Publications by authors named "Ludger Schöls"

282 Publications

The European Reference Network for Rare Neurological Diseases.

Front Neurol 2020 14;11:616569. Epub 2021 Jan 14.

Institute for Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany.

While rare diseases (RDs) are by definition of low prevalence, the total number of patients suffering from an RD is high, and the majority of them have neurologic manifestations, involving central, peripheral nerve, and muscle. In 2017, 24 European Reference Networks (ERNs), each focusing on a specific group of rare or low-prevalence complex diseases, were formed to improve the care for patients with an RD. One major aim is to have "the knowledge travel instead of the patient," which has been put into practice by the implementation of the Clinical Patient Management System (CPMS) that enables clinicians to perform pan-European virtual consultations. The European Reference Network for Rare Neurological Diseases (ERN-RND) provides an infrastructure for knowledge sharing and care coordination for patients affected by a rare neurological disease (RND) involving the most common central nervous system pathological conditions. It covers the following disease groups: (i) Cerebellar Ataxias and Hereditary Spastic Paraplegias; (ii) Huntington's disease and Other Choreas; (iii) Frontotemporal dementia; (iv) Dystonia, (non-epileptic) paroxysmal disorders, and Neurodegeneration with Brain Iron Accumulation; (v) Leukoencephalopathies; and (vi) Atypical Parkinsonian Syndromes. At the moment, it unites 32 expert centers and 10 affiliated partners in 21 European countries, as well as patient representatives, but will soon cover nearly all countries of the European Union as a result of the ongoing expansion process. Disease expert groups developed and consented on diagnostic flowcharts and disease scales to assess the different aspects of RNDs. ERN-RND has started to discuss diagnostically unclear patients in the CPMS, is one of four ERNs that serve as foundation of Solve-RD, and has established an RND training and education program. The network will facilitate trial readiness through the establishment of an ERN-RND registry with a minimal data of all patients seen at the ERN-RND centers, thus providing a unique overview of existing genotype-based cohorts. The overall aim of the ERNs is to improve access for patients with RDs to quality diagnosis, care, and treatment. Based on this objective, ERNs are monitored by the European Commission on a regular basis to provide transparency and reassurance to the RD community and the general public.
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http://dx.doi.org/10.3389/fneur.2020.616569DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840612PMC
January 2021

Natural History, Phenotypic Spectrum, and Discriminative Features of Multisystemic RFC1 Disease.

Neurology 2021 Mar 25;96(9):e1369-e1382. Epub 2021 Jan 25.

From the Department of Neurodegenerative Diseases (A.T., S.R., L.S., M. Synofzik), Hertie-Institute for Clinical Brain Research and Center of Neurology, and German Center for Neurodegenerative Diseases (DZNE) (A.T., S.R., L.S., M. Synofzik), University of Tübingen, Germany; MRC Centre for Neuromuscular Diseases (A.C., N.D., H.H.), Department of Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, UCL Queen Square Institute of Neurology, London, UK; Department of Brain and Behaviour Sciences (A.C.), University Pavia, Italy; Department of Neurology (J.F., T.K.), University Hospital Bonn; German Center for Neurodegenerative Diseases (DZNE) (J.F., H.J., T.K.), Bonn; Department of Neurology (H.J.), University Hospital of Heidelberg; Department of Psychiatry, Psychotherapy and Psychosomatics (A.M.H., D.R.), University of Halle, Germany; Département de Neurologie (S.M., M.A.), Hôpital de Hautepierre, Hôpitaux Universitaires de Strasbourg; Department of Neurology (A.E.-L.), APHP, CHU de Bicêtre; French National Reference Center for Rare Neuropathies (NNERF) (A.E.-L.); Inserm U1195 and Paris-Sud University (A.E.-L.), Le Kremlin Bicêtre, France; Medical Faculty (S.E.), Department of Neurology, Uludag University, Bursa, Turkey; University of Zurich (V.C.S., A.A.T.); Department of Neurology (V.C.S., A.A.T.), University Hospital Zurich, Switzerland; Institute of Medical Genetics and Applied Genomics (M. Sturm, T.B.H.) and Center for Rare Diseases (T.B.H.), University of Tübingen, Germany; Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC) (N.V.-D., H.P.); INSERM (N.V.-D., H.P.), U1258; CNRS (N.V.-D., H.P.), UMR7104, Illkirch; Université de Strasbourg (H.P.), France; Department of Neurology (B.P.v.d.W.), Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, the Netherlands; Department of Neurology (M.P.), Karolinska University Hospital; Department of Clinical Neuroscience (M.P.), Karolinska Institute, Stockholm, Sweden; Department of Neurology (D.T.), Essen University Hospital, University of Duisburg-Essen, Essen; Department of Medical Statistics (R.-D.H.), RWTH Aachen University, Germany; Department of Neurology (J.G.), Hospital Universitario Miguel Servet. Zaragoza, Spain; Department of Neurology (M. Strupp), University Hospital, and German Center for Vertigo and Balance Disorders (M.Strupp), Ludwig Maximilians University, Munich, Germany; Neurology Service (G.M.), Hospital Unversitario Central de Asturias (HUCA), SESPA, Oviedo, Spain; Department of Neurosciences and Reproductive and Odontostomatological Sciences (A.F.), Federico II University Naples, Italy; Institute of Genetics and Molecular and Cellular Biology (M.A.), INSERM-U964/CNRS-UMR7104, University of Strasbourg, Illkirch; Strasbourg Federation of Translational Medicine (M.A.), University of Strasbourg, Strasbourg, France; Service of Neurology (J.I.), University Hospital "Marqués de Valdecilla (IDIVAL)," University of Cantabria, "Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED)," Santander, Spain; and Suna and Inan Kıraç Foundation (A.N.B.), Neurodegeneration Research Laboratory, KUTTAM, Koç University School of Medicine, Istanbul, Turkey.

Objective: To delineate the full phenotypic spectrum, discriminative features, piloting longitudinal progression data, and sample size calculations of replication factor complex subunit 1 (RFC1) repeat expansions, recently identified as causing cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS).

Methods: Multimodal repeat screening (PCR, Southern blot, whole-exome/genome sequencing-based approaches) combined with cross-sectional and longitudinal deep phenotyping in (1) cross-European cohort A (70 families) with ≥2 features of CANVAS or ataxia with chronic cough (ACC) and (2) Turkish cohort B (105 families) with unselected late-onset ataxia.

Results: Prevalence of RFC1 disease was 67% in cohort A, 14% in unselected cohort B, 68% in clinical CANVAS, and 100% in ACC. RFC1 disease was also identified in Western and Eastern Asian individuals and even by whole-exome sequencing. Visual compensation, sensory symptoms, and cough were strong positive discriminative predictors (>90%) against RFC1-negative patients. The phenotype across 70 RFC1-positive patients was mostly multisystemic (69%), including dysautonomia (62%) and bradykinesia (28%) (overlap with cerebellar-type multiple system atrophy [MSA-C]), postural instability (49%), slow vertical saccades (17%), and chorea or dystonia (11%). Ataxia progression was ≈1.3 Scale for the Assessment and Rating of Ataxia points per year (32 cross-sectional, 17 longitudinal assessments, follow-up ≤9 years [mean 3.1 years]) but also included early falls, variable nonlinear phases of MSA-C-like progression (SARA points 2.5-5.5 per year), and premature death. Treatment trials require 330 (1-year trial) and 132 (2-year trial) patients in total to detect 50% reduced progression.

