Disease severity affects quality of life of hereditary spastic paraplegia patients.

BACKGROUND AND PURPOSE: Hereditary spastic paraplegia (HSP) causes progressive gait disturbance because of degeneration of the corticospinal tract. To assess its impact on Health-Related Quality of Life (HRQoL), we analyzed the correlation of HRQoL with disease severity and clinical symptoms in HSP. METHODS: HRQoL was assessed by the Short-Form 36 (SF-36) Mental and Physical Component summary scores (MCS and PCS) in 143 German patients with HSP. Disease severity was assessed by the Spastic Paraplegia Rating Scale (SPRS) and landmarks of walking ability. Patients with 'pure' or 'complicated' HSP were compared. RESULTS: Higher SPRS scores indicating higher disease severity correlated significantly with lower PCS (r = -0.63; P < 0.0005) and MCS (r = -0.38; P < 0.0005) scores. MCS and PCS were reduced in patients with 'complicated' forms compared to 'pure' HSP and with decreasing walking ability. CONCLUSION: HRQoL is substantially impaired in patients with HSP and decreases with disease severity and the presence of 'complicating' symptoms. Patients are most affected by the physical restraints of their disease, but mental health is impaired as well. HRQoL is a valid parameter in HSP that should be considered in upcoming therapeutical trials.

Amplicon-based high-throughput pooled sequencing identifies mutations in CYP7B1 and SPG7 in sporadic spastic paraplegia patients.

Hereditary spastic paraplegia (HSP) is a neurodegenerative disorder defined clinically by progressive lower limb spasticity and weakness. HSP is a genetically highly heterogeneous condition with at least 46 gene loci identified so far, involving X-linked, autosomal recessive (AR) and autosomal dominant inheritance. For correct diagnosis, molecular testing is essential because clinical parameters by themselves are not reliable to differentiate HSP forms. The purpose of this study was to establish amplicon-based high-throughput genotyping for AR-HSP. A sample of 187 index cases with apparently sporadic or recessive spastic paraplegia were analyzed by applying an array-based amplification strategy. Amplicon libraries of the CYP7B1-(SPG5) and SPG7-gene were generated followed by a pooled next-generation sequencing (NGS) approach. We identified three SPG5 and seven SPG7 patients. All had one homozygous or two heterozygous mutations. In total, 20 distinct mutations (CYP7B1,n = 4and SPG7,n = 16) including two novel CYP7B1 mutations (p.G51R and p.E211KfsX3) and eight novel SPG7 mutations (p.Leu8delinsLeuLeu, p.W29X, p.R139X, p.R247X, p.G344D, p.Leu346_Leu347ins11, p.R398X and p.R398Q) were detected by this comprehensive genetic testing. Our study illustrates how amplicon-based NGS can be used as an efficient tool to study genotypes and mutations in large patient cohorts and complex phenotypes.

Evaluating the effect of spastin splice mutations by quantitative allele-specific expression assay.

BACKGROUND: mutations in the SPG4/SPAST gene are the most common cause for hereditary spastic paraplegia (HSP). The splice-site mutations make a significant contribution to HSP and account for 17.4% of all types of mutations and 30.8% of point mutations in the SPAST gene. However, only few studies with limited molecular approach were conducted to investigate and decipher the role of SPAST splice-site mutations in HSP. METHODS: a reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and quantitative allele-specific expression assay were performed. RESULTS: we have characterized the consequence of two novel splice-site mutations (c.1493 + 1G>A and c.1414-1G>A) in the SPAST gene in two different families with pure HSP. The RT-PCR analysis revealed that both spastin mutations are indeed splice-site mutations and cause skipping of exon 12. Furthermore, RT-PCR data suggested that these splice-site mutations may cause leaky splicing. By means of a quantitative allele-specific expression assay, we could confirm that both splice-site mutations cause leaky splicing, as the relative expression of the exon 12-skipped transcript was reduced (21.1 ± 3.6 compared to expected 50%). CONCLUSIONS: our finding supports a "threshold-effect-model" for functional spastin in HSP. A higher level (78.8 ± 3.9%) of functional spastin than the expected ratio of 50% owing to leaky splicing might cause late age at onset of HSP. Remarkably, we could show that a quantitative allele-specific expression assay is a simple and effective tool to evaluate the role of most types of spastin splice-site mutations in HSP.

Frequency and phenotype of SPG11 and SPG15 in complicated hereditary spastic paraplegia.

