{"gene":"MYH6","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2009,"finding":"Loss-of-function nonsense mutation in myh6 (cardiac myosin heavy chain) in Xenopus tropicalis muzak mutants deletes the coiled-coil domain required for thick filament polymerization, severely disrupting the cardiomyocyte cytoskeleton and abolishing cardiac contractility, while early cardiac morphogenesis (looping, chamber formation) proceeds normally but valves and trabeculae fail to form.","method":"Positional cloning, loss-of-function genetic model (Xenopus tropicalis muzak mutant), histology and cytoskeletal analysis","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — first positional cloning in X. tropicalis with defined structural and functional phenotype; ortholog of mammalian MYH6","pmids":["19769958"],"is_preprint":false},{"year":2010,"finding":"MYH6 mutations A230P and A1366D significantly disrupt myofibril formation when GFP-MYH6 fusion proteins are expressed in mouse myoblasts, while mutation H252Q significantly enhances myofibril assembly compared to wild-type, demonstrating that specific residues in MYH6 are required for proper sarcomere/myofibril organization.","method":"Transfection of GFP-MYH6 fusion constructs (wild-type and mutant) in mouse myoblasts, fluorescence microscopy of myofibril formation","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional cell-based assay with multiple mutants; single lab study","pmids":["20656787"],"is_preprint":false},{"year":2013,"finding":"Allele-specific RNAi delivered by AAV selectively silences the R403Q mutant Myh6 transcript in heterozygous HCM mice; a ~25% reduction in mutant transcript levels is sufficient to prevent hypertrophy and myocardial fibrosis for at least 6 months, establishing that partial suppression of the mutant allele blocks HCM pathogenesis.","method":"AAV-delivered RNAi in Myh6(R403Q/+) knock-in mice, echocardiography, histology, quantitative RT-PCR","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — in vivo loss-of-function with allele-specific approach, multiple phenotypic readouts, highly cited foundational study","pmids":["24092743"],"is_preprint":false},{"year":2016,"finding":"Under pathological cardiac stress, BRG1 (nucleosome-remodeling factor) is activated in cardiomyocytes and sequentially recruits G9a/GLP (histone methyltransferase) and DNMT3 (DNA methyltransferase) to assemble repressive chromatin on the Myh6 promoter, marked by H3K9 methylation and CpG methylation, thereby silencing Myh6 and impairing cardiac contraction; disruption of any component of this complex de-represses Myh6 and reduces stress-induced dysfunction.","method":"Co-immunoprecipitation of BRG1-G9a-DNMT3 complex, ChIP for H3K9me and CpG methylation on Myh6 promoter, genetic disruption of Brg1/G9a/Dnmt3 in mice, cardiac function assays; validated in human hypertrophic heart tissue","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (Co-IP, ChIP, genetic loss-of-function, human tissue correlation), mechanistic pathway fully reconstituted","pmids":["26952936"],"is_preprint":false},{"year":2019,"finding":"In adult zebrafish myh6-/- (weak atrium) mutants, loss of atrial myosin heavy chain leads to atrial hypoplasia with elastin deposition; the compensatory ventricular enlargement occurs predominantly via cardiomyocyte hyperplasia (not hypertrophy), accompanied by activation of mammalian hypertrophy-associated transcriptional profiles and ER-stress pathway activation.","method":"Immunohistochemistry, confocal microscopy (cardiomyocyte size/density/proliferation), RT-PCR for hypertrophy markers, western blot for ER stress markers in myh6-/- zebrafish","journal":"Cell and tissue research","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic knockout with multiple cellular readouts in zebrafish ortholog; single lab","pmids":["31129720"],"is_preprint":false},{"year":2016,"finding":"Patient-derived iPSC-cardiomyocytes from HLHS subjects with MYH6 variants exhibit defective cardiomyogenic differentiation and upregulation of MYH7 (β-myosin heavy chain), mirroring in vivo cardiac tissue expression changes; this establishes that MYH6 variants alter the MYH6/MYH7 balance during cardiomyogenesis.","method":"iPSC cardiomyocyte differentiation from HLHS patients, transcriptome and protein expression analysis of cardiac tissue, MYH7 upregulation quantification","journal":"Physiological genomics","confidence":"Medium","confidence_rationale":"Tier 2 — patient iPSC model with in vitro/in vivo correlation; single lab","pmids":["27789736"],"is_preprint":false},{"year":2020,"finding":"iPSC-cardiomyocytes carrying the MYH6-R443P head domain variant show dysmorphic sarcomere structure, increased MYH7 expression replacing MYH6 after differentiation day 15, slower contraction rates, reduced shortening, and slower relaxation; CRISPR/Cas9 correction of R443P rescues sarcomere organization and contractile phenotypes, demonstrating that this variant in the MYH6 motor head directly impairs sarcomere assembly and contractility.","method":"iPSC-cardiomyocyte functional assays (contraction rate, shortening, velocity), immunostaining, CRISPR/Cas9 correction and reintroduction of R443P variant, patient cardiac tissue immunostaining","journal":"Frontiers in cell and developmental biology","confidence":"High","confidence_rationale":"Tier 1–2 — CRISPR isogenic correction and reintroduction provide bidirectional causality; multiple functional and structural readouts","pmids":["32656206"],"is_preprint":false},{"year":1993,"finding":"The human MYH6 gene consists of 39 exons (37 coding), with the 5'-UTR split across 3 exons and the AUG initiation codon in the third exon; all exon/intron boundaries are conserved with cardiac β-MHC (MYH7) except the 13th intron of MYH7 which is absent in MYH6; the encoded protein sequence was fully determined.","method":"Complete genomic sequencing of human MYH6 locus (26,159 bp) and comparative analysis","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1 — complete structural characterization of gene architecture by direct sequencing","pmids":["8307559"],"is_preprint":false},{"year":2011,"finding":"Three MYH6 missense mutations (R17H, C539R, K543R) associated with familial atrial septal defect are all located in the highly conserved alpha-myosin motor domain region involved in myosin-actin interaction, suggesting that perturbation of this actin-binding interface is a mechanism for MYH6-associated congenital heart defects.","method":"Array-based