Welander distal myopathy--an overview

Dynamics of T-Cell Intracellular Antigen 1-Dependent Stress Granules in Proteostasis and Welander Distal Myopathy under Oxidative Stress

T-cell intracellular antigen 1 (TIA1) is an RNA-binding protein that is primarily involved in the post-transcriptional regulation of cellular RNAs. Furthermore, it is a key component of stress granules (SGs), RNA, and protein aggregates that are formed in response to stressful stimuli to reduce cellular activity as a survival mechanism. TIA1 p.E384K mutation is the genetic cause of Welander distal myopathy (WDM), a late-onset muscular dystrophy whose pathogenesis has been related to modifying SG dynamics. In this study, we present the results obtained by analyzing two specific aspects: (i) SGs properties and dynamics depending on the amino acid at position 384 of TIA1; and (ii) the formation/disassembly time-course of TIA1WT/WDM-dependent SGs under oxidative stress. The generation of TIA1 variants—in which the amino acid mutated in WDM and the adjacent ones were replaced by lysines, glutamic acids, or alanines—allowed us to verify that the inclusion of a single lysine is necessary and sufficient to alter SGs dynamics. Moreover, time-lapse microscopy analysis allowed us to establish in vivo the dynamics of TIA1WT/WDM-dependent SG formation and disassembly, after the elimination of the oxidizing agent, for 1 and 3 h, respectively. Our observations show distinct dynamics between the formation and disassembly of TIA1WT/WDM-dependent SGs. Taken together, this study has allowed us to expand the existing knowledge on the role of TIA1 and the WDM mutation in SG formation.

The Multifunctional Faces of T-Cell Intracellular Antigen 1 in Health and Disease

T-cell intracellular antigen 1 (TIA1) is an RNA-binding protein that is expressed in many tissues and in the vast majority of species, although it was first discovered as a component of human cytotoxic T lymphocytes. TIA1 has a dual localization in the nucleus and cytoplasm, where it plays an important role as a regulator of gene-expression flux. As a multifunctional master modulator, TIA1 controls biological processes relevant to the physiological functioning of the organism and the development and/or progression of several human pathologies. This review summarizes our current knowledge of the molecular aspects and cellular processes involving TIA1, with relevance for human pathophysiology.

A Heterologous Cell Model for Studying the Role of T-Cell Intracellular Antigen 1 in Welander Distal Myopathy

Welander distal myopathy (WDM) is a muscle dystrophy characterized by adult-onset distal muscle weakness, prevalently impacting the distal long extensors of the hands and feet. WDM is an autosomal dominant disorder caused by a missense mutation (c.1362G>A; p.E384K) in the TIA1 (T-cell intracellular antigen 1) gene, which encodes an RNA-binding protein basically required for the posttranscriptional regulation of RNAs. We have developed a heterologous cell model of WDM to study the molecular and cellular events associated with mutated TIA1 expression. Specifically, we analyzed how this mutation affects three regulatory functions mediated by TIA1: (i) control of alternative SMN2 (survival motor neuron 2) splicing; (ii) formation, assembly, and disassembly of stress granules; and (iii) mitochondrial dynamics and its consequences for mitophagy, autophagy, and apoptosis. Our results show that whereas WDM-associated TIA1 expression had only a mild effect on SMN2 splicing, it led to suboptimal adaptation to environmental stress, with exacerbated stress granule formation that was accompanied by mitochondrial dysfunction and autophagy. Overall, our observations indicate that some aspects of the cell phenotype seen in muscle of patients with WDM can be recapitulated by ectopic expression of WDM-TIA1 in embryonic kidney cells, highlighting the potential of this model to investigate the pathogenesis of this degenerative disease and possible therapeutics.

A Patient as Art: Andrew Wyeth's Portrayal of Christina Olson's Neurologic Disorder in Christina's World

In Christina's World, one of the most beloved works of American art, Andrew Wyeth painted Christina Olson crawling crablike across the field below her house, raised on emaciated arms, with a swollen knob for an elbow, and hands clenched and gnarled. The significance of these physical abnormalities, and the message Wyeth endeavored to convey via the portrait, are considered here in light of Christina's medical history and the disorder it most likely signifies.

