{"gene":"TNNT2","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":1994,"finding":"TNNT2 encodes cardiac troponin T, a component of the thin filament troponin complex; the gene undergoes alternative splicing in the 5' coding region to produce multiple fetal isoforms in human fetal heart, and was mapped to chromosome 1q by somatic cell hybrid analysis.","method":"cDNA cloning, alternative splicing analysis, somatic cell hybrid mapping","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1-2 — direct molecular cloning and genomic mapping with functional isoform characterization","pmids":["8088824"],"is_preprint":false},{"year":2004,"finding":"A 5-bp insertion/deletion polymorphism in intron 3 of TNNT2 affects alternative splicing, causing skipping of exon 4; the deletion allele was associated with larger left ventricular mass in HCM patients, demonstrated by in vitro expression studies.","method":"In vitro expression/splicing assay, population genetics, clinical echocardiography","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro splicing assay plus clinical association, single lab","pmids":["14986170"],"is_preprint":false},{"year":2009,"finding":"TNNT2 missense mutations (Arg134Gly, Arg151Cys, Arg159Gln, Arg205Trp, Lys210del) associated with DCM cause decreased Ca2+ sensitivity of force development in cardiac myocytes reconstituted with mutant troponin T proteins, establishing a pathophysiological mechanism for DCM.","method":"Reconstituted cardiac myocyte force-Ca2+ measurement with mutant troponin T proteins","journal":"Circulation. Cardiovascular genetics","confidence":"High","confidence_rationale":"Tier 1 — direct functional reconstitution assay with multiple mutations, clinical correlation","pmids":["20031601"],"is_preprint":false},{"year":2010,"finding":"The rat Tnnt2 promoter drives cardiomyocyte-specific expression; an inducible Tnnt2-rtTA;TetO-Cre system achieves specific and robust Cre recombinase expression in cardiomyocytes of embryonic and adult mouse hearts following doxycycline induction, enabling cardiomyocyte-specific gene disruption.","method":"Transgenic mouse generation, Cre reporter lines, cardiac-specific gene disruption","journal":"Genesis","confidence":"High","confidence_rationale":"Tier 2 — direct in vivo validation with two reporter lines; widely replicated tool paper","pmids":["20014345"],"is_preprint":false},{"year":2010,"finding":"The TNNT2 pE96K missense mutation causes impaired left ventricular function and induction of heart failure marker genes in transgenic mice, demonstrating intrinsic cardiomyocyte dysfunction independent of a non-compaction phenotype.","method":"Transgenic mouse model, echocardiography, histology, gene expression analysis","journal":"Cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 — clean transgenic model with functional cardiac phenotyping, single lab","pmids":["20083571"],"is_preprint":false},{"year":2018,"finding":"Cells of the Tnnt2-Cre lineage (myocardial lineage) populate the intercalated cushions of the outflow tract that give rise to the anterior pulmonary valve cusp and non-coronary aortic valve cusp; these cells express mesenchymal markers Sox9 and versican without expressing Tnnt2 mRNA or protein, revealing a previously unrecognized myocardial-to-mesenchymal contribution to valve development.","method":"Cre-based lineage tracing with Rosa TdTomato-EGFP reporter, 3D imaging, immunostaining","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 — direct lineage tracing with multiple Cre drivers and reporter confirmation, single lab","pmids":["29920846"],"is_preprint":false},{"year":2019,"finding":"Tnnt2a is expressed not only in myocardial cells but also in a novel group of smooth muscle cells on the outflow tract (OFT); restoring tnnt2a expression in both myocardial and OFT cells (but not myocardium alone) rescues cardiac function and circulation in tnnt2a-null zebrafish, demonstrating an essential role of Tnnt2 in OFT mechanical dynamics.","method":"CRISPR/Cas9 knockout zebrafish, conditional rescue with tissue-specific promoters, RNA-seq, immunofluorescence","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 — genetic rescue experiment with multiple tissue-specific rescue conditions, RNA-seq, single lab","pmids":["31796423"],"is_preprint":false},{"year":2019,"finding":"DYRK1A regulates the alternative splicing of TNNT2 through phosphorylation of the splicing factor SRSF6; elevated phosphorylated SRSF6 in trisomy 21 myocardium correlates with increased expression of fetal TNNT2 isoforms, and TNNT2 missplicing correlates with QRS cardiac parameters in DM1 patients.","method":"Western blotting, RT-PCR splicing analysis, immunohistochemistry in human myocardial tissue","journal":"Experimental and molecular pathology","confidence":"Medium","confidence_rationale":"Tier 3 — pathway established by correlative molecular analysis in human tissue with multiple biomarkers, replicated across DM1/DM2 cohorts","pmids":["31201803"],"is_preprint":false},{"year":2020,"finding":"HCM-associated TNNT2 variants increase cardiac microtissue contraction and myofilament calcium affinity, while DCM-associated TNNT2 variants decrease contraction and myofilament calcium affinity; these sarcomere contractile changes induce graded transcriptomic responses including MAPK targets, HOPX, and NPPB in human iPSC-derived cardiomyocytes.","method":"CRISPR/Cas9 hiPSC engineering, cardiac microtissue contraction assay, thin filament calcium reporter, RNA sequencing, NPPB-tdTomato reporter","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal functional assays in isogenic human cell systems across 51 variants","pmids":["33025817"],"is_preprint":false},{"year":2021,"finding":"The HCM-associated TNNT2 I79N variant increases myofilament Ca2+ sensitivity and decreases Ca2+ off-rate (koff) in reconstituted human cardiac thin filaments; in CRISPR/Cas9-engineered heterozygous I79N hiPSC-CMs, enhanced Ca2+ buffering reduced intracellular Ca2+ transients, caused beat-to-beat instability and action potential triangulation, and induced alternans at elevated pacing rates, revealing a pro-arrhythmic mechanism.","method":"Reconstituted thin filament stopped-flow fluorescence, CRISPR/Cas9 hiPSC-CMs, voltage/Ca2+ imaging, transcriptomics","journal":"Frontiers in cell and developmental biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution combined with isogenic hiPSC-CM functional studies, multiple orthogonal methods","pmids":["34977031"],"is_preprint":false},{"year":2021,"finding":"XIN protein expression is reduced in TNNT2-ΔK210 cardiomyocytes and mouse hearts; overexpression of XINB isoform decreases myofilament disorganization, increases cell contractility, and ameliorates DCM remodeling (cardiac dilation, systolic dysfunction, fibrosis) in TNNT2-ΔK210 mice via AAV9 delivery.","method":"hESC-derived cardiomyocytes, transgenic mice, AAV9 cardiac overexpression, echocardiography, histology","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo AAV rescue experiment with functional cardiac readouts, single lab","pmids":["34222259"],"is_preprint":false},{"year":2022,"finding":"The TNNT2 K280N mutation increases myofilament Ca2+ sensitivity independent of phosphorylation status (not corrected by alkaline phosphatase or PKA treatment); as little as 14% mutant cTnT-K280N in troponin exchange experiments is sufficient to increase Ca2+ sensitivity; hiPSC-CMs with heterozygous or homozygous K280N show elevated diastolic Ca2+, increased contractility, and impaired relaxation (dose-dependent).","method":"Force measurements in isolated cardiomyocytes, alkaline phosphatase/PKA treatment, troponin exchange, CRISPR/Cas9 isogenic hiPSC-CMs, Ca2+ transient and cell shortening assays","journal":"Journal of molecular and cellular cardiology plus","confidence":"High","confidence_rationale":"Tier 1 — reconstitution (troponin exchange) plus isogenic hiPSC-CMs with multiple orthogonal functional assays","pmids":["37159677"],"is_preprint":false},{"year":2022,"finding":"The TNNT2 Δ160E mutation causes prolonged calcium decay, relaxation impairment, and hypertrophy in hiPSC-CMs in a gene-dosage dependent manner; the mutant protein causes sarcomeric calcium retention, activates NFATc1 nuclear translocation and CaMKIIδ/phospholamban phosphorylation; epigallocatechin-3-gallate (calcium desensitizer) rescues the calcium and relaxation phenotype.","method":"CRISPR/Cas9 isogenic iPSC-CMs (heterozygous, homozygous, corrected), Ca2+ imaging with R-GECO-fused mutant cTnT, high-content NFATc1 imaging, western blotting for CaMKIIδ/phospholamban, drug rescue","journal":"Circulation. Genomic and precision medicine","confidence":"High","confidence_rationale":"Tier 1-2 — isogenic hiPSC-CMs with multiple orthogonal mechanistic readouts and pharmacological rescue","pmids":["35861968"],"is_preprint":false},{"year":2022,"finding":"Specific