The cytoplasmic bodies in a congenital myopathy can be stained with antibodies to desmin, the muscle-specific intermediate filament protein

The FLNC Ala1186Val Variant Linked to Cytoplasmic Body Myopathy and Cardiomyopathy Causes Protein Instability

Filamin C-related disorders include myopathies and cardiomyopathies linked to variants in the FLNC gene. Filamin C belongs to a family of actin-binding proteins involved in sarcomere stability. This study investigates the pathogenic impact of the FLNC c.3557C > T (p.Ala1186Val) pathogenic variant associated with an early-onset cytoplasmic body myopathy and cardiomyopathy in three unrelated patients. We performed clinical imaging and myopathologic and genetic characterization of three patients with an early-onset myopathy and cardiomyopathy. Bioinformatics analysis, variant interpretation, and protein structure analysis were performed to validate and assess the effects of the filamin C variant. All patients presented with a homogeneous clinical phenotype marked by a severe contractural myopathy, leading to loss of gait. There was prominent respiratory involvement and restrictive or hypertrophic cardiomyopathies. The Ala1186Val variant is located in the interstrand loop involved in intradomain stabilization and/or interdomain interactions with neighbor Ig-like domains. 3D modeling highlights local structural changes involving nearby residues and probably impacts the protein stability, causing protein aggregation in the form of cytoplasmic bodies. Myopathologic studies have disclosed the prominent aggregation and upregulation of the aggrephagy-associated proteins LC3B and p62. As a whole, the Ala1186Val variant in the FLNC gene provokes a severe myopathy with contractures, respiratory involvement, and cardiomyopathy due to protein aggregation in patients' muscles.

Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?

Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.

Remodeling of Cardiomyocytes: Study of Morphological Cellular Changes Preceding Symptomatic Ischemic Heart Failure

Although major pathogenesis mechanisms of heart failure (HF) are well established, the significance of early (mal)adaptive structural changes of cardiomyocytes preceding symptomatic ischemic HF remains ambiguous. The aim of this study is to present the morphological characterization of changes in cardiomyocytes and their reorganization of intermediate filaments during remodeling preceding symptomatic ischemic HF in an adult human heart. A total of 84 myocardial tissue samples from middle-left heart ventricular segments were analyzed histomorphometrically and immunohistochemically, observing the cardiomyocyte's size, shape, and desmin expression changes in the remodeling process: Stage A of HF, Stage B of HF, and Stages C/D of HF groups (ACC/AHA classification). Values p < 0.05 were considered significant. The cellular length, diameter, and volume of Stage A of HF increased predominantly by the diameter vs. the control group (p < 0.001) and continued to increase in Stage B of HF in a similar pattern (p < 0.001), increasing even more in the C/D Stages of HF predominantly by length (p < 0.001). Desmin expression was increased in Stage A of HF vs. the control group (p < 0.001), whereas it was similar in Stages A and B of HF (p > 0.05), and most intense in Stages C/D of HF (p < 0.001). Significant morphological changes of cardiomyocytes and their cytoskeletal reorganization were observed during the earliest remodeling events preceding symptomatic ischemic HF.

Is Desmin Propensity to Aggregate Part of its Protective Function?

Desmin is the major protein component of the intermediate filaments (IFs) cytoskeleton in muscle cells, including cardiac. The accumulation of cleaved and misfolded desmin is a cellular hallmark of heart failure (HF). These desmin alterations are reversed by therapy, suggesting a causal role for the IFs in the development of HF. Though IFs are known to play a role in the protection from stress, a mechanistic model of how that occurs is currently lacking. On the other hand, the heart is uniquely suited to study the function of the IFs, due to its inherent, cyclic contraction. That is, HF can be used as a model to address how IFs afford protection from mechanical, and possibly redox, stress. In this review we provide a brief summary of the current views on the function of the IFs, focusing on desmin. We also propose a new model according to which the propensity of desmin to aggregate may have been selected during evolution as a way to dissipate excessive mechanical and possibly redox stress. According to this model, though desmin misfolding may afford protection from acute injury, the sustained or excessive accumulation of desmin aggregates could impair proteostasis and contribute to disease.

Molecular insights into cardiomyopathies associated with desmin (DES) mutations

Increasing usage of next-generation sequencing techniques pushed during the last decade cardiogenetic diagnostics leading to the identification of a huge number of genetic variants in about 170 genes associated with cardiomyopathies, channelopathies, or syndromes with cardiac involvement. Because of the biochemical and cellular complexity, it is challenging to understand the clinical meaning or even the relevant pathomechanisms of the majority of genetic sequence variants. However, detailed knowledge about the associated molecular pathomechanism is essential for the development of efficient therapeutic strategies in future and genetic counseling. Mutations in DES, encoding the muscle-specific intermediate filament protein desmin, have been identified in different kinds of cardiac and skeletal myopathies. Here, we review the functions of desmin in health and disease with a focus on cardiomyopathies. In addition, we will summarize the genetic and clinical literature about DES mutations and will explain relevant cell and animal models. Moreover, we discuss upcoming perspectives and consequences of novel experimental approaches like genome editing technology, which might open a novel research field contributing to the development of efficient and mutation-specific treatment options.

