{"gene":"MYF5","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1990,"finding":"MYF5 contains an intrinsic transcriptional activation domain distinct from its helix-loop-helix (HLH) motif, located predominantly in the C-terminal half of the protein. High-affinity, sequence-specific DNA binding requires hetero-oligomeric association with the ubiquitous HLH protein E12 to confer muscle-specific transactivation.","method":"GAL4-fusion transactivation assay with reporter plasmid; heterodimerization with E12","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro transactivation assay with domain mapping and heterodimerization experiments, foundational biochemical characterization","pmids":["2385294"],"is_preprint":false},{"year":1992,"finding":"Site-directed mutagenesis of MYF5 revealed that two clusters of basic amino acids in the conserved basic region and two amphipathic helices in the HLH domain are essential for sequence-specific DNA binding and hetero-oligomerization, respectively. Transcriptional activation requires two additional cooperative domains in the amino- and carboxyl-termini; deletion of either abolishes activity. Dimerization with E12 increases both DNA-binding affinity and transactivation independently of DNA binding. Muscle-specific transactivation requires collaboration of the two activation domains together with the DNA-binding region.","method":"Site-directed mutagenesis; chimeric GAL4-Myf5 fusion reporter assays; co-transfection transactivation assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutagenesis and multiple orthogonal reporter assays in a single rigorous study","pmids":["1582413"],"is_preprint":false},{"year":1993,"finding":"PKA phosphorylates MYF5 and MyoD in vitro but does not affect their DNA-binding ability. Nevertheless, elevated cAMP/PKA represses the transcriptional activation of muscle-specific genes by MYF5 and MyoD through the basic HLH domain and E-box motif, acting post-translationally at a step after DNA binding, specifically inhibiting myogenic bHLH proteins but not ubiquitous HLH proteins E12/E47.","method":"In vitro PKA phosphorylation assay; reporter co-transfection; dominant-negative and overexpression of PKA catalytic subunit","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus functional reporter experiments with multiple lines of evidence in one study","pmids":["8387507"],"is_preprint":false},{"year":1993,"finding":"All four MRFs including MYF5 can transactivate the mouse desmin gene through E-box elements in its promoter and enhancer, as demonstrated by co-transfection of each factor with desmin-CAT constructs into 10T1/2 cells.","method":"Co-transfection reporter assay (desmin-CAT); gel electrophoretic mobility shift assay (EMSA)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro transactivation assay, single lab, single method for MYF5 specifically","pmids":["8382796"],"is_preprint":false},{"year":1993,"finding":"Ectopic expression of bovine MYF5 (bmyf) in transgenic mice under a viral promoter caused ectopic skeletal muscle differentiation in brain and heart, activating endogenous skeletal myogenic determination genes, demonstrating that MYF5 can initiate myogenic differentiation in vivo.","method":"Transgenic mouse overexpression; histology; in situ hybridization; immunohistochemistry","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo gain-of-function with multiple tissue readouts, direct demonstration of ectopic myogenesis","pmids":["8413206"],"is_preprint":false},{"year":1994,"finding":"MYF5 alone (without MyoD, myogenin, or MRF4) is sufficient to establish and maintain the myoblast phenotype in C3H10T1/2 mesenchymal cells, but cross-activation of other endogenous MRF genes does not occur at the myoblast stage in these cells; autoactivation of the Myf5 gene also does not occur.","method":"Stable transfection of C3H10T1/2 cells with MRF cDNAs; RT-PCR; phenotypic characterization","journal":"Differentiation; research in biological diversity","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean loss/gain-of-function cell system, single lab","pmids":["8187980"],"is_preprint":false},{"year":1995,"finding":"MYF5 expression is restricted to a subset of subdomains in the embryonic brain (mesencephalon and secondary prosencephalon), where it functions as an axonal marker but does not cause myogenic conversion, as Myf5 protein is absent in neurons despite correct mRNA splicing, indicating post-transcriptional regulation of Myf5 specifically in neurons.","method":"Gene-targeted nlacZ knock-in mouse; beta-galactosidase reporter expression; immunofluorescence; immunoblotting; RT-PCR","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — knock-in reporter mouse combined with protein detection and RT-PCR demonstrating translational/stability regulation in neurons","pmids":["8575308"],"is_preprint":false},{"year":1997,"finding":"Genetic epistasis experiments using Pax-3 (splotch) and Myf-5 double homozygous mutant mice showed complete absence of body muscles not seen in individual mutants, because MyoD activation depends on either Pax-3 or Myf-5. Therefore Pax-3 and Myf-5 define two distinct upstream myogenic pathways and MyoD acts genetically downstream of both in the body.","method":"Genetic epistasis using double homozygous mutant mice (Pax3/Myf5); lacZ reporter for lineage tracing; histology","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — double-mutant epistasis independently establishing pathway hierarchy, replicated across multiple groups","pmids":["9094721"],"is_preprint":false},{"year":1997,"finding":"Ectopic Pax-3 retroviral infection in embryonic tissues is sufficient to induce expression of MyoD, Myf-5, and myogenin in paraxial and lateral plate mesoderm and the neural tube in the absence of inducing tissues, placing Pax-3 upstream of both MYF5 and MyoD.","method":"Retroviral infection of chick embryo explants; in situ hybridization","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — gain-of-function retroviral