ABSTRACT
Microsatellite expansions of CCTG repeats in the cellular nucleic acid-binding protein (CNBP) gene leads to accumulation of toxic RNA and have been associated with myotonic dystrophy type 2 (DM2). However, it is still unclear whether the dystrophic phenotype is also linked to CNBP decrease, a conserved CCHC-type zinc finger RNA-binding protein that regulates translation and is required for mammalian development. Here, we show that depletion of Drosophila CNBP in muscles causes ageing-dependent locomotor defects that are correlated with impaired polyamine metabolism. We demonstrate that the levels of ornithine decarboxylase (ODC) and polyamines are significantly reduced upon dCNBP depletion. Of note, we show a reduction of the CNBP-polyamine axis in muscles from DM2 patients. Mechanistically, we provide evidence that dCNBP controls polyamine metabolism through binding dOdc mRNA and regulating its translation. Remarkably, the locomotor defect of dCNBP-deficient flies is rescued by either polyamine supplementation or dOdc1 overexpression. We suggest that this dCNBP function is evolutionarily conserved in vertebrates with relevant implications for CNBP-related pathophysiological conditions.
Subject(s)
Drosophila Proteins/metabolism , Motor Activity/genetics , Motor Activity/physiology , Polyamines/metabolism , RNA-Binding Proteins/metabolism , Animals , Animals, Genetically Modified , Cell Line , Down-Regulation/physiology , Drosophila Proteins/genetics , Drosophila melanogaster , Gene Expression Regulation/drug effects , HEK293 Cells , Humans , Muscle, Skeletal/metabolism , Myotonic Dystrophy/genetics , Myotonic Dystrophy/metabolism , Protein Biosynthesis , Putrescine/pharmacology , RNA Interference , RNA-Binding Proteins/genetics , Spermidine/pharmacologyABSTRACT
GM2 gangliosidosis type Sandhoff is caused by a defect of beta-hexosaminidase, an enzyme involved in the catabolism of gangliosides. It has been proposed that substrate reduction therapy using N-butyl-deoxynojirimycin (miglustat) may delay neurological progression, at least in late-onset forms of GM2 gangliosidosis. We report the results of a 3-year treatment with miglustat (100 mg t.i.d) in a patient with chronic Sandhoff disease manifesting with an atypical, spinal muscular atrophy phenotype. The follow-up included serial neurological examinations, blood tests, abdominal ultrasound, and neurophysiologic, cognitive, brain, and muscle MRI studies. We document some minor effects on neurological progression in chronic Sandhoff disease by miglustat treatment, confirming the necessity of phase II therapeutic trials including early-stage patients in order to assess its putative efficacy in chronic Sandhoff disease.
Subject(s)
1-Deoxynojirimycin/analogs & derivatives , Enzyme Inhibitors/therapeutic use , Glucosyltransferases/antagonists & inhibitors , Sandhoff Disease/drug therapy , 1-Deoxynojirimycin/therapeutic use , Disease Progression , Glucosyltransferases/metabolism , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Muscle Weakness/diagnosis , Muscle Weakness/drug therapy , Muscle Weakness/etiology , Muscular Atrophy, Spinal/diagnosis , Muscular Atrophy, Spinal/drug therapy , Muscular Atrophy, Spinal/etiology , Neurologic Examination , Predictive Value of Tests , Sandhoff Disease/complications , Sandhoff Disease/diagnosis , Sandhoff Disease/enzymology , Sandhoff Disease/genetics , Time Factors , Treatment OutcomeABSTRACT
OBJECTIVE: Myotonic dystrophy type 1 (DM1) is the most frequent muscular dystrophy in adults. DM1 is a multisystem disorder also affecting the heart with an increased incidence of sudden death, which has been explained with the common impairment of the conduction system often requiring pacemaker implantation; however, the occurrence of sudden death despite pacemaker implantation and the observation of major ventricular arrhythmias generated the hypothesis that ventricular arrhythmias may play a causal role as well. The aim of the study was to assess the 2-year cumulative incidence and the value of noninvasive and invasive findings as predictive factors for sudden death, resuscitated cardiac arrest, ventricular fibrillation, sustained ventricular tachycardia and severe sinus dysfunction or high-degree atrioventricular block. METHODS/DESIGN: More than 500 DM1 patients will be evaluated at baseline with a clinical interview, 12-lead ECG, 24-h ECG and echocardiogram. Conventional and nonconventional indications to electrophysiological study, pacemaker, implantable cardioverter defibrillator or loop recorder implantation have been developed. In the case of an indication to electrophysiological study, pacemaker, implantable cardioverter defibrillator or loop recorder implant at baseline or at follow-up, the patient will be referred for the procedure. At the end of 2-year follow-up, all candidate prognostic factors will be tested for their association with the endpoints. TRIAL REGISTRATION: ClinicalTrials.gov ID NCT00127582. CONCLUSION: The available evidence supports the hypothesis that both bradyarrhythmias and tachyarrhythmias may cause sudden death in DM1, but the course of cardiac disease in DM1 is still unclear. We expect that this large, prospective, multicenter study will provide evidence to improve diagnostic and therapeutic strategies in DM1.