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Background and purpose: The aim was to determine the genetic background of unknown muscular dystrophy in five French families. Methods: Twelve patients with limb girdle muscular dystrophy or distal myopathy were clinically evaluated. Gene mutations were identified using targeted exon sequencing and mutated DNAJB6 was tested in vitro. Results: Five patients presented with distal lower limb weakness whilst others had proximal presentation with a variable rate of progression starting at the mean age of 38.5 years. Two novel mutations (c.284A>T, p.Asn95Ile, two families; and c.293_295delATG, p.Asp98del, one family) as well as the previously reported c.279C>G (p.Phe93Leu, two families) mutation in DNAJB6 were identified. All showed a reduced capacity to prevent protein aggregation. Conclusions: The mutational and phenotypical spectrum of DNAJB6-caused muscle disease is larger than previously reported, including also dysphagia. The originally reported c.279C>G (p.Phe93Leu) mutation is now identified in four different populations and appears to be a mutational hotspot. Our report confirms that some DNAJB6 mutations cause distal-onset myopathy and hence DNAJB6 defects should be considered broadly in dominant muscular dystrophy families. [ABSTRACT FROM AUTHOR]

utosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in LMNA gene encoding lamins A and C. The disease is characterized by early onset joint contractures during childhood associated with humero-peroneal muscular wasting and weakness, and by the development of a cardiac disease in adulthood. Important intra-familial variability characterized by a wide range of age at onset of myopathic symptoms (AOMS) has been recurrently reported, suggesting the contribution of a modifier gene. Our objective was to identify a modifier locus of AOMS in relation with the LMNA mutation. To map the modifier locus, we genotyped 291 microsatellite markers in 59 individuals of a large French family, where 19 patients carrying the same LMNA mutation, exhibited wide range of AOMS. We performed Bayesian Markov Chain Monte Carlo-based joint segregation and linkage methods implemented in the Loki software, and detected a strong linkage signal on chromosome 2 between markers D2S143 and D2S2244 (211 cM) with a Bayes factor of 28.7 (empirical p value = 0.0032). The linked region harbours two main candidate genes, DES and MYL1 encoding desmin and light chain of myosin. Importantly, the impact of the genotype on the phenotype for this locus showed an overdominant effect with AOMS 2 years earlier for the homozygotes of the rare allele and 37 years earlier for the heterozygotes than the homozygotes for the common allele. These results provide important highlights for the natural history and for the physiopathology of Emery-Dreifuss muscular dystrophy. [ABSTRACT FROM AUTHOR]

Background: Heart-hand syndromes are a heterogeneous group of genetic disorders characterised by the association of congenital cardiac disease and limb deformities. Laminopathies are a group of diseases caused by mutations in the LMNA gene encoding A-type lamins. Results: We report a new LMNA mutation (c.1609-12T>G, IVS9-12 T>G) that creates a new cryptic splicing site with the retention of 11 intronic nucleotides in the mRNA. This LMNA mutation segregates with a new type of heart-hand syndrome in a previously reported family suffering from adult onset progressive conduction system disease, atrial and ventricular tachyarrhythmias, sudden death, dilated cardiomyopathy, and brachydactyly with predominant foot involvement. Analysis of the fibroblasts of two affected family members identified for the first time a truncated lamin A/C protein resulting from the frame shift created by the new splicing site, together with nuclear envelope abnormalities confirming that this LMNA mutation is pathogenic. Conclusions: This new heart-hand syndrome should therefore be considered as a new kind of laminopathy. As part of laminopathies with heart involvement, patients presenting with this phenotype and their relatives are at risk for developing sudden cardiac death and should beneficiate from appropriate LMNA genetic diagnosis. [ABSTRACT FROM AUTHOR]

The article discusses the nuclear lamins and their role in premature ageing. The nucleus is the defining feature of eukaryotic cells and is separated by the nuclear envelope (NE) from the cytoplasm. NE is composed of the nuclear membrane, nuclear pore complexes, and the nuclear lamina. A-type lamins accelerate ageing by imposing a senescent program on dividing cells when presented in mutant forms.

