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

Spinocerebellar ataxia types 1, 2, 3, and 6: disease severity and nonataxia symptoms.

OBJECTIVE: To identify factors that determine disease severity and clinical phenotype of the most common spinocerebellar ataxias (SCAs), we studied 526 patients with SCA1, SCA2, SCA3. or SCA6. METHODS: To measure the severity of ataxia we used the Scale for the Assessment and Rating of Ataxia (SARA). In addition, nonataxia symptoms were assessed with the Inventory of Non-Ataxia Symptoms (INAS). The INAS count denotes the number of nonataxia symptoms in each patient. RESULTS: An analysis of covariance with SARA score as dependent variable and repeat lengths of the expanded and normal allele, age at onset, and disease duration as independent variables led to multivariate models that explained 60.4% of the SARA score variance in SCA1, 45.4% in SCA2, 46.8% in SCA3, and 33.7% in SCA6. In SCA1, SCA2, and SCA3, SARA was mainly determined by repeat length of the expanded allele, age at onset, and disease duration. The only factors determining the SARA score in SCA6 were age at onset and disease duration. The INAS count was 5.0 +/- 2.3 in SCA1, 4.6 +/- 2.2 in SCA2, 5.2 +/- 2.5 in SCA3, and 2.0 +/- 1.7 in SCA6. In SCA1, SCA2, and SCA3, SARA score and disease duration were the strongest predictors of the INAS count. In SCA6, only age at onset and disease duration had an effect on the INAS count. CONCLUSIONS: Our study suggests that spinocerebellar ataxia (SCA) 1, SCA2, and SCA3 share a number of common biologic properties, whereas SCA6 is distinct in that its phenotype is more determined by age than by disease-related factors

Consensus Paper: Neurophysiological Assessments of Ataxias in Daily Practice

The purpose of this consensus paper is to review electrophysiological abnormalities and to provide a guideline of neurophysiological assessments in cerebellar ataxias. All authors agree that standard electrophysiological methods should be systematically applied in all cases of ataxia to reveal accompanying peripheral neuropathy, the involvement of the dorsal columns, pyramidal tracts and the brainstem. Electroencephalography should also be considered, although findings are frequently non-specific. Electrophysiology helps define the neuronal systems affected by the disease in an individual patient and to understand the phenotypes of the different types of ataxia on a more general level. As yet, there is no established electrophysiological measure which is sensitive and specific of cerebellar dysfunction in ataxias. The authors agree that cerebellar brain inhibition (CBI), which is based on a paired-pulse transcranial magnetic stimulation (TMS) paradigm assessing cerebellar-cortical connectivity, is likely a useful measure of cerebellar function. Although its role in the investigation and diagnoses of different types of ataxias is unclear, it will be of interest to study its utility in this type of conditions. The authors agree that detailed clinical examination reveals core features of ataxia (i.e., dysarthria, truncal, gait and limb ataxia, oculomotor dysfunction) and is sufficient for formulating a differential diagnosis. Clinical assessment of oculomotor function, especially saccades and the vestibulo-ocular reflex (VOR) which are most easily examined both at the bedside and with quantitative testing techniques, is of particular help for differential diagnosis in many cases. Pure clinical measures, however, are not sensitive enough to reveal minute fluctuations or early treatment response as most relevant for pre-clinical stages of disease which might be amenable to study in future intervention trials. The authors agree that quantitative measures of ataxia are desirable as biomarkers. Methods are discussed that allow quantification of ataxia in laboratory as well as in clinical and real-life settings, for instance at the patients' home. Future studies are needed to demonstrate their usefulness as biomarkers in pharmaceutical or rehabilitation trials

Deep Mining of Oxysterols and Cholestenoic Acids in Human Plasma and Cerebrospinal Fluid: Quantification using Isotope Dilution Mass Spectrometry

Both plasma and cerebrospinal fluid (CSF) are rich in cholesterol and its metabolites. Here we describe in detail a methodology for the identification and quantification of multiple sterols including oxysterols and sterol-acids found in these fluids. The method is translatable to any laboratory with access to liquid chromatography – tandem mass spectrometry. The method exploits isotope-dilution mass spectrometry for absolute quantification of target metabolites. The method is applicable for semi-quantification of other sterols for which isotope labelled surrogates are not available and approximate quantification of partially identified sterols. Values are reported for non-esterified sterols in the absence of saponification and total sterols following saponification. In this way absolute quantification data is reported for 17 sterols in the NIST SRM 1950 plasma along with semi-quantitative data for 8 additional sterols and approximate quantification for one further sterol. In a pooled (CSF) sample used for internal quality control, absolute quantification was performed on 10 sterols, semi-quantification on 9 sterols and approximate quantification on a further three partially identified sterols. The value of the method is illustrated by confirming the sterol phenotype of a patient suffering from ACOX2 deficiency, a rare disorder of bile acid biosynthesis, and in a plasma sample from a patient suffering from cerebrotendinous xanthomatosis, where cholesterol 27-hydroxylase is deficient