resequencing of 13 sarcomeric genes, co-segregation analysis in families, structural and homology analysis of mutation locations","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — genetic segregation plus structural localization; no direct functional actin-binding assay performed","pmids":["22194935"],"is_preprint":false},{"year":2021,"finding":"Novel MYH6 insertion variant Arg1822_Glu1823dup in the coiled-coil tail domain significantly impairs myofibril formation and increases apoptosis in transfected C2C12 myoblasts; molecular simulation reveals the variant impairs the myosin α-helix and increases coiled-coil dimer stability, suggesting altered tail domain self-aggregation as a disease mechanism.","method":"Transfection of MYH6 variants in C2C12 cells, myofibril formation assay, apoptosis assay, molecular dynamics simulation","journal":"European journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — cell-based functional assay plus molecular modeling; single lab","pmids":["34481090"],"is_preprint":false},{"year":2022,"finding":"Variants in the MYH6 gene promoter (g.4085G>C and g.4716G>A, identified in VSD patients) significantly reduce MYH6 transcriptional activity as shown by dual luciferase reporter assays, and alter transcription factor binding as shown by electrophoretic mobility shift assays, establishing a regulatory mechanism by which promoter variants reduce MYH6 expression.","method":"Dual luciferase reporter assay, electrophoretic mobility shift assay (EMSA), bioinformatics (JASPAR)","journal":"BMC medical genomics","confidence":"Medium","confidence_rationale":"Tier 2 — two orthogonal functional assays (reporter + EMSA) in cellular systems; single lab","pmids":["36209093"],"is_preprint":false},{"year":2023,"finding":"MYH6 gene promoter variants found in Tetralogy of Fallot patients reduce MYH6 transcriptional activity in dual luciferase reporter assays and alter transcription factor binding in EMSA across three cell lines (HEK-293, HL-1, H9C2), indicating that reduced MYH6 promoter-driven expression is a pathogenic mechanism in TOF.","method":"Dual luciferase reporter assay, EMSA in three cell lines, bioinformatics (JASPAR)","journal":"Pediatric research","confidence":"Medium","confidence_rationale":"Tier 2 — two orthogonal functional assays replicated in three cell lines; single lab","pmids":["38135727"],"is_preprint":false},{"year":2024,"finding":"MYH6 variants in HLHS neonates are associated with impaired right atrial active contractility (reduced RA active strain) as measured by 2D speckle-tracking echocardiography, while RV function is preserved; RA reservoir and conduit strain correlate with heart rate only in variant carriers, demonstrating atrium-specific functional impairment consistent with the atrial predominance of MYH6 expression.","method":"2D speckle-tracking echocardiography in neonates, strain and strain rate analysis, case-control comparison","journal":"Genes","confidence":"Medium","confidence_rationale":"Tier 2 — direct in vivo functional measurement tied to MYH6 genotype with matched controls; single study","pmids":["39596649"],"is_preprint":false},{"year":2024,"finding":"MYH6 overexpression suppresses proliferation and migration of prostate cancer cells in vitro and in vivo; RNA-seq identified KIT proto-oncogene as a downstream target downregulated by MYH6, and rescue assays confirmed that MYH6's tumor-suppressive effects are mediated through downregulation of KIT expression.","method":"Overexpression in prostate cancer cell lines, proliferation and migration assays, xenograft in vivo model, RNA-seq, rescue assays with KIT","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays with downstream target validation by rescue; single lab, non-cardiac context","pmids":["39181964"],"is_preprint":false},{"year":2025,"finding":"A gene regulatory enhancer element interacts directly with the MYH6 locus (confirmed by chromatin conformation assays) and controls MYH6 expression; epigenome editing-mediated enhancer activation alters cardiomyocyte response to endothelin-1 stress, preventing polyploidization and changes in calcium dynamics, establishing that enhancer-mediated MYH6 regulation modulates cardiomyocyte stress response and maturation.","method":"Chromatin conformation assays (3C/Hi-C type), epigenome editing, endothelin-1 stress assay, calcium dynamics measurement, polyploidy analysis in hiPSC-derived cardiomyocytes","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1–2 — chromatin conformation plus epigenome editing with functional readouts; preprint, not yet peer-reviewed","pmids":[],"is_preprint":true},{"year":2024,"finding":"hiPSC-CMs carrying HCM-associated MYH6-R725C and MYH7-R723C mutations in 3D engineered heart tissues show elevated TGF-β1 secretion specifically from mutant cardiomyocytes, increased activated fibroblasts, and augmented contraction force; blocking TGF-β1 receptor signaling normalizes fibroblast activation and force to control levels, placing mutant MYH6/7-driven TGF-β1 overexpression upstream of fibroblast activation.","method":"3D engineered heart tissue (EHT) model, ELISA/secretion assay for TGF-β1, fibroblast activation markers, contraction force measurement, TGF-β receptor antagonist rescue","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2–3 — preprint with functional assays but MYH6 and MYH7 mutations analyzed together, making MYH6-specific attribution uncertain","pmids":[],"is_preprint":true}],"current_model":"MYH6 encodes the α-myosin heavy chain, a core sarcomeric motor protein that polymerizes via its coiled-coil tail domain into thick filaments and drives cardiac contraction through actin interaction via its head/motor domain; its expression is epigenetically regulated in stressed hearts by a BRG1-G9a/GLP-DNMT3 repressive chromatin complex assembled on the MYH6 promoter, and by enhancer elements that modulate cardiomyocyte stress responses; loss or mutation of MYH6 disrupts myofibril formation, impairs contractility (especially atrial), shifts MYH6/MYH7 balance toward fetal β-MHC, and can trigger downstream TGF-β1-mediated fibroblast activation, while allele-specific silencing of dominant gain-of-function mutations is sufficient to prevent hypertrophic cardiomyopathy pathology in vivo."