Abstract: Facioscapulohumeral muscular dystrophy is the most common inherited muscular dystrophy though no treatment exists. The lack of therapeutic development for FSHD is directly linked to insufficient understanding of how the disease is caused. The goals of the studies presented here were to gain a better understanding of the pathogenic mechanisms of FSHD and to develop targeted translational therapies to treat the disease. FSHD is associated with D4Z4 repeat contraction on human chromosome 4q35, which does not result in complete loss or mutation of any gene. Consequently, the major obstacle to discerning the underlying pathogenic mechanism is to identify the cause. Although no gene was conclusively linked to FSHD development, evidence supported a role for the D4Z4-encoded DUX4 gene. In Chapter 3, our objective was to test the in vivo myopathic potential of DUX4. We delivered DUX4 to zebrafish and mouse muscle by transposon-mediated transgenesis and adeno-associated viral vectors, respectively. We found over-expression of DUX4 caused abnormalities associated with muscular dystrophy in both animal models. This toxicity required DNA binding, since a DUX4 DNA binding domain mutant produced no abnormalities. We also found the toxic effects of DUX4 were p53-dependent. This study demonstrated the myopathic potential of DUX4 in animal muscle and provided a p53-dependent mechanism for DUX4-induced toxicity. Considering previous studies showed DUX4 was elevated in FSHD patient muscles, our data support the hypothesis that DUX4 over-expression contributes to FSHD development. With DUX4 as a potential target, gene silencing approaches could provide treatment for FSHD. With as many as 29 different gene mutations responsible for other dominant myopathies, gene silencing approaches could have a broad impact. Feasible mechanisms to silence dominant disease genes have lagged behind gene replacement strategies, but with the discovery of RNA interference (RNAi) and its subsequent development into a promising new gene silencing tool, the landscape has changed. In Chapter 4, our objective was to demonstrate proof-of-principle for RNAi therapy of a dominant myopathy in vivo. We tested the potential of AAV-delivered therapeutic microRNAs, targeting the human Facioscapulohumeral muscular dystrophy (FSHD) Region Gene 1 (FRG1), to correct myopathic features in mice expressing toxic levels of human FRG1 (FRG1-high mice). We found that FRG1 gene silencing improved muscle mass, strength, and histopathological abnormalities associated with muscular dystrophy in FRG1-high mice, thereby demonstrating therapeutic promise for treatment of FSHD and other dominantly inherited myopathies using RNAi. Next we applied this therapeutic strategy to FSHD by targeting DUX4. Several recent studies support an FSHD pathogenesis model involving over-expression of the myopathic DUX4 gene making it the most promising therapeutic target. In Chapter 5, we tested a pre-clinical RNAi-based DUX4 gene silencing approach as a prospective treatment for FSHD. We found that AAV vector-delivered therapeutic microRNAs corrected DUX4-associated myopathy in mouse muscle. These results provide proof-of-principle for RNAi therapy of FSHD through DUX4 inhibition. Together these studies have helped define the main pathogenic insult in FSHD and laid out a plausible, targeted therapy to treat the disease.
Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscular dystrophy characterized by progressive and asymmetric weakness of facial, shoulder and limb muscles. FSHD is linked to aberrant expression of the DUX4 gene, which encodes a myotoxic transcription factor. The emergence of DUX4 as a primary pathogenic insult in FSHD represented a momentum shift in the field, as it enabled translational research for the first time. There is currently no treatment for FSHD. Therapy development requires an understanding of the disease mechanism, as well as some knowledge about the normal function of the underlying genes involved. For these areas of research, animal models have proven to be essential tools. The goal of this work was to develop and characterize a viable animal model that recapitulated FSHD-like phenotypes. To achieve this, we have taken two approaches to create an FSHD animal model. The first approach was to define the extent of functional equivalency between the human DUX4 gene, which has close homologs only in primates, and a distantly related mouse gene, called Dux. This work supported that Dux and DUX4 both can cause myotoxicity and that Dux could therefore potentially be used as a proxy for human DUX4 in mouse studies designed to understand the normal and disease function of both genes. This work also demonstrated that there were key divergences in DUX4 and Dux protein homology and function that must be accounted for when studying Dux as a substitute for DUX4. In addition, DUX4, not Dux, is the main driver of FSHD in humans. Thus, DUX4 inhibition may be a direct path to FSHD therapy. Since DUX4 is extremely toxic, DUX4-expressing animal model development has been difficult, but progress has been made, revealing that tight regulation of DUX4 expression is critical for creating a viable model that develops myopathic features that are useful as therapeutic outcome measures. Our second approach for creating an FSHD animal model was to develop a DUX4 transgenic model with tight control of DUX4 expression. Here we report an inducible FSHD mouse model – called TIC-DUX4 - that utilizes Tamoxifen (TAM)-Inducible CRE recombinase to turn on DUX4 in skeletal muscle. Uninduced TIC-DUX4 (i.e. DUX4-off) mice are born in Mendelian ratios, develop normally to adulthood, and are indistinguishable from wild-type animals. Induced animals display significantly reduced skeletal muscle force, impaired open field activity, muscle wasting, and histological indicators of muscular dystrophy, including increased central nuclei and inflammation. Importantly, these phenotypes are tunable; myopathy progresses slowly over many months at low doses of TAM, while high doses can be used to rapidly induce widespread myopathic phenotypes within 2 weeks. We are now using this model to test DUX4-targeted gene therapies and myostatin inhibition to prevent DUX4 induced muscle weakness and increase muscle strength respectively. To directly target DUX4 expression, we utilized the RNAi pathway by AAV delivery of a DUX4-targeted microRNA. This provided long-term protection from DUX4-associated damage in old induced TIC-DUX4 mice. We also tested AAV delivery of follistatin by directly injecting virus into tibialis anterior and gastroc muscles of TIC-DUX4 mice. Follistatin expression significantly increased muscle mass and total muscle strength in the presence of DUX4 expression after 8 weeks of induction. These data will support translation of gene therapies for FSHD, and the TIC-DUX4 mouse model will be useful for testing other FSHD therapies as they emerge.