Cytoplasmic body pathology in severe ACTA1-related myopathy in the absence of typical nemaline rods

Mutations in ACTA1 cause a group of myopathies with expanding clinical and histopathological heterogeneity. We describe three patients with severe ACTA1-related myopathy who have muscle fiber cytoplasmic bodies but no classic nemaline rods. Patient 1 is a five-year-old boy who presented at birth with severe weakness and respiratory failure, requiring mechanical ventilation. Whole exome sequencing identified a heterozygous c.282C>A (p.Asn94Lys) ACTA1 mutation. Patients 2 and 3 were twin boys with hypotonia, severe weakness, and respiratory insufficiency at birth requiring mechanical ventilation. Both died at 6 months of age. The same heterozygous c.282C>A (p.Asn94Lys) ACTA1 mutation was identified by whole exome sequencing. We conclude that clinically severe ACTA1-related myopathy can present with muscle morphological findings suggestive of cytoplasmic body myopathy in the absence of definite nemaline rods. The Asn94Lys mutation in skeletal muscle sarcomeric α-actin may be linked to this histological appearance. These novel ACTA1 cases also illustrate the successful application of whole exome sequencing in directly arriving at a candidate genetic diagnosis in patients with unexpected phenotypic and histologic features for a known neuromuscular gene.

Desmin-related cardiomyopathy: an unfolding story

The intermediate filament protein desmin is an integral component of the cardiomyocyte and serves to maintain the overall structure and cytoskeletal organization within striated muscle cells. Desmin-related myopathy can be caused by mutations in desmin or associated proteins, which leads to intracellular accumulation of misfolded protein and production of soluble pre-amyloid oligomers, which leads to weakened skeletal and cardiac muscle. In this review, we examine the cellular phenotypes in relevant animal models of desmin-related cardiomyopathy. These models display characteristic sarcoplasmic protein aggregates. Aberrant protein aggregation leads to mitochondrial dysfunction, abnormal metabolism, and altered cardiomyocyte structure. These deficits to cardiomyocyte function may stem from impaired cellular proteolytic mechanisms. The data obtained from these models allow a more complete picture of the pathology in desmin-related cardiomyopathy to be described. Moreover, these studies highlight the importance of desmin in maintaining cardiomyocyte structure and illustrate how disrupting this network can be deleterious to the heart. We emphasize the similarities observed between desmin-related cardiomyopathy and other protein conformational disorders and speculate that therapies to treat this disease may be broadly applicable to diverse protein aggregation-based disorders.

Diagnostic immunohistochemistry in neuromuscular disorders

Most neuromuscular disorders display only non-specific myopathological features in routine histological preparations. However, a number of proteins, including sarcolemmal, sarcomeric, and nuclear proteins as well as enzymes with defects responsible for neuromuscular disorders, have been identified during the past two decades, allowing a more specific and firm diagnosis of muscle diseases. Identification of protein defects relies predominantly on immunohistochemical preparations and on Western blot analysis. While immunohistochemistry is very useful in identifying abnormal expression of primary protein abnormalities in recessive conditions, it is less helpful in detecting primary defects in dominantly inherited disorders. Abnormal immunohistochemical expression patterns can be confirmed by Western blot analysis which may also be informative in dominant disorders, although its role has yet to be established. Besides identification of specific protein defects, immunohistochemistry is also helpful in the differentiation of inflammatory myopathies by subtyping cellular infiltrates and demonstrating up-regulation of subtle immunological parameters such as cell adhesion molecules. The role of immunohistochemistry in denervating disorders, however, remains controversial in the absence of a reliable marker of muscle fibre denervation. Nevertheless, as well as the diagnostic value of immunocytochemical analysis it may also widen understanding of muscle fibre pathology as well as help in the development of therapeutic strategies.

Congenital myopathies in the new millennium

Few medical disciplines have benefited so enormously from the molecular revolution as myology. Whereas the congenital myopathies have flourished from enzyme histochemistry and electron microscopy, defining individual congenital myopathies by structural abnormalities, genetic research has only recently focused on congenital myopathies. However, a number of congenital myopathies have been molecularly elucidated: central and multiminicore diseases, nemaline myopathy, myotubular myopathy, and congenital myopathy marked by aggregation of proteins, giving rise to the concept of protein aggregate myopathies, to which now desminopathies, alpha-B crystallinopathies, selenoproteinopathy, myotilinopathy, actinopathies, and myosinopathies belong. Based on recent identification of mutations in respective genes, the principle "from morphology, that is, immunohistochemistry, to molecular analysis" through recognition of certain accrued proteins within muscle fibers and subsequent analysis of their respective genes has resulted in a wealth of genetic data and in reconsidering classification and nosologic interpretation of certain congenital myopathies. This heuristic principle needs to be further applied to other genetically still obscure congenital myopathies.

Cytoplasmic body myopathy masquerading as motor neuron disease

Cytoplasmic body myopathy (CBM) is characterized by proteinaceous inclusion bodies in muscle tissue. A 43-year-old woman presented with rapidly progressive weakness and dysphagia. Electromyography (EMG) elsewhere demonstrated lower-limb chronic partial denervation. Muscle biopsy showed fiber size variation without diagnostic features. A diagnosis of possible motor neuron disease was made and the patient was commenced on riluzole. Subsequently, the patient's condition stabilized, prompting reassessment. Repeat EMG demonstrated no features of denervation and was more suggestive of a myopathic process. Review of the original muscle biopsy showed cytoplasmic bodies. The case highlights a further diagnostic possibility in the assessment of patients with "possible" motor neuron disease. The clinical features of CBM are briefly reviewed.

Congenital myopathies at their molecular dawning

The introduction and application of molecular techniques have commenced to influence and alter the nosology of congenital myopathies. Long-known entities such as nemaline myopathies, core diseases, and desmin-related myopathies have now been found to be caused by unequivocal mutations. Several of these mutations and their genes have been identified by analyzing aggregates of proteins within muscle fibers as a morphological hallmark as in desminopathy and actinopathy, the latter a subtype among the nemaline myopathies. Immunohistochemistry has played a crucial role in recognizing this new group of protein aggregate myopathies within the spectrum of congenital myopathies. It is to be expected that other congenital myopathies marked by inclusion bodies may turn out to be such protein aggregate myopathies, depending on analysis of individual proteins within these protein aggregates and their association with putative gene mutations.

