Publications by authors named "Michaela Auer-Grumbach"

78 Publications

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

Brain 2021 May 10. Epub 2021 May 10.

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
May 2021

ATTR amyloidosis during the COVID-19 pandemic: insights from a global medical roundtable.

Orphanet J Rare Dis 2021 05 6;16(1):204. Epub 2021 May 6.

Section of Cardiovascular Medicine, Department of Medicine and Amyloidosis Center, Boston University School of Medicine, Boston Medical Center, Boston, MA, USA.

Background: The global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causing the ongoing coronavirus disease 2019 (COVID-19) pandemic has raised serious concern for patients with chronic disease. A correlation has been identified between the severity of COVID-19 and a patient's preexisting comorbidities. Although COVID-19 primarily involves the respiratory system, dysfunction in multiple organ systems is common, particularly in the cardiovascular, gastrointestinal, immune, renal, and nervous systems. Patients with amyloid transthyretin (ATTR) amyloidosis represent a population particularly vulnerable to COVID-19 morbidity due to the multisystem nature of ATTR amyloidosis.

Main Body: ATTR amyloidosis is a clinically heterogeneous progressive disease, resulting from the accumulation of amyloid fibrils in various organs and tissues. Amyloid deposition causes multisystem clinical manifestations, including cardiomyopathy and polyneuropathy, along with gastrointestinal symptoms and renal dysfunction. Given the potential for exacerbation of organ dysfunction, physicians note possible unique challenges in the management of patients with ATTR amyloidosis who develop multiorgan complications from COVID-19. While the interplay between COVID-19 and ATTR amyloidosis is still being evaluated, physicians should consider that the heightened susceptibility of patients with ATTR amyloidosis to multiorgan complications might increase their risk for poor outcomes with COVID-19.

Conclusion: Patients with ATTR amyloidosis are suspected to have a higher risk of morbidity and mortality due to age and underlying ATTR amyloidosis-related organ dysfunction. While further research is needed to characterize this risk and management implications, ATTR amyloidosis patients might require specialized management if they develop COVID-19. The risks of delaying diagnosis or interrupting treatment for patients with ATTR amyloidosis should be balanced with the risk of exposure in the health care setting. Both physicians and patients must adapt to a new construct for care during and possibly after the pandemic to ensure optimal health for patients with ATTR amyloidosis, minimizing treatment interruptions.
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http://dx.doi.org/10.1186/s13023-021-01834-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8100737PMC
May 2021

Diagnosis and treatment of cardiac amyloidosis: an interdisciplinary consensus statement.

Wien Klin Wochenschr 2020 Dec 3;132(23-24):742-761. Epub 2020 Dec 3.

Department of Internal Medicine II, Division of Cardiology, Medical University of Vienna, Vienna, Austria.

The prevalence and significance of cardiac amyloidosis have been considerably underestimated in the past; however, the number of patients diagnosed with cardiac amyloidosis has increased significantly recently due to growing awareness of the disease, improved diagnostic capabilities and demographic trends. Specific therapies that improve patient prognosis have become available for certain types of cardiac amyloidosis. Thus, the earliest possible referral of patients with suspicion of cardiac amyloidosis to an experienced center is crucial to ensure rapid diagnosis, early initiation of treatment, and structured patient care. This requires intensive collaboration across several disciplines, and between resident physicians and specialized centers. The aim of this consensus statement is to provide guidance for the rapid and efficient diagnosis and treatment of light-chain amyloidosis and transthyretin amyloidosis, which are the most common forms of cardiac amyloidosis.
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http://dx.doi.org/10.1007/s00508-020-01781-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7732807PMC
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

Hereditary ATTR Amyloidosis in Austria: Prevalence and Epidemiological Hot Spots.

J Clin Med 2020 Jul 14;9(7). Epub 2020 Jul 14.

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

Background: Hereditary transthyretin amyloidosis (hATTR) is an autosomal dominantly inherited disorder caused by an accumulation of amyloid fibrils in tissues due to mutations in the transthyretin () gene. The prevalence of hATTR is still unclear and likely underestimated in many countries. In order to apply new therapies in a targeted manner, early diagnosis and knowledge of phenotype-genotype correlations are mandatory. This study aimed to assess the prevalence and phenotypic spectrum of hATTR in Austria.

Methods: Within the period of 2014-2019, patients with ATTR-associated cardiomyopathy and/or unexplained progressive polyneuropathies were screened for mutations in the gene.

Results: We identified 43 cases from 22 families carrying 10 different missense mutations and confirmed two mutational hot spots at c.323A>G (p.His108Arg) and c.337G>C (p.Val113Leu). Two further patients with late onset ATTR carried variants of unknown significance. The majority of patients initially presented with heart failure symptoms that were subsequently accompanied by progressive polyneuropathy in most cases. A total of 55% had a history of carpal tunnel syndrome before the onset of other organ manifestations.

