Udd b , c , d , on behalf of the LGMD workshop study group

ObjectiveLimb‐girdle muscular dystrophies (LGMDs), one of the most heterogeneous neuromuscular disorders (NMDs), involves predominantly proximal‐muscle weakness with >30 genes associated with different subtypes. The clinical‐genetic overlap among subtypes and with other NMDs complicate disease‐subtype identification lengthening diagnostic process, increases overall costs hindering treatment/clinical‐trial recruitment. Currently seven LGMD clinical trials are active but still no gene‐therapy‐related treatment is available. Till‐date no nation‐wide large‐scale LGMD sequencing program was performed. Our objectives were to understand LGMD genetic basis, different subtypes’ relative prevalence across US and investigate underlying disease mechanisms.MethodsA total of 4656 patients with clinically suspected‐LGMD across US were recruited to conduct next‐generation sequencing (NGS)‐based gene‐panel testing during June‐2015 to June‐2017 in CLIA‐CAP‐certified Emory‐Genetics‐Laboratory. Thirty‐five LGMD‐subtypes‐associated or LGMD‐like other NMD‐associated genes were investigated. Main outcomes were diagnostic yield, gene‐variant spectrum, and LGMD subtypes’ prevalence in a large US LGMD‐suspected population.ResultsMolecular diagnosis was established in 27% (1259 cases; 95% CI, 26–29%) of the patients with major contributing genes to LGMD phenotypes being: CAPN3(17%), DYSF(16%), FKRP(9%) and ANO5(7%). We observed an increased prevalence of genetically confirmed late‐onset Pompe disease, DNAJB6‐associated LGMD subtype1E and CAPN3‐associated autosomal‐dominant LGMDs. Interestingly, we identified a high prevalence of patients with pathogenic variants in more than one LGMD gene suggesting possible synergistic heterozygosity/digenic/multigenic contribution to disease presentation/progression that needs consideration as a part of diagnostic modality.InterpretationOverall, this study has improved our understanding of the relative prevalence of different LGMD subtypes, their respective genetic etiology, and the changing paradigm of their inheritance modes and novel mechanisms that will allow for improved timely treatment, management, and enrolment of molecularly diagnosed individuals in clinical trials.

Objective:To describe the baseline clinical and functional characteristics of an international cohort of 193 patients with dysferlinopathy.Methods:The Clinical Outcome Study for dysferlinopathy (COS) is an international multicenter study of this disease, evaluating patients with genetically confirmed dysferlinopathy over 3 years. We present a cross-sectional analysis of 193 patients derived from their baseline clinical and functional assessments.Results:There is a high degree of variability in disease onset, pattern of weakness, and rate of progression. No factor, such as mutation class, protein expression, or age at onset, accounted for this variability. Among patients with clinical diagnoses of Miyoshi myopathy or limb-girdle muscular dystrophy, clinical presentation and examination was not strikingly different. Respiratory impairment and cardiac dysfunction were observed in a minority of patients. A substantial delay in diagnosis was previously common but has been steadily reducing, suggesting increasing awareness of dysferlinopathies.Conclusions:These findings highlight crucial issues to be addressed for both optimizing clinical care and planning therapeutic trials in dysferlinopathy. This ongoing longitudinal study will provide an opportunity to further understand patterns and variability in disease progression and form the basis for trial design.

Background and objectiveDysferlinopathies are a group of muscle disorders caused by mutations in the DYSF gene. Previous muscle imaging studies describe a selective pattern of muscle involvement in smaller patient cohorts, but a large imaging study across the entire spectrum of the dysferlinopathies had not been performed and previous imaging findings were not correlated with functional tests.MethodsWe present cross-sectional T1-weighted muscle MRI data from 182 patients with genetically confirmed dysferlinopathies. We have analysed the pattern of muscles involved in the disease using hierarchical analysis and presented it as heatmaps. Results of the MRI scans have been correlated with relevant functional tests for each region of the body analysed.ResultsIn 181 of the 182 patients scanned, we observed muscle pathology on T1-weighted images, with the gastrocnemius medialis and the soleus being the most commonly affected muscles. A similar pattern of involvement was identified in most patients regardless of their clinical presentation. Increased muscle pathology on MRI correlated positively with disease duration and functional impairment.ConclusionsThe information generated by this study is of high diagnostic value and important for clinical trial development. We have been able to describe a pattern that can be considered as characteristic of dysferlinopathy. We have defined the natural history of the disease from a radiological point of view. These results enabled the identification of the most relevant regions of interest for quantitative MRI in longitudinal studies, such as clinical trials.Clinical trial registrationNCT01676077.

Limb girdle muscular dystrophy type 2L or anoctaminopathy is a condition mainly characterized by adult onset proximal lower limb muscular weakness and raised CK values, due to recessive ANO5 gene mutations. An exon 5 founder mutation (c.191dupA) has been identified in most of the British and German LGMD2L patients so far reported. We aimed to further investigate the prevalence and spectrum of ANO5 gene mutations and related clinical phenotypes, by screening 205 undiagnosed patients referred to our molecular service with a clinical suspicion of anoctaminopathy. A total of 42 unrelated patients had two ANO5 mutations (21%), whereas 14 carried a single change. We identified 34 pathogenic changes, 15 of which are novel. The c.191dupA mutation represents 61% of mutated alleles and appears to be less prevalent in non-Northern European populations. Retrospective clinical analysis corroborates the prevalently proximal lower limb phenotype, the male predominance and absence of major cardiac or respiratory involvement. Identification of cases with isolated hyperCKaemia and very late symptomatic male and female subjects confirms the extension of the phenotypic spectrum of the disease. Anoctaminopathy appears to be one of the most common adult muscular dystrophies in Northern Europe, with a prevalence of about 20%-25% in unselected undiagnosed cases.