Conclusions: RFC1 disease is frequent and occurs across continents, with CANVAS and ACC as highly diagnostic phenotypes yet as variable, overlapping clusters along a continuous multisystemic disease spectrum, including MSA-C-overlap. Our natural history data help to inform future RFC1 treatment trials.

Classification Of Evidence: This study provides Class II evidence that RFC1 repeat expansions are associated with CANVAS and ACC.
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http://dx.doi.org/10.1212/WNL.0000000000011528DOI Listing
March 2021

Bi-allelic truncating mutations in VWA1 cause neuromyopathy.

Brain 2021 Jan 18. Epub 2021 Jan 18.

Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tübingen, Germany.

The von Willebrand Factor A domain containing 1 protein, encoded by VWA1, is an extracellular matrix protein expressed in muscle and peripheral nerve. It interacts with collagen VI and perlecan, two proteins that are affected in hereditary neuromuscular disorders. Lack of VWA1 is known to compromise peripheral nerves in a Vwa1 knock-out mouse model. Exome sequencing led us to identify bi-allelic loss of function variants in VWA1 as the molecular cause underlying a so far genetically undefined neuromuscular disorder. We detected six different truncating variants in 15 affected individuals from six families of German, Arabic, and Roma descent. Disease manifested in childhood or adulthood with proximal and distal muscle weakness predominantly of the lower limbs. Myopathological and neurophysiological findings were indicative of combined neurogenic and myopathic pathology. Early childhood foot deformity was frequent, but no sensory signs were observed. Our findings establish VWA1 as a new disease gene confidently implicated in this autosomal recessive neuromyopathic condition presenting with child-/adult-onset muscle weakness as a key clinical feature.
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http://dx.doi.org/10.1093/brain/awaa418DOI Listing
January 2021

Generation of the CRISPR/Cas9-mediated KIF1C knock-out human iPSC line HIHRSi003-A-1.

Stem Cell Res 2020 12 29;49:102059. Epub 2020 Oct 29.

German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany; Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research and Center of Neurology, University of Tübingen, Tübingen, Germany. Electronic address:

Bi-allelic loss-of-function mutations in the gene encoding the motor protein KIF1C are associated with Hereditary Spastic Paraplegia (HSP) type SPG58, a slowly progressive neurodegenerative motoneuron disease. The biological role of KIF1C is incompletely understood. We used a protein-based CRISPR/Cas9 genome editing approach to generate a homozygous KIF1C knock-out iPSC line (HIHRSi003-A-1) from a healthy control. This iPSC-KIF1C line and the corresponding isogenic control are a useful model to study the physiological function of KIF1C and the pathophysiological consequences of KIF1C dysfunction in human disease.
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http://dx.doi.org/10.1016/j.scr.2020.102059DOI Listing
December 2020

PolyQ-expanded ataxin-3 protein levels in peripheral blood mononuclear cells correlate with clinical parameters in SCA3: a pilot study.

J Neurol 2020 Oct 26. Epub 2020 Oct 26.

Institute of Medical Genetics and Applied Genomics, University of Tübingen, Calwerstraße 7, 72076, Tübingen, Germany.

In view of upcoming clinical trials, quantitative molecular markers accessible in peripheral blood are of critical importance as prognostic or pharmacodynamic markers in genetic neurodegenerative diseases such as Spinocerebellar Ataxia Type 3 (SCA3), in particular for signaling target engagement. In this pilot study, we focused on the quantification of ataxin-3, the protein altered in SCA3, in human peripheral blood mononuclear cells (PBMCs) acquired from preataxic and ataxic SCA3 mutation carriers as well as healthy controls, as a molecular marker directly related to SCA3 pathophysiology. We established two different highly sensitive TR-FRET-based immunoassays to measure the protein levels of either total full-length, non-expanded and expanded, ataxin-3 or specifically polyQ-expanded ataxin-3. In PBMCs, a clear discrimination between SCA3 mutation carrier and controls were seen measuring polyQ-expanded ataxin-3 protein level. Additionally, polyQ-expanded ataxin-3 protein levels correlated with disease progression and clinical severity as assessed by the Scale for the Assessment and Rating of Ataxia. Total full-length ataxin-3 protein levels were directly influenced by the expression levels of the polyQ-expanded ataxin-3 protein, but were not correlated with clinical parameters. Assessment of ataxin-3 levels in fibroblasts or induced pluripotent stem cells allowed to distinguish mutation carriers from controls, thus providing proof-of-principle validation of our PBMC findings across cell lines. Total full-length or polyQ-expanded ataxin-3 protein was not detectable by TR-FRET assays in other biofluids like plasma or cerebrospinal fluid, indicating the need for ultra-sensitive assays for these biofluids. Standardization studies revealed that tube systems, blood sampling, and PBMC preparation may influence ataxin-3 protein levels indicating a high demand for standardized protocols in biomarker studies. In conclusion, the polyQ-expanded ataxin-3 protein is a promising candidate as a molecular target engagement marker in SCA3 in future clinical trials, determinable even in-easily accessible-peripheral blood biomaterials. These results, however, require validation in a larger cohort and further standardization of modifying conditions.
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http://dx.doi.org/10.1007/s00415-020-10274-yDOI Listing
October 2020

Comparative Transcriptional Profiling of Motor Neuron Disorder-Associated Genes in Various Human Cell Culture Models.

Front Cell Dev Biol 2020 24;8:544043. Epub 2020 Sep 24.

German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany.

Disease modeling requires appropriate cellular models that best mimic the underlying pathophysiology. Human origin and an adequate expression of the disease protein are pre-requisites that support information from a model to be meaningful. In this study we investigated expression profiles of (i) PBMCs and (ii) fibroblasts as patient derived cells as well as (iii) lymphoblasts and (iv) induced pluripotent stem cells (iPSC) as immortalized sources, and (v) iPSC-derived cortical neurons to assess their aptitude to model motor neuron diseases (MNDs) including hereditary spastic paraplegia (HSP), amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). We generated all five different cell types from two healthy donors and performed RNA sequencing to display expression patterns in MND-related genes. For the ten most common HSP genotypes we validated gene expression by qPCR. To verify the results on protein level, proteome analysis of fibroblasts, iPSCs and cortical neurons was performed. Depending on the specific MND gene we found largely different expression patterns. Out of 168 MND-related genes, 50 had their highest expression in iPSC-derived cortical neurons, 41 were most strongly expressed in fibroblasts, 26 in lymphoblasts, 22 in iPSCs, and 14 in PBMCs. Pathophysiologically related MNDs like HSPs associated with axonal transport deficits shared highest expression in cortical neurons. 15 MND-related genes were not detectable in any of the analyzed cell types. This may reflect the critical dependency of motor neurons on support of other cell types like oligodendrocytes which express myelin proteins like L1CAM (SPG1), PLP1 (SPG2) and MAG (SPG75) which are lacking in neurons but cause MNDs if mutated. This study provides comprehensive information on expression of genes associated with a large spectrum of MNDs. Expression profiles can be used to inform on appropriate cell models for genotype specific motor neuron research.
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http://dx.doi.org/10.3389/fcell.2020.544043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7543453PMC
September 2020

Association of Age at Onset and First Symptoms With Disease Progression in Patients With Metachromatic Leukodystrophy.

Neurology 2021 01 12;96(2):e255-e266. Epub 2020 Oct 12.

