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.     

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.     

A new locus (SPG46) maps to 9p21.2-q21.12 in a Tunisian family with a complicated autosomal recessive hereditary spastic paraplegia with mental impairment and thin corpus callosum

Hereditary spastic paraplegia (HSP) with thin corpus callosum (TCC) and mental impairment is a frequent subtype of complicated HSP, often inherited as an autosomal recessive (AR) trait. It is clear from molecular genetic analyses that there are several underlying causes of this syndrome, with at least six genetic loci identified to date. However, SPG11 and SPG15 are the two major genes for this entity. To map the responsible gene in a large AR-HSP-TCC family of Tunisian origin, we investigated a consanguineous family with a diagnosis of AR-HSP-TCC excluded for linkage to the SPG7, SPG11, SPG15, SPG18, SPG21, and SPG32 loci. A genome-wide scan was undertaken using 6,090 SNP markers covering all chromosomes. The phenotypic presentation in five patients was suggestive of a complex HSP that associated an early-onset spastic paraplegia with mild handicap, mental deterioration, congenital cataract, cerebellar signs, and TCC. The genome-wide search identified a single candidate region on chromosome 9, exceeding the LOD score threshold of +3. Fine mapping using additional markers narrowed the candidate region to a 45.1-Mb interval (15.4 cM). Mutations in three candidate genes were excluded. The mapping of a novel AR-HSP-TCC locus further demonstrates the extensive genetic heterogeneity of this condition. We propose that testing for this locus should be performed, after exclusion of mutations in SPG11 and SPG15 genes, in AR-HSP-TCC families, especially when cerebellar ataxia and cataract are present.     

Partial SPAST and DPY30 deletions in a Japanese spastic paraplegia type 4 family

Spastic paraplegia type 4 (SPG4) is the most common autosomal dominant hereditary SPG caused by mutations in the SPAST gene. We studied the four-generation pedigree of a Japanese family with autosomal dominant hereditary SPG both clinically and genetically. Twelve available family members (ten affected; two unaffected) and two spouses were enrolled in the study. The clinical features were hyperreflexia in all four limbs, spasticity of the lower extremities, impaired vibration sense, mild cognitive impairment confirmed by the Wechsler Adult Intelligence Scale—Third Edition, and peripheral neuropathy confirmed by neurophysiological examinations. All four female patients experienced miscarriages. The cerebrospinal fluid tau levels were mildly increased in two of three patients examined. Linkage analyses revealed the highest logarithm of odds score of 2.64 at 2p23-p21 where the SPAST gene is located. Mutation scanning of the entire exonic regions of the SPAST gene by direct sequencing revealed no mutations. Exonic copy number analysis by real-time quantitative polymerase chain reaction revealed heterozygous deletion of exons 1 to 4 of the SPAST gene. Breakpoint analysis showed that the centromeric breakpoint was located within intron 4 of SPAST while the telomeric breakpoint was located within intron 3 of the neighboring DPY30 gene, causing a deletion of approximately 70?kb ranging from exons 1 to 3 of DPY30 to exons 1 to 4 of SPAST. To our knowledge, this is the first report of SPG4 associated with partial deletions of both the SPAST and DPY30 genes. The partial heterozygous deletion of DPY30 could modify the phenotypic expression of SPG4 patients with this pedigree.     

Mutation analysis of the SPG4 gene in Italian patients with pure and complicated forms of spastic paraplegia

Mutations in the SPG4 gene are the most common causes of hereditary spastic paraplegia (HSP) accounting for up to 40% of autosomal dominant (AD) forms and 12–18% of sporadic cases. The phenotype associated with HSP due to mutations in the SPG4 gene tends to be pure. There is increasing evidence, however, of patients with complicated forms of spastic paraplegia in which SPG4 mutations were identified. A cohort of 38 unrelated Italian patients with spastic paraplegia, of which 24 had a clear dominant inheritance and 14 were apparently sporadic, were screened for mutations in the SPG4 gene.We identified 11 different mutations, six of which were novel (p.Glu143GlyfsX8, p.Tyr415X, p.Asp548Asn, c.1656_1664delinsTGACCT, c.1688-3C>G and c.*2G>T) and two exon deletions previously reported. The overall rate of SPG4 gene mutation in our patients was 36.8% (14/38); in AD-HSP we observed a mutation frequency of 45.8% (11/24), in sporadic cases the frequency was 21.4% (3/14). Furthermore, we found a mutational rate of 22.2% (2/9) and 41.4% (12/29) in the complicated and pure forms, respectively. The results underlie the importance of genetic testing in all affected individuals.     

