Publications by authors named "Jonathan Baets"

101 Publications

Biallelic mutations in complex neuropathy affect ADP ribosylation and DNA damage response.

Life Sci Alliance 2021 11 3;4(11). Epub 2021 Sep 3.

Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium

ADP ribosylation is a reversible posttranslational modification mediated by poly(ADP-ribose)transferases (e.g., PARP1) and (ADP-ribosyl)hydrolases (e.g., ARH3 and PARG), ensuring synthesis and removal of mono-ADP-ribose or poly-ADP-ribose chains on protein substrates. Dysregulation of ADP ribosylation signaling has been associated with several neurodegenerative diseases, including Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Recessive ARH3 mutations are described to cause a stress-induced epileptic ataxia syndrome with developmental delay and axonal neuropathy (CONDSIAS). Here, we present two families with a neuropathy predominant disorder and homozygous mutations in We characterized a novel C26F mutation, demonstrating protein instability and reduced protein function. Characterization of the recurrent V335G mutant demonstrated mild loss of expression with retained enzymatic activity. Although the V335G mutation retains its mitochondrial localization, it has altered cytosolic/nuclear localization. This minimally affects basal ADP ribosylation but results in elevated nuclear ADP ribosylation during stress, demonstrating the vital role of ADP ribosylation reversal by ARH3 in DNA damage control.
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http://dx.doi.org/10.26508/lsa.202101057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8424258PMC
November 2021

Characterization of HNRNPA1 mutations defines diversity in pathogenic mechanisms and clinical presentation.

JCI Insight 2021 Jul 22;6(14). Epub 2021 Jul 22.

Translational Neurosciences, Faculty of Medicine and Health Sciences, and.

Mutations in HNRNPA1 encoding heterogeneous nuclear ribonucleoprotein (hnRNP) A1 are a rare cause of amyotrophic lateral sclerosis (ALS) and multisystem proteinopathy (MSP). hnRNPA1 is part of the group of RNA-binding proteins (RBPs) that assemble with RNA to form RNPs. hnRNPs are concentrated in the nucleus and function in pre-mRNA splicing, mRNA stability, and the regulation of transcription and translation. During stress, hnRNPs, mRNA, and other RBPs condense in the cytoplasm to form stress granules (SGs). SGs are implicated in the pathogenesis of (neuro-)degenerative diseases, including ALS and inclusion body myopathy (IBM). Mutations in RBPs that affect SG biology, including FUS, TDP-43, hnRNPA1, hnRNPA2B1, and TIA1, underlie ALS, IBM, and other neurodegenerative diseases. Here, we characterize 4 potentially novel HNRNPA1 mutations (yielding 3 protein variants: *321Eext*6, *321Qext*6, and G304Nfs*3) and 2 known HNRNPA1 mutations (P288A and D262V), previously connected to ALS and MSP, in a broad spectrum of patients with hereditary motor neuropathy, ALS, and myopathy. We establish that the mutations can have different effects on hnRNPA1 fibrillization, liquid-liquid phase separation, and SG dynamics. P288A accelerated fibrillization and decelerated SG disassembly, whereas *321Eext*6 had no effect on fibrillization but decelerated SG disassembly. By contrast, G304Nfs*3 decelerated fibrillization and impaired liquid phase separation. Our findings suggest different underlying pathomechanisms for HNRNPA1 mutations with a possible link to clinical phenotypes.
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http://dx.doi.org/10.1172/jci.insight.148363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8410042PMC
July 2021

The ARCA Registry: A Collaborative Global Platform for Advancing Trial Readiness in Autosomal Recessive Cerebellar Ataxias.

Front Neurol 2021 25;12:677551. Epub 2021 Jun 25.

Unit of Neuromuscular and Neurodegenerative Diseases, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.

Autosomal recessive cerebellar ataxias (ARCAs) form an ultrarare yet expanding group of neurodegenerative multisystemic diseases affecting the cerebellum and other neurological or non-neurological systems. With the advent of targeted therapies for ARCAs, disease registries have become a precious source of real-world quantitative and qualitative data complementing knowledge from preclinical studies and clinical trials. Here, we review the , a global collaborative multicenter platform (>15 countries, >30 sites) with the overarching goal to advance trial readiness in ARCAs. It presents a good clinical practice (GCP)- and general data protection regulation (GDPR)-compliant professional-reported registry for multicenter web-based capture of cross-center standardized longitudinal data. Modular electronic case report forms (eCRFs) with core, extended, and optional datasets allow data capture tailored to the participating site's variable interests and resources. The eCRFs cover all key data elements required by regulatory authorities [European Medicines Agency (EMA)] and the European Rare Disease (ERD) platform. They capture genotype, phenotype, and progression and include demographic data, biomarkers, comorbidity, medication, magnetic resonance imaging (MRI), and longitudinal clinician- or patient-reported ratings of ataxia severity, non-ataxia features, disease stage, activities of daily living, and (mental) health status. Moreover, they are aligned to major autosomal-dominant spinocerebellar ataxia (SCA) and sporadic ataxia (SPORTAX) registries in the field, thus allowing for joint and comparative analyses not only across ARCAs but also with SCAs and sporadic ataxias. The registry is at the core of a systematic multi-component ARCA database cluster with a linked biobank and an evolving study database for digital outcome measures. Currently, the registry contains more than 800 patients with almost 1,500 visits representing all ages and disease stages; 65% of patients with established genetic diagnoses capture all the main ARCA genes, and 35% with unsolved diagnoses are targets for advanced next-generation sequencing. The ARCA Registry serves as the backbone of many major European and transatlantic consortia, such as PREPARE, PROSPAX, and the Ataxia Global Initiative, with additional data input from SPORTAX. It has thus become the largest global trial-readiness registry in the ARCA field.
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http://dx.doi.org/10.3389/fneur.2021.677551DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8267795PMC
June 2021

High prevalence of sporadic late-onset nemaline myopathy in a cohort of whole-exome sequencing negative myopathy patients.

Neuromuscul Disord 2021 May 14. Epub 2021 May 14.

Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium; The Laboratory of Neuromuscular Pathology, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; The Neuromuscular Reference Centre, Department of Neurology, Antwerp University Hospital, Antwerp, Belgium. Electronic address:

Sporadic late-onset nemaline myopathy (SLONM) is an enigmatic, supposedly very rare, putatively immune-mediated late-onset myopathy, typically presenting with subacutely progressive limb-girdle muscular weakness, yet slowly progressing cases have been described too. We systematically studied (para)clinical and histopathological findings in a cohort of 18 isolated yet suspected inherited myopathy patients, showing late-onset, slowly progressive limb-girdle muscle weakness, remaining unsolved after whole-exome sequencing. The presence of a monoclonal gammopathy of unknown significance (MGUS) and anti-HMGCR antibodies was determined. Biopsies were systematically re-evaluated and systematic immunohistochemical and electron microscopy studies were performed to particularly evaluate the presence of rods and/or inflammatory features. Ten patients showed rods as core feature on muscle biopsy on re-evaluation, four of these had an IgG κ MGUS in blood. As such, these ten patients represented suspected slowly progressing SLONM patients, with auxiliary data supporting this diagnosis: 1) additional muscle biopsy features pointing towards Z-disk and myofibrillar pathology; 2) a common selective pattern of muscle involvement on MRI; 3) inflammatory features on muscle biopsy. Findings in this proof-of-concept study highlight difficulties in reliably diagnosing slowly progressing SLONM and the probably underestimated prevalence of this entity in cohorts of whole exome sequencing negative myopathy patients, initially considered having an inherited myopathy.
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http://dx.doi.org/10.1016/j.nmd.2021.04.010DOI Listing
May 2021

Family-based exome sequencing identifies RBM45 as a possible candidate gene for frontotemporal dementia and amyotrophic lateral sclerosis.