Mechanistic basis of an epistatic interaction reducing age at onset in hereditary spastic paraplegia

Many genetic neurological disorders exhibit variable expression within affected families, often exemplified by variations in disease age at onset. Epistatic effects (i.e. effects of modifier genes on the disease gene) may underlie this variation, but the mechanistic basis for such epistatic interactions is rarely understood. Here we report a novel epistatic interaction between SPAST and the contiguous gene DPY30, which modifies age at onset in hereditary spastic paraplegia, a genetic axonopathy. We found that patients with hereditary spastic paraplegia caused by genomic deletions of SPAST that extended into DPY30 had a significantly younger age at onset. We show that, like spastin, the protein encoded by SPAST, the DPY30 protein controls endosomal tubule fission, traffic of mannose 6-phosphate receptors from endosomes to the Golgi, and lysosomal ultrastructural morphology. We propose that additive effects on this pathway explain the reduced age at onset of hereditary spastic paraplegia in patients who are haploinsufficient for both genes.This work was supported by grants to E.R.; Project Grant from United States Spastic Paraplegia Foundation, UK Medical Research Council Project Grant [MR/M00046X/1], Project grant from NIHR Biomedical Research Centre at Addenbrooke’s Hospital, Wellcome Trust Senior Research Fellowship in Clinical Science [082381], Project Grant from Tom Wahlig Stiftung (project 33). J.E. and P.M. are supported by a Wellcome Trust Principal Research Fellowship Grant to Margaret S. Robinson [086598]. T.M.N. was supported by an MRC PhD studentship [G0800117]. B.W. is supported by the Tom Wahlig Advanced Fellowship, the German Federal Ministry of Education and Research (BMBF, 01GQ113), the Bavarian Ministry of Education and Culture, Sciences and Arts in the framework of the Bavarian Molecular Biosystems Research Network and ForIPS, and the Interdisciplinary Centre for Clinical Research (IZKF, University Hospital of Erlangen, N3 and F3). T.R. was supported by research grant DFG GRK2162/1 of the Deutsche Forschungsgemeinschaft. The study was also supported by the European Union within the 7th European Community Framework Program for Research and Technological Development through funding for the NEUROMICS network (F5-2012-305121 to L.S. and A.D.), the E-Rare Network NEUROLIPID (01GM1408B to R.S. and ANR-13-RARE-0003-02 to G.S.), and a Marie Curie International Outgoing Fellowship (grant PIOF-GA-2012-326681 to R.S. and L.S.). This work was further supported by the US National Institutes of Health (NIH) (grant 5R01NS072248 to R.S.), the German HSP-Selbsthilfegruppe e.V. (grant to R.S. and L.S.), and grants to C.B.: Project Grant from Tom Wahlig Stiftung (project 20), grant from the Stiftung für Pathobiochemie und Molekulare Diagnostik. CIMR is supported by a Wellcome Trust Strategic Award [100140] and Equipment Grant [093026]

Exon deletions and intragenic insertions are not rare in ataxia with oculomotor apraxia 2

<p>Abstract</p> <p>Background</p> <p>The autosomal recessively inherited ataxia with oculomotor apraxia 2 (AOA2) is a neurodegenerative disorder characterized by juvenile or adolescent age of onset, gait ataxia, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia, and elevated serum AFP levels. AOA2 is caused by mutations within the senataxin gene (<it>SETX</it>). The majority of known mutations are nonsense, missense, and splice site mutations, as well as small deletions and insertions.</p> <p>Methods</p> <p>To detect mutations in patients showing a clinical phenotype consistent with AOA2, the coding region including splice sites of the <it>SETX </it>gene was sequenced and dosage analyses for all exons were performed on genomic DNA. The sequence of cDNA fragments of alternative transcripts isolated after RT-PCR was determined.</p> <p>Results</p> <p>Sequence analyses of the <it>SETX </it>gene in four patients revealed a heterozygous nonsense mutation or a 4 bp deletion in three cases. In another patient, PCR amplification of exon 11 to 15 dropped out. Dosage analyses and breakpoint localisation yielded a 1.3 kb LINE1 insertion in exon 12 (patient P1) and a 6.1 kb deletion between intron 11 and intron 14 (patient P2) in addition to the heterozygous nonsense mutation R1606X. Patient P3 was compound heterozygous for a 4 bp deletion in exon 10 and a 20.7 kb deletion between intron 10 and 15. This deletion was present in a homozygous state in patient P4.</p> <p>Conclusion</p> <p>Our findings indicate that gross mutations seem to be a frequent cause of AOA2 and reveal the importance of additional copy number analysis for routine diagnostics.</p

Deep mining of oxysterols and cholestenoic acids in human plasma and cerebrospinal fluid: Quantification using isotope dilution mass spectrometry