experiment in chick embryos with direct molecular readout","pmids":["9094722"],"is_preprint":false},{"year":1997,"finding":"Myf-5 and MyoD define development of distinct muscle compartments: Myf5(-/-) embryos showed delayed epaxial (paraspinal/intercostal) but normal limb muscle development, while MyoD(-/-) embryos showed delayed limb but normal epaxial muscle development, indicating that Myf-5 is specifically required for epaxial and MyoD for hypaxial myogenesis.","method":"Knockout mouse analysis; immunohistochemistry; in situ hybridization for multiple muscle markers","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple knockout mouse lines, multiple orthogonal markers, independently replicated across labs","pmids":["9428409"],"is_preprint":false},{"year":1996,"finding":"Myf-5 and MyoD are not expressed in the same muscle precursor cell but rather determine different muscle cell lineages arising from independently committed stem cell populations. Selective ablation of Myf5-expressing precursors from differentiating ES cells does not prevent MyoD-dependent muscle differentiation, and early Myf5-progenitors do not develop into later MyoD cells even when Myf5 is inactivated.","method":"Selective cell ablation in differentiating ES cells; lineage analysis; immunofluorescence","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell ablation experiments with lineage analysis, multiple approaches","pmids":["8617206"],"is_preprint":false},{"year":1996,"finding":"Targeted knock-in of myogenin cDNA into the Myf5 locus (replacing Myf5 function) rescued rib cage defects and viability in Myf5-null mice, demonstrating functional redundancy of Myf5 and myogenin for rib formation.","method":"Homologous recombination knock-in mouse; phenotypic rescue analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — precise genetic rescue experiment demonstrating functional equivalence at the same locus","pmids":["8587605"],"is_preprint":false},{"year":1998,"finding":"Wnt1 (from dorsal neural tube) preferentially activates Myf5, while Wnt7a (from dorsal ectoderm) preferentially activates MyoD in paraxial mesoderm explants, demonstrating that different Wnt molecules activate myogenesis through distinct pathways acting on MYF5 and MyoD differentially.","method":"Paraxial mesoderm explant culture with Wnt-expressing cells; lacZ reporter for Myf5 (Myf5-nlacZ mice); in situ hybridization","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — explant culture system with specific ligands and genetic reporters, multiple Wnt molecules tested","pmids":["9753670"],"is_preprint":false},{"year":1998,"finding":"RhoA GTPase and serum response factor (SRF) selectively control MyoD expression without affecting Myf5 expression in mouse myoblasts. Blocking RhoA activity or inactivating SRF extinguishes MyoD but not Myf5, demonstrating that MyoD and Myf5 are regulated by different upstream signaling cascades.","method":"Dominant-negative RhoA; C3-transferase; lovastatin treatment; SRF inactivation; immunoblot; promoter-reporter assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological and genetic tools with reporter and protein readouts in a single study","pmids":["9658178"],"is_preprint":false},{"year":1998,"finding":"MYF5 protein undergoes cell cycle-regulated expression in proliferating myoblasts: it is high in G0, decreases during G1, reappears at end of G1 and is stable until mitosis. Myf5 is proteolytically degraded in a phosphorylation-dependent manner specifically in mitotic cells (G2/M), representing the first transcription factor shown to undergo cell cycle-regulated degradation.","method":"Immunoblotting of synchronized cultures; nocodazole mitotic block; immunocytolocalization; cell cycle analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical demonstration of cell cycle-phase-specific protein phosphorylation and proteolysis, multiple synchronization methods","pmids":["9425159"],"is_preprint":false},{"year":1998,"finding":"In proliferating C2 myoblasts, MyoD and Myf-5 expression patterns are mutually exclusive during differentiation. Cell cycle analysis showed MYF5 protein is high in G0 and S/G2/M but falls in G1, while MyoD peaks in mid-G1. High Myf5 (low MyoD) correlates with failure to differentiate, and high MyoD (low Myf5) correlates with entry into differentiation.","method":"Immunofluorescence; cell synchronization; immunoblot; isolation of undifferentiated subpopulations","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — synchronized cultures with multiple protein-level readouts and functional differentiation correlation","pmids":["9744876"],"is_preprint":false},{"year":1999,"finding":"Sonic hedgehog (Shh) has an essential inductive function for early activation of Myf5 (and MyoD) specifically in epaxial somite cells in the mouse embryo. Myf5, not MyoD, is the direct target of Shh signaling in the epaxial dermomyotome, as shown by failure of MyoD activation by recombinant Shh in presomitic mesoderm explants from Myf5-null embryos.","method":"Shh-null mouse analysis; presomitic mesoderm explants with recombinant Shh protein; Myf5-null mouse cross; in situ hybridization","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — null mutant combined with explant rescue experiments, independently replicated across labs","pmids":["10457014"],"is_preprint":false},{"year":2000,"finding":"The Myf5 gene is controlled by multiple discrete and dispersed enhancers spread throughout 14 kb spanning the MRF4/Myf5 locus, each driving reporter expression in a particular subset of skeletal muscle precursors. Separate enhancers control epaxial body, some hypaxial body, facial muscle, and CNS expression, demonstrating modular long-range transcriptional control.","method":"Transgenic mouse reporter analysis; lacZ transgene constructs with various upstream deletions","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple independent transgenic lines with systematic deletion mapping, replicated across