TNNT2 HCM mutations (R92Q) increase atrial myofilament calcium sensitivity, reduce inotropic reserve, slow twitch kinetics, and directly promote spontaneous beats and triggered contractions in atrial trabeculae, providing a genotype-specific arrhythmogenic mechanism for atrial fibrillation; E163R mutation instead increases tension cost without causing atrial arrhythmias.","method":"Mouse HCM models (R92Q and E163R), ex vivo atrial trabecula mechanics, ATPase measurements, echocardiography","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 2 — direct ex vivo functional studies in two genetically distinct mouse models with mechanistic comparison","pmids":["35514357"],"is_preprint":false},{"year":2022,"finding":"DYRK1A overexpression in iPSC-derived cardiomyocytes increases TNNT2 fetal splice variant abundance (~58% increase) and decreases the adult cTnT3 variant (~27% decrease) by increasing SRSF6 phosphorylation (~25-65%), establishing the DYRK1A→SRSF6→TNNT2 splicing pathway in human cardiomyocytes.","method":"DYRK1A overexpression in hiPSC-CMs, RT-PCR for splice variants, western blotting for phospho-SRSF6","journal":"Cardiovascular toxicology","confidence":"Medium","confidence_rationale":"Tier 2 — direct gain-of-function experiment with molecular readouts in human cardiomyocytes, single lab","pmids":["35596909"],"is_preprint":false},{"year":2023,"finding":"TNNT2 physically interacts with EGFR protein in colorectal cancer cells (co-immunoprecipitation); TNNT2 overexpression upregulates EGFR and HER2, decreases E-cadherin, increases Vimentin and N-cadherin (EMT markers), and promotes proliferation, migration, and invasion, suggesting a non-sarcomeric role via EGFR/HER2/EMT signaling.","method":"Co-immunoprecipitation, western blotting, CCK-8, colony formation, Transwell assays, qPCR in CRC cell lines","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 — single co-IP plus overexpression/knockdown in cancer cells; non-canonical context, single lab","pmids":["37481519"],"is_preprint":false},{"year":2024,"finding":"The HCM-causative TNNT2 R92L mutation allosterically repositions the N-terminus of cTnI closer to cTnC (measured by TR-FRET), creates additional electrostatic interactions at the PKA consensus sequence, reduces cTnI phosphorylation, and causes early-onset diastolic dysfunction; constitutive phosphomimetic cTnI (D23D24) recovers diastolic function specifically for R92L-cTnT, identifying impaired PKA accessibility as the mechanism.","method":"In vivo mouse model, ex vivo hemodynamics, western blotting, stopped-flow kinetics, TR-FRET, molecular dynamics simulations, constitutive phosphomimetic cTnI rescue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1-2 — multiple orthogonal structural/functional methods in vivo and in vitro; preprint not yet peer-reviewed","pmids":["37503299"],"is_preprint":true},{"year":2024,"finding":"The TNNT2 R141W mutation disrupts a salt bridge between TNNT2 and E-257 of tropomyosin (3D structural modeling), reducing cardiac contraction; nuclear TNNT2 functions as an HDAC1 sponge in cardiomyocytes, and the R141W mutant has compromised HDAC1 association, causing epigenetic perturbation and transcriptional dysregulation including downregulation of cardiac muscular genes and upregulation of TGFβ signaling and EZH2; simvastatin restores nuclear TNNT2(R141W)-HDAC1 association and recovers cardiac function.","method":"Knock-in mice (Tnnt2 R154W), iPSC-derived cardiomyocytes from LVNC patients, 3D protein modeling, co-IP (TNNT2-HDAC1), omics, drug screening, in vivo cardiac functional assessment","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP, knock-in mouse model, patient iPSC-CMs, and pharmacological rescue; preprint","pmids":["bio_10.1101_2024.10.09.24314670"],"is_preprint":true},{"year":2026,"finding":"The DCM-causing TNNT2 R151W mutation causes sarcomere disarray, attenuated Ca2+ transient amplitude, prolonged time to Ca2+ peak, and delayed Ca2+ decay tau in iPSC-CMs; in pillar-based engineered heart tissue, R151W substantially decreases contractile force; overexpression of wild-type TNNT2 in patient iPSCs rescues sarcomere organization, Ca2+ handling, and contractile force, demonstrating that sarcomere insufficiency and Ca2+ handling disturbance are the primary disease mechanism.","method":"Patient-derived iPSC-CMs, isogenic WT TNNT2 overexpression rescue, pillar-based engineered heart tissue (EHT) contractile force assay, Ca2+ imaging, sarcomere immunofluorescence","journal":"Bioengineering & translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 — patient-derived and rescued isogenic EHT with multiple orthogonal functional assays, single lab","pmids":["42016857"],"is_preprint":false}],"current_model":"TNNT2 encodes cardiac troponin T, a thin-filament protein that regulates Ca2+-dependent actomyosin interaction; its alternative splicing is controlled by the DYRK1A→SRSF6 kinase-splicing axis, and disease-causing mutations (HCM or DCM) alter myofilament Ca2+ sensitivity and contractile force in opposite directions—HCM variants increase and DCM variants decrease Ca2+ sensitivity and contraction—with downstream consequences including transcriptomic remodeling via MAPK/NPPB pathways, altered Ca2+ handling and arrhythmogenesis, nuclear lamina remodeling, and (for certain mutations) disruption of a nuclear HDAC1-sponge function that causes epigenetic perturbation in cardiomyocytes."},"narrative":{"teleology":[{"year":1994,"claim":"Establishing the identity of TNNT2 as the cardiac troponin T gene resolved which thin-filament component was heart-specific and revealed that developmental alternative splicing generates multiple fetal isoforms.","evidence":"cDNA cloning, alternative splicing analysis, and somatic cell hybrid mapping of human fetal heart","pmids":["8088824"],"confidence":"High","gaps":["Functional consequences of individual fetal vs. adult isoforms not determined","Splicing regulatory mechanism unknown"]},{"year":2004,"claim":"Identification of an intronic polymorphism that controls exon 4 skipping demonstrated that TNNT2 splicing variation has clinical consequences, linking isoform composition to left ventricular mass in HCM patients.","evidence":"In vitro splicing assay of 5-bp indel in intron 3 combined with echocardiographic association in HCM cohort","pmids":["14986170"],"confidence":"Medium","gaps":["Mechanistic basis of how exon 4 inclusion alters cardiac function not established","Association study in single cohort"]},{"year":2009,"claim":"Reconstitution of DCM-associated TNNT2 mutations into cardiac myocytes established that decreased Ca²⁺ sensitivity of force is the unifying biophysical defect in DCM-causing variants, providing the first systematic functional classification of TNNT2 mutations.","evidence":"Force–Ca²⁺ measurements in cardiac myocytes reconstituted with five different DCM-associated mutant troponin T proteins","pmids":["20031601"],"confidence":"High","gaps":["Whether decreased Ca²⁺ sensitivity alone is sufficient for DCM in vivo was untested","Downstream transcriptomic consequences unknown"]},{"year":2010,"claim":"Two studies—a cardiomyocyte-specific inducible Cre tool and a pE96K transgenic model—validated that TNNT2 promoter activity is cardiomyocyte-specific and that single TNNT2 mutations are sufficient to cause intrinsic contractile dysfunction and heart failure gene induction in vivo.","evidence":"Transgenic mouse with Tnnt2-rtTA;TetO-Cre validated with Cre reporters; Tnnt2 pE96K transgenic mice with echocardiography and gene expression analysis","pmids":["20014345","20083571"],"confidence":"High","gaps":["Mechanism linking pE96K to contractile dysfunction not resolved at the molecular level"]},{"year":2018,"claim":"Lineage tracing revealed that Tnnt2-expressing myocardial progenitors contribute to outflow tract valve mesenchyme through a myocardial-to-mesenchymal transition, expanding TNNT2's developmental role beyond sarcomeric function.","evidence":"Cre-based lineage tracing with Rosa TdTomato-EGFP reporter and 3D imaging in mouse embryos","pmids":["29920846"],"confidence":"Medium","gaps":["Whether TNNT2 mutations affect valve development through this lineage is unknown","Lineage contribution quantified in mouse only"]},{"year":2019,"claim":"Two advances defined upstream regulatory and non-cardiac roles: DYRK1A phosphorylation of SRSF6 was identified as the kinase pathway controlling TNNT2 fetal-to-adult isoform switching, and Tnnt2a was shown to be essential in outflow tract smooth muscle cells for cardiac output in zebrafish.","evidence":"DYRK1A→SRSF6→TNNT2 splicing analysis in trisomy 21 and DM1 human myocardium; CRISPR knockout and tissue-specific rescue of tnnt2a in zebrafish","pmids":["31201803","31796423"],"confidence":"Medium","gaps":["Whether DYRK1A pathway directly binds