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.     

Hereditary spastic paraplegia: clinical genetic study of 15 families

BACKGROUND: Autosomal dominant hereditary spastic paraplegia (ADHSP) is mainly caused by mutations in the SPG4 gene, which encodes a new member of the AAA (adenosine triphosphatases associated with diverse cellular activities) protein family (spastin). Accumulation of genotype-phenotype correlation is important for better understanding of SPG4-linked hereditary spastic paraplegia. OBJECTIVES: To perform a clinical and genetic study of families with ADHSP and to perform the functional analysis of the founder mutation discovered in the SPG4 gene. DESIGN: Genetic and clinical study.Patients Fifteen unrelated families with ADHSP originating from southern Scotland. MAIN OUTCOME MEASURES: Clinical assessment, linkage analysis, haplotype study, expression of mutant spastin protein in cultured cells. RESULTS: Nine families with ADHSP were linked to the SPG4 locus at 2p21-p24. Sequence analysis of SPG4showed a novel N386S mutation in all 9 of these families. Expression of mutant spastin showed aberrant distribution in cultured cells. Haplotype analysis suggested the existence of a common founder. Clinical examination of the affected members carrying the mutation showed phenotypic variations including broad range of age at onset and disease duration and additional neurologic features such as mental retardation. Magnetic resonance imaging demonstrated unique features, including thin corpus callosum and atrophy of the cerebellum in 2 patients. Linkage and sequence analyses showed no evidence of linkage to the currently known ADHSP loci in the remaining 6 families. CONCLUSIONS: A founder SPG4 mutation N386S was identified in the families with ADHSP originating from southern Scotland. Clinical investigation showed intrafamilial and interfamilial phenotypic variations. The genetic study demonstrated evidence of further genetic heterogeneity in ADHSP.     

Atlastin1 mutations are frequent in young-onset autosomal dominant spastic paraplegia

BACKGROUND: Hereditary spastic paraplegias are disorders that are very heterogeneous, both clinically and genetically. The atlastin1 gene has recently been implicated in SPG3A, a form of autosomal dominant pure spastic paraplegia. Atlastin1 mutations have been identified in 8 families so far. OBJECTIVES: To determine the relative frequency, phenotype, and mutation spectrum of SPG3A in patients with pure autosomal dominant spastic paraplegia and onset before age 20 years. PATIENTS AND METHODS: We sequenced the atlastin1 gene in a large series of patients (31 families) in which mutations in the spastin gene, corresponding to the frequent SPG4 locus, had previously been excluded. The phenotype was compared with 126 SPG4 patients. RESULTS: We identified 12 families (39%) including 34 patients with 9 different missense atlastin1 mutations, 7 of which are newly described. The main clinical characteristic of these SPG3A patients was pure spasticity with very young onset of symptoms (mean age, 4.6 +/- 3.9 years) and slow progression. However, additional signs such as decreased vibration sense and wasting in lower limbs, sphincter disturbances, and scoliosis were found in a minority of patients. In addition, several gene carriers were clinically affected but still asymptomatic (n = 5) or had no clinical signs (n = 2), indicating incomplete penetrance. Compared with patients from other families meeting the same diagnostic criteria (43 patients) and families with SPG4 (126 patients), the major form of autosomal dominant spastic paraplegia, SPG3A patients had earlier symptom onset, less frequently increased reflexes in the upper limbs, decreased vibration sense in the lower limbs, and fewer sphincter disturbances, but more frequently observed wasting in the lower limbs and scoliosis. These particularities, as well as frequent abnormal motor evoked potentials, could help identify patients to be screened for atlastin1 gene mutations. CONCLUSIONS: This study enables us to estimate the frequency of the SPG3A mutations in France at 39% in families with young-onset autosomal dominant spastic paraplegia after exclusion of SPG4 cases. So far, most mutations have been private, although they were all found in exons 7, 8, 12, and 13. These exons should be given priority when performing molecular diagnoses for SPG3A.     

SPG3A: An additional family carrying a new atlastin mutation

The authors report on a novel frameshift mutation (c.1688insA) in the SPG3A gene resulting in premature translation termination of the gene product atlastin. These data add a new variant to the second disease gene in autosomal dominant hereditary spastic paraplegia (ADHSP) and lend definitive support to its causative role. By combining direct testing of SPAST and SPG3A, at least 50% of ADHSP families can now receive appropriate genetic diagnosis.     