Calf heads on a trophy sign: Miyoshi myopathy

Miyoshi myopathy is an autosomal recessive distal myopathy with predominant involvement of the posterior calf muscles attributed to mutations in the dysferlin gene. We report a 26-year-old male, born of nonconsanginous parentage. He noticed weakness and atrophy of leg muscles with inability to walk on his heels. The creatine kinase concentration was high. The electromyography showed myopathic pattern and the muscle biopsy disclosed dystrophic changes with absence of dysferlin. Miyoshi myopathy may be distinct among the hereditary distal myopathies. There are only few reported cases of Miyoshi myopathy in the world literature. In India only 12 cases were reported who had classical features of Miyoshi myopathy. Our's is a typical case of Miyoshi myopathy, with an affected twin sister as well. He also had “calf heads on a trophy sign” on physical examination, which is considered to be pathognomonic of this disease.

Novel mutations widen the phenotypic spectrum of slow skeletal/β-cardiac myosin (MYH7) distal myopathy

Laing early onset distal myopathy and myosin storage myopathy are caused by mutations of slow skeletal/β-cardiac myosin heavy chain encoded by the gene MYH7, as is a common form of familial hypertrophic/dilated cardiomyopathy. The mechanisms by which different phenotypes are produced by mutations in MYH7, even in the same region of the gene, are not known. To explore the clinical spectrum and pathobiology, we screened the MYH7 gene in 88 patients from 21 previously unpublished families presenting with distal or generalized skeletal muscle weakness, with or without cardiac involvement. Twelve novel mutations have been identified in thirteen families. In one of these families, the father of the proband was found to be a mosaic for the MYH7 mutation. In eight cases, de novo mutation appeared to have occurred, which was proven in four. The presenting complaint was footdrop, sometimes leading to delayed walking or tripping, in members of 17 families (81%), with other presentations including cardiomyopathy in infancy, generalized floppiness, and scoliosis. Cardiac involvement as well as skeletal muscle weakness was identified in nine of 21 families. Spinal involvement such as scoliosis or rigidity was identified in 12 (57%). This report widens the clinical and pathological phenotypes, and the genetics of MYH7 mutations leading to skeletal muscle diseases.

Distal myopathies

The distal myopathies are a heterogeneous group of genetic disorders defined by a predominant distal weakness at onset or throughout the evolution of the disease and by pathological data supporting a myopathic process. The number of genes associated with distal myopathies continues to increase. Fourteen distinct distal myopathies are currently defined by their gene and causative mutations, compared to just five entities delineated on clinical grounds two decades ago. The known proteins affected in the distal myopathies are of many types and include a significant number of sarcomeric proteins. The useful indicators for clinicians to direct towards a correct molecular diagnosis are the mode of inheritance, the age at onset, the pattern of muscle involvement, the serum creatine kinase level and the muscle pathology findings. This review gives an overview of the clinical and genetic characteristics of the currently identified distal myopathies with emphasis on some recent findings.

Welander distal myopathy is caused by a mutation in the RNA-binding protein TIA1

OBJECTIVE

A study was undertaken to identify the molecular cause of Welander distal myopathy (WDM), a classic autosomal dominant distal myopathy.

METHODS

The genetic linkage was confirmed and defined by microsatellite and single nucleotide polymorphism haplotyping. The whole linked genomic region was sequenced with targeted high-throughput and Sanger sequencing, and coding transcripts were sequenced on the cDNA level. WDM muscle biopsies were studied by Western blotting and immunofluorescence microscopy. Splicing of TIA1 and its target genes in muscle and myoblast cultures was analyzed by reverse transcriptase polymerase chain reaction. Mutant TIA1 was characterized by cell biological studies on HeLa cells, including quantification of stress granules by high content analysis and fluorescence recovery after photobleaching (FRAP) experiments.

