Familial cardioneuromyopathy with hyaline masses and nemaline rods: a novel phenotype

NEM6, KBTBD13-Related Congenital Myopathy: Myopathological Analysis in 18 Dutch Patients Reveals Ring Rods Fibers, Cores, Nuclear Clumps, and Granulo-Filamentous Protein Material

Nemaline myopathy type 6 (NEM6), KBTBD13-related congenital myopathy is caused by mutated KBTBD13 protein that interacts improperly with thin filaments/actin, provoking impaired muscle-relaxation kinetics. We describe muscle morphology in 18 Dutch NEM6 patients and correlate it with clinical phenotype and pathophysiological mechanisms. Rods were found in in 85% of biopsies by light microscopy, and 89% by electron microscopy. A peculiar ring disposition of rods resulting in ring-rods fiber was observed. Cores were found in 79% of NEM6 biopsies by light microscopy, and 83% by electron microscopy. Electron microscopy also disclosed granulofilamentous protein material in 9 biopsies. Fiber type 1 predominance and prominent nuclear internalization were found. Rods were immunoreactive for α-actinin and myotilin. Areas surrounding the rods showed titin overexpression suggesting derangement of the surrounding sarcomeres. NEM6 myopathology hallmarks are prominent cores, rods including ring-rods fibers, nuclear clumps, and granulofilamentous protein material. This material might represent the histopathologic epiphenomenon of altered interaction between mutated KBTBD13 protein and thin filaments. We claim to classify KBTBD13-related congenital myopathy as rod-core myopathy.

Review of Cardiac Disease in Nemaline Myopathy

OBJECTIVES

Little is known about the type, frequency, severity, treatment, and outcome of cardiac disease in nemaline myopathy. This review summarizes and discusses findings concerning the type, prevalence, diagnosis, treatment, and outcome of cardiac involvement in nemaline myopathy.

METHODS

Review of publications about nemaline myopathy and cardiac disease.

RESULTS

Altogether, 35 patients with nemaline myopathy with cardiac disease were identified. Age at presentation ranged from 0 to 62 years. In 30 individuals whose gender was described, 22 were male and eight were female. Onset was congenital in 16 patients, infantile in five, and adult in four. Nine patients presented with dilated cardiomyopathy, six with hypertrophic cardiomyopathy, and one with nonspecific cardiomyopathy. Among those with cardiomyopathy, four developed heart failure. One patient experienced sudden cardiac death. A ventricular septal defect was described in two patients. Cardiac treatment included drugs for heart failure (eight patients), implantable cardioverter-defibrillator implantation (one patient), and heart transplant (three patients). Four patients received noninvasive positive-pressure ventilation and two continuous positive-pressure ventilation. The outcome was fatal in 11 patients.

CONCLUSIONS

Cardiac disease in nemaline myopathy manifests as cardiomyopathy leading to heart failure. If respiratory muscles are affected, the right side of the heart may be secondarily involved. Early detection of cardiac involvement is essential since effective treatment for cardiac disease in nemaline myopathy may be available.

Autoantibody profiles in two patients with non-autoimmune muscle disease implicate a role for gliadin autoreactivity

The objective of this case study was to characterize autoreactivity in two patients with non-autoimmune forms of muscle disease who had positivity for antinuclear antibodies (ANA) and Ro (SSA) autoantibodies. Serum samples from these two patients were applied to an autoantigen protein array with more than 70 specificities and were compared to samples from healthy controls and patients with systemic lupus erythematosus. Both myopathy patients had high levels of gliadin autoreactivity in serum and one patient had an overall autoantibody profile with lupus-like features. The findings suggest that some disorders of muscle that are considered non-autoimmune, may in fact have autoimmune features. Further examination of the role of subclinical gluten autoreactivity in the pathogenesis of myopathy syndromes has the potential to suggest improved approaches to diagnosis and treatment of these conditions.

Actinopathies and myosinopathies

The currently recognized two forms of "anabolic" protein aggregate myopathies, that is, defects in development, maturation and final formation of respective actin and myosin filaments encompass actinopathies and myosinopathies. The former are marked by mutations in the ACTA1 gene, largely of the de novo type. Aggregates of actin filaments are deposited within muscle fibers. Early clinical onset is often congenital; most patients run a rapidly progressive course and die during their first 2 years of life. Myosinopathies or myosin storage myopathies also commence in childhood, but show a much more protracted course owing to mutations in the myosin heavy chain gene MYH7. Protein aggregation consists of granular material in muscle fibers and few, if any, filaments.

Genomic expression patterns of cardiac tissues from dogs with dilated cardiomyopathy

OBJECTIVE

To evaluate global genome expression patterns of left ventricular tissues from dogs with dilated cardiomyopathy (DCM).