A case of spastic paraplegia-15 with a novel pathogenic variant in ZFYVE26 gene

Abstract

Hereditary spastic paraplegia (HSP) is a group of rare neurodegenerative disorder with genetic and clinical heterogeneity. It has autosomal dominant (AD), autosomal recessive (AR) and X-linked forms. HSPs are clinically classified into ‘pure’ and ‘complicated’ (complex) forms. SPG11 (KIAA1840) and SPG15 (ZFYVE26) are the most common ARHSPs with thin corpus callosum (TCC). They typically present with early cognitive impairment in childhood followed by gait impairment and spasticity in the second and third decades of life. Here, we present a patient girl, born to a couple who were first cousins, was admitted to the pediatric neurology outpatient clinic at 14?years of age because of walking with help, dysarthria and forgetfulness. Her examination revealed a motor mental retardation, bilateral leg spasticity, increased deep tendon reflexes in lower limbs, bilateral pigmentary retinopathy; TCC and white matter hyperintensities on brain MRI, sensorimotor axonal polyneuropathy findings in lower limbs on electromyography. Based on the clinical features and the imaging studies, the diagnosis of HSP was suspected. Targeted next generation sequencing (NGS) was performed using Inherited NGS Panel that consists of 579 gene associated with Mendelian disorders. Analysis of the patient revealed a c.6398_6401delGGGA(p.Arg2133Asnfs*15)(Exon35) homozygous novel change in ZFYVE26 gene. Genotype-phenotype correlation of HSP is complicated due to heterogeneity. The clinical similarity of HSP types increases the importance of genetic diagnosis. There are few reports about pathogenic variants in ZFYVE26 gene in the literature. This case report is one of the few studies that revealed a novel pathogenic variant in ZFYVE26 gene using NGS.     

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.     

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.     

Screening for the hereditary spastic paraplaegias SPG4 and SPG3A with the multiplex ligation-dependent probe amplification technique in a large population of affected individuals

Hereditary spastic paraplaegias are a group of clinically and genetically heterogeneous neurodegenerative disorders characterised by progressive spasticity and weakness in the lower limbs. The most common forms of hereditary spastic paraplaegia are SPG4 and SPG3A caused by sequence variants in the SPAST and ATL1 genes, as well as by deletions and duplications not detected by standard techniques. In this study, we used the multiplex ligation-dependent probe amplification (MLPA) analysis for screening 93 patients (52 familial and 41 isolated cases). As a result, we identified 11 different deletions and 1 duplication in the SPAST gene and a single exon deletion in the ATL1 gene. These results indicate that micro-rearrangements in the SPAST gene are a fairly frequent cause of hereditary spastic paraplaegia and that MLPA is a useful and efficient technique to detect a considerable proportion of the mutations in the most common forms of hereditary spastic paraplaegias.     

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.     

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.     

Novel SPG3A and SPG4 mutations in dominant spastic paraplegia families

Objectives – The hereditary spastic paraplegias (HSP) are a genetically and clinically heterogeneous group of neurodegenerative disorders, mainly characterized by a progressive spasticity and weakness of the lower limbs. Mutations in the SPG4 and SPG3A genes are responsible for approximately 50% of autosomal dominant HSP. To genetically diagnose the Portuguese families with HSP, mutation analysis was performed for the SPG4 and SPG3A genes. Patients and methods – Analysis was performed by polymerase chain reaction, followed by denaturing high performance liquid chromatography (DHPLC), in 61 autosomal dominant (AD)‐HSP families and 19 unrelated patients without family history. Results – Ten novel mutations were identified: one in the SPG3A and nine in the SPG4 genes; three known mutations in the SPG4 were also found. Most of the novel mutations were frameshift or nonsense (80%), resulting in a dysfunctional protein. Conclusions – The SPG4 and SPG3A analysis allowed the identification of 10 novel mutations and the genetic diagnosis of approximately a quarter of our AD‐HSP families.     

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.     

