Two novel mutations in the Spastin gene of Chinese patients with hereditary spastic paraplegia

Background and purpose: Hereditary spastic paraplegia (HSP) is a clinically and genetically heterogeneous group of neurodegenerative diseases. Mutations in the spastin (SPG4) gene are responsible for approximately 40% of autosomal dominant HSP (AD‐HSP) and 6.5–18% of sporadic cases. Methods: Spastin mutations were screened in 11 AD‐HSP families and 11 sporadic cases by direct sequencing and MLPA assay. Novel mutations were detected in 100 healthy controls by PCR‐RFLP. Results: We identified seven different spastin mutations in five probands and one sporadic patient. Two of seven mutations were novel. The c.458delT was a pathogenic mutation, but the effect of c.1724 G>T remained unknown. Conclusions: This study allowed us to estimate the frequency of the SPG4 mutations in Chinese at 45% (5/11) in families with AD‐HSP and 9% (1/11) in sporadic cases. In addition, our data showed p.T614I was not associated with congenital arachnoid cysts.     

Expansion of the phenotypic spectrum of SPG6 caused by mutation in NIPA1

Background

Hereditary spastic paraplegia type 6 (SPG6) is caused by mutations in the NIPA1 gene, this is a rare cause of HSP, until now, all the affected individuals reported displayed “pure” spastic paraplegia.

Objectives

To analyze the genotype/phenotype correlation of mutations so far described in NIPA1.

Methods

Eighty-six Chinese Han HSP patients were investigated for SPG6 mutations by direct sequencing of the NIPA1 gene.

Results

One heterozygous missense mutation c.316G > C/p.G106R was identified in a complicated form of ADHSP family with peripheral nerves disease, and SPG6 mutation in our sample accounted for 3.6% (1/28) of ADHSP families and 1.1% (1/86) of non-ARHSP patients who were negative for SPG4, SPG3A and SPG31 mutations.

Conclusions

We report the first complicated case of SPG6 in the world by the presence of peripheral neuropathy, which extends the phenotype initially described.     

遗传性痉挛性截瘫11型基因突变分析

目的 探讨中国人群遗传性痉挛性截瘫11型(SPGll)基因突变频率及临床特点.方法 应用聚合酶链反应(PCR)结合直接测序方法对28个常染色体隐性遗传性痉挛性截瘫(ARHSP)家系先证者和14例散发痉挛性截瘫合并胼胝体发育不良患者进行SPG11基因突变分析.结果 共确诊10例SPG11家系,其中7个为ARHSP家系,3例为散发患者,共携带有13个SPG11基因新突变:c.5977C>T/p.Q1993X、c.4668T>A/p.Y1556X、c.6898_6899delCT/p.L2300AfsX23.38、c.3719_3720delTA/p.11240VfsX263、c.733_734delAT/p.M245VfsX246、c.7088_7089insATTA/p.Y2363X、c.2163_2164insT/p.1722Yfsx731、c.7101-7102insT/p.K2368X、c.6790_6791insC/p.12264PfsX2339、c.654_655delinsG/p.S218RfsX219、c.7151+4_7151+7delAGTA/p.K2384fsX2386、c.6355-21_6355-18delTCT、c.3004C>T/p.G1002X.SPG11在ARHSP家系的发病率约为25.0%(7/28),在ARHSP合并胼胝体发育不良(ARHSP-TCC)家系的发病率为6/6,在散发HSP-TCC患者中突变率为3/14.结论 对于中国人群而言,复杂型ARHSP和散发HSP-TCC患者应首先排除SPG11基因突变.     

Novel spastin (SPG4) mutations in Italian patients with hereditary spastic paraplegia

Spastic paraplegia type 4 is caused by mutations in the gene that encodes spastin (SPG4), a member of the AAA protein family. A cohort of 34 unrelated Italian patients with pure spastic paraplegia, of which 18 displayed autosomal dominant inheritance and 16 were apparently sporadic, were screened for mutations in the SPG4 gene by denaturing high performance liquid chromatography. We identified a previously reported mutation in a sporadic patient with pure hereditary spastic paraplegia. We also identified eight unrelated patients with pure autosomal dominant hereditary spastic paraplegia carrying five novel mutations in the SPG4 gene (one missense mutation, c.1304 C>T; one nonsense mutation, c.807C>A; two frameshift mutations, c.1281dupT, c.1514_1515insATA; and one splicing mutation, c.1322-2A>C). The frequency for SPG4 mutations detected in autosomal dominant hereditary spastic paraplegia was 44.4%. This study contributes to expand the spectrum of SPG4 mutations in Italian population.     