From Department of Paediatric Neurology and Developmental Medicine (C.K., S.E., C.R., J.B., A.B., N.K., I.K.-M., S.G.), University Children's Hospital; Department of Medical Genetics (S.B.-W.), University Hospital Tübingen; Clinical Neurogenetics Section (L.S.), Department of Neurology and Hertie Institute for Clinical Brain Research, University of Tübingen; and German Center for Neurodegenerative Diseases (DZNE) Tübingen (L.S.), Germany Crona Kliniken.

Objective: To compare disease progression between different onset forms of metachromatic leukodystrophy (MLD) and to investigate the influence of the type of first symptoms on the natural course and dynamic of disease progression.

Methods: Clinical, genetic, and biochemical parameters were analyzed within a nationwide study of patients with late-infantile (LI; onset age ≤2.5 years), early-juvenile (EJ; onset age 2.6 to <6 years), late-juvenile (LJ; onset age 6 to <16 years), and adult (onset age ≥16 years) forms of MLD. First symptoms were categorized as motor symptoms only, cognitive symptoms only, or both. Standardized clinical endpoints included loss of motor and language functions, as well as dysphagia/tube feeding.

Results: Ninety-seven patients with MLD were enrolled. Patients with LI (n = 35) and EJ (n = 18) MLD exhibited similarly rapid disease progression, all starting with motor symptoms (with or without additional cognitive symptoms). In LJ (n = 38) and adult-onset (n = 6) patients, the course of the disease was as rapid as in the early-onset forms, when motor symptoms were present at disease onset, while patients with only cognitive symptoms at disease onset exhibited significantly milder disease progression, independently of their age at onset. A certain genotype-phenotype correlation was observed.

Conclusions: In addition to age at onset, the type of first symptoms predicts the rate of disease progression in MLD. These findings are important for counseling and therapy.

Classification Of Evidence: This study provides Class II evidence that in patients with MLD, age at onset and the type of first symptoms predict the rate of disease progression.
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http://dx.doi.org/10.1212/WNL.0000000000011047DOI Listing
January 2021

Haploinsufficiency due to a novel ACO2 deletion causes mitochondrial dysfunction in fibroblasts from a patient with dominant optic nerve atrophy.

Sci Rep 2020 10 7;10(1):16736. Epub 2020 Oct 7.

Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg.

ACO2 is a mitochondrial protein, which is critically involved in the function of the tricarboxylic acid cycle (TCA), the maintenance of iron homeostasis, oxidative stress defense and the integrity of mitochondrial DNA (mtDNA). Mutations in the ACO2 gene were identified in patients suffering from a broad range of symptoms, including optic nerve atrophy, cortical atrophy, cerebellar atrophy, hypotonia, seizures and intellectual disabilities. In the present study, we identified a heterozygous 51 bp deletion (c.1699_1749del51) in ACO2 in a family with autosomal dominant inherited isolated optic atrophy. A complementation assay using aco1-deficient yeast revealed a growth defect for the mutant ACO2 variant substantiating a pathogenic effect of the deletion. We used patient-derived fibroblasts to characterize cellular phenotypes and found a decrease of ACO2 protein levels, while ACO2 enzyme activity was not affected compared to two age- and gender-matched control lines. Several parameters of mitochondrial function, including mitochondrial morphology, mitochondrial membrane potential or mitochondrial superoxide production, were not changed under baseline conditions. However, basal respiration, maximal respiration, and spare respiratory capacity were reduced in mutant cells. Furthermore, we observed a reduction of mtDNA copy number and reduced mtDNA transcription levels in ACO2-mutant fibroblasts. Inducing oxidative stress led to an increased susceptibility for cell death in ACO2-mutant fibroblasts compared to controls. Our study reveals that a monoallelic mutation in ACO2 is sufficient to promote mitochondrial dysfunction and increased vulnerability to oxidative stress as main drivers of cell death related to optic nerve atrophy.
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http://dx.doi.org/10.1038/s41598-020-73557-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7541502PMC
October 2020

Defining diagnostic cutoffs in neurological patients for serum very long chain fatty acids (VLCFA) in genetically confirmed X-Adrenoleukodystrophy.

Sci Rep 2020 09 15;10(1):15093. Epub 2020 Sep 15.

Institute for Clinical Chemistry and Pathobiochemistry/Central Laboratory, University of Tübingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany.

X-linked Adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene resulting in the accumulation of very long chain fatty acids (VLCFA). X-ALD is the most common peroxisomal disorder with adult patients (male and female) presenting with progressive spastic paraparesis with bladder disturbance, sensory ataxia with impaired vibration sense, and leg pain. 80% of male X-ALD patients have an adrenal failure, while adrenal dysfunction is rare in women with X-ALD. The objective of this study was to define optimal serum VLCFA cutoff values in patients with X-ALD-like phenotypes for the differentiation of genetically confirmed X-ALD and Non-X-ALD individuals. Three groups were included into this study: a) X-ALD cases with confirmed ABCD1 mutations (n = 34) and two Non-X-ALD cohorts: b) Patients with abnormal serum VCLFA levels despite negative testing for ABCD1 mutations (n = 15) resulting from a total of 1,953 VLCFA tests c) Phenotypically matching patients as Non-X-ALD controls (n = 104). Receiver operating curve analysis was used to optimize VLCFA cutoff values, which differentiate patients with genetically confirmed X-ALD and Non-X-ALD individuals. The serum concentration of C26:0 was superior to C24:0 for the detection of X-ALD. The best differentiation of Non-X-ALD and X-ALD individuals was obtained with a cutoff value of < 1.0 for the C24:0/C22:0 ratio resulting in a sensitivity of 97%, a specificity of 94.1% and a positive predictive value (PPV) of 83.8% for true X-ALD. Our findings further suggested a cutoff of < 0.02 for the ratio C26:0/C22:0 leading to a sensitivity of 90.9%, a specificity of 95.0%, and a PPV of 80.6%. Pearson correlation indicated a significant positive association between total blood cholesterol and VLCFA values. Usage of serum VLCFA are economical and established biomarkers suitable for the guidance of genetic testing matching the X-ALD phenotype. We suggest using our new optimized cutoff values, especially the two ratios (C24:0/C22:0 and C26:0/C22:0), in combination with standard lipid profiles.
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http://dx.doi.org/10.1038/s41598-020-71248-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7494896PMC
September 2020

Natural history of Krabbe disease - a nationwide study in Germany using clinical and MRI data.

Orphanet J Rare Dis 2020 09 10;15(1):243. Epub 2020 Sep 10.

Department of Child Neurology, Children's Hospital, University of Tübingen, Hoppe-Seyler-Str. 1, 72072, Tübingen, Germany.

Background: Krabbe disease or globoid cell leukodystrophy is a severe neurodegenerative disorder caused by a defect in the GALC gene leading to a deficiency of the enzyme ß-galactocerebrosidase. The aim of this work was to describe the natural disease course covering the whole spectrum of the disease.

Methods: Natural history data were collected with a standardized questionnaire, supplemented by medical record data. We defined different forms of the disease according to Abdelhalim et al. (2014). Developmental and disease trajectories were described based on the acquisition and loss of milestones as well as the time of first clearly identifiable symptoms and needs such as spasticity, seizures and tube feeding. MRI was assessed using the scoring system by Loes et al. (1999) and in addition a pattern recognition approach, based on Abdelhalim et al. (2014).