There are 8 different known types of this disorder, and some Muscular Dystrophy can actually be discovered during pregnancy, according to HRF. This guidebook provides essential information on MD, but also serves as a historical survey, by providing information on the controversies surrounding its causes, and first-person narratives by people coping with MD. Patients, family members, or caregivers explain the condition from their own experience. The symptoms, causes, and treatments are explained in detail. Essential to anyone trying to learn about diseases and conditions, the alternative treatments are explored. Each essay is carefully edited and presented with an introduction, so that they are accessible for student researchers and readers.
Muscular Dystrophy: New Insights for the Healthcare Professional: 2013 Edition is a ScholarlyBrief™ that delivers timely, authoritative, comprehensive, and specialized information about Additional Research in a concise format. The editors have built Muscular Dystrophy: New Insights for the Healthcare Professional: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Additional Research in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Muscular Dystrophy: New Insights for the Healthcare Professional: 2013 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
About 7 million people worldwide are suffering from various inherited neuromuscular diseases. Gene therapy brings the hope of treating these diseases at their genetic roots. Muscle Gene Therapy is the only book dedicated to this topic. The first edition was published in 2010 when the field was just about to enter its prime time. The progress made since then has been unprecedented. The number of diseases that have been targeted by gene therapy has increased tremendously. The gene therapy toolbox is expanded greatly with many creative novel strategies (such as genome editing and therapy with disease-modifying genes). Most importantly, clinical benefits have begun to emerge in human patients. To reflect rapid advances in the field, we have compiled the second edition of Muscle Gene Therapy with contributions from experts that have conducted gene therapy studies either in animal models and/or in human patients. The new edition offers a much needed, up-to-date overview and perspective on the foundation and current status of neuromuscular disease gene therapy. It provides a framework to the development and regulatory approval of muscle gene therapy drugs in the upcoming years. This book is a must-have for anyone who is interested in neuromuscular disease gene therapy including those in the research arena (established investigators and trainees in the fields of clinical practice, veterinary medicine and basic biomedical sciences), funding and regulatory agencies, and patient community.
The muscular dystrophies are a group of genetic diseases that severely affect children and adults. For sufferers and their family, the illness presents enormous physical and psychological challenges. This new edition answers many of the questions asked about how and why it occurs, and how it affects the life of a recently diagnosed child.
Publisher: Karger Medical and Scientific Publishers
This book reviews the electrophysiological, genetic and immunological bases of some of the major neuromuscular diseases and evaluates their importance pertaining to the clinical management of the patients. Included are up-to-date topics such as gene therapy, myoblast transfer and new drug trials. Written by experts in their own fields, this volume will not only be of great value to neurologists and neuroscientists, but also to geneticists, immunologists and physiologists.
Muscular Dystrophy - Research Update and Therapeutic Strategies is for students, researchers, and clinicians interested in muscular dystrophies who want to improve their knowledge of these complex genetic diseases. The book includes information about the genetics of various types of muscular dystrophies as well as explores new and current therapeutic strategies that aim to ameliorate symptoms and improve patients’ quality of life and life expectancy. In addition, this book reviews information on current clinical trials for muscular dystrophies and presents a framework for what to consider during the design of these trials.
Facioscapulohumeral muscular dystrophy (FSHD) is a genetic disorder involving slowly progressive muscle degeneration in which the muscles of the face, shoulder blades and upper arms are among the most severely affected. It is the third most common inherited muscular dystrophy, affecting 1 in 20,000. The search for the molecular basis of the disease is of interest to all genetic researchers, involving a deletion outside a coding region resulting in over-expression of adjacent genes. This volume summarizes the current understanding of the disorder, including clinical, molecular and therapeutic aspects.
This issue of Neurologic Clinics, guest edited by Dr. José Biller, is devoted to Therapy in Neurology. This issue is one of four selected each year by the series Consulting Editor, Dr. Randolph W. Evan. Articles in this issue include: Update on CGRP Antagonism in the Treatment of Migraine, Advances in the Treatment of Multiple Sclerosis, Advances in the Treatment of Neuromyelitis Optica Spectrum Disorder, Advances and ongoing controversies in PFO closure and cryptogenic stroke, Advances in neuromodulation/neurostimulation in Neurology, Advances in the treatment of muscular dystrophies and motor neuron disorders, Advances in the management of small fiber neuropathies, Update in the treatment of Idiopathic Intracranial Hypertension, What is new in neuro-oncology?, Advances in the surgical management of epilepsy, Treatment of Viral Encephalitis, An update on Botulinum toxin in neurology, Cannabinoids in neurological illnesses, and Pitfalls in Transitioning Neurological Care of the Developmentally Disabled from Pediatric to Adult Providers.