BAG3 myofibrillar myopathy presenting with cardiomyopathy

Animal Models of Congenital Cardiomyopathies Associated With Mutations in Z-Line Proteins

The cardiac Z-line at the boundary between sarcomeres is a multiprotein complex connecting the contractile apparatus with the cytoskeleton and the extracellular matrix. The Z-line is important for efficient force generation and transmission as well as the maintenance of structural stability and integrity. Furthermore, it is a nodal point for intracellular signaling, in particular mechanosensing and mechanotransduction. Mutations in various genes encoding Z-line proteins have been associated with different cardiomyopathies, including dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, restrictive cardiomyopathy, and left ventricular noncompaction, and mutations even within the same gene can cause widely different pathologies. Animal models have contributed to a great advancement in the understanding of the physiological function of Z-line proteins and the pathways leading from mutations in Z-line proteins to cardiomyopathy, although genotype-phenotype prediction remains a great challenge. This review presents an overview of the currently available animal models for Z-line and Z-line associated proteins involved in human cardiomyopathies with special emphasis on knock-in and transgenic mouse models recapitulating the clinical phenotypes of human cardiomyopathy patients carrying mutations in Z-line proteins. Pros and cons of mouse models will be discussed and a future outlook will be given. J. Cell. Physiol. 232: 38-52, 2017. © 2016 Wiley Periodicals, Inc.

The Relationship Between Child Anxiety Related Disorders and Primary Nocturnal Enuresis

BACKGROUND

Nocturnal enuresis, often called bedwetting or sleep wetting, is a common problem in children after the age of five and may lead to symptoms such as infection, incontinence and frequent urination. This problem refers to a state in which children after the age of five have no control of their urine for six continuous months and it cannot be attributed to any organic factors or drug use.

OBJECTIVES

In this study we aimed to study generalized anxiety disorder as one of the possible causes of primary nocturnal enuresis.

MATERIALS AND METHODS

In this case-control study 180 children with primary nocturnal enuresis and same number of healthy children with a mean age of 7 - 17 years old with the same demographic characteristics were selected. The study took place at Amir Kabir hospital of Arak, Iran during year 2014. After collecting the information, diagnosis was verified based on the diagnostic and statistical manual of mental disorders (DSM) IV-TR criteria. Results were analyzed using the SPSS software (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, version 20.0. Armonk, NY: IBM Corp.).

RESULTS

Frequency of generalized anxiety disorder, panic disorder, school phobia, social anxiety, separation anxiety, history of anxiety in mother, history of primary nocturnal enuresis in parent's family and body mass index had a significant difference between the two groups (P = 0.005).

CONCLUSIONS

With the results obtained from this study we could say that there was a clear significant difference between the two control and patient groups for all subgroups of anxiety disorders such as generalized anxiety disorder and their relationship with primary nocturnal enuresis. Given the higher prevalence of generalized anxiety disorder, panic disorder, school phobia, social anxiety, separation anxiety and comparison with healthy children, it is recommended for all children with primary nocturnal enuresis to be investigated and treated for generalized anxiety disorder.

Breaking BAG: The Co-Chaperone BAG3 in Health and Disease

Human BAG (Bcl-2-associated athanogene) proteins form a family of antiapoptotic proteins that currently consists of six members (BAG1-6) all sharing the BAG protein domain from which the name arises. Via this domain, BAG proteins bind to the heat shock protein 70 (Hsp70), thereby acting as a co-chaperone regulating the activity of Hsp70. In addition to their antiapoptotic activity, all human BAG proteins have distinct functions in health and disease, and BAG3 in particular is the focus of many investigations. BAG3 has a modular protein domain composition offering the possibility for manifold interactions with other proteins. Various BAG3 functions are implicated in disorders including cancer, myopathies, and neurodegeneration. The discovery of its role in selective autophagy and the description of BAG3-mediated selective macroautophagy as an adaptive mechanism to maintain cellular homeostasis, under stress as well as during aging, make BAG3 a highly interesting target for future pharmacological interventions.

Hearing loss, coloboma and left ventricular enlargement in a boy with an interstitial 10q26 deletion

Distal deletion of the long arm of chromosome 10 with breakpoints mapped at 10q26 is a well-recognized contiguous genomic disorder. A wide spectrum of clinical findings is seen in affected individuals and the common clinical features include craniofacial dysmorphia, developmental delay, intellectual disability, hypotonia, cardiovascular defects, and urogenital malformations. We report herein on a male patient with a 5.5 Mb interstitial deletion of 10q26.11q2613 and compare his clinical presentation to previously reported cases. Apart from characteristic phenotypes seen in 10q26 deletion syndrome, he presents with colobomas and left ventricle enlargement. These are cardiovascular and ophthalmological findings that have not been described in prior cases. © 2016 Wiley Periodicals, Inc.

NFκB is a central regulator of protein quality control in response to protein aggregation stresses via autophagy modulation

NFκB is a master regulator of protein quality control. It helps the cells to survive proteotoxicity by modulating autophagy via up-regulation of BAG3 and HspB8 expression, a molecular mechanism relevant to protein conformational diseases.

During cell life, proteins often misfold, depending on particular mutations or environmental changes, which may lead to protein aggregates that are toxic for the cell. Such protein aggregates are the root cause of numerous diseases called “protein conformational diseases,” such as myofibrillar myopathy and familial amyotrophic lateral sclerosis. To fight against aggregates, cells are equipped with protein quality control mechanisms. Here we report that NFκB transcription factor is activated by misincorporation of amino acid analogues into proteins, inhibition of proteasomal activity, expression of the R120G mutated form of HspB5 (associated with myofibrillar myopathy), or expression of the G985R and G93A mutated forms of superoxide dismutase 1 (linked to familial amyotrophic lateral sclerosis). This noncanonical stimulation of NFκB triggers the up-regulation of BAG3 and HspB8 expression, two activators of selective autophagy, which relocalize to protein aggregates. Then NFκB-dependent autophagy allows the clearance of protein aggregates. Thus NFκB appears as a central and major regulator of protein aggregate clearance by modulating autophagic activity. In this context, the pharmacological stimulation of this quality control pathway might represent a valuable strategy for therapies against protein conformational diseases.

