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.     

Possible anticipation in hereditary spastic paraplegia type 4 (SPG4)

OBJECTIVE: We report a multigenerational family with uncomplicated hereditary spastic paraplegia type 4 and apparent anticipation. Genetic analysis of the proband revealed a frame shift mutation (5 base pair deletion) in exon 9 of the SPG4 gene encoding the spastin protein. We hypothesized that this deletion mutation may be dynamic and variability in the size of the deletion could account for the anticipation. METHODS: Clinical and genetic analysis of this family and the deletion mutation. RESULTS: In this family, the age of onset, which ranges from 3 to 50 years shows an average decrease in the age of onset of 21.8 years per transmission over three generations. Genetic analysis of multiple family members indicates that all affected members carry the same c.1340_1344delTATAA mutation and that it is not dynamic. CONCLUSION: In this family, other molecular mechanisms may contribute to development of anticipation.     

Complicated hereditary spastic paraplegia with peripheral neuropathy, optic atrophy and mental retardation

An 8-year old girl with a not previously described type of complicated hereditary spastic paraplegia (HSP) is presented. Spasticity in her lower limbs had already been recognized during infancy and worsened progressively. Severe delay in mental development was observed. Peripheral neuropathy and optic atrophy developed at 5 years of age. On brain magnetic resonance imaging, an abnormally thin corpus callosum was observed. Involvement of the fasciculus gracilis was suggested by somatosensory evoked potentials. To our knowledge, there has been no reported case of complicated HSP with peripheral neuropathy, optic atrophy and mental retardation so far. We postulate that our patient is a sporadic case of not previously described complicated HSP.     

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.     

Motor activation in SPG4-linked hereditary spastic paraplegia

OBJECTIVE: The aim of this study was to investigate the extent of motor cortical functional reorganisation in patients with SPG4-linked hereditary spastic paraplegia by exploring cortical motor activation related to movements of clinically affected (lower) and unaffected (upper) limbs. METHODS: Thirteen patients and 13 normal controls matched for age, gender and handedness underwent O15-labelled water positron emission tomography during (1) right ankle flexion-extension, (2) right shoulder flexion-extension and (3) rest. Within-group comparisons of movement vs. rest (simple main effects) and between-group comparisons of movement vs. rest (group x behavioural state interaction) were performed using a random effects approach and statistical parametric mapping (SPM99). RESULTS: Patterns of motor activation were generally comparable between groups during both tasks, although patients had a tendency towards more widespread activation in sensorimotor cortical and cerebellar regions. Statistically significant differences were restricted to the ankle movement response, however, where patients showed significantly increased regional cerebral blood flow in the right and left primary motor cortices, the supplementary motor areas and the right premotor cortex compared to controls. CONCLUSIONS: Motor cortical reorganisation may explain this result, but as no significant differences were recognised in the motor response of the unaffected limb, differences in functional demands should also be considered.     

SPG4 founder effect in French Canadians with hereditary spastic paraplegia

BACKGROUND: The most common cause of autosomal dominant Hereditary Spastic Paraplegia (HSP) is mutations in the SPG4 gene. We have previously identified novel SPG4 mutations in a collection of North American families including the c.G1801A mutation present in two families from Quebec. The aim of this study is to estimate the frequency of the c.G1801A mutation in the French Canadian (FC) population and to determine whether this mutation originates from a common ancestor. METHODS: We collected and sequenced exon 15 in probands of 37 families. Genotypes of markers flanking the SPG4 gene were used to construct haplotypes in five families. Clinical information was reviewed by a neurologist with expertise in HSP. RESULTS: We have identified three additional unrelated families with the c.G1801A mutation and haplotype analysis revealed that all five families share a common ancestor. The mutation is present in 7% of all our FC families and explains half of our spastin linked FC families. The phenotype associated with the c.G1801A genotype is pure HSP with bladder involvement. CONCLUSION: In this study we have determined that the relative frequency of the c.G1801A mutation in our FC collection is 7%, and approximately 50% in the spastin positive FC group. This mutation is the most common HSP mutation identified in this population to date and is suggestive of a founder effect in Quebec.     

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。     

Evoked potentials in hereditary spastic paraplegia

Pattern reversal visual evoked response (VER) and monaural stimulation of brainstem auditory evoked responses (BAER) were recorded from both sides in 25 patients (males 19; females 6) with hereditary spastic paraplegia (HSP). Their age ranged from 15–52 (mean±SD; 25.2±22.5) years and duration of symptoms 6 months-9 (mean±SD; 4.2±3.6) years. A prolonged P 100 latency was seen in 6 patients and BAER abnormality in 13. None of the patients had clinical evidence of brainstem involvement. It is suggested that VER and BAER abnormalities are due to segmental demyelination and fiber loss in central conduction pathways and could serve as an important tool for the diagnosis of this disorder.