Conclusions: Our study underlined the relevance of hATTR in the pathogenesis of amyloid-driven cardiomyopathy and axonal polyneuropathy and indicated considerable genetic heterogeneity of this disease in the Austrian population. The estimated prevalence of hATTR in Austria based on this study is 1:200,000 but a potentially higher number of unknown cases must be taken into account. With respect to new therapeutic approaches, we strongly propose genetic testing of the gene in an extended cohort of patients with unexplained heart failure and progressive polyneuropathy.
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http://dx.doi.org/10.3390/jcm9072234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7408866PMC
July 2020

Chance or challenge, spoilt for choice? New recommendations on diagnostic and therapeutic considerations in hereditary transthyretin amyloidosis with polyneuropathy: the German/Austrian position and review of the literature.

J Neurol 2020 Jun 4. Epub 2020 Jun 4.

Department of Neurology, Charité University Medicine, Berlin, Germany.

Hereditary transthyretin amyloidosis is caused by pathogenic variants (ATTR) in the TTR gene. Alongside cardiac dysfunction, the disease typically manifests with a severely progressive sensorimotor and autonomic polyneuropathy. Three different drugs, tafamidis, patisiran, and inotersen, are approved in several countries, including the European Union and the United States of America. By stabilizing the TTR protein or degrading its mRNA, all types of treatment aim at preventing amyloid deposition and stopping the otherwise fatal course. Therefore, it is of utmost importance to recognize both onset and progression of neuropathy as early as possible. To establish recommendations for diagnostic and therapeutic procedures in the follow-up of both pre-symptomatic mutation carriers and patients with manifest ATTR amyloidosis with polyneuropathy, German and Austrian experts elaborated a harmonized position. This paper is further based on a systematic review of the literature. Potential challenges in the early recognition of disease onset and progression are the clinical heterogeneity and the subjectivity of sensory and autonomic symptoms. Progression cannot be defined by a single test or score alone but has to be evaluated considering various disease aspects and their dynamics over time. The first-line therapy should be chosen based on individual symptom constellations and contra-indications. If symptoms worsen, this should promptly implicate to consider optimizing treatment. Due to the rareness and variability of ATTR amyloidosis, the clinical course is most importantly directive in doubtful cases. Therefore, a systematic follow-up at an experienced center is crucial to identify progression and reassure patients and carriers.
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http://dx.doi.org/10.1007/s00415-020-09962-6DOI Listing
June 2020

Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes.

Nat Genet 2020 05 4;52(5):473-481. Epub 2020 May 4.

Istituiti Clinici Scientifici Maugeri IRCCS, Environmental Research Center, Pavia, Italy.

Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy. We identified 45 individuals from 38 families across multiple ancestries carrying the nonsense c.757delG (p.Ala253GlnfsTer27) variant in SORD, in either a homozygous or compound heterozygous state. SORD is an enzyme that converts sorbitol into fructose in the two-step polyol pathway previously implicated in diabetic neuropathy. In patient-derived fibroblasts, we found a complete loss of SORD protein and increased intracellular sorbitol. Furthermore, the serum fasting sorbitol levels in patients were dramatically increased. In Drosophila, loss of SORD orthologs caused synaptic degeneration and progressive motor impairment. Reducing the polyol influx by treatment with aldose reductase inhibitors normalized intracellular sorbitol levels in patient-derived fibroblasts and in Drosophila, and also dramatically ameliorated motor and eye phenotypes. Together, these findings establish a novel and potentially treatable cause of neuropathy and may contribute to a better understanding of the pathophysiology of diabetes.
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http://dx.doi.org/10.1038/s41588-020-0615-4DOI Listing
May 2020

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

Linkage analysis and whole exome sequencing reveals AHNAK2 as a novel genetic cause for autosomal recessive CMT in a Malaysian family.

Neurogenetics 2019 08 22;20(3):117-127. Epub 2019 Apr 22.

Department of Biomedical Science, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.

Charcot-Marie-Tooth (CMT) disease is a form of inherited peripheral neuropathy that affects motor and sensory neurons. To identify the causative gene in a consanguineous family with autosomal recessive CMT (AR-CMT), we employed a combination of linkage analysis and whole exome sequencing. After excluding known AR-CMT genes, genome-wide linkage analysis mapped the disease locus to a 7.48-Mb interval on chromosome 14q32.11-q32.33, flanked by the markers rs2124843 and rs4983409. Whole exome sequencing identified two non-synonymous variants (p.T40P and p.H915Y) in the AHNAK2 gene that segregated with the disease in the family. Pathogenic predictions indicated that p.T40P is the likely causative allele. Analysis of AHNAK2 expression in the AR-CMT patient fibroblasts showed significantly reduced mRNA and protein levels. AHNAK2 binds directly to periaxin which is encoded by the PRX gene, and PRX mutations are associated with another form of AR-CMT (CMT4F). The altered expression of mutant AHNAK2 may disrupt the AHNAK2-PRX interaction in which one of its known functions is to regulate myelination.
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http://dx.doi.org/10.1007/s10048-019-00576-3DOI Listing
August 2019

Loss of Neurological Disease HSAN-I-Associated Gene SPTLC2 Impairs CD8 T Cell Responses to Infection by Inhibiting T Cell Metabolic Fitness.

Immunity 2019 05 2;50(5):1218-1231.e5. Epub 2019 Apr 2.