Protein surplus myopathies and other rare congenital myopathies

The protein surplus myopathies have emerged as a newly recognized subgroup of morphologically defined myopathies within the spectrum of congenital myopathies because of the accumulation of protein aggregates, some of them mutant proteins. Currently, nosologic, including molecular criteria include desmin-related myopathies, actinopathies, and hereditary inclusion body myopathies, whereas hyaline body myopathy is still a putative form of protein surplus myopathy because of lack of any molecular data. The congenital myopathies (CM), foremost including nemaline and myotubular myopathies, have given evidence that, despite their epidemiologic rarity, the molecular age has dawned in CM and has even revealed surprising new nosologic features requiring reassessment and reclassification of certain CM. It is to be expected that a recently updated ENMC Consortium on "Protein surplus and other congenital myopathies" may procure important new information.

Congenital myopathies

Most congenital myopathies have been defined on account of the morphological findings in enzyme histochemical preparations. In effect, the diagnosis of this group of diseases continues to be made on the histological pattern of muscle biopsies. However, progress has been made in elucidating the molecular genetic background of several of the congenital myopathies. In this updated review we address those congenital myopathies for which gene defects and mutant proteins have been found (central core disease, nemaline myopathies, desminopathy, actinopathy, certain vacuolar myopathies, and myotubular myopathy) and the other disease with central nuclei (centronuclear myopathy).

Surplus protein myopathies

Certain muscular dystrophies are marked by absence or reduction of mutant proteins, foremost dystrophinopathies and sarcoglycanopathies. Conversely, other sporadic and familial neuromuscular conditions are marked by a surplus of proteins present in a granular or filamentous form, such as desmin-related myopathies, actinopathy and, perhaps, hyaline body myopathy. This emerging group of congenital myopathies is clinically, immunohistochemically, and genetically diverse. Clinically, early- and late-onset diseases with variable courses are described. Immunohistochemically, mutant gene-related and other proteins have been identified by immunohistochemistry. Mutations in the desmin and alpha-B crystallin genes have been discovered in desminopathies. Mutations in the actin gene, but in no other genes have been revealed in actinopathy. Surplus sarcoplasmic and/or intranuclear nemaline bodies have been related to mutant tropomyosin-3, actin and nebulin genes. This emerging concept of surplus protein myopathies will require substantial investigation to further interpret the results of present and future studies.

Progress in desmin-related myopathies

Desmin-related myopathies are sporadic and familial neuromuscular conditions of considerable clinical heterogeneity uniformly marked by the pathologic accretion of desmin, often in a filamentous fashion. A large variety of other proteins, some of them cytoskeletal, also accrue. Morphologically, two types may be distinguished, one characterized by inclusions such as cytoplasmic and spheroid bodies or desmin-dystrophin plaques and another marked by granulofilamentous material. The genetic spectrum of desmin-related myopathies is quite diverse in that missense mutations and deletions in the desmin gene and a missense mutation in the alpha-B crystallin gene have been detected and several genes on other chromosomes have been mapped; the encoded protein products of these genes, however, are unknown. Accumulation of desmin and other proteins appears to be due to impaired nonlysosomal proteolysis. Mutant desmin that appears to be hyperphosphorylated seems to act as a seed protein for filament aggregation, inducing formation of inclusions and granulofilamentous material in these conditions. This condition is part of the group of disorders known as "surplus protein myopathies."

Gene-related protein surplus myopathies

Numerous muscular dystrophies, such as dystrophinopathies, sarcoglycanopathies, and emerino- and laminopathies, are marked by the absence or reduction of mutant transsarcolemmal or nuclear proteins. In addition to these recently identified minus-proteinopathies, there are a growing number of plus-proteinopathies among neuromuscular disorders marked by a surplus or excess of endogenous proteins within muscle fibers of different, i.e., nontranssarcolemmal and nonnuclear types. These proteins are often filamentous; for example, desmin and actin accrue in respective desmin-related myopathies, among which are entities marked by mutant desmin, true desminopathies, and actinopathy, the latter often seen as a subgroup in nemaline myopathies. Desmin-related myopathies consist largely of those marked by desmin-containing inclusions and those characterized by desmin-containing granulofilamentous material. When mutations in the desmin gene can be identified, the mutant desmin is thought to form the major myopathological lesion. Together with desmin, other proteins often accumulate. The spectrum of these proteins is quite diverse and encompasses such proteins as dystrophin, nestin, vimentin, alphaB-crystallin, ubiquitin, amyloid precursor protein, and beta-amyloid epitopes, as well as gelsolin and alpha(1)-antichymotrypsin. Among these associated proteins, one, alphaB-crystallin, has been found mutant in one large family, justifying the term alphaB-crystallinopathy as a separate condition among the desmin-related myopathies. Other proteins accruing with desmin have not yet been identified as mutant in desmin-related myopathies. Mutations in the desmin gene entail missense mutations and small deletions. The formation of mutant actin may lead to aggregates of actin filaments which may or may not be associated with formation of sarcoplasmic and/or intranuclear nemaline bodies. A considerable number of missense mutations in the sarcomeric actin gene ACTA1 have been discovered in patients with nemaline myopathy and also in a few patients without myopathological evidence of nemaline bodies in biopsied skeletal muscle fibres. Apart from alphaB-crystallin, no other proteins coaggregating with actin in actin filament aggregates of actinopathy or the actin mutation type of nemaline myopathy have so far been identified. Two further candidates for protein surplus myopathies are hyaline body myopathy, which is marked by accumulation of granular nonfilamentous material within muscle fibers that is rich in myosin and adenosine triphosphatase activities, and hereditary inclusion body myopathies, which are marked by accumulation of tubulofilaments similar to the helical filaments of Alzheimer neurofibrillary tangles. These tubulofilaments consist of diverse proteins as well, though no mutant protein has yet been discovered. So far, no genes responsible for familial hyaline body and hereditary inclusion body myopathies have been identified. The discovery of mutant proteins, desmin, alphaB-crystallin, and actin, as components of surplus or excess proteins accumulating in muscle fibers in certain neuromuscular conditions is responsible for the recent emergence of this new concept of gene-related protein surplus myopathies.