TNNT2 pre-mRNA cis-elements is unknown","OFT smooth muscle role not confirmed in mammalian systems"]},{"year":2020,"claim":"A comprehensive survey of 51 TNNT2 variants in isogenic hiPSC-CMs established that HCM mutations increase and DCM mutations decrease microtissue contraction and Ca²⁺ affinity in a graded manner, with contractile changes driving downstream transcriptomic remodeling via MAPK and NPPB pathways.","evidence":"CRISPR/Cas9 isogenic hiPSC-CM panel, cardiac microtissue contraction, thin filament Ca²⁺ reporter, RNA-seq, NPPB-tdTomato reporter","pmids":["33025817"],"confidence":"High","gaps":["Whether graded transcriptomic remodeling occurs in adult human heart tissue in vivo is untested","Specific MAPK effectors mediating remodeling not identified"]},{"year":2021,"claim":"Detailed biophysical and cellular studies of specific HCM mutations (I79N, K280N) revealed that increased Ca²⁺ sensitivity operates through decreased Ca²⁺ off-rate from thin filaments, causing Ca²⁺ buffering defects, beat-to-beat instability, and dose-dependent diastolic dysfunction—mechanisms that explain arrhythmogenesis at the single-cell level.","evidence":"Stopped-flow fluorescence on reconstituted thin filaments; isogenic CRISPR hiPSC-CMs with voltage/Ca²⁺ imaging and troponin exchange experiments","pmids":["34977031","37159677"],"confidence":"High","gaps":["Whether these kinetic defects can be pharmacologically targeted at the thin filament level in vivo","Contribution of heterozygous vs. homozygous mutant incorporation ratios in patient hearts unknown"]},{"year":2022,"claim":"Multiple studies converged on mutation-specific mechanistic details: Δ160E was shown to activate CaMKIIδ and NFATc1 hypertrophic signaling from sarcomeric Ca²⁺ retention; R92Q was identified as a genotype-specific atrial arrhythmia driver; DYRK1A→SRSF6→TNNT2 splicing was validated by gain-of-function in human cardiomyocytes; and XIN (XINB) was identified as a downstream effector whose loss contributes to ΔK210 DCM remodeling.","evidence":"CRISPR isogenic iPSC-CMs with Ca²⁺-fused mutant cTnT and EGCG rescue; ex vivo atrial trabeculae from R92Q/E163R mice; DYRK1A overexpression in hiPSC-CMs; AAV9-XINB rescue in ΔK210 mice","pmids":["35861968","35514357","35596909","34222259"],"confidence":"High","gaps":["Whether CaMKIIδ/NFAT activation is a general feature of all HCM mutations or Δ160E-specific","XIN mechanism of sarcomere stabilization not defined"]},{"year":2024,"claim":"Two preprints identified novel mechanistic layers: R92L allosterically repositions cTnI to block PKA phosphorylation as the basis for diastolic dysfunction (rescued by phosphomimetic cTnI), and R141W disrupts a nuclear TNNT2–HDAC1 sponge interaction, causing epigenetic perturbation rescued by simvastatin, revealing an unexpected non-sarcomeric nuclear function.","evidence":"(preprint) TR-FRET, molecular dynamics, phosphomimetic cTnI rescue in R92L mice; (preprint) knock-in mice, patient iPSC-CMs, co-IP TNNT2-HDAC1, drug screening","pmids":["37503299","bio_10.1101_2024.10.09.24314670"],"confidence":"Medium","gaps":["Both findings are preprints awaiting peer review","Nuclear HDAC1-sponge function not confirmed by independent labs","Structural basis of TNNT2-HDAC1 interaction not defined","Whether PKA accessibility defect applies to other HCM mutations is unknown"]},{"year":2026,"claim":"Wild-type TNNT2 overexpression rescue in patient-derived iPSC-CMs and engineered heart tissues demonstrated that sarcomere insufficiency and Ca²⁺ handling disturbance are the primary, correctable disease mechanism in DCM caused by R151W.","evidence":"Patient iPSC-CMs with WT TNNT2 overexpression, pillar-based EHT contractile force assay, Ca²⁺ imaging","pmids":["42016857"],"confidence":"Medium","gaps":["Whether gene supplementation is therapeutic in vivo remains untested","Stoichiometric effects of overexpression on troponin complex assembly not evaluated"]},{"year":null,"claim":"Key unresolved questions include the structural basis and generality of TNNT2's nuclear HDAC1-sponge function, whether distinct HCM mutations share the PKA accessibility defect or each operates through unique allosteric mechanisms, and how fetal-to-adult isoform switching is integrated with developmental and disease-related sarcomere remodeling in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of full-length cTnT in complex with HDAC1","No in vivo gene therapy trial for TNNT2 cardiomyopathy","Contribution of individual splice isoforms to adult cardiac function not dissected in human"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,2,8,9,11]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[2,8,9,11,12]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[17]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,2,8,9,11,12,18]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[17]}],"pathway":[{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[0,2,8,9,11,13,18]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,4,8,9,12,13,18]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[1,7,14]}],"complexes":["cardiac troponin complex (cTnT–cTnI–cTnC)","thin filament (troponin–tropomyosin–actin)"],"partners":["TNNC1","TNNI3","TPM1","SRSF6","HDAC1","XIRP2"],"other_free_text":[]},"mechanistic_narrative":"TNNT2 encodes cardiac troponin T (cTnT), a core component of the thin-filament troponin complex that governs Ca²⁺-dependent regulation of actomyosin interaction and sarcomere contraction in cardiomyocytes [PMID:8088824]. The gene undergoes developmental alternative splicing—controlled by the DYRK1A→SRSF6 phosphorylation axis—to produce fetal and adult isoforms with distinct functional properties [PMID:8088824, PMID:35596909]. Disease-causing missense mutations partition into two mechanistic classes: HCM-associated variants (e.g., R92Q, I79N, K280N, Δ160E) increase myofilament Ca²⁺ sensitivity, impair relaxation, and promote arrhythmogenesis through enhanced Ca²⁺ buffering and signaling via CaMKIIδ/NFAT pathways, whereas DCM-associated variants (e.g., R134G, R151C, R205W, ΔK210, R151W) decrease Ca²⁺ sensitivity and contractile force, with wild-type TNNT2 overexpression rescuing the phenotype [PMID:20031601, PMID:33025817, PMID:34977031, PMID:35861968, PMID:42016857]. Beyond its sarcomeric role, TNNT2 localizes to cardiomyocyte nuclei where it sequesters HDAC1, and disruption of this interaction by the R141W mutation causes epigenetic perturbation and transcriptional dysregulation [PMID:bio_10.1101_2024.10.09.24314670]."},"prefetch_data":{"uniprot":{"accession":"P45379","full_name":"Troponin T, cardiac muscle","aliases":["Cardiac muscle troponin T","cTnT"],"length_aa":298,"mass_kda":35.9,"function":"Troponin T is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex which confers calcium-sensitivity to striated muscle actomyosin ATPase activity","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P45379/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/TNNT2","classification":"Common Essential","n_dependent_lines":394,"n_total_lines":1208,"dependency_fraction":0.326158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TNNT2","total_profiled":1310},"omim":[{"mim_id":"621216","title":"PLAQUE-ENRICHED LONG NONCODING RNA IN ATHEROSCLEROTIC AND INFLAMMATORY BOWEL MACROPHAGE REGULATION; PELATON","url":"https://www.omim.org/entry/621216"},{"mim_id":"615396","title":"LEFT VENTRICULAR NONCOMPACTION 10; LVNC10","url":"https://www.omim.org/entry/615396"},{"mim_id":"613874","title":"CARDIOMYOPATHY, FAMILIAL HYPERTROPHIC, 18; CMH18","url":"https://www.omim.org/entry/613874"},{"mim_id":"613251","title":"CARDIOMYOPATHY, FAMILIAL HYPERTROPHIC, 14; CMH14","url":"https://www.omim.org/entry/613251"},{"mim_id":"612681","title":"CUGBP- AND ELAV-LIKE FAMILY, MEMBER 6; CELF6","url":"https://www.omim.org/entry/612681"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Nucleoli","reliability":"Uncertain"},{"location":"Focal adhesion sites","reliability":"Additional"},{"location":"Microtubules","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":8731.9}],"url":"https://www.proteinatlas.org/search/TNNT2"},"hgnc":{"alias_symbol":["CMPD2"],"prev_symbol":["CMH2","CMD1D"]},"alphafold":{"accession":"P45379","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P45379","model_url":"https://alphafold.ebi.ac.uk/files/AF-P45379-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P45379-F1-predicted_aligned_error_v6.png","plddt_mean":78.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TNNT2","jax_strain_url":"https://www.jax.org/strain/search?query=TNNT2"},"sequence":{"accession":"P45379","fasta_url":"https://rest.uniprot.org/uniprotkb/P45379.