labs","pmids":["10934019"],"is_preprint":false},{"year":2000,"finding":"Quiescent satellite cells express both CD34 and MYF5 (via beta-galactosidase activity in Myf5-nlacZ mice), and all CD34-positive satellite cells co-express MYF5, establishing MYF5 as a marker of committed, quiescent muscle satellite cells.","method":"Isolated myofiber preparation; immunofluorescence; Myf5-nlacZ knock-in reporter mice; flow cytometry","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic reporter plus immunofluorescence on primary tissue, multiple markers co-analyzed","pmids":["11121437"],"is_preprint":false},{"year":2000,"finding":"MYF5 protein is absent in neurons despite correct splicing of Myf5 mRNA, indicating that post-transcriptional regulation (at the level of mRNA translation or protein stability) prevents Myf5 protein accumulation in neurons, which accounts for the lack of myogenic conversion in the brain.","method":"Immunofluorescence; immunoblotting; RT-PCR in brain neurons; Myf5-nlacZ transgenic mice; retrograde DiI labeling","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — protein and mRNA detection in same tissue, genetic reporter, multiple methods","pmids":["10603349"],"is_preprint":false},{"year":2001,"finding":"Delta1-activated Notch signaling in chick limb bud inhibits muscle differentiation by preventing Myf5-expressing myoblasts from progressing to the MyoD-expressing stage, without affecting Myf5 or Pax3 expression, placing Notch action between the Myf5 and MyoD steps in the myogenic hierarchy.","method":"Retroviral misexpression of Delta1 in chick limb; in situ hybridization for Myf5, Pax3, MyoD; immunohistochemistry","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo gain-of-function with multiple molecular readouts placing Notch between Myf5 and MyoD steps","pmids":["11060246"],"is_preprint":false},{"year":2002,"finding":"Myf5 is a direct target of long-range Shh signaling through positive regulation by Gli transcription factors. A Gli-binding site within the Myf5 epaxial somite (ES) enhancer is required for enhancer activation by Shh signaling in transfected 3T3 cells and in transgenic embryos; deletion of this Gli site abolishes activity in Shh-null embryos.","method":"Transgenic lacZ reporter analysis; luciferase reporter in Shh-responsive 3T3 cells; Gli-site mutagenesis; Shh heterozygous and homozygous null embryo analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — enhancer mutagenesis combined with in vivo transgenic validation and null mutant analysis","pmids":["11782449"],"is_preprint":false},{"year":2003,"finding":"p300 acetyltransferase (HAT) activity is specifically required for induction of Myf5 and MyoD expression upstream of these MRFs; embryos lacking p300 protein show severely attenuated Myf5 induction, while ES cells with p300 null or HAT-dead mutations fail to activate Myf5 efficiently despite normal Pax3 expression. CBP HAT activity is not required for Myf5 activation.","method":"Genetic mouse knockouts and ES cells with point mutations (p300 AT-dead, p300 null, CBP AT-dead); RT-PCR; immunostaining","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple allelic series of knockouts with molecular readouts, places p300 HAT activity upstream of Myf5","pmids":["14517256"],"is_preprint":false},{"year":2004,"finding":"In the absence of both Myf5 and MyoD, Mrf4 expression (when intact) is sufficient to confer skeletal muscle identity, revising the epistatic relationship: both Myf5 and Mrf4 act upstream of MyoD as muscle determination genes.","method":"Allelic series of three Myf5 mutants differentially affecting Mrf4 expression; Myf5:MyoD double-null mice; histology; molecular analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — allelic series with genetic epistasis, multiple mutant combinations, replicated","pmids":["15386014"],"is_preprint":false},{"year":2006,"finding":"Canonical Wnt/beta-catenin signaling directly activates Myf5 transcription in epaxial somite progenitors via Frizzled receptors (Fz1 and/or Fz6) and Tcf/Lef-binding sites immediately 5' to the Myf5 early epaxial enhancer. Blocking Wnt/beta-catenin dramatically reduces Myf5 activation, while activated beta-catenin is sufficient to activate Myf5 in somites. The Wnt/beta-catenin and Shh/Gli pathways act synergistically.","method":"Tcf/Lef site mutation in transgenic mice; gain-of-function and loss-of-function of beta-catenin in somites; Frizzled knockdown; reporter assays","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis of regulatory elements in vivo combined with gain/loss-of-function, multiple orthogonal methods","pmids":["16936075"],"is_preprint":false},{"year":2007,"finding":"Six1 and Six4 homeoproteins bind a 145-bp Myf5 limb enhancer element (at -57.5 kb) in vitro (EMSA) and in vivo (ChIP), and Six1 transactivates a reporter under the control of this sequence. Myf5 expression is severely impaired in limb buds of Six1(-/-) and Six1(-/-)/Six4(-/+) mutant mice despite presence of myogenic progenitors, establishing Six1/4 as direct upstream regulators of Myf5 in limb myogenesis.","method":"EMSA; ChIP with embryonic extracts; transactivation reporter assay; transgenic enhancer mutagenesis; Six1/Six4 mutant mouse analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding plus in vivo ChIP plus enhancer mutagenesis plus genetic knockout, multiple orthogonal methods","pmids":["17592144"],"is_preprint":false},{"year":2007,"finding":"Myf5-null adult mice exhibit perturbed muscle regeneration with increased fiber hypertrophy, delayed differentiation, adipocyte accumulation, and fibrosis after freeze-injury. Mrf4 is not expressed in normal or Myf5-null satellite cells, excluding Mrf4 from a role in adult muscle progenitors. Myf5-null myoblasts show impaired proliferation in vitro.","method":"Myf5-null mouse; freeze-injury regeneration model; histology; satellite cell isolation; in vitro proliferation assay","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — null mouse with in vivo and in vitro readouts, defines Myf5 role