emerin and Muscle-Weakness

Skeletal muscle weakness is an important determinant of age-related declines in independence and quality of life but its causes remain unclear. Accelerated ageing syndromes such as Hutchinson-Gilford Progerin Syndrome, caused by mutations in genes encoding nuclear envelope proteins, have been extensively studied to aid our understanding of the normal biological ageing process. Like several other pathologies associated with genetic defects to nuclear envelope proteins including Emery-Dreifuss muscular dystrophy, Limb-Girdle muscular dystrophy and congenital muscular dystrophy, these disorders can lead to severe muscle dysfunction. Here, we first describe the structure and function of nuclear envelope proteins, and then review the mechanisms by which mutations in genes encoding nuclear envelope proteins induce premature ageing diseases and muscle pathologies. In doing so, we highlight the potential importance of such genes in processes leading to skeletal muscle weakness in old age.

Topics: Aging; Humans; Lamin Type A; Membrane Proteins; Muscle Weakness; Muscle, Skeletal; Muscular Dystrophies; Mutation; Nuclear Envelope; Nuclear Proteins

A 42-year-old man with a history of two previous coronary embolisms was referred to our hospital. He had been experiencing muscle weakness since he was around 40 years old. He had muscle atrophy of the scapula, upper arm, and lower extremities, and electromyography revealed myogenic changes in the limb muscles. Histopathological analysis of the muscle biopsy specimen revealed a complete deficiency of emerin protein, and genetic examination revealed a mutation in the emerin (EMD) gene, resulting in a diagnosis of Emery-Dreifuss muscular dystrophy (EDMD). EDMD is a muscular disorder with three symptoms: joint contracture at early onset, muscle weakness and atrophy, and cardiac dysfunction. Although this patient showed no obvious joint contracture, the course and clinical symptoms vary among patients. Therefore, in patients in whom clinical diagnosis is difficult, muscle biopsy and genetic testing should be performed for EDMD in order to prevent sudden death due to this disease.

Topics: Adult; Contracture; Humans; Joints; Male; Membrane Proteins; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Muscular Dystrophy, Emery-Dreifuss; Mutation; Nuclear Proteins

Mutations in the lamin A/C gene (LMNA) are known to be involved in several diseases such as Emery-Dreifuss muscular dystrophy, limb-girdle muscular dystrophy type 1B and dilated cardiomyopathies with conduction disease, with considerable phenotype heterogeneity. Here we report on a novel autosomal dominant mutation in LMNA in two direct relatives presenting with different clinical phenotypes, characterized by severe life-threatening limb-girdle muscle involvement and cardiac dysfunction treated with heart transplantation in the proband, and by ventricular tachyarrhythmias with preserved cardiac and skeletal muscle function in her young son. To our knowledge, this is the first report of a duplication in the LMNA gene. The two phenotypes described could reflect different clinical stages of the same disease. We hypothesize that early recognition and initiation of therapeutic manoeuvres in the younger patient may retard the rate of progression of the cardiomyopathy.

Topics: Adult; Amino Acid Sequence; Cardiomyopathy, Dilated; Electrocardiography; Female; Gene Duplication; Heart; Heart Diseases; Heart Transplantation; Humans; Immunohistochemistry; Lamin Type A; Membrane Proteins; Middle Aged; Molecular Sequence Data; Muscle Weakness; Muscle, Skeletal; Muscular Dystrophies, Limb-Girdle; Nuclear Proteins; Pedigree; Phenotype; Stroke Volume; Tomography, X-Ray Computed

Topics: Arrhythmias, Cardiac; Atrial Fibrillation; Biopsy; Contracture; Creatine Kinase; Disease Progression; DNA Mutational Analysis; Electromyography; Genetic Diseases, X-Linked; Genetic Markers; Humans; Male; Membrane Proteins; Middle Aged; Muscle Weakness; Muscle, Skeletal; Muscular Dystrophy, Emery-Dreifuss; Myocardium; Nuclear Proteins; Prognosis

Hauptmann-Thannhauser muscular dystrophy is characterized by the clinical triad of early-onset contractures of elbow, Achilles tendons, and cervical spine, slowly progressive humeroperoneal muscle wasting and weakness, and life-threatening cardiac involvement with conduction blocks manifesting in the third decade. Hauptmann-Thannhauser muscular dystrophy is due to mutations in the LMNA gene affecting the nuclear envelope proteins lamin A and C. We present a 16-year-old German boy with typical muscular involvement and contractures and typical course of Hauptmann-Thannhauser muscular dystrophy due to the novel missense mutation R401C. The data of this family suggest a lower penetrance of muscular and especially cardiac symptoms than expected. Autosomal-dominant Hauptmann-Thannhauser muscular dystrophy and X-chromosomal Emery-Dreifuss muscular dystrophy are not clearly distinguishable by phenotypic criteria. Other muscular diseases associated with contractures and congenital or childhood onset are reviewed.

Topics: Adolescent; Biopsy; Cardiomyopathies; Cell Nucleus; Contracture; Humans; Lamin Type A; Male; Membrane Proteins; Muscle Weakness; Muscle, Skeletal; Muscular Atrophy; Muscular Dystrophy, Emery-Dreifuss; Mutation, Missense; Neurologic Examination; Nuclear Proteins; Pedigree; Phenotype; Syndrome; Thymopoietins

To describe the clinical and histopathologic picture of a childhood-onset, severe variant of scapuloperoneal MD with rigidity of the spine.. Rigidity of the spine is a feature of numerous syndromes, including X-linked Emery-Dreifuss MD, Bethlem myopathy, and the rigid spine syndrome. These are, however, relatively static or very slowly progressive neuromuscular disorders, usually associated with preserved ambulation into adult life.. Five unrelated children (three boys and two girls) presented in the first 2 years of life with poor neck control, waddling gait, and frequent falls. Early wasting of the distal leg muscles, biceps, triceps, and neck muscles was noted in all patients, and all had contractures and severe rigidity of the spine. The condition progressed rapidly, and all patients lost ambulation before the age of 8 years. Cardiac function was normal in all.. Creatine kinase was moderately elevated in all, and muscle biopsy specimens showed nonspecific dystrophic changes with normal expression of dystrophin, the sarcoglycans, and laminin alpha2, alpha5, beta1, and gamma1 chains. Emerin expression was normal in two of the boys whose tissue was available for study.. The distribution of weakness, wasting, and contractures of the patients described resembled Emery-Dreifuss MD, but the rapid progression of weakness and contractures and the involvement of both sexes together with normal emerin expression suggest that this form is not X-linked Emery-Dreifuss MD. We suggest that these patients represent a severe MD characterized by early onset distal wasting and severe rigidity of the spine, with probable autosomal recessive inheritance.

Topics: Age of Onset; Biopsy; Child, Preschool; Contracture; Female; Genes, Recessive; Humans; Infant; Male; Membrane Proteins; Muscle Weakness; Muscle, Skeletal; Muscular Dystrophies; Nuclear Proteins; Phenotype; Thymopoietins; X Chromosome