Myosin heavy chain is stabilized by BCL-2 interacting cell death suppressor (BIS) in skeletal muscle

BCL-2 interacting cell death suppressor (BIS), which is ubiquitously expressed, has important roles in various cellular processes, such as apoptosis, the cellular stress response, migration and invasion and protein quality control. In particular, BIS is highly expressed in skeletal and cardiac muscles, and BIS gene mutations result in human myopathy. In this study, we show that mRNA and protein levels of BIS were markedly increased during skeletal myogenesis in C2C12 cells and mouse satellite cells. BIS knockdown did not prevent the early stage of skeletal myogenesis, but did induce muscle atrophy and a decrease in the diameter of myotubes. BIS knockdown significantly suppressed the expression level of myosin heavy chain (MyHC) without changing the expression levels of myogenic marker proteins, such as Mgn, Cav-3 and MG53. In addition, BIS endogenously interacted with MyHC, and BIS knockdown induced MyHC ubiquitination and degradation. From these data, we conclude that molecular association of MyHC and BIS is necessary for MyHC stabilization in skeletal muscle.

Heart Disease in Disorders of Muscle, Neuromuscular Transmission, and the Nerves

Little is known regarding cardiac involvement (CI) by neuromuscular disorders (NMDs). The purpose of this review is to summarise and discuss the major findings concerning the types, frequency, and severity of cardiac disorders in NMDs as well as their diagnosis, treatment, and overall outcome. CI in NMDs is characterized by pathologic involvement of the myocardium or cardiac conduction system. Less commonly, additional critical anatomic structures, such as the valves, coronary arteries, endocardium, pericardium, and even the aortic root may be involved. Involvement of the myocardium manifests most frequently as hypertrophic or dilated cardiomyopathy and less frequently as restrictive cardiomyopathy, non-compaction, arrhythmogenic right-ventricular dysplasia, or Takotsubo-syndrome. Cardiac conduction defects and supraventricular and ventricular arrhythmias are common cardiac manifestations of NMDs. Arrhythmias may evolve into life-threatening ventricular tachycardias, asystole, or even sudden cardiac death. CI is common and carries great prognostic significance on the outcome of dystrophinopathies, laminopathies, desminopathies, nemaline myopathy, myotonias, metabolic myopathies, Danon disease, and Barth-syndrome. The diagnosis and treatment of CI in NMDs follows established guidelines for the management of cardiac disease, but cardiotoxic medications should be avoided. CI in NMDs is relatively common and requires complete work-up following the establishment of a neurological diagnosis. Appropriate cardiac treatment significantly improves the overall long-term outcome of NMDs.

Mutations in FLNC are Associated with Familial Restrictive Cardiomyopathy

Individuals affected by restrictive cardiomyopathy (RCM) often develop heart failure at young ages resulting in early heart transplantation. Familial forms are mainly caused by mutations in sarcomere proteins and demonstrate a common genetic etiology with other inherited cardiomyopathies. Using next-generation sequencing, we identified two novel missense variants (p.S1624L; p.I2160F) in filamin-C (FLNC), an actin-cross-linking protein mainly expressed in heart and skeletal muscle, segregating in two families with autosomal-dominant RCM. Affected individuals presented with heart failure due to severe diastolic dysfunction requiring heart transplantation in some cases. Histopathology of heart tissue from patients of both families showed cytoplasmic inclusions suggesting protein aggregates, which were filamin-C specific for the p.S1624L by immunohistochemistry. Cytoplasmic aggregates were also observed in transfected myoblast cell lines expressing this mutant filamin-C indicating further evidence for its pathogenicity. Thus, FLNC is a disease gene for autosomal-dominant RCM and broadens the phenotype spectrum of filaminopathies.

BAG3-related myopathy, polyneuropathy and cardiomyopathy with long QT syndrome

BAG3 belongs to BAG family of molecular chaperone regulators interacting with HSP70 and anti-apoptotic protein Bcl-2. It is ubiquitously expressed with strong expression in skeletal and cardiac muscle, and is involved in a panoply of cellular processes. Mutations in BAG3 and aberrations in its expression cause fulminant myopathies, presenting with progressive limb and axial muscle weakness, and respiratory insufficiency and neuropathy. Herein, we report a sporadic case of a 15-years old girl with symptoms of myopathy, demyelinating polyneuropathy and asymptomatic long QT syndrome. Genetic testing demonstrated heterozygous mutation Pro209Leu (c.626C > T) in exon 3 of BAG3 gene causing severe myopathy and neuropathy, often associated with restrictive cardiomyopathy. We did not find a mutation in any known LQT syndrome genes. Analysis of muscle biopsy revealed profound disintegration of Z-discs with extensive accumulation of granular debris and large inclusions within fibers. We demonstrated profound alterations in BAG3 distribution as the protein localized to long filamentous structures present across the fibers that were positively stained not only for α-actinin but also for desmin and filamin indicating that those disintegrated Z-disc regions contained also other sarcomeric proteins. The mutation caused a decrease in the content of BAG3 and HSP70, and also of α-actinin desmin, filamin and fast myosin heavy chain, confirming its severe effect on the muscle fiber morphology and thus function. We provide further evidence that BAG3 is associated with Z-disc maintenance, and the Pro209Leu mutation may occur worldwide. We also provide a summary of cases associated with this mutation reported so far.