Congenital myopathies with inclusion bodies: a brief review

Based on morphological abnormalities, congenital myopathies can be classified into several categories: (1) enzyme histochemically abnormal appearance without structural pathology, e.g., congenital fibre type disproportion or congenital fibre type uniformity; (2) abnormally placed nuclei, e.g. myotubular and centronuclear myopathies; (3) disruption of normal intrinsic structures, largely sarcomeres, e.g. central cores and minicores; (4) abnormal inclusions within muscle fibres. Several such inclusions are derived from pre-existing structures, most notably rods or nemaline bodies. Other derivatives of Z-band material are cytoplasmic bodies and possibly related inclusions as spheroid bodies, sarcoplasmic bodies or Mallory body-like inclusions. These inclusions share accumulation of desmin, the muscle fibre-specific intermediate filament, and of other proteins, some of them physiological, but others quite abnormal. Inclusions without identified precursors are fingerprint bodies, reducing bodies, cylindrical spirals, and Zebra bodies. Experimental models and tissue culture reproduction are necessary to further clarify significance of these inclusions in congenital myopathy pathology.

Spheroid body myopathy revisited

Having reported spheroid body myopathy from Indiana (IN) inherited in an autosomal-dominant fashion several years ago, we now describe additional findings from the Oregon branch--briefly recorded earlier--and confirm earlier studies in another clinically affected IN member of this kinship demonstrating identical spheroid bodies within the myopathic muscle specimens. The spheroid bodies also contained increased amounts of desmin, alpha-B crystallin, and ubiquitin within muscle fibers. Our studies now have established that spheroid body myopathy is a member of the growing family of desminopathic neuromuscular conditions.

Familial mixed congenital myopathy with rigid spine phenotype

We describe a father and daughter with a rigid spine syndrome and proximal myopathy. The index patient was a 42-year-old man, who died from respiratory failure after a lifelong, slowly progressive proximal myopathy and a rigid spine phenotype. This was morphologically characterized by cytoplasmic bodies, increased desmin, features of reducing-body myopathy, and sarcoplasmic and intranuclear tubulofilamentous inclusions. These cases are characterized by an early onset and possibly autosomal-dominant inheritance, with associated complex structural hallmarks of both desmin-related and inclusion body myopathies. Together they may be defined as a complex mixed congenital myopathy with a rigid spine phenotype.

Congenital myopathy in Braunvieh x Brown Swiss calves

A hitherto unknown skeletal muscle disorder is described in six Braunvieh x Brown Swiss calves. The animals showed rapidly progressing muscular weakness and became recumbent within 2 weeks of birth. Histological examination of skeletal muscle revealed a marked variation in muscle fibre size, internally placed nuclei, segmental loss of cross-striation with disorganization of myofibrils, and accumulation of nemaline rods. The most distinctive histological finding was intracytoplasmic, homogeneous, mostly crescent-shaped areas at the periphery of numerous muscle fibres. Electron microscopically, accumulations of tightly packed, parallel filamentous structures, about 20 nm in diameter, were detected in these areas. Enzyme histochemistry showed that all muscle fibre types were affected. Vimentin and dystrophin immunohistochemistry revealed normal antigen distribution within connective tissue components and at the periphery of each muscle fibre, respectively. The lesions could be readily distinguished from other neurological and neuromuscular disorders previously described in Braunvieh x Brown Swiss or American Brown Swiss Cattle. The disease appears to be a novel congenital myopathy in this breed, and a hereditary aetiology is suspected.

Congenital myopathies

The congenital myopathies (CM) are a group of non or little progressive neuromuscular conditions, often hereditary, delineated by morphological techniques, ie, enzyme histochemistry and electron microscopy. The catalogue of CM entailing well known "classic" conditions as central core disease, nemaline myopathy, and centronuclear myopathy has continuously been expanded, now comprising some 40 conditions. Nosologic advances have occurred with immunohistochemical techniques that show generalized or focal protein abnormalities within muscle fibers of certain CM, but at much slower pace as to localization of CM genes. So far, only those for central core disease, nemaline myopathy, and myotubular myopathy have been reported. Epidemiological rarity and nosographic controversy of CM have contributed to this lack of molecular genetic progress in CM.

Chromosome 12-linked autosomal dominant scapuloperoneal muscular dystrophy

Scapuloperoneal syndromes are characterized by their distribution of muscle weakness and wasting. The reported pattern of inheritance has been variable. Both neurogenic and myopathic forms of autosomally dominantly inherited scapuloperoneal syndrome have been described. It has been suggested that these are variants of other neuromuscular diseases. We examined 44 members from a family with 14 members affected with a scapuloperoneal syndrome. Physiological and histological analysis implied that this condition is predominantly myopathic. Linkage analysis was done to confirm the genetic etiology of the disease in this family and to evaluate the possibility that it is a allelic variant of other neuromuscular diseases. Genetic analysis demonstrated linkage of the disease to chromosome 12, which makes it genetically distinct from other loci known to cause neuromuscular disease. Muscle fibers with hyaline desmin-containing cytoplasmic inclusions in combination with focal myopathic changes may be a disease-specific morphological marker of the disease.