Neurobiol Dis 2021 08 9;156:105421. Epub 2021 Jun 9.

Neurodegenerative Brain Diseases, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium; Institute Born-Bunge, Antwerp, Belgium. Electronic address:

Neurodegenerative disorders like frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are pathologically characterized by toxic protein deposition in the cytoplasm or nucleus of affected neurons and glial cells. Many of these aggregated proteins belong to the class of RNA binding proteins (RBP), and, when mutated, account for a significant subset of familial ALS and FTD cases. Here, we present first genetic evidence for the RBP gene RBM45 in the FTD-ALS spectrum. RBM45 shows many parallels with other FTD-ALS associated genes and proteins. Multiple lines of evidence have demonstrated that RBM45 is an RBP that, upon mutation, redistributes to the cytoplasm where it co-aggregates with other RBPs into cytoplasmic stress granules (SG), evolving to persistent toxic TDP-43 immunoreactive inclusions. Exome sequencing in two affected first cousins of a heavily affected early-onset dementia family listed a number of candidate genes. The gene with the highest pathogenicity score was the RBP gene RBM45. In the family, the RBM45 Arg183* nonsense mutation co-segregated in both affected cousins. Validation in an unrelated patient (n = 548) / control (n = 734) cohort identified an additional RBM45 Arg183* carrier with bvFTD on a shared 4 Mb haplotype. Transcript and protein expression analysis demonstrated loss of nuclear RBM45, suggestive of a loss-of-function disease mechanism. Further, two more ultra-rare VUS, one in the nuclear localization signal (NLS, p.Lys456Arg) in an ALS patient and one in the intrinsically disordered homo-oligomer assembly (HOA) domain (p.Arg314Gln) in a patient with nfvPPA were detected. Our findings suggest that the pathomechanisms linking RBM45 with FTD and ALS may be related to its loss of nuclear function as a mediator of mRNA splicing, cytoplasmic retention or its inability to form homo-oligomers, leading to aggregate formation with trapping of other RBPs including TDP-43, which may accumulate into persisted TDP-43 inclusions.
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http://dx.doi.org/10.1016/j.nbd.2021.105421DOI Listing
August 2021

Unrestrained poly-ADP-ribosylation provides insights into chromatin regulation and human disease.

Mol Cell 2021 06 20;81(12):2640-2655.e8. Epub 2021 May 20.

Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK. Electronic address:

ARH3/ADPRHL2 and PARG are the primary enzymes reversing ADP-ribosylation in vertebrates, yet their functions in vivo remain unclear. ARH3 is the only hydrolase able to remove serine-linked mono(ADP-ribose) (MAR) but is much less efficient than PARG against poly(ADP-ribose) (PAR) chains in vitro. Here, by using ARH3-deficient cells, we demonstrate that endogenous MARylation persists on chromatin throughout the cell cycle, including mitosis, and is surprisingly well tolerated. Conversely, persistent PARylation is highly toxic and has distinct physiological effects, in particular on active transcription histone marks such as H3K9ac and H3K27ac. Furthermore, we reveal a synthetic lethal interaction between ARH3 and PARG and identify loss of ARH3 as a mechanism of PARP inhibitor resistance, both of which can be exploited in cancer therapy. Finally, we extend our findings to neurodegeneration, suggesting that patients with inherited ARH3 deficiency suffer from stress-induced pathogenic increase in PARylation that can be mitigated by PARP inhibition.
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http://dx.doi.org/10.1016/j.molcel.2021.04.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8221567PMC
June 2021

Biallelic variants in HPDL cause pure and complicated hereditary spastic paraplegia.

Brain 2021 06;144(5):1422-1434

Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.

Human 4-hydroxyphenylpyruvate dioxygenase-like (HPDL) is a putative iron-containing non-heme oxygenase of unknown specificity and biological significance. We report 25 families containing 34 individuals with neurological disease associated with biallelic HPDL variants. Phenotypes ranged from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spasticity and global developmental delays, sometimes complicated by episodes of neurological and respiratory decompensation. Variants included bona fide pathogenic truncating changes, although most were missense substitutions. Functionality of variants could not be determined directly as the enzymatic specificity of HPDL is unknown; however, when HPDL missense substitutions were introduced into 4-hydroxyphenylpyruvate dioxygenase (HPPD, an HPDL orthologue), they impaired the ability of HPPD to convert 4-hydroxyphenylpyruvate into homogentisate. Moreover, three additional sets of experiments provided evidence for a role of HPDL in the nervous system and further supported its link to neurological disease: (i) HPDL was expressed in the nervous system and expression increased during neural differentiation; (ii) knockdown of zebrafish hpdl led to abnormal motor behaviour, replicating aspects of the human disease; and (iii) HPDL localized to mitochondria, consistent with mitochondrial disease that is often associated with neurological manifestations. Our findings suggest that biallelic HPDL variants cause a syndrome varying from juvenile-onset pure hereditary spastic paraplegia to infantile-onset spastic tetraplegia associated with global developmental delays.
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http://dx.doi.org/10.1093/brain/awab041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8219359PMC
June 2021

Cerebellar ataxia in progressive supranuclear palsy: a clinico-pathological case report.

Acta Neurol Belg 2021 Apr 5;121(2):599-602. Epub 2021 Mar 5.

Department of Neurology, Antwerp University Hospital, Drie Eikenstraat 655, B-2650, Edegem, Belgium.

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http://dx.doi.org/10.1007/s13760-021-01629-xDOI Listing
April 2021

Efficacy and Safety of Bimagrumab in Sporadic Inclusion Body Myositis: Long-term Extension of RESILIENT.

Neurology 2021 03 17;96(12):e1595-e1607. Epub 2021 Feb 17.

