Hereditary myopathy with early respiratory failure (HMERF) : Still rare but common enough

Phenotypic and genetic/allelic heterogeneity is a feature of many neuromuscular disorders, titinopathies being one of them. Hereditary Myopathy with Early Respiratory Failure (HMERF) has been considered an extremely rare disease with definite clinicopathologic hallmarks, and geographically restricted to the Northern European population with one single titin gene defect identified in previous years. The recent availability of massive parallel sequencing techniques, allowing the screening of all coding regions of the genome in undiagnosed patients, together with a growing awareness of the main muscle MRI features of the disease, has led to the discovery of a number of HMERF families and new titin mutations in the last five years. We reviewed the clinical, pathological and muscle imaging findings that are still cornerstones for the diagnosis of this disease, as well as the most recent molecular genetic findings. HMERF is more common and geographically widespread than previously expected, and the knowledge of the whole phenotypic and molecular spectrum of HMERF can increase the number of diagnosed patients considerably. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

Panorama of the distal myopathies

Distal myopathies are genetic primary muscle disorders with a prominent weakness at onset in hands and/or feet. The age of onset (from early childhood to adulthood), the distribution of muscle weakness (upper versus lower limbs) and the histological findings (ranging from nonspecific myopathic changes to myofibrillar disarrays and rimmed vacuoles) are extremely variable. However, despite being characterized by a wide clinical and genetic heterogeneity, the distal myopathies are a category of muscular dystrophies: genetic diseases with progressive loss of muscle fibers. Myopathic congenital arthrogryposis is also a form of distal myopathy usually caused by focal amyoplasia. Massive parallel sequencing has further expanded the long list of genes associated with a distal myopathy, and contributed identifying as distal myopathy-causative rare variants in genes more often related with other skeletal or cardiac muscle diseases. Currently, almost 20 genes (ACTN2, CAV3, CRYAB, DNAJB6, DNM2, FLNC, HNRNPA1, HSPB8, KHLH9, LDB3, MATR3, MB, MYOT, PLIN4, TIA1, VCP, NOTCH2NLC, LRP12, GIPS1) have been associated with an autosomal dominant form of distal myopathy. Pathogenic changes in four genes (ADSSL, ANO5, DYSF, GNE) cause an autosomal recessive form; and disease-causing variants in five genes (DES, MYH7, NEB, RYR1 and TTN) result either in a dominant or in a recessive distal myopathy. Finally, a digenic mechanism, underlying a Welander-like form of distal myopathy, has been recently elucidated. Rare pathogenic mutations in SQSTM1, previously identified with a bone disease (Paget disease), unexpectedly cause a distal myopathy when combined with a common polymorphism in TIA1. The present review aims at describing the genetic basis of distal myopathy and at summarizing the clinical features of the different forms described so far. ©2020 Gaetano Conte Academy - Mediterranean Society of Myology, Naples, Italy.Peer reviewe

Kaitsijamutaatiot neuromuskulaaritaudeissa

Vertaisarvioitu.Kaitsijaproteiinien eli kaperonien ja kokaperonien geenivirheet aiheuttavat neuromuskulaaritauteja vaihtelevilla mekanismeilla. Peittyvästi periytyvät taudit liittyvät tyypillisesti kaitsijaproteiinin toiminnan puutokseen, kun taas vallitsevasti periytyvien taustalla voi olla kaitsijaproteiinikoneiston häiriintyminen (esimerkiksi DNAJB6- ja BAG3-geenivirheet) tai muut solumyrkylliset vaikutukset (sHSP-geenivirheet). Tautimekanismien selviäminen on viime vuosina avannut mahdollisuuksia myös tämän kasvavan tautiryhmän hoitoyrityksille.Peer reviewe

Borderlines between sarcopenia and mild late-onset muscle disease

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Use of animal models to understand titin physiology and pathology

In recent years, increasing attention has been paid to titin (TTN) and its mutations. Heterozygous TTN truncating variants (TTNtv) increase the risk of a cardiomyopathy. At the same time, TTNtv and few missense variants have been identified in patients with mainly recessive skeletal muscle diseases. The pathogenic mechanisms underlying titin-related diseases are still partly unknown. Similarly, the titin mechanical and functional role in the muscle contraction are far from being exhaustively clarified. In the last few years, several animal models carrying variants in the titin gene have been developed and characterized to study the structural and mechanical properties of specific titin domains or to mimic patients' mutations. This review describes the main animal models so far characterized, including eight mice models and three fish models (Medaka and Zebrafish) and discusses the useful insights provided by a thorough characterization of the cell-, tissue- and organism-phenotypes in these models.Peer reviewe

Statiineihin liittyvät itsepintaiset lihasoireet

Pääkirjoitus-editoria

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results

Skeletal muscle and the nervous system depend on efficient protein quality control, and they express chaperones and cochaperones at high levels to maintain protein homeostasis. Mutations in many of these proteins cause neuromuscular diseases, myopathies, and hereditary motor and sensorimotor neuropathies. In this review, we cover mutations in DNAJB6, DNAJB2, αB-crystallin (CRYAB, HSPB5), HSPB1, HSPB3, HSPB8, and BAG3, and discuss the molecular mechanisms by which they cause neuromuscular disease. In addition, previously unpublished results are presented, showing downstream effects of BAG3 p.P209L on DNAJB6 turnover and localization

Increasing Role of Titin Mutations in Neuromuscular Disorders

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Is Gene-Size an Issue for the Diagnosis of Skeletal Muscle Disorders?

Human genes have a variable length. Those having a coding sequence of extraordinary length and a high number of exons were almost impossible to sequence using the traditional Sanger-based gene-by-gene approach. High-throughput sequencing has partly overcome the size-related technical issues, enabling a straightforward, rapid and relatively inexpensive analysis of large genes. Several large genes (e.g. TTN, NEB, RYR1, DMD) are recognized as disease-causing in patients with skeletal muscle diseases. However, because of their sheer size, the clinical interpretation of variants in these genes is probably the most challenging aspect of the high-throughput genetic investigation in the field of skeletal muscle diseases. The main aim of this review is to discuss the technical and interpretative issues related to the diagnostic investigation of large genes and to reflect upon the current state of the art and the future advancements in the field. © 2020 - IOS Press and the authors. All rights reserved.Peer reviewe