Targeted next generation sequencing in SPAST-negative hereditary spastic paraplegia

Molecular characterization is important for an accurate diagnosis in hereditary spastic paraplegia (HSP). Mutations in the gene SPAST (SPG4) are the most common cause of autosomal dominant forms. We performed targeted next generation sequencing (NGS) in a SPAST-negative HSP sample. Forty-four consecutive HSP patients were recruited from an adult neurogenetics clinic in Sydney, Australia. SPAST mutations were confirmed in 17 subjects, and therefore 27 SPAST-negative patients were entered into this study. Patients were screened according to mode of inheritance using a PCR-based library and NGS (Roche Junior 454 sequencing platform). The screening panel included ten autosomal dominant (AD) and nine autosomal recessive (AR) HSP-causing genes. A genetic cause for HSP was identified in 25.9 % (7/27) of patients, including 1/12 classified as AD and 6/15 as AR or sporadic inheritance. Several forms of HSP were identified, including one patient with SPG31, four with SPG7 (with one novel SPG7 mutation) and two with SPG5 (including two novel CYP7B1 frameshift mutations). Additional clinical features were noted, including optic atrophy and ataxia for patients with SPG5 and ataxia and a chronic progressive external ophthalmoplegia-like phenotype for SPG7. This protocol enabled the identification of a genetic cause in approximately 25 % of patients in whom one of the most common genetic forms of HSP (SPG4) was excluded. Targeted NGS may be a useful method to screen for mutations in multiple genes associated with HSP. More studies are warranted to determine the optimal approach to achieve a genetic diagnosis in this condition.     

A novel homozygous mutation in ATP13A2 gene causing pure hereditary spastic paraplegia

SPG78 is a subtype of hereditary spastic paraplegia(HSP) caused by ATP13A2 gene mutations. SPG78 was reported as complicated HSP in several cases, but was never associated with pure HSP. Here we report the first Chinese patient carrying a novel homozygous nonsense mutation in ATP13A2 presenting with pure HSP.     

Clinical and genetic findings in a series of Italian children with pure hereditary spastic paraplegia

Background: Hereditary spastic paraplegias (HSP) are a group of neurodegenerative disorders characterized by progressive lower extremity spastic weakness. SPG7, SPG4 and SPG3A are some of the autosomal genes recently found as mutated in recessive or dominant forms of HSP in childhood. SPG31 is more often associated with a pure spastic paraplegia phenotype, but genotype–phenotype correlation is still unclear. The aims of the current study was: (i) to verify the mutational frequency of SPG4, SPG3A, SPG31 and SPG7 genes in our very‐well‐selected childhood sample, and (ii) to improve our knowledge about the clinical and electrophysiological HSP phenotypes and their possible correlation with a specific mutation. Methods: A sample of 14 Italian children affected by pure HSP (mean age at diagnosis 5.9 years) was extensively investigated with electrophysiological, neuroradiological and genetic tests. Results: Three SPG4 mutations were identified in three patients: two novel missense mutations, both sporadic, and one multiexonic deletion already reported. A novel large deletion in SPG31 gene involving exons 2–5 was also detected in one young patient. No mutations in the SPG7 and in the SPG3A genes were found. Conclusions: Our data confirm that HSP represent a heterogeneous group of genetic neurodegenerative disorders, also in sporadic or autosomal recessive early onset forms. Multiplex Ligation‐dependent Probe Amplification‐based mutation screening for SPG4 and SPG31 genes would be added to sequencing‐based screening of SPG4, SPG31 and SPG3A genes in the routine diagnosis of HSP children.     