From the Department of Neurology (A.A.A.), Brigham and Women's Hospital and Harvard Medical School, Boston, MA; Medical Research Council Centre for Neuromuscular Diseases (M.G.H., P.M.M.) and Institute of Neurology, Department of Neuromuscular Diseases & Centre for Rheumatology (P.M.M.), University College London; Department of Rheumatology & Queen Square Centre for Neuromuscular Diseases (P.M.M.), University College London Hospitals NHS Foundation Trust; Department of Rheumatology (P.M.M.), Northwick Park Hospital, London North West University Healthcare NHS Trust, UK; Department of Neurology (U.A.B.), Leiden University Medical Center, Netherlands; National Institute for Health Research Manchester Biomedical Research Centre (H.C.), Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, The University of Manchester, UK; Department of Internal Medicine and Clinical Immunology (O.B.), Pitié-Salpêtrière Hospital, Sorbonne Université, Paris, France; Novartis Healthcare Pvt. Ltd. (K.A.K), Hyderabad, India; Novartis Pharmaceuticals (M.W., D.A.P.), East Hanover, NJ; Novartis Pharma AG (L.B.T., A.A.S-T.), Basel, Switzerland; Department of Neurology (T.E.L.), The Johns Hopkins University School of Medicine, Baltimore, MD; Institute for Immunology & Infectious Diseases (M.N.), Fiona Stanley Hospital, Murdoch University and Notre Dame University, Perth; Department of Neurology (C.L.), Royal North Shore Hospital, New South Wales; Calvary Health Care Bethlehem (K.A.R.), Caulfield South, Australia; Department of Neurology (M.d.V), Amsterdam University Medical Centre, the Netherlands; Department of Medicine (D.P.A.), University of Miami, FL; Department of Neurology (R.J.B., M.M.D.), University of Kansas Medical Center, Kansas City; Department of Neurology (J.A.L.M.), Newcastle upon Tyne Hospitals NHS Foundation Trust, UK; Department of Neurology (J.T.K.), The Ohio State University Wexner Medical Center, Columbus; Neuromuscular Research Center (B.O., N.C.J.), UC Davis School of Medicine, Sacramento, CA; Department of Neurology (P.V.d.B.), University Hospital Saint-Luc, University of Louvain, Brussels; Neuromuscular Reference Centre, Department of Neurology (J.B.), Antwerp University Hospital; Institute Born-Bunge (J.B.), University of Antwerp; Department of Neurology (J.L.d.B.), Ghent University Hospital, Belgium; Department of Neurology (C.K.), Oregon Health & Science University, Portland; Department of Neurology (W.S.D.), Massachusetts General Hospital, Neuromuscular Diagnostic Center and Electromyography Laboratory, Boston; Department of Neurology (M.M.), Fondazione Policlinico Universitario Agostino Gemelli IRCCS; Università Cattolica del Sacro Cuore (M.M.), Rome, Italy; Department of Neurology (S.P.N.), University of Texas Southwestern Medical Center, Dallas; Department of Neurology (H.H.J.), University Hospital and University of Zurich, Switzerland; Department of Neurosciences (E.P.), University of Padova School of Medicine; Fondazione IRCCS Istituto Neurologico Carlo Besta (L.M.), Milan; Unit of Neurology and Neuromuscular Disorders (C.R.), Azienda Ospedaliera Universitaria Policlinico G Martino, University of Messina; Center for Neuromuscular Diseases (M.F.), Unit of Neurology, ASST Spedali Civili and University of Brescia, Italy; Nerve and Muscle Center of Texas (A.I.S.), Houston; Neuromuscular Research Center (K.S.), Phoenix, AZ; Department of Neurology (N.A.G.), ALS & Neuromuscular Center, University of California Irvine, Orange; Department of Neurology (M.M.-Y.), National Center Hospital, National Center of Neurology and Psychiatry, Tokyo; Department of Neurology (S.Y.), Kumamoto University Hospital; Department of Neurology (N.S.), Tohoku University Hospital, Miyagi; Department of Neurology (M.A.), Tohoku University School of Medicine, Sendai; Department of Neurology (M.K.), Nagoya University Hospital, Aichi; Department of Neurology (H.M.), Osaka City General Hospital; Wakayama Medical University Hospital (K.M.); Tokushima University Hospital (H.N.); Department of Neuromuscular Research (I.N.), National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan; RTI Health Solutions (C.D.R., V.S.L.W.), Research Triangle Park, NC; Copenhagen Neuromuscular Center (J.V.), Rigshospitalet, University of Copenhagen, Denmark; and UCB (L.Z.A.), Bulle, Switzerland. H.N. is currently affiliated with the Department of Neurology, Kanazawa Medical University, Ishikawa, Japan. B.O. is currently affiliated with the Department of Neurology, Mayo Clinic, Jacksonville, FL.

Objective: To assess long-term (2 years) effects of bimagrumab in participants with sporadic inclusion body myositis (sIBM).

Methods: Participants (aged 36-85 years) who completed the core study (RESILIENT [Efficacy and Safety of Bimagrumab/BYM338 at 52 Weeks on Physical Function, Muscle Strength, Mobility in sIBM Patients]) were invited to join an extension study. Individuals continued on the same treatment as in the core study (10 mg/kg, 3 mg/kg, 1 mg/kg bimagrumab or matching placebo administered as IV infusions every 4 weeks). The co-primary outcome measures were 6-minute walk distance (6MWD) and safety.

Results: Between November 2015 and February 2017, 211 participants entered double-blind placebo-controlled period of the extension study. Mean change in 6MWD from baseline was highly variable across treatment groups, but indicated progressive deterioration from weeks 24-104 in all treatment groups. Overall, 91.0% (n = 142) of participants in the pooled bimagrumab group and 89.1% (n = 49) in the placebo group had ≥1 treatment-emergent adverse event (AE). Falls were slightly higher in the bimagrumab 3 mg/kg group vs 10 mg/kg, 1 mg/kg, and placebo groups (69.2% [n = 36 of 52] vs 56.6% [n = 30 of 53], 58.8% [n = 30 of 51], and 61.8% [n = 34 of 55], respectively). The most frequently reported AEs in the pooled bimagrumab group were diarrhea 14.7% (n = 23), involuntary muscle contractions 9.6% (n = 15), and rash 5.1% (n = 8). Incidence of serious AEs was comparable between the pooled bimagrumab and the placebo group (18.6% [n = 29] vs 14.5% [n = 8], respectively).

Conclusion: Extended treatment with bimagrumab up to 2 years produced a good safety profile and was well-tolerated, but did not provide clinical benefits in terms of improvement in mobility. The extension study was terminated early due to core study not meeting its primary endpoint.

Clinical Trial Registration: Clinicaltrials.gov identifier NCT02573467.

Classification Of Evidence: This study provides Class IV evidence that for patients with sIBM, long-term treatment with bimagrumab was safe, well-tolerated, and did not provide meaningful functional benefit. The study is rated Class IV because of the open-label design of extension treatment period 2.
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http://dx.doi.org/10.1212/WNL.0000000000011626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8032371PMC
March 2021

Pathogenic Variants in the Myosin Chaperone UNC-45B Cause Progressive Myopathy with Eccentric Cores.

Am J Hum Genet 2020 12 19;107(6):1078-1095. Epub 2020 Nov 19.

Department of Clinical Genome Analysis, Medical Genome Center, National Center of Neurology and Psychiatry, 187-8551 Tokyo, Japan.

The myosin-directed chaperone UNC-45B is essential for sarcomeric organization and muscle function from Caenorhabditis elegans to humans. The pathological impact of UNC-45B in muscle disease remained elusive. We report ten individuals with bi-allelic variants in UNC45B who exhibit childhood-onset progressive muscle weakness. We identified a common UNC45B variant that acts as a complex hypomorph splice variant. Purified UNC-45B mutants showed changes in folding and solubility. In situ localization studies further demonstrated reduced expression of mutant UNC-45B in muscle combined with abnormal localization away from the A-band towards the Z-disk of the sarcomere. The physiological relevance of these observations was investigated in C. elegans by transgenic expression of conserved UNC-45 missense variants, which showed impaired myosin binding for one and defective muscle function for three. Together, our results demonstrate that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC-45B in myofibrillar organization.
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http://dx.doi.org/10.1016/j.ajhg.2020.11.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820787PMC
December 2020

The expanding genetic landscape of hereditary motor neuropathies.

Brain 2020 12;143(12):3540-3563

Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.

