Clemens Müller-Reible

Treatment of dysferlinopathy with deflazacort: a double-blind, placebo-controlled clinical trial

BackgroundDysferlinopathies are autosomal recessive disorders caused by mutations in the dysferlin (DYSF) gene encoding the dysferlin protein. DYSF mutations lead to a wide range of muscular phenotypes, with the most prominent being Miyoshi myopathy (MM) and limb girdle muscular dystrophy type 2B (LGMD2B).MethodsWe assessed the one-year-natural course of dysferlinopathy, and the safety and efficacy of deflazacort treatment in a double-blind, placebo-controlled cross-over trial. After one year of natural course without intervention, 25 patients with genetically defined dysferlinopathy were randomized to receive deflazacort and placebo for six months each (1xa0mg/kg/day in month one, 1xa0mg/kg every 2nd day during months two to six) in one of two treatment sequences.ResultsDuring one year of natural course, muscle strength declined about 2% as measured by CIDD (Clinical Investigation of Duchenne Dystrophy) score, and 76 Newton as measured by hand-held dynamometry. Deflazacort did not improve muscle strength. In contrast, there is a trend of worsening muscle strength under deflazacort treatment, which recovers after discontinuation of the study drug. During deflazacort treatment, patients showed a broad spectrum of steroid side effects.ConclusionDeflazacort is not an effective therapy for dysferlinopathies, and off-label use is not warranted. This is an important finding, since steroid treatment should not be administered in patients with dysferlinopathy, who may be often misdiagnosed as polymyositis.Trial registrationThis clinical trial was registered at http://www.ClincalTrials.gov, identifier: NCT00527228, and was always freely accessible to the public.

Facing the genetic heterogeneity in neuromuscular disorders: Linkage analysis as an economic diagnostic approach towards the molecular diagnosis

The identification of an ever increasing number of gene defects in patients with neuromuscular disorders has disclosed both marked phenotype and genotype variability and considerable disease overlap. In order to offer an economic strategy to characterise the molecular defect in patients with unclassified neuromuscular disorders, we designed DNA marker sets for linkage analysis of 62 distinct neuromuscular disorders gene loci, including all known muscular dystrophies, congenital myopathies, congenital myasthenic syndromes and myotonias. Genotyping of marker loci of 140 clinically well-characterised families with unclassified neuromuscular disorders reduced the number of candidates to one or two genes in 49 % of the families. Subsequent mutation analysis and genome-wide scans enabled the determination of the genetic defect in 31 % of the families including the identification of a new gene and a new mutation in an unexpected candidate gene. This highlights the effective application of this approach both for diagnostic strategies as well as for the identification of new loci and genes.

Novel RYR1 missense mutation causes core rod myopathy.

M. von der Hagen, W. Kress, G. Hahn, K. S. Brocke, P. Mitzscherling, A. Huebner, C. Müller-Reible, G. Stoltenburg-Didinger and A. M. Kaindl Department of Pediatric Neurology, Technical University, Dresden, Germany; Institute of Human Genetics, JuliusMaximilian University, Würzburg; Department of Radiology, Technical University, Dresden; Children s Hospital, Technical University, Dresden; Departments of Neuropathology; Pediatric Neurology, Charité, Berlin, Germany and Inserm U676-Paris 7, Paris, France

SLC2A3 single‐nucleotide polymorphism and duplication influence cognitive processing and population‐specific risk for attention‐deficit/hyperactivity disorder

BACKGROUNDnAttention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurodevelopmental disorder with profound cognitive, behavioral, and psychosocial impairments with persistence across the life cycle. Our initial genome-wide screening approach for copy number variants (CNVs) in ADHD implicated a duplication of SLC2A3, encoding glucose transporter-3 (GLUT3). GLUT3 plays a critical role in cerebral glucose metabolism, providing energy for the activity of neurons, which, in turn, moderates the excitatory-inhibitory balance impacting both brain development and activity-dependent neural plasticity. We therefore aimed to provide additional genetic and functional evidence for GLUT3 dysfunction in ADHD.nnnMETHODSnCase-control association analyses of SLC2A3 single-nucleotide polymorphisms (SNPs) and CNVs were conducted in several European cohorts of patients with childhood and adult ADHD (SNP, nxa0=xa01,886 vs. 1,988; CNV, nxa0=xa01,692 vs. 1,721). These studies were complemented by SLC2A3 expression analyses in peripheral cells, functional EEG recordings during neurocognitive tasks, and ratings of food energy content.nnnRESULTSnMeta-analysis of all cohorts detected an association of SNP rs12842 with ADHD. While CNV analysis detected a population-specific enrichment of SLC2A3 duplications only in German ADHD patients, the CNVxa0+xa0rs12842 haplotype influenced ADHD risk in both the German and Spanish cohorts. Duplication carriers displayed elevated SLC2A3 mRNA expression in peripheral blood cells and altered event-related potentials reflecting deficits in working memory and cognitive response control, both endophenotypic traits of ADHD, and an underestimation of energy units of high-caloric food.nnnCONCLUSIONSnTaken together, our results indicate that both common and rare SLC2A3 variation impacting regulation of neuronal glucose utilization and energy homeostasis may result in neurocognitive deficits known to contribute to ADHD risk.

Regional lactate and carbon dioxide concentrations in a metabolic test for malignant hyperthermia

control measurements of lactate did not increase after application of halothane or caffeine at a distant site in the same muscle. Similarly, carbon dioxide values did not rise when halothane was applied at a distant site in the same muscle. Further experiments in individuals susceptible to malignant hyperthermia have revealed that halothane applied via microdialysis increases lactate but not carbon dioxide concentrations (unpublished data). The highly diffusible carbon dioxide seems to be transported away by blood, whereas the polar lactate is locally retained in the muscle tissue. By contrast, in the published Research letter, caffeine was given as a bolus by injection and led to a timely defined increase of pCO2 in individuals susceptible to malignant hyperthermia. In conclusion, no data point towards an interference between different trigger agents in the presented study. Local lactate and carbon dioxide increase seems to be limited to an area less than 10 mm around the application site. Further experiments will be done to confirm these results. *Martin Anetseder, Martin Hager, Clemens Muller-Reible, Norbert Roewer

The Genetic Approach: Next-Generation Sequencing-Based Diagnosis of Congenital and Infantile Myopathies/Muscle Dystrophies

The practical basis for massive parallel sequencing is described to help clinicians in choosing the most adequate diagnostic approach for childhood myopathies. The key quality feature for massive parallel sequencing is the sequence depth (coverage) as a prerequisite for variant identification and quantification of sequence copy numbers. Our experience with a next-generation sequencing gene panel for the analysis of muscular dystrophies/myopathies with infantile or juvenile onset resulted in the identification of pathogenic or likely pathogenic mutations in approximately 41% (of 141 patients), thus leading to a definitive diagnosis. A subset of patients shows an accumulation of “excess” heterozygous variants that may act as modifiers of the phenotype. Massive parallel sequencing has become a reliable and cost-effective method, but it requires exact clinical, bioptic, and/or radiologic information to evaluate the clinical relevance of possibly pathologic variants.