Eight novel mutations in SPG4 in a large sample of patients with hereditary spastic paraplegia

BACKGROUND: Hereditary spastic paraplegia (HSP) is a group of genetically heterogeneous disorders characterized by progressive spasticity of the lower limbs. Mutations in the SPG4 gene, which encodes spastin protein, are responsible for up to 45% of autosomal dominant cases. OBJECTIVE: To search for disease-causing mutations in a large series of Italian patients with HSP. DESIGN: Samples of DNA were analyzed by direct sequencing of all exons in SPG4. Samples from a subset of patients were also analyzed by direct sequencing of all exons in SPG3A, SPG6, SPG10, and SPG13. SETTING: Molecular testing facility in Italy. PATIENTS: Sixty unrelated Italian patients with pure (n = 50) and complicated (n = 10) HSP. MAIN OUTCOME MEASURES: Mutations in SPG4, SPG3A, SPG6, SPG10, and SPG13. RESULTS: We identified 12 different mutations, 8 of which were novel, in 13 patients. No mutations of any of the other HSP genes tested were found in 15 patients with sporadic pure HSP who did not have mutations in the SPG4 gene. CONCLUSIONS: The overall rate of mutation in the SPG4 gene within our sample was 22%, rising to 26% when only patients with pure HSP were considered. The negative result obtained in 15 patients without mutations in SPG4 in whom 4 other genes were analyzed (SPG3A, SPG6, SPG10, and SPG13) indicate that these genes are not frequently mutated in sporadic pure HSP.     

Early onset autosomal dominant spastic paraplegia caused by novel mutations in SPG3A

Hereditary spastic paraplegia (HSP) is a group of neurodegenerative disorders mainly characterized by progressive spasticity of the lower limbs. The major features of HSP are a marked phenotypic variability both among and within families and an extended genetic heterogeneity. More than 20 HSP loci and 10 spastic paraplegia genes ( SPG) have been identified to date, including the genes responsible for the two most frequent forms of autosomal dominant spastic paraplegia (AD-HSP), encoding spastin ( SPG4) and atlastin ( SPG3A), respectively. To date, only eight mutations have been described in the atlastin gene, which was reported to account for about 10% of all AD-HSP families. We investigated 15 German and French AD-HSP families, including the 3 large pedigrees that allowed the mapping and subsequent refinement of the SPG3A locus. Three novel mutations were found in exons 4, 9, and 12 of the atlastin gene and the common R239C mutation located in exon 7 was confirmed in a 7th family of European origin. Overall, the comparison of the clinical data for all SPG3A-HSP families reported to date failed to reveal any genotype/phenotype correlation as demonstrated for other forms of AD-HSP. However, it confirmed the early onset of this form of HSP, which was observed in almost all affected individuals with a mutation in the atlastin gene.     

NIPA1 mutation in complex hereditary spastic paraplegia with epilepsy

Background and purpose: Hereditary spastic paraplegia (HSP) is a group of clinically and genetically heterogeneous neurodegenerative disorders characterized in the ‘pure’ phenotype by progressive spasticity and weakness of the lower limbs. In the ‘complex’ phenotype, additional neurologic symptoms or signs are found. Mutations in the NIPA1 gene have been reported to cause spastic paraplegia type 6 (SPG6) in 10 families. SPG6 is a rare form of autosomal dominantly inherited HSP associated with a pure phenotype; however, in one complex SPG6 family, idiopathic generalized epilepsy (IGE) has been described and in addition, recurrent microdeletions at 15q11.2 including NIPA1 have been identified in patients with IGE. The purpose was to identify NIPA1 mutations in patients with pure and complex HSP. Methods: Fifty‐two patients with HSP were screened for mutations in NIPA1. Results: One previously reported missense mutation c.316G>A, p.Gly106Arg, was identified in a complex HSP patient with spastic dysarthria, facial dystonia, atrophy of the small hand muscles, upper limb spasticity, and presumably IGE. The epilepsy co‐segregated with HSP in the family. Conclusion: NIPA1 mutations were rare in our population of patients with HSP, but can be found in patients with complex HSP. Epilepsy might be more common in SPG6 than in other forms of HSP because of a genetic risk factor closely linked to NIPA1.     