},"narrative":{"teleology":[{"year":1993,"claim":"Complete genomic characterization of MYH6 established its 39-exon architecture and near-identity with the MYH7 locus, providing the structural framework needed to interpret subsequent disease-associated variants.","evidence":"Full genomic sequencing (26,159 bp) and comparative analysis with MYH7","pmids":["8307559"],"confidence":"High","gaps":["No functional data on promoter or regulatory elements at this stage","No disease mutation mapping yet performed"]},{"year":2009,"claim":"Positional cloning of the Xenopus muzak mutant demonstrated that the MYH6 coiled-coil tail domain is essential for thick filament assembly and cardiac contractility, while dispensable for early cardiac morphogenesis.","evidence":"Positional cloning and cytoskeletal/histological analysis in X. tropicalis muzak loss-of-function mutant","pmids":["19769958"],"confidence":"High","gaps":["Xenopus ortholog; direct extrapolation to mammalian MYH6 function required confirmation","No motor-domain-specific functional dissection"]},{"year":2010,"claim":"Expression of disease-associated MYH6 point mutants in myoblasts revealed that specific residues in both the head and tail domains are required for proper myofibril formation, separating gain-of-assembly from loss-of-assembly variants.","evidence":"GFP-MYH6 wild-type and mutant fusion construct transfection in mouse myoblasts with fluorescence microscopy","pmids":["20656787"],"confidence":"Medium","gaps":["Overexpression in non-cardiomyocyte cell line; physiological relevance in cardiomyocytes not confirmed","No contractile or mechanical readouts"]},{"year":2011,"claim":"Identification of MYH6 motor-domain missense mutations co-segregating with familial atrial septal defects placed the myosin-actin interaction interface as a critical determinant of congenital heart structure.","evidence":"Array-based sarcomeric gene resequencing, family co-segregation analysis, structural homology mapping","pmids":["22194935"],"confidence":"Medium","gaps":["No direct actin-binding or ATPase functional assays performed for the identified variants","Structural inference based on homology, not crystal structure of α-MHC"]},{"year":2013,"claim":"Allele-specific RNAi silencing of the R403Q mutant Myh6 allele in vivo proved that even partial (~25%) suppression of the gain-of-function transcript prevents hypertrophic cardiomyopathy, establishing a therapeutic paradigm for dominant sarcomeric mutations.","evidence":"AAV-delivered allele-specific RNAi in Myh6(R403Q/+) knock-in mice with echocardiography, histology, and qRT-PCR","pmids":["24092743"],"confidence":"High","gaps":["Long-term durability beyond 6 months not assessed","Translation to human MYH6 sequence context not tested"]},{"year":2016,"claim":"Discovery that a BRG1–G9a/GLP–DNMT3 repressive complex assembles on the MYH6 promoter under cardiac stress explained how pathological signaling epigenetically silences α-MHC to drive the fetal gene re-expression program and contractile dysfunction.","evidence":"Co-IP, ChIP (H3K9me, CpG methylation), genetic disruption of Brg1/G9a/Dnmt3 in mice, validation in human hypertrophic heart tissue","pmids":["26952936"],"confidence":"High","gaps":["Upstream signal that activates BRG1 recruitment to MYH6 specifically remains undefined","Relative contribution of H3K9me vs CpG methylation not dissected"]},{"year":2016,"claim":"Patient iPSC-cardiomyocytes with MYH6 variants recapitulated the MYH6-to-MYH7 isoform shift observed in HLHS cardiac tissue, providing a human cellular model linking MYH6 haploinsufficiency to defective cardiomyogenesis and β-MHC compensation.","evidence":"iPSC-CM differentiation from HLHS patients, transcriptome and protein expression analysis","pmids":["27789736"],"confidence":"Medium","gaps":["Specific MYH6 variants not functionally isolated from genetic background","Mechanism by which MYH6 loss upregulates MYH7 not determined"]},{"year":2019,"claim":"Zebrafish myh6 knockout revealed that loss of atrial myosin triggers ventricular compensatory hyperplasia rather than hypertrophy, accompanied by ER-stress activation, distinguishing the piscine response from canonical mammalian hypertrophy.","evidence":"Immunohistochemistry, confocal microscopy, qRT-PCR, western blot in myh6−/− zebrafish","pmids":["31129720"],"confidence":"Medium","gaps":["Hyperplasia vs. hypertrophy distinction may reflect zebrafish-specific regenerative capacity","ER-stress pathway as cause vs. consequence not resolved"]},{"year":2020,"claim":"CRISPR/Cas9 correction and reintroduction of the R443P head-domain variant in isogenic iPSC-CMs established bidirectional causality between this motor-domain mutation and impaired sarcomere assembly, MYH6/MYH7 switching, and contractile dysfunction.","evidence":"CRISPR isogenic correction/reintroduction, iPSC-CM contraction assays, immunostaining, patient tissue validation","pmids":["32656206"],"confidence":"High","gaps":["Biochemical mechanism (ATPase, actin affinity) of R443P not directly measured","Long-term maturation effects not studied"]},{"year":2021,"claim":"A coiled-coil tail domain insertion variant was shown to impair myofibril formation and increase apoptosis, with molecular dynamics suggesting altered α-helix and dimer stability as the structural basis—extending the spectrum of disease mechanisms to tail-domain self-aggregation defects.","evidence":"C2C12 transfection, myofibril/apoptosis assays, molecular dynamics simulation","pmids":["34481090"],"confidence":"Medium","gaps":["Molecular dynamics prediction not validated by biophysical measurement of dimer stability","Apoptosis mechanism not explored"]},{"year":2022,"claim":"Functional characterization of MYH6 promoter variants from VSD patients demonstrated that cis-regulatory mutations reduce MYH6 transcription and alter transcription factor binding, establishing a non-coding pathogenic mechanism.","evidence":"Dual luciferase reporter assay and EMSA in cell lines","pmids":["36209093"],"confidence":"Medium","gaps":["Specific transcription factors affected not definitively identified","In vivo promoter activity not tested"]},{"year":2023,"claim":"Replication of the promoter-variant mechanism in Tetralogy of Fallot patients across three cell lines strengthened the generality of reduced MYH6 promoter activity as a pathogenic mechanism across congenital heart defects.","evidence":"Dual luciferase reporter and EMSA in HEK-293, HL-1, H9C2 cell lines","pmids":["38135727"],"confidence":"Medium","gaps":["Endogenous chromatin context not assessed","Causality in animal models not established for TOF-associated variants"]},{"year":2024,"claim":"In vivo echocardiographic measurement in HLHS neonates directly linked MYH6 variant status to atrium-selective contractile impairment, confirming in patients the chamber-specific functional consequence predicted by MYH6 expression patterns.","evidence":"2D speckle-tracking echocardiography with genotype-stratified case-control analysis in neonates","pmids":["39596649"],"confidence":"Medium","gaps":["Small cohort; replication in larger populations needed","Mechanistic basis for preserved RV function not addressed"]},{"year":null,"claim":"Key unresolved questions include the biochemical mechanism by which individual MYH6 mutations alter ATPase kinetics and actin binding, the upstream signals that recruit the BRG1 repressive complex specifically to MYH6, and whether MYH6-driven TGF-β1 secretion from mutant cardiomyocytes is a general feature of HCM pathogenesis.