Results: Thirty-eight patients were identified, from 27 of these patients 40 MRIs were available; 30 (79%) had an infantile onset, showing first symptoms in their first year of life, almost all (27 out of 30) starting in the first six months. A later onset after the first year of life was observed in 8 patients (21%, range 18 months to 60 years). Irritability, abnormalities in movement pattern as well as general developmental regression were the first symptoms in the infantile group; disease course was severe with rapid progression, e.g. loss of visual fixation, need for tube feeding and then an early death. Gait disorders were the first symptoms in all patients of the later onset groups; progression was variable. The different forms of the disease were characterized by different MRI patterns (infantile: diffuse white matter involvement and cerebellar structures specifically affected, later onset: parieto-occipital white matter and splenium affected, adult: motor tracts specifically affected).

Conclusion: This is the first description of the natural history of Krabbe disease in a larger European cohort using developmental, clinical and MRI data. We would like to highlight the very different clinical and MRI characteristics of the later onset forms. These data are important for counselling affected patients and families and may serve as a basis for future treatment trials.
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http://dx.doi.org/10.1186/s13023-020-01489-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7488349PMC
September 2020

Conversion of individuals at risk for spinocerebellar ataxia types 1, 2, 3, and 6 to manifest ataxia (RISCA): a longitudinal cohort study.

Lancet Neurol 2020 09;19(9):738-747

German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; Department of Neurology, University Hospital of Bonn, Bonn, Germany.

Background: Spinocerebellar ataxias (SCAs) are autosomal dominant neurodegenerative diseases. Our aim was to study the conversion to manifest ataxia among apparently healthy carriers of mutations associated with the most common SCAs (SCA1, SCA2, SCA3, and SCA6), and the sensitivity of clinical and functional measures to detect change in these individuals.

Methods: In this prospective, longitudinal, observational cohort study, based at 14 referral centres in seven European countries, we enrolled children or siblings of patients with SCA1, SCA2, SCA3, or SCA6. Eligible individuals were those without ataxia, defined by a score on the Scale for the Assessment and Rating of Ataxia (SARA) of less than 3; participants had to be aged 18-50 years for children or siblings of patients with SCA1, SCA2, or SCA3, and 35-70 years for children or siblings of patients with SCA6. Study visits took place at recruitment and after 2, 4, and 6 years (plus or minus 3 months). We did genetic testing to identify mutation carriers, with results concealed to the participant and clinical investigator. We assessed patients with clinical scales, questionnaires of patient-reported outcome measures, a rating of the examiner's confidence of presence of ataxia, and performance-based coordination tests. Conversion to ataxia was defined by an SARA score of 3 or higher. We analysed the association of factors at baseline with conversion to ataxia and the evolution of outcome parameters on temporal scales (time from inclusion and time to predicted age at ataxia onset) in the context of mutation status and conversion status. This study is registered with ClinicalTrials.gov, NCT01037777.

Findings: Between Sept 13, 2008, and Oct 28, 2015, 302 participants were enrolled. We analysed data for 252 participants with at least one follow-up visit. 83 (33%) participants were from families affected by SCA1, 99 (39%) by SCA2, 46 (18%) by SCA3, and 24 (10%) by SCA6. In participants who carried SCA mutations, 26 (52%) of 50 SCA1 carriers, 22 (59%) of 37 SCA2 carriers, 11 (42%) of 26 SCA3 carriers, and two (13%) of 15 SCA6 carriers converted to ataxia. One (3%) of 33 SCA1 non-carriers and one (2%) of 62 SCA2 non-carriers converted to ataxia. Owing to the small number of people who met our criteria for ataxia, subsequent analyses could not be done in carriers of the SCA6 mutation. Baseline factors associated with conversion were age (hazard ratio 1·13 [95% CI 1·03-1·24]; p=0·011), CAG repeat length (1·25 [1·11-1·41]; p=0·0002), and ataxia confidence rating (1·72 [1·23-2·41]; p=0·0015) for SCA1; age (1·08 [1·02-1·14]; p=0·0077) and CAG repeat length (1·65 [1·27-2·13]; p=0·0001) for SCA2; and age (1·27 [1·09-1·50]; p=0·0031), confidence rating (2·60 [1·23-5·47]; p=0·012), and double vision (14·83 [2·15-102·44]; p=0·0063) for SCA3. From the time of inclusion, the SARA scores of SCA1, SCA2, and SCA3 mutation carriers increased, whereas they remained stable in non-carriers. On a timescale defined by the predicted time of ataxia onset, SARA progression in SCA1, SCA2, and SCA3 mutation carriers was non-linear, with marginal progression before ataxia and increasing progression after ataxia onset.

Interpretation: Our study provides quantitative data on the conversion of non-ataxic SCA1, SCA2, and SCA3 mutation carriers to manifest ataxia. Our data could prove useful for the design of preventive trials aimed at delaying the onset of ataxia by aiding sample size calculations and stratification of study participants.

Funding: European Research Area Network for Research Programmes on Rare Diseases, Polish Ministry of Science and Higher Education, Italian Ministry of Health, European Community's Seventh Framework Programme.
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http://dx.doi.org/10.1016/S1474-4422(20)30235-0DOI Listing
September 2020

Onset features and time to diagnosis in Friedreich's Ataxia.

Orphanet J Rare Dis 2020 08 3;15(1):198. Epub 2020 Aug 3.

Department of Neurology, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.

Background: In rare disorders diagnosis may be delayed due to limited awareness and unspecific presenting symptoms. Herein, we address the issue of diagnostic delay in Friedreich's Ataxia (FRDA), a genetic disorder usually caused by homozygous GAA-repeat expansions.

Methods: Six hundred eleven genetically confirmed FRDA patients were recruited within a multicentric natural history study conducted by the EFACTS (European FRDA Consortium for Translational Studies, ClinicalTrials.gov -Identifier NCT02069509). Age at first symptoms as well as age at first suspicion of FRDA by a physician were collected retrospectively at the baseline visit.

Results: In 554 of cases (90.7%), disease presented with gait or coordination disturbances. In the others (n = 57, 9.3%), non-neurological features such as scoliosis or cardiomyopathy predated ataxia. Before the discovery of the causal mutation in 1996, median time to diagnosis was 4(IQR = 2-9) years and it improved significantly after the introduction of genetic testing (2(IQR = 1-5) years, p < 0.001). Still, after 1996, time to diagnosis was longer in patients with a) non-neurological presentation (mean 6.7, 95%CI [5.5,7.9] vs 4.5, [4.2,5] years in those with neurological presentation, p = 0.001) as well as in b) patients with late-onset (3(IQR = 1-7) vs 2(IQR = 1-5) years compared to typical onset < 25 years of age, p = 0.03). Age at onset significantly correlated with the length of the shorter GAA repeat (GAA1) in case of neurological onset (r = - 0,6; p < 0,0001), but not in patients with non-neurological presentation (r = - 0,1; p = 0,4). Across 54 siblings' pairs, differences in age at onset did not correlate with differences in GAA-repeat length (r = - 0,14, p = 0,3).

Conclusions: In the genetic era, presentation with non-neurological features or in the adulthood still leads to a significant diagnostic delay in FRDA. Well-known correlations between GAA1 repeat length and disease milestones are not valid in case of atypical presentations or positive family history.
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http://dx.doi.org/10.1186/s13023-020-01475-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397644PMC
August 2020

Real-life gait assessment in degenerative cerebellar ataxia: Toward ecologically valid biomarkers.

Neurology 2020 09 1;95(9):e1199-e1210. Epub 2020 Jul 1.

