The Experts below are selected from a list of 2070 Experts worldwide ranked by ideXlab platform
J P Jin - One of the best experts on this subject based on the ideXlab platform.
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TNNT1 nemaline myopathy natural history and therapeutic frontier
Human Molecular Genetics, 2018Co-Authors: Hanzhong Feng, Michael D Fox, Vincent J Carson, Michael W Lawlor, John T Gray, Karlla W Brigatti, J P Jin, Kevin A StraussAbstract:We describe the natural history of ‘Amish’ nemaline myopathy (ANM), an infantile-onset, lethal disease linked to a pathogenic c.505G>T nonsense mutation of TNNT1, which encodes the slow fiber isoform of troponin T (TNNT1; a.k.a. TnT). The TNNT1 c.505G>T allele has a carrier frequency of 6.5% within Old Order Amish settlements of North America. We collected natural history data for 106 ANM patients born between 1923 and 2017. Over the last two decades, mean age of molecular diagnosis was 16 ± 27 days. TNNT1 c.505G>T homozygotes were normal weight at birth but failed to thrive by age 9 months. Presenting neonatal signs were axial hypotonia, hip and shoulder stiffness, and tremors, followed by progressive muscle weakness, atrophy and contractures. Affected children developed thoracic rigidity, pectus carinatum and restrictive lung disease during infancy, and all succumbed to respiratory failure by 6 years of age (median survival 18 months, range 0.2–66 months). Muscle histology from two affected children showed marked fiber size variation owing to both Type 1 myofiber smallness (hypotrophy) and Type 2 fiber hypertrophy, with evidence of nemaline rods, myofibrillar disarray and vacuolar pathology in both fiber types. The truncated slow TNNT1 (TnT) fragment (p.Glu180Ter) was undetectable in ANM muscle, reflecting its rapid proteolysis and clearance from sarcoplasm. Similar functional and histological phenotypes were observed in other human cohorts and two transgenic murine models (TNNT1−/− and TNNT1 c.505G>T). These findings have implications for emerging molecular therapies, including the suitably of TNNT1 gene replacement for newborns with ANM or other TNNT1-associated myopathies.
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functional basis of three new recessive mutations of slow skeletal muscle troponin t found in non amish TNNT1 nemaline myopathies
Biochemistry, 2016Co-Authors: Chinthaka Amarasinghe, Moazzem M Hossain, J P JinAbstract:Troponin T (TnT) is the tropomyosin (Tm)-binding and thin filament-anchoring subunit of troponin and plays a central role in striated muscle contraction. A nonsense mutation in exon 11 of the TNNT1 gene encoding slow skeletal muscle troponin T (ssTnT) truncating the polypeptide chain at Glu(180) causes a lethal recessive nemaline myopathy (NM) in the Amish (ANM). More TNNT1 NM mutations have been reported recently with similar recessive phenotypes. A nonsense mutation in exon 9 causes truncation at Ser(108), and a splicing site mutation causes truncation at Leu(203). Another splicing site mutation causes an internal deletion of the 39 exon 8-encoded amino acids. We engineered and characterized these ssTnT mutants to demonstrate that the Ser(108) truncation exhibits a Tm binding affinity lower than that of the ANM Glu(180) truncation, indicating a partial loss of Tm-binding site 1. Despite the presence of Tm-binding sites 1 and 2, ssTnT truncated at Leu(203) binds Tm with decreased affinity, consistent with its recessive NM phenotype and the requirement of troponin complex formation for high-affinity binding of TnT to Tm. The exon 8-deleted ssTnT has a partial loss of Tm-binding site 1 but retains high-affinity Tm-binding site 2. However, exon 8-deleted ssTnT exhibits a dramatically diminished Tm binding affinity, indicating a long-range conformational effect of this middle region deletion. Predicted from the TnT structure-function relationship, removal of the N-terminal variable region partially rescued this negative impact. These novel findings lay a foundation for understanding the pathogenesis of TNNT1 myopathies and provide insights into the development of targeted treatment.
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structural and functional impacts of novel mutations in slow skeletal muscle troponin t found in non amish TNNT1 nemaline myopathies
Biophysical Journal, 2016Co-Authors: Chinthaka Amarasinghe, J P JinAbstract:Troponin T (TnT) is the thin filament anchoring subunit of the troponin complex and has two tropomyosin-binding sites for the incorporation of troponin into the sarcomeric structure. A nonsense mutation in exon 11 of the slow skeletal muscle troponin T (ssTnT) gene (TNNT1) truncating the polypeptide chain at Glu180 was found to cause nemaline myopathy (NM) in the Amish, an autosomal recessive disease with severe lethal phenotype. More NM TNNT1 mutations have recently been reported with similar recessive phenotypes. Here we engineered protein constructs representing the mutant ssTnT to investigate their impact on tropomyosin-binding and integration into the thin filament regulatory system. Like the Glu180X mutation, two novel nonsense mutations in exon 9 and exon 11 truncate the ssTnT polypeptide chain at Ser108 and Leu203, respectively, to delete the C-terminal region tropomyosin-binding site 2. A splicing site mutation causes a deletion of a 39 amino acid segment from the middle region tropomyosin-binding site 1. To understand the molecular mechanisms underlying these TNNT1 mutations, we expressed and purified the mutant ssTnT proteins and analyzed their tropomyosin-binding affinity using solid-phase protein binding assays. The results demonstrate that both the Ser108X and exon 8 deletion mutations have similarly decreased tropomyosin-binding as that of Glu180X. We recently showed that the affinity of tropomyosin-binding site 1 is modulated by the isoform-specific N-terminal variable region, with ssTnT having the weakest tropomyosin-binding affinity. Therefore, the N-terminal variable region-based conformational and functional modulation may be a therapeutic target for TNNT1 myopathies. While Leu203X has both tropomyosin-binding sites intact, its recessive phenotype suggests that the incorporation into troponin complex may be required for high affinity binding of TnT to tropomyosin, which may be a protective mechanism against the Leu203X mutation.
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human slow troponin t TNNT1 pre mrna alternative splicing is an indicator of skeletal muscle response to resistance exercise in older adults
Journals of Gerontology Series A-biological Sciences and Medical Sciences, 2014Co-Authors: Tan Zhang, J P Jin, Seungjun Choi, Zhongmin Wang, Alexander Birbrair, Maria Laura Messi, Anthony P Marsh, Barbara J Nicklas, Osvaldo DelbonoAbstract:max. We propose that TNNT1 AS1, AS2 and the AS1/AS2 ratio are potential quantitative biomarkers of skeletal muscle adaptation to resistance training in older adults, and that their profile reflects enhanced single fiber muscle force in the absence of significant increases in fiber cross-sectional area.
Bruno Dallapiccola - One of the best experts on this subject based on the ideXlab platform.
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isolation and cloning by a polymerase chain reaction of a genomic dna fragment of the human slow skeletal troponin TNNT1 gene
Cell Biochemistry and Function, 1993Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Federica Sangiuolo, Lo S Cicero, L Dagruma, S Melchionda, Bruno DallapiccolaAbstract:The genomic 3' structure of the gene coding for the human slow skeletal troponin T (TNNT1) gene, is reported. An intron of 912 nucleotides containing an Alu-element has been identified and characterized. The complexity of the sequenced region suggests an alternative exon use. The present results may be valuable for further studies on the gene structure of TNNT1 and the related troponin gene family.
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polymerase chain reaction in the detection of mrna transcripts from the slow skeletal troponin t TNNT1 gene in myotonic dystrophy and normal muscle
Cell Biochemistry and Function, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, G Zelano, Federica Sangiuolo, Lo S Cicero, F Samson, Bruno DallapiccolaAbstract:Recent studies have shown that the gene encoding for the slow skeletal troponin isoform T (TNNT1) is located on the proximal long arm of human chromosome 19 in the myotonic dystrophy (DM) region. In order to test TNNT1 as a candidate gene for DM, we have isolated TNNT1 cDNA from skeletal muscle from two healthy individuals and from two patients with DM. Sequencing of the TNNT1 cDNA from the DM and normal muscle revealed two sequence variants but no transcriptionally significant mutations. This work rules out a defect in the coding segment of TNNT1 as a cause of DM and provides a polymerase chain reaction protocol for studying troponin T gene expression.
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Assignment of the slow troponin T (TNNT1) gene to chromosome 19 using polymerase chain reaction.
Human genetics, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Mariano Rocchi, Bruno DallapiccolaAbstract:Confirmation that the slow troponin (TNNT1) gene lies on chromosome 19 has been obtained by means of the polymerase chain reaction and somatic cell hybrids.
Giuseppe Novelli - One of the best experts on this subject based on the ideXlab platform.
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isolation and cloning by a polymerase chain reaction of a genomic dna fragment of the human slow skeletal troponin TNNT1 gene
Cell Biochemistry and Function, 1993Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Federica Sangiuolo, Lo S Cicero, L Dagruma, S Melchionda, Bruno DallapiccolaAbstract:The genomic 3' structure of the gene coding for the human slow skeletal troponin T (TNNT1) gene, is reported. An intron of 912 nucleotides containing an Alu-element has been identified and characterized. The complexity of the sequenced region suggests an alternative exon use. The present results may be valuable for further studies on the gene structure of TNNT1 and the related troponin gene family.
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polymerase chain reaction in the detection of mrna transcripts from the slow skeletal troponin t TNNT1 gene in myotonic dystrophy and normal muscle
Cell Biochemistry and Function, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, G Zelano, Federica Sangiuolo, Lo S Cicero, F Samson, Bruno DallapiccolaAbstract:Recent studies have shown that the gene encoding for the slow skeletal troponin isoform T (TNNT1) is located on the proximal long arm of human chromosome 19 in the myotonic dystrophy (DM) region. In order to test TNNT1 as a candidate gene for DM, we have isolated TNNT1 cDNA from skeletal muscle from two healthy individuals and from two patients with DM. Sequencing of the TNNT1 cDNA from the DM and normal muscle revealed two sequence variants but no transcriptionally significant mutations. This work rules out a defect in the coding segment of TNNT1 as a cause of DM and provides a polymerase chain reaction protocol for studying troponin T gene expression.
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Assignment of the slow troponin T (TNNT1) gene to chromosome 19 using polymerase chain reaction.
Human genetics, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Mariano Rocchi, Bruno DallapiccolaAbstract:Confirmation that the slow troponin (TNNT1) gene lies on chromosome 19 has been obtained by means of the polymerase chain reaction and somatic cell hybrids.
Sanam Shafaattalab - One of the best experts on this subject based on the ideXlab platform.
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in vitro analyses of suspected arrhythmogenic thin filament variants as a cause of sudden cardiac death in infants
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Sanam Shafaattalab, Eric Lin, Charles M Stevens, Laura J Dewar, Francis C Lynn, Shubhayan Sanatani, Zachary LaksmanAbstract:Sudden unexpected death of an infant (SUDI) is a devastating occurrence for families. To investigate the genetic pathogenesis of SUDI, we sequenced >70 genes from 191 autopsy-negative SUDI victims. Ten infants sharing a previously unknown variant in troponin I (TnI) were identified. The mutation (TNNI1 R37C+/−) is in the fetal/neonatal paralog of TnI, a gene thought to be expressed in the heart up to the first 24 months of life. Using phylogenetic analysis and molecular dynamics simulations, it was determined that arginine at residue 37 in TNNI1 may play a critical functional role, suggesting that the variant may be pathogenic. We investigated the biophysical properties of the TNNI1 R37C mutation in human reconstituted thin filaments (RTFs) using fluorometry. RTFs reconstituted with the mutant R37C TnI exhibited reduced Ca2+-binding sensitivity due to an increased Ca2+ off-rate constant. Furthermore, we generated TNNI1 R37C+/− mutants in human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) using CRISPR-Cas9. In monolayers of hiPSC-CMs, we simultaneously monitored voltage and Ca2+ transients through optical mapping and compared them to their isogenic controls. We observed normal intrinsic beating patterns under control conditions in TNNI1 R37C+/− at stimulation frequencies of 55 beats/min (bpm), but these cells showed no restitution with increased stimulation frequency to 65 bpm and exhibited alternans at >75 bpm. The WT hiPSC-CMs did not exhibit any sign of arrhythmogenicity even at stimulation frequencies of 120 bpm. The approach used in this study provides critical physiological and mechanistic bases to investigate sarcomeric mutations in the pathogenesis of SUDI.
Massimo Gennarelli - One of the best experts on this subject based on the ideXlab platform.
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isolation and cloning by a polymerase chain reaction of a genomic dna fragment of the human slow skeletal troponin TNNT1 gene
Cell Biochemistry and Function, 1993Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Federica Sangiuolo, Lo S Cicero, L Dagruma, S Melchionda, Bruno DallapiccolaAbstract:The genomic 3' structure of the gene coding for the human slow skeletal troponin T (TNNT1) gene, is reported. An intron of 912 nucleotides containing an Alu-element has been identified and characterized. The complexity of the sequenced region suggests an alternative exon use. The present results may be valuable for further studies on the gene structure of TNNT1 and the related troponin gene family.
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polymerase chain reaction in the detection of mrna transcripts from the slow skeletal troponin t TNNT1 gene in myotonic dystrophy and normal muscle
Cell Biochemistry and Function, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, G Zelano, Federica Sangiuolo, Lo S Cicero, F Samson, Bruno DallapiccolaAbstract:Recent studies have shown that the gene encoding for the slow skeletal troponin isoform T (TNNT1) is located on the proximal long arm of human chromosome 19 in the myotonic dystrophy (DM) region. In order to test TNNT1 as a candidate gene for DM, we have isolated TNNT1 cDNA from skeletal muscle from two healthy individuals and from two patients with DM. Sequencing of the TNNT1 cDNA from the DM and normal muscle revealed two sequence variants but no transcriptionally significant mutations. This work rules out a defect in the coding segment of TNNT1 as a cause of DM and provides a polymerase chain reaction protocol for studying troponin T gene expression.
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Assignment of the slow troponin T (TNNT1) gene to chromosome 19 using polymerase chain reaction.
Human genetics, 1992Co-Authors: Giuseppe Novelli, Massimo Gennarelli, Mariano Rocchi, Bruno DallapiccolaAbstract:Confirmation that the slow troponin (TNNT1) gene lies on chromosome 19 has been obtained by means of the polymerase chain reaction and somatic cell hybrids.