Desmin-related neuromuscular disorders

Desmin, the intermediate filament protein of skeletal muscle fibers, cardiac myocytes, and certain smooth muscle cells, is a member of the cytoskeleton linking Z-bands with the plasmalemma and the nucleus. The pathology of desmin in human neuromuscular disorders is always marked by increased amounts, diffusely or focally. Desmin is highly expressed in immature muscle fibers, both during fetal life and regeneration as well as in certain congenital myopathies, together with vimentin. Desmin is also enriched in neonatal myotonic dystrophy and small fibers in infantile spinal muscular atrophy. Focal accretion of desmin may be twofold, in conjunction with certain inclusion bodies, cytoplasmic and spheroid bodies, and in a more patchy fashion, granulofilamentous material. Both lesions have been found in certain families, affected by a myopathy and/or cardiomyopathy. Other proteins, e.g., dystrophin, vimentin, actin, ubiquitin, and alpha-B crystallin, may also be overexpressed. Desmin pathology may be genetically regulated or may merely reflect profoundly impaired metabolism of several proteins within myofibers.

Hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle

We describe a family line with an autosomal recessive disease of muscular dystrophy of the diaphragmatic muscles in Holstein-Friesian cattle. Histopathological examination in the present cases revealed various degenerative changes in the diaphragmatic and other thoracic muscles as follows: variation in muscle fiber diameter, fiber splitting, sarcoplasmic masses, ring fiber, vacuolar and hyalinized degeneration of muscle fibers. In addition, central core-like structures were the prominent features in the diaphragmatic muscles, occupying the center of the fiber or scattered within the fiber. These pathological alterations are consistent with the diaphragmatic myopathy previously reported in Meuse-Rhine-Yssel cattle in the Netherlands. The fibers containing core-like structures consisted of three distinct zones which could be well distinguished by NADH-tetrazolium reductase activity. This activity was absent in the innermost zone, decreased in the intermediate zone, and normal or increased in the periphery. Electron microscopically, this structure appeared to be composed of focal myofibrillar degeneration beginning with streaming or disintegration of the Z disk. We discuss here the similarity between this core-like structure and the other alternative organelles that have been reported previously, and a possible defect or storage in the cytoskeleton from the findings of the Z disk abnormalities.

Desmin myopathy: a multisystem disorder involving skeletal, cardiac, and smooth muscle

Myopathy associated with desmin-type intermediate filaments is an uncommon disorder of skeletal and/or cardiac muscle. The present study focuses on a 28-year-old man with generalized muscular atrophy, cardiomyopathy, and intestinal malabsorption and pseudo-obstruction. Abundant sarcoplasmic granular and filamentous aggregates that were ultrastructurally continuous with Z lines or dense bodies and exhibited intense immunostaining for desmin were present throughout the skeletal musculature, myocardium, and smooth muscle of the intestine. Moreover, neurofilament-immunoreactive axonal spheroids were identified in the spinal cord and roots. These widely distributed findings illustrate the multisystemic character of desmin myopathy, which in this instance first adds intestinal smooth muscle involvement to its already known skeletal and cardiac muscle manifestations. The additional presence of neurofilament aggregates in the spinal cord and roots constitutes an extremely rare conjunction of intermediate filament pathology of the neuromuscular system.

Cytoplasmic body myopathy: familial cases with accumulation of desmin and dystrophin. An immunohistochemical, immunoelectron microscopic and biochemical study

Muscle biopsy samples from five patients with cytoplasmic body myopathy (CBM) were investigated by immunohistochemical (antibodies to desmin, actin, dystrophin, spectrin, alpha actinin and utrophin), immunoelectron microscopic (antibodies to desmin, actin and dystrophin) and biochemical (desmin, dystrophin, actin and utrophin western blots) methods. Using immunofluorescence it was shown that the centers of cytoplasmic bodies (CB) were stained by anti-actin, anti-utrophin and three different anti-dystrophin antibodies. The peripheries were labeled by the anti-desmin antibody. Moreover, fibers containing CB showed a markedly increased staining of their entire sarcoplasm with the anti-desmin antibody. Using immunoelectron microscopy it was shown that anti-dystrophin antibodies selectively stained the external limit of the central granular region. Anti-desmin antibody labeled the filamentous halo, and anti-actin antibody stained the central core and the radiating filaments. Biochemical studies showed storage of desmin and dystrophin, both of normal molecular weight. Our results suggest that CBM should be considered along with a wider group of intermediate filament pathologies that include desmin-storage myopathies.

Desmin myopathy with cardiomyopathy

We report a case of abnormal desmin accumulation within the muscle of a 30-year-old female with a 2-year history of cardiomyopathy and axial muscle weakness. Serum creatine kinase was normal. A quadriceps muscle biopsy revealed pink hyaline inclusions, which stained for acid phosphatase and with PAS and were present in both fibre types. Electron microscopy showed these inclusions to consist of aggregates of irregularly arranged 6- to 15-nm-diameter filaments enmeshed within a central core of dense granulo-amorphous material. In other areas, the granulo-amorphous material lay as irregular patches within the sarcoplasm, mainly at the level of the "Z" band causing disruption of the sarcomere. Immunoelectron microscopy using colloidal gold showed that the dense amorphous material reacted strongly with desmin antisera and could, therefore, represent a defective or phosphorylated form of the protein.