Hereditary motor neuropathies are clinically and genetically diverse disorders characterized by length-dependent axonal degeneration of lower motor neurons. Although currently as many as 26 causal genes are known, there is considerable missing heritability compared to other inherited neuropathies such as Charcot-Marie-Tooth disease. Intriguingly, this genetic landscape spans a discrete number of key biological processes within the peripheral nerve. Also, in terms of underlying pathophysiology, hereditary motor neuropathies show striking overlap with several other neuromuscular and neurological disorders. In this review, we provide a current overview of the genetic spectrum of hereditary motor neuropathies highlighting recent reports of novel genes and mutations or recent discoveries in the underlying disease mechanisms. In addition, we link hereditary motor neuropathies with various related disorders by addressing the main affected pathways of disease divided into five major processes: axonal transport, tRNA aminoacylation, RNA metabolism and DNA integrity, ion channels and transporters and endoplasmic reticulum.
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http://dx.doi.org/10.1093/brain/awaa311DOI Listing
December 2020

Reply: De novo SPTAN1 mutation in axonal sensorimotor neuropathy and developmental disorder.

Brain 2020 12;143(12):e105

Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.

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http://dx.doi.org/10.1093/brain/awaa345DOI Listing
December 2020

The genetic landscape of axonal neuropathies in the middle-aged and elderly: Focus on .

Neurology 2020 12 3;95(24):e3163-e3179. Epub 2020 Nov 3.

From the Friedrich-Baur-Institute (J.S., B.S.-W., M.W.), Department of Neurology, LMU Munich, Germany; DNA Laboratory (P.L., P.S.), Department of Pediatric Neurology, 2nd Faculty of Medicine, Charles University in Prague and University Hospital Motol, Czech Republic; Neuromuscular Unit (D.K., A.K.), Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland; Dr. John T. Macdonald Foundation Department of Human Genetics (L.A., A.R., S.Z.), John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, FL; Neurogenetics Group (J.B., T.D., P.D.J.), Center for Molecular Neurology, University of Antwerp; Institute Born-Bunge (J.B., T.D., P.D.J.), University of Antwerp; Neuromuscular Reference Centre (J.B., P.D.J.), Department of Neurology, Antwerp University Hospital, Belgium; Department of Clinical Chemistry and Laboratory Medicine (C.B.), Jena University Hospital; Centogene AG (C.B.), Rostock, Germany; Department of Medical Genetics (G.J.B., H.H.), Telemark Hospital Trust, Skien, Norway; Neurology Department (D.B., A.L., J. Weishaupt), Ulm University, Germany; Department of Neurology (J.D., D. Walk), University of Minnesota, Minneapolis; Department of Neurology (L.D.), Perelman School of Medicine at the University of Pennsylvania, Philadelphia; Department of Sleep Medicine and Neuromuscular Diseases (B.D., A.S., P.Y.), University of Münster; Institute of Human Genetics (K.E., I.K.), Medical Faculty, RWTH Aachen University, Germany; Sydney Medical School (M.E., M.K., G.N.), Concord Hospital, Northcott Neuroscience Laboratory, ANZAC Research Institute, Concord, Australia; Department of Orthopaedics and Trauma Surgery (C.F., K.K., D. Weinmann, R.W., S.T., M.A.-G.), Medical University of Vienna, Austria; AP-HP (T.S.), Institut de Myologie, Centre de référence des maladies neuromusculaires Nord/Est/Ile-de-France, G-H Pitié-Salpêtrière, Paris, France; Department of Neurology (D.N.H.), University of Rochester, NY; Department of Clinical Neurosciences (R.H.), University of Cambridge School of Clinical Medicine, UK; Department of Neurology (S.I.), Konventhospital der Barmherzigen Brüder Linz; Karl Chiari Lab for Orthopaedic Biology (K.K., D. Weinmann, S.T.), Department of Orthopedics and Trauma Surgery, Medical University of Vienna, Austria; Stanford Center for Undiagnosed Diseases (J.N.K.), Stanford, CA; Undiagnosed Diseases Network (UDN) (J.N.K., S.Z.); Centre for Medical Research (N.G.L., R.O., G.Ravenscroft), University of Western Australia, Nedlands; Harry Perkins Institute of Medical Research (N.G.L., R.O., G. Ravenscroft), Nedlands; Neurogenetic Unit (P.J.L.), Royal Perth Hospital, Perth, Australia; Department of Neurology (W.N.L., J. Wanschitz), Medical University of Innsbruck, Austria; Department of Neurosciences and Behavior (W.M.), Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil; Department of Neurology (S.P.), Hannover Medical School, Germany; Department of Clinical and Experimental Medicine (G. Ricci), University of Pisa, Italy; Institute of Human Genetics (S.R.-S.), Medical University of Innsbruck, Austria; Department of Neurodegenerative Diseases Hertie-Institute for Clinical Brain Research and Center of Neurology (L.S., R.S., M.S.), University of Tübingen; German Center for Neurodegenerative Diseases (DZNE) (L.S., R.S., M.S.), Tübingen, Germany; AP-HP (B.F.), Laboratoire de génétique moléculaire, pharmacogénétique et hormonologie, Hôpital de Bicêtre; Le Kremlin-Bicêtre, France; Institute of Human Genetics (T.M.S.), Helmholtz Zentrum Munich-German Research Center for Environmental Health, Neuherberg; Institute for Human Genetics (T.M.S.), Technical University Munich; and Institut für Klinische Genetik (J. Wagner), Technische Universität Dresden, Medizinische Fakultät Carl Gustav Carus, Germany.

Objective: To test the hypothesis that monogenic neuropathies such as Charcot-Marie-Tooth disease (CMT) contribute to frequent but often unexplained neuropathies in the elderly, we performed genetic analysis of 230 patients with unexplained axonal neuropathies and disease onset ≥35 years.

Methods: We recruited patients, collected clinical data, and conducted whole-exome sequencing (WES; n = 126) and single-gene sequencing (n = 104). We further queried WES repositories for variants and measured blood levels of the -encoded protein neprilysin.

Results: In the WES cohort, the overall detection rate for assumed disease-causing variants in genes for CMT or other conditions associated with neuropathies was 18.3% (familial cases 26.4%, apparently sporadic cases 12.3%). was most frequently involved and accounted for 34.8% of genetically solved cases. The relevance of for late-onset neuropathies was further supported by detection of a comparable proportion of cases in an independent patient sample, preponderance of variants among patients compared to population frequencies, retrieval of additional late-onset neuropathy patients with variants from WES repositories, and low neprilysin levels in patients' blood samples. Transmission of variants was often consistent with an incompletely penetrant autosomal-dominant trait and less frequently with autosomal-recessive inheritance.

Conclusions: A detectable fraction of unexplained late-onset axonal neuropathies is genetically determined, by variants in either CMT genes or genes involved in other conditions that affect the peripheral nerves and can mimic a CMT phenotype. variants can act as completely penetrant recessive alleles but also confer dominantly inherited susceptibility to axonal neuropathies in an aging population.
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http://dx.doi.org/10.1212/WNL.0000000000011132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7836667PMC
December 2020

Defining the clinical, molecular and imaging spectrum of adaptor protein complex 4-associated hereditary spastic paraplegia.

Brain 2020 10;143(10):2929-2944

Division of Neurology, Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, IA, USA.