From the Departments of Cognitive Neurology (W.I., J.S., M.G.) and Neurodegeneration (A.T., L.S.), Hertie Institute for Clinical Brain Research; Centre for Integrative Neuroscience (CIN) (W.I., J.S., M.G.); German Research Center for Neurodegenerative Diseases (DZNE) (A.T., L.S., M.S.), Tübingen; and Department of Neurology (D.T.), University of Duisburg-Essen, Germany.

Objectives: With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid motor biomarkers are highly warranted. In this observational study, we aimed to unravel and validate markers of ataxic gait in real life by using wearable sensors.

Methods: We assessed gait characteristics of 43 patients with degenerative cerebellar disease (Scale for the Assessment and Rating of Ataxia [SARA] 9.4 ± 3.9) compared with 35 controls by 3 body-worn inertial sensors in 3 conditions: (1) laboratory-based walking; (2) supervised free walking; (3) real-life walking during everyday living (subgroup n = 21). Movement analysis focused on measures of spatiotemporal step variability and movement smoothness.

Results: A set of gait variability measures was identified that allowed us to consistently identify ataxic gait changes in all 3 conditions. Lateral step deviation and a compound measure of spatial step variability categorized patients vs controls with a discrimination accuracy of 0.86 in real life. Both were highly correlated with clinical ataxia severity (effect size ρ = 0.76). These measures allowed detecting group differences even for patients who differed only 1 point in the clinical SARA subscore, with highest effect sizes for real-life walking ( = 0.67).

Conclusions: We identified measures of ataxic gait that allowed us not only to capture the gait variability inherent in ataxic gait in real life, but also to demonstrate high sensitivity to small differences in disease severity, with the highest effect sizes in real-life walking. They thus represent promising candidates for motor markers for natural history and treatment trials in ecologically valid contexts.

Classification Of Evidence: This study provides Class I evidence that a set of gait variability measures, even if accessed in real life, correlated with the clinical severity of ataxia in patients with degenerative cerebellar disease.
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http://dx.doi.org/10.1212/WNL.0000000000010176DOI Listing
September 2020

Multifocal, hypoechogenic nerve thickening in Cerebrotendinous Xanthomatosis.

Clin Neurophysiol 2020 Aug 21;131(8):1798-1803. Epub 2020 May 21.

Center of Neurology and Hertie Institute for Clinical Brain Research (HIH), University of Tübingen, Tübingen, Germany.

Objective: To characterize peripheral nerve morphology in cerebrotendinous xanthomatosis (CTX) patients using high-resolution ultrasound (HRUS) in vivo. We hypothesized that nerve enlargements might be present in CTX as a result of accumulation of abnormal lipids with deposition also in peripheral nerves.

Methods: Four CTX patients were examined using HRUS to assess morphological abnormalities of peripheral nerves as well as cervical nerve roots 5 and 6.

Results: HRUS revealed mild to moderate, hypoechogenic thickening of sensorimotor nerves (ulnar nerve in 1/4, tibial nerve in 3/4, median nerve 4/4 patients) as well as mild enlargement of pure sensory nerves (sural nerve in 2/3, superficial FN in 2/4 patients). The vagal nerve was moderately enlarged in one patient, cervical roots showed moderate enlargements of C5 in two patients, one of which also showing thickening of C6 as well as in another patient. UPSS score was slightly to moderately abnormal in all patients. The Homogeneity score was not increased suggesting regional to inhomogeneous nerve enlargement.

Conclusions: HRUS shows multifocal, hypoechogenic nerve thickening of peripheral nerves and nerve roots in CTX.

Significance: HRUS might serve as a valuable, additive and non-invasive bedside tool to assess peripheral nerve morphology in future clinical studies on CTX patients.
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http://dx.doi.org/10.1016/j.clinph.2020.04.162DOI Listing
August 2020

Neurofilaments in spinocerebellar ataxia type 3: blood biomarkers at the preataxic and ataxic stage in humans and mice.

EMBO Mol Med 2020 07 8;12(7):e11803. Epub 2020 Jun 8.

Hertie Institute for Clinical Brain Research (HIH), Center of Neurology, University of Tübingen, Tübingen, Germany.

With molecular treatments coming into reach for spinocerebellar ataxia type 3 (SCA3), easily accessible, cross-species validated biomarkers for human and preclinical trials are warranted, particularly for the preataxic disease stage. We assessed serum levels of neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH) in ataxic and preataxic subjects of two independent multicentric SCA3 cohorts and in a SCA3 knock-in mouse model. Ataxic SCA3 subjects showed increased levels of both NfL and pNfH. In preataxic subjects, NfL levels increased with proximity to the individual expected onset of ataxia, with significant NfL elevations already 7.5 years before onset. Cross-sectional NfL levels correlated with both disease severity and longitudinal disease progression. Blood NfL and pNfH increases in human SCA3 were each paralleled by similar changes in SCA3 knock-in mice, here also starting already at the presymptomatic stage, closely following ataxin-3 aggregation and preceding Purkinje cell loss in the brain. Blood neurofilaments, particularly NfL, might thus provide easily accessible, cross-species validated biomarkers in both ataxic and preataxic SCA3, associated with earliest neuropathological changes, and serve as progression, proximity-to-onset and, potentially, treatment-response markers in both human and preclinical SCA3 trials.
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http://dx.doi.org/10.15252/emmm.201911803DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7338806PMC
July 2020

Confirmation of TACO1 as a Leigh Syndrome Disease Gene in Two Additional Families.

J Neuromuscul Dis 2020 ;7(3):301-308

Department of Clinical Neurosciences, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK.

Background: In 2009, we identified TACO1 as a novel mitochondrial disease gene in a single family, however no second family has been described to confirm the role of TACO1 in mitochondrial disease.

Objective: In this report, we describe two independent consanguineous families carrying pathogenic variants in TACO1, confirming the phenotype.

Methods: Detailed clinical investigations and whole exome sequencing with haplotype analysis have been performed in several members of the two reported families.

Results: Clinical phenotype of the patients confirms the originally reported phenotype of a childhood-onset progressive cerebellar and pyramidal syndrome with optic atrophy and learning difficulties. Brain MRI showed periventricular white matter lesions with multiple cystic defects, suggesting leukoencephalopathy in both patients. One patient carried the previously described homozygous TACO1 variant (p.His158ProfsTer8) and haplotype analysis suggested that this variant is a rare founder mutation. The second patient from another family carried a homozygous novel frame shift variant (p.Cys85PhefsTer15).

Conclusions: The identification of two Turkish families with similar characteristic clinical presentation and an additional homozygous nonsense mutation confirms that TACO1 is a human mitochondrial disease gene. Although most patients with this clinical presentation undergo next generation sequencing analysis, screening for selected founder mutations in the Turkish population based on the precise clinical presentation may reduce time and cost of finding the genetic diagnosis even in the era of massively parallel sequencing.
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http://dx.doi.org/10.3233/JND-200510DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458500PMC
January 2020

Confirmation of TACO1 as a Leigh Syndrome Disease Gene in Two Additional Families.

J Neuromuscul Dis 2020 ;7(3):301-308

Department of Clinical Neurosciences, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK.

Background: In 2009, we identified TACO1 as a novel mitochondrial disease gene in a single family, however no second family has been described to confirm the role of TACO1 in mitochondrial disease.

Objective: In this report, we describe two independent consanguineous families carrying pathogenic variants in TACO1, confirming the phenotype.

Methods: Detailed clinical investigations and whole exome sequencing with haplotype analysis have been performed in several members of the two reported families.