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P45379/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P45379"}},"corpus_meta":[{"pmid":"19412328","id":"PMC_19412328","title":"Coding sequence mutations identified in MYH7, TNNT2, SCN5A, CSRP3, LBD3, and TCAP from 313 patients with familial or idiopathic dilated cardiomyopathy.","date":"2008","source":"Clinical and translational science","url":"https://pubmed.ncbi.nlm.nih.gov/19412328","citation_count":158,"is_preprint":false},{"pmid":"20031601","id":"PMC_20031601","title":"Clinical and functional characterization of TNNT2 mutations identified in patients with dilated cardiomyopathy.","date":"2009","source":"Circulation. Cardiovascular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20031601","citation_count":93,"is_preprint":false},{"pmid":"8088824","id":"PMC_8088824","title":"Human cardiac troponin T: identification of fetal isoforms and assignment of the TNNT2 locus to chromosome 1q.","date":"1994","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8088824","citation_count":67,"is_preprint":false},{"pmid":"20083571","id":"PMC_20083571","title":"Severe familial left ventricular non-compaction cardiomyopathy due to a novel troponin T (TNNT2) mutation.","date":"2010","source":"Cardiovascular research","url":"https://pubmed.ncbi.nlm.nih.gov/20083571","citation_count":58,"is_preprint":false},{"pmid":"19150014","id":"PMC_19150014","title":"[Mutations in sarcomeric genes MYH7, MYBPC3, TNNT2, TNNI3, and TPM1 in patients with hypertrophic cardiomyopathy].","date":"2009","source":"Revista espanola de cardiologia","url":"https://pubmed.ncbi.nlm.nih.gov/19150014","citation_count":58,"is_preprint":false},{"pmid":"12881443","id":"PMC_12881443","title":"Hypertrophic cardiomyopathy: low frequency of mutations in the beta-myosin heavy chain (MYH7) and cardiac troponin T (TNNT2) genes among Spanish patients.","date":"2003","source":"Clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12881443","citation_count":57,"is_preprint":false},{"pmid":"33025817","id":"PMC_33025817","title":"Development of a Cardiac Sarcomere Functional Genomics Platform to Enable Scalable Interrogation of Human TNNT2 Variants.","date":"2020","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/33025817","citation_count":49,"is_preprint":false},{"pmid":"24093860","id":"PMC_24093860","title":"Screening of MYH7, MYBPC3, and TNNT2 genes in Brazilian patients with hypertrophic cardiomyopathy.","date":"2013","source":"American heart journal","url":"https://pubmed.ncbi.nlm.nih.gov/24093860","citation_count":45,"is_preprint":false},{"pmid":"29920846","id":"PMC_29920846","title":"Intercalated cushion cells within the cardiac outflow tract are derived from the myocardial troponin T type 2 (Tnnt2) Cre lineage.","date":"2018","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/29920846","citation_count":34,"is_preprint":false},{"pmid":"20014345","id":"PMC_20014345","title":"Inducible cardiomyocyte-specific gene disruption directed by the rat Tnnt2 promoter in the mouse.","date":"2010","source":"Genesis (New York, N.Y. : 2000)","url":"https://pubmed.ncbi.nlm.nih.gov/20014345","citation_count":29,"is_preprint":false},{"pmid":"14986170","id":"PMC_14986170","title":"The role of a common TNNT2 polymorphism in cardiac hypertrophy.","date":"2004","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14986170","citation_count":27,"is_preprint":false},{"pmid":"28642161","id":"PMC_28642161","title":"Digenic inheritance of mutations in the cardiac troponin (TNNT2) and cardiac beta myosin heavy chain (MYH7) as the cause of severe dilated cardiomyopathy.","date":"2017","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28642161","citation_count":27,"is_preprint":false},{"pmid":"32290750","id":"PMC_32290750","title":"Increased Myocardial Oxygen Consumption Precedes Contractile Dysfunction in Hypertrophic Cardiomyopathy Caused by Pathogenic TNNT2 Gene Variants.","date":"2020","source":"Journal of the American Heart Association","url":"https://pubmed.ncbi.nlm.nih.gov/32290750","citation_count":24,"is_preprint":false},{"pmid":"24037902","id":"PMC_24037902","title":"The genetics of dilated cardiomyopathy: a prioritized candidate gene study of LMNA, TNNT2, TCAP, and PLN.","date":"2013","source":"Clinical cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/24037902","citation_count":22,"is_preprint":false},{"pmid":"23782526","id":"PMC_23782526","title":"Somatic MYH7, MYBPC3, TPM1, TNNT2 and TNNI3 mutations in sporadic hypertrophic cardiomyopathy.","date":"2013","source":"Circulation journal : official journal of the Japanese Circulation Society","url":"https://pubmed.ncbi.nlm.nih.gov/23782526","citation_count":20,"is_preprint":false},{"pmid":"34977031","id":"PMC_34977031","title":"Mechanisms of Arrhythmogenicity of Hypertrophic Cardiomyopathy-Associated Troponin T (TNNT2) Variant I79N.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34977031","citation_count":19,"is_preprint":false},{"pmid":"19666196","id":"PMC_19666196","title":"The role of large gene deletions and duplications in MYBPC3 and TNNT2 in patients with hypertrophic cardiomyopathy.","date":"2009","source":"International journal of cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/19666196","citation_count":15,"is_preprint":false},{"pmid":"35514357","id":"PMC_35514357","title":"Genotype-Driven Pathogenesis of Atrial Fibrillation in Hypertrophic Cardiomyopathy: The Case of Different TNNT2 Mutations.","date":"2022","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/35514357","citation_count":14,"is_preprint":false},{"pmid":"22017532","id":"PMC_22017532","title":"Cardiac Troponin T (TNNT2) mutations are less prevalent in Indian hypertrophic cardiomyopathy patients.","date":"2011","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/22017532","citation_count":14,"is_preprint":false},{"pmid":"33304277","id":"PMC_33304277","title":"A Novel Homozygous Intronic Variant in TNNT2 Associates With Feline Cardiomyopathy.","date":"2020","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/33304277","citation_count":13,"is_preprint":false},{"pmid":"31796423","id":"PMC_31796423","title":"Combinatorial genetic replenishments in myocardial and outflow tract tissues restore heart function in tnnt2 mutant zebrafish.","date":"2019","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/31796423","citation_count":11,"is_preprint":false},{"pmid":"31611837","id":"PMC_31611837","title":"TNNT2 Missplicing in Skeletal Muscle as a Cardiac Biomarker in Myotonic Dystrophy Type 1 but Not in Myotonic Dystrophy Type 2.","date":"2019","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/31611837","citation_count":11,"is_preprint":false},{"pmid":"19324435","id":"PMC_19324435","title":"Dilated cardiomyopathy caused by a novel TNNT2 mutation-added value of genetic testing in the correct identification of affected subjects.","date":"2009","source":"International journal of cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/19324435","citation_count":11,"is_preprint":false},{"pmid":"35861968","id":"PMC_35861968","title":"Human-Induced Pluripotent Stem Cell-Derived Cardiomyocyte Model for TNNT2 Δ160E-Induced Cardiomyopathy.","date":"2022","source":"Circulation. Genomic and precision medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35861968","citation_count":10,"is_preprint":false},{"pmid":"33588347","id":"PMC_33588347","title":"Association of variants in MYH7, MYBPC3 and TNNT2 with sudden cardiac death-related risk factors in Brazilian patients with hypertrophic cardiomyopathy.","date":"2021","source":"Forensic science international. Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33588347","citation_count":10,"is_preprint":false},{"pmid":"27737317","id":"PMC_27737317","title":"Prevalence and Phenotypic Expression of Mutations in the MYH7, MYBPC3 and TNNT2 Genes in Families with Hypertrophic Cardiomyopathy in the South of Brazil: A Cross-Sectional Study.","date":"2016","source":"Arquivos brasileiros de cardiologia","url":"https://pubmed.ncbi.nlm.nih.gov/27737317","citation_count":10,"is_preprint":false},{"pmid":"22292720","id":"PMC_22292720","title":"Genetic variation screening of TNNT2 gene in a cohort of patients with hypertrophic and dilated cardiomyopathy.","date":"2012","source":"Physiological research","url":"https://pubmed.ncbi.nlm.nih.gov/22292720","citation_count":9,"is_preprint":false},{"pmid":"26525169","id":"PMC_26525169","title":"TNNT2 Gene Polymorphisms are Associated with Susceptibility to Idiopathic Dilated Cardiomyopathy in Kazak and Han Chinese.","date":"2015","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/26525169","citation_count":8,"is_preprint":false},{"pmid":"27964935","id":"PMC_27964935","title":"Molecular and in silico analysis of a new plasmid-mediated AmpC β-lactamase (CMH-2) in clinical isolates of Klebsiella pneumoniae.","date":"2016","source":"Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/27964935","citation_count":8,"is_preprint":false},{"pmid":"34222259","id":"PMC_34222259","title":"Cardiac Overexpression of XIN Prevents Dilated Cardiomyopathy Caused by TNNT2 ΔK210 Mutation.