in adult regeneration","pmids":["17961534"],"is_preprint":false},{"year":2008,"finding":"Lineage tracing and conditional cell ablation demonstrated two distinct myogenic lineages in mouse skeletal muscle: a Myf5-lineage and a Myf5-independent lineage. Ablating the Myf5 lineage is compatible with myogenesis sustained by Myf5-independent, MyoD-expressing myoblasts. Myf5-lineage cells also contribute significantly to rib development.","method":"Conditional cell ablation using Myf5-Cre; Cre-dependent reporter lineage tracing; genetic mouse crosses","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional cell ablation plus lineage tracing, multiple genetic tools","pmids":["18331721"],"is_preprint":false},{"year":2009,"finding":"DUX4c over-expression induces MYF5 protein and its DNA-binding activity in human myoblasts. DUX4c and MYF5 interact by co-immunoprecipitation, suggesting DUX4c stabilizes MYF5 protein. DUX4c-induced MYF5 increase promotes myoblast proliferation and inhibits differentiation.","method":"Western blot; DNA-binding assay; co-immunoprecipitation; overexpression in primary human myoblasts","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single Co-IP for interaction, overexpression with functional readout, single lab","pmids":["19829708"],"is_preprint":false},{"year":2010,"finding":"A Pax3/Dmrt2/Myf5 regulatory cascade operates in epaxial dermomyotome stem cells: Pax3 directly binds a conserved sequence at -18 kb from Dmrt2 (shown by gel shift and ChIP), Dmrt2 directly binds and transactivates the Myf5 early epaxial enhancer (shown by gel shift and transactivation assay), and conditional Dmrt2 overexpression in Pax3-expressing somite cells activates Myf5.","method":"Gel shift (EMSA); ChIP; transgenic enhancer analysis; Dmrt2 mutant embryo analysis; conditional overexpression","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — EMSA plus in vivo ChIP plus enhancer mutagenesis plus gain/loss-of-function genetics, multiple orthogonal methods","pmids":["20368965"],"is_preprint":false},{"year":2011,"finding":"Zic1 and Zic2 co-localize with Myf5 and Pax3 in the dorsal medial dermomyotome and potentiate Gli-dependent activation of the Myf5 epaxial somite enhancer. Zic2 co-immunoprecipitates with Gli2, indicating Zic2 forms complexes with Gli2 to promote Myf5 expression. Myf5 expression in newly forming somites is deficient in Zic2 mutant embryos.","method":"In situ hybridization; immunohistochemistry; functional reporter assays in 3T3 cells; co-immunoprecipitation; Zic2 mutant mouse analysis; presomitic mesoderm explants","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional reporter plus in vivo genetic mutant, multiple methods","pmids":["21211521"],"is_preprint":false},{"year":2012,"finding":"In quiescent satellite cells, Myf5 mRNA is sequestered in mRNP granules together with microRNA-31 which suppresses its translation. Upon satellite cell activation, mRNP granules dissociate, miR-31 levels decrease, and Myf5 protein accumulates via translation (not transcription). Conditions maintaining mRNP granules delay myogenesis; manipulating miR-31 levels affects satellite cell differentiation and muscle regeneration in vivo.","method":"RNA immunoprecipitation; FISH for mRNP granules; miR-31 manipulation (overexpression/knockdown); in vitro translation assay; satellite cell ex vivo culture; in vivo muscle regeneration","journal":"Cell stem cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (RIP, FISH, functional miRNA manipulation, in vivo) establishing post-transcriptional mechanism","pmids":["22770245"],"is_preprint":false},{"year":2013,"finding":"Emerin associates with the Myf5 genomic locus in proliferating myogenic progenitors (ChIP). Before transcriptional activation, the Myf5 locus localizes to the nuclear lamina; upon activation during differentiation it moves to the nucleoplasm. Both emerin and HDAC3 are required for proper Myf5 localization to the nuclear lamina and its repression; activation of HDAC3 catalytic activity rescues Myf5 lamina localization.","method":"Chromatin immunoprecipitation (ChIP); fluorescence in situ hybridization (FISH) for nuclear position; emerin and HDAC3 knockdown; HDAC3 catalytic activation","journal":"Chromosome research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ChIP plus FISH for localization, single lab, functional connection to expression","pmids":["24062260"],"is_preprint":false},{"year":2013,"finding":"Pax3 synergizes with Gli2 and Zic1 in transactivating the Myf5 epaxial somite (ES) enhancer. This synergy requires conserved functional domains of each protein, a novel homeodomain motif in the Myf5 promoter, and the essential Gli motif in the ES enhancer. Overexpression of Zic1 and Pax3 in 10T1/2 cells results in their enrichment at the endogenous Myf5 locus (ChIP) and induction of Myf5 expression.","method":"Transactivation reporter assay; domain mutagenesis; ChIP at endogenous Myf5 locus; overexpression in 10T1/2 cells","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reporter assay with mutagenesis plus in vivo ChIP at endogenous locus, multiple factor combinations tested","pmids":["24036067"],"is_preprint":false},{"year":2016,"finding":"MYF5 and MyoD bind the same genomic sites genome-wide but have distinct molecular functions: Myf5 induces histone acetylation without Pol II recruitment or robust gene activation, whereas MyoD induces histone acetylation, recruits Pol II, and robustly activates gene transcription. Thus initial muscle lineage specification by Myf5 occurs without significant induction of gene transcription.","method":"ChIP-seq for MYF5, MyoD, histone marks, Pol II; genome-wide binding comparison in myoblasts","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — genome-wide ChIP-seq with multiple marks, rigorous comparison of two factors at same loci","pmids":["26906734"],"is_preprint":false},{"year":2016,"finding":"MYF5 functions as an RNA-binding protein in myoblasts, associating with a subset of mRNAs including Ccnd1 (Cyclin D1) mRNA. MYF5 binds the 3' UTR and coding region of Ccnd1 mRNA (shown by biotin-RNA pulldown, UV-crosslinking, gel shift, and RIP), promotes CCND1 protein translation, and modestly increases Ccnd1 transcription. MYF5-dependent CCND1 upregulation is required for normal myoblast proliferation and differentiation.","method":"Ribonucleoprotein immunoprecipitation (RIP); biotin-RNA pulldown; UV crosslinking; gel shift (EMSA); MYF5 knockdown/overexpression; polysome profiling implied; rescue by CCND1 restoration","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal binding assays (RIP, pulldown, UV-crosslink, EMSA) plus functional rescue experiments","pmids":["26819411"],"is_preprint":false},{"year":2018,"finding":"Satellite cells lacking both MyoD and Myf5 (double knockout) are maintained in uninjured muscle but fail to regenerate injured muscle; dKO satellite cell progeny accumulate in damaged muscle without undergoing muscle differentiation, demonstrating an absolute requirement for either MyoD or Myf5 in muscle regeneration and showing their expression stabilizes myogenic identity.","method":"Conditional double knockout (MyoD/Myf5) in satellite cells; muscle injury model; histology; immunofluorescence; lineage tracing","journal":"Stem cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional double-KO with injury model, multiple molecular and cellular readouts","pmids":["29478898"],"is_preprint":false},{"year":2018,"finding":"SNAIL transcription factor binds to the MYF5 promoter and suppresses its expression. SNAIL silencing in alveolar rhabdomyosarcoma cells allows re-expression of MYF5 and promotes myogenic differentiation. SNAIL forms a repressive complex with HDAC1/2 to regulate MYF5 and other differentiation genes.","method":"ChIP for SNAIL at MYF5 promoter; SNAIL knockdown; reporter assays; co-immunoprecipitation of SNAIL-HDAC1/2 complex; xenograft tumor model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ChIP plus Co-IP plus functional knockdown, single lab","pmids":["29844345"],"is_preprint":false},{"year":2019,"finding":"MLL1 transcriptionally regulates Myf5 by mediating H3K4me3 on its promoter. ChIP showed H3K4me3 enrichment at the Myf5 promoter is MLL1-dependent; MLL1 knockdown reduced Myf5 expression and caused G1 cell cycle arrest in myoblasts. MLL1 is required for satellite cell proliferation and muscle repair in vivo.","method":"ChIP for H3K4me3 at Myf5 promoter; siRNA knockdown of MLL1; cell cycle analysis; cardiotoxin injury model in vivo","journal":"Cell proliferation","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ChIP plus knockdown functional assay, single lab","pmids":["31840352"],"is_preprint":false},{"year":2012,"finding":"PTEN deletion with myf5-Cre selectively expands Myf5-lineage adipocytes, causing lipomatosis and partial lipodystrophy, demonstrating that PI3K/PTEN signaling specifically controls the Myf5+ adipocyte lineage and that Myf5+ mesenchymal precursors give rise not only to brown adipocytes and muscle but also to subsets of white adipocytes.","method":"Conditional Pten knockout using Myf5-Cre; lineage tracing; fat depot analysis; histology","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with lineage tracing, defined cellular phenotype, multiple depot analyses","pmids":["22940198"],"is_preprint":false},{"year":2003,"finding":"TGF-beta1 treatment of retinal pericytes induces nuclear translocation of Myf5 (along with Smad2), switching cells from a growth-potentiated to growth-arrested/contractile phenotype marked by alpha-SMA upregulation, while FGF-2 antagonizes this TGF-beta1-induced Myf5 nuclear translocation and phenotype switch.","method":"RT-PCR; immunoprecipitation; EMSA; indirect immunofluorescence for nuclear translocation in primary pericytes","journal":"Investigative ophthalmology & visual science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP/immunofluorescence, single lab, mechanism not fully established","pmids":["14578427"],"is_preprint":false},{"year":1993,"finding":"9-cis-retinoic acid (acting via retinoid X receptors) represses Myf5 mRNA levels in C2 and L6 myoblast cell lines, likely at the transcriptional level, because Myf5 mRNA stability is unaffected; cycloheximide does not block the repression, suggesting direct involvement of RA receptors.","method":"Northern blot; mRNA stability assay; cycloheximide treatment; retinoid receptor-selective agonists in cell culture","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — mRNA stability and transcriptional analysis with receptor-selective compounds, single lab","pmids":["8404668"],"is_preprint":false},{"year":2008,"finding":"The Mrf4/Myf5 locus is regulated by a novel mechanism involving equilibria among enhancers, promoters, and transcription balancing sequences (which can act as cryptic promoters). These elements collectively ensure that enhancers and promoters produce the highly dynamic expression patterns of both genes; nonproductive interactions between enhancers and cryptic promoters explain the unexpected phenotypes of different Mrf4 knockout alleles.","method":"Enhancer-promoter composition manipulation in transgenic mice; BAC/YAC reporter series; in vivo expression analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic in vivo enhancer-promoter dissection in transgenic mice, novel regulatory mechanism defined","pmids":["18198342"],"is_preprint":false}],"current_model":"MYF5 is a basic helix-loop-helix (bHLH) transcription factor and the earliest myogenic regulatory factor expressed in skeletal muscle progenitors; it heterodimerizes with E-proteins (E12/E47) to bind E-box sequences and activate muscle genes through two cooperative N- and C-terminal transactivation domains, acts genetically upstream of MyoD as one of two parallel determination pathways (alongside Pax3) for skeletal myogenesis, is directly regulated at its multiple dispersed enhancers by the Shh/Gli, Wnt/β-catenin, Pax3/Dmrt2, Six1/4, Zic1/2, and MLL1-H3K4me3 pathways, undergoes cell cycle-dependent phosphorylation and mitotic proteasomal degradation, is post-transcriptionally suppressed in quiescent satellite cells by miR-31-mediated sequestration in mRNP granules, and—unlike MyoD—induces histone acetylation at muscle gene loci without recruiting RNA Pol II or robustly activating transcription, thereby marking the initial chromatin-priming step of muscle lineage specification prior to full transcriptional activation by MyoD; MYF5 also functions as an RNA-binding protein that enhances CCND1 mRNA translation to support myoblast proliferation."