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No single-molecule or purified-protein biophysical studies of disease-associated α-MHC variants","Signal initiating BRG1 recruitment to MYH6 promoter unknown","MYH6-specific contribution to TGF-β1-mediated fibroblast activation not separated from MYH7"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003774","term_label":"cytoskeletal motor activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,8]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0,6]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1,6,9]}],"pathway":[{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[0,6]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,4,5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,5,6,8]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[3]}],"complexes":["cardiac thick filament (myosin)","sarcomere"],"partners":["BRG1","G9A","GLP","DNMT3","MYH7"],"other_free_text":[]},"mechanistic_narrative":"MYH6 encodes the α-myosin heavy chain, the principal sarcomeric motor protein of the atrium, whose head domain drives actin-dependent force generation and whose coiled-coil tail domain mediates thick filament polymerization essential for myofibril assembly and cardiac contractility [PMID:19769958, PMID:20656787, PMID:32656206]. Mutations in the motor head impair sarcomere organization and contractile function with a shift from MYH6 toward MYH7 (β-MHC) expression, while tail-domain truncations or insertions abolish thick filament formation; allele-specific silencing of the dominant R403Q mutant allele is sufficient to prevent hypertrophic cardiomyopathy in vivo [PMID:24092743, PMID:34481090]. Under pathological stress, a BRG1–G9a/GLP–DNMT3 chromatin-repressive complex assembles on the MYH6 promoter, depositing H3K9 and CpG methylation to silence MYH6 transcription and worsen cardiac dysfunction [PMID:26952936]. MYH6 mutations cause familial atrial septal defects and are associated with hypoplastic left heart syndrome, with atrium-selective contractile impairment reflecting the chamber-restricted predominance of α-MHC expression [PMID:22194935, PMID:27789736, PMID:39596649]."},"prefetch_data":{"uniprot":{"accession":"P13533","full_name":"Myosin-6","aliases":["Myosin heavy chain 6","Myosin heavy chain, cardiac muscle alpha isoform","MyHC-alpha"],"length_aa":1939,"mass_kda":223.7,"function":"Muscle contraction","subcellular_location":"Cytoplasm, myofibril","url":"https://www.uniprot.org/uniprotkb/P13533/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MYH6","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MYH6","total_profiled":1310},"omim":[{"mim_id":"616096","title":"MYOSIN HEAVY CHAIN-ASSOCIATED RNA TRANSCRIPT, NONCODING; MHRT","url":"https://www.omim.org/entry/616096"},{"mim_id":"615396","title":"LEFT VENTRICULAR NONCOMPACTION 10; LVNC10","url":"https://www.omim.org/entry/615396"},{"mim_id":"614090","title":"SICK SINUS SYNDROME 3, SUSCEPTIBILITY TO; SSS3","url":"https://www.omim.org/entry/614090"},{"mim_id":"614089","title":"ATRIAL SEPTAL DEFECT 3; ASD3","url":"https://www.omim.org/entry/614089"},{"mim_id":"613613","title":"MICRO RNA 208B; MIR208B","url":"https://www.omim.org/entry/613613"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Focal adhesion sites","reliability":"Uncertain"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"heart muscle","ntpm":4840.4}],"url":"https://www.proteinatlas.org/search/MYH6"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P13533","domains":[{"cath_id":"1.20.5","chopping":"843-970","consensus_level":"medium","plddt":79.0079,"start":843,"end":970}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P13533","model_url":"https://alphafold.ebi.ac.uk/files/AF-P13533-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P13533-F1-predicted_aligned_error_v6.png","plddt_mean":74.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MYH6","jax_strain_url":"https://www.jax.org/strain/search?query=MYH6"},"sequence":{"accession":"P13533","fasta_url":"https://rest.uniprot.org/uniprotkb/P13533.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P13533/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P13533"}},"corpus_meta":[{"pmid":"21378987","id":"PMC_21378987","title":"A rare variant in MYH6 is associated with high risk of sick sinus syndrome.","date":"2011","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21378987","citation_count":247,"is_preprint":false},{"pmid":"20215591","id":"PMC_20215591","title":"Coding sequence rare variants identified in MYBPC3, MYH6, TPM1, TNNC1, and TNNI3 from 312 patients with familial or idiopathic dilated cardiomyopathy.","date":"2010","source":"Circulation. Cardiovascular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20215591","citation_count":199,"is_preprint":false},{"pmid":"24092743","id":"PMC_24092743","title":"Allele-specific silencing of mutant Myh6 transcripts in mice suppresses hypertrophic cardiomyopathy.","date":"2013","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/24092743","citation_count":178,"is_preprint":false},{"pmid":"20656787","id":"PMC_20656787","title":"Alpha-cardiac myosin heavy chain (MYH6) mutations affecting myofibril formation are associated with congenital heart defects.","date":"2010","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20656787","citation_count":120,"is_preprint":false},{"pmid":"22194935","id":"PMC_22194935","title":"Cardiac alpha-myosin (MYH6) is the predominant sarcomeric disease gene for familial atrial septal defects.