SAMPLE POPULATION

Tissues obtained from the left ventricle of 2 Doberman Pinschers with end-stage DCM and 5 healthy control dogs.

PROCEDURE

Transcriptional activities of 23,851 canine DNA sequences were determined by use of an oligonucleotide microarray. Genome expression patterns of DCM tissue were evaluated by measuring the relative amount of complementary RNA hybridization to the microarray probes and comparing it with gene expression for tissues from 5 healthy control dogs.

RESULTS

478 transcripts were differentially expressed (> or = 2.5-fold change). In DCM tissue, expression of 173 transcripts was upregulated and expression of 305 transcripts was downregulated, compared with expression for control tissues. Of the 478 transcripts, 167 genes could be specifically identified. These genes were grouped into 1 of 8 categories on the basis of their primary physiologic function. Grouping revealed that pathways involving cellular energy production, signaling and communication, and cell structure were generally downregulated, whereas pathways involving cellular defense and stress responses were upregulated. Many previously unreported genes that may contribute to the pathophysiologic aspects of heart disease were identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Evaluation of global expression patterns provides a molecular portrait of heart failure, yields insights into the pathophysiologic aspects of DCM, and identifies intriguing genes and pathways for further study.

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.

Mimicking phosphorylation of the small heat-shock protein alphaB-crystallin recruits the F-box protein FBX4 to nuclear SC35 speckles

The mammalian small heat shock protein alphaB-crystallin can be phosphorylated at three different sites, Ser19, Ser45 and Ser59. We compared the intracellular distribution of wild-type, nonphosphorylatable and all possible pseudophosphorylation mutants of alphaB-crystallin by immunoblot and immunocytochemical analyses of stable and transiently transfected cells. We observed that pseudophosphorylation at two (especially S19D/S45D) or all three (S19D/S45D/S59D) sites induced the partial translocation of alphaB-crystallin from the detergent-soluble to the detergent-insoluble fraction. Double immunofluorescence studies showed that the pseudophosphorylation mutants localized in nuclear speckles containing the splicing factor SC35. The alphaB-crystallin mutants in these speckles were resistant to mild detergent treatment, and also to DNase I or RNase A digestion, indicating a stable interaction with one or more speckle proteins, not dependent on intact DNA or RNA. We further found that FBX4, an adaptor protein of the ubiquitin-protein isopeptide ligase SKP1/CUL1/F-box known to interact with pseudophosphorylated alphaB-crystallin, was also recruited to SC35 speckles when cotransfected with the pseudophosphorylation mutants. Because SC35 speckles also react with an antibody against alphaB-crystallin endogenously phosphorylated at Ser45, our findings suggest that alphaB-crystallin has a phosphorylation-dependent role in the ubiquitination of a component of SC35 speckles.

Identification of a locus for an autosomal recessive hyaline body myopathy at chromosome 3p22.2–p21.32

Hyaline body myopathy is a rare congenital disease with distinctive histopathological features. We performed homozygosity mapping in a family with two affected sibs and identified a gene locus with a maximum homozygosity region of 5.35 centi Morgans or 5.59 Megabases at chromosome 3p22.2-p21.32. The best candidate responsible for the disease is a novel gene that exhibits homology to the myosin heavy chain.

Congenital myopathies and related disorders

PURPOSE OF REVIEW

Considerable progress has been made in molecular genetic research and in identifying the underlying pathogenesis of congenital myopathies, with implications for genetic counseling. Therefore an overview of such advances in the last two years is most timely and relevant for a more precise delineation of these disorders.

RECENT FINDINGS

New mutations have been described on the ryanodine receptor gene, including the carboxyl-terminus region, and experimental models developed to explain their role in central core disease. Phenotype-genotype correlations for nemaline myopathy have improved our understanding of those related to gene mutations. In multi-minicore disease, collaborative studies support genetic heterogeneity and autosomal-recessive inheritance. Research on X-linked myotubular myopathies has revealed a high percentage of mothers of sporadic cases as carriers. Although not initially included within the congenital myopathies, desmin-related or myofibrillar myopathies are described here because they are closely related to other congenital myopathies with intracytoplasmic inclusions. Western blot for myotubularin and desmin has been proposed as a useful diagnostic test for both X-linked myotubular myopathy and desmin-related myopathy, and in-vitro and mouse models for the latter have provided insights into its pathogenesis. Several entities still await genetic characterization. Here we focus on clinical features, inheritance, and molecular genetics.

SUMMARY

Advances in immunohistochemistry and molecular genetics in congenital muscular dystrophies have enriched our knowledge of this heterogeneous group of disorders, leading to more accurate classification and differentiation between the various congenital myopathies.