},"narrative":{"mechanistic_narrative":"MYF5 is a basic helix-loop-helix transcription factor that acts as one of the earliest determinants of skeletal muscle lineage, heterodimerizing with the ubiquitous E-protein E12 to achieve high-affinity, sequence-specific E-box binding and muscle-specific transactivation through two cooperative N- and C-terminal activation domains that function together with the DNA-binding region [PMID:2385294, PMID:1582413]. Gain-of-function expression of MYF5 is sufficient to establish the myoblast phenotype in mesenchymal cells and to drive ectopic skeletal myogenesis in vivo [PMID:8413206, PMID:8187980]. Genetically, MYF5 defines a determination pathway parallel to Pax3 that acts upstream of MyoD, with Pax3 and Myf5 doubly required for body muscle formation and Mrf4 able to substitute as a determination gene in their combined absence [PMID:9094721, PMID:15386014]; the two factors also pattern distinct muscle compartments and lineages, MYF5 being required for epaxial myogenesis [PMID:9428409, PMID:8617206]. Despite binding the same genomic sites as MyoD, MYF5 induces histone acetylation without recruiting RNA Pol II or robustly activating transcription, marking an initial chromatin-priming step in lineage specification that precedes full activation by MyoD [PMID:26906734]. MYF5 transcription is controlled by multiple dispersed, compartment-specific enhancers integrating Shh/Gli, Wnt/β-catenin, Pax3/Dmrt2, Six1/4, and Zic signaling [PMID:10934019, PMID:11782449, PMID:16936075, PMID:17592144, PMID:20368965, PMID:24036067]. Its protein output is gated post-translationally and post-transcriptionally: MYF5 undergoes cell cycle-dependent phosphorylation and mitotic proteasomal degradation [PMID:9425159], and in quiescent satellite cells its mRNA is sequestered in mRNP granules with miR-31 to suppress translation until activation [PMID:22770245]. Beyond its transcriptional role, MYF5 is itself an RNA-binding protein that binds Ccnd1 mRNA and enhances CCND1 translation to support myoblast proliferation [PMID:26819411]. MYF5 marks committed quiescent satellite cells and is required, redundantly with MyoD, for muscle regeneration [PMID:11121437, PMID:29478898].","teleology":[{"year":1990,"claim":"Established the biochemical basis of MYF5 function by showing it carries an intrinsic activation domain separable from its HLH motif and requires heterodimerization with E12 for high-affinity DNA binding and muscle-specific transactivation.","evidence":"GAL4-fusion transactivation assays and heterodimerization with E12","pmids":["2385294"],"confidence":"High","gaps":["Did not map the full set of in vivo target genes","E-protein partner choice in vivo not addressed"]},{"year":1992,"claim":"Resolved the structure-function logic of MYF5, defining the basic region and HLH helices for DNA binding/dimerization and two cooperative terminal activation domains both required for activity.","evidence":"Site-directed mutagenesis and chimeric GAL4-Myf5 reporter assays","pmids":["1582413"],"confidence":"High","gaps":["Coactivator partners of the activation domains not identified","No structural model of the activation domains"]},{"year":1993,"claim":"Showed MYF5 transcriptional output is modulated post-translationally, as PKA phosphorylation and cAMP repress bHLH-driven muscle gene activation without altering DNA binding, identifying a signaling brake on differentiation.","evidence":"In vitro PKA kinase assay plus reporter co-transfection with PKA manipulation","pmids":["8387507"],"confidence":"High","gaps":["PKA phosphorylation sites on MYF5 not mapped","Mechanism of post-DNA-binding inhibition unresolved"]},{"year":1993,"claim":"Demonstrated MYF5 can transactivate a specific muscle structural gene (desmin) through E-box elements, linking the factor to direct downstream target regulation.","evidence":"Co-transfection desmin-CAT reporter and EMSA in 10T1/2 cells","pmids":["8382796"],"confidence":"Medium","gaps":["Single target gene tested for MYF5 specifically","In vivo relevance not established"]},{"year":1993,"claim":"Established that MYF5 alone establishes the myoblast phenotype without cross-activating other MRFs or autoactivating, indicating it acts as a committed determinant rather than through an MRF amplification loop in this context.","evidence":"Stable transfection of C3H10T1/2 cells with MRF cDNAs and RT-PCR","pmids":["8187980"],"confidence":"Medium","gaps":["Single cell system","May not reflect cross-regulation in embryonic context"]},{"year":1993,"claim":"Identified retinoid signaling as a transcriptional repressor of Myf5, showing 9-cis-RA via RXR lowers Myf5 mRNA without affecting stability.","evidence":"Northern blot, mRNA stability and cycloheximide assays with receptor-selective retinoids in myoblast lines","pmids":["8404668"],"confidence":"Medium","gaps":["Direct RA-responsive element not mapped","Single-lab cell-line data"]},{"year":1993,"claim":"Provided in vivo proof of MYF5's myogenic determination capacity by showing ectopic expression converts brain and heart to skeletal muscle and activates endogenous determination genes.","evidence":"Transgenic mouse overexpression with histology and in situ hybridization","pmids":["8413206"],"confidence":"High","gaps":["Mechanism of cross-lineage conversion not detailed","Direct vs indirect target activation not separated"]},{"year":1996,"claim":"Defined MYF5 and MyoD as marking distinct, independently committed