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22194935","citation_count":74,"is_preprint":false},{"pmid":"27789736","id":"PMC_27789736","title":"Impact of MYH6 variants in hypoplastic left heart syndrome.","date":"2016","source":"Physiological genomics","url":"https://pubmed.ncbi.nlm.nih.gov/27789736","citation_count":73,"is_preprint":false},{"pmid":"26085007","id":"PMC_26085007","title":"Recessive MYH6 Mutations in Hypoplastic Left Heart With Reduced Ejection Fraction.","date":"2015","source":"Circulation. Cardiovascular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26085007","citation_count":68,"is_preprint":false},{"pmid":"29590334","id":"PMC_29590334","title":"A rare missense mutation in MYH6 associates with non-syndromic coarctation of the aorta.","date":"2018","source":"European heart journal","url":"https://pubmed.ncbi.nlm.nih.gov/29590334","citation_count":60,"is_preprint":false},{"pmid":"26952936","id":"PMC_26952936","title":"Epigenetic response to environmental stress: Assembly of BRG1-G9a/GLP-DNMT3 repressive chromatin complex on Myh6 promoter in pathologically stressed hearts.","date":"2016","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/26952936","citation_count":55,"is_preprint":false},{"pmid":"19769958","id":"PMC_19769958","title":"Absence of heartbeat in the Xenopus tropicalis mutation muzak is caused by a nonsense mutation in cardiac myosin myh6.","date":"2009","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/19769958","citation_count":42,"is_preprint":false},{"pmid":"32656206","id":"PMC_32656206","title":"Contractility of Induced Pluripotent Stem Cell-Cardiomyocytes With an MYH6 Head Domain Variant Associated With Hypoplastic Left Heart Syndrome.","date":"2020","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32656206","citation_count":40,"is_preprint":false},{"pmid":"8307559","id":"PMC_8307559","title":"Structural organization of the human cardiac alpha-myosin heavy chain gene (MYH6).","date":"1993","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8307559","citation_count":30,"is_preprint":false},{"pmid":"34697898","id":"PMC_34697898","title":"Identification of MYH6 as the potential gene for human ischaemic cardiomyopathy.","date":"2021","source":"Journal of cellular and molecular 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Heart","date":"2024-06-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.21.600099","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":28645,"output_tokens":4164,"usd":0.074197},"stage2":{"model":"claude-opus-4-6","input_tokens":7615,"output_tokens":3187,"usd":0.176625},"total_usd":0.250822,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"Loss-of-function nonsense mutation in myh6 (cardiac myosin heavy chain) in Xenopus tropicalis muzak mutants deletes the coiled-coil domain required for thick filament polymerization, severely disrupting the cardiomyocyte cytoskeleton and abolishing cardiac contractility, while early cardiac morphogenesis (looping, chamber formation) proceeds normally but valves and trabeculae fail to form.\",\n      \"method\": \"Positional cloning, loss-of-function genetic model (Xenopus tropicalis muzak mutant), histology and cytoskeletal analysis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — first positional cloning in X. tropicalis with defined structural and functional phenotype; ortholog of mammalian MYH6\",\n      \"pmids\": [\"19769958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MYH6 mutations A230P and A1366D significantly disrupt myofibril formation when GFP-MYH6 fusion proteins are expressed in mouse myoblasts, while mutation H252Q significantly enhances myofibril assembly compared to wild-type, demonstrating that specific residues in MYH6 are required for proper sarcomere/myofibril organization.\",\n      \"method\": \"Transfection of GFP-MYH6 fusion constructs (wild-type and mutant) in mouse myoblasts, fluorescence microscopy of myofibril formation\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional cell-based assay with multiple mutants; single lab study\",\n      \"pmids\": [\"20656787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Allele-specific RNAi delivered by AAV selectively silences the R403Q mutant Myh6 transcript in heterozygous HCM mice; a ~25% reduction in mutant transcript levels is sufficient to prevent hypertrophy and myocardial fibrosis for at least 6 months, establishing that partial suppression of the mutant allele blocks HCM pathogenesis.\",\n      \"method\": \"AAV-delivered RNAi in Myh6(R403Q/+) knock-in mice, echocardiography, histology, quantitative RT-PCR\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo loss-of-function with allele-specific approach, multiple phenotypic readouts, highly cited foundational study\",\n      \"pmids\": [\"24092743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Under pathological cardiac stress, BRG1 (nucleosome-remodeling factor) is activated in cardiomyocytes and sequentially recruits G9a/GLP (histone methyltransferase) and DNMT3 (DNA methyltransferase) to assemble repressive chromatin on the Myh6 promoter, marked by H3K9 methylation and CpG methylation, thereby silencing Myh6 and impairing cardiac contraction; disruption of any component of this complex de-represses Myh6 and reduces stress-induced dysfunction.\",\n      \"method\": \"Co-immunoprecipitation of BRG1-G9a-DNMT3 complex, ChIP for H3K9me and CpG methylation on Myh6 promoter, genetic disruption of Brg1/G9a/Dnmt3 in mice, cardiac function assays; validated in human hypertrophic heart tissue\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (Co-IP, ChIP, genetic loss-of-function, human tissue correlation), mechanistic pathway fully reconstituted\",\n      \"pmids\": [\"26952936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In adult zebrafish myh6-/- (weak atrium) mutants, loss of atrial myosin heavy chain leads to atrial hypoplasia with elastin deposition; the compensatory ventricular enlargement occurs predominantly via cardiomyocyte hyperplasia (not hypertrophy), accompanied by activation of mammalian hypertrophy-associated transcriptional profiles and ER-stress pathway activation.\",\n      \"method\": \"Immunohistochemistry, confocal microscopy (cardiomyocyte size/density/proliferation), RT-PCR for hypertrophy markers, western blot for ER stress markers in myh6-/- zebrafish\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic knockout with multiple cellular readouts in zebrafish ortholog; single lab\",\n      \"pmids\": [\"31129720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Patient-derived iPSC-cardiomyocytes from HLHS subjects with MYH6 variants exhibit defective cardiomyogenic differentiation and upregulation of MYH7 (β-myosin heavy chain), mirroring in vivo cardiac tissue expression changes; this establishes that MYH6 variants alter the MYH6/MYH7 balance during cardiomyogenesis.