Hepatic lipase (HL) plays a key role in the metabolism of plasma lipoproteins, and its level of activity requires tight regulation, given the association of both low and high levels with atherosclerosis and coronary artery disease. However, little is known about the factors responsible for HL expression. Here, we report that the human hepatic lipase gene (LIPC) promoter is regulated by hepatocyte nuclear factor 4a (HNF4a), peroxisome proliferator-activated receptor g coactivator-1a (PGC-1a), apolipoprotein A-I regulatory protein-1 (ARP-1), and hepatocyte nuclear factor 1a (HNF1a). Reporter analysis showed that HNF4a directly regulates the LIPC promoter via two newly identified direct repeat elements, DR1 and DR4. PGC-1a is capable of stimulating the HNF4a-dependent transactivation of the LIPC promoter. ARP-1 displaces HNF4a from the DR1 site and blocks its ability to activate the LIPC promoter. Induction by HNF1a requires the HNF1 binding site and upon cotransfection with HNF4a leads to an additive effect. In addition, the in vivo relevance of HNF4a in LIPC expression is shown by the ability of the HNF4a antagonist Medica 16 to repress endogenous LIPC mRNA expression. Furthermore, disruption of Hnf4a in mice prevents the expression of HL mRNA in liver. The overall effect these transcription factors have on HL expression will ultimately depend on the interplay between these various factors and their relative intracellular concentrations.-Rufibach, L. E., S. A. Duncan, M. Battle, and S. S. Deeb. Hepatic lipase (HL) is a 477 amino acid glycoprotein that plays an important role in lipoprotein metabolism. The majority of HL is synthesized and secreted by the liver, where it has been shown to act as both a lipase and a ligand. As a lipase, it catalyzes the hydrolysis of triglycerides and phospholipids of intermediate density lipoprotein remnants, large buoyant LDLs, and HDLs to form smaller, denser lipoprotein particles (1, 2). Studies in humans have shown an association between high HL activity and increased plasma concentrations of small, dense LDL and HDL particles, one of the major risk factors for coronary artery disease (3-5). As a ligand, HL contributes to the process of reverse cholesterol transport by participating with surface proteoglycans and the low density lipoprotein receptor like-protein in promoting hepatic uptake of lipoproteins, including remnant LDL and HDL particles (6-8), thus mediating the hepatic uptake of HDL-cholesteryl esters (9). The observed association of low HL activity with coronary artery disease might be attributable to decreased HL-enhanced remnant uptake by the liver (10). Together, these data show that HL is an important enzyme in lipid metabolism that must be highly regulated, because both low and high levels of HL activity appear associated with dyslipidemia.The expression level of hepatic lipase activity varies widely in normal individuals (5-to 8-fold) and is influenced by genetic variation, obesity, gender, intracellular cholesterol, and lipid-lowering therapy (11). H...

Mutations in the dysferlin gene (DYSF) lead to a complete or partial absence of the dysferlin protein in skeletal muscles and are at the origin of dysferlinopathies, a heterogeneous group of rare autosomal recessive inherited neuromuscular disorders. As a step towards a better understanding of the DYSF mutational spectrum, and towards possible inclusion of patients in future therapeutic clinical trials, we set up the Universal Mutation Database for Dysferlin (UMD-DYSF), a Locus-Specific Database developed with the UMD® software. The main objective of UMD-DYSF is to provide an updated compilation of mutational data and relevant interactive tools for the analysis of DYSF sequence variants, for diagnostic and research purposes. In particular, specific algorithms can facilitate the interpretation of newly identified intronic, missense-or isosemantic-exonic sequence variants, a problem encountered recurrently during genetic diagnosis in dysferlinopathies. UMD-DYSF v1.0 is freely accessible at www.umd.be/DYSF/. It contains a total of 742 mutational entries corresponding to 266 different disease-causing mutations identified in 558 patients worldwide diagnosed with dysferlinopathy. This article presents for the first time a comprehensive analysis of the dysferlin mutational spectrum based on all compiled DYSF diseasecausing mutations reported in the literature to date, and using the main bioinformatics tools offered in UMD-DYSF.

Purpose: Limb Girdle Muscular Dystrophies (LGMD) are a genetically heterogeneous category of autosomal inherited muscle diseases. Many genes causing LGMD have been identified, and clinical trials are beginning for treatment of some genetic subtypes. However, even with the gene-level mechanisms known, it is still difficult to get a reliable and generalizable prevalence estimation for each subtype due to the limited amount of epidemiology data and the low incidence of LGMDs. Methods: Taking advantage of recently published whole exome and genome sequencing data from the general population, we used a Bayesian method to develop a reliable disease prevalence estimator. Results: This method was applied to nine recessive LGMD subtypes. The estimated disease prevalence calculated by this method were largely comparable to published estimates from epidemiological studies, however highlighted instances of possible under-diagnosis for LGMD2B and 2L. Conclusion: The increasing size of aggregated population variant databases will allow for robust and reproducible prevalence estimates of recessive disease, which is critical for the strategic design and prioritization of clinical trials..