muscle lineages rather than sequential states of one cell.","evidence":"Selective cell ablation in differentiating ES cells with lineage analysis","pmids":["8617206"],"confidence":"High","gaps":["Molecular basis of lineage divergence unknown","ES-cell model may not capture all embryonic lineages"]},{"year":1996,"claim":"Showed functional redundancy between Myf5 and myogenin for rib formation by rescuing Myf5-null defects with myogenin knocked into the Myf5 locus.","evidence":"Homologous recombination knock-in and phenotypic rescue in mice","pmids":["8587605"],"confidence":"High","gaps":["Does not address muscle-specific roles distinguishing the factors","Locus context vs protein function not fully separated"]},{"year":1997,"claim":"Established the epistatic hierarchy by showing MyoD activation requires either Pax3 or Myf5, defining two parallel upstream determination pathways with MyoD downstream.","evidence":"Pax3/Myf5 double-mutant mouse epistasis with lacZ lineage tracing","pmids":["9094721","9094722"],"confidence":"High","gaps":["Molecular link from Pax3 to Myf5 not yet defined here","Compartment-specific contributions not detailed"]},{"year":1997,"claim":"Showed Myf5 and MyoD govern distinct muscle compartments, with Myf5 specifically required for epaxial and MyoD for hypaxial/limb myogenesis.","evidence":"Knockout mouse analysis with multiple muscle markers","pmids":["9428409"],"confidence":"High","gaps":["Mechanistic basis of compartment specificity unresolved","Does not address regeneration roles"]},{"year":1998,"claim":"Discovered cell cycle coupling of MYF5 protein levels, identifying it as the first transcription factor subject to phosphorylation-dependent mitotic proteolysis.","evidence":"Immunoblotting of synchronized cultures with nocodazole block and immunolocalization","pmids":["9425159","9744876"],"confidence":"High","gaps":["Responsible kinase and E3 ligase not identified","Phosphodegron not mapped"]},{"year":1998,"claim":"Demonstrated differential upstream signaling by showing distinct Wnt ligands, and RhoA/SRF, selectively regulate Myf5 versus MyoD.","evidence":"Paraxial mesoderm explants with Wnt-expressing cells, genetic reporters, and RhoA/SRF perturbation","pmids":["9753670","9658178"],"confidence":"High","gaps":["Direct Myf5 cis-elements for these pathways not yet defined here","Receptor specificity not fully resolved"]},{"year":1999,"claim":"Identified Myf5 as the direct epaxial target of Shh, placing hedgehog signaling at the top of epaxial muscle induction.","evidence":"Shh-null mice and presomitic mesoderm explants with recombinant Shh, including Myf5-null crosses","pmids":["10457014"],"confidence":"High","gaps":["Direct cis-element not yet mapped at this stage","Region-specific dependence not generalized"]},{"year":2000,"claim":"Revealed modular long-range control of Myf5 through multiple dispersed compartment-specific enhancers across the MRF4/Myf5 locus.","evidence":"Transgenic lacZ reporter analysis with systematic upstream deletions","pmids":["10934019"],"confidence":"High","gaps":["Trans-acting factors for each enhancer not all identified at this stage","Enhancer-promoter interaction logic not yet resolved"]},{"year":2000,"claim":"Established MYF5 as a marker of committed, quiescent CD34+ satellite cells, linking the factor to the adult muscle stem cell compartment.","evidence":"Isolated myofibers, Myf5-nlacZ reporter mice, immunofluorescence and flow cytometry","pmids":["11121437"],"confidence":"High","gaps":["Functional role of MYF5 in quiescence not addressed here","Does not explain how protein is restrained in quiescence"]},{"year":2000,"claim":"Showed Myf5 is regulated post-transcriptionally in neurons, where mRNA is correctly spliced but protein is absent, explaining the absence of myogenic conversion in brain.","evidence":"Protein and mRNA detection in brain neurons with Myf5-nlacZ reporter and retrograde labeling","pmids":["8575308","10603349"],"confidence":"High","gaps":["Molecular machinery blocking translation/stability in neurons not identified","Whether this overlaps the satellite cell mechanism unknown"]},{"year":2001,"claim":"Positioned Notch signaling as acting between the Myf5 and MyoD steps, blocking progression of Myf5+ myoblasts to the MyoD stage without altering Myf5 expression.","evidence":"Retroviral Delta1 misexpression in chick limb with in situ hybridization","pmids":["11060246"],"confidence":"High","gaps":["Direct molecular targets of Notch at this transition not defined","Mammalian validation not in this study"]},{"year":2002,"claim":"Mapped a direct Gli-binding site in the Myf5 epaxial enhancer required for Shh-dependent activation, converting the Shh dependence into a defined cis-regulatory mechanism.","evidence":"Transgenic and luciferase reporters with Gli-site mutagenesis in Shh-null embryos","pmids":["11782449"],"confidence":"High","gaps":["Cooperating factors at the enhancer not all defined here","Other enhancers' direct inputs not addressed"]},{"year":2003,"claim":"Placed p300 HAT activity upstream of Myf5 induction, showing histone acetylation is specifically required for activating the determination gene.","evidence":"Allelic series of p300/CBP knockout and HAT-dead mice and ES cells with RT-PCR and immunostaining","pmids":["14517256"],"confidence":"High","gaps":["Direct recruitment of p300 to the Myf5 locus not demonstrated","CBP/p300 nonredundancy mechanism unresolved"]},{"year":2003,"claim":"Linked Myf5 nuclear translocation to TGF-β/Smad-driven contractile phenotype switching in pericytes, antagonized by FGF-2, suggesting a context outside classical myogenesis.","evidence":"RT-PCR, immunoprecipitation, EMSA and immunofluorescence in primary retinal pericytes","pmids":["14578427"],"confidence":"Low","gaps":["Single-lab Co-IP/immunofluorescence without orthogonal validation","Direct role of MYF5 in the phenotype switch not established","Physiological significance unclear"]},{"year":2004,"claim":"Revised the determination hierarchy by showing