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Morais J, Oliveira AA, Pires O, Burmester I, Regadas MJ, Gouveia P. Titinopathy, an atypical respiratory failure. BMJ Case Rep 2020; 13:e235378. [PMID: 32912888 PMCID: PMC7482489 DOI: 10.1136/bcr-2020-235378] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2020] [Indexed: 01/12/2023] Open
Abstract
Hereditary myopathy with early respiratory failure is a neuromuscular disease with an autosomal dominant inheritance pattern. Clinical presentation is characterised by proximal and distal muscle weakness, exertional dyspnoea and generalised fatigue. There is no disease-modifying therapy and the prognosis is unknown. Herein we present a case of a 40-year-old woman with long-standing asthenia and apathy and, more recently, daytime sleepiness, dyspnoea and difficulty in walking. A hypercapnic respiratory failure with severe acidemia was identified. The muscle biopsy showed the presence of cytoplasmatic bodies and rimmed vacuoles, suggestive of a hereditary myopathy with early respiratory failure disease. The genetic study confirmed this diagnosis identifying a heterozygous mutation on c.95134T>C (p.Cys31712Arg) in exon 343 in the titin gene. The patient was discharged home under supportive treatment with non-invasive ventilation.
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Affiliation(s)
- Joana Morais
- Internal Medicine, Hospital de Braga, Braga, Portugal
| | | | - Olga Pires
- Internal Medicine, Hospital de Braga, Braga, Portugal
| | | | | | - Paulo Gouveia
- Internal Medicine, Hospital de Braga, Braga, Portugal
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Tasca G, Udd B. Hereditary myopathy with early respiratory failure (HMERF): Still rare, but common enough. Neuromuscul Disord 2018; 28:268-276. [DOI: 10.1016/j.nmd.2017.12.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 11/04/2017] [Accepted: 12/03/2017] [Indexed: 01/04/2023]
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Genetic epidemiology of titin-truncating variants in the etiology of dilated cardiomyopathy. Biophys Rev 2017; 9:207-223. [PMID: 28510119 PMCID: PMC5498329 DOI: 10.1007/s12551-017-0265-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/10/2017] [Indexed: 02/07/2023] Open
Abstract
Heart failure (HF) is a complex clinical syndrome defined by the inability of the heart to pump enough blood to meet the body's metabolic demands. Major causes of HF are cardiomyopathies (diseases of the myocardium associated with mechanical and/or electrical dysfunction), among which the most common form is dilated cardiomyopathy (DCM). DCM is defined by ventricular chamber enlargement and systolic dysfunction with normal left ventricular wall thickness, which leads to progressive HF. Over 60 genes are linked to the etiology of DCM. Titin (TTN) is the largest known protein in biology, spanning half the cardiac sarcomere and, as such, is a basic structural and functional unit of striated muscles. It is essential for heart development as well as mechanical and regulatory functions of the sarcomere. Next-generation sequencing (NGS) in clinical DCM cohorts implicated truncating variants in titin (TTNtv) as major disease alleles, accounting for more than 25% of familial DCM cases, but these variants have also been identified in 2-3% of the general population, where these TTNtv blur diagnostic and clinical utility. Taking into account the published TTNtv and their association to DCM, it becomes clear that TTNtv harm the heart with position-dependent occurrence, being more harmful when present in the A-band TTN, presumably with dominant negative/gain-of-function mechanisms. However, these insights are challenged by the depiction of position-independent toxicity of TTNtv acting via haploinsufficient alleles, which are sufficient to induce cardiac pathology upon stress. In the current review, we provide an overview of TTN and discuss studies investigating various TTN mutations. We also present an overview of different mechanisms postulated or experimentally validated in the pathogenicity of TTNtv. DCM-causing genes are also discussed with respect to non-truncating mutations in the etiology of DCM. One way of understanding pathogenic variants is probably to understand the context in which they may or may not affect protein-protein interactions, changes in cell signaling, and substrate specificity. In this regard, we also provide a brief overview of TTN interactions in situ. Quantitative models in the risk assessment of TTNtv are also discussed. In summary, we highlight the importance of gene-environment interactions in the etiology of DCM and further mechanistic studies used to delineate the pathways which could be targeted in the management of DCM.
