GTP cyclohydrolase I (GCH) and has a postulated autosomal dominant inheritance with a low penetrance. G201E is a dominant DRD mutation. Recombinant G201E mutant protein possessed very low enzyme activity. When G201E was expressed in eukaryotic cells, only a small amount of GCH protein could be detected. In baby hamster kidney cells, G201E protein was synthesized normally but was degraded rapidly in pulse-chase experiments. More interestingly, G201E dramatically decreased the level of wild-type protein and GCH activity in cotransfection studies. Therefore, G201E exerts a dominant-negative effect on the wild-type protein, probably going through an interaction between them. We also showed that L79P but not R249S (a recessive DRD mutation) had a dominant-negative effect. Through the dominant-negative mechanism, a single mutation could decrease GCH activity to less than 50% of normal. This study not only explains the inheritance of DRD but also increases the understanding of genetic diseases associated with multiple subunit proteins.     

Striatal biopterin and tyrosine hydroxylase protein reduction in dopa-responsive dystonia.

OBJECTIVE: To determine the mechanism leading to striatal dopamine (DA) loss in dopa-responsive dystonia (DRD). BACKGROUND: Although mutations in the gene GCH1, coding for the tetrahydrobiopterin (BH4) biosynthetic enzyme guanosine triphosphate-cyclohydrolase I, have been identified in some patients with DRD, the actual status of brain BH4 (the cofactor for tyrosine hydroxylase [TH]) is unknown. METHODS: The authors sequenced GCH1 and measured levels of total biopterin (BP) and total neopterin (NP), TH, and dopa decarboxylase (DDC) proteins, and the DA and vesicular monoamine transporters (DAT, VMAT2) in autopsied brain of two patients with typical DRD. RESULTS: Patient 1 had two GCH1 mutations but Patient 2 had no mutation in the coding region of this gene. Striatal BP levels were markedly reduced (<20% of control subjects) in both patients and were also low in two conditions characterized by degeneration of nigrostriatal DA neurons (PD and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treated primate), whereas brain NP concentrations were selectively decreased (<45%) in the DRD patients. In the putamen, both DRD patients had severely reduced (<3%) TH protein levels but had normal concentrations of DDC protein, DAT, and VMAT2. CONCLUSIONS: The data suggest that 1) brain BH4 is decreased substantially in dopa-responsive dystonia, 2) dopa-responsive dystonia can be distinguished from degenerative nigrostriatal dopamine deficiency disorders by the presence of reduced brain neopterin, and 3) the striatal dopamine reduction in dopa-responsive dystonia is caused by decreased TH activity due to low cofactor concentration and to actual loss of TH protein. This reduction of TH protein, which might be explained by reduced enzyme stability/expression consequent to congenital BH4 deficiency, can be expected to limit the efficacy of acute BH4 administration on dopamine biosynthesis in dopa-responsive dystonia.     

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.     

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.     

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