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.     

A missense mutation in the coiled-coil domain of the KIF5A gene and late-onset hereditary spastic paraplegia

BACKGROUND: To our knowledge, up to now, only 2 mutations in the KIF5A gene, a member of the kinesin superfamily, have been identified as the molecular cause of early-onset autosomal dominant hereditary spastic paraparesis (ADHSP). OBJECTIVE: To assess the genetic defect in a family with late-onset ADHSP. PATIENTS AND METHODS: Only the proband agreed to undergo complete neurological testing and mutational analysis. The proband was screened for mutations in the spastin, atlastin, NIPA1, and KIF5A genes, either by denaturing high-performance liquid chromatography or sequence analysis. RESULTS: The history of the family was consistent with ADHSP characterized by late onset of the disease. Mutational analysis results were negative for the spastin, atlastin, and NIPA1 genes but identified a missense mutation (c.1082C>T) in the coiled-coil coding region of the KIF5A gene. CONCLUSIONS: This finding enlarges the phenotypic spectrum of ADHSP linked to KIF5A and enhances the role of that gene in the epidemiology of this disease. We propose that the KIF5A gene should be routinely analyzed in patients with hereditary spastic paraplegia negative for spastin and atlastin mutations.     

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.     

Clinical and genetic characterization of hereditary spastic paraplegia type 3A in Taiwan

AimTo investigate the clinical and genetic features of hereditary spastic paraplegia (HSP) type 3A (SPG3A) in Taiwan.MethodsMutational analysis of the ATL1 gene was performed for 274 unrelated Taiwanese HSP patients. The diagnosis of SPG3A was ascertained by the presence of a heterozygous pathogenic mutation in ATL1. The SPG3A patients received clinical, electrophysiological, and neuroimaging evaluations. Disease severity was assessed by using Spastic Paraplegia Rating Scale (SPRS) and disability score. Nineteen single nucleotide polymorphism (SNP) markers flanking ATL1 were genotyped for haplotype analysis of ATL1 p.R416C mutation.ResultsEighteen SPG3A patients from 11 families were identified. They typically presented a pure form HSP phenotype with disease onset ranging from age 1–68 years. Five heterozygous ATL1 mutations were identified, including p.R239C, p.V253I, p.Y336H, p.P342R and p.R416C. ATL1 p.R416C was the most common mutation and presented in five SPG3A pedigrees. Haplotype analyses demonstrated a shared haplotype in the 12 individuals carrying a p.R416C allele.ConclusionSPG3A accounts for 4% (11 out of 274) of HSP in the Taiwanese cohort. Patents with the ATL1 p.R416C mutation in Taiwan may descend from a common ancestor. This study defines the clinical and genetic features of SPG3A in Taiwan and provides useful information for the diagnosis and management, especially in patients of Han Chinese descent.     

Hereditary spastic paraplegia 3A associated with axonal neuropathy

OBJECTIVE: To study the frequency and distribution of mutations in SPG3A in a large cohort of patients with hereditary spastic paraplegia. DESIGN: We screened a large cohort of 182 families and isolated cases with pure or complex hereditary spastic paraplegia phenotypes, which were negative for mutations in SPG4. RESULTS: In 12 probands (6.6%), we identified 12 different SPG3A mutations (11 missense and 1 insertion/frameshift) of which 7 were novel and 3 were de novo. We found incomplete penetrance in 1 family (G482V). In most cases, SPG3A mutations were associated with an early age at onset (mean, 3 y); however, in 1 family (R495W mutation), symptoms started later (mean, 14 y) with clear intrafamilial variability (8-28 y). Six patients with an SPG3A mutation (F151S, Q191R, M408T, G469A, R495W) originating from 5 unrelated families presented with a complex form of hereditary spastic paraplegia associated with a neuropathy (17%). Our electrophysiological and pathological findings confirmed an axonal sensory-motor neuropathy. There was no correlation between the genotype and the presence of a neuropathy. CONCLUSIONS: We conclude that mutations in SPG3A represent an important cause of patients in the overall hereditary spastic paraplegia population. SPG3A is more often associated with a neuropathy than previously assumed. Therefore, patients with a bipyramidal syndrome and a neuropathy should be screened for mutations in SPG3A.     

