A mutation in the alpha tropomyosin gene TPM3 associated with autosomal dominant nemaline myopathy NEM1
ABSTRACT Nemaline myopathies are diseases characterized by the presence in muscle fibres of pathognomonic rod bodies. These are composed largely of alpha-actinin and actin. We have identified a missense mutation in the alpha-tropomyosin gene, TPM3, which segregates completely with the disease in a family whose autosomal dominant nemaline myopathy we had previously localized to chromosome 1p13-q25. The mutation substitutes an arginine residue for a highly conserved methionine in a putative actin-binding site near the N terminus of the alpha-tropomyosin. The mutation may strengthen tropomyosin - actin binding, leading to rod body formation, by adding a further basic residue to the postulated actin-binding motif.
Full-textDOI: · Available from: Peter Blumbergs, Jun 26, 2014
- SourceAvailable from: Amitabh Sharma
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- "In contrast to these edgetic mutations, the quasi-WT mutation M9R causes a different disease, nemaline myopathy. M9R might affect actin binding, thus leading to the formation of abnormal nemaline rods (Laing et al., 1995). The possible disease relevance of our approach was further illustrated by edgetic mutations in the gene EFHC1, mutations in which can cause epilepsy. "
ABSTRACT: How disease-associated mutations impair protein activities in the context of biological networks remains mostly undetermined. Although a few renowned alleles are well characterized, functional information is missing for over 100,000 disease-associated variants. Here we functionally profile several thousand missense mutations across a spectrum of Mendelian disorders using various interaction assays. The majority of disease-associated alleles exhibit wild-type chaperone binding profiles, suggesting they preserve protein folding or stability. While common variants from healthy individuals rarely affect interactions, two-thirds of disease-associated alleles perturb protein-protein interactions, with half corresponding to "edgetic" alleles affecting only a subset of interactions while leaving most other interactions unperturbed. With transcription factors, many alleles that leave protein-protein interactions intact affect DNA binding. Different mutations in the same gene leading to different interaction profiles often result in distinct disease phenotypes. Thus disease-associated alleles that perturb distinct protein activities rather than grossly affecting folding and stability are relatively widespread. Copyright © 2015 Elsevier Inc. All rights reserved.Cell 04/2015; 161(3):647-660. DOI:10.1016/j.cell.2015.04.013 · 33.12 Impact Factor
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- "However, there does not seem to be a simple unifying mechanism associated with these mutations. The most widely studied tropomyosin mutation is the slow a-tropomyosin (a-Tm, TPM3) p.Met9Arg substitution (Laing et al., 1995; Corbett et al., 2001, 2005). Expression of a-Tm "
ABSTRACT: The congenital myopathies are a diverse group of genetic skeletal muscle diseases, which typically present at birth or in early infancy. There are multiple modes of inheritance and degrees of severity (ranging from foetal akinesia, through lethality in the newborn period to milder early and later onset cases). Classically, the congenital myopathies are defined by skeletal muscle dysfunction and a non-dystrophic muscle biopsy with the presence of one or more characteristic histological features. However, mutations in multiple different genes can cause the same pathology and mutations in the same gene can cause multiple different pathologies. This is becoming ever more apparent now that, with the increasing use of next generation sequencing, a genetic diagnosis is achieved for a greater number of patients. Thus, considerable genetic and pathological overlap is emerging, blurring the classically established boundaries. At the same time, some of the pathophysiological concepts underlying the congenital myopathies are moving into sharper focus. Here we explore whether our emerging understanding of disease pathogenesis and underlying pathophysiological mechanisms, rather than a strictly gene-centric approach, will provide grounds for a different and perhaps complementary grouping of the congenital myopathies, that at the same time could help instil the development of shared potential therapeutic approaches. Stemming from recent advances in the congenital myopathy field, five key pathophysiology themes have emerged: defects in (i) sarcolemmal and intracellular membrane remodelling and excitation-contraction coupling; (ii) mitochondrial distribution and function; (iii) myofibrillar force generation; (iv) atrophy; and (v) autophagy. Based on numerous emerging lines of evidence from recent studies in cell lines and patient tissues, mouse models and zebrafish highlighting these unifying pathophysiological themes, here we review the congenital myopathies in relation to these emerging pathophysiological concepts, highlighting both areas of overlap between established entities, as well as areas of distinction within single gene disorders. Published by Oxford University Press on behalf of the Guarantors of Brain 2014. This work is written by US Government employees and is in the public domain in the US.Brain 12/2014; 138(2). DOI:10.1093/brain/awu368 · 10.23 Impact Factor
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- "The essential roles of sarcomeric proteins have been highlighted by identification of mutations in their genes associated with various diseases. This includes mutations in genes encoding β-TM and γ-TM isoforms (TPM2 and TPM3) in association with congenital myopathies with a range of clinical and morphological phenotypes [12,13,35-42]. In addition, mutations in TPM2, TNNI2, MYH3, MYH8 and MYBPC1 have recently been identified to cause the DA syndromes, characterized by congenital contractures [12,15]. "
ABSTRACT: Background The formation of contractile myofibrils requires the stepwise onset of expression of muscle specific proteins. It is likely that elucidation of the expression patterns of muscle-specific sarcomeric proteins is important to understand muscle disorders originating from defects in contractile sarcomeric proteins. Methods We investigated the expression profile of a panel of sarcomeric components with a focus on proteins associated with a group of congenital disorders. The analyses were performed in cultured human skeletal muscle cells during myoblast proliferation and myotube development. Results Our culture technique resulted in the development of striated myotubes and the expression of adult isoforms of the sarcomeric proteins, such as fast TnI, fast TnT, adult fast and slow MyHC isoforms and predominantly skeletal muscle rather than cardiac actin. Many proteins involved in muscle diseases, such as beta tropomyosin, slow TnI, slow MyBPC and cardiac TnI were readily detected in the initial stages of muscle cell differentiation, suggesting the possibility of an early role for these proteins as constituent of the developing contractile apparatus during myofibrillogenesis. This suggests that in disease conditions the mechanisms of pathogenesis for each of the mutated sarcomeric proteins might be reflected by altered expression patterns, and disturbed assembly of cytoskeletal, myofibrillar structures and muscle development. Conclusions In conclusion, we here confirm that cell cultures of human skeletal muscle are an appropriate tool to study developmental stages of myofibrillogenesis. The expression of several disease-associated proteins indicates that they might be a useful model system for studying the pathogenesis of muscle diseases caused by defects in specific sarcomeric constituents.BMC Musculoskeletal Disorders 12/2012; 13(1):262. DOI:10.1186/1471-2474-13-262 · 1.90 Impact Factor