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34222259","citation_count":7,"is_preprint":false},{"pmid":"37481519","id":"PMC_37481519","title":"Cardiac tropoini T (TNNT2) plays a potential oncogenic role in colorectal carcinogenesis.","date":"2023","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/37481519","citation_count":6,"is_preprint":false},{"pmid":"37159677","id":"PMC_37159677","title":"Low expression of the K280N TNNT2 mutation is sufficient to increase basal myofilament activation in human hypertrophy cardiomyopathy.","date":"2022","source":"Journal of molecular and cellular cardiology plus","url":"https://pubmed.ncbi.nlm.nih.gov/37159677","citation_count":6,"is_preprint":false},{"pmid":"31201803","id":"PMC_31201803","title":"Comparative analysis of the DYRK1A-SRSF6-TNNT2 pathway in myocardial tissue from individuals with and without Down syndrome.","date":"2019","source":"Experimental and molecular pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31201803","citation_count":6,"is_preprint":false},{"pmid":"25110706","id":"PMC_25110706","title":"Cardiac troponin T (TNNT2) mutations in chinese dilated cardiomyopathy patients.","date":"2014","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/25110706","citation_count":6,"is_preprint":false},{"pmid":"16538283","id":"PMC_16538283","title":"Hypertrophic cardiomyopathy--molecular genetic analysis of exons 9 and 11 of the TNNT2 gene in Czech patients.","date":"2006","source":"Methods of information in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/16538283","citation_count":6,"is_preprint":false},{"pmid":"37180798","id":"PMC_37180798","title":"Tale of two hearts: a TNNT2 hypertrophic cardiomyopathy case report.","date":"2023","source":"Frontiers in cardiovascular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/37180798","citation_count":5,"is_preprint":false},{"pmid":"23586019","id":"PMC_23586019","title":"TNNT2 gene polymorphisms are associated with susceptibility to idiopathic dilated cardiomyopathy in the Han Chinese population.","date":"2013","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/23586019","citation_count":5,"is_preprint":false},{"pmid":"28669108","id":"PMC_28669108","title":"Novel Genetic Variants in BAG3 and TNNT2 in a Swedish Family with a History of Dilated Cardiomyopathy and Sudden Cardiac Death.","date":"2017","source":"Pediatric cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/28669108","citation_count":4,"is_preprint":false},{"pmid":"40310325","id":"PMC_40310325","title":"The p.Asn271Ile Variant in the TNNT2 Gene Is Associated With Low-Risk Late-Onset Hypertrophic Cardiomyopathy.","date":"2025","source":"JACC. Heart failure","url":"https://pubmed.ncbi.nlm.nih.gov/40310325","citation_count":3,"is_preprint":false},{"pmid":"32846832","id":"PMC_32846832","title":"A novel nonsense mutation in TNNT2 in a Chinese pedigree with hypertrophic cardiomyopathy: A case report.","date":"2020","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32846832","citation_count":3,"is_preprint":false},{"pmid":"35596909","id":"PMC_35596909","title":"Impact of DYRK1A Expression on TNNT2 Splicing and Daunorubicin Toxicity in Human iPSC-Derived Cardiomyocytes.","date":"2022","source":"Cardiovascular toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/35596909","citation_count":2,"is_preprint":false},{"pmid":"36801602","id":"PMC_36801602","title":"Human induced pluripotent stem cell line YCMi007-A generated from a dilated cardiomyopathy patient with a heterozygous dominant c.613C > T (p. Arg205Trp) variant of the TNNT2 gene.","date":"2023","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/36801602","citation_count":2,"is_preprint":false},{"pmid":"23230735","id":"PMC_23230735","title":"[Expression of ACTN2, alpha-actin and TNNT2 in rat bone marrow-derived mesenchymal stem cells induced by low frequency pulsed electromagnetic fields].","date":"2012","source":"Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition","url":"https://pubmed.ncbi.nlm.nih.gov/23230735","citation_count":2,"is_preprint":false},{"pmid":"40084085","id":"PMC_40084085","title":"Cardiac-Specific Gene Editing via an AAV9-Tnnt2-SaCas9-miR122TS Vector.","date":"2025","source":"Bio-protocol","url":"https://pubmed.ncbi.nlm.nih.gov/40084085","citation_count":1,"is_preprint":false},{"pmid":"41321620","id":"PMC_41321620","title":"Phenotype specific nuclear lamina remodeling in hiPSC derived cardiomyocytes bearing TNNT2 sarcomeric variants.","date":"2025","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/41321620","citation_count":1,"is_preprint":false},{"pmid":"40344932","id":"PMC_40344932","title":"Generation of a human embryonic stem cell line (WAe009-A-3B) carrying homozygous TNNT2 gene knockout by CRISPR/Cas9 editing.","date":"2025","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/40344932","citation_count":1,"is_preprint":false},{"pmid":"34929444","id":"PMC_34929444","title":"Generation of an iPSC line (ZZUNEUi021-A) from a hypertrophic cardiomyopathy patient with TNNT2 mutation.","date":"2021","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/34929444","citation_count":1,"is_preprint":false},{"pmid":"32758068","id":"PMC_32758068","title":"Chondroid and Osseous Metaplasia of the Central Fibrous Body in Adolescent Hearts with Mutations in TNNI3 and TNNT2 genes.","date":"2020","source":"Pediatric and developmental pathology : the official journal of the Society for Pediatric Pathology and the Paediatric Pathology Society","url":"https://pubmed.ncbi.nlm.nih.gov/32758068","citation_count":1,"is_preprint":false},{"pmid":"36229763","id":"PMC_36229763","title":"A case of fetal isolated ventricular noncompaction with TNNT2 gene mutation and literature review.","date":"2022","source":"Echocardiography (Mount Kisco, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/36229763","citation_count":0,"is_preprint":false},{"pmid":"39191188","id":"PMC_39191188","title":"Carrying both the heterozygous Myh6-R453C and Tnnt2-R92W mutations aggravate the hypertrophic cardiomyopathy phenotype in mice.","date":"2024","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/39191188","citation_count":0,"is_preprint":false},{"pmid":"37503299","id":"PMC_37503299","title":"The HCM - Linked Mutation Arg92Leu in TNNT2 Allosterically Alters the cTnC - cTnI Interface and Disrupts the PKA-mediated Regulation of Myofilament Relaxation.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37503299","citation_count":0,"is_preprint":false},{"pmid":"19253838","id":"PMC_19253838","title":"[Association of TNNT2 gene mutations with idiopathic dilated cardiomyopathy in a Chengdu population].","date":"2008","source":"Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition","url":"https://pubmed.ncbi.nlm.nih.gov/19253838","citation_count":0,"is_preprint":false},{"pmid":"41429711","id":"PMC_41429711","title":"Generation of an induced pluripotent stem cell line (HPCHi002-A) derived from a dilated cardiomyopathy patient harboring heterozygous mutations c.644G > T (p.Arg215Leu) in the TNNT2 gene.","date":"2025","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/41429711","citation_count":0,"is_preprint":false},{"pmid":"41969674","id":"PMC_41969674","title":"A TNNT2 variant in a sporadic case of dilated cardiomyopathy: a case report and review.","date":"2026","source":"Frontiers in cardiovascular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41969674","citation_count":0,"is_preprint":false},{"pmid":"16630449","id":"PMC_16630449","title":"[Analysis of MYH7, MYBPC3 and TNNT2 gene mutations in 10 Chinese pedigrees with familial hypertrophic cardiomyopathy and the correlation between genotype and phenotype].","date":"2006","source":"Zhonghua xin xue guan bing za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/16630449","citation_count":0,"is_preprint":false},{"pmid":"42016857","id":"PMC_42016857","title":"Pediatric dilated cardiomyopathy caused by TNNT2-R151W mutation: Modeling and rescue in patient-derived induced pluripotent stem cells and engineered heart tissue.","date":"2026","source":"Bioengineering & translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/42016857","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.26.666851","title":"Investigating the role of long non-coding RNA in hypertrophic cardiomyopathy","date":"2025-07-31","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.26.666851","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.04.23.25326161","title":"Skeletal muscle biomarkers of amyotrophic lateral sclerosis: a large-scale, multi-cohort proteomic study","date":"2025-04-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.23.25326161","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.20.624427","title":"Cardiac electrical abnormalities