Results: Clinical phenotype of the patients confirms the originally reported phenotype of a childhood-onset progressive cerebellar and pyramidal syndrome with optic atrophy and learning difficulties. Brain MRI showed periventricular white matter lesions with multiple cystic defects, suggesting leukoencephalopathy in both patients. One patient carried the previously described homozygous TACO1 variant (p.His158ProfsTer8) and haplotype analysis suggested that this variant is a rare founder mutation. The second patient from another family carried a homozygous novel frame shift variant (p.Cys85PhefsTer15).

Conclusions: The identification of two Turkish families with similar characteristic clinical presentation and an additional homozygous nonsense mutation confirms that TACO1 is a human mitochondrial disease gene. Although most patients with this clinical presentation undergo next generation sequencing analysis, screening for selected founder mutations in the Turkish population based on the precise clinical presentation may reduce time and cost of finding the genetic diagnosis even in the era of massively parallel sequencing.
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http://dx.doi.org/10.3233/JND-200510DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458500PMC
January 2020

Clinico-Genetic, Imaging and Molecular Delineation of COQ8A-Ataxia: A Multicenter Study of 59 Patients.

Ann Neurol 2020 08 10;88(2):251-263. Epub 2020 Jun 10.

Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research and Center of Neurology, University of Tübingen, Tübingen, Germany.

Objective: To foster trial-readiness of coenzyme Q8A (COQ8A)-ataxia, we map the clinicogenetic, molecular, and neuroimaging spectrum of COQ8A-ataxia in a large worldwide cohort, and provide first progression data, including treatment response to coenzyme Q10 (CoQ10).

Methods: Cross-modal analysis of a multicenter cohort of 59 COQ8A patients, including genotype-phenotype correlations, 3D-protein modeling, in vitro mutation analyses, magnetic resonance imaging (MRI) markers, disease progression, and CoQ10 response data.

Results: Fifty-nine patients (39 novel) with 44 pathogenic COQ8A variants (18 novel) were identified. Missense variants demonstrated a pleiotropic range of detrimental effects upon protein modeling and in vitro analysis of purified variants. COQ8A-ataxia presented as variable multisystemic, early-onset cerebellar ataxia, with complicating features ranging from epilepsy (32%) and cognitive impairment (49%) to exercise intolerance (25%) and hyperkinetic movement disorders (41%), including dystonia and myoclonus as presenting symptoms. Multisystemic involvement was more prevalent in missense than biallelic loss-of-function variants (82-93% vs 53%; p = 0.029). Cerebellar atrophy was universal on MRI (100%), with cerebral atrophy or dentate and pontine T2 hyperintensities observed in 28%. Cross-sectional (n = 34) and longitudinal (n = 7) assessments consistently indicated mild-to-moderate progression of ataxia (SARA: 0.45/year). CoQ10 treatment led to improvement by clinical report in 14 of 30 patients, and by quantitative longitudinal assessments in 8 of 11 patients (SARA: -0.81/year). Explorative sample size calculations indicate that ≥48 patients per arm may suffice to demonstrate efficacy for interventions that reduce progression by 50%.

Interpretation: This study provides a deeper understanding of the disease, and paves the way toward large-scale natural history studies and treatment trials in COQ8A-ataxia. ANN NEUROL 2020;88:251-263.
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http://dx.doi.org/10.1002/ana.25751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7877690PMC
August 2020

FIG4 mutations leading to parkinsonism and a phenotypical continuum between CMT4J and Yunis Varón syndrome.

Parkinsonism Relat Disord 2020 05 28;74:6-11. Epub 2020 Mar 28.

Department of Neurology and Hertie Institute for Clinical Brain Research and Center of Neurology, University of Tübingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany; German Center for Neurodegenerative Diseases (DZNE), 72076, Tübingen, Germany.

Background: Charcot-Marie-Tooth disease type 4J (CMT4J) originates from mutations in the FIG4 gene and leads to distal muscle weakness. Two null alleles of FIG4 cause Yunis Varón syndrome with severe central nervous system involvement, cleidocranial dysmorphism, absent thumbs and halluces and early death.

Objectives: To analyse the phenotypic spectrum of FIG4-related disease and explore effects of residual FIG4 protein.

Methods: Phenotyping of five new patients with FIG4-related disease. Western Blot analyses of FIG4 from patient fibroblasts.

Results: Next generation sequencing revealed compound heterozygous variants in FIG4 in five patients. All five patients presented with peripheral neuropathy, various degree of dysmorphism and a central nervous system involvement comprising Parkinsonism in 3/5 patients, cerebellar ataxia (1/5), spasticity of lower limbs (1/5), epilepsy (1/5) and/or cognitive deficits (2/5). Onset varied between the first and the seventh decade. There was no residual FIG4 protein detectable in fibroblasts of the four analysed patients.

Conclusion: This study extends the phenotypic spectrum of FIG4-related disease to Parkinsonism as a feature and demonstrates new phenotypes on a continuum between CMT4J and Yunis Varón syndrome.
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http://dx.doi.org/10.1016/j.parkreldis.2020.03.021DOI Listing
May 2020

ATPase Domain AFG3L2 Mutations Alter OPA1 Processing and Cause Optic Neuropathy.

Ann Neurol 2020 07 21;88(1):18-32. Epub 2020 Apr 21.

Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.

Objective: Dominant optic atrophy (DOA) is the most common inherited optic neuropathy, with a prevalence of 1:12,000 to 1:25,000. OPA1 mutations are found in 70% of DOA patients, with a significant number remaining undiagnosed.

Methods: We screened 286 index cases presenting optic atrophy, negative for OPA1 mutations, by targeted next generation sequencing or whole exome sequencing. Pathogenicity and molecular mechanisms of the identified variants were studied in yeast and patient-derived fibroblasts.

Results: Twelve cases (4%) were found to carry novel variants in AFG3L2, a gene that has been associated with autosomal dominant spinocerebellar ataxia 28 (SCA28). Half of cases were familial with a dominant inheritance, whereas the others were sporadic, including de novo mutations. Biallelic mutations were found in 3 probands with severe syndromic optic neuropathy, acting as recessive or phenotype-modifier variants. All the DOA-associated AFG3L2 mutations were clustered in the ATPase domain, whereas SCA28-associated mutations mostly affect the proteolytic domain. The pathogenic role of DOA-associated AFG3L2 mutations was confirmed in yeast, unraveling a mechanism distinct from that of SCA28-associated AFG3L2 mutations. Patients' fibroblasts showed abnormal OPA1 processing, with accumulation of the fission-inducing short forms leading to mitochondrial network fragmentation, not observed in SCA28 patients' cells.

Interpretation: This study demonstrates that mutations in AFG3L2 are a relevant cause of optic neuropathy, broadening the spectrum of clinical manifestations and genetic mechanisms associated with AFG3L2 mutations, and underscores the pivotal role of OPA1 and its processing in the pathogenesis of DOA. ANN NEUROL 2020 ANN NEUROL 2020;88:18-32.
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http://dx.doi.org/10.1002/ana.25723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7383914PMC
July 2020

First-line exome sequencing in Palestinian and Israeli Arabs with neurological disorders is efficient and facilitates disease gene discovery.

Eur J Hum Genet 2020 08 25;28(8):1034-1043. Epub 2020 Mar 25.

Department of Neurology and Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.