Mutations in CYP2U1, DDHD2 and GBA2 genes are rare causes of complicated forms of hereditary spastic paraparesis

Complicated hereditary spastic paraplegias (HSP) are a heterogeneous group of HSP characterized by spasticity associated with a variable combination of neurologic and extra-neurologic signs and symptoms. Among them, HSP with thin corpus callosum and intellectual disability is a frequent subtype, often inherited as a recessive trait (ARHSP-TCC). Within this heterogeneous subgroup, SPG11 and SPG15 represent the most frequent subtypes. We analyzed the mutation frequency of three genes associated with early-onset forms of ARHSP with and without TCC, CYP2U1/SPG56, DDHD2/SPG54 and GBA2/SPG46, in a large population of selected complicated HSP patients by using a combined approach of traditional-based and amplicon-based high-throughput pooled-sequencing. Three families with mutations were identified, one for each of the genes analyzed. Novel homozygous mutations were identified in CYP2U1 (c.1A>C/p.Met1?) and in GBA2 (c.2048G>C/p.Gly683Arg), while the homozygous mutation found in DDHD2 (c.1978G>C/p.Asp660His) had been previously reported in a compound heterozygous state. The phenotypes associated with the CYP2U1 and DDHD2 mutations overlap the SPG56 and the SPG54 subtypes, respectively, with few differences. By contrast, the GBA2 mutated patients show phenotypes combining typical features of both the SPG46 subtype and the recessive ataxia form, with marked intrafamilial variability thereby expanding the spectrum of clinical entities associated with GBA2 mutations. Overall, each of three genes analyzed shows a low mutation frequency in a general population of complicated HSP (<1 % for either CYP2U1 or DDHD2 and approximately 2 % for GBA2). These findings underline once again the genetic heterogeneity of ARHSP-TCC and the clinical overlap between complicated HSP and the recessive ataxia syndromes.     

Spastin mutation screening in Chinese patients with pure hereditary spastic paraplegia

BackgroundHereditary spastic paraplegia (HSP) is a clinically and genetically heterogeneous group of neurodegenerative diseases. Mutations in the spastin (SPAST) gene are the most common cause of pure HSP. However, few data are available regarding the clinical and genetic spectrum of HSP among Chinese patients.MethodsClinical data were collected at diagnosis and follow-up of 42 Chinese patients with pure HSP. All seventeen exons of the SPAST gene were directly sequenced. Additionally, we used a multiplex ligation dependent probe amplification (MLPA) assay targeting the SPAST gene to evaluate large exon deletion or insertion mutations in patients without SPAST point mutations.ResultsThe age of disease onset of our patients was 19.6 ± 14.4 years. Six novel variations were found, including three missense mutations (p. L363P, p. D441V, and p. S595R), one insertion (c.1511dupT (p. Y505Ifs*7)), and two larger deletions (exons 5–17 and exons 10–17). Four previously reported mutations, including p. S399L, c.1215_c.1219delTATAA (p. N405Kfs*36), exon 1 deletion, and exon 16 deletion, were detected. The SPAST mutation rate was 40% (4/10) in Chinese familial patients and 33.33% (7/21) in Chinese sporadic pure HSP patients. The frequency of large deletions was high in both AD-HSP (20%, 2/10) and sporadic HSP (14.28%, 3/21).ConclusionSPAST mutations are common in Chinese patients with pure HSP. Large exon deletions are an important cause of AD-HSP and sporadic pure HSP in Chinese patients. Large fragment tests should be performed to explore large SPAST mutations in familial and sporadic HSP patients without SPAST point mutations.     