in a mouse model of left ventricular non-compaction cardiomyopathy","date":"2024-11-22","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.20.624427","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.09.24314670","title":"Targeting mutant TNNT2-induced epigenetic perturbation and pathogenic signaling in left ventricular non-compaction cardiomyopathy","date":"2024-10-11","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.09.24314670","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.02.25.636485","title":"Remodelling of supernumerary leaflet primordia leads to bicuspid aortic valve (BAV) caused by loss of primary cilia","date":"2025-02-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.25.636485","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.08.24318665","title":"Genetic Causes of Sudden Cardiac Arrest in the Community","date":"2024-12-10","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.08.24318665","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":35999,"output_tokens":4875,"usd":0.090561},"stage2":{"model":"claude-opus-4-6","input_tokens":8371,"output_tokens":3527,"usd":0.195045},"total_usd":0.285606,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"TNNT2 encodes cardiac troponin T, a component of the thin filament troponin complex; the gene undergoes alternative splicing in the 5' coding region to produce multiple fetal isoforms in human fetal heart, and was mapped to chromosome 1q by somatic cell hybrid analysis.\",\n      \"method\": \"cDNA cloning, alternative splicing analysis, somatic cell hybrid mapping\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct molecular cloning and genomic mapping with functional isoform characterization\",\n      \"pmids\": [\"8088824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A 5-bp insertion/deletion polymorphism in intron 3 of TNNT2 affects alternative splicing, causing skipping of exon 4; the deletion allele was associated with larger left ventricular mass in HCM patients, demonstrated by in vitro expression studies.\",\n      \"method\": \"In vitro expression/splicing assay, population genetics, clinical echocardiography\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro splicing assay plus clinical association, single lab\",\n      \"pmids\": [\"14986170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TNNT2 missense mutations (Arg134Gly, Arg151Cys, Arg159Gln, Arg205Trp, Lys210del) associated with DCM cause decreased Ca2+ sensitivity of force development in cardiac myocytes reconstituted with mutant troponin T proteins, establishing a pathophysiological mechanism for DCM.\",\n      \"method\": \"Reconstituted cardiac myocyte force-Ca2+ measurement with mutant troponin T proteins\",\n      \"journal\": \"Circulation. Cardiovascular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct functional reconstitution assay with multiple mutations, clinical correlation\",\n      \"pmids\": [\"20031601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The rat Tnnt2 promoter drives cardiomyocyte-specific expression; an inducible Tnnt2-rtTA;TetO-Cre system achieves specific and robust Cre recombinase expression in cardiomyocytes of embryonic and adult mouse hearts following doxycycline induction, enabling cardiomyocyte-specific gene disruption.\",\n      \"method\": \"Transgenic mouse generation, Cre reporter lines, cardiac-specific gene disruption\",\n      \"journal\": \"Genesis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo validation with two reporter lines; widely replicated tool paper\",\n      \"pmids\": [\"20014345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The TNNT2 pE96K missense mutation causes impaired left ventricular function and induction of heart failure marker genes in transgenic mice, demonstrating intrinsic cardiomyocyte dysfunction independent of a non-compaction phenotype.\",\n      \"method\": \"Transgenic mouse model, echocardiography, histology, gene expression analysis\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean transgenic model with functional cardiac phenotyping, single lab\",\n      \"pmids\": [\"20083571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cells of the Tnnt2-Cre lineage (myocardial lineage) populate the intercalated cushions of the outflow tract that give rise to the anterior pulmonary valve cusp and non-coronary aortic valve cusp; these cells express mesenchymal markers Sox9 and versican without expressing Tnnt2 mRNA or protein, revealing a previously unrecognized myocardial-to-mesenchymal contribution to valve development.\",\n      \"method\": \"Cre-based lineage tracing with Rosa TdTomato-EGFP reporter, 3D imaging, immunostaining\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct lineage tracing with multiple Cre drivers and reporter confirmation, single lab\",\n      \"pmids\": [\"29920846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Tnnt2a is expressed not only in myocardial cells but also in a novel group of smooth muscle cells on the outflow tract (OFT); restoring tnnt2a expression in both myocardial and OFT cells (but not myocardium alone) rescues cardiac function and circulation in tnnt2a-null zebrafish, demonstrating an essential role of Tnnt2 in OFT mechanical dynamics.\",\n      \"method\": \"CRISPR/Cas9 knockout zebrafish, conditional rescue with tissue-specific promoters, RNA-seq, immunofluorescence\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic rescue experiment with multiple tissue-specific rescue conditions, RNA-seq, single lab\",\n      \"pmids\": [\"31796423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DYRK1A regulates the alternative splicing of TNNT2 through phosphorylation of the splicing factor SRSF6; elevated phosphorylated SRSF6 in trisomy 21 myocardium correlates with increased expression of fetal TNNT2 isoforms, and TNNT2 missplicing correlates with QRS cardiac parameters in DM1 patients.\",\n      \"method\": \"Western blotting, RT-PCR splicing analysis, immunohistochemistry in human myocardial tissue\",\n      \"journal\": \"Experimental and molecular pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pathway established by correlative molecular analysis in human tissue with multiple biomarkers, replicated across DM1/DM2 cohorts\",\n      \"pmids\": [\"31201803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HCM-associated TNNT2 variants increase cardiac microtissue contraction and myofilament calcium affinity, while DCM-associated TNNT2 variants decrease contraction and myofilament calcium affinity; these sarcomere contractile changes induce graded transcriptomic responses including MAPK targets, HOPX, and NPPB in human iPSC-derived cardiomyocytes.\",\n      \"method\": \"CRISPR/Cas9 hiPSC engineering, cardiac microtissue contraction assay, thin filament calcium reporter, RNA sequencing, NPPB-tdTomato reporter\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal functional assays in isogenic human cell systems across 51 variants\",\n      \"pmids\": [\"33025817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The HCM-associated TNNT2 I79N variant increases myofilament Ca2+ sensitivity and decreases Ca2+ off-rate (koff) in reconstituted human cardiac thin filaments; in CRISPR/Cas9-engineered heterozygous I79N hiPSC-CMs, enhanced Ca2+ buffering reduced intracellular Ca2+ transients, caused beat-to-beat instability and action potential triangulation, and induced alternans at elevated pacing rates, revealing a pro-arrhythmic mechanism.\",\n      \"method\": \"Reconstituted thin filament stopped-flow fluorescence, CRISPR/Cas9 hiPSC-CMs, voltage/Ca2+ imaging, transcriptomics\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution combined with isogenic hiPSC-CM functional studies, multiple orthogonal methods\",\n      \"pmids\": [\"34977031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"XIN protein expression is reduced in TNNT2-ΔK210 cardiomyocytes and mouse hearts; overexpression of XINB isoform decreases myofilament disorganization, increases cell contractility, and ameliorates DCM remodeling (cardiac dilation, systolic dysfunction, fibrosis) in TNNT2-ΔK210 mice via AAV9 delivery.\",\n      \"method\": \"hESC-derived cardiomyocytes, transgenic mice, AAV9 cardiac overexpression, echocardiography, histology\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo AAV rescue experiment with functional cardiac readouts, single lab\",\n      \"pmids\": [\"34222259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The TNNT2 K280N mutation increases myofilament Ca2+ sensitivity independent of phosphorylation status (not corrected by alkaline phosphatase or PKA treatment); as little as 14% mutant cTnT-K280N in troponin exchange experiments is sufficient to increase Ca2+ sensitivity; hiPSC-CMs with heterozygous or homozygous K280N show elevated diastolic Ca2+, increased contractility, and impaired relaxation (dose-dependent).