T Cell Metabolism Group (D140), German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Faculty of Biosciences, Heidelberg University, 69120 Heidelberg, Germany. Electronic address:

Patients with the neurological disorder HSAN-I suffer frequent infections, attributed to a lack of pain sensation and failure to seek care for minor injuries. Whether protective CD8 T cells are affected in HSAN-I patients remains unknown. Here, we report that HSAN-I-associated mutations in serine palmitoyltransferase subunit SPTLC2 dampened human T cell responses. Antigen stimulation and inflammation induced SPTLC2 expression, and murine T-cell-specific ablation of Sptlc2 impaired antiviral-T-cell expansion and effector function. Sptlc2 deficiency reduced sphingolipid biosynthetic flux and led to prolonged activation of the mechanistic target of rapamycin complex 1 (mTORC1), endoplasmic reticulum (ER) stress, and CD8 T cell death. Protective CD8 T cell responses in HSAN-I patient PBMCs and Sptlc2-deficient mice were restored by supplementing with sphingolipids and pharmacologically inhibiting ER stress-induced cell death. Therefore, SPTLC2 underpins protective immunity by translating extracellular stimuli into intracellular anabolic signals and antagonizes ER stress to promote T cell metabolic fitness.
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http://dx.doi.org/10.1016/j.immuni.2019.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6531359PMC
May 2019

Neuropathy-causing mutations in HSPB1 impair autophagy by disturbing the formation of SQSTM1/p62 bodies.

Autophagy 2019 06 31;15(6):1051-1068. Epub 2019 Jan 31.

a Peripheral Neuropathy Research Group , Institute Born Bunge and University of Antwerp , Antwerp , Belgium.

HSPB1 (heat shock protein family B [small] member 1) is a ubiquitously expressed molecular chaperone. Most mutations in HSPB1 cause axonal Charcot-Marie-Tooth neuropathy and/or distal hereditary motor neuropathy. In this study we show that mutations in HSPB1 lead to impairment of macroautophagic/autophagic flux. In HSPB1 knockout cells, we demonstrate that HSPB1 is necessary for autophagosome formation, which was rescued upon re-expression of HSPB1. Employing a label-free LC-MS/MS analysis on the various HSPB1 variants (wild type and mutants), we identified autophagy-specific interactors. We reveal that the wild-type HSPB1 protein binds to the autophagy receptor SQSTM1/p62 and that the PB1 domain of SQSTM1 is essential for this interaction. Mutations in HSPB1 lead to a decrease in the formation of SQSTM1/p62 bodies, and subsequent impairment of phagophore formation, suggesting a regulatory role for HSPB1 in autophagy via interaction with SQSTM1. Remarkably, autophagy deficits could also be confirmed in patient-derived motor neurons thereby indicating that the impairment of autophagy might be one of the pathomechanisms by which mutations in HSPB1 lead to peripheral neuropathy. Abbreviations: ACD: alpha-crystallin domain; ALS: amyotrophic lateral sclerosis; ATG14: autophagy related 14; BAG1/3: BCL2 associated athanogene 1/3; CMT: Charcot-Marie-Tooth; dHMN: distal hereditary motor neuropathy; GFP: green fluorescent protein; HSPA8: heat shock protein family A (Hsp70) member 8; HSPB1/6/8: heat shock protein family B (small) member 1/6/8; LIR: LC3-interacting region; LC3B: microtubule associated protein 1 light chain 3 beta; PB1: Phox and Bem1; SQSTM1: sequestosome 1; STUB1/CHIP: STIP1 homology and U-box containing protein 1; UBA: ubiquitin-associated; WIPI1: WD repeat domain, phosphoinositide interacting 1; WT: wild-type.
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http://dx.doi.org/10.1080/15548627.2019.1569930DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6526868PMC
June 2019

Development and validation of a TTR-specific copy number screening tool, and application to potentially relevant patient cohorts.

Mol Cell Probes 2018 10 21;41:61-63. Epub 2018 Aug 21.

Department of Clinical Chemistry and Laboratory Medicine, Jena University Hospital, Am Klinikum 1, 07747, Jena, Germany. Electronic address:

TTR amyloidosis (ATTR) is a fatal condition caused by extracellular deposits of misfolded transthyretin. Patients often present with cardiac disease, but manifestations may also involve other organs including the peripheral nervous system. ATTR is considered familial when heterozygous mutations in the TTR gene are present (ATTRmutant or ATTRm), or acquired when no TTR aberrations are detected (ATTRwildtype or ATTRwt). We hypothesized that TTR copy number variants (CNVs), which would escape the standard diagnostic approaches, contribute to ATTR-related phenotypes, and developed a multiplex ligation-dependent probe amplification-based (MLPA-based), TTR-specific copy number screening tool. High inter-sample and intra-sample homogeneity of MLPA signals and the expected drop in signal intensity for restriction digest-based positive controls validated this tool. Subsequent application to 13 patients diagnosed with ATTRwt, and to 93 patients presenting with late onset and presumably inherited polyneuropathy did not identify TTR CNVs. We discuss insufficient sensitivity of the assay as well as non-existence and non-pathogenicity of TTR CNVs as potentially underlying our negative finding, but suggest size and composition of our cohorts as more likely explanations. Our CNV-screening tool will be made available to initiatives interested in screening additional and potentially more appropriate patient samples.
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http://dx.doi.org/10.1016/j.mcp.2018.08.005DOI Listing
October 2018

Hereditary Neuropathies: Update 2017.