BACKGROUND: Hereditary spastic paraplegias (HSP) are clinically and genetically highly heterogeneous. Recently, two novel genes, SPG11 (spatacsin) and SPG15 (spastizin), associated with autosomal recessive HSP, were identified. Clinically, both are characterised by complicated HSP and a rather similar phenotype consisting of early onset spastic paraplegia, cognitive deficits, thin corpus callosum (TCC), peripheral neuropathy and mild cerebellar ataxia. OBJECTIVE: To compare the frequency of SPG11 and SPG15 in patients with early onset complicated HSP and to further characterise the phenotype of SPG11 and SPG15. RESULTS: A sample of 36 index patients with early onset complicated HSP and a family history compatible with autosomal recessive inheritance was collected and screened for mutations in SPG11 and SPG15. Overall frequency of SPG11 was 14% (5/36) but was considerably higher in patients with TCC (42%). One patient with mental retardation and thinning of the corpus callosum was compound heterozygous for two novel SPG15 mutations. Additionally, several new polymorphisms and sequence variants of unknown significance have been identified in the SPG15 gene. CONCLUSIONS: TCC seems to be the best phenotypic predictor for SPG11 as well as SPG15. No clinical features could discriminate between SPG11 and SPG15. Therefore, priority of genetic testing should be driven by mutation frequency that appears to be substantially higher in SPG11 than in SPG15.

Autosomal dominant spastic paraplegia with peripheral neuropathy maps to chr12q23-24.

OBJECTIVE: Hereditary spastic paraplegias (HSP) are genetically exceedingly heterogeneous. To date, 37 genetic loci for HSP have been described (SPG1-41), among them 16 loci for autosomal dominant disease. Notwithstanding, further genetic heterogeneity is to be expected in HSP, as various HSP families do not link to any of the known HSP loci. In this study, we aimed to map the disease locus in a German family segregating autosomal dominant complicated HSP. METHODS: A genome-wide linkage analysis was performed using the GeneChip Mapping 10Kv2.0 Xba Array containing 10,204 SNP markers. Suggestive loci were further analyzed by mapping of microsatellite markers. RESULTS: One locus on chromosome 12q23-24, termed SPG36, was confirmed by high density microsatellite fine mapping with a significant LOD score of 3.2. SPG36 is flanked by markers D12S318 and D12S79. Linkage to SPG36 was excluded in >20 additional autosomal dominant HSP families. Candidate genes were selected and sequenced. No disease-causing mutations were identified in the coding regions of ATXN2, HSPB8, IFT81, Myo1H, UBE3B, and VPS29. SPG36 is complicated by a sensory and motor neuropathy; it is therefore the eighth autosomal dominant subtype of complicated HSP. CONCLUSION: We report mapping of a new locus for autosomal dominant hereditary spastic paraplegia (HSP) (SPG36) on chromosome 12q23-24 in a German family with autosomal dominant HSP complicated by peripheral neuropathy.

SPG10 is a rare cause of spastic paraplegia in European families.

BACKGROUND: SPG10 is an autosomal dominant form of hereditary spastic paraplegia (HSP), which is caused by mutations in the neural kinesin heavy chain KIF5A gene, the neuronal motor of fast anterograde axonal transport. Only four mutations have been identified to date. OBJECTIVE: To determine the frequency of SPG10 in European families with HSP and to specify the SPG10 phenotype. PATIENTS AND METHODS: 80 index patients from families with autosomal dominant HSP were investigated for SPG10 mutations by direct sequencing of the KIF5A motor domain. Additionally, the whole gene was sequenced in 20 of these families. RESULTS: Three novel KIF5A mutations were detected in German families, including one missense mutation (c.759G>T, p.K253N), one in frame deletion (c.768_770delCAA, p.N256del) and one splice site mutation (c.217G>A). Onset of gait disturbance varied from infancy to 30 years of age. All patients presented clinically with pure HSP, but a subclinical sensory-motor neuropathy was detected by neurophysiology studies. CONCLUSIONS: SPG10 accounts for approximately 3% of European autosomal dominant HSP families. All mutations affect the motor domain of kinesin and thus most likely impair axonal transport. Clinically, SPG10 is characterised by spastic paraplegia with mostly subclinical peripheral neuropathy.

High frequency of partial SPAST deletions in autosomal dominant hereditary spastic paraplegia.