Bi-allelic loss-of-function variants in genes that encode subunits of the adaptor protein complex 4 (AP-4) lead to prototypical yet poorly understood forms of childhood-onset and complex hereditary spastic paraplegia: SPG47 (AP4B1), SPG50 (AP4M1), SPG51 (AP4E1) and SPG52 (AP4S1). Here, we report a detailed cross-sectional analysis of clinical, imaging and molecular data of 156 patients from 101 families. Enrolled patients were of diverse ethnic backgrounds and covered a wide age range (1.0-49.3 years). While the mean age at symptom onset was 0.8 ± 0.6 years [standard deviation (SD), range 0.2-5.0], the mean age at diagnosis was 10.2 ± 8.5 years (SD, range 0.1-46.3). We define a set of core features: early-onset developmental delay with delayed motor milestones and significant speech delay (50% non-verbal); intellectual disability in the moderate to severe range; mild hypotonia in infancy followed by spastic diplegia (mean age: 8.4 ± 5.1 years, SD) and later tetraplegia (mean age: 16.1 ± 9.8 years, SD); postnatal microcephaly (83%); foot deformities (69%); and epilepsy (66%) that is intractable in a subset. At last follow-up, 36% ambulated with assistance (mean age: 8.9 ± 6.4 years, SD) and 54% were wheelchair-dependent (mean age: 13.4 ± 9.8 years, SD). Episodes of stereotypic laughing, possibly consistent with a pseudobulbar affect, were found in 56% of patients. Key features on neuroimaging include a thin corpus callosum (90%), ventriculomegaly (65%) often with colpocephaly, and periventricular white-matter signal abnormalities (68%). Iron deposition and polymicrogyria were found in a subset of patients. AP4B1-associated SPG47 and AP4M1-associated SPG50 accounted for the majority of cases. About two-thirds of patients were born to consanguineous parents, and 82% carried homozygous variants. Over 70 unique variants were present, the majority of which are frameshift or nonsense mutations. To track disease progression across the age spectrum, we defined the relationship between disease severity as measured by several rating scales and disease duration. We found that the presence of epilepsy, which manifested before the age of 3 years in the majority of patients, was associated with worse motor outcomes. Exploring genotype-phenotype correlations, we found that disease severity and major phenotypes were equally distributed among the four subtypes, establishing that SPG47, SPG50, SPG51 and SPG52 share a common phenotype, an 'AP-4 deficiency syndrome'. By delineating the core clinical, imaging, and molecular features of AP-4-associated hereditary spastic paraplegia across the age spectrum our results will facilitate early diagnosis, enable counselling and anticipatory guidance of affected families and help define endpoints for future interventional trials.
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http://dx.doi.org/10.1093/brain/awz307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7780481PMC
October 2020

De Novo and Inherited Variants in GBF1 are Associated with Axonal Neuropathy Caused by Golgi Fragmentation.

Am J Hum Genet 2020 10 15;107(4):763-777. Epub 2020 Sep 15.

Institute of Human Genetics, Center for Molecular Medicine Cologne, Center for Rare Diseases Cologne, and Institute for Genetics, University of Cologne, 50931 Cologne, Germany. Electronic address:

Distal hereditary motor neuropathies (HMNs) and axonal Charcot-Marie-Tooth neuropathy (CMT2) are clinically and genetically heterogeneous diseases characterized primarily by motor neuron degeneration and distal weakness. The genetic cause for about half of the individuals affected by HMN/CMT2 remains unknown. Here, we report the identification of pathogenic variants in GBF1 (Golgi brefeldin A-resistant guanine nucleotide exchange factor 1) in four unrelated families with individuals affected by sporadic or dominant HMN/CMT2. Genomic sequencing analyses in seven affected individuals uncovered four distinct heterozygous GBF1 variants, two of which occurred de novo. Other known HMN/CMT2-implicated genes were excluded. Affected individuals show HMN/CMT2 with slowly progressive distal muscle weakness and musculoskeletal deformities. Electrophysiological studies confirmed axonal damage with chronic neurogenic changes. Three individuals had additional distal sensory loss. GBF1 encodes a guanine-nucleotide exchange factor that facilitates the activation of members of the ARF (ADP-ribosylation factor) family of small GTPases. GBF1 is mainly involved in the formation of coatomer protein complex (COPI) vesicles, maintenance and function of the Golgi apparatus, and mitochondria migration and positioning. We demonstrate that GBF1 is present in mouse spinal cord and muscle tissues and is particularly abundant in neuropathologically relevant sites, such as the motor neuron and the growth cone. Consistent with the described role of GBF1 in Golgi function and maintenance, we observed marked increase in Golgi fragmentation in primary fibroblasts derived from all affected individuals in this study. Our results not only reinforce the existing link between Golgi fragmentation and neurodegeneration but also demonstrate that pathogenic variants in GBF1 are associated with HMN/CMT2.
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http://dx.doi.org/10.1016/j.ajhg.2020.08.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7491385PMC
October 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 Neurology, Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.

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

Tempering our metrics: Finding new ways to refine tried and true instruments.

Neurology 2020 03 10;94(9):373-374. Epub 2020 Feb 10.

From the Department of Neurology (V.H.L.), Dartmouth-Hitchcock Medical Center and Dartmouth College Geisel School of Medicine, Lebanon, NH; and Neuromuscular Reference Center (J.B.), Antwerp University Hospital and Faculty of Medicine University of Antwerp, Belgium.

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http://dx.doi.org/10.1212/WNL.0000000000009028DOI Listing
March 2020

Multisystem proteinopathy due to a homozygous p.Arg159His mutation: A tale of the unexpected.

Neurology 2020 02 17;94(8):e785-e796. Epub 2019 Dec 17.

From the Neurogenetics Group (W.D.R., P.D.J., J.B.), Laboratory of Neuromuscular Pathology (W.D.R., P.D.J., J.B.), Institute Born-Bunge, Neuromics Support Facility (A.A.), VIB-UAntwerp Center for Molecular Neurology, and Receptor Biology Lab (S.M.), Department of Biomedical Sciences, University of Antwerp; Neuromuscular Reference Centre (W.D.R., P.D.J., J.B.), Department of Neurology, Antwerp University Hospital, Belgium; Institute of Neuropathology (C.S.C., R.S.), University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen; Centre for Biochemistry (C.S.C., L.E.), Institute of Biochemistry I, and Center for Physiology and Pathophysiology (C.S.C.), Institute of Vegetative Physiology, Medical Faculty, University of Cologne, Germany; Griffith Institute for Drug Discovery (A.H), Griffith University, Nathan, Brisbane, Queensland; Department of Veterinary Biosciences (A.H.), Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia; John Walton Muscular Dystrophy Research Centre (K.J., A.T., V.S.), Institute of Genetic Medicine, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle-Upon-Tyne, UK; and Laboratory for Neuropathology (J.L.D.B.), Division of Neurology, Ghent University Hospital, Belgium.

Objective: To assess the clinical, radiologic, myopathologic, and proteomic findings in a patient manifesting a multisystem proteinopathy due to a homozygous valosin-containing protein gene () mutation previously reported to be pathogenic in the heterozygous state.

Methods: We studied a 36-year-old male index patient and his father, both presenting with progressive limb-girdle weakness. Muscle involvement was assessed by MRI and muscle biopsies. We performed whole-exome sequencing and Sanger sequencing for segregation analysis of the identified p.Arg159His mutation. To dissect biological disease signatures, we applied state-of-the-art quantitative proteomics on muscle tissue of the index case, his father, 3 additional patients with -related myopathy, and 3 control individuals.