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Sommario I potenziali evocati visivi (VER) e uditivi del tronco (BAER) sono stati registrati bilateralmente in 25 pazienti (19 maschi e 6 femmine) affetti da paraplegia spastica ereditaria (HSP). La loro età media era compresa tra 15 e 52 anni (media±DS=25.2±22.5) e con una durata di malattia compresa tra 6 mesi e 9 anni (media±DS=4.2±3.6). In 6 pazienti è stato riscontrato un aumento della latenza della P100 e in 13 i BAER erano anormali. Nessuno dei pazienti presentava segni clinici di coinvolgimento del tronco. Viene ipotizzato che le anormalità osservate ai VER e BAER sono dovute ad una demielinizzazione segmentaria o a perdita di fibre lungo le vie di conduzione cerebrale. Questi esami strumentali sarebbero quindi di grande utilità nella diagnosi di HSP.

     

Recent advances in hereditary spastic paraplegia

The hereditary spastic paraplegias are a group of rare disorders that are characterized by great clinical and genetic heterogeneity. There has been an exponential increase in the number of HSP loci mapped in recent years, with nine out of the 17 loci reported during the past 2 years. Eight loci have now been identified for the autosomal-dominant form, and seven of these are associated with pure HSP. Spastic paraplegia-4 remains the most frequent locus, and is usually associated with a pure phenotype. Although the corresponding spastin gene was only recently identified, over 50 mutations have been described to date, which renders molecular diagnosis difficult. Five loci are known for autosomal-recessive HSP, and four of these are associated with complex forms, all with different phenotypes. Two genes have been identified: paraplegin and sacsin. Finally, three loci have been identified in X-linked HSP, two of which are complex forms. The genes that encode L1 and PLP were the first to be identified in HSP disorders. Surprisingly, the five genes encode proteins of different families, making understanding and diagnosis of HSP even more difficult. The discovery of new genes should hopefully help to clarify the pathophysiology of these disorders.     

Chinese patients with Machado-Joseph disease presenting with complicated hereditary spastic paraplegia

Background and purpose:  The clinical overlap between Machado-Joseph disease (MJD) and autosomal dominant complicated hereditary spastic paraplegia (AD-HSP) is extensive and the differentiation between them can be difficult on clinical ground. However, patients are seeking the right diagnosis and it is important for neurologists to distinguish them in the early stage.
Methods:  In recent 10 years, we have recruited and followed-up three families which were initially diagnosed as complicated AD-HSP based on the clinical criteria. Mutation analyses of SPG4 , SPG3A and ATXN3 were performed in the index cases.
Results:  No mutations on SPG4 and SPG3A were found. Mutation analysis of ATXN3 showed that these cases have one expanded allele and one normal allele. The copy numbers of CAG repeats were 80/28, 86/28 and 83/33, respectively.
Conclusions:  The molecular diagnosis confirmed that they were MJD patients though they had been misdiagnosed as complicated AD-HSP for many years. The copy numbers of expanded allele were more than 80 and the copy numbers of normal allele were more than 27, which could somewhat explain the earlier onset age of these cases and the anticipation of the pedigrees. Our data emphasize the necessity to perform the mutation analysis of ATXN3 in clinically diagnosed complicated AD-HSP patients.     

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.     

遗传性痉挛性截瘫paraplegin基因的突变分析

目的探讨paraplegin基因在中国人遗传性痉挛性截瘫(HSP或SPG)中的突变特点,为该病的基因诊断奠定基础。方法应用聚合酶链反应单链构象多态性(PCRSSCP)结合DNA序列分析方法,对来自全国8个常染色体隐性遗传HSP家系的先证者和14例散发性HSP患者进行paraplegin基因突变分析。结果所有外显子均可扩出,发现15号外显子上2例先证者出现异常SSCP条带,经DNA序列分析发现2063及2066位点上存在碱基G被A替换,但家系内不存在共分离的现象,且正常对照者也存在G被A替换,考虑为多态,其中G2066A为首次发现。结论Paraplegin基因突变可能在中国人HSP患者中少见。2063G→A及2066G→A是paraplegin基因的两个多态性改变,其中2066G→A为首次发现。     

Non-motor symptoms are relevant and possibly treatable in hereditary spastic paraplegia type 4 (SPG4)

Journal of Neurology - Hereditary spastic paraplegias (HSP) share as cardinal feature progressive spastic gait disorder. SPG4 accounts for about 25% of cases and is caused by mutations in the SPAST...