Clinical and genetic study of a large Italian family linked to SPG12 locus

BACKGROUND: Seven loci for autosomal dominant hereditary spastic paraplegia (ADHSP) have been mapped. To date, two families of SPG12 (chromosome 19q13) have been analyzed; however, there is not enough clinical information on SPG12 to establish locus-phenotype correlations. METHODS: The authors studied 60 individuals from a large Italian family with ADHSP, in which 16 members in four generations were affected. They performed genetic linkage analysis with DNA markers from currently known ADHSP loci. After database searching, one candidate gene for SPG12 was analyzed by sequencing. RESULTS: The patients in this family showed an early onset and rapid progression of symptoms, resulting in severe disability, with a large proportion of affected members requiring use of a wheelchair. By age 16, most patients had sensory disturbance. Evidence for linkage to the SPG12 locus was obtained. Obligate recombination events observed in this family have narrowed the SPG12 locus from the 16.1 cM to 11.3 cM region between markers D19S416 and D19S412. In combination with previous genetic studies, the SPG12 locus was further narrowed to the 3.3 cM region between D19S416 and D19S220. A homologue of the AAA (ATPases associated with a variety of cellular activities) protein family, proteasome 26S subunit ATPase mapped near D19S220, was excluded by sequencing. CONCLUSIONS: This study refined the SPG12 region between D19S416 and D19S220 and revealed several clinical characteristics-early onset, rapid progression, and involvement of sensory disturbance-that may be unique to SPG12. Suggestive evidence of genetic anticipation was obtained, but should be confirmed in other SPG12 families.     

Spectrum of SPG4 mutations in a large collection of North American families with hereditary spastic paraplegia

BACKGROUND: Hereditary spastic paraplegia (HSP) is a neurodegenerative disease characterized by progressive spasticity and weakness of the lower limbs. The most common form of HSP is caused by mutations in the SPG4 gene, which codes for spastin, an adenosine triphosphatase with various cellular activities (AAA) protein family member. OBJECTIVE: To investigate a large collection of predominantly North American patients with HSP for mutations in the spastin encoding gene, SPG4. METHODS: DNA from 76 unrelated affected individuals was studied for mutations by single-stranded conformational polymorphism analysis and direct sequencing. Each new variant identified was then analyzed in 80 control subjects to determine whether the variant is a common polymorphism or a rare mutation. All DNA samples were amplified by polymerase chain reaction, followed by electrophoresis and autoradiography. RESULTS: We identified 8 novel mutations and 5 previously reported mutations in 15 affected individuals. The novel mutations are 4 missense, 1 nonsense, 1 frameshift, and 2 splice mutations. Two polymorphisms (one in an affected individual) were also identified. CONCLUSIONS: Our collection of families with HSP is different on a genetic level from those previously described. The percentage of our families with a SPG4 mutation is 10% lower than the 40% estimate of families with autosomal dominant HSP noted to be linked to this locus, and splice mutations are not predominant in our collection. Interestingly, we also identified 2 recurring mutations in specific populations (R562Q and G559D), which may facilitate the development of future spastin diagnostic testing in these populations.     

De novo occurrence of novel SPG3A/atlastin mutation presenting as cerebral palsy

BACKGROUND: Mutations in the SPG3A gene (atlastin protein) cause approximately 10% of autosomal-dominant hereditary spastic paraplegia. For many subjects with an SPG3A mutation, spastic gait begins in early childhood and does not significantly worsen even over many years. Such subjects resemble those with spastic diplegic cerebral palsy. To date, only 9 SPG3A mutations have been reported. OBJECTIVE: To analyze the SPG3A coding sequence in an individual with childhood-onset spastic gait, who, prior to the birth of her similarly affected child, had no previous family history of hereditary spastic paraplegia. METHODS: The SPG3A coding sequence was analyzed in DNA samples from the proband, her affected child, her unaffected parents, and control subjects by polymerase-chain-reaction amplification of each exon followed by direct DNA sequencing. Seventeen microsatellite polymorphisms were amplified and analyzed to confirm reported paternity. RESULTS: We identified a novel SPG3A mutation (L157W) in the proband and her affected child. This mutation was absent in the proband's unaffected parents. Results of microsatellite polymorphism analysis were consistent with paternity as reported. These results indicate that this novel SPG3A mutation arose de novo in the proband. CONCLUSIONS: We report the de novo occurrence of a novel SPG3A mutation in a subject with childhood-onset, nonprogressive, spastic diplegia who had no previous family history of hereditary spastic paraplegia until the birth of her similarly affected son. Although rare, the occurrence of a de novo hereditary spastic paraplegia gene mutation must be considered in subjects with spastic diplegic cerebral palsy for whom no other cause is identified. This is extremely important for correct genetic counseling because recurrence risk may be as high as 50% when a mutation is detected.     