RESULTS

The linked haplotype at 2p13 was narrowed down to <806 kb. Sequencing by multiple methods revealed only 1 segregating coding mutation, c.1362 G>A (p.E384K) in the RNA-binding protein TIA1, a key component of stress granules. Immunofluorescence microscopy of WDM biopsies showed a focal increase of TIA1 in atrophic and vacuolated fibers. In HeLa cells, mutant TIA1 constructs caused a mild increase in stress granule abundance compared to wild type, and showed slower average fluorescence recovery in FRAP.

INTERPRETATION

WDM is caused by mutated TIA1 through a dominant pathomechanism probably involving altered stress granule dynamics.

A case of hereditary inclusion body myopathy: 1 patient, 2 novel mutations

Hereditary inclusion body myopathy is an autosomal recessive disorder that presents in early adulthood with slowly progressive weakness sparing the quadriceps. Muscle histopathology reveals rimmed vacuoles without inflammation. The disorder is caused by a mutation in the gene for UDP-N-acetylglucosamine 2-epimerase-N-acetylmannosamine kinase (GNE), a bifunctional enzyme involved in protein glycosylation. Over 40 mutations have been described to date. We present a case of a young woman with progressive lower extremity weakness. Clinical presentation, laboratory evaluation, electrodiagnostic testing, muscle pathology, and genetic sequencing are described. The patient was found to have heterozygous mutations in the GNE gene, confirming the diagnosis of hereditary inclusion body myopathy. The mutations she carried have not been described previously. We briefly review the clinical, histopathologic, and molecular genetic findings of this disorder.

Living with a chronic deteriorating disease: the trajectory with muscular dystrophy over ten years

PURPOSE

The aim of the study was to elucidate experiences of living with muscular dystrophy in terms of consequences for activity over 10 years.

METHODS

The study population was identified in a prevalence study in a county of Sweden. Forty-six persons of this cohort with MD were interviewed. A qualitative research approach was chosen. The World Health Organization's International Classification of Functioning, Disability and Health (ICF) was used for categorization.

RESULTS

Nearly all the subjects experienced a deterioration of physical capacity. Most obvious were the restrictions on mobility and increased fatigue and feebleness. The persons described psychosocial consequences of the muscular dystrophy as well as stigma when the disability had become more obvious. In spite of reported distress several persons experienced better psychological adaptation over time. The image of the future was often dark but several focus on today and avoid thoughts about the future. ICF showed some limitation with regard to temporal aspects, emotions and the subjective perspective.

CONCLUSIONS

The knowledge of the trajectory with MD is important in order to offer the best possible treatment and support. Repeated assessment by ICF can serve as a valuable source of such knowledge, and a development of the classification would increase its usefulness in future analysis of functioning and disability.

Quality of life in patients with muscular dystrophy and their next of kin

The aims of this study were to investigate quality of life (QoL) among adult patients with muscular dystrophy (n=46) and their next of kin (n=36) and to investigate the influence of disease-related and demographic factors on QoL. The questionnaire "Subjective estimation of quality of life" was used. The results show that patients had lower QoL than their next of kin regarding having no work or meaningful occupation, energy, self-assuredness, self-acceptance and emotional experiences. Age of onset of disease had an impact on QoL. The need for a ventilator had an influence only on assessment of energy. Patients without a partner assessed lower than those who had a partner. In the case of a person who is young and single the onset of muscular dystrophy reduces the likelihood of having a partner or children and affects personal economy negatively. Assessment of relationship to friends was lower among next of kin who provided daily help than among those who provided help once a week. There is a need for recurrent rehabilitation during life-long disabilities and a need to give particular support to those with early onset of disease, those who are single and those who are childless. It is also important to include the patient's close relations when giving rehabilitation.