Background: Skeletal muscle disorders associated with mutations of lamin A/C gene include autosomal Emery­Dreifuss muscular dystrophy and limb girdle muscular dystrophy 1B. The pathogenic mechanism underlying these diseases is unknown. Recent data suggest an impairment of signalling mechanisms as a possible cause of muscle malfunction. A molecular complex in muscle cells formed by lamin A/C, emerin, and nuclear actin has been identified. The stability of this protein complex appears to be related to phosphorylation mechanisms. Objective: To analyse lamin A/C phosphorylation in control and laminopathic muscle cells. Methods: Lamin A/C N-terminal phosphorylation was determined in cultured mouse myoblasts using a specific antibody. Insulin treatment of serum starved myoblast cultures was carried out to evaluate involvement of insulin signalling in the phosphorylation pathway. Screening of four Emery­Dreifuss and one limb girdle muscular dystrophy 1B cases was undertaken to investigate lamin A/C phosphorylation in both cultured myoblasts and mature muscle fibres. Results: Phosphorylation of lamin A was observed during myoblast differentiation or proliferation, along with reduced lamin A/C phosphorylation in quiescent myoblasts. Lamin A N-terminus phosphorylation was induced by an insulin stimulus, which conversely did not affect lamin C phosphorylation. Lamin A/C was also hyperphosphorylated in mature muscle, mostly in regenerating fibres. Lamin A/C phosphorylation was strikingly reduced in laminopathic myoblasts and muscle fibres, while it was preserved in interstitial fibroblasts. Conclusions: Altered lamin A/C interplay with a muscle specific phosphorylation partner might be involved in the pathogenic mechanism of Emery­Dreifuss muscular dystrophy and limb girdle muscular dystrophy 1B. [ABSTRACT FROM AUTHOR]

Details the mutational analysis of lamin A/C gene (LMNA) in a large white population of patients affected by dilated cardiomyopathy (DCM) with or without associated symptoms. Missense mutation identified in a family with early atrial fibrillation and a previously described mutation in another family with a quadriceps myopathy associated with DCM.

We present our observations on the skeletal muscle pathology of nine cases from seven families of autosomal dominant Emery-Dreifuss muscular dystrophy (ADEDMD) with identified mutations in the lamin A/C gene, aged 2–35 years at the time of biopsy. The severity of pathological change was moderate and the most common features were variation in fibre size (hypertrophy and atrophy), an increase in internal nuclei and smaller diameter fibres with high oxidative enzyme activity. Only one case showed necrosis, which was present in two separate samples taken from the quadriceps and tibialis anterior, at different ages. Immunocytochemistry detected an age-related reduction of laminin β1 on the muscle fibres in adolescent and adult cases. Antibodies to lamins A and A/C, and emerin did not reveal any detectable differences from controls. Electron microscopy of two out of three cases showed an abnormal distribution of heterochromatin in many fibre nuclei. Our results show that dystrophic changes in skeletal muscle are not a major feature of ADEDMD, and that nuclear abnormalities may be detected with electron microscopy. Immunodetection of reduced laminin β1 may be a useful secondary marker in adults with this disorder, as immunocytochemistry of lamins is not yet of diagnostic use. [ABSTRACT FROM AUTHOR]

AimThe aim of the study was to evaluate electrocardi-ography and echocardiography in the diagnosis of familial hypertrophic cardiomyopathy in children, using the genetic status as the criterion of reference.Methods and ResultsWe analysed 35 children (<18 years) from 13 families with identified mutations: 16 were genetically affected (11·2±3 years), 19 unaffected (13·1±2·8 years). Conventional major diagnostic criteria were: left ventricular wall thickness >95% confidence interval on the echocardiogram; abnormal Q waves, left ventricular hypertrophy (voltage >95th percentile), or marked ST-T changes on the electrocardiogram. Twenty-two minor electrocardiographic and echocardiographic criteria were also analysed. Using major criteria, the specificity of the electrocardiogram and echocardiogram was excellent (100% for both) but sensitivity was particularly low (38% and 50% respectively). However, when four relevant additional criteria (QRS axis, left atrium dimension, intraventricular septum/posterior wall ratio, E/A wave ratio) were taken into account, sensitivity increased to 88% and specificity remained high (95%).Conclusions(1) Familial hypertrophic cardiomyopathy was diagnosed in only ∼50% of genetically affected children by conventional electrocardiographic and/or echocardiographic criteria. (2) Relevant additional diagnostic criteria were selected so that nearly all children considered as healthy carriers of a mutation (based on conventional criteria) could be identified with excellent specificity. [ABSTRACT FROM PUBLISHER]