Mutation analysis of SPG4 and SPG3A genes and its implication in molecular diagnosis of Korean patients with hereditary spastic paraplegia

BACKGROUND: Hereditary spastic paraplegia (HSP), a genetically and clinically heterogeneous group of neurodegenerative disorders, is characterized by progressive lower limb weakness and spasticity. Among the 8 loci associated with the autosomal dominant uncomplicated HSP (AD-HSP), the spastin (SPG4) and atlastin (SPG3A) genes have been known to account for approximately 40% and 10% of all cases, respectively. OBJECTIVE: To investigate the contribution of these 2 genes in the occurrence of HSP in Korean patients. DESIGN: Clinical and genetic study. SETTING: Tertiary care center. PATIENTS: Eighteen patients with uncomplicated HSP (11 AD and 7 sporadic) underwent screening for gene mutation. MAIN OUTCOME MEASURES: Mutations in the SPG4 and SPG3A genes as detected by direct sequencing of all coding exons and flanking intronic sequences. RESULTS: We identified 8 different SPG4 mutations, 7 of which have not been reported elsewhere. Among the detected mutations were 3 missense mutations, 2 in-frame deletions, 2 frameshift mutations, and 1 splice-site mutation. No mutation was found in the SPG3A gene. CONCLUSION: Compared with previous studies, a higher frequency of SPG4 gene mutations in AD-HSP (7/11; 64%) was observed, suggesting that a mutation analysis for the SPG4 gene might be helpful for molecular diagnosis of AD-HSP in Korean patients.     

Mitochondrial DNA polymorphisms/haplogroups in hereditary spastic paraplegia

Mitochondrial dysfunction could contribute to the development of spastic paraplegia. Among others, two of the genes implicated in hereditary spastic paraplegia encoded mitochondrial proteins and some of the clinical features frequently found in these patients resemble those observed in patients with mitochondrial DNA (mtDNA) mutations. We investigated the association between common mtDNA polymorphisms and spastic paraplegia. The ten mtDNA polymorphisms that defined the common European haplogroups were determined in 424 patients, 19% with a complicated phenotype. A rare haplogroup was associated with the disease in patients without a SPG3A, SPG4, or SPG7 mutation. Allele 10398G was more frequent among patients with a pure versus complicated phenotype. This mtDNA polymorphism was previously associated with the risk of developing other neurodegenerative diseases. In conclusion, some mtDNA polymorphisms could contribute to the development of spastic paraplegia or act as modifiers of the phenotype.     

Peripheral neuropathy in hereditary spastic paraplegia due to spastin (SPG4) mutation--a neurophysiological study using excitability techniques

ObjectiveTo identify peripheral nerve abnormalities in hereditary spastic paraplegia (HSP) due to mutations in the spastin gene (spastic paraplegia 4, SPG4) using standard nerve conduction (NCS) and novel tests of axonal excitability.MethodsEleven patients with known mutations in spastin were assessed with NCS for the upper and lower limbs, and axonal excitability testing on the median nerve.ResultsStandard nerve conduction studies revealed a sensorimotor neuropathy in two patients. Excitability studies on median motor axons showed an isolated abnormality (increased strength-duration time constant), but those on sensory axons were normal in nine patients with normal routine nerve conduction studies.ConclusionsPeripheral neuropathy occurs in HSP patients with SPG4 mutations, but axonal excitability studies provide limited additional evidence for subclinical peripheral nerve dysfunction, and add little further to standard nerve conduction studies.SignificanceThe features of HSP due to SPG4 mutations include sensorimotor polyneuropathy. The value of excitability studies is limited in individual patients.     

White matter lesions in spastic paraplegia with mutations in SPG5/CYP7B1

Hereditary spastic paraplegias (HSPs) are relatively frequent disorders presenting great genetic heterogeneity. The recent identification of mutations in SPG5/CYP7B1 in six autosomal recessive kindred linked to the SPG5 locus on chromosome 8q prompted us to test the relative frequency of SPG5/CYP7B1 variants in 12 families and in sporadic HSP patients by high-resolution melting screening combined with direct sequencing. We present two patients who harbored three mutations (including two novel variants) in SPG5/CYP7B1 and white matter involvement evidenced at brain MRI. In HSP patients in whom no other genes were mutated, screening of SPG5/CYP7B1 seems to have a low diagnostic yield in autosomal recessive (8%) and sporadic (<1%) cases, even in those with complicated clinical features.     