Hereditary distal myopathy with granulo-filamentous cytoplasmic inclusions containing desmin, dystrophin and vimentin

A 56-year-old female and her 34-year-old daughter presented with a predominantly distal myopathy affecting the peroneal and calf muscles, neck flexors and hand muscles. Both patients and two other daughters had cardiac arrhythmias, three requiring the insertion of cardiac pacemakers. Skeletal muscle biopsies revealed a complex myopathic process with granular degeneration, rimmed vacuoles and eosinophilic cytoplasmic inclusions. Ultrastructurally, the inclusions were composed of electron dense granular material and filaments forming linear masses beneath the sarcolemma and rounded masses within the cytoplasm of the fibres. Immunohistochemistry revealed labelling of the inclusions for desmin, dystrophin and vimentin, but not for alpha-actinin, spectrin, utrophin or myosin heavy chains. This family shows a hereditary distal myopathy with some features in common with previously-reported cases in which biopsies showed cytoplasmic inclusion bodies containing desmin. This group of diseases is clinically and pathologically heterogeneous. In the present cases, the accumulation of cytoplasmic filaments may reflect a generalised disturbance of filamentous protein metabolism rather than a specific disorder of desmin.

Familial cardiomyopathy, mental retardation and myopathy associated with desmin-type intermediate filaments

The clinical and morphological findings of a familial case affected by mental retardation, severe biventricular hypertrophic cardiomyopathy and vacuolar myopathy are reported. The phenotype of this patient is similar to that described by other authors, in which a lysosomal glycogen storage disease with normal acid maltase levels was suspected. However, in our case the vacuoles were stained by several antibodies directed against various sarcolemmal proteins, such as dystrophin and spectrin, and therefore, were not of lysosomal origin. Some of these vacuoles were clearly derived from the splitting of the fibres and invagination of the extracellular space; autophagic vacuoles were not observed. The accumulation of desmin-type, intermediate filaments was demonstrated on immunocytochemistry both in the skeletal and cardiac muscles. A brother of the propositus was also affected by mental retardation, severe cardiomyopathy and died suddenly at the age of 24 yr. A cardiomyopathy and mental subnormality were also present in other male cousins of the proband, while sudden death occurred in several females relatives, whose intelligence was normal. None of these latter individuals was available for further investigation. This report expands the spectrum of desmin associated myopathy and cardiomyopathy to include a familial condition with associated mental retardation.

New insights into the pathogenesis of congenital myopathies

Congenital myopathies are developmental disorders of muscle that are best understood in the context of ontogenesis. Segmental amyoplasia results from a defective somite, usually because of lack of induction by the notochord and neural tube; the connective tissue matrix of the muscle is derived from lateral mesoderm and is present, but the myocytes are derived from somitic mesoderm and are replaced by adipose cells. Generalized amyoplasia is due to defective myogenic regulatory genes. X-linked recessive myotubular myopathy is associated with overexpression of vimentin and desmin, fetal intermediate filaments that attach to nuclear, mitochondrial, and inner sarcolemmal membranes and Z-bands of sarcomeres to preserve the morphologic organization of the myotube. Neonatal myotonic dystrophy is a true maturational delay in muscle development. Congenital muscle fiber-type disproportion is a syndrome of multiple etiologies but in some cases is associated with cerebellar hypoplasia and may be the result of abnormal suprasegmental stimulation of the developing motor unit at 20 to 28 weeks' gestation, mediated through bulbospinal pathways but not the corticospinal tract. Maturational delay of muscle in late developmental stages is less specific than in stages before midgestation. The Proteus syndrome is a muscular dysgenesis; abnormal paracrine growth factors and perhaps altered genes that regulate muscle differentiation and growth, such as myoD and myogenin, are the suspected cause. Focal proliferative myositis may be another example of a "paracrine myopathy."

Desmin pathology in neuromuscular diseases

Desmin is an intermediate filament protein that in striated muscle is normally located at Z-bands, beneath the sarcolemma, and prominently at neuromuscular junctions. It is abundant during myogenesis and in regenerating fibers, but decreases in amount with maturation; in regenerating and denervated muscle fibers it is co-expressed with vimentin. Aggregates of desmin occur as nonspecific cytoplasmic bodies or cytoplasmic spheroid complexes, similar to the aggregates of keratin filaments in Mallory bodies or the neurofilament aggregates in Lewy bodies. In all three instances, alpha-B crystallin may be associated with desmin. There are now increasing numbers of neuromuscular disorders in which abnormal amounts of desmin, some abnormally phosphorylated, feature prominently in muscle fibres. Several of these diseases, including spheroid body myopathy, granulo-filamentous body myopathy and the dystrophinopathies, are familial. Ultrastructural and immunohistochemical studies of desmin have considerably broadened our understanding of the pathology of the cytoskeleton in muscle fibers and in certain hereditary neuromuscular diseases.

Inclusions in familial cytoplasmic body myopathy are stained by anti-dystrophin antibodies

We report here for the first time positive anti-dystrophin labelling of inclusions in three cases belonging to the same family affected by familial cytoplasmic body myopathy (CBM). Inclusions are also stained, as reported previously, by anti-actin antibodies. The anti-desmin reaction was negative in the centre of cytoplasmic bodies (CB) but showed an enhancement of staining in the peripheral part. Abnormal sarcoplasmic staining of fibres with CB was also observed with that antibody. Anti-vimentin antibody labelling was negative. At present, the significance of this labelling by anti-dystrophin antibodies is unknown, but will open new fields for further investigations in an attempt to understand CB pathogenesis.

Experimental emetine myopathy: enzyme histochemical, electron microscopic, and immunomorphological studies

Ipecac, containing emetine hydrochloride, is used by patients with anorexia nervosa to induce vomiting. Its chronic usage may result in a myopathy and a cardiomyopathy, the former marked by cytoplasmic bodies. We studied myopathological changes after daily injections of female Wistar rats with emetine hydrochloride intraperitoneally for periods of 4, 5, 9, and 10 weeks. The extensor digitorum longus muscle and the soleus muscle showed core-like lesions, streaming of the z-discs, nemaline bodies, cytoplasmic bodies, and spheroid cytoplasmic bodies. Immunomorphological studies revealed increased amounts of desmin. During a period of repair, i.e., 2, 4, and 6 weeks after termination of emetine application, these myopathological alterations faded while proliferation of the T-tubular system, i.e., honeycomb structures, was more often prevalent. Pathological features completely disappeared between 6 and 12 weeks of recovery.