Results: The index patient, homozygous for the known p.Arg159His mutation in , manifested a typical -related myopathy phenotype, although with a markedly high creatine kinase value and a relatively early disease onset, and Paget disease of bone. The father exhibited a myopathy phenotype and discrete parkinsonism, and multiple deceased family members on the maternal side of the pedigree displayed a dementia, parkinsonism, or myopathy phenotype. Bioinformatic analysis of quantitative proteomic data revealed the degenerative nature of the disease, with evidence suggesting selective failure of muscle regeneration and stress granule dyshomeostasis.

Conclusion: We report a patient showing a multisystem proteinopathy due to a homozygous mutation. The patient manifests a severe phenotype, yet fundamental disease characteristics are preserved. Proteomic findings provide further insights into -related pathomechanisms.
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http://dx.doi.org/10.1212/WNL.0000000000008763DOI Listing
February 2020

Functional characterization of GYG1 variants in two patients with myopathy and glycogenin-1 deficiency.

Neuromuscul Disord 2019 12 23;29(12):951-960. Epub 2019 Oct 23.

Department of Pathology and Genetics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.

Glycogen storage disease XV is caused by variants in the glycogenin-1 gene, GYG1, and presents as a predominant skeletal myopathy or cardiomyopathy. We describe two patients with late-onset myopathy and biallelic GYG1 variants. In patient 1, the novel c.144-2A>G splice acceptor variant and the novel frameshift variant c.631delG (p.Val211Cysfs*30) were identified, and in patient 2, the previously described c.304G>C (p.Asp102His) and c.487delG (p.Asp163Thrfs*5) variants were found. Protein analysis showed total absence of glycogenin-1 expression in patient 1, whereas in patient 2 there was reduced expression of glycogenin-1, with the residual protein being non-functional. Both patients showed glycogen and polyglucosan storage in their muscle fibers, as revealed by PAS staining and electron microscopy. Age at onset of the myopathy phenotype was 53 years and 70 years respectively, with the selective pattern of muscle involvement on MRI corroborating the pattern of weakness. Cardiac evaluation of patient 1 and 2 did not show any specific abnormalities linked to the glycogenin-1 deficiency. In patient 2, who was shown to express the p.Asp102His mutated glycogenin-1, cardiac evaluation was still normal at age 77 years. This contrasts with the association of the p.Asp102His variant in homozygosity with a severe cardiomyopathy in several cases with an onset age between 30 and 50 years. This finding might indicate that the level of p.Asp102His mutated glycogenin-1 determines if a patient will develop a cardiomyopathy.
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http://dx.doi.org/10.1016/j.nmd.2019.10.002DOI Listing
December 2019

Defects in Axonal Transport in Inherited Neuropathies.

J Neuromuscul Dis 2019 ;6(4):401-419

Peripheral Neuropathy Research Group, Department of Biomedical Sciences, University of Antwerp, Antwerpen, Belgium.

Axonal transport is a highly complex process essential for sustaining proper neuronal functioning. Disturbances can result in an altered neuronal homeostasis, aggregation of cargoes, and ultimately a dying-back degeneration of neurons. The impact of dysfunction in axonal transport is shown by genetic defects in key proteins causing a broad spectrum of neurodegenerative diseases, including inherited peripheral neuropathies. In this review, we provide an overview of the cytoskeletal components, molecular motors and adaptor proteins involved in axonal transport mechanisms and their implication in neuronal functioning. In addition, we discuss the involvement of axonal transport dysfunction in neurodegenerative diseases with a particular focus on inherited peripheral neuropathies. Lastly, we address some recent scientific advances most notably in therapeutic strategies employed in the area of axonal transport, patient-derived iPSC models, in vivo animal models, antisense-oligonucleotide treatments, and novel chemical compounds.
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http://dx.doi.org/10.3233/JND-190427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6918914PMC
April 2020

CMT disease severity correlates with mutation-induced open conformation of histidyl-tRNA synthetase, not aminoacylation loss, in patient cells.

Proc Natl Acad Sci U S A 2019 09 9;116(39):19440-19448. Epub 2019 Sep 9.

Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037;

Aminoacyl-transfer RNA (tRNA) synthetases (aaRSs) are the largest protein family causatively linked to neurodegenerative Charcot-Marie-Tooth (CMT) disease. Dominant mutations cause the disease, and studies of CMT disease-causing mutant glycyl-tRNA synthetase (GlyRS) and tyrosyl-tRNA synthetase (TyrRS) showed their mutations create neomorphic structures consistent with a gain-of-function mechanism. In contrast, based on a yeast model, loss of aminoacylation function was reported for CMT disease mutants in histidyl-tRNA synthetase (HisRS). However, neither that nor prior work of any CMT disease-causing aaRS investigated the aminoacylation status of tRNAs in the cellular milieu of actual patients. Using an assay that interrogated aminoacylation levels in patient cells, we investigated a HisRS-linked CMT disease family with the most severe disease phenotype. Strikingly, no difference in charged tRNA levels between normal and diseased family members was found. In confirmation, recombinant versions of 4 other HisRS CMT disease-causing mutants showed no correlation between activity loss in vitro and severity of phenotype in vivo. Indeed, a mutation having the most detrimental impact on activity was associated with a mild disease phenotype. In further work, using 3 independent biophysical analyses, structural opening (relaxation) of mutant HisRSs at the dimer interface best correlated with disease severity. In fact, the HisRS mutation in the severely afflicted patient family caused the largest degree of structural relaxation. These data suggest that HisRS-linked CMT disease arises from open conformation-induced mechanisms distinct from loss of aminoacylation.
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http://dx.doi.org/10.1073/pnas.1908288116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6765236PMC
September 2019

Safety and efficacy of intravenous bimagrumab in inclusion body myositis (RESILIENT): a randomised, double-blind, placebo-controlled phase 2b trial.

Lancet Neurol 2019 09;18(9):834-844

Center for Neuromuscular Diseases, Unit of Neurology, Azienda Socio Sanitaria Territoriale Spedali Civili and University of Brescia, Brescia, Italy.

Background: Inclusion body myositis is an idiopathic inflammatory myopathy and the most common myopathy affecting people older than 50 years. To date, there are no effective drug treatments. We aimed to assess the safety, efficacy, and tolerability of bimagrumab-a fully human monoclonal antibody-in individuals with inclusion body myositis.

Methods: We did a multicentre, double-blind, placebo-controlled study (RESILIENT) at 38 academic clinical sites in Australia, Europe, Japan, and the USA. Individuals (aged 36-85 years) were eligible for the study if they met modified 2010 Medical Research Council criteria for inclusion body myositis. We randomly assigned participants (1:1:1:1) using a blocked randomisation schedule (block size of four) to either bimagrumab (10 mg/kg, 3 mg/kg, or 1 mg/kg) or placebo matched in appearance to bimagrumab, administered as intravenous infusions every 4 weeks for at least 48 weeks. All study participants, the funder, investigators, site personnel, and people doing assessments were masked to treatment assignment. The primary outcome measure was 6-min walking distance (6MWD), which was assessed at week 52 in the primary analysis population and analysed by intention-to-treat principles. We used a multivariate normal repeated measures model to analyse data for 6MWD. Safety was assessed by recording adverse events and by electrocardiography, echocardiography, haematological testing, urinalysis, and blood chemistry. This trial is registered with ClinicalTrials.gov, number NCT01925209; this report represents the final analysis.