\",\n      \"method\": \"iPSC cardiomyocyte differentiation from HLHS patients, transcriptome and protein expression analysis of cardiac tissue, MYH7 upregulation quantification\",\n      \"journal\": \"Physiological genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — patient iPSC model with in vitro/in vivo correlation; single lab\",\n      \"pmids\": [\"27789736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"iPSC-cardiomyocytes carrying the MYH6-R443P head domain variant show dysmorphic sarcomere structure, increased MYH7 expression replacing MYH6 after differentiation day 15, slower contraction rates, reduced shortening, and slower relaxation; CRISPR/Cas9 correction of R443P rescues sarcomere organization and contractile phenotypes, demonstrating that this variant in the MYH6 motor head directly impairs sarcomere assembly and contractility.\",\n      \"method\": \"iPSC-cardiomyocyte functional assays (contraction rate, shortening, velocity), immunostaining, CRISPR/Cas9 correction and reintroduction of R443P variant, patient cardiac tissue immunostaining\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — CRISPR isogenic correction and reintroduction provide bidirectional causality; multiple functional and structural readouts\",\n      \"pmids\": [\"32656206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The human MYH6 gene consists of 39 exons (37 coding), with the 5'-UTR split across 3 exons and the AUG initiation codon in the third exon; all exon/intron boundaries are conserved with cardiac β-MHC (MYH7) except the 13th intron of MYH7 which is absent in MYH6; the encoded protein sequence was fully determined.\",\n      \"method\": \"Complete genomic sequencing of human MYH6 locus (26,159 bp) and comparative analysis\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — complete structural characterization of gene architecture by direct sequencing\",\n      \"pmids\": [\"8307559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Three MYH6 missense mutations (R17H, C539R, K543R) associated with familial atrial septal defect are all located in the highly conserved alpha-myosin motor domain region involved in myosin-actin interaction, suggesting that perturbation of this actin-binding interface is a mechanism for MYH6-associated congenital heart defects.\",\n      \"method\": \"Array-based resequencing of 13 sarcomeric genes, co-segregation analysis in families, structural and homology analysis of mutation locations\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — genetic segregation plus structural localization; no direct functional actin-binding assay performed\",\n      \"pmids\": [\"22194935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Novel MYH6 insertion variant Arg1822_Glu1823dup in the coiled-coil tail domain significantly impairs myofibril formation and increases apoptosis in transfected C2C12 myoblasts; molecular simulation reveals the variant impairs the myosin α-helix and increases coiled-coil dimer stability, suggesting altered tail domain self-aggregation as a disease mechanism.\",\n      \"method\": \"Transfection of MYH6 variants in C2C12 cells, myofibril formation assay, apoptosis assay, molecular dynamics simulation\",\n      \"journal\": \"European journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — cell-based functional assay plus molecular modeling; single lab\",\n      \"pmids\": [\"34481090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Variants in the MYH6 gene promoter (g.4085G>C and g.4716G>A, identified in VSD patients) significantly reduce MYH6 transcriptional activity as shown by dual luciferase reporter assays, and alter transcription factor binding as shown by electrophoretic mobility shift assays, establishing a regulatory mechanism by which promoter variants reduce MYH6 expression.\",\n      \"method\": \"Dual luciferase reporter assay, electrophoretic mobility shift assay (EMSA), bioinformatics (JASPAR)\",\n      \"journal\": \"BMC medical genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — two orthogonal functional assays (reporter + EMSA) in cellular systems; single lab\",\n      \"pmids\": [\"36209093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MYH6 gene promoter variants found in Tetralogy of Fallot patients reduce MYH6 transcriptional activity in dual luciferase reporter assays and alter transcription factor binding in EMSA across three cell lines (HEK-293, HL-1, H9C2), indicating that reduced MYH6 promoter-driven expression is a pathogenic mechanism in TOF.\",\n      \"method\": \"Dual luciferase reporter assay, EMSA in three cell lines, bioinformatics (JASPAR)\",\n      \"journal\": \"Pediatric research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — two orthogonal functional assays replicated in three cell lines; single lab\",\n      \"pmids\": [\"38135727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MYH6 variants in HLHS neonates are associated with impaired right atrial active contractility (reduced RA active strain) as measured by 2D speckle-tracking echocardiography, while RV function is preserved; RA reservoir and conduit strain correlate with heart rate only in variant carriers, demonstrating atrium-specific functional impairment consistent with the atrial predominance of MYH6 expression.\",\n      \"method\": \"2D speckle-tracking echocardiography in neonates, strain and strain rate analysis, case-control comparison\",\n      \"journal\": \"Genes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo functional measurement tied to MYH6 genotype with matched controls; single study\",\n      \"pmids\": [\"39596649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MYH6 overexpression suppresses proliferation and migration of prostate cancer cells in vitro and in vivo; RNA-seq identified KIT proto-oncogene as a downstream target downregulated by MYH6, and rescue assays confirmed that MYH6's tumor-suppressive effects are mediated through downregulation of KIT expression.