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     

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     

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.     

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.     

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.     

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。     

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.     

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.     

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     

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.     

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     

应用多重连接依赖性探针扩增定量技术检测假肥大型肌营养不良重复突变及携带状态

目的 应用多重连接依赖性探针扩增(MLPA)技术对假肥大型肌营养不良(DMD及BMD)患者及其家系成员进行dystrophin基因分析,探讨MLPA定量技术在本病重复突变及携带者检测中的优势.方法 以355例DMD及BMD患者、46名缺失型患者之母和8名重复型患者之母为研究对象,应用MLPA技术对dystrophin基因全长外显子进行分析,对于单一外显子缺失的样本采用PCR及测序进行验证.结果 经MLPA分析,全部355例患者中190例为dystrophin基因缺失型患者,在其余非缺失型患者中检测出34例重复型突变.此外,在46名缺失型患者的母亲中发现了28名携带者,在8名重复型患者的母亲中发现了6名携带者,两组患者母亲携带者频率差异无统计学意义.经过测序验证,在1例单一外显子缺失的患者中发现17号外显子存在AGGGAACAGATCCTGGTAAAGCA小片段缺失.结论 与传统的定量方法相比,MLPA定量技术可对DMD及BMD患者全长外显子区域同时进行缺失、重复分析,并能对患者家系成员的携带状态进行判定.此外,MLPA检测结果受模板DNA的浓度及纯度影响较小.     

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 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.     

多巴反应性肌张力障碍的临床特点和基因诊断

目的 研究多巴反应性肌张力障碍(DRD)患者的临床特点和三磷酸鸟苷环化水解酶Ⅰ(GCH Ⅰ)基因突变.方法 对18例家族性和17例散发性DRD患者按发病年龄分为儿童期、青春期和成年期发病组,对3组患者进行病史采集、神经系统体格检查、神经心理测试和头颅CT或MRI扫描.对其中26例患者及1名无症状家族成员进行GCH Ⅰ基因的突变分析.选取35例无任何神经系统异常的健康人作为健康对照.结果 (1)儿童期发病组(15/15)、青春期发病组(6/6)与成人期发病组(7/14)比较,症状具有日间波动性者比例的差异有统计学意义(χ2=13.125,P=0.001),且症状波动性与年龄旱负相关(r=-0.720,P<0.01).(2)3组间姿势性震颤的发生率(7/15、5/6、1/14)差异有统计学意义(χ2=8.073,P=0.018),姿势性震颤发生率与患者年龄呈正相关(r=0.399,P=0.018).(3)3组患者腱反射亢进的发生率(11/15、1/6、4/14)差异有统计学意义(χ2=8.309,P=0.016),腱反射亢进发生率与年龄旱负相关(r=-0.429,P=0.010).(4)病例组汉密尔顿抑郁评分和焦虑评分均高于对照组.(5)在其中1个家系检出GCH Ⅰ基因杂合型点突变A224G.结论 DRD临床表现多样,临床表现与年龄密切相关,GCH Ⅰ基因杂合型点突变A224G可能导致发病.     

Are dopa-responsive dystonia and Parkinson’s disease related disorders? A case report

Objectivel-Dopa-responsive dystonia (DRD) is a hereditary dystonia characterized by an excellent response to low dosages of levodopa. DRD patients may also develop Parkinsonism which resembles idiopathic Parkinson’s disease. In classical DRD no changes in the dopaminergic uptake have been observed.MethodsA 65-year old woman presented with clinically remarkably slowly progressing Parkinson’s disease (PD) without any dystonic signs and excellent response to dopaminergic medications. We obtained a [¹²³I] FP-CIT-SPECT (DaTSCAN?) in order to elucidate a striatal dopaminergic deficit.ResultsWe found a reduced uptake in the [¹²³I] FP-CIT-SPECT (DaTSCAN?) contralateral to the more affected body side. Additionally, the patient showed a heterozygous deletion of the GHC1 gene.ConclusionsPatients with mild parkinsonian symptoms, excellent response to low dosages of dopaminergic drugs and a reduced dopamine-transporter uptake in [¹²³I] FP-CIT-SPECT might more commonly be GCH1 mutation carriers than has previously been supposed. PD patients with a positive family history of DRD and combination of these clinical symptoms should be offered genetic counselling and testing for GCH1.     

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.     

A new splice site mutation in the SMN1 gene causes discrepant results in SMN1 deletion screening approaches

In most patients with infantile spinal muscular atrophy (SMA) both exons 7 and 8 of the SMN1 gene are deleted, but the deletion may also be restricted to exon 7. We report on an SMA type I patient who was initially diagnosed to be homozygous for an exon 7 deletion only. However, multiplex ligation-dependent probe amplification (MLPA) analyses revealed a heterozygous deletion of exons 7 and 8 of the SMN1 gene. By sequencing a new subtle splice site mutation (IVS6-2A>G) was identified. This variant affects the target sequence of oligonucleotides of all applied tests in a way that it has contrary effects on the efficiencies of the different assays. The results have major impacts on genetic counselling and carrier detection of the patient's paternal relatives.     

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.