AimsIt is not known whether the apparent normality of echocardiographic examination results, in subjects bearing a mutation for hypertrophic cardiomyopathy but without ultrasonic left ventricular hypertrophy, is due to incomplete phenotypic expression, or inaccurate echocardiographic criteria. The aim of this study was to search for echocardiographic abnormalities in these patients.Methods and ResultsEchocardiography was performed in 100 subjects from two families with a mutation in the β-MHC (720) or My-BPC (714) genes. We compared genetically affected subjects with an apparently normal left ventricle (thickness <13mm) (20 patients), and non-affected first-degree relatives (61 normal subjects). (1) Patients had a thicker left ventricular wall (9·7±1·4 vs 8·9±1·4mm, P=0·03), a greater indexed mass (107±18 vs 97±17g.m−2, P=0·03), a larger left atrium (27±9 vs 23±10mm3, P=0·09) and lower wall stress (78±11 vs 89±15 103dynes.cm−2, P=0·002); these differences were highly significant after adjustment for height, age and systolic blood pressure either for wall thickness (P=0·073503), mass (P=0·005) or atrial volume (P=0·001), and the ventricular systolic dimension appeared smaller (P=0·01); (2) results remained significant (P<0·01) when a lower cut-off value (≤11mm) or only adults (≥18 years) were considered; (3) a subanalysis of Family 714 (13 patients, 25 normals matched for sex, age and height) showed the same trends.ConclusionIn familial hypertrophic cardiomyopathy, genetically affected subjects with an apparently normal heart by echocardiography show slight ultrasonic structural and functional left ventricular modifications, suggesting that the phenotype of the disease is a continuous spectrum from normal structure to typical hypertrophy. [ABSTRACT FROM PUBLISHER]

Background The gene involved in familial hypertrophic cardiomyopathy on chromosome 11 was recently identified as the cardiac myosin binding protein-C (MyBP-C) gene. The phenotype of two families associated with mutation in this gene is described here and compared to that of five families with mutations in the beta-myosin heavy chain gene.Methods and results In adults (n=33) bearing a splice acceptor site mutation in the MyBP-C gene, penetrance of familial hypertrophic cardiomyopathy was incomplete (69%) and ventricular hypertrophy mild. Among 37 clinical, electrocardiographic and echocardiographic parameters analysed, the only difference with the beta-MHC group (n=35) was a shorter acceleration time of systolic flow in the pulmonary artery (P<0·05). Sensitivity and specificity of diagnostic criteria were similar for the two genes. Cumulative survival rate for the splice acceptor site mutation (90% at 50 years old) was mid-way between that observed with a malignant (Arg403Leu: 42%) and a benign mutation (Arg403Trp: 100%) in the beta myosin heavy chain gene (P=0·002).Conclusions The detailed phenotype associated with a mutation in the MyBP-C gene was no different from that associated with mutations in the beta myosin heavy chain gene, except for prognosis which appeared more benign. These preliminary results suggest that there is no locus-specific genotype–phenotype correlation for the two genes analysed. [ABSTRACT FROM PUBLISHER]

An abstract of the study "Echocardiographic assessment of left ventricular function in mouse model of Emery-Dreifuss muscular dystrophy carrying a LMNA mutation," by S. Varnous et al, is presented.

Purpose. Familial cardiomyopathies are caused by genetic mutations that induce accumulation of misfolded proteins with consequent cardiomyocyte death and maladaptive cardiac remodelling. Molecular chaperones are a family of proteins devoted to prevent accumulation of misfolded proteins by promoting either their refolding or degradation via the ubiquitin-proteasome or the autophagosome systems and can thus represent a potential mean to treat familial cardiomyopathies.Methods. Melusin is a muscle specific chaperone protein whose overexpression effectively prevents maladaptive cardiac remodeling and heart failure both in pressure overload and myocardial infarct mouse models. In this study we use in vivo gene delivery with cardiotropic adeno associated virus 9 vector to induce to increase melusin expression in the heart of mice carrying H222P Lamin A mutation mimicking human Emery-Dreifuss familial cardiomyopathy. Mutant male mice develop spontaneous dilated cardiomyopathy from 4 months of age and die within 10-12 months of age.Results. Homozygous mutant mice were injected with AAV9-Melusin (I.V. injection of 1012 viral particles/mouse) either at 1 month of age before development of the cardiomyopathy or at 4 months when cardiomyopathy was already present to test for both preventive and therapeutic activity. Cardiac function was monitored by echocardiography for the following months. While untreated mice progressively developed left ventricle dilation and reduced contractility (FS%), mice injected with AAV9-Melusin retained physiological level of contractility and were protected toward LV dilation. Ten months after the treatment, 40% of mutant mice died, while 100% of melusin-treated mice were alive. A second group of mutant male mice was injected with AAV9-melusin at 4 months of age when the cardiomyopathy was already detectable. Interestingly melusin prevented the deterioration of contractility in the following 6 months and significantly reduced mortality.Conclusions These data indicate that melusin chaperone overexpression can effectively delay the onset of Emery-Dreifuss cardiomyopathy as well as arrest the progression of the already established pathology. [ABSTRACT FROM AUTHOR]

An abstract of the study "Apical left ventricular aneurysm without atrio-ventricular block due to a lamin A/C gene mutation," by J. F. Forissier et al, is presented.