BACKGROUND: Hereditary spastic paraplegia (HSP) is a genetically heterogeneous neurodegenerative disease. The most frequent cause of autosomal dominant HSP is mutation of SPAST (SPG4 locus), but additional pedigrees remain mutation negative by conventional screening despite linkage to SPG4. OBJECTIVE: To determine the frequency of genomic copy number aberrations of SPAST in autosomal dominant HSP. METHODS: We developed and validated a multiplex ligation-dependent probe amplification assay targeting SPAST and SPG3A, another gene frequently involved in autosomal dominant HSP. In a multicenter study we subsequently investigated 65 index patients with autosomal dominant HSP, all of whom had previously been screened negative for SPAST mutations. Independent secondary samples, additional family members, and cDNA were analyzed to confirm positive findings. RESULTS: Aberrant MLPA profiles were identified in 12 cases (18%). They exclusively affect SPAST, represent deletions, segregate with the disease, and are largely pedigree specific. Internal SPAST deletions entail expression of correspondingly shortened transcripts, which vary in stability. Age at onset in SPAST deletion carriers does not differ from that associated with other SPAST mutations. CONCLUSIONS: Partial SPAST deletions, but not SPAST amplifications and SPG3A copy number aberrations, represent an underestimated cause of autosomal dominant hereditary spastic paraplegia. Partial SPAST deletions are likely to act via haploinsufficiency.

The Spastic Paraplegia Rating Scale (SPRS): a reliable and valid measure of disease severity.

OBJECTIVE: To develop and evaluate a clinical Spastic Paraplegia Rating Scale (SPRS) to measure disease severity and progression. METHODS: A 13-item scale was designed to rate functional impairment occurring in pure forms of spastic paraplegia (SP). Additional symptoms constituting a complicated form of SP are recorded in an inventory. Two independent patient cohorts were evaluated in a two-step validation procedure. RESULTS: Application of SPRS requires less than 15 minutes and does not require any special equipment, so it is suitable for an outpatient setting. Interrater agreement of SPRS was high (intraclass correlation coefficient = 0.99). Reliability was further supported by high internal consistency (Cronbach alpha = 0.91). SPRS values were almost normally distributed without apparent floor or ceiling effect. Construct validity was shown by high correlation of SPRS to Barthel Index and the International Cooperative Ataxia Rating Scale (convergent validity) and low correlation to Mini-Mental Status Examination (discriminant validity). CONCLUSION: The Spastic Paraplegia Rating Scale is a reliable and valid measure of disease severity.

Motor system abnormalities in hereditary spastic paraparesis type 4 (SPG4) depend on the type of mutation in the spastin gene.

BACKGROUND: Hereditary spastic paraparesis (HSP) denotes a group of inherited neurological disorders with progressive lower limb spasticity as their clinical hallmark; a large proportion of autosomal dominant HSP belongs to HSP type 4, which has been linked to the SPG4 locus on chromosome 2. A variety of mutations have been identified within the SPG4 gene product, spastin. OBJECTIVE: Correlation of genotype and electrophysiological phenotype. MATERIAL: Two large families with HSP linked to the SPG4 locus with a very similar disease with respect to age of onset, progression, and severity of symptoms. METHODS: Mutation analysis was performed by PCR from genomic DNA and cDNA, and direct sequencing. The motor system was evaluated using transcranial magnetic stimulation. RESULTS: Patients differ in several categories depending on the type of mutation present. CONCLUSIONS: For the first time in hereditary spastic paraparesis, a phenotypic correlate of a given genetic change in the spastin gene has been shown.

Mutation analysis of the spastin gene (SPG4) in patients in Germany with autosomal dominant hereditary spastic paraplegia.

Hereditary spastic paraplegias (HSP) comprise a genetically and clinically heterogeneous group of neurodegenerative disorders characterized by progressive spasticity and hyperreflexia of the lower limbs. Autosomal dominant hereditary spastic paraplegia 4 linked to chromosome 2p (SPG4) is the most common form of autosomal dominant hereditary spastic paraplegia. It is caused by mutations in the SPG4 gene encoding spastin, a member of the AAA protein family of ATPases. In this study the spastin gene of HSP patients from 161 apparently unrelated families in Germany was analyzed. The authors identified mutations in 27 out of the 161 HSP families; 23 of these mutations have not been described before and only one mutation was found in two families. Among the detected mutations are 14 frameshift, four nonsense, and four missense mutations, one large deletion spanning several exons, as well as four mutations that affect splicing. Most of the novel mutations are located in the conserved AAA cassette-encoding region of the spastin gene. The relative frequency of spastin gene mutations in an unselected group of German HSP patients is approximately 17%. Frameshift mutations account for the majority of SPG4 mutations in this population. The proportion of splice mutations is considerably lower than reported elsewhere.