Intrafamilial variability in hereditary spastic paraplegia associated with an SPG4 gene mutation

The authors studied a family with pure autosomal dominant spastic paraplegia (ADHSP) that showed a marked intrafamilial variability in both age at onset and clinical severity, ranging from severe congenital presentation to mild involvement after age 55. They found a novel mutation in the SPG4 gene, which segregates with the disease in six patients. The mutation affects the consensus donor splice site of SPG4 intron 16, resulting in a premature termination codon at amino acid 578. The data confirm the pathologic significance of SPG4 mutations in pure ADHSP and add to the list of known SPG4 allelic variants.     

Novel mutation in the SPG3A gene in an African American family with an early onset of hereditary spastic paraplegia

BACKGROUND: Mutations in a novel GTPase gene SPG3A cause an autosomal dominant hereditary spastic paraplegia linked to chromosome 14q (SPG3), which accounts for approximately 10% to 15% of all autosomal dominant hereditary spastic paraplegia cases. The mutational spectrum of the SPG3A gene and the phenotype/genotype correlations have not yet been established. OBJECTIVE: To describe a kindred with an infantile onset of hereditary spastic paraplegia caused by a novel mutation in the SPG3A gene. PATIENTS: Complete neurological examination and genetic analysis were performed on 6 affected members of a small African American kindred. Linkage analysis to genetic markers near autosomal dominant hereditary spastic paraplegia loci on chromosomes 2p and 14q was performed. The coding sequence of the SPG3A gene was analyzed, and the identified change in the sequence was tested for being a benign polymorphism by sequencing 200 chromosomes from normal controls. RESULTS: Every affected individual had signs of uncomplicated spastic paraparesis without additional neurological abnormalities. None of the affected family members had ever walked normally. The history was consistent with an infantile onset, despite the normal acquisition of motor milestones. Genetic analysis suggested linkage to the SPG3A locus on chromosome 14q. Analysis of the SPG3A gene revealed a missense mutation C635T, predicted to result in a threonine to isoleucine substitution at codon 156. Analysis of 200 normal chromosomes did not identify the same change in healthy subjects. CONCLUSION: We report a novel mutation in the SPG3A gene in an African American family with an infantile onset of autosomal dominant hereditary spastic paraplegia.     

Missense and splice site mutations in SPG4 suggest loss-of-function in dominant spastic paraplegia

We studied nine Italian families with a pure form of autosomal dominant spastic paraplegia (ADHSP) to assess the frequency of mutations in the SPG4 gene. We observed marked intrafamilial variability in both age-at-onset and clinical severity, ranging from severe congenital presentation to mild involvement after age 55 years to healthy carriers of the mutation after age 70. Four of nine probands harboured SPG4 mutations, We identified three new SPG4 mutations, all predicting a loss-of-function with apparently important consequences for spastin function. RT-PCR studies predict loss-of-function as a possible mechanism leading to spastin-related HSP. The current study expands the spectrum of allelic variants in SPG4, confirming their pathological significance in pure AD-HSP and suggesting implications for the presumed function of spastin. Received: 15 December 2000, Received in revised form: 29 May 2001, Accepted: 18 June 2001     

Clinical and genetic study of a Brazilian family with spastic paraplegia (SPG6 locus).

We describe a Brazilian family in which inheritance of a G106R mutation in the SPG6 gene (also know as NIPA1) resulted in an autosomal dominant form of hereditary spastic paraplegia (ADHSP). Clinical investigations indicated that this family has a pure form of spastic paraplegia. All patients presented with gait difficulty in their twenties, progressing to frank spastic paraplegia during the next decade. Our report further supports evidence that mutations in SPG6 cause ADHSP.     