Sensory ataxia as a prominent clinical presentation in three families with mutations in CYP7B1

Pathogenic mutations in CYP7B1 account for SPG5, an autosomal recessive hereditary spastic paraplegia characterized by a complex phenotype including visual problems and cerebellar dysfunction. Sensory ataxia is not usually regarded as a typical clinical feature of SPG5. The purpose of this study was to describe six patients showing features of sensory ataxia as the prominent and/or initial symptoms of SPG5. Six patients from three distinct pedigrees (three women, three men; age 49.5 ± 18.2 years), all presenting gait unsteadiness and frequent falls since childhood, underwent clinical and molecular investigations. All showed marked sensory ataxic gait with positive Romberg's sign, as well as severely impaired position and vibration sense. Comparatively minor signs of pyramidal involvement were also detected. In four of the patients, brain MRI showed white matter hyperintensities on T2-weighted images. An already reported homozygous c.889A>G (p.T297A) mutation in SPG5/CYP7B1 was found in five patients from two families, whereas the remaining case harbored the novel c.250_251delC/p.L84Ffs*6 and c.266A>C/p.Y89S variants. Marked and enduring sensory ataxia can be a pivotal sign in SPG5, and expands the phenotypic spectrum associated with mutations in CYP7B1.     

Hereditary spastic paraplegia with mental impairment and thin corpus callosum in Tunisia: SPG11, SPG15, and further genetic heterogeneity

OBJECTIVE: To perform a clinical and genetic study of Tunisian families with autosomal recessive (AR) hereditary spastic paraplegia with thin corpus callosum (HSP-TCC). DESIGN: Linkage studies and mutation screening. SETTING: Reference Center for Neurogenetics in South and Center Tunisia. PARTICIPANTS: Seventy-three subjects from 33 "apparently" unrelated Tunisian families with AR HSP. MAIN OUTCOME MEASURES: Families with AR HSP-TCC were subsequently tested for linkage to the corresponding loci using microsatellite markers from the candidate intervals, followed by direct sequencing of the KIAA1840 gene in families linked to SPG11. RESULTS: We identified 8 Tunisian families (8 of 33 [24%]), including 19 affected patients, fulfilling the clinical criteria for HSP-TCC. In 7 families, linkage to either SPG11 (62.5%) or SPG15 (25%) was suggested by haplotype reconstruction and positive logarithm of odds score values for microsatellite markers. The identification of 2 recurrent mutations (R2034X and M245VfsX) in the SPG11 gene in 5 families validated the linkage results. The neurological and radiological findings in SPG11 and SPG15 patients were relatively similar. The remaining family, characterized by an earlier age at onset and the presence of cataracts, was excluded for linkage to the 6 known loci, suggesting further genetic heterogeneity. CONCLUSIONS: Autosomal recessive HSP-TCC is a frequent subtype of complicated HSP in Tunisia and is clinically and genetically heterogeneous. SPG11 and SPG15 are the major loci for this entity, but at least another genetic form with unique clinical features exists.     

ATL1 and REEP1 mutations in hereditary and sporadic upper motor neuron syndromes

SPAST mutations are the most common cause of autosomal dominant hereditary spastic paraplegias (AD-HSPs), but many spastic paraplegia patients are found to carry no mutations in this gene. In order to assess the contribution of ATL1 and REEP1 in AD-HSP, we performed mutational analysis in 27 SPAST-negative AD-HSP families. We found three novel ATL1 mutations and one REEP1 mutation in five index-patients. In 110 patients with sporadic adult-onset upper motor neuron syndromes, a novel REEP1 mutation was identified in one patient. Apart from a significantly younger age at onset in ATL1 patients and restless legs in some, the clinical phenotype of ATL1 and REEP1 was similar to other pure AD-HSPs.     

A de novo SPAST mutation leading to somatic mosaicism is associated with a later age at onset in HSP

SPG4/SPAST, the gene-encoding spastin, is responsible for the most frequent form of autosomal dominant hereditary spastic paraplegia (HSP). SPG4-HSP is a heterogeneous disorder characterized by both interfamilial and intrafamilial variation, especially regarding the severity and the age at onset. In this study, we investigated the origin of the mutation and the factors involved in intra-familial heterogeneity in a family with a SPG4 mutation. We demonstrated that the mutation occurred de novo and show evidence of somatic mosaicism in the grandfather, who was the only affected member of six siblings. His disease began at age 55, much later than in his daughter, who had onset at age 18, and his grandson, in whom onset was at age 5. These observations indicate that de novo mutations can occur in SPG4, and that somatic mosaicism might account for intra-familial variation in SPG4-linked HSP.     

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.