A high rate of consanguinity leads to a high prevalence of autosomal recessive disorders in inbred populations. One example of inbred populations is the Arab communities in Israel and the Palestinian Authority. In the Palestinian Authority in particular, due to limited access to specialized medical care, most patients do not receive a genetic diagnosis and can therefore neither receive genetic counseling nor possibly specific treatment. We used whole-exome sequencing as a first-line diagnostic tool in 83 Palestinian and Israeli Arab families with suspected neurogenetic disorders and were able to establish a probable genetic diagnosis in 51% of the families (42 families). Pathogenic, likely pathogenic or highly suggestive candidate variants were found in the following genes extending and refining the mutational and phenotypic spectrum of these rare disorders: ACO2, ADAT3, ALS2, AMPD2, APTX, B4GALNT1, CAPN1, CLCN1, CNTNAP1, DNAJC6, GAMT, GPT2, KCNQ2, KIF11, LCA5, MCOLN1, MECP2, MFN2, MTMR2, NT5C2, NTRK1, PEX1, POLR3A, PRICKLE1, PRKN, PRX, SCAPER, SEPSECS, SGCG, SLC25A15, SPG11, SYNJ1, TMCO1, and TSEN54. Further, this cohort has proven to be ideal for prioritization of new disease genes. Two separately published candidate genes (WWOX and PAX7) were identified in this study. Analyzing the runs of homozygosity (ROHs) derived from the Exome sequencing data as a marker for the rate of inbreeding, revealed significantly longer ROHs in the included families compared with a German control cohort. The total length of ROHs correlated with the detection rate of recessive disease-causing variants. Identification of the disease-causing gene led to new therapeutic options in four families.
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http://dx.doi.org/10.1038/s41431-020-0609-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7382450PMC
August 2020

Delineating -associated disease: From isolated neuropathy to early onset neurodegeneration.

Neurol Genet 2020 Feb 13;6(1):e393. Epub 2020 Jan 13.

Department of Neurology (C.S.), Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich; German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Institute of Human Genetics (C.N.), Department of Medical Genetics, University of Göttingen, Germany; Department of Pediatrics (E.F.), Salzburg State Hospitals (SALK) and Paracelsus Medical University; Division of Clinical Genetics Salzburg State Hospitals and Paracelsus Medical University, Salzburg, Austria; Department of Neurology (S.Y., F.F.), Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, China; Mitochondrial Medicine Frontier Program (R.D.G., M.J.F.), Children's Hospital of Philadelphia; Division of Human Genetics (R.D.G.), Department of Pediatrics, University of Pennsylvania Perelman School of Medicine Philadelphia; Department of Pediatrics (R.D.G.), Perelman School of Medicine, University of Pennsylvania; Institute of Medical Genetics and Applied Genomics (J.P.), University of Tübingen, Germany; Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research (J.P.), University of Tübingen, Germany; Children's Hospital (P.F.), Klinikum Reutlingen, Reutlingen; Department of Neurology (C.K.), University Hospital Bonn; Medical Genetic Center (S.K.), Munich; Department of Neurodegeneration (L.S., M.S.), Hertie Institute for Clinical Brain Research, University of Tübingen; German Center for Neurodegenerative Diseases (DZNE) (L.S.), Tübingen; Department of General Pediatrics (F.D.), Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine University, Duesseldorf, Germany; Division of Pediatric Neurology (G.M.S.), University Children's Hospital Zurich, Switzerland; Department of Neurology (B.B.), Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany; Department of Pediatrics (J.A.M.), Salzburg State Hospitals (SALK) and Paracelsus Medical University, Salzburg, Austria; Department of Neurology (A.A.), Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany; Medical Genetic Center (A.A.), Munich; Institute of Medical Genetics and Applied Genomics (T.B.H.), Tübingen, Germany; Institute of Human Genetics (H.P.), Technische Universität München, Munich, Germany; Institute of Human Genetics (H.P.), Helmholtz Center Munich, Neuherberg, Germany; Department of Pediatrics (S.B.W.), Salzburg State Hospitals (SALK) and Paracelsus Medical University, Salzburg, Austria; Institute of Human Genetics, Technische Universität München, Munich, Germany; Institute of Human Genetics (S.B.W.), Helmholtz Center Munich, Neuherberg, Germany; Center for Medical Genetics (K.M.), and Department of Metabolism, Chiba Children's Hospital, Chiba, Japan; and Department of Neurology (T.K.), Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich; German Center for Neurodegenerative Diseases (DZNE) (T.K.), Munich; Munich Cluster for Systems Neurology (SyNergy) (T.K.), Ludwig Maximilians University Munich, Germany.

Objective: To delineate the phenotypic and genotypic spectrum in carriers of mitochondrial mutations in a large international cohort.

Methods: We analyzed in detail the clinical, genetical, and neuroimaging data from 132 mutation carriers from national registries and local databases from Europe, USA, Japan, and China.

Results: We identified 113 clinically affected and 19 asymptomatic individuals with a known pathogenic mutation. The most frequent mutations were m.8993 T > G (53/132, 40%), m.8993 T > C (30/132, 23%), m.9176 T > C (30/132, 23%), and m.9185 T > C (12/132, 9%). The degree of heteroplasmy was high both in affected (mean 95%, range 20%-100%) and unaffected individuals (mean 73%, range 20%-100%). Age at onset ranged from prenatal to the age of 75 years, but almost half of the patients (49/103, 48%) became symptomatic before their first birthday. In 28 deceased patients, the median age of death was 14 months. The most frequent symptoms were ataxia (81%), cognitive dysfunction (49%), neuropathy (48%), seizures (37%), and retinopathy (14%). A diagnosis of Leigh syndrome was made in 55% of patients, whereas the classic syndrome of neuropathy, ataxia, and retinitis pigmentosa (NARP) was rare (8%).

Conclusions: In this currently largest series of patients with mitochondrial mutations, the phenotypic spectrum ranged from asymptomatic to early onset multisystemic neurodegeneration. The degree of mutation heteroplasmy did not reliably predict disease severity. Leigh syndrome was found in more than half of the patients, whereas classic NARP syndrome was rare. Oligosymptomatic presentations were rather frequent in adult-onset patients, indicating the need to include mutations in the differential diagnosis of both ataxias and neuropathies.
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http://dx.doi.org/10.1212/NXG.0000000000000393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6975175PMC
February 2020

NfL and pNfH are increased in Friedreich's ataxia.

J Neurol 2020 May 30;267(5):1420-1430. Epub 2020 Jan 30.

Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research and Center of Neurology, University of Tuebingen, Hoppe-Seyler-Str. 3, 72076, Tuebingen, Germany.

Objective: To assess neurofilaments as neurodegenerative biomarkers in serum of patients with Friedreich's ataxia.

Methods: Single molecule array measurements of neurofilament light (NfL) and heavy chain (pNfH) in 99 patients with genetically confirmed Friedreich's ataxia. Correlation of NfL/pNfH serum levels with disease severity, disease duration, age, age at onset, and GAA repeat length.

Results: Median serum levels of NfL were 21.2 pg/ml (range 3.6-49.3) in controls and 26.1 pg/ml (0-78.1) in Friedreich's ataxia (p = 0.002). pNfH levels were 23.5 pg/ml (13.3-43.3) in controls and 92 pg/ml (3.1-303) in Friedreich's ataxia (p = 0.0004). NfL levels were significantly increased in younger patients (age 16-31 years, p < 0.001) and patients aged 32-47 years (p = 0.008), but not in patients of age 48 years and older (p = 0.41). In a longitudinal assessment, there was no difference in NfL levels in 14 patients with repeated sampling 2 years after baseline measurement. Levels of NfL correlated inversely with GAA1 repeat length (r = - 0.24, p = 0.02) but not with disease severity (r = - 0.13, p = 0.22), disease duration (r = - 0.06, p = 0.53), or age at onset (r = 0.05, p = 0.62).