Desmin and vimentin as markers of regeneration in muscle diseases

Localization and distribution of desmin and vimentin have been studied in different neuromuscular disorders using monoclonal antibodies. We have demonstrated that vimentin, although virtually absent in normal human muscle fibers, is expressed in regenerating fibers in different neuromuscular disorders. Moreover, these fibers showed a strong positivity with desmin antibodies. In normal muscle fibers desmin is only localized at Z-line level. These results suggest that desmin and vimentin may be over-expressed during muscle regeneration processes, probably because of their importance in the structural organization of the sarcomere.

A mild juvenile variant of type IV glycogenosis

The mild juvenile form of type IV glycogenosis, confirmed by a profound deficiency of the brancher enzyme in tissue specimens is reported from three Turkish male siblings who, foremost, suffered from chronic progressive myopathy. Muscle fibers contained polyglucosan inclusions of typical fine structure i.e. a mixture of granular and filamentous glycogen. They reacted strongly for myophosphorylase, but were resistant to diastase. These inclusions were ubiquitinated and reacted with antibody KM-279 which previously has been shown to bind to Lafora bodies, corpora amylacea and polyglucosan material in hepatic and cardiac cells of type IV glycogenosis as well as polyglucosan body myopathy without brancher enzyme deficiency. Our findings confirm that although rate, a mild form of type IV glycogenosis is marked by polyglucosan inclusion not only in myofibers, but also in smooth muscle and sweat gland epithelial cells. This further implies that when polyglucosan inclusions are observed within myofibers it is mandatory to examine the muscle tissue for brancher enzyme activity since the brancher enzyme activities in circulating erythrocytes and leucocytes were normal in all three affected siblings and their parents. Therefore, it can be concluded that the patients reported on here represent a variant form of type IV glycogenosis, in which the defect is limited to muscle tissue. This further indicates that there are several different types of type IV glycogenosis with variable clinical manifestations.

Immunohistochemical investigations to demonstrate vital direct traumatic damage of skeletal muscle

The muscle proteins actin, myosin, desmin and myoglobin were investigated in traumatically damaged human and animal skeletal muscle using an immunohistochemical PAP-method. A depletion of all the proteins investigated was observed in muscle fibres damaged in the antemortem period. The antigens could however also be demonstrated in the otherwise empty sarcolemma, the discoid disintegration zones of the fibres and between the fibres. The depletion begins immediately after the trauma and myoglobin is the first to be affected. No such changes could be observed after post mortem muscle damage. The antigens could be demonstrated until 72 hours post mortem. The demonstration of protein depletion is an important addition to the light microscopical findings in vital muscle alterations.

Neuromyopathy and restrictive cardiomyopathy with accumulation of intermediate filaments: a clinical, morphological and biochemical study

The clinical, morphological and biochemical findings of a sporadic case, showing accumulation of desmin-type intermediate filaments in skeletal muscle and myocardium are described. Desmin storage was demonstrated by immunofluorescence, sodium dodecyl sulfate gel electrophoresis and two-dimensional gel electrophoresis. These findings are in agreement with those of Rappaport et al. (FEBS lett. 231:421-425, 1989). A sensory-motor polyneuropathy was established by electrophysiological studies and, ultrastructurally, intramuscular nerves showed accumulation of neurofilaments and neurotubules with formation of axonal spheroids. These findings are discussed considering all previous reports with related conditions.

Vimentin/desmin immunoreactivity of myofibres in developmental myopathies

Immunoreactivity for the intermediate filament proteins vimentin and desmin was studied in muscle biopsies of 33 children with neuromuscular diseases and in postmortem muscle of 15 fetuses and neonates at 8-42 weeks gestation. Fetal myotubes exhibited strong reactions for vimentin and desmin; reactivity was still present, though weaker, by 31 weeks and was no longer demonstrable at term. In X-linked myotubular myopathy (5 cases) myofibres showed strong reactivity for both vimentin and desmin; in myotonic dystrophy desmin but not vimentin had strong reactivity in myofibres of neonates and children. A similar but much weaker pattern of desmin reactivity was seen in nemaline rod disease and in congenital muscle fibre-type disproportion. The small myofibres in spinal muscular atrophy were reactive for both vimentin and desmin, as were regenerating myofibres in Duchenne muscular dystrophy and dermatomyositis. Acridine orange fluorochrome distinguished vimentin/desmin-reactive myofibres that were regenerating from those of developmental myopathies because the RNA fluorescence was strong in regenerating myofibres and in fetal myotubes, but was absent from myofibres in developmental disorders of muscle. A failure to regress of fetal cytoskeletal proteins may contribute to the apparent arrest in morphogenesis of myofibres. These stains are useful in studying the muscle biopsies of children with developmental myopathies because they demonstrate an aspect of muscle maturation not detected by standard histochemical methods.

Primary lipid cardiomyopathy

In this communication, we describe an isolated, apparently congenital cardiomyopathy (CMP) characterized by the accumulation of stainable lipid in mitochondria of cardiomyocytes. This lesion, which we term primary lipid cardiomyopathy, has not been reported so far. The structural alteration was associated with progressive heart failure, leading to death at the age of 3 years, and with massive hypertrophy of myocardium. Lipid storage in heart muscle cells resulted in an impressive yellow to orange color of the myocardium. We suggest that this type of primary CMP may represent a new member within the group of mitochondrial CMPs. Possible pathogenic mechanisms are discussed.