Myopathy of distal lower limbs: the clinical variant of Miyoshi

Miyoshi distal dystrophy is a rare myopathy characterized by an autosomal recessive pattern of inheritance and it is prevalent in Japan. Onset of disease is in early adult life with weakness and atrophy of the leg muscles. Recently gene linkage to chromosome 2p12-14 has been established. We report three sisters, born of consanguineous parents. All of them noticed weakness and atrophy of leg muscles, and could not walk on their heels. In all of them the creatine kinase concentrations were very high. The electromyography showed myopathic patterns and the muscle biopsy disclosed dystrophic changes and an absence of dysferlin. There are few cases reported of Miyoshi distal dystrophy in Latin America. The Miyoshi myopathy may be distinct among the hereditary distal myopathies.

The illness experience of adult persons with muscular dystrophy

PURPOSE

The purpose of the present study is to describe the illness experience of persons with muscular dystrophy, their experience of activities of daily living, and whether there are any differences in how different types of muscular dystrophy affect people's lives.

METHOD

Fifty-eight subjects were interviewed on two occasions. The interviews with 15 subjects (five for each type of muscular dystrophy; proximal muscular dystrophy, myotonic muscular dystrophy, myopathia distalis tarda hereditaria) were subjected to inductive content analysis. The interviews were about experiences of the first symptoms, learning of the diagnosis, life in general from then to the present, managing daily living and thoughts about the future.

RESULTS

After a deductive validation procedure the results were presented as three core narratives', one for each type of muscular dystrophy. The illness experience was mainly similar irrespective of type of muscular dystrophy. Learning of the incurable, progressive, hereditary disease was traumatic and the subjects hoped the diagnosis was wrong. They felt uncertain about the future, and were sad and worried about the consequences of a hereditary disease for their children.

CONCLUSION

The results will enable rehabilitation staff to better understand the patient's need for psychosocial support.

An autosomal dominant early adult-onset distal muscular dystrophy

In this study we describe an autosomal dominant distal muscular dystrophy in a small Austrian family. The myopathy started in early adulthood with a slowly progressive weakness of the muscles of the anterior tibial compartment, followed by the long finger extensors and sternocleidomastoids in some family members. Other muscles were spared. Histopathology showed fiber size variation and autophagic vacuoles. This disease pattern is similar to Laing distal myopathy, which has been described previously in only one other family.

Distal myopathies

Among various previously described distal myopathies, several diseases have now been established as clinically and genetically distinct entities. The most representative diseases are dominantly inherited Welander distal myopathy and tibial muscular dystrophy, and the recessively inherited distal myopathy with rimmed vacuoles and distal muscular dystrophy (Miyoshi myopathy). Since the discovery of the gene loci for several distal myopathies, several diseases previously categorized as different disorders have now proven to be the same or allelic disorders (e.g. distal myopathy with rimmed vacuoles and hereditary inclusion body myopathy, Miyoshi myopathy and limb-girdle muscular dystrophy with gene locus at 2p13). Except for Miyoshi myopathy, which has the typical findings of muscular dystrophy, most of the distal myopathies share the common pathologic features of myopathic changes with rimmed vacuoles. The pathologic changes are somewhat similar to those seen in chronic muscular dystrophy, but necrotic and regenerative processes are less prominent and creatine kinase levels are either normal or only mildly elevated. Further study is necessary to determine why rimmed vacuoles are so common in the distal myopathies, and what role they play in the pathogenesis of muscle fibre atrophy and loss, predominantly in the distal portions of the extremities.

Hereditary inclusion body myopathies

Hereditary inclusion body myopathies comprise autosomal recessive and autosomal dominant muscle disorders that have a variable clinical phenotype but share similar morphological features. These include rimmed vacuoles within muscle fibres and collections of intrasarcoplasmic and intranuclear tubulofilamentous inclusions, 16-18 nm in external diameter. The resemblances and the differences between the sporadic and the hereditary inclusion body myopathies are discussed. Recent advances in the identification of various proteins involved in these diseases are mentioned because they have provided better insight into their underlying pathophysiological mechanisms. Linkage studies have allowed the localization of the genetic defect of some hereditary inclusion body myopathies and related disorders, contributing to their individualization.