A large Japanese SPG4 family with a novel insertion mutation of the SPG4 gene: a clinical and genetic study

We studied a large Japanese family with autosomal dominant pure hereditary spastic paraplegia (ADPHSP) clinically and genetically. To date, seven loci causing ADPHSP have been mapped to chromosomes 14q, 2p, 15q, 8q, 12q, 2q, and 19q. Among these loci, the SPG4 locus on chromosome 2p21--p22 has been shown to account for approximately 40% of all autosomal dominant hereditary spastic paraplegia (ADHSP) families. Very recently, Hazan et al. identified the SPG4 gene encoding a new member of the AAA (ATPases associated with diverse cellular activities) protein family, named spastin. We found a novel insertion mutation (nt1272--1273insA) in exon 8 of the SPG4 gene in the present family. Our study is the first to confirm the causative mutation of the SPG4 gene in Japanese. Clinically, it is noteworthy that the disease progression in the patients of this family was slow in spite of the late onset, and more than half of the patients showed severe constipation in addition to pure spastic paraplegia.     

Mutation in KIF5A can also cause adult-onset hereditary spastic paraplegia

Autosomal dominant hereditary spastic paraplegia (AD HSP) linked to chromosome 12q (SPG10) is caused by mutations in the neuronal kinesin heavy-chain KIF5A gene. This is a rare cause of AD HSP, and only two disease-causing mutations have been reported thus far. In both instances, affected individuals harboring mutations in the KIF5A gene displayed symptom onset at a very early age. Here we present the results of clinical and genetic analyses of a large kindred with uncomplicated AD HSP. We were able to establish a definitive linkage to the SPG10 locus, and sequencing of the KIF5A gene revealed a heterozygous missense mutation 1,035 A>G in exon 10, resulting in tyrosine-to-cysteine substitution. This mutation is located in a highly conserved kinesin motor domain of the neuronal kinesin heavy-chain protein, but in contrast to two previously reported missense mutations, the age of symptom onset in our family was much later, with an average age of 36.1±4 years. Our results demonstrate that mutations in the KIF5A gene can also be associated with an adult age of onset of AD HSP.     

Three novel mutations of the spastin gene in Chinese patients with hereditary spastic paraplegia

BACKGROUND: Hereditary spastic paraplegia is a group of genetically heterogeneous neurodegenerative disorders characterized by progressive spasticity of the lower limbs. The most common form of hereditary spastic paraplegia is caused by mutations in the spastin gene (SPG4), which encodes spastin, an adenosine triphosphatase associated with various cellular activities protein. OBJECTIVE: To investigate the Chinese patients with hereditary spastic paraplegia for mutations in SPG4. METHODS: DNA samples from 31 unrelated patients were analyzed for mutations in SPG4 by single-strand conformation polymorphism analysis and direct sequencing. All DNA samples were screened for mutations by the polymerase chain reaction, followed by electrophoresis and silver staining. Each new variant identified was analyzed in 50 control subjects to determine whether it is a polymorphism or a mutation. RESULTS: Three novel mutations were detected in 4 affected individuals, including 2 missense mutations (T1258A and A1293G) and 1 deletion mutation (1668-1670delCTA). CONCLUSIONS: To our knowledge, this is the first report of SPG4 mutations in the People's Republic of China. The percentage of involved Chinese families with autosomal dominant hereditary spastic paraplegia with an SPG4 mutation is 18% (4/22), lower than the estimated 40% linked to this locus.     

遗传性痉挛性截瘫atlastin基因突变分析

目的 探讨中国人遗传性痉挛性截瘫（HSP）atlastin基因的突变特点,为HSP的基因诊断奠定基础。方法 应用聚合酶链反应一单链构象多态性（PCR-SSCP）结合DNA序列分析方法,对来自全国20例常染色体显性遗传HSP家系的先证者和10例散发性HSP患者进行了atlastin基因突变分析。结果 在20例常染色体显性遗传HSP家系的先证者和10例散发性HSP患者中均未发现异常SSCP条带,第7号外显子直接DNA序列分析亦无异常。结论 atlastin基因突变可能在中国人HSP患者中少见。