\",\n      \"method\": \"Overexpression in prostate cancer cell lines, proliferation and migration assays, xenograft in vivo model, RNA-seq, rescue assays with KIT\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays with downstream target validation by rescue; single lab, non-cardiac context\",\n      \"pmids\": [\"39181964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A gene regulatory enhancer element interacts directly with the MYH6 locus (confirmed by chromatin conformation assays) and controls MYH6 expression; epigenome editing-mediated enhancer activation alters cardiomyocyte response to endothelin-1 stress, preventing polyploidization and changes in calcium dynamics, establishing that enhancer-mediated MYH6 regulation modulates cardiomyocyte stress response and maturation.\",\n      \"method\": \"Chromatin conformation assays (3C/Hi-C type), epigenome editing, endothelin-1 stress assay, calcium dynamics measurement, polyploidy analysis in hiPSC-derived cardiomyocytes\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — chromatin conformation plus epigenome editing with functional readouts; preprint, not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"hiPSC-CMs carrying HCM-associated MYH6-R725C and MYH7-R723C mutations in 3D engineered heart tissues show elevated TGF-β1 secretion specifically from mutant cardiomyocytes, increased activated fibroblasts, and augmented contraction force; blocking TGF-β1 receptor signaling normalizes fibroblast activation and force to control levels, placing mutant MYH6/7-driven TGF-β1 overexpression upstream of fibroblast activation.\",\n      \"method\": \"3D engineered heart tissue (EHT) model, ELISA/secretion assay for TGF-β1, fibroblast activation markers, contraction force measurement, TGF-β receptor antagonist rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2–3 — preprint with functional assays but MYH6 and MYH7 mutations analyzed together, making MYH6-specific attribution uncertain\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"MYH6 encodes the α-myosin heavy chain, a core sarcomeric motor protein that polymerizes via its coiled-coil tail domain into thick filaments and drives cardiac contraction through actin interaction via its head/motor domain; its expression is epigenetically regulated in stressed hearts by a BRG1-G9a/GLP-DNMT3 repressive chromatin complex assembled on the MYH6 promoter, and by enhancer elements that modulate cardiomyocyte stress responses; loss or mutation of MYH6 disrupts myofibril formation, impairs contractility (especially atrial), shifts MYH6/MYH7 balance toward fetal β-MHC, and can trigger downstream TGF-β1-mediated fibroblast activation, while allele-specific silencing of dominant gain-of-function mutations is sufficient to prevent hypertrophic cardiomyopathy pathology in vivo.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MYH6 encodes the α-myosin heavy chain, the principal sarcomeric motor protein of the atrium, whose head domain drives actin-dependent force generation and whose coiled-coil tail domain mediates thick filament polymerization essential for myofibril assembly and cardiac contractility [PMID:19769958, PMID:20656787, PMID:32656206]. Mutations in the motor head impair sarcomere organization and contractile function with a shift from MYH6 toward MYH7 (β-MHC) expression, while tail-domain truncations or insertions abolish thick filament formation; allele-specific silencing of the dominant R403Q mutant allele is sufficient to prevent hypertrophic cardiomyopathy in vivo [PMID:24092743, PMID:34481090]. Under pathological stress, a BRG1–G9a/GLP–DNMT3 chromatin-repressive complex assembles on the MYH6 promoter, depositing H3K9 and CpG methylation to silence MYH6 transcription and worsen cardiac dysfunction [PMID:26952936]. MYH6 mutations cause familial atrial septal defects and are associated with hypoplastic left heart syndrome, with atrium-selective contractile impairment reflecting the chamber-restricted predominance of α-MHC expression [PMID:22194935, PMID:27789736, PMID:39596649].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Complete genomic characterization of MYH6 established its 39-exon architecture and near-identity with the MYH7 locus, providing the structural framework needed to interpret subsequent disease-associated variants.\",\n      \"evidence\": \"Full genomic sequencing (26,159 bp) and comparative analysis with MYH7\",\n      \"pmids\": [\"8307559\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional data on promoter or regulatory elements at this stage\", \"No disease mutation mapping yet performed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Positional cloning of the Xenopus muzak mutant demonstrated that the MYH6 coiled-coil tail domain is essential for thick filament assembly and cardiac contractility, while dispensable for early cardiac morphogenesis.\",\n      \"evidence\": \"Positional cloning and cytoskeletal/histological analysis in X. tropicalis muzak loss-of-function mutant\",\n      \"pmids\": [\"19769958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Xenopus ortholog; direct extrapolation to mammalian MYH6 function required confirmation\", \"No motor-domain-specific functional dissection\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Expression of disease-associated MYH6 point mutants in myoblasts revealed that specific residues in both the head and tail domains are required for proper myofibril formation, separating gain-of-assembly from loss-of-assembly variants.\",\n      \"evidence\": \"GFP-MYH6 wild-type and mutant fusion construct transfection in mouse myoblasts with fluorescence microscopy\",\n      \"pmids\": [\"20656787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Overexpression in non-cardiomyocyte cell line; physiological relevance in cardiomyocytes not confirmed\", \"No contractile or mechanical readouts\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of MYH6 motor-domain missense mutations co-segregating with familial atrial septal defects placed the myosin-actin interaction interface as a critical determinant of congenital heart structure.\",\n      \"evidence\": \"Array-based sarcomeric gene resequencing, family co-segregation analysis, structural homology mapping\",\n      \"pmids\": [\"22194935\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct actin-binding or ATPase functional assays performed for the identified variants\", \"Structural inference based on homology, not crystal structure of α-MHC\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Allele-specific RNAi silencing of the R403Q mutant Myh6 allele in vivo proved that even partial (~25%) suppression of the gain-of-function transcript prevents hypertrophic cardiomyopathy, establishing a therapeutic paradigm for dominant sarcomeric mutations.