Findings: Between Sept 26, 2013, and Jan 6, 2016, 251 participants were enrolled to the study, of whom 63 were assigned to each bimagrumab group and 62 were allocated to the placebo group. At week 52, 6MWD change from baseline did not differ between any bimagrumab dose and placebo (least squares mean treatment difference for bimagrumab 10 mg/kg group, 17·6 m, SE 14·3, 99% CI -19·6 to 54·8; p=0·22; for 3 mg/kg group, 18·6 m, 14·2, -18·2 to 55·4; p=0·19; and for 1 mg/kg group, -1·3 m, 14·1, -38·0 to 35·4; p=0·93). 63 (100%) participants in each bimagrumab group and 61 (98%) of 62 in the placebo group had at least one adverse event. Falls were the most frequent adverse event (48 [76%] in the bimagrumab 10 mg/kg group, 55 [87%] in the 3 mg/kg group, 54 [86%] in the 1 mg/kg group, and 52 [84%] in the placebo group). The most frequently reported adverse events with bimagrumab were muscle spasms (32 [51%] in the bimagrumab 10 mg/kg group, 43 [68%] in the 3 mg/kg group, 25 [40%] in the 1 mg/kg group, and 13 [21%] in the placebo group) and diarrhoea (33 [52%], 28 [44%], 20 [32%], and 11 [18%], respectively). Adverse events leading to discontinuation were reported in four (6%) participants in each bimagrumab group compared with one (2%) participant in the placebo group. At least one serious adverse event was reported by 21 (33%) participants in the 10 mg/kg group, 11 (17%) in the 3 mg/kg group, 20 (32%) in the 1 mg/kg group, and 20 (32%) in the placebo group. No significant adverse cardiac effects were recorded on electrocardiography or echocardiography. Two deaths were reported during the study, one attributable to subendocardial myocardial infarction (secondary to gastrointestinal bleeding after an intentional overdose of concomitant sedatives and antidepressants) and one attributable to lung adenocarcinoma. Neither death was considered by the investigator to be related to bimagrumab.

Interpretation: Bimagrumab showed a good safety profile, relative to placebo, in individuals with inclusion body myositis but did not improve 6MWD. The strengths of our study are that, to the best of our knowledge, it is the largest randomised controlled trial done in people with inclusion body myositis, and it provides important natural history data over 12 months.

Funding: Novartis Pharma.
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http://dx.doi.org/10.1016/S1474-4422(19)30200-5DOI Listing
September 2019

Nonsense mutations in alpha-II spectrin in three families with juvenile onset hereditary motor neuropathy.

Brain 2019 09;142(9):2605-2616

Neurogenetics Group, Center for Molecular Neurology, University of Antwerp, Belgium.

Distal hereditary motor neuropathies are a rare subgroup of inherited peripheral neuropathies hallmarked by a length-dependent axonal degeneration of lower motor neurons without significant involvement of sensory neurons. We identified patients with heterozygous nonsense mutations in the αII-spectrin gene, SPTAN1, in three separate dominant hereditary motor neuropathy families via next-generation sequencing. Variable penetrance was noted for these mutations in two of three families, and phenotype severity differs greatly between patients. The mutant mRNA containing nonsense mutations is broken down by nonsense-mediated decay and leads to reduced protein levels in patient cells. Previously, dominant-negative αII-spectrin gene mutations were described as causal in a spectrum of epilepsy phenotypes.
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http://dx.doi.org/10.1093/brain/awz216DOI Listing
September 2019

FAHN/SPG35: a narrow phenotypic spectrum across disease classifications.

Brain 2019 06;142(6):1561-1572

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

The endoplasmic reticulum enzyme fatty acid 2-hydroxylase (FA2H) plays a major role in the formation of 2-hydroxy glycosphingolipids, main components of myelin. FA2H deficiency in mice leads to severe central demyelination and axon loss. In humans it has been associated with phenotypes from the neurodegeneration with brain iron accumulation (fatty acid hydroxylase-associated neurodegeneration, FAHN), hereditary spastic paraplegia (HSP type SPG35) and leukodystrophy (leukodystrophy with spasticity and dystonia) spectrum. We performed an in-depth clinical and retrospective neurophysiological and imaging study in a cohort of 19 cases with biallelic FA2H mutations. FAHN/SPG35 manifests with early childhood onset predominantly lower limb spastic tetraparesis and truncal instability, dysarthria, dysphagia, cerebellar ataxia, and cognitive deficits, often accompanied by exotropia and movement disorders. The disease is rapidly progressive with loss of ambulation after a median of 7 years after disease onset and demonstrates little interindividual variability. The hair of FAHN/SPG35 patients shows a bristle-like appearance; scanning electron microscopy of patient hair shafts reveals deformities (longitudinal grooves) as well as plaque-like adhesions to the hair, likely caused by an abnormal sebum composition also described in a mouse model of FA2H deficiency. Characteristic imaging features of FAHN/SPG35 can be summarized by the 'WHAT' acronym: white matter changes, hypointensity of the globus pallidus, ponto-cerebellar atrophy, and thin corpus callosum. At least three of four imaging features are present in 85% of FA2H mutation carriers. Here, we report the first systematic, large cohort study in FAHN/SPG35 and determine the phenotypic spectrum, define the disease course and identify clinical and imaging biomarkers.
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http://dx.doi.org/10.1093/brain/awz102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6536916PMC
June 2019

Muscular dystrophy with arrhythmia caused by loss-of-function mutations in .

Neurol Genet 2019 Apr 1;5(2):e321. Epub 2019 Apr 1.

Neurogenetics Group (W.D.R., P.D.J., J.B.), University of Antwerp; the Laboratory of Neuromuscular Pathology (W.D.R., P.D.J., J.B.), Institute Born- Bunge, University of Antwerp; the Neuromuscular Reference Centre (W.D.R., P.D.J., J.B.), Department of Neurology, Antwerp University Hospital, Belgium; Sorbonne Université (I.N., M.B., R.B.Y., G.B.), INSERM U974, Center of Research in Myology, Institute of Myology, G.H. Pitié-Salpêtrière Paris, France; Histology and Cellular Imaging (B.A.), Neuromics Support Facility, VIB-UAntwerp Center for Molecular Neurology, University of Antwerp; Laboratory for Neuropathology (B.D.P., J.D.B.), Division of Neurology, Ghent University Hospital, Belgium; AP-HP, Centre de Référence de Pathologie Neuromusculaire Nord/Est/Ile-deFrance (R.B.Y., B.E.), G.H. Pitié-Salpêtrière, Bioinformatics Unit (C.M.), Necker Hospital, AP-HP, and University Paris Descartes, ; Centre National de Recherche en Génomique Humaine (CNRGH) (A.B., J.F.D.), Institut de Biologie François Jacob, CEA, Université Paris-Saclay, Evry; Laboratoire de Neuropathologie (T.M.), G.H. Pitié-Salpêtrière, Paris, France; Center for Medical Genetics (S.S.), Ghent University Hospital, Belgium; Developmental Dynamics, Imperial Centre for Experimental and Translational Medicine (R.S., T.B.), Imperial College London; John Walton Muscular Dystrophy Research Centre (K.J., A.T., V.S.), MRC Centre for Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.

Objective: To study the genetic and phenotypic spectrum of patients harboring recessive mutations in .

Methods: We performed whole-exome sequencing in a multicenter cohort of 1929 patients with a suspected hereditary myopathy, showing unexplained limb-girdle muscular weakness and/or elevated creatine kinase levels. Immunohistochemistry and mRNA experiments on patients' skeletal muscle tissue were performed to study the pathogenicity of identified loss-of-function (LOF) variants in .