Conclusion: Serum levels of NfL and pNfH are elevated in Friedreich's ataxia, but differences to healthy controls decrease with increasing age. Long-term longitudinal data are required to explore whether this reflects a selection bias from early death of more severely affected individuals or a slowing down of the neurodegenerative process with age. In a pilot study over 2 years of follow-up-a period relevant for biomarkers indicating treatment effects-we found NfL levels to be stable.
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http://dx.doi.org/10.1007/s00415-020-09722-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7184046PMC
May 2020

Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy.

Nat Commun 2020 01 30;11(1):595. Epub 2020 Jan 30.

Institute of Medical Biology, A*STAR, Biopolis, Singapore, 138648, Singapore.

Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients' primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy.
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http://dx.doi.org/10.1038/s41467-020-14360-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992768PMC
January 2020

Unraveling the genetic cause of hereditary ophthalmic disorders in Arab societies from Israel and the Palestinian Authority.

Eur J Hum Genet 2020 06 2;28(6):742-753. Epub 2020 Jan 2.

Institute for Ophthalmic Research, Molecular Genetics Laboratory, Tuebingen, Germany.

Visual impairment due to inherited ophthalmic disorders is amongst the most common disabilities observed in populations practicing consanguineous marriages. Here we investigated the molecular genetic basis of an unselected broad range of ophthalmic disorders in 20 consanguineous families from Arab villages of Israel and the Palestinian Authority. Most patients had little or very poor prior clinical workup and were recruited in a field study. Homozygosity mapping followed by candidate gene sequencing applying conventional Sanger sequencing or targeted next generation sequencing was performed in six families. In the remaining 14 families, one affected subject per family was chosen for whole exome sequencing. We discovered likely disease-causing variants, all homozygous, in 19 of 20 independent families (95%) including a previously reported novel disease gene for congenital nystagmus associated with foveal hypoplasia. Moreover, we found a family in which disease-causing variants for two collagenopathies - Stickler and Knobloch syndrome - segregate within a large sibship. Nine of the 19 distinct variants observed in this study were novel. Our study demonstrated a very high molecular diagnostic yield for a highly diverse spectrum of rare ophthalmic disorders in Arab patients from Israel and the Palestinian Authority, even with very limited prior clinical investigation. We conclude that 'genetic testing first' may be an economic way to direct clinical care and to support proper genetic counseling and risk assessment in these families.
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http://dx.doi.org/10.1038/s41431-019-0566-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253446PMC
June 2020

mRNA as a Novel Treatment Strategy for Hereditary Spastic Paraplegia Type 5.

Mol Ther Methods Clin Dev 2019 Dec 31;15:359-370. Epub 2019 Oct 31.

German Center for Neurodegenerative Diseases (DZNE), 72076 Tübingen, Germany.

Hereditary spastic paraplegia type 5 is a neurodegenerative disease caused by loss-of-function mutations in the gene encoding the oxysterol 7-α-hydroxylase involved in bile acid synthesis in the liver. Lack of CYP7B1 leads to an accumulation of its oxysterol substrates, in particular 25-hydroxycholesterol and 27-hydroxycholesterol that are able to cross the blood-brain barrier and have neurotoxic properties. A potential therapeutic strategy for SPG5 is the replacement of CYP7B1 by administration of mRNA. Here, we studied the intravenous application of formulated mouse and human CYP7B1 mRNA in mice lacking the endogenous gene. A single-dose injection of either mouse or human CYP7B1 mRNA led to a pronounced degradation of oxysterols in liver and serum within 2 days of treatment. Pharmacokinetics indicate a single injection of human CYP7B1 mRNA to be effective in reducing oxysterols for at least 5 days. Repetitive applications of mRNA were safe for at least 17 days and resulted in a significant reduction of neurotoxic oxysterols not only in liver and serum but also to some extent in the brain. Our study highlights the potential to use mRNA as a novel therapy to treat patients with SPG5 disease.
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http://dx.doi.org/10.1016/j.omtm.2019.10.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6888748PMC
December 2019

Single Nucleotide Polymorphisms in Thyroid Hormone Transporter Genes MCT8, MCT10 and Deiodinase DIO2 Contribute to Inter-Individual Variance of Executive Functions and Personality Traits.

Exp Clin Endocrinol Diabetes 2020 Sep 9;128(9):573-581. Epub 2019 Dec 9.

Department of Neurology, University of Lübeck, Lübeck, Germany.

Thyroid hormones are modulators of cognitive functions, and changes in hormone levels affect intelligence, memory, attention and executive function. Single nucleotide polymorphisms (SNPs) of transporter proteins MCT8, MCT10 and deiodinase 2 (DIO2) influence thyroid metabolism and could therefore contribute to inter-individual variance of cognitive functions. This study investigates the influence of these SNPs using an extensive neuropsychological test battery. 656 healthy participants aged 18-39 years were genotyped for four SNPs: MCT8 (rs5937843 and rs6647476), MCT10 (rs14399) and DIO2 (rs225014) and underwent eleven different neuropsychological tests as well as four personality questionnaires. Test results were compared between homo- and heterozygous carriers and for the X-linked MCT8 additionally between men and women. Personality questionnaires revealed that Risk Seeking was reduced in homozygous T carriers and highest in homozygous C carriers of the DIO2 SNP and that both polymorphisms of MCT8 had an additive effect on Physical Aggression in men. Neuropsychological testing indicated that MCT10 affects nonverbal reasoning abilities, DIO2 influences working memory and verbal fluency and MCT8 influences attention, alertness and planning. This pilot study suggests an influence of polymorphisms in thyroid hormone transporter genes and deiodinase on cognitive domains and personality traits.
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http://dx.doi.org/10.1055/a-1065-1786DOI Listing
September 2020

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

J Neurol 2020 Feb 23;267(2):369-379. Epub 2019 Oct 23.

Department of Neurodegenerative Disease, Hertie-Institute for Clinical Brain Research, and Center for Neurology, University of Tübingen, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany.

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 gene. Although HSP is an upper motor neuron disease, the relevance of non-motor symptoms is increasingly recognized because of the potential response to treatment. Our study sets out to evaluate non-motor symptoms and their relevance with regard to health-related quality of life. In 118 genetically confirmed SPG4 cases and age- and gender-matched controls, validated questionnaires were used to evaluate fatigue, depression, pain, and restless legs syndrome. In addition, self-reported medical information was collected concerning comorbidities and bladder, bowel, and sexual dysfunction. In a sub-study, cognition was evaluated using the CANTAB test-battery and the Montreal Cognitive Assessment in 26 SPG4 patients. We found depression and pain to be significantly increased. The frequency of restless legs syndrome varied largely depending on defining criteria. There were no significant deficits in cognition as examined by CANTAB despite a significant increase in self-reported memory impairment in SPG4 patients. Bladder, sexual, and defecation problems were frequent and seemed to be underrecognized in current treatment strategies. All identified non-motor symptoms correlated with health-related quality of life, which was reduced in SPG4 compared to controls. We recommend that clinicians regularly screen for depression, pain, and fatigue and ask for bladder, sexual, and defecation problems to recognize and treat non-motor symptoms accordingly to improve quality of life in patients with SPG4.
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http://dx.doi.org/10.1007/s00415-019-09573-wDOI Listing
February 2020