\",\n      \"evidence\": \"AAV-delivered allele-specific RNAi in Myh6(R403Q/+) knock-in mice with echocardiography, histology, and qRT-PCR\",\n      \"pmids\": [\"24092743\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term durability beyond 6 months not assessed\", \"Translation to human MYH6 sequence context not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery that a BRG1–G9a/GLP–DNMT3 repressive complex assembles on the MYH6 promoter under cardiac stress explained how pathological signaling epigenetically silences α-MHC to drive the fetal gene re-expression program and contractile dysfunction.\",\n      \"evidence\": \"Co-IP, ChIP (H3K9me, CpG methylation), genetic disruption of Brg1/G9a/Dnmt3 in mice, validation in human hypertrophic heart tissue\",\n      \"pmids\": [\"26952936\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream signal that activates BRG1 recruitment to MYH6 specifically remains undefined\", \"Relative contribution of H3K9me vs CpG methylation not dissected\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Patient iPSC-cardiomyocytes with MYH6 variants recapitulated the MYH6-to-MYH7 isoform shift observed in HLHS cardiac tissue, providing a human cellular model linking MYH6 haploinsufficiency to defective cardiomyogenesis and β-MHC compensation.\",\n      \"evidence\": \"iPSC-CM differentiation from HLHS patients, transcriptome and protein expression analysis\",\n      \"pmids\": [\"27789736\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific MYH6 variants not functionally isolated from genetic background\", \"Mechanism by which MYH6 loss upregulates MYH7 not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Zebrafish myh6 knockout revealed that loss of atrial myosin triggers ventricular compensatory hyperplasia rather than hypertrophy, accompanied by ER-stress activation, distinguishing the piscine response from canonical mammalian hypertrophy.\",\n      \"evidence\": \"Immunohistochemistry, confocal microscopy, qRT-PCR, western blot in myh6−/− zebrafish\",\n      \"pmids\": [\"31129720\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hyperplasia vs. hypertrophy distinction may reflect zebrafish-specific regenerative capacity\", \"ER-stress pathway as cause vs. consequence not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"CRISPR/Cas9 correction and reintroduction of the R443P head-domain variant in isogenic iPSC-CMs established bidirectional causality between this motor-domain mutation and impaired sarcomere assembly, MYH6/MYH7 switching, and contractile dysfunction.\",\n      \"evidence\": \"CRISPR isogenic correction/reintroduction, iPSC-CM contraction assays, immunostaining, patient tissue validation\",\n      \"pmids\": [\"32656206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism (ATPase, actin affinity) of R443P not directly measured\", \"Long-term maturation effects not studied\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A coiled-coil tail domain insertion variant was shown to impair myofibril formation and increase apoptosis, with molecular dynamics suggesting altered α-helix and dimer stability as the structural basis—extending the spectrum of disease mechanisms to tail-domain self-aggregation defects.\",\n      \"evidence\": \"C2C12 transfection, myofibril/apoptosis assays, molecular dynamics simulation\",\n      \"pmids\": [\"34481090\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular dynamics prediction not validated by biophysical measurement of dimer stability\", \"Apoptosis mechanism not explored\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Functional characterization of MYH6 promoter variants from VSD patients demonstrated that cis-regulatory mutations reduce MYH6 transcription and alter transcription factor binding, establishing a non-coding pathogenic mechanism.\",\n      \"evidence\": \"Dual luciferase reporter assay and EMSA in cell lines\",\n      \"pmids\": [\"36209093\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific transcription factors affected not definitively identified\", \"In vivo promoter activity not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Replication of the promoter-variant mechanism in Tetralogy of Fallot patients across three cell lines strengthened the generality of reduced MYH6 promoter activity as a pathogenic mechanism across congenital heart defects.\",\n      \"evidence\": \"Dual luciferase reporter and EMSA in HEK-293, HL-1, H9C2 cell lines\",\n      \"pmids\": [\"38135727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous chromatin context not assessed\", \"Causality in animal models not established for TOF-associated variants\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"In vivo echocardiographic measurement in HLHS neonates directly linked MYH6 variant status to atrium-selective contractile impairment, confirming in patients the chamber-specific functional consequence predicted by MYH6 expression patterns.\",\n      \"evidence\": \"2D speckle-tracking echocardiography with genotype-stratified case-control analysis in neonates\",\n      \"pmids\": [\"39596649\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Small cohort; replication in larger populations needed\", \"Mechanistic basis for preserved RV function not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the biochemical mechanism by which individual MYH6 mutations alter ATPase kinetics and actin binding, the upstream signals that recruit the BRG1 repressive complex specifically to MYH6, and whether MYH6-driven TGF-β1 secretion from mutant cardiomyocytes is a general feature of HCM pathogenesis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No single-molecule or purified-protein biophysical studies of disease-associated α-MHC variants\", \"Signal initiating BRG1 recruitment to MYH6 promoter unknown\", \"MYH6-specific contribution to TGF-β1-mediated fibroblast activation not separated from MYH7\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003774\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1, 6, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 4, 5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 5, 6, 8]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"cardiac thick filament (myosin)\",\n      \"sarcomere\"\n    ],\n    \"partners\": [\n      \"BRG1\",\n      \"G9a\",\n      \"GLP\",\n      \"DNMT3\",\n      \"MYH7\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}