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Differential isoform expression and selective muscle involvement in muscular dystrophies. THE AMERICAN JOURNAL OF PATHOLOGY 2015; 185:2833-42. [PMID: 26269091 DOI: 10.1016/j.ajpath.2015.06.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 12/23/2022]
Abstract
Despite the expression of the mutated gene in all muscles, selective muscles are involved in genetic muscular dystrophies. Different muscular dystrophies show characteristic patterns of fatty degenerative changes by muscle imaging, even to the extent that the patterns have been used for diagnostic purposes. However, the underlying molecular mechanisms explaining the selective involvement of muscles are not known. To test the hypothesis that different muscles may express variable amounts of different isoforms of muscle genes, we applied a custom-designed exon microarray containing probes for 57 muscle-specific genes to assay the transcriptional profiles in sets of human adult lower limb skeletal muscles. Quantitative real-time PCR and whole transcriptome sequencing were used to further analyze the results. Our results demonstrate significant variations in isoform and gene expression levels in anatomically different muscles. Comparison of the known patterns of selective involvement of certain muscles in two autosomal dominant titinopathies and one autosomal dominant myosinopathy, with the isoform and gene expression results, shows a correlation between the specific muscles involved and significant differences in the level of expression of the affected gene and exons in these same muscles compared with some other selected muscles. Our results suggest that differential expression levels of muscle genes and isoforms are one determinant in the selectivity of muscle involvement in muscular dystrophies.
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Uruha A, Hayashi YK, Oya Y, Mori-Yoshimura M, Kanai M, Murata M, Kawamura M, Ogata K, Matsumura T, Suzuki S, Takahashi Y, Kondo T, Kawarabayashi T, Ishii Y, Kokubun N, Yokoi S, Yasuda R, Kira JI, Mitsuhashi S, Noguchi S, Nonaka I, Nishino I. Necklace cytoplasmic bodies in hereditary myopathy with early respiratory failure. J Neurol Neurosurg Psychiatry 2015; 86:483-9. [PMID: 25253871 DOI: 10.1136/jnnp-2014-309009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/07/2014] [Indexed: 12/21/2022]
Abstract
BACKGROUND In hereditary myopathy with early respiratory failure (HMERF), cytoplasmic bodies (CBs) are often localised in subsarcolemmal regions, with necklace-like alignment (necklace CBs), in muscle fibres although their sensitivity and specificity are unknown. OBJECTIVE To elucidate the diagnostic value of the necklace CBs in the pathological diagnosis of HMERF among myofibrillar myopathies (MFMs). METHODS We sequenced the exon 343 of TTN gene (based on ENST00000589042), which encodes the fibronectin-3 (FN3) 119 domain of the A-band and is a mutational hot spot for HMERF, in genomic DNA from 187 patients from 175 unrelated families who were pathologically diagnosed as MFM. We assessed the sensitivity and specificity of the necklace CBs for HMERF by re-evaluating the muscle pathology of our patients with MFM. RESULTS TTN mutations were identified in 17 patients from 14 families, whose phenotypes were consistent with HMERF. Among them, 14 patients had necklace CBs. In contrast, none of other patients with MFM had necklace CBs except for one patient with reducing body myopathy. The sensitivity and specificity were 82% and 99%, respectively. Positive predictive value was 93% in the MFM cohort. CONCLUSIONS The necklace CB is a useful diagnostic marker for HMERF. When muscle pathology shows necklace CBs, sequencing the FN3 119 domain of A-band in TTN should be considered.