Both plasma and cerebrospinal fluid (CSF) are rich in cholesterol and its metabolites. Here we describe in detail a methodology for the identification and quantification of multiple sterols including oxysterols and sterol-acids found in these fluids. The method is translatable to any laboratory with access to liquid chromatography – tandem mass spectrometry. The method exploits isotope-dilution mass spectrometry for absolute quantification of target metabolites. The method is applicable for semi-quantification of other sterols for which isotope labelled surrogates are not available and approximate quantification of partially identified sterols. Values are reported for non-esterified sterols in the absence of saponification and total sterols following saponification. In this way absolute quantification data is reported for 17 sterols in the NIST SRM 1950 plasma along with semi-quantitative data for 8 additional sterols and approximate quantification for one further sterol. In a pooled (CSF) sample used for internal quality control, absolute quantification was performed on 10 sterols, semi-quantification on 9 sterols and approximate quantification on a further three partially identified sterols. The value of the method is illustrated by confirming the sterol phenotype of a patient suffering from ACOX2 deficiency, a rare disorder of bile acid biosynthesis, and in a plasma sample from a patient suffering from cerebrotendinous xanthomatosis, where cholesterol 27-hydroxylase is deficient

Prediction of the disease course in Friedreich ataxia

We explored whether disease severity of Friedreich ataxia can be predicted using data from clinical examinations. From the database of the European Friedreich Ataxia Consortium for Translational Studies (EFACTS) data from up to five examinations of 602 patients with genetically confirmed FRDA was included. Clinical instruments and important symptoms of FRDA were identified as targets for prediction, while variables such as genetics, age of disease onset and first symptom of the disease were used as predictors. We used modelling techniques including generalised linear models, support-vector-machines and decision trees. The scale for rating and assessment of ataxia (SARA) and the activities of daily living (ADL) could be predicted with predictive errors quantified by root-mean-squared-errors (RMSE) of 6.49 and 5.83, respectively. Also, we were able to achieve reasonable performance for loss of ambulation (ROC-AUC score of 0.83). However, predictions for the SCA functional assessment (SCAFI) and presence of cardiological symptoms were difficult. In conclusion, we demonstrate that some clinical features of FRDA can be predicted with reasonable error; being a first step towards future clinical applications of predictive modelling. In contrast, targets where predictions were difficult raise the question whether there are yet unknown variables driving the clinical phenotype of FRDA

Progression characteristics of the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS): a 4-year cohort study

BACKGROUND: The European Friedreich's Ataxia Consortium for Translational Studies (EFACTS) investigates the natural history of Friedreich's ataxia. We aimed to assess progression characteristics and to identify patient groups with differential progression rates based on longitudinal 4-year data to inform upcoming clinical trials in Friedreich's ataxia. METHODS: EFACTS is a prospective, observational cohort study based on an ongoing and open-ended registry. Patients with genetically confirmed Friedreich's ataxia were seen annually at 11 clinical centres in seven European countries (Austria, Belgium, France, Germany, Italy, Spain, and the UK). Data from baseline to 4-year follow-up were included in the current analysis. Our primary endpoints were the Scale for the Assessment and Rating of Ataxia (SARA) and the activities of daily living (ADL). Linear mixed-effect models were used to analyse annual disease progression for the entire cohort and subgroups defined by age of onset and ambulatory abilities. Power calculations were done for potential trial designs. This study is registered with ClinicalTrials.gov, NCT02069509. FINDINGS: Between Sept 15, 2010, and Nov 20, 2018, of 914 individuals assessed for eligibility, 602 patients were included. Of these, 552 (92%) patients contributed data with at least one follow-up visit. Annual progression rate for SARA was 0·82 points (SE 0·05) in the overall cohort, and higher in patients who were ambulatory (1·12 [0·07]) than non-ambulatory (0·50 [0·07]). ADL worsened by 0·93 (SE 0·05) points per year in the entire cohort, with similar progression rates in patients who were ambulatory (0·94 [0·07]) and non-ambulatory (0·91 [0·08]). Although both SARA and ADL showed slightly greater worsening in patients with typical onset (symptom onset at ≤24 years) than those with late onset (symptom onset ≥25 years), differences in progression slopes were not significant. For a 2-year parallel-group trial, 230 (115 per group) patients would be required to detect a 50% reduction in SARA progression at 80% power: 118 (59 per group) if only individuals who are ambulatory are included. With ADL as the primary outcome, 190 (95 per group) patients with Friedreich's ataxia would be needed, and fewer patients would be required if only individuals with early-onset are included. INTERPRETATION: Our findings for stage-dependent progression rates have important implications for clinicians and researchers, as they provide reliable outcome measures to monitor disease progression, and enable tailored sample size calculation to guide upcoming clinical trial designs in Friedreich's ataxia. FUNDING: European Commission, Voyager Therapeutics, and EuroAtaxia