Neuropediatrics 2017 08 8;48(4):282-293. Epub 2017 Jun 8.

Friedrich-Baur-Institut, LMU Munich, Munich, Germany.

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http://dx.doi.org/10.1055/s-0037-1603518DOI Listing
August 2017

Mutant HSPB1 causes loss of translational repression by binding to PCBP1, an RNA binding protein with a possible role in neurodegenerative disease.

Acta Neuropathol Commun 2017 01 11;5(1). Epub 2017 Jan 11.

Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Institute Born Bunge and University of Antwerp, Antwerpen, Belgium.

The small heat shock protein HSPB1 (Hsp27) is an ubiquitously expressed molecular chaperone able to regulate various cellular functions like actin dynamics, oxidative stress regulation and anti-apoptosis. So far disease causing mutations in HSPB1 have been associated with neurodegenerative diseases such as distal hereditary motor neuropathy, Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis. Most mutations in HSPB1 target its highly conserved α-crystallin domain, while other mutations affect the C- or N-terminal regions or its promotor. Mutations inside the α-crystallin domain have been shown to enhance the chaperone activity of HSPB1 and increase the binding to client proteins. However, the HSPB1-P182L mutation, located outside and downstream of the α-crystallin domain, behaves differently. This specific HSPB1 mutation results in a severe neuropathy phenotype affecting exclusively the motor neurons of the peripheral nervous system. We identified that the HSPB1-P182L mutant protein has a specifically increased interaction with the RNA binding protein poly(C)binding protein 1 (PCBP1) and results in a reduction of its translational repressive activity. RNA immunoprecipitation followed by RNA sequencing on mouse brain lead to the identification of PCBP1 mRNA targets. These targets contain larger 3'- and 5'-UTRs than average and are enriched in an RNA motif consisting of the CTCCTCCTCCTCC consensus sequence. Interestingly, next to the clear presence of neuronal transcripts among the identified PCBP1 targets we identified known genes associated with hereditary peripheral neuropathies and hereditary spastic paraplegias. We therefore conclude that HSPB1 can mediate translational repression through interaction with an RNA binding protein further supporting its role in neurodegenerative disease.
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http://dx.doi.org/10.1186/s40478-016-0407-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5225548PMC
January 2017

Targeted Next-Generation Sequencing Reveals Novel TTN Mutations Causing Recessive Distal Titinopathy.

Mol Neurobiol 2017 11 29;54(9):7212-7223. Epub 2016 Oct 29.

Folkhälsan Institute of Genetics, Biomedicum Helsinki and Department of Medical Genetics, Haartman Institute, University of Helsinki, Haartmaninkatu 8, 00290, Helsinki, Finland.

Tibial muscular dystrophy (TMD) is the first described human titinopathy. It is a mild adult-onset slowly progressive myopathy causing weakness and atrophy in the anterior lower leg muscles. TMD is caused by mutations in the last two exons, Mex5 and Mex6, of the titin gene (TTN). The first reported TMD mutations were dominant, but the Finnish founder mutation FINmaj, an 11-bp insertion/deletion in Mex6, in homozygosity caused a completely different severe early-onset limb-girdle muscular dystrophy 2J (LGMD2J). Later, we reported that not all TMD mutations cause LGMD when homozygous or compound heterozygous with truncating mutation, but some of them rather cause a more severe TMD-like distal disease. We have now performed targeted next-generation sequencing of myopathy-related genes on seven families from Albania, Bosnia, Iran, Tunisia, Belgium, and Spain with juvenile or early adult onset recessive distal myopathy. Novel mutations in TTN Mex5, Mex6 and A-band exon 340 were identified in homozygosity or compound heterozygosity with a frameshift or nonsense mutation in TTN I- or A-band region. Family members having only one of these TTN mutations were healthy. Our results add yet another entity to the list of distal myopathies: juvenile or early adult onset recessive distal titinopathy.
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http://dx.doi.org/10.1007/s12035-016-0242-3DOI Listing
November 2017

Rare Variants in MME, Encoding Metalloprotease Neprilysin, Are Linked to Late-Onset Autosomal-Dominant Axonal Polyneuropathies.

Am J Hum Genet 2016 09;99(3):607-623

Department of Human Genetics and Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.