Results: We identified 4 individuals from 3 families harboring homozygous LOF variants in , the gene that encodes for Popeye domain containing protein 1 (POPDC1). Patients showed skeletal muscle involvement and cardiac conduction abnormalities of varying nature and severity, but all exhibited at least subclinical signs of both skeletal muscle and cardiac disease. All identified mutations lead to a partial or complete loss of function of through nonsense-mediated decay or through functional changes to the POPDC1 protein.

Conclusions: We report the identification of homozygous LOF mutations in , causal in a young adult-onset myopathy with concomitant cardiac conduction disorders in the absence of structural heart disease. These findings underline the role of POPDC1, and by extension, other members of this protein family, in striated muscle physiology and disease. This disorder appears to have a low prevalence, although it is probably underdiagnosed because of its striking phenotypic variability and often subtle yet clinically relevant manifestations, particularly concerning the cardiac conduction abnormalities.
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http://dx.doi.org/10.1212/NXG.0000000000000321DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6501641PMC
April 2019

Exertional rhabdomyolysis: Relevance of clinical and laboratory findings, and clues for investigation.

Anaesth Intensive Care 2019 Mar 9;47(2):128-133. Epub 2019 May 9.

2 Department of Neurology, University Hospital Antwerp, Belgium.

Some degree of exertional rhabdomyolysis (ER), striated muscle breakdown associated with strenuous exercise, is a well-known phenomenon associated with endurance sports. However in rare cases, severe and/or recurrent ER is a manifestation of an underlying condition, which puts patients at risk for significant morbidity and mortality. Selecting the patients that need a diagnostic work up of an acute rhabdomyolysis episode is an important task. Based on the diagnostic work up of three illustrative patients treated in our hospital, retrospectively using the 'RHABDO' screening tool, we discuss the clinical and biochemical clues that should trigger further investigation for an underlying condition. Finally, we describe the most common genetic causes of this clinical syndrome.
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http://dx.doi.org/10.1177/0310057X19835830DOI Listing
March 2019

Loss of paraplegin drives spasticity rather than ataxia in a cohort of 241 patients with .

Neurology 2019 06 8;92(23):e2679-e2690. Epub 2019 May 8.

From Sorbonne Université (G.C., C.E., B.F., M.-L.M., F.M., M.P., C.-S.D., G.S., A.D.), Institut du Cerveau et de la Moelle épinière (ICM), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière; Department of Genetics (G.C., C.E., M.-L.M., P.C., F.M., G.B., G.S., A.D.), Pitié-Salpêtrière Charles-Foix University Hospital, Assistance publique-Hôpitaux de Paris, Sorbonne Université, Paris, France; Center for Neurology and Hertie Institute for Clinical Brain Research (R.S., M.S., L.S.), University of Tübingen, German Center for Neurodegenerative Diseases; German Center for Neurodegenerative Diseases (R.S., M.S., L.S.), Tübingen; Department of Neurology (B.P.C.v.d.W., E.G.H.), Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands; Neurogenetics Group (P.D.J., J.B., T.D., P.M., J.D.B., M.D.), University of Antwerp; Laboratories of Neurogenetics and Neuromuscular Pathology (P.D.J., J.B., T.D., P.M., J.D.B., M.D.), Institute Born-Bunge, University of Antwerp; Department of Neurology (P.D.J., J.B., T.D., P.M., J.D.B., M.D.), Antwerp University Hospital, Belgium; Scientific Institute IRCCS "E. Medea" (A.M.), Conegliano, Italy; Department of Neurology (M.A.), Hôpital de Hautepierre, Strasbourg; Institut de Génétique et de Biologie Moléculaire et Cellulaire (M.A.), INSERM-U964/CNRS-UMR7104/Université de Strasbourg, Illkirch; Fédération de Médecine Translationnelle de Strasbourg (M.A.), Université de Strasbourg; Department of Neurology (B.F.), Pitié-Salpêtrière Charles-Foix University Hospital, Assistance publique-Hôpitaux de Paris, Sorbonne Université, France; Department of Neurology (T. Klockgether, D.K.), University of Bonn; German Center for Neurodegenerative Diseases (T. Klockgether, D.K.), Bonn; Scientific Institute IRCCS E. Medea Neurorehabilitation Unit (M.G.D.), Bosisio Parini, Lecco, Italy; ULB Center of Human Genetics (I.M.), Brussels, Belgium; Scientific Institute IRCCS E. Medea Laboratory of Molecular Biology (M.T.B.), Bosisio Parini, Lecco, Italy; Department of Neurology With Friedrich-Baur Institute (T. Klopstock), University Hospital of the Ludwig-Maximilians-Universität München; German Center for Neurodegenerative Diseases (T. Klopstock); Munich Cluster for Systems Neurology (T. Klopstock), Germany; Department of Genetics (E.O.-R.), Croix-Rousse University Hospital, Lyon, France; Department of Neurology (C.K.), University of Rostock, Germany; Ecole Pratique des Hautes Etudes (M.P., G.S.), PSL Research University; Sorbonne Université (S.T.d.M.), INSERM, Institut Pierre Louis de Santé Publique, Medical Information Unit, Pitié-Salpêtrière Charles-Foix University Hospital, Assistance publique-Hôpitaux de Paris; and Raymond Escourolle Neuropathology Department (D.S., C.D.), Pitié-Salpêtrière University Hospital, Assistance publique-Hôpitaux de Paris, Sorbonne Université, France.

Objective: We took advantage of a large multinational recruitment to delineate genotype-phenotype correlations in a large, trans-European multicenter cohort of patients with spastic paraplegia gene 7 ().

Methods: We analyzed clinical and genetic data from 241 patients with , integrating neurologic follow-up data. One case was examined neuropathologically.

Results: Patients with had a mean age of 35.5 ± 14.3 years (n = 233) at onset and presented with spasticity (n = 89), ataxia (n = 74), or both (n = 45). At the first visit, patients with a longer disease duration (>20 years, n = 62) showed more cerebellar dysarthria ( < 0.05), deep sensory loss ( < 0.01), muscle wasting ( < 0.01), ophthalmoplegia ( < 0.05), and sphincter dysfunction ( < 0.05) than those with a shorter duration (<10 years, n = 93). Progression, measured by Scale for the Assessment and Rating of Ataxia evaluations, showed a mean annual increase of 1.0 ± 1.4 points in a subgroup of 30 patients. Patients homozygous for loss of function (LOF) variants (n = 65) presented significantly more often with pyramidal signs ( < 0.05), diminished visual acuity due to optic atrophy ( < 0.0001), and deep sensory loss ( < 0.0001) than those with at least 1 missense variant (n = 176). Patients with at least 1 Ala510Val variant (58%) were older (age 37.6 ± 13.7 vs 32.8 ± 14.6 years, < 0.05) and showed ataxia at onset ( < 0.05). Neuropathologic examination revealed reduction of the pyramidal tract in the medulla oblongata and moderate loss of Purkinje cells and substantia nigra neurons.

Conclusions: This is the largest cohort study to date and shows a spasticity-predominant phenotype of LOF variants and more frequent cerebellar ataxia and later onset in patients carrying at least 1 Ala510Val variant.
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http://dx.doi.org/10.1212/WNL.0000000000007606DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6556095PMC
June 2019
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