\",\n      \"method\": \"Force measurements in isolated cardiomyocytes, alkaline phosphatase/PKA treatment, troponin exchange, CRISPR/Cas9 isogenic hiPSC-CMs, Ca2+ transient and cell shortening assays\",\n      \"journal\": \"Journal of molecular and cellular cardiology plus\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution (troponin exchange) plus isogenic hiPSC-CMs with multiple orthogonal functional assays\",\n      \"pmids\": [\"37159677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The TNNT2 Δ160E mutation causes prolonged calcium decay, relaxation impairment, and hypertrophy in hiPSC-CMs in a gene-dosage dependent manner; the mutant protein causes sarcomeric calcium retention, activates NFATc1 nuclear translocation and CaMKIIδ/phospholamban phosphorylation; epigallocatechin-3-gallate (calcium desensitizer) rescues the calcium and relaxation phenotype.\",\n      \"method\": \"CRISPR/Cas9 isogenic iPSC-CMs (heterozygous, homozygous, corrected), Ca2+ imaging with R-GECO-fused mutant cTnT, high-content NFATc1 imaging, western blotting for CaMKIIδ/phospholamban, drug rescue\",\n      \"journal\": \"Circulation. Genomic and precision medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — isogenic hiPSC-CMs with multiple orthogonal mechanistic readouts and pharmacological rescue\",\n      \"pmids\": [\"35861968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Specific TNNT2 HCM mutations (R92Q) increase atrial myofilament calcium sensitivity, reduce inotropic reserve, slow twitch kinetics, and directly promote spontaneous beats and triggered contractions in atrial trabeculae, providing a genotype-specific arrhythmogenic mechanism for atrial fibrillation; E163R mutation instead increases tension cost without causing atrial arrhythmias.\",\n      \"method\": \"Mouse HCM models (R92Q and E163R), ex vivo atrial trabecula mechanics, ATPase measurements, echocardiography\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct ex vivo functional studies in two genetically distinct mouse models with mechanistic comparison\",\n      \"pmids\": [\"35514357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DYRK1A overexpression in iPSC-derived cardiomyocytes increases TNNT2 fetal splice variant abundance (~58% increase) and decreases the adult cTnT3 variant (~27% decrease) by increasing SRSF6 phosphorylation (~25-65%), establishing the DYRK1A→SRSF6→TNNT2 splicing pathway in human cardiomyocytes.\",\n      \"method\": \"DYRK1A overexpression in hiPSC-CMs, RT-PCR for splice variants, western blotting for phospho-SRSF6\",\n      \"journal\": \"Cardiovascular toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct gain-of-function experiment with molecular readouts in human cardiomyocytes, single lab\",\n      \"pmids\": [\"35596909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TNNT2 physically interacts with EGFR protein in colorectal cancer cells (co-immunoprecipitation); TNNT2 overexpression upregulates EGFR and HER2, decreases E-cadherin, increases Vimentin and N-cadherin (EMT markers), and promotes proliferation, migration, and invasion, suggesting a non-sarcomeric role via EGFR/HER2/EMT signaling.\",\n      \"method\": \"Co-immunoprecipitation, western blotting, CCK-8, colony formation, Transwell assays, qPCR in CRC cell lines\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single co-IP plus overexpression/knockdown in cancer cells; non-canonical context, single lab\",\n      \"pmids\": [\"37481519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The HCM-causative TNNT2 R92L mutation allosterically repositions the N-terminus of cTnI closer to cTnC (measured by TR-FRET), creates additional electrostatic interactions at the PKA consensus sequence, reduces cTnI phosphorylation, and causes early-onset diastolic dysfunction; constitutive phosphomimetic cTnI (D23D24) recovers diastolic function specifically for R92L-cTnT, identifying impaired PKA accessibility as the mechanism.\",\n      \"method\": \"In vivo mouse model, ex vivo hemodynamics, western blotting, stopped-flow kinetics, TR-FRET, molecular dynamics simulations, constitutive phosphomimetic cTnI rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal structural/functional methods in vivo and in vitro; preprint not yet peer-reviewed\",\n      \"pmids\": [\"37503299\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The TNNT2 R141W mutation disrupts a salt bridge between TNNT2 and E-257 of tropomyosin (3D structural modeling), reducing cardiac contraction; nuclear TNNT2 functions as an HDAC1 sponge in cardiomyocytes, and the R141W mutant has compromised HDAC1 association, causing epigenetic perturbation and transcriptional dysregulation including downregulation of cardiac muscular genes and upregulation of TGFβ signaling and EZH2; simvastatin restores nuclear TNNT2(R141W)-HDAC1 association and recovers cardiac function.\",\n      \"method\": \"Knock-in mice (Tnnt2 R154W), iPSC-derived cardiomyocytes from LVNC patients, 3D protein modeling, co-IP (TNNT2-HDAC1), omics, drug screening, in vivo cardiac functional assessment\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP, knock-in mouse model, patient iPSC-CMs, and pharmacological rescue; preprint\",\n      \"pmids\": [\"bio_10.1101_2024.10.09.24314670\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The DCM-causing TNNT2 R151W mutation causes sarcomere disarray, attenuated Ca2+ transient amplitude, prolonged time to Ca2+ peak, and delayed Ca2+ decay tau in iPSC-CMs; in pillar-based engineered heart tissue, R151W substantially decreases contractile force; overexpression of wild-type TNNT2 in patient iPSCs rescues sarcomere organization, Ca2+ handling, and contractile force, demonstrating that sarcomere insufficiency and Ca2+ handling disturbance are the primary disease mechanism.\",\n      \"method\": \"Patient-derived iPSC-CMs, isogenic WT TNNT2 overexpression rescue, pillar-based engineered heart tissue (EHT) contractile force assay, Ca2+ imaging, sarcomere immunofluorescence\",\n      \"journal\": \"Bioengineering & translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — patient-derived and rescued isogenic EHT with multiple orthogonal functional assays, single lab\",\n      \"pmids\": [\"42016857\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TNNT2 encodes cardiac troponin T, a thin-filament protein that regulates Ca2+-dependent actomyosin interaction; its alternative splicing is controlled by the DYRK1A→SRSF6 kinase-splicing axis, and disease-causing mutations (HCM or DCM) alter myofilament Ca2+ sensitivity and contractile force in opposite directions—HCM variants increase and DCM variants decrease Ca2+ sensitivity and contraction—with downstream consequences including transcriptomic remodeling via MAPK/NPPB pathways, altered Ca2+ handling and arrhythmogenesis, nuclear lamina remodeling, and (for certain mutations) disruption of a nuclear HDAC1-sponge function that causes epigenetic perturbation in cardiomyocytes.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TNNT2 encodes cardiac troponin T (cTnT), a core component of the thin-filament troponin complex that governs Ca²⁺-dependent regulation of actomyosin interaction and sarcomere contraction in cardiomyocytes [PMID:8088824]. The gene undergoes developmental alternative splicing—controlled by the DYRK1A→SRSF6 phosphorylation axis—to produce fetal and adult isoforms with distinct functional properties [PMID:8088824, PMID:35596909]. Disease-causing missense mutations partition into two mechanistic classes: HCM-associated variants (e.g., R92Q, I79N, K280N, Δ160E) increase myofilament Ca²⁺ sensitivity, impair relaxation, and promote arrhythmogenesis through enhanced Ca²⁺ buffering and signaling via CaMKIIδ/NFAT pathways, whereas DCM-associated variants (e.g., R134G, R151C, R205W, ΔK210, R151W) decrease Ca²⁺ sensitivity and contractile force, with wild-type TNNT2 overexpression rescuing the phenotype [PMID:20031601, PMID:33025817, PMID:34977031, PMID:35861968, PMID:42016857]. Beyond its sarcomeric role, TNNT2 localizes to cardiomyocyte nuclei where it sequesters HDAC1, and disruption of this interaction by the R141W mutation causes epigenetic perturbation and transcriptional dysregulation [PMID:bio_10.1101_2024.10.09.24314670].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing the identity of TNNT2 as the cardiac troponin T gene resolved which thin-filament component was heart-specific and revealed that developmental alternative splicing generates multiple fetal isoforms.