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Affiliation(s)
- Akinori Uruha
- Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan Department of Education, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan
| | - Yukiko K Hayashi
- Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan Department of Neurophysiology, Tokyo Medical University, Tokyo, Japan
| | - Yasushi Oya
- Department of Neurology, National Center Hospital, NCNP, Tokyo, Japan
| | | | - Masahiro Kanai
- Department of Neurology, National Center Hospital, NCNP, Tokyo, Japan
| | - Miho Murata
- Department of Neurology, National Center Hospital, NCNP, Tokyo, Japan
| | - Mayumi Kawamura
- Department of Neurology, Japanese Red Cross Society, Wakayama Medical Center, Wakayama, Japan
| | - Katsuhisa Ogata
- Institute of Clinical Research/Department of Neurology, National Hospital Organization Higashisaitama Hospital, Saitama, Japan
| | - Tsuyoshi Matsumura
- Department of Neurology, National Hospital Organization Toneyama National Hospital, Osaka, Japan
| | - Shigeaki Suzuki
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Yukako Takahashi
- Department of Neurology, Osaka Red Cross Hospital, Osaka, Japan Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takayuki Kondo
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takeshi Kawarabayashi
- Department of Neurology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, Aomori, Japan
| | - Yuko Ishii
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Norito Kokubun
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Satoshi Yokoi
- Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Rei Yasuda
- Department of Neurology, National Hospital Organization Maizuru Medical Center, Kyoto, Japan
| | - Jun-ichi Kira
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Satomi Mitsuhashi
- Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan
| | - Satoru Noguchi
- Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan
| | - Ikuya Nonaka
- Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan Institute of Clinical Research/Department of Neurology, National Hospital Organization Higashisaitama Hospital, Saitama, Japan
| | - Ichizo Nishino
- Department of Clinical Development, Translational Medical Center, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan Department of Neuromuscular Research, National Institute of Neuroscience, NCNP, Tokyo, Japan
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Palmio J, Evilä A, Chapon F, Tasca G, Xiang F, Brådvik B, Eymard B, Echaniz-Laguna A, Laporte J, Kärppä M, Mahjneh I, Quinlivan R, Laforêt P, Damian M, Berardo A, Taratuto AL, Bueri JA, Tommiska J, Raivio T, Tuerk M, Gölitz P, Chevessier F, Sewry C, Norwood F, Hedberg C, Schröder R, Edström L, Oldfors A, Hackman P, Udd B. Hereditary myopathy with early respiratory failure: occurrence in various populations. J Neurol Neurosurg Psychiatry 2014; 85:345-53. [PMID: 23606733 DOI: 10.1136/jnnp-2013-304965] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
OBJECTIVE Several families with characteristic features of hereditary myopathy with early respiratory failure (HMERF) have remained without genetic cause. This international study was initiated to clarify epidemiology and the genetic underlying cause in these families, and to characterise the phenotype in our large cohort. METHODS DNA samples of all currently known families with HMERF without molecular genetic cause were obtained from 12 families in seven different countries. Clinical, histopathological and muscle imaging data were collected and five biopsy samples made available for further immunohistochemical studies. Genotyping, exome sequencing and Sanger sequencing were used to identify and confirm sequence variations. RESULTS All patients with clinical diagnosis of HMERF were genetically solved by five different titin mutations identified. One mutation has been reported while four are novel, all located exclusively in the FN3 119 domain (A150) of A-band titin. One of the new mutations showed semirecessive inheritance pattern with subclinical myopathy in the heterozygous parents. Typical clinical features were respiratory failure at mid-adulthood in an ambulant patient with very variable degree of muscle weakness. Cytoplasmic bodies were retrospectively observed in all muscle biopsy samples and these were reactive for myofibrillar proteins but not for titin. CONCLUSIONS We report an extensive collection of families with HMERF with five different mutations in exon 343 of TTN, which establishes this exon as the primary target for molecular diagnosis of HMERF. Our relatively large number of new families and mutations directly implies that HMERF is not extremely rare, not restricted to Northern Europe and should be considered in undetermined myogenic respiratory failure.
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Affiliation(s)
- Johanna Palmio
- Department of Neurology, Neuromuscular Research Unit, Tampere University and University Hospital, , Tampere, Finland
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Pfeffer G, Barresi R, Wilson IJ, Hardy SA, Griffin H, Hudson J, Elliott HR, Ramesh AV, Radunovic A, Winer JB, Vaidya S, Raman A, Busby M, Farrugia ME, Ming A, Everett C, Emsley HCA, Horvath R, Straub V, Bushby K, Lochmüller H, Chinnery PF, Sarkozy A. Titin founder mutation is a common cause of myofibrillar myopathy with early respiratory failure. J Neurol Neurosurg Psychiatry 2014; 85:331-8. [PMID: 23486992 PMCID: PMC6558248 DOI: 10.1136/jnnp-2012-304728] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
OBJECTIVE Titin gene (TTN) mutations have been described in eight families with hereditary myopathy with early respiratory failure (HMERF). Some of the original patients had features resembling myofibrillar myopathy (MFM), arguing that TTN mutations could be a much more common cause of inherited muscle disease, especially in presence of early respiratory involvement. METHODS We studied 127 undiagnosed patients with clinical presentation compatible with MFM. Sanger sequencing for the two previously described TTN mutations in HMERF (p.C30071R in the 119th fibronectin-3 (FN3) domain, and p.R32450W in the kinase domain) was performed in all patients. Patients with mutations had detailed review of their clinical records, muscle MRI findings and muscle pathology. RESULTS We identified five new families with the p.C30071R mutation who were clinically similar to previously reported cases, and muscle pathology demonstrated diagnostic features of MFM. Two further families had novel variants in the 119th FN3 domain (p.P30091L and p.N30145K). No patients were identified with mutations at position p.32450. CONCLUSIONS Mutations in TTN are a cause of MFM, and titinopathy is more common than previously thought. The finding of the p.C30071R mutation in 3.9% of our study population is likely due to a British founder effect. The occurrence of novel FN3 domain variants, although still of uncertain pathogenicity, suggests that other mutations in this domain may cause MFM, and that the disease is likely to be globally distributed. We suggest that HMERF due to mutations in the TTN gene be nosologically classified as MFM-titinopathy.
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Affiliation(s)
- Gerald Pfeffer
- Institute of Genetic Medicine, International Centre for Life, Newcastle University, , Newcastle upon Tyne, UK
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Toro C, Olivé M, Dalakas MC, Sivakumar K, Bilbao JM, Tyndel F, Vidal N, Farrero E, Sambuughin N, Goldfarb LG. Exome sequencing identifies titin mutations causing hereditary myopathy with early respiratory failure (HMERF) in families of diverse ethnic origins. BMC Neurol 2013; 13:29. [PMID: 23514108 PMCID: PMC3610280 DOI: 10.1186/1471-2377-13-29] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 03/08/2013] [Indexed: 01/12/2023] Open
Abstract
Background Hereditary myopathy with early respiratory failure (HMERF) was described in several North European families and recently linked to a titin gene (TTN) mutation. We independently studied HMERF-like diseases with the purpose to identify the cause, refine diagnostic criteria, and estimate the frequency of this disease among myopathy patients of various ethnic origins. Methods Whole exome sequencing analysis was carried out in a large U.S. family that included seven members suffering from skeletal muscle weakness and respiratory failure. Subsequent mutation screening was performed in further 45 unrelated probands with similar phenotypes. Studies included muscle strength evaluation, nerve conduction studies and concentric needle EMG, respiratory function test, cardiologic examination, and muscle biopsy. Results A novel TTN p.Gly30150Asp mutation was identified in the highly conserved A-band of titin that co-segregated with the disease in the U.S. family. Screening of 45 probands initially diagnosed as myofibrillar myopathy (MFM) but excluded based on molecular screening for the known MFM genes led to the identification of a previously reported TTN p.Cys30071Arg mutation in one patient. This same mutation was also identified in a patient with suspected HMERF. The p.Gly30150Asp and p.Cys30071Arg mutations are localized to a side chain of fibronectin type III element A150 of the 10th C-zone super-repeat of titin. Conclusions Missense mutations in TTN are the cause of HMERF in families of diverse origins. A comparison of phenotypic features of HMERF caused by the three known TTN mutations in various populations allowed to emphasize distinct clinical/pathological features that can serve as the basis for diagnosis. The newly identified p.Gly30150Asp and the p.Cys30071Arg mutation are localized to a side chain of fibronectin type III element A150 of the 10th C-zone super-repeat of titin.
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Affiliation(s)
- Camilo Toro
- Undiagnosed Diseases Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
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Pfeffer G, Elliott HR, Griffin H, Barresi R, Miller J, Marsh J, Evilä A, Vihola A, Hackman P, Straub V, Dick DJ, Horvath R, Santibanez-Koref M, Udd B, Chinnery PF. Titin mutation segregates with hereditary myopathy with early respiratory failure. ACTA ACUST UNITED AC 2012; 135:1695-713. [PMID: 22577215 DOI: 10.1093/brain/aws102] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In 2001, we described an autosomal dominant myopathy characterized by neuromuscular ventilatory failure in ambulant patients. Here we describe the underlying genetic basis for the disorder, and we define the neuromuscular, respiratory and radiological phenotype in a study of 31 mutation carriers followed for up to 31 years. A combination of genome-wide linkage and whole exome sequencing revealed the likely causal genetic variant in the titin (TTN) gene (g.274375T>C; p.Cys30071Arg) within a shared haplotype of 2.93 Mbp on chromosome 2. This segregated with the phenotype in 21 individuals from the original family, nine subjects in a second family with the same highly selective pattern of muscle involvement on magnetic resonance imaging and a third familial case with a similar phenotype. Comparing the mutation carriers revealed novel features not apparent in our original report. The clinical presentation included predominant distal, proximal or respiratory muscle weakness. The age of onset was highly variable, from early adulthood, and including a mild phenotype in advanced age. Muscle weakness was earlier onset and more severe in the lower extremities in nearly all patients. Seven patients also had axial muscle weakness. Respiratory function studies demonstrated a gradual deterioration over time, reflecting the progressive nature of this condition. Cardiomyopathy was not present in any of our patients despite up to 31 years of follow-up. Magnetic resonance muscle imaging was performed in 21 affected patients and revealed characteristic abnormalities with semitendinosus involvement in 20 of 21 patients studied, including 3 patients who were presymptomatic. Diagnostic muscle histopathology most frequently revealed eosinophilic inclusions (inclusion bodies) and rimmed vacuoles, but was non-specific in a minority of patients. These findings have important clinical implications. This disease should be considered in patients with adult-onset proximal or distal myopathy and early respiratory failure, even in the presence of non-specific muscle pathology. Muscle magnetic resonance imaging findings are characteristic and should be considered as an initial investigation, and if positive should prompt screening for mutations in TTN. With 363 exons, screening TTN presented a major challenge until recently. However, whole exome sequencing provides a reliable cost-effective approach, providing the gene of interest is adequately captured.
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Affiliation(s)
- Gerald Pfeffer
- Institute of Genetic Medicine, Central Parkway, Newcastle, NE1 3BZ, UK
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Ohlsson M, Hedberg C, Brådvik B, Lindberg C, Tajsharghi H, Danielsson O, Melberg A, Udd B, Martinsson T, Oldfors A. Hereditary myopathy with early respiratory failure associated with a mutation in A-band titin. ACTA ACUST UNITED AC 2012; 135:1682-94. [PMID: 22577218 DOI: 10.1093/brain/aws103] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hereditary myopathy with early respiratory failure and extensive myofibrillar lesions has been described in sporadic and familial cases and linked to various chromosomal regions. The mutated gene is unknown in most cases. We studied eight individuals, from three apparently unrelated families, with clinical and pathological features of hereditary myopathy with early respiratory failure. The investigations included clinical examination, muscle histopathology and genetic analysis by whole exome sequencing and single nucleotide polymorphism arrays. All patients had adult onset muscle weakness in the pelvic girdle, neck flexors, respiratory and trunk muscles, and the majority had prominent calf hypertrophy. Examination of pulmonary function showed decreased vital capacity. No signs of cardiac muscle involvement were found. Muscle histopathological features included marked muscle fibre size variation, fibre splitting, numerous internal nuclei and fatty infiltration. Frequent groups of fibres showed eosinophilic inclusions and deposits. At the ultrastructural level, there were extensive myofibrillar lesions with marked Z-disc alterations. Whole exome sequencing in four individuals from one family revealed a missense mutation, g.274375T>C; p.Cys30071Arg, in the titin gene (TTN). The mutation, which changes a highly conserved residue in the myosin binding A-band titin, was demonstrated to segregate with the disease in all three families. High density single nucleotide polymorphism arrays covering the entire genome demonstrated sharing of a 6.99 Mb haplotype, located in chromosome region 2q31 including TTN, indicating common ancestry. Our results demonstrate a novel and the first disease-causing mutation in A-band titin associated with hereditary myopathy with early respiratory failure. The typical histopathological features with prominent myofibrillar lesions and inclusions in muscle and respiratory failure early in the clinical course should be incentives for analysis of TTN mutations.
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Affiliation(s)
- Monica Ohlsson
- Department of Pathology, Institute of Biomedicine, University of Gothenburg, Sahlgrenska University Hospital, SE-413 45 Gothenburg, Sweden
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New phenotype and pathology features in MYH7-related distal myopathy. Neuromuscul Disord 2012; 22:640-7. [PMID: 22521714 DOI: 10.1016/j.nmd.2012.03.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/06/2012] [Accepted: 03/02/2012] [Indexed: 11/22/2022]
Abstract
Laing distal myopathy is an autosomal dominant disease due to mutations in the gene encoding for the human slow-β myosin heavy chain, MYH7. Most reports describe it as a mild, early onset myopathy with involvement usually restricted to foot extensors, hand finger extensors and neck flexors, and unspecific findings on muscle biopsy. We identified the first two Italian families with Laing distal myopathy, harboring two novel mutations in the MYH7 gene and performed clinical, neurophysiological, pathological, muscle MRI and cardiological investigations on affected members from the two families. Subjects from one family presented a moderate-severe phenotype, with proximal together with distal involvement and even loss of ambulation at advanced age. One patient displayed atypical muscle biopsy findings including cytoplasmic bodies and myofibrillar myopathy-like features. Affected members from the second family shared a very mild phenotype, with weakness largely limited to long toe and foot extensors and/or late onset. No patient showed any sign of heart involvement. Our study significantly broadens the clinical and pathological spectrum of Laing distal myopathy. We suggest that MYH7 screening should be considered in undiagnosed late-onset distal myopathy or cytoplasmic body myopathy patients.
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Gautel M. Cytoskeletal protein kinases: titin and its relations in mechanosensing. Pflugers Arch 2011; 462:119-34. [PMID: 21416260 PMCID: PMC3114093 DOI: 10.1007/s00424-011-0946-1] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 02/15/2011] [Accepted: 02/18/2011] [Indexed: 12/22/2022]
Abstract
Titin, the giant elastic ruler protein of striated muscle sarcomeres, contains a catalytic kinase domain related to a family of intrasterically regulated protein kinases. The most extensively studied member of this branch of the human kinome is the Ca2+–calmodulin (CaM)-regulated myosin light-chain kinases (MLCK). However, not all kinases of the MLCK branch are functional MLCKs, and about half lack a CaM binding site in their C-terminal autoinhibitory tail (AI). A unifying feature is their association with the cytoskeleton, mostly via actin and myosin filaments. Titin kinase, similar to its invertebrate analogue twitchin kinase and likely other “MLCKs”, is not Ca2+–calmodulin-activated. Recently, local protein unfolding of the C-terminal AI has emerged as a common mechanism in the activation of CaM kinases. Single-molecule data suggested that opening of the TK active site could also be achieved by mechanical unfolding of the AI. Mechanical modulation of catalytic activity might thus allow cytoskeletal signalling proteins to act as mechanosensors, creating feedback mechanisms between cytoskeletal tension and tension generation or cellular remodelling. Similar to other MLCK-like kinases like DRAK2 and DAPK1, TK is linked to protein turnover regulation via the autophagy/lysosomal system, suggesting the MLCK-like kinases have common functions beyond contraction regulation.
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Affiliation(s)
- Mathias Gautel
- King's College London BHF Centre of Research Excellence, Cardiovascular Division, London, SE1 1UL, UK.
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