Desmin and actin associated with cytoplasmic bodies in skeletal muscle fibers: immunocytochemical and fine structural studies, with a note on unusual 18- to 20-nm filaments

In a fine structural and immunocytochemical study, the latter performed on semithin sections of epoxy resin embedded skeletal muscle fibers, three types of cytoplasmic bodies were identified in a case of cytoplasmic body myopathy: (1) The first type, the classical type, showed a central core and a light halo with radiating actin filaments at the periphery. (2) The second type, the spheroid body was characterized by irregularly arranged granular masses associated with intermediate filaments. Desmin immunoreactivity occurred in the central and peripheral parts, where filaments of intermediate size were visualized by electron microscopy. Desmin immunoreactivity was noted also at the Z-bands of striated annulets, within areas of disordered myofibrils, such as sarcoplasmic masses, and in atrophic muscle fibers. (3) The third type of the cytoplasmic body was composed mainly of large masses of uneven granularity and electron density. The center of this type reacted to anti-actin antibody suggesting that the 5- to 6-nm filaments, which ultrastructurally proved to be a major component, were of the actin type. By contrast, neither intermediate filaments nor actin microfilaments were found by electron microscopy in cytoplasmic bodies in a second case where no immunoreaction to desmin or actin occurred. Anti-vimentin antibody stained only the cytoplasm of endomysial cells, but not the inclusion bodies. Some other, unusual inclusions with 18- to 20-nm tubulo-filamentous structures have to be distinguished from the various types of filaments in cytoplasmic bodies. It is concluded, that pleomorphism and heterogeneity of "cytoplasmic bodies" have to be taken into consideration when classifying cytoplasmic body myopathies.

Myotubular myopathy: arrest of morphogenesis of myofibres associated with persistence of fetal vimentin and desmin. Four cases compared with fetal and neonatal muscle

Vastus lateralis muscle biopsies of four unrelated male neonates showing myotubular (i.e. centronuclear) myopathy (MM) were compared with muscle from four human fetuses in the myotubular stage of development, a 31 week preterm infant and four term neonates. The perimysium, blood vessels, spindles, myelinated intramuscular nerves, and motor end-plates in MM are as well developed as in term neonatal muscle. The cytoarchitecture of myofibres in MM is more mature than that of fetal myotubes in the spacing of central nuclei, Z-band registry, development of the sarcotubular system, and in the condensation of nuclear chromatin and nucleoli. Triads in MM may retain an immature oblique or longitudinal orientation. Myofibrillar ATPase shows normal differentiation of fibre types, consistent with normal innervation. Spinal motor neurons are normal in number and in RNA fluorescence. Immunoreactivity for vimentin and desmin in myofibres of MM is uniformly strong, as in fetal myotubes and unlike mature neonatal muscle. Maternal muscle biopsies of two cases also showed scattered small centronuclear myofibres reactive for vimentin and desmin. The arrest in morphogenesis of fibre architecture in MM is not a general arrest in muscle development. Persistence of fetal cytoskeletal proteins that preserve the immature central positions of nuclei and mitochondria may be important in pathogenesis. Vimentin/desmin studies of the infant and maternal muscle biopsies are useful in establishing the diagnosis.

Myopathy with respiratory failure and typical myofibrillar lesions

16 patients representing 7 different pedigrees exhibited an unusual, adult onset limb-girdle myopathy with typical clinical hallmarks. In a majority of cases there was evidence of an autosomal dominant inheritance. A prominent early finding in all cases was respiratory muscle weakness, and in many of these an acute respiratory incapacity was the reason for the first neurological examination. Neck flexor and sometimes foot extensor weakness were other early symptoms. The clinical picture seems to be at variance with that of the more well known hereditary myopathies. Electrophysiological analysis confirmed a myopathy and serum muscle enzyme concentrations were normal or slightly elevated. Muscle biopsy findings revealed myofibrillar changes which, at the light microscopy level, included plaques that stained strongly with rhodamine-conjugated phalloidin, a specific marker for F-actin. At the ultrastructural level, these plaques were observed to be composed of moderately dense, thin filaments and were related to splitting of Z-discs or formed extensions from Z-discs. We believe that the muscle biopsy changes revealed by cytochemical and ultrastructural observations indicate defective myofibrillogenesis, and the possibility of defective actin polymerization is discussed. A conclusive answer requires further immunocytochemical and immunoelectrophoretic studies and possibly the application of molecular genetics.

Involvement of respiratory muscles in cytoplasmic body myopathy--a pathology study

A muscle biopsy and autopsy study of a child who died at 14 months of respiratory failure is described. A diagnosis of infantile cytoplasmic body myopathy was made due to the high percentage of cytoplasmic bodies (CBs), particularly in respiratory muscles. No pathological abnormalities were found in the central nervous system, peripheral nerves or visceral organs. Immunohistochemical studies suggested that the central core of CBs was stained for fibrillary actin, being surrounded by a positive signal for desmin. A differential diagnosis as to other conditions involving proliferation of CBs is discussed.

Myopathy associated with desmin type intermediate filaments. An immunoelectron microscopic study

The muscle biopsy performed in a 58-year-old woman with a myopathy involving pelvic girdle and lower limbs displayed unusual intermediate filament aggregates by light and electron microscopy. No cardiac involvement was detected. The filamentous aggregates selective for type 1 fibers were found in subsarcolemmal and intermyofibrillar areas closely related to Z bands. Immunohistochemical study by light and electron microscopy using polyclonal and monoclonal antibodies and avidin-biotin peroxidase method revealed that aggregates consisted of desmin filaments. Desmin positive material was unstained with vimentine antibodies.