Seven novel mutations and four exon deletions in a collection of Norwegian patients with SPG4 hereditary spastic paraplegia

To establish the phenotypic variation and frequency of SPAST mutations or deletions in Norwegian patients with hereditary spastic paraplegia (HSP), we examined 59 unrelated patients with HSP and screened for DNA point mutations and microdeletions in SPG4 . Forty-one had a familial history, 35 had a clear dominant inheritance, six had other affected sibs and 18 were sporadic. We found 12 mutations in SPG4 , seven of them novel, and four different heterozygous exon deletions, two of them novel. Mutations were found in 16 families showing autosomal dominant (AD) inheritance, and in one sporadic case. In two non-SPG4 families the S44L polymorphism/modifier was found in both affected and unaffected individuals. This is the first study of Norwegian patients with HSP since the 1970s, and the first report on SPG4 in Norway. Our results show that SPG4 mutations and deletions are a significant cause of HSP in our population and warrant SPG4 screening in AD families and selected sporadic cases.     

Hereditary spastic paraplegia with cerebellar ataxia: a complex phenotype associated with a new SPG4 gene mutation

Complex forms of hereditary spastic paraplegia (HSP) are rare and usually transmitted in an autosomal recessive pattern. A family of four generations with autosomal dominant hereditary spastic paraplegia (AD-HSP) and a complex phenotype with variably expressed co-existing ataxia, dysarthria, unipolar depression, epilepsy, migraine, and cognitive impairment was investigated. Genetic linkage analysis and sequencing of the SPG4 gene was performed and electrophysiologic investigations were carried out in six individuals and positron emission tomography (PET) in one patient. The disease was linked to the SPG4 locus on chromosome 2p as previously reported for pure HSP. Sequence analysis of the SPG4 (spastin) gene identified a novel 1593 C > T (GLN490Stop) mutation leading to premature termination of exon 12 with ensuing truncation of the encoded protein. However, the mutation was only identified in those individuals who were clinically affected by a complex phenotype consisting of HSP and cerebellar ataxia. Other features noted in this kindred including epilepsy, cognitive impairment, depression, and migraine did not segregate with the HSP phenotype or mutation, and therefore the significance of these features to SPG4 is unclear. Electrophysiologic investigation showed increased central conduction time at somatosensory evoked potentials measured from the lower limbs as the only abnormal finding in two affected individuals with the SPG4 mutation. Moreover, PET of one patient showed significantly relatively decreased regional cerebral blood flow in most of the cerebellum. We conclude that this kindred demonstrates a considerable overlap between cerebellar ataxia and spastic paraplegia, emphasizing the marked clinical heterogeneity of HSP associated with spastin mutations.     

Hereditary spastic paraplegia type 11: Clinicogenetic lessons from 339 patients

Hereditary spastic paraplegia type 11 (SPG11) is the most common subtype of autosomal recessive hereditary spastic paraplegia (HSP), to date, there are more than 181 different KIAA1840 gene mutations detected, and yet the genetic landscape of SPG11 is far from complete. To find the clinical and genetic characteristics of SPG11, we performed a reanalysis of the clinical features and genotype-phenotype correlations in all reported studies exhibiting SPG11 mutations. A total of 339 patients were collected, their mean age at onset was 13.10 ± 3.65 years, with initial symptoms like gait disturbance (107/195, 54.87%) and mental retardation (47/195, 24.10%). Cognitive decline (228/270, 84.44%) was the most common complex manifestation stepped by dysarthria (134/195, 68.72%), neuropathy (112/177, 63.28%), amyatrophy, sphincter disturbance (60/130, 46.15%) and ataxia (90/194, 46.39%). The most common brain MRI abnormality is thinning of the corpus callosum (TCC) (173/190, 91.05%), followed by periventricular white matter changes (130/158, 82.28%), cerebral or cerebellar cortical atrophy (55/107, 51.40%). The mutational spectrum associated with KIAA1840 gene is wide, and frameshift mutations are the most common type followed by nonsense mutations. Our reanalysis demonstrated that SPG11 exhibited significant clinical and genetic heterogeneity, and no clear genotype-phenotype correlation was observed. There is no mutational hot spot in the KIAA1840 gene, which emphasizes the need to analyse the whole gene in clinical practice. In addition to conventional genetic testing methods, further mRNA analysis should be conducted on some cases to yield a definitive diagnosis.