Mrf4 can confer muscle identity when both Myf5 and MyoD are absent, placing Mrf4 alongside Myf5 upstream of MyoD.","evidence":"Allelic series of Myf5 mutants and Myf5:MyoD double-null mice with histology","pmids":["15386014"],"confidence":"High","gaps":["Relative contribution of each determination gene by lineage unresolved","Adult relevance addressed separately"]},{"year":2006,"claim":"Defined direct Wnt/β-catenin control of Myf5 through Tcf/Lef sites at the epaxial enhancer and showed synergy with the Shh/Gli pathway.","evidence":"In vivo Tcf/Lef site mutagenesis, β-catenin gain/loss-of-function, Frizzled knockdown and reporters","pmids":["16936075"],"confidence":"High","gaps":["Integration with other enhancer inputs not fully mapped","Quantitative contribution vs Shh not resolved"]},{"year":2007,"claim":"Identified Six1/Six4 as direct regulators of Myf5 in limb myogenesis through binding a distal limb enhancer.","evidence":"EMSA, in vivo ChIP, enhancer mutagenesis and Six1/Six4 mutant mouse analysis","pmids":["17592144"],"confidence":"High","gaps":["Cooperating limb factors not all defined","Relationship to Pax3 input at limb not resolved"]},{"year":2007,"claim":"Defined a role for Myf5 in adult muscle regeneration, with Myf5-null muscle showing impaired regeneration, fibrosis, adipocyte accumulation and impaired myoblast proliferation.","evidence":"Myf5-null freeze-injury model with histology and in vitro proliferation assays","pmids":["17961534"],"confidence":"High","gaps":["Distinct from MyoD-redundant requirement not yet separated here","Molecular mediators of the proliferation defect unidentified at this stage"]},{"year":2008,"claim":"Demonstrated by lineage tracing and ablation that a Myf5-independent MyoD lineage can sustain myogenesis, refining the two-lineage model and showing Myf5-lineage contribution to ribs.","evidence":"Myf5-Cre conditional ablation and Cre-dependent lineage tracing","pmids":["18331721"],"confidence":"High","gaps":["Molecular determinants of the alternative lineage unknown","Functional equivalence of the two lineages unresolved"]},{"year":2008,"claim":"Defined a complex enhancer-promoter equilibrium mechanism with transcription balancing/cryptic promoter sequences governing the dynamic Mrf4/Myf5 expression patterns.","evidence":"Transgenic BAC/YAC reporter series with enhancer-promoter composition manipulation","pmids":["18198342"],"confidence":"High","gaps":["Chromatin architecture mediating these equilibria not resolved","Trans factors enforcing balancing not identified"]},{"year":2009,"claim":"Linked DUX4c to MYF5 protein stabilization and a proliferative, differentiation-inhibited myoblast state via physical interaction.","evidence":"Western blot, DNA-binding assay and single co-immunoprecipitation with overexpression in human myoblasts","pmids":["19829708"],"confidence":"Medium","gaps":["Single Co-IP without reciprocal validation","Mechanism of stabilization not defined"]},{"year":2010,"claim":"Defined a Pax3→Dmrt2→Myf5 cascade in which Dmrt2 directly binds and transactivates the Myf5 epaxial enhancer, providing a molecular link from Pax3 to Myf5.","evidence":"EMSA, ChIP, transgenic enhancer analysis and conditional overexpression in mice","pmids":["20368965"],"confidence":"High","gaps":["How this cascade integrates with Shh/Wnt inputs not fully resolved","Temporal ordering relative to other enhancer factors unclear"]},{"year":2011,"claim":"Showed Zic1/Zic2 potentiate Gli-dependent Myf5 activation, with Zic2 forming complexes with Gli2, integrating multiple dermomyotome inputs at the epaxial enhancer.","evidence":"In situ hybridization, reporter assays, co-immunoprecipitation and Zic2 mutant mouse analysis","pmids":["21211521"],"confidence":"High","gaps":["Stoichiometry/architecture of the Zic-Gli complex unknown","Quantitative enhancer contribution not resolved"]},{"year":2012,"claim":"Established a translational control mechanism in quiescent satellite cells, where Myf5 mRNA is sequestered in mRNP granules with miR-31 and released upon activation, explaining MYF5 protein restraint despite mRNA presence.","evidence":"RNA immunoprecipitation, FISH, miR-31 manipulation, in vitro translation and in vivo regeneration","pmids":["22770245"],"confidence":"High","gaps":["Full granule composition and assembly factors not defined","Whether neuronal silencing uses the same machinery unknown"]},{"year":2012,"claim":"Defined the Myf5 lineage as a precursor source for adipocytes, showing PTEN/PI3K signaling controls Myf5+ adipocyte expansion and that Myf5+ precursors yield brown and some white adipocytes.","evidence":"Myf5-Cre conditional Pten knockout with lineage tracing and fat depot analysis","pmids":["22940198"],"confidence":"High","gaps":["Role of MYF5 protein itself (vs lineage marking) in adipogenesis not addressed","Mechanism of lineage bifurcation unknown"]},{"year":2013,"claim":"Connected Myf5 locus repression to nuclear lamina positioning, with emerin and HDAC3 required for lamina tethering before activation and relocation to nucleoplasm upon differentiation.","evidence":"ChIP, FISH for nuclear position, emerin/HDAC3 knockdown and HDAC3 catalytic activation","pmids":["24062260"],"confidence":"Medium","gaps":["Causality between positioning and expression not fully separated","Single-lab data"]},{"year":2013,"claim":"Showed Pax3 synergizes with Gli2 and Zic1 at the Myf5 epaxial enhancer and a novel promoter homeodomain motif, integrating the determination inputs onto endogenous Myf5.","evidence":"Transactivation reporters with domain mutagenesis and ChIP at endogenous Myf5 in 10T1/2 cells","pmids":["24036067"],"confidence":"High","gaps":["In vivo requirement of the promoter motif not established","Order of factor assembly unresolved"]},{"year":2016,"claim":"Distinguished MYF5 from MyoD mechanistically by genome-wide ChIP-seq, showing MYF5 induces histone acetylation without Pol II recruitment or robust transcription, defining a chromatin-priming role preceding MyoD activation.","evