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Chai W, Qu H, Ma Q, Zhu M, Li M, Zhan Y, Liu Z, Xu J, Yao H, Li Z, Wang C. RNA-seq analysis identifies differentially expressed gene in different types of donkey skeletal muscles. Anim Biotechnol 2023; 34:1786-1795. [PMID: 35302433 DOI: 10.1080/10495398.2022.2050920] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
The main component of donkey meat is skeletal muscle, and different muscle fibers have been found to be associated with meat quality. However, RNA-seq technology has yet to be used to profile the transcriptomic changes of different muscles of the donkey. In this study, the characterizations of different muscles on the gene expression profiles of Dezhou donkey were obtained, the aim was to identify the important genes in donkey muscles, and aid in improving donkey meat quality via RNA-seq. In the donkey gluteus (DG) and donkey longissimus dorsi (DL) group, GO enrichment indicated that DEGs were mainly involved in the biological regulation and metabolic process, and KEGG analysis shows that a total of 427 DEGs were mapped to 216 KEGG pathways and 23 KEGG pathways were significantly enriched such as the ribosome, glycolysis/gluconeogenesis, glucagon signaling pathway and biosynthesis of amino acids pathways. Meanwhile, 504 DEGs were mapped to 223 KEGG pathways, in which 17 were significantly enriched including cardiac muscle contraction and oxytocin signaling pathway in donkey hamstring muscles (DH) and DL group. In addition, the tenderness in donkey meat might involve muscle fiber type and glucose metabolism, which might profit from the DEGs including MYH1, MYH7, TNNC1, TNNI3, TPM3, ALDOA, ENO3, and PGK1. The genes found in this study will provide some ideas for further understanding the molecular mechanism of donkey meat quality.
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Affiliation(s)
- Wenqiong Chai
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Honglei Qu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China
- National Engineering Research Center for Gelatin-based Traditional Chinese Medicine, Dong-E-E-Jiao Co. Ltd, Liaocheng, China
| | - Qiugang Ma
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Mingxia Zhu
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Mengmeng Li
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Yandong Zhan
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Ziwen Liu
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Jing Xu
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Huanfen Yao
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Zeyu Li
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
| | - Changfa Wang
- Liaocheng Research Institute of Donkey High-efficiency Breeding and Ecological Feeding, Liaocheng University, Liaocheng, China
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2
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Holling T, Lisfeld J, Johannsen J, Matschke J, Song F, Altmeppen HC, Kutsche K. Autosomal dominantly inherited myopathy likely caused by the TNNT1 variant p.(Asp65Ala). Hum Mutat 2022; 43:1224-1233. [PMID: 35510366 DOI: 10.1002/humu.24397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 04/25/2022] [Accepted: 05/01/2022] [Indexed: 11/12/2022]
Abstract
Nemaline myopathies (NEM) are genetically and clinically heterogenous. Biallelic or monoallelic variants in TNNT1, encoding slow skeletal troponin T1 (TnT1), cause NEM. We report a 2-year-old patient and his mother carrying the heterozygous TNNT1 variant c.194A>C/p.(Asp65Ala) that occurred de novo in the mother. Both had muscle hypotrophy and muscle weakness. Muscle pathology in the proband's mother revealed slow twitch type 1 fiber hypotrophy and fast twitch type 2 fiber hypertrophy that was confirmed by a reduced ratio of slow skeletal myosin to fast skeletal myosin type 2a. RT-PCR and immunoblotting data demonstrated increased levels of high-molecular-weight TnT1 isoforms in skeletal muscle of the proband's mother that were also observed in some controls. In an overexpression system, complex formation of TnT1-D65A with tropomyosin 3 (TPM3) was enhanced. The previously reported TnT1-E104V and TnT1-L96P mutants showed reduced or no co-immunoprecipitation with TPM3. Our studies support pathogenicity of the TNNT1 p.(Asp65Ala) variant. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Tess Holling
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jasmin Lisfeld
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jessika Johannsen
- Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jakob Matschke
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Feizhi Song
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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3
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Rasmussen M, Jin JP. Troponin Variants as Markers of Skeletal Muscle Health and Diseases. Front Physiol 2021; 12:747214. [PMID: 34733179 PMCID: PMC8559874 DOI: 10.3389/fphys.2021.747214] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 09/01/2021] [Indexed: 12/21/2022] Open
Abstract
Ca2 +-regulated contractility is a key determinant of the quality of muscles. The sarcomeric myofilament proteins are essential players in the contraction of striated muscles. The troponin complex in the actin thin filaments plays a central role in the Ca2+-regulation of muscle contraction and relaxation. Among the three subunits of troponin, the Ca2+-binding subunit troponin C (TnC) is a member of the calmodulin super family whereas troponin I (TnI, the inhibitory subunit) and troponin T (TnT, the tropomyosin-binding and thin filament anchoring subunit) are striated muscle-specific regulatory proteins. Muscle type-specific isoforms of troponin subunits are expressed in fast and slow twitch fibers and are regulated during development and aging, and in adaptation to exercise or disuse. TnT also evolved with various alternative splice forms as an added capacity of muscle functional diversity. Mutations of troponin subunits cause myopathies. Owing to their physiological and pathological importance, troponin variants can be used as specific markers to define muscle quality. In this focused review, we will explore the use of troponin variants as markers for the fiber contents, developmental and differentiation states, contractile functions, and physiological or pathophysiological adaptations of skeletal muscle. As protein structure defines function, profile of troponin variants illustrates how changes at the myofilament level confer functional qualities at the fiber level. Moreover, understanding of the role of troponin modifications and mutants in determining muscle contractility in age-related decline of muscle function and in myopathies informs an approach to improve human health.
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Affiliation(s)
- Monica Rasmussen
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Jian-Ping Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, United States
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4
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van de Locht M, Borsboom TC, Winter JM, Ottenheijm CAC. Troponin Variants in Congenital Myopathies: How They Affect Skeletal Muscle Mechanics. Int J Mol Sci 2021; 22:ijms22179187. [PMID: 34502093 PMCID: PMC8430961 DOI: 10.3390/ijms22179187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/19/2021] [Accepted: 08/23/2021] [Indexed: 02/05/2023] Open
Abstract
The troponin complex is a key regulator of muscle contraction. Multiple variants in skeletal troponin encoding genes result in congenital myopathies. TNNC2 has been implicated in a novel congenital myopathy, TNNI2 and TNNT3 in distal arthrogryposis (DA), and TNNT1 and TNNT3 in nemaline myopathy (NEM). Variants in skeletal troponin encoding genes compromise sarcomere function, e.g., by altering the Ca2+ sensitivity of force or by inducing atrophy. Several potential therapeutic strategies are available to counter the effects of variants, such as troponin activators, introduction of wild-type protein through AAV gene therapy, and myosin modulation to improve muscle contraction. The mechanisms underlying the pathophysiological effects of the variants in skeletal troponin encoding genes are incompletely understood. Furthermore, limited knowledge is available on the structure of skeletal troponin. This review focusses on the physiology of slow and fast skeletal troponin and the pathophysiology of reported variants in skeletal troponin encoding genes. A better understanding of the pathophysiological effects of these variants, together with enhanced knowledge regarding the structure of slow and fast skeletal troponin, will direct the development of treatment strategies.
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5
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Petrucci A, Primiano G, Savarese M, Sancricca C, Udd B, Servidei S. Novel TNNT1 mutation and mild nemaline myopathy phenotype in an Italian patient. Neuromuscul Disord 2021; 31:532-538. [PMID: 33832840 DOI: 10.1016/j.nmd.2021.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 02/15/2021] [Accepted: 03/01/2021] [Indexed: 12/19/2022]
Abstract
Mutations in the TNNT1 gene cause an infantile, lethal form of myopathy named "Amish" Nemaline Myopathy. Adult patients are very rarely described. We report a 49-year-old patient who presented a slowly progressive phenotype characterized by myalgia, exercise intolerance and dyspnea since infancy. In adult life she lapsed into a coma as a result of acute respiratory failure, with the need of tracheostomy, subsequently removed once her respiratory condition improved. Afterwards, non-invasive ventilation was started. Short stature, contractures, a small size posterior cranial fossa and osteonecrosis were additional clinical findings. Muscle MRI showed minor hypotrophy and degenerative changes of the muscles of the posterior thigh compartment and involvement of the paraspinal, medial gastrocnemius and soleus muscles with sparing of the gracilis muscle. Muscle biopsy revealed multiminicores and nemaline rods. Genetic analysis identified a new pathogenetic biallelic deletion c.786delG p.(Lys263Serfs*36) in exon 13 of TNNT1 gene. This case confirms that recessive mutations in TNNT1 gene can manifest mainly with respiratory failure in adult life.
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Affiliation(s)
- Antonio Petrucci
- Center for Neuromuscular and Neurological Rare Diseases, Neuroscience Department, San Camillo-Forlanini Hospital, Rome, Italy
| | - Guido Primiano
- UOC Neurofisiopatologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo Agostino Gemelli 8, Rome 00168, Italy; Dipartimento Universitario di Neuroscienze, Università Cattolica del Sacro Cuore, Roma, Italy.
| | - Marco Savarese
- Folkhälsan Research Center, Helsinki, Finland; Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Cristina Sancricca
- UOC Neurofisiopatologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo Agostino Gemelli 8, Rome 00168, Italy; Dipartimento Universitario di Neuroscienze, Università Cattolica del Sacro Cuore, Roma, Italy
| | - Bjarne Udd
- Folkhälsan Research Center, Helsinki, Finland; Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland; Neuromuscular Research Center, Tampere University and University Hospital, Tampere, Finland; Department of Neurology, Vaasa Central Hospital, Vaasa, Finland
| | - Serenella Servidei
- UOC Neurofisiopatologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo Agostino Gemelli 8, Rome 00168, Italy; Dipartimento Universitario di Neuroscienze, Università Cattolica del Sacro Cuore, Roma, Italy
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6
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Géraud J, Dieterich K, Rendu J, Uro Coste E, Dobrzynski M, Marcorelle P, Ioos C, Romero NB, Baudou E, Brocard J, Coville AC, Fauré J, Koenig M, Juntas Morales R, Lacène E, Madelaine A, Marty I, Pegeot H, Theze C, Siegfried A, Cossee M, Cances C. Clinical phenotype and loss of the slow skeletal muscle troponin T in three new patients with recessive TNNT1 nemaline myopathy. J Med Genet 2020; 58:602-608. [PMID: 32994279 PMCID: PMC8394741 DOI: 10.1136/jmedgenet-2019-106714] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 06/12/2020] [Accepted: 07/05/2020] [Indexed: 01/08/2023]
Abstract
Background Congenital nemaline myopathies are rare pathologies characterised by muscle weakness and rod-shaped inclusions in the muscle fibres. Methods Using next-generation sequencing, we identified three patients with pathogenic variants in the Troponin T type 1 (TNNT1) gene, coding for the troponin T (TNT) skeletal muscle isoform. Results The clinical phenotype was similar in all patients, associating hypotonia, orthopaedic deformities and progressive chronic respiratory failure, leading to early death. The anatomopathological phenotype was characterised by a disproportion in the muscle fibre size, endomysial fibrosis and nemaline rods. Molecular analyses of TNNT1 revealed a homozygous deletion of exons 8 and 9 in patient 1; a heterozygous nonsense mutation in exon 9 and retention of part of intron 4 in muscle transcripts in patient 2; and a homozygous, very early nonsense mutation in patient 3. Western blot analyses confirmed the absence of the TNT protein resulting from these mutations. Discussion The clinical and anatomopathological presentations of our patients reinforce the homogeneous character of the phenotype associated with recessive TNNT1 mutations. Previous studies revealed an impact of recessive variants on the tropomyosin-binding affinity of TNT. We report in our patients a complete loss of TNT protein due to open reading frame disruption or to post-translational degradation of TNT.
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Affiliation(s)
- Justine Géraud
- Neuropediatric Department, University Hospital Centre Toulouse, Toulouse, France
| | - Klaus Dieterich
- INSERM U1216, Grenoble Alpes University Hospital, Grenoble, France.,INSERM U1037, Cancer Research Center of Toulouse (CRCT), Department of Pathology, Toulouse University Hospital, Toulouse, France
| | - John Rendu
- INSERM U1216, Grenoble Alpes University Hospital, Grenoble, France.,INSERM U1216, University of Grenoble Alpes, Grenoble, France
| | - Emmanuelle Uro Coste
- INSERM U1037, Cancer Research Center of Toulouse (CRCT), Department of Pathology, Toulouse University Hospital, Toulouse, France
| | | | - Pascale Marcorelle
- Pathology Department, Brest University Hospital, Morvan Hospital, Brest, France
| | - Christine Ioos
- Neuropediatric Department, Garches University Hospital Center, Garches, France
| | - Norma Beatriz Romero
- UMRS974, CNRS FRE3617, Center for Research in Myology, INSERM, CNRS, Sorbonne University, UPMC University of Paris 06, Paris, France.,Myology Institute, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière University Hospital, Paris, France
| | - Eloise Baudou
- Neuropediatric Department, University Hospital Centre Toulouse, Toulouse, France
| | - Julie Brocard
- INSERM U1216, Grenoble Alpes University Hospital, Grenoble, France.,INSERM U1216, University of Grenoble Alpes, Grenoble, France
| | - Anne-Cécile Coville
- Neuropediatric Department, University Hospital Centre Toulouse, Toulouse, France
| | - Julien Fauré
- INSERM U1216, Grenoble Alpes University Hospital, Grenoble, France.,INSERM U1216, University of Grenoble Alpes, Grenoble, France
| | - Michel Koenig
- Molecular Genetics Laboratory, LGMR, Montpellier University Hospital Centre, University of Montpellier, Montpellier, France
| | - Raul Juntas Morales
- Molecular Genetics Laboratory, LGMR, Montpellier University Hospital Centre, University of Montpellier, Montpellier, France
| | - Emmanuelle Lacène
- UMRS974, CNRS FRE3617, Center for Research in Myology, INSERM, CNRS, Sorbonne University, UPMC University of Paris 06, Paris, France.,Myology Institute, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière University Hospital, Paris, France
| | - Angéline Madelaine
- UMRS974, CNRS FRE3617, Center for Research in Myology, INSERM, CNRS, Sorbonne University, UPMC University of Paris 06, Paris, France.,Myology Institute, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière University Hospital, Paris, France
| | - Isabelle Marty
- INSERM U1216, Grenoble Alpes University Hospital, Grenoble, France.,INSERM U1216, University of Grenoble Alpes, Grenoble, France
| | - Henri Pegeot
- Molecular Genetics Laboratory, LGMR, Montpellier University Hospital Centre, University of Montpellier, Montpellier, France
| | - Corinne Theze
- Molecular Genetics Laboratory, LGMR, Montpellier University Hospital Centre, University of Montpellier, Montpellier, France
| | | | - Mireille Cossee
- Molecular Genetics Laboratory, LGMR, Montpellier University Hospital Centre, University of Montpellier, Montpellier, France
| | - Claude Cances
- Neuropediatric Department, University Hospital Centre Toulouse, Toulouse, France
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7
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Clayton JS, McNamara EL, Goullee H, Conijn S, Muthsam K, Musk GC, Coote D, Kijas J, Testa AC, Taylor RL, O’Hara AJ, Groth D, Ottenheijm C, Ravenscroft G, Laing NG, Nowak KJ. Ovine congenital progressive muscular dystrophy (OCPMD) is a model of TNNT1 congenital myopathy. Acta Neuropathol Commun 2020; 8:142. [PMID: 32819427 PMCID: PMC7441672 DOI: 10.1186/s40478-020-01017-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/10/2020] [Indexed: 12/21/2022] Open
Abstract
Ovine congenital progressive muscular dystrophy (OCPMD) was first described in Merino sheep flocks in Queensland and Western Australia in the 1960s and 1970s. The most prominent feature of the disease is a distinctive gait with stiffness of the hind limbs that can be seen as early as 3 weeks after birth. The disease is progressive. Histopathological examination had revealed dystrophic changes specifically in type I (slow) myofibres, while electron microscopy had demonstrated abundant nemaline bodies. Therefore, it was never certain whether the disease was a dystrophy or a congenital myopathy with dystrophic features. In this study, we performed whole genome sequencing of OCPMD sheep and identified a single base deletion at the splice donor site (+ 1) of intron 13 in the type I myofibre-specific TNNT1 gene (KT218690 c.614 + 1delG). All affected sheep were homozygous for this variant. Examination of TNNT1 splicing by RT-PCR showed intron retention and premature termination, which disrupts the highly conserved 14 amino acid C-terminus. The variant did not reduce TNNT1 protein levels or affect its localization but impaired its ability to modulate muscle contraction in response to Ca2+ levels. Identification of the causative variant in TNNT1 finally clarifies that the OCPMD sheep is in fact a large animal model of TNNT1 congenital myopathy. This model could now be used for testing molecular or gene therapies.
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Pellerin D, Aykanat A, Ellezam B, Troiano EC, Karamchandani J, Dicaire MJ, Petitclerc M, Robertson R, Allard-Chamard X, Brunet D, Konersman CG, Mathieu J, Warman Chardon J, Gupta VA, Beggs AH, Brais B, Chrestian N. Novel Recessive TNNT1 Congenital Core-Rod Myopathy in French Canadians. Ann Neurol 2020; 87:568-583. [PMID: 31970803 DOI: 10.1002/ana.25685] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 01/06/2020] [Accepted: 01/19/2020] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Recessive null variants of the slow skeletal muscle troponin T1 (TNNT1) gene are a rare cause of nemaline myopathy that is fatal in infancy due to respiratory insufficiency. Muscle biopsy shows rods and fiber type disproportion. We report on 4 French Canadians with a novel form of recessive congenital TNNT1 core-rod myopathy. METHODS Patients underwent full clinical characterization, lower limb magnetic resonance imaging (MRI), muscle biopsy, and genetic testing. A zebrafish loss-of-function model using morpholinos was created to assess the pathogenicity of the identified variant. Wild-type or mutated human TNNT1 mRNAs were coinjected with morpholinos to assess their abilities to rescue the morphant phenotype. RESULTS Three adults and 1 child shared a novel missense homozygous variant in the TNNT1 gene (NM_003283.6: c.287T > C; p.Leu96Pro). They developed from childhood very slowly progressive limb-girdle weakness with rigid spine and disabling contractures. They suffered from restrictive lung disease requiring noninvasive mechanical ventilation in 3 patients, as well as recurrent episodes of rhabdomyolysis triggered by infections, which were relieved by dantrolene in 1 patient. Older patients remained ambulatory into their 60s. MRI of the leg muscles showed fibrofatty infiltration predominating in the posterior thigh and the deep posterior leg compartments. Muscle biopsies showed multiminicores and lobulated fibers, rods in half the patients, and no fiber type disproportion. Wild-type TNNT1 mRNA rescued the zebrafish morphants, but mutant transcripts failed to do so. INTERPRETATION This study expands the phenotypic spectrum of TNNT1 myopathy and provides functional evidence for the pathogenicity of the newly identified missense mutation. ANN NEUROL 2020;87:568-583.
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Affiliation(s)
- David Pellerin
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Asli Aykanat
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Benjamin Ellezam
- Department of Pathology, Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montreal, Quebec, Canada
| | - Emily C Troiano
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Jason Karamchandani
- Department of Pathology, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Marie-Josée Dicaire
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Marc Petitclerc
- Department of Neurology, Hôpital Hôtel-Dieu de Lévis, Lévis, Quebec, Canada
| | - Rebecca Robertson
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Xavier Allard-Chamard
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada
| | - Denis Brunet
- Department of Neurology, Hôpital de l'Enfant Jésus, Université Laval, Quebec City, Quebec, Canada
| | | | - Jean Mathieu
- Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,Neuromuscular Disease Clinic, Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay-Lac-Saint-Jean, Jonquière, Quebec, Canada
| | - Jodi Warman Chardon
- Department of Neurosciences, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Vandana A Gupta
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Bernard Brais
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, Quebec, Canada.,Neuromuscular Disease Clinic, Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay-Lac-Saint-Jean, Jonquière, Quebec, Canada.,Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Nicolas Chrestian
- Department of Child Neurology, Centre Hospitalier de l'Université Laval et Centre Mère-Enfant Soleil, Université Laval, Quebec City, Quebec, Canada
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9
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D'Amico A, Fattori F, Fiorillo C, Paglietti MG, Testa MBC, Verardo M, Catteruccia M, Bruno C, Bertini E. 'Amish Nemaline Myopathy' in 2 Italian siblings harbouring a novel homozygous mutation in Troponin-I gene. Neuromuscul Disord 2019; 29:766-770. [PMID: 31604653 DOI: 10.1016/j.nmd.2019.09.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/10/2019] [Accepted: 09/02/2019] [Indexed: 02/06/2023]
Abstract
Amish Nemaline Myopathy is a severe form of nemaline myopathy associated to mutation in TNNT1 gene, firstly reported among the Old Order Amish. Here we report two Italian siblings who manifested, by the age of 7 months, progressive and severe muscle weakness and wasting, respiratory insufficiency, pectus carinatum deformity and failure to thrive. Muscle biopsy was consistent with nemaline myopathy and novel homozygous missense mutation in TNNT1 was found. Our cases expand the mutational spectrum of TNNT1, confirm the invariable peculiar clinical phenotype also outside the Amish population, and suggest that TNNT1 should be considered for molecular analysis in NM patients with chest deformities and progressive contractures.
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Affiliation(s)
- Adele D'Amico
- Unit of Muscular and Neurodegenerative Disorders, Department of Neurosciences and Neurorehabilitation, Bambino Gesù Children's Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy.
| | - Fabiana Fattori
- Unit of Muscular and Neurodegenerative Disorders, Department of Neurosciences and Neurorehabilitation, Bambino Gesù Children's Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy
| | - Chiara Fiorillo
- Paediatric Neurology and Neuromuscular Disorders Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, Istituto Giannina Gaslini, Genoa, Italy
| | - Maria Giovanna Paglietti
- Respiratory Unit, Academic Department of Pediatrics, Bambino Gesù Children's Hospital, IRCCS, Piazza di Sant' Onofrio 4, 00165 Rome, Italy
| | - Maria Beatrice Chiarini Testa
- Respiratory Unit, Academic Department of Pediatrics, Bambino Gesù Children's Hospital, IRCCS, Piazza di Sant' Onofrio 4, 00165 Rome, Italy
| | - Margherita Verardo
- Unit of Muscular and Neurodegenerative Disorders, Department of Neurosciences and Neurorehabilitation, Bambino Gesù Children's Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy
| | - Michela Catteruccia
- Unit of Muscular and Neurodegenerative Disorders, Department of Neurosciences and Neurorehabilitation, Bambino Gesù Children's Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy
| | - Claudio Bruno
- Center of Translational and Experimental Myology, Istituto Giannina Gaslini, Genova, Italy
| | - Enrico Bertini
- Unit of Muscular and Neurodegenerative Disorders, Department of Neurosciences and Neurorehabilitation, Bambino Gesù Children's Hospital, Piazza S. Onofrio 4, 00165 Rome, Italy
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10
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Chen G, Su Y, Cai Y, He L, Yang G. Comparative transcriptomic analysis reveals beneficial effect of dietary mulberry leaves on the muscle quality of finishing pigs. Vet Med Sci 2019; 5:526-535. [PMID: 31486291 PMCID: PMC6868455 DOI: 10.1002/vms3.187] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Background The aim of this study was to investigate the effect of dietary mulberry leaves on the transcriptome profiles of finishing pigs. RNA‐Seq was used to identify differentially expressed genes (DEGs) in the longissimus dorsi of 56 pigs fed either a traditional diet or diets supplemented with 3%, 6% or 9% mulberry leaf powder, and both gene ontology (GO) function and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses were performed. Furthermore, protein–protein interaction (PPI) network and the subnet module analysis were used to identify genes with beneficial potential, and quantitative real‐time polymerase chain reaction (qRT‐PCR) was used to validate the expression patterns revealed by RNA‐Seq. Results Pigs fed with the 6% mulberry diet exhibited greater average daily gain, lower water loss and lower shear force than the control group and yielded 531 DEGs, including 271 and 260 upregulated and downregulated genes, respectively. Function analysis revealed that the DEGs were significantly enriched in functions related to muscle growth and development. Furthermore, several genes (i.e. ACOT4, ECHS1, HACD1, NPR1, ADCY2, MGLL and IRS1) were enriched in a KEGG pathway that was associated with fatty acid metabolism, and in the PPI subnet module, four of eight node genes, namely TNNC1, MYL3, TCAP and TNNT1, were associated with muscle formation and development. The upregulation of these genes, including TNNC1, TNNT1 and MYL3, was confirmed by qRT‐PCR. Conclusions Dietary mulberry leaves (6%) may improve the muscle quality of pigs by modulating the expression of several key genes, such as TNNC1, MYL3 and TNNT1. The study was aimed to explain the effect of the inclusion of mulberry in the diet of pigs on transcriptome profiling. The inclusion of mulberry in the diet might be helpful in muscle formation and development of pigs by modulating the expression levels of three genes including TNNC1, MYL3 and TNNT1![]()
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Affiliation(s)
- Guoshun Chen
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Yingyu Su
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Yu Cai
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Lianghong He
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
| | - Gang Yang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China
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11
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Oki K, Wei B, Feng HZ, Jin JP. The loss of slow skeletal muscle isoform of troponin T in spindle intrafusal fibres explains the pathophysiology of Amish nemaline myopathy. J Physiol 2019; 597:3999-4012. [PMID: 31148174 PMCID: PMC6675633 DOI: 10.1113/jp278119] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 05/29/2019] [Indexed: 01/17/2023] Open
Abstract
KEY POINTS The pathogenic mechanism and the neuromuscular reflex-related phenotype (e.g. tremors accompanied by clonus) of Amish nemaline myopathy, as well as of other recessively inherited TNNT1 myopathies, remain to be clarified. The truncated slow skeletal muscle isoform of troponin T (ssTnT) encoded by the mutant TNNT1 gene is unable to incorporate into myofilaments and is degraded in muscle cells. By contrast to extrafusal muscle fibres, spindle intrafusal fibres of normal mice contain a significant level of cardiac TnT and a low molecular weight splice form of ssTnT. Intrafusal fibres of ssTnT-knockout mice have significantly increased cardiac TnT. Rotarod and balance beam tests have revealed abnormal neuromuscular co-ordination in ssTnT-knockout mice and a blunted response to a spindle sensitizer, succinylcholine. The loss of ssTnT and a compensatory increase of cardiac TnT in intrafusal nuclear bag fibres may increase myofilament Ca2+ -sensitivity and tension, impairing spindle function, thus identifying a novel mechanism for the development of targeted treatment. ABSTRACT A nonsense mutation at codon Glu180 of TNNT1 gene causes Amish nemaline myopathy (ANM), a recessively inherited disease with infantile lethality. TNNT1 encodes the slow skeletal muscle isoform of troponin T (ssTnT). The truncated ssTnT is unable to incorporate into myofilament and is degraded in muscle cells. The symptoms of ANM include muscle weakness, atrophy, contracture and tremors accompanied by clonus. An ssTnT-knockout (KO) mouse model recapitulates key features of ANM such as atrophy of extrafusal slow muscle fibres and increased fatigability. However, the neuromuscular reflex-related symptoms of ANM have not been explained. By isolating muscle spindles from ssTnT-KO and control mice aiming to examine the composition of myofilament proteins, we found that, in contrast to extrafusal fibres, intrafusal fibres contain a significant level of cardiac TnT and the low molecular weight splice form of ssTnT. Intrafusal fibres from ssTnT-KO mice have significantly increased cardiac TnT. Rotarod and balance beam tests revealed impaired neuromuscular co-ordination in ssTnT-KO mice, indicating abnormality in spindle functions. Unlike the wild-type control, the beam running ability of ssTnT-KO mice had a blunted response to a spindle sensitizer, succinylcholine. Immunohistochemistry detected ssTnT and cardiac TnT in nuclear bag fibres, whereas fast skeletal muscle TnT was detected in nuclear chain fibres, and cardiac α-myosin was present in one of the two nuclear bag fibres. The loss of ssTnT and a compensatory increase of cardiac TnT in nuclear bag fibres would increase myofilament Ca2+ -sensitivity and tension, thus affecting spindle activities. This mechanism provides an explanation for the pathophysiology of ANM, as well as a novel target for treatment.
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Affiliation(s)
| | | | - Han-Zhong Feng
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - J.-P. Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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12
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Abstract
Nemaline myopathy (NM) is among the most common non-dystrophic congenital myopathies (incidence 1:50.000). Hallmark features of NM are skeletal muscle weakness and the presence of nemaline bodies in the muscle fiber. The clinical phenotype of NM patients is quite diverse, ranging from neonatal death to normal lifespan with almost normal motor function. As the respiratory muscles are involved as well, severely affected patients are ventilator-dependent. The mechanisms underlying muscle weakness in NM are currently poorly understood. Therefore, no therapeutic treatment is available yet. Eleven implicated genes have been identified: ten genes encode proteins that are either components of thin filament, or are thought to contribute to stability or turnover of thin filament proteins. The thin filament is a major constituent of the sarcomere, the smallest contractile unit in muscle. It is at this level of contraction – thin-thick filament interaction – where muscle weakness originates in NM patients. This review focusses on how sarcomeric gene mutations directly compromise sarcomere function in NM. Insight into the contribution of sarcomeric dysfunction to muscle weakness in NM, across the genes involved, will direct towards the development of targeted therapeutic strategies.
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Affiliation(s)
| | - Coen A.C. Ottenheijm
- Correspondence to: Coen Ottenheijm, PhD, Department of Physiology, VU University Medical Center, O|2 building, 12W-51, De Boelelaan 1118, 1081 HV Amsterdam, The Netherlands. Tel.: +31 20 4448123; Fax: +31 20 4448124; E-mail:
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13
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Streff H, Bi W, Colón AG, Adesina AM, Miyake CY, Lalani SR. Amish nemaline myopathy and dilated cardiomyopathy caused by a homozygous contiguous gene deletion of TNNT1 and TNNI3 in a Mennonite child. Eur J Med Genet 2018; 62:103567. [PMID: 30395933 DOI: 10.1016/j.ejmg.2018.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 10/05/2018] [Accepted: 11/01/2018] [Indexed: 12/28/2022]
Abstract
Amish nemaline myopathy (ANM) is a severe congenital form of NM, known to be fatal in early childhood due to pulmonary insufficiency. Homozygous mutation in TNNT1 was originally ascertained in an Older Amish community in 2000. To date, only five reports with six pathogenic variants in TNNT1 have been described in both Amish and non-Amish families. Here, we describe a 16-month old female from a small Mennonite community from Mexico, presenting with congenital hypotonia and dilated cardiomyopathy, with a novel homozygous deletion of 19q13.42 of about 11 kb in size, encompassing TNNT1 and TNNI3. Cardiomyopathy has not been observed in association with ANM in previous reports. Conversely, homozygous mutation in TNNI3 have been described with dilated cardiomyopathy. Our report underscores the consideration of contiguous gene deletion in children with ANM who present with congenital hypotonia and cardiomyopathy. The report also expands the known spectrum of non-Amish related ANM mutations to include homozygous multi-exonic TNNT1 deletion.
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Affiliation(s)
- Haley Streff
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Weimin Bi
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA; Baylor Genetics Laboratories, Houston, TX, 77030, USA
| | - Athos G Colón
- Department of Pediatrics, Texas Tech University School of Medicine, Lubbock, TX, 79430, USA
| | - Adekunle M Adesina
- Department of Pathology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Christina Y Miyake
- Division of Cardiology, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Seema R Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.
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14
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Huang K, Luo YE, Li QX, Duan HQ, Bi FF, Yang H, Luo YB. [Clinical, pathological and genetic studies of two cases of childhood-onset nemaline myopathy]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2018; 20:804-808. [PMID: 30369353 PMCID: PMC7389041 DOI: 10.7499/j.issn.1008-8830.2018.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 08/15/2018] [Indexed: 06/08/2023]
Abstract
This article reports two cases of childhood-onset nemaline myopathy diagnosed by muscle pathology and genetic diagnosis. The two patients had onset in early childhood, with muscle weakness as the first manifestation, as well as long disease duration and slow progression. Gomori staining and hematoxylin-eosin staining showed red-stained rods in the sarcoplasmic cytoplasm and sarcolemma under a light microscope. Electron microscopy showed that the dense nemaline rods were located under the muscle fiber sarcolemma and parallel to the long axis of the muscle fibers, and some muscle fiber myofilaments were dissolved and necrotic. Gene testing found that one of the two patients had heterozygous mutation (c.1013A>C) in the ACTA1 gene, and the other had compound heterozygous mutation (c.18676C>T and c.9812C>A) in the NEB gene. The two mutations were more common in nemaline myopathy. Nemaline myopathy is a recessive or dominant inheritance myopathy, in which the nemaline rod in the cytoplasm of myocytes is a characteristic muscle pathological change. Pathological and genetic diagnosis is the gold standard for diagnosis of nemaline myopathy.
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Affiliation(s)
- Kun Huang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410008, China.
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15
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Konersman CG, Freyermuth F, Winder TL, Lawlor MW, Lagier-Tourenne C, Patel SB. Novel autosomal dominant TNNT1 mutation causing nemaline myopathy. Mol Genet Genomic Med 2017; 5:678-691. [PMID: 29178646 PMCID: PMC5702563 DOI: 10.1002/mgg3.325] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/13/2017] [Accepted: 07/18/2017] [Indexed: 01/30/2023] Open
Abstract
Background Nemaline myopathy (NEM) is one of the three major forms of congenital myopathy and is characterized by diffuse muscle weakness, hypotonia, respiratory insufficiency, and the presence of nemaline rod structures on muscle biopsy. Mutations in troponin T1 (TNNT1) is 1 of 10 genes known to cause NEM. To date, only homozygous nonsense mutations or compound heterozygous truncating or internal deletion mutations in TNNT1 gene have been identified in NEM. This extended family is of historical importance as some members were reported in the 1960s as initial evidence that NEM is a hereditary disorder. Methods Proband and extended family underwent Sanger sequencing for TNNT1. We performed RT‐PCR and immunoblot on muscle to assess TNNT1 RNA expression and protein levels in proband and father. Results We report a novel heterozygous missense mutation of TNNT1 c.311A>T (p.E104V) that segregated in an autosomal dominant fashion in a large family residing in the United States. Extensive sequencing of the other known genes for NEM failed to identify any other mutant alleles. Muscle biopsies revealed a characteristic pattern of nemaline rods and severe myofiber hypotrophy that was almost entirely restricted to the type 1 fiber population. Conclusion This novel mutation alters a residue that is highly conserved among vertebrates. This report highlights not only a family with autosomal dominant inheritance of NEM, but that this novel mutation likely acts via a dominant negative mechanism.
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Affiliation(s)
- Chamindra G Konersman
- Department of Neurosciences, University of California San Diego, San Diego, California
| | - Fernande Freyermuth
- MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts.,Broad Institute of Harvard University and MIT, Cambridge, Massachusetts
| | | | - Michael W Lawlor
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine and Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Clotilde Lagier-Tourenne
- MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts.,Broad Institute of Harvard University and MIT, Cambridge, Massachusetts
| | - Shailendra B Patel
- Division of Endocrinology, Metabolism and Clinical Nutrition, Medical College of Wisconsin, and Clement J. Zablocki VAMC, Milwaukee, Wisconsin
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16
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Feng HZ, Jin JP. Carbonic Anhydrase III Is Expressed in Mouse Skeletal Muscles Independent of Fiber Type-Specific Myofilament Protein Isoforms and Plays a Role in Fatigue Resistance. Front Physiol 2016; 7:597. [PMID: 28018233 PMCID: PMC5156832 DOI: 10.3389/fphys.2016.00597] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 11/16/2016] [Indexed: 01/04/2023] Open
Abstract
Carbonic anhydrase III (CAIII) is a metabolic enzyme and a regulator for intracellular pH. CAIII has been reported with high level expression in slow twitch skeletal muscles. Here we demonstrate that CAIII is expressed in multiple slow and fast twitch muscles of adult mouse independent of the expression of myosin isoforms. Expressing similar fast type of myofilament proteins, CAIII-positive tibial anterior (TA) muscle exhibits higher tolerance to fatigue than that of CAIII-negative fast twitch extensor digitorum longus (EDL) muscle in in situ contractility studies. We further studied the muscles of CAIII knockout (Car3-KO) mice. The loss of CAIII in soleus and TA muscles in Car3-KO mice did not change muscle mass, sarcomere protein isoform contents, and the baseline twitch and tetanic contractility as compared with age-matched wild type (WT) controls. On the other hand, Car3-KO TA muscle showed faster force reduction at the beginning but higher resistance at the end during a fatigue test, followed by slower post fatigue recovery than that of WT TA muscle. Superfused Car3-KO soleus muscle also had faster total force reduction during fatigue test than that of WT soleus. However, it showed a less elevation of resting tension followed by a better post fatigue recovery under acidotic stress. CAIII was detected in neonatal TA and EDL muscle, downregulated during development, and then re-expressed in adult TA but not EDL muscles. The expression of CAIII in Tnnt1-KO myopathy mouse soleus muscle that has diminished slow fiber contents due to the loss of slow troponin T remained high. Car3-KO EDL, TA, and soleus muscles showed no change in the expression of mitochondria biomarker proteins. The data suggest a fiber type independent expression of CAIII with a role in the regulation of intracellular pH in skeletal muscle and may be explored as a target for improving fatigue resistance and for the treatment of TNNT1 myopathies.
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Affiliation(s)
- Han-Zhong Feng
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
| | - J-P Jin
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
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17
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Mondal A, Jin JP. Protein Structure-Function Relationship at Work: Learning from Myopathy Mutations of the Slow Skeletal Muscle Isoform of Troponin T. Front Physiol 2016; 7:449. [PMID: 27790152 PMCID: PMC5062619 DOI: 10.3389/fphys.2016.00449] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 09/20/2016] [Indexed: 12/03/2022] Open
Abstract
Troponin T (TnT) is the sarcomeric thin filament anchoring subunit of the troponin complex in striated muscles. A nonsense mutation in exon 11 of the slow skeletal muscle isoform of TnT (ssTnT) gene (TNNT1) was found in the Amish populations in Pennsylvania and Ohio. This single nucleotide substitution causes a truncation of the ssTnT protein at Glu180 and the loss of the C-terminal tropomyosin (Tm)-binding site 2. As a consequence, it abolishes the myofilament integration of ssTnT and the loss of function causes an autosomal recessive nemaline myopathy (NM). More TNNT1 mutations have recently been reported in non-Amish ethnic groups with similar recessive NM phenotypes. A nonsense mutation in exon 9 truncates ssTnT at Ser108, deleting Tm-binding site 2 and a part of the middle region Tm-binding site 1. Two splicing site mutations result in truncation of ssTnT at Leu203 or deletion of the exon 14-encoded C-terminal end segment. Another splicing mutation causes an internal deletion of the 39 amino acids encoded by exon 8, partially damaging Tm-binding site 1. The three splicing mutations of TNNT1 all preserve the high affinity Tm-binding site 2 but still present recessive NM phenotypes. The molecular mechanisms for these mutations to cause myopathy provide interesting models to study and understand the structure-function relationship of TnT. This focused review summarizes the current knowledge of TnT isoform regulation, structure-function relationship of TnT and how various ssTnT mutations cause recessive NM, in order to promote in depth studies for further understanding the pathogenesis and pathophysiology of TNNT1 myopathies toward the development of effective treatments.
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Affiliation(s)
- Anupom Mondal
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
| | - J-P Jin
- Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA
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