Axonal polyneuropathies are a frequent cause of progressive disability in the elderly. Common etiologies comprise diabetes mellitus, paraproteinaemia, and inflammatory disorders, but often the underlying causes remain elusive. Late-onset axonal Charcot-Marie-Tooth neuropathy (CMT2) is an autosomal-dominantly inherited condition that manifests in the second half of life and is genetically largely unexplained. We assumed age-dependent penetrance of mutations in a so far unknown gene causing late-onset CMT2. We screened 51 index case subjects with late-onset CMT2 for mutations by whole-exome (WES) and Sanger sequencing and subsequently queried WES repositories for further case subjects carrying mutations in the identified candidate gene. We studied nerve pathology and tissue levels and function of the abnormal protein in order to explore consequences of the mutations. Altogether, we observed heterozygous rare loss-of-function and missense mutations in MME encoding the metalloprotease neprilysin in 19 index case subjects diagnosed with axonal polyneuropathies or neurodegenerative conditions involving the peripheral nervous system. MME mutations segregated in an autosomal-dominant fashion with age-related incomplete penetrance and some affected individuals were isolated case subjects. We also found that MME mutations resulted in strongly decreased tissue availability of neprilysin and impaired enzymatic activity. Although neprilysin is known to degrade β-amyloid, we observed no increased amyloid deposition or increased incidence of dementia in individuals with MME mutations. Detection of MME mutations is expected to increase the diagnostic yield in late-onset polyneuropathies, and it will be tempting to explore whether substances that can elevate neprilysin activity could be a rational option for treatment.
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http://dx.doi.org/10.1016/j.ajhg.2016.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5011077PMC
September 2016

Whole exome sequencing in congenital pain insensitivity identifies a novel causative intronic NTRK1-mutation due to uniparental disomy.

Am J Med Genet B Neuropsychiatr Genet 2016 09 17;171(6):875-8. Epub 2016 May 17.

Department of Orthopaedics, Medical University Vienna, Vienna, Austria.

Congenital insensitivity to pain and anhidrosis (CIPA), also known as hereditary sensory and autonomic neuropathy type IV (HSAN IV), is characterized by recurrent episodes of unexplained high fever, loss of pain perception and temperature sensation, absent sweating, repeated traumatic and thermal injuries, and mild mental retardation. After exclusion of obviously pathogenic mutations in NTRK1, the most common cause of CIPA, whole exome sequencing (WES) was carried out in a CIPA patient with unrelated parents. No mutations in known HSAN genes were identified. However, filtering for genes carrying two rare sequence variations detected 13 homozygous single nucleotide variants (SNV), all being located on chromosome 1. Further analysis strongly suggested that this finding might be best explained by uniparental disomy of chromosome 1. Because NTRK1 is also located on chromosome 1, we re-evaluated WES data and detected a novel intronic sequence variation at position c.2188-12 C>A, homozygously because of uniparental disomy. Subsequent analysis of NTRK1 transcripts in peripheral blood cells of the patient revealed an influence of the variant on mRNA splicing. The C>A transversion generated a novel splice-site, which led to the incorporation of 10 intronic bases into the NTRK1 mRNA and consequently to a non-functional gene product. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.b.32458DOI Listing
September 2016

Cryptic Amyloidogenic Elements in the 3' UTRs of Neurofilament Genes Trigger Axonal Neuropathy.

Am J Hum Genet 2016 Apr 31;98(4):597-614. Epub 2016 Mar 31.

Dr. John T. Macdonald Department of Human Genetics and John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA. Electronic address:

Abnormal protein aggregation is observed in an expanding number of neurodegenerative diseases. Here, we describe a mechanism for intracellular toxic protein aggregation induced by an unusual mutation event in families affected by axonal neuropathy. These families carry distinct frameshift variants in NEFH (neurofilament heavy), leading to a loss of the terminating codon and translation of the 3' UTR into an extra 40 amino acids. In silico aggregation prediction suggested the terminal 20 residues of the altered NEFH to be amyloidogenic, which we confirmed experimentally by serial deletion analysis. The presence of this amyloidogenic motif fused to NEFH caused prominent and toxic protein aggregates in transfected cells and disrupted motor neurons in zebrafish. We identified a similar aggregation-inducing mechanism in NEFL (neurofilament light) and FUS (fused in sarcoma), in which mutations are known to cause aggregation in Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis, respectively. In summary, we present a protein-aggregation-triggering mechanism that should be taken into consideration during the evaluation of stop-loss variants.
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http://dx.doi.org/10.1016/j.ajhg.2016.02.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4833435PMC
April 2016

MORC2 mutations cause axonal Charcot-Marie-Tooth disease with pyramidal signs.

Ann Neurol 2016 Mar 13;79(3):419-27. Epub 2016 Jan 13.

Northcott Neuroscience Laboratory, ANZAC Research Institute, Concord, NSW, Australia.

Objective: To use linkage analysis and whole exome sequencing to identify the genetic mutation in a multigenerational Australian family with Charcot-Marie-Tooth disease type 2 (CMT2) and pyramidal signs.

Methods: Genome-wide linkage analysis was performed to map the locus. Whole exome sequencing was undertaken on selected individuals (3 affected, 1 normal), and segregation analysis and mutation screening were carried out using high-resolution melt analysis. The GEM.app database was queried to identify additional families with mutations.

Results: Significant linkage (2-point LOD score ≥ +3) and haplotype analysis mapped a new locus for CMT2 and pyramidal signs to a 6.6Mb interval on chromosome 22q12.1-q12.3. Whole exome sequencing identified a novel mutation (p.R252W) in the microrchidia CW-type zinc finger 2 (MORC2) gene mapping within the linkage region. The mutation fully segregated with the disease phenotype in the family. Screening additional families and querying unsolved CMT2 exomes, we identified the p.R252W mutation in 2 unrelated early onset CMT2 families and a second mutation p.E236G in 2 unrelated CMT2 families. Both the mutations occurred at highly conserved amino acid residues and were absent in the normal population.

Interpretation: We have identified a new locus in which MORC2 mutations are the likely pathogenic cause of CMT2 and pyramidal signs in these families. MORC2 encodes the human CW-type zinc finger 2 protein, which is a chromatin modifier involved in the regulation of DNA repair as well as gene transcription.
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http://dx.doi.org/10.1002/ana.24575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4936275PMC
March 2016

Mutation screen reveals novel variants and expands the phenotypes associated with DYNC1H1.

J Neurol 2015 Sep 24;262(9):2124-34. Epub 2015 Jun 24.

Department of Orthopaedics, Medical University Vienna, Währingergürtel 18-20, 1090, Vienna, Austria.

Dynein, cytoplasmic 1, heavy chain 1 (DYNC1H1) encodes a necessary subunit of the cytoplasmic dynein complex, which traffics cargo along microtubules. Dominant DYNC1H1 mutations are implicated in neural diseases, including spinal muscular atrophy with lower extremity dominance (SMA-LED), intellectual disability with neuronal migration defects, malformations of cortical development, and Charcot-Marie-Tooth disease, type 2O. We hypothesized that additional variants could be found in these and novel motoneuron and related diseases. Therefore, we analyzed our database of 1024 whole exome sequencing samples of motoneuron and related diseases for novel single nucleotide variations. We filtered these results for significant variants, which were further screened using segregation analysis in available family members. Analysis revealed six novel, rare, and highly conserved variants. Three of these are likely pathogenic and encompass a broad phenotypic spectrum with distinct disease clusters. Our findings suggest that DYNC1H1 variants can cause not only lower, but also upper motor neuron disease. It thus adds DYNC1H1 to the growing list of spastic paraplegia related genes in microtubule-dependent motor protein pathways.
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http://dx.doi.org/10.1007/s00415-015-7727-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4573829PMC
September 2015

Reply: The p.Ser107Leu in BICD2 is a mutation 'hot spot' causing distal spinal muscular atrophy.

Brain 2015 Nov 10;138(Pt 11):e392. Epub 2015 Jun 10.

2 Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, New South Wales, 2145, Australia 3 Discipline of Paediatrics and Child Health, Faculty of Medicine, The University of Sydney, Sydney, New South Wales, 2006, Australia 24 Murdoch Children's Research Institute. The Royal Children's Hospital. Parkville Victoria 3052 Australia 25 Department of Paediatrics, University of Melbourne Parkville Victoria 3010 Australia.

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http://dx.doi.org/10.1093/brain/awv160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4719680PMC
November 2015

Transcriptional regulator PRDM12 is essential for human pain perception.

Nat Genet 2015 Jul 25;47(7):803-8. Epub 2015 May 25.

1] Department of Medical Genetics, University of Cambridge, Cambridge, UK. [2] Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.

Pain perception has evolved as a warning mechanism to alert organisms to tissue damage and dangerous environments. In humans, however, undesirable, excessive or chronic pain is a common and major societal burden for which available medical treatments are currently suboptimal. New therapeutic options have recently been derived from studies of individuals with congenital insensitivity to pain (CIP). Here we identified 10 different homozygous mutations in PRDM12 (encoding PRDI-BF1 and RIZ homology domain-containing protein 12) in subjects with CIP from 11 families. Prdm proteins are a family of epigenetic regulators that control neural specification and neurogenesis. We determined that Prdm12 is expressed in nociceptors and their progenitors and participates in the development of sensory neurons in Xenopus embryos. Moreover, CIP-associated mutants abrogate the histone-modifying potential associated with wild-type Prdm12. Prdm12 emerges as a key factor in the orchestration of sensory neurogenesis and may hold promise as a target for new pain therapeutics.
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http://dx.doi.org/10.1038/ng.3308DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212047PMC
July 2015

Inverted formin 2-related Charcot-Marie-Tooth disease: extension of the mutational spectrum and pathological findings in Schwann cells and axons.

J Peripher Nerv Syst 2015 Mar;20(1):52-9

Friedrich-Baur Institute, Department of Neurology, Ludwig-Maximilians University Munich, Munich, Germany.

Mutations in the gene encoding inverted formin FH2 and WH2 domain-containing protein (INF2), a Cdc42 effector involved in the regulation of actin dynamics, cause focal segmental glomerulosclerosis (FSGS) and intermediate Charcot-Marie-Tooth neuropathy combined with FSGS (FSGS-CMT). Here, we report on six patients from four families with sensorimotor polyneuropathy and FSGS. Nerve conduction velocities were moderately slowed, and amplitudes of sensory and motor potentials were decreased. One patient had internal hydrocephalus and was intellectually disabled. Molecular genetic testing revealed two known and two novel missense mutations in the second and fourth exons of the INF2 gene. Investigations of one nerve biopsy confirmed the diagnosis of intermediate-type CMT and revealed occasional abnormal in- and outfoldings of myelin sheaths and expansions of the endoplasmic reticulum in axons and Schwann cells. While earlier reports suggested that mutations causing FSGS-CMT are restricted to exons 2 and 3 of the INF2 gene, we found one CMT-FSGS causing mutation (p.Glu184Lys) in exon 4 extending the critical region of INF2 for rapid CMT-FSGS molecular genetic diagnosis. Study of a nerve biopsy showed abnormalities that might be related to the known role of the INF2-binding partner CDC42 in myelination.
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http://dx.doi.org/10.1111/jns.12106DOI Listing
March 2015

Phenotypic and molecular insights into spinal muscular atrophy due to mutations in BICD2.

Brain 2015 Feb 14;138(Pt 2):293-310. Epub 2014 Dec 14.

2 Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, New South Wales, 2145, Australia 3 Discipline of Paediatrics and Child Health, Faculty of Medicine, The University of Sydney, Sydney, New South Wales, 2006, Australia 24 Murdoch Children's Research Institute. The Royal Children's Hospital, Parkville Victoria 3052 Australia 25 Department of Paediatrics, University of Melbourne Parkville Victoria 3010 Australia.

Spinal muscular atrophy is a disorder of lower motor neurons, most commonly caused by recessive mutations in SMN1 on chromosome 5q. Cases without SMN1 mutations are subclassified according to phenotype. Spinal muscular atrophy, lower extremity-predominant, is characterized by lower limb muscle weakness and wasting, associated with reduced numbers of lumbar motor neurons and is caused by mutations in DYNC1H1, which encodes a microtubule motor protein in the dynein-dynactin complex and one of its cargo adaptors, BICD2. We have now identified 32 patients with BICD2 mutations from nine different families, providing detailed insights into the clinical phenotype and natural history of BICD2 disease. BICD2 spinal muscular atrophy, lower extremity predominant most commonly presents with delayed motor milestones and ankle contractures. Additional features at presentation include arthrogryposis and congenital dislocation of the hips. In all affected individuals, weakness and wasting is lower-limb predominant, and typically involves both proximal and distal muscle groups. There is no evidence of sensory nerve involvement. Upper motor neuron signs are a prominent feature in a subset of individuals, including one family with exclusively adult-onset upper motor neuron features, consistent with a diagnosis of hereditary spastic paraplegia. In all cohort members, lower motor neuron features were static or only slowly progressive, and the majority remained ambulant throughout life. Muscle MRI in six individuals showed a common pattern of muscle involvement with fat deposition in most thigh muscles, but sparing of the adductors and semitendinosus. Muscle pathology findings were highly variable and included pseudomyopathic features, neuropathic features, and minimal change. The six causative mutations, including one not previously reported, result in amino acid changes within all three coiled-coil domains of the BICD2 protein, and include a possible 'hot spot' mutation, p.Ser107Leu present in four families. We used the recently solved crystal structure of a highly conserved region of the Drosophila orthologue of BICD2 to further-explore how the p.Glu774Gly substitution inhibits the binding of BICD2 to Rab6. Overall, the features of BICD2 spinal muscular atrophy, lower extremity predominant are consistent with a pathological process that preferentially affects lumbar lower motor neurons, with or without additional upper motor neuron involvement. Defining the phenotypic features in this, the largest BICD2 disease cohort reported to date, will facilitate focused genetic testing and filtering of next generation sequencing-derived variants in cases with similar features.
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http://dx.doi.org/10.1093/brain/awu356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4306822PMC
February 2015

HSJ1-related hereditary neuropathies: novel mutations and extended clinical spectrum.

Neurology 2014 Nov 1;83(19):1726-32. Epub 2014 Oct 1.

From the Department of Sleep Medicine and Neuromuscular Disorders (B.G., A.S., D.R., H.H., P.Y.), University of Muenster, Germany; Department of Orthopaedics (M.A.-G.), Medical University Vienna, Austria; Institute of Human Genetics (T.S.), Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg; Friedrich Baur Institute (M.Z., J.S.), Department of Neurology, Ludwig Maximilians University Munich; and Institute of Human Genetics (S.R.-S.), RWTH Aachen University, Germany.

Objectives: To determine the nature and frequency of HSJ1 mutations in patients with hereditary motor and hereditary motor and sensory neuropathies.

Methods: Patients were screened for mutations by genome-wide or targeted linkage and homozygosity studies, whole-exome sequencing, and Sanger sequencing. RNA and protein studies of skin fibroblasts were used for functional characterization.

Results: We describe 2 additional mutations in the HSJ1 gene in a cohort of 90 patients with autosomal recessive distal hereditary motor neuropathy (dHMN) and Charcot-Marie-Tooth disease type 2 (CMT2). One family with a dHMN phenotype showed the homozygous splice-site mutation c.229+1G>A, which leads to retention of intron 4 in the HSJ1 messenger RNA with a premature stop codon and loss of protein expression. Another family, presenting with a CMT2 phenotype, carried the homozygous missense mutation c.14A>G (p.Tyr5Cys). This mutation was classified as likely disease-related by several automatic algorithms for prediction of possible impact of an amino acid substitution on the structure and function of proteins. Both mutations cosegregated with autosomal recessive inheritance of the disease and were absent from the general population.