\",\n      \"evidence\": \"cDNA cloning, alternative splicing analysis, and somatic cell hybrid mapping of human fetal heart\",\n      \"pmids\": [\"8088824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequences of individual fetal vs. adult isoforms not determined\", \"Splicing regulatory mechanism unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of an intronic polymorphism that controls exon 4 skipping demonstrated that TNNT2 splicing variation has clinical consequences, linking isoform composition to left ventricular mass in HCM patients.\",\n      \"evidence\": \"In vitro splicing assay of 5-bp indel in intron 3 combined with echocardiographic association in HCM cohort\",\n      \"pmids\": [\"14986170\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis of how exon 4 inclusion alters cardiac function not established\", \"Association study in single cohort\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Reconstitution of DCM-associated TNNT2 mutations into cardiac myocytes established that decreased Ca²⁺ sensitivity of force is the unifying biophysical defect in DCM-causing variants, providing the first systematic functional classification of TNNT2 mutations.\",\n      \"evidence\": \"Force–Ca²⁺ measurements in cardiac myocytes reconstituted with five different DCM-associated mutant troponin T proteins\",\n      \"pmids\": [\"20031601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether decreased Ca²⁺ sensitivity alone is sufficient for DCM in vivo was untested\", \"Downstream transcriptomic consequences unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Two studies—a cardiomyocyte-specific inducible Cre tool and a pE96K transgenic model—validated that TNNT2 promoter activity is cardiomyocyte-specific and that single TNNT2 mutations are sufficient to cause intrinsic contractile dysfunction and heart failure gene induction in vivo.\",\n      \"evidence\": \"Transgenic mouse with Tnnt2-rtTA;TetO-Cre validated with Cre reporters; Tnnt2 pE96K transgenic mice with echocardiography and gene expression analysis\",\n      \"pmids\": [\"20014345\", \"20083571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking pE96K to contractile dysfunction not resolved at the molecular level\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Lineage tracing revealed that Tnnt2-expressing myocardial progenitors contribute to outflow tract valve mesenchyme through a myocardial-to-mesenchymal transition, expanding TNNT2's developmental role beyond sarcomeric function.\",\n      \"evidence\": \"Cre-based lineage tracing with Rosa TdTomato-EGFP reporter and 3D imaging in mouse embryos\",\n      \"pmids\": [\"29920846\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TNNT2 mutations affect valve development through this lineage is unknown\", \"Lineage contribution quantified in mouse only\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Two advances defined upstream regulatory and non-cardiac roles: DYRK1A phosphorylation of SRSF6 was identified as the kinase pathway controlling TNNT2 fetal-to-adult isoform switching, and Tnnt2a was shown to be essential in outflow tract smooth muscle cells for cardiac output in zebrafish.\",\n      \"evidence\": \"DYRK1A→SRSF6→TNNT2 splicing analysis in trisomy 21 and DM1 human myocardium; CRISPR knockout and tissue-specific rescue of tnnt2a in zebrafish\",\n      \"pmids\": [\"31201803\", \"31796423\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DYRK1A pathway directly binds TNNT2 pre-mRNA cis-elements is unknown\", \"OFT smooth muscle role not confirmed in mammalian systems\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A comprehensive survey of 51 TNNT2 variants in isogenic hiPSC-CMs established that HCM mutations increase and DCM mutations decrease microtissue contraction and Ca²⁺ affinity in a graded manner, with contractile changes driving downstream transcriptomic remodeling via MAPK and NPPB pathways.\",\n      \"evidence\": \"CRISPR/Cas9 isogenic hiPSC-CM panel, cardiac microtissue contraction, thin filament Ca²⁺ reporter, RNA-seq, NPPB-tdTomato reporter\",\n      \"pmids\": [\"33025817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether graded transcriptomic remodeling occurs in adult human heart tissue in vivo is untested\", \"Specific MAPK effectors mediating remodeling not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Detailed biophysical and cellular studies of specific HCM mutations (I79N, K280N) revealed that increased Ca²⁺ sensitivity operates through decreased Ca²⁺ off-rate from thin filaments, causing Ca²⁺ buffering defects, beat-to-beat instability, and dose-dependent diastolic dysfunction—mechanisms that explain arrhythmogenesis at the single-cell level.\",\n      \"evidence\": \"Stopped-flow fluorescence on reconstituted thin filaments; isogenic CRISPR hiPSC-CMs with voltage/Ca²⁺ imaging and troponin exchange experiments\",\n      \"pmids\": [\"34977031\", \"37159677\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether these kinetic defects can be pharmacologically targeted at the thin filament level in vivo\", \"Contribution of heterozygous vs. homozygous mutant incorporation ratios in patient hearts unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Multiple studies converged on mutation-specific mechanistic details: Δ160E was shown to activate CaMKIIδ and NFATc1 hypertrophic signaling from sarcomeric Ca²⁺ retention; R92Q was identified as a genotype-specific atrial arrhythmia driver; DYRK1A→SRSF6→TNNT2 splicing was validated by gain-of-function in human cardiomyocytes; and XIN (XINB) was identified as a downstream effector whose loss contributes to ΔK210 DCM remodeling.\",\n      \"evidence\": \"CRISPR isogenic iPSC-CMs with Ca²⁺-fused mutant cTnT and EGCG rescue; ex vivo atrial trabeculae from R92Q/E163R mice; DYRK1A overexpression in hiPSC-CMs; AAV9-XINB rescue in ΔK210 mice\",\n      \"pmids\": [\"35861968\", \"35514357\", \"35596909\", \"34222259\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CaMKIIδ/NFAT activation is a general feature of all HCM mutations or Δ160E-specific\", \"XIN mechanism of sarcomere stabilization not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two preprints identified novel mechanistic layers: R92L allosterically repositions cTnI to block PKA phosphorylation as the basis for diastolic dysfunction (rescued by phosphomimetic cTnI), and R141W disrupts a nuclear TNNT2–HDAC1 sponge interaction, causing epigenetic perturbation rescued by simvastatin, revealing an unexpected non-sarcomeric nuclear function.\",\n      \"evidence\": \"(preprint) TR-FRET, molecular dynamics, phosphomimetic cTnI rescue in R92L mice; (preprint) knock-in mice, patient iPSC-CMs, co-IP TNNT2-HDAC1, drug screening\",\n      \"pmids\": [\"37503299\", \"bio_10.1101_2024.10.09.24314670\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Both findings are preprints awaiting peer review\", \"Nuclear HDAC1-sponge function not confirmed by independent labs\", \"Structural basis of TNNT2-HDAC1 interaction not defined\", \"Whether PKA accessibility defect applies to other HCM mutations is unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Wild-type TNNT2 overexpression rescue in patient-derived iPSC-CMs and engineered heart tissues demonstrated that sarcomere insufficiency and Ca²⁺ handling disturbance are the primary, correctable disease mechanism in DCM caused by R151W.\",\n      \"evidence\": \"Patient iPSC-CMs with WT TNNT2 overexpression, pillar-based EHT contractile force assay, Ca²⁺ imaging\",\n      \"pmids\": [\"42016857\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether gene supplementation is therapeutic in vivo remains untested\", \"Stoichiometric effects of overexpression on troponin complex assembly not evaluated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis and generality of TNNT2's nuclear HDAC1-sponge function, whether distinct HCM mutations share the PKA accessibility defect or each operates through unique allosteric mechanisms, and how fetal-to-adult isoform switching is integrated with developmental and disease-related sarcomere remodeling in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of full-length cTnT in complex with HDAC1\", \"No in vivo gene therapy trial for TNNT2 cardiomyopathy\", \"Contribution of individual splice isoforms to adult cardiac function not dissected in human\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 2, 8, 9, 11]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [2, 8, 9, 11, 12]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 2, 8, 9, 11, 12, 18]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [0, 2, 8, 9, 11, 13, 18]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 4, 8, 9, 12, 13, 18]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [1, 7, 14]}\n    ],\n    \"complexes\": [\n      \"cardiac troponin complex (cTnT–cTnI–cTnC)\",\n      \"thin filament (troponin–tropomyosin–actin)\"\n    ],\n    \"partners\": [\n      \"TNNC1\",\n      \"TNNI3\",\n      \"TPM1\",\n      \"SRSF6\",\n      \"HDAC1\",\n      \"XIRP2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}