Conclusions: Taken together, in our cohort of 90 probands, we confirm that HSJ1 mutations are a rare but detectable cause of autosomal recessive dHMN and CMT2. We provide clinical and functional information on an HSJ1 splice-site mutation and report the detailed phenotype of 2 patients with CMT2, broadening the phenotypic spectrum of HSJ1-related neuropathies.
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http://dx.doi.org/10.1212/WNL.0000000000000966DOI Listing
November 2014

Extended phenotypic spectrum of KIF5A mutations: From spastic paraplegia to axonal neuropathy.

Neurology 2014 Aug 9;83(7):612-9. Epub 2014 Jul 9.

From the MRC Centre for Neuromuscular Diseases (Y.-T.L., M.L., A.H., M.M.R., H.H.) and Departments of Molecular Neuroscience (Y.-T.L., J.H., A.H., A.P., D.H., M.M.R., H.H.) and Clinical Neuroscience (C.P.), UCL Institute of Neurology; National Hospital for Neurology and Neurosurgery and UCLH (M.L., J.H., A.H., K.G.S., M.M.R., H.H.), London, UK; Section of Epilepsy (Y.-T.L.), Department of Neurology, Neurological Institute, Taipei Veterans General Hospital; National Yang-Ming University School of Medicine (Y.-T.L.), Taipei, Taiwan; Division of Neuropathology (Z.J., S.B.) and Neurogenetics Unit (J.M.P, M.G.S.), National Hospital for Neurology and Neurosurgery; Department of Neurology (J.C.J.), Chelsea and Westminster Hospital, London, UK; Department of Orthopaedics (M.A.-G.), Medical University Vienna, Austria; and Dr. John T. MacDonald Department of Human Genetics and Hussman Institute for Human Genomics (S.Z.), Miller School of Medicine, University of Miami, FL.

Objective: To establish the phenotypic spectrum of KIF5A mutations and to investigate whether KIF5A mutations cause axonal neuropathy associated with hereditary spastic paraplegia (HSP) or typical Charcot-Marie-Tooth disease type 2 (CMT2).

Methods: KIF5A sequencing of the motor-domain coding exons was performed in 186 patients with the clinical diagnosis of HSP and in 215 patients with typical CMT2. Another 66 patients with HSP or CMT2 with pyramidal signs were sequenced for all exons of KIF5A by targeted resequencing. One additional patient was genetically diagnosed by whole-exome sequencing.

Results: Five KIF5A mutations were identified in 6 unrelated patients: R204W and D232N were novel mutations; R204Q, R280C, and R280H have been previously reported. Three patients had CMT2 as the predominant and presenting phenotype; 2 of them also had pyramidal signs. The other 3 patients presented with HSP but also had significant axonal neuropathy or other additional features.

Conclusion: This is currently the largest study investigating KIF5A mutations. By combining next-generation sequencing and conventional sequencing, we confirm that KIF5A mutations can cause variable phenotypes ranging from HSP to CMT2. The identification of mutations in CMT2 broadens the phenotypic spectrum and underlines the importance of KIF5A mutations, which involve degeneration of both the central and peripheral nervous systems and should be tested in HSP and CMT2.
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http://dx.doi.org/10.1212/WNL.0000000000000691DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4141994PMC
August 2014

A novel missense mutation confirms ATL3 as a gene for hereditary sensory neuropathy type 1.

Brain 2014 Jul 15;137(Pt 7):e286. Epub 2014 Apr 15.

3 Department of Orthopaedics, Medical University Vienna, 1090 Vienna, Austria

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http://dx.doi.org/10.1093/brain/awu091DOI Listing
July 2014

Whole-exome sequencing in patients with inherited neuropathies: outcome and challenges.

J Neurol 2014 May 15;261(5):970-82. Epub 2014 Mar 15.

Department of Orthopaedics, Medical University Vienna, Währingergürtel 18-20, 1090, Vienna, Austria.

Inherited peripheral neuropathies (IPN) are one of the most frequent inherited causes of neurological disability characterized by considerable phenotypic and genetic heterogeneity. Based on clinical and electrophysiological properties, they can be subdivided into three main groups: HMSN, dHMN, and HSN. At present, more than 50 IPN genes have been identified. Still, many patients and families with IPN have not yet received a molecular genetic diagnosis because clinical genetic testing usually only covers a subset of IPN genes. Moreover, a considerable proportion of IPN genes has to be identified. Here we present results of WES in 27 IPN patients excluded for mutations in many known IPN genes. Eight of the patients received a definite diagnosis. While six of these patients carried bona fide pathogenic mutations in known IPN genes, two patients had mutations in genes known to be involved in other types of neuromuscular disorders. A further group of eight patients carried sequence variations in IPN genes that could not unequivocally be classified as pathogenic. In addition, combining data of WES and linkage analysis identified SH3BP4, ITPR3, and KLHL13 as novel IPN candidate genes. Moreover, there was evidence that particular mutations in PEX12, a gene known to cause Zellweger syndrome, could also lead to an IPN phenotype. We show that WES is a useful tool for diagnosing IPN and we suggest an expanded phenotypic spectrum of some genes involved in other neuromuscular and neurodegenerative disorders. Nevertheless, interpretation of variants in known and potential novel disease genes has remained challenging.
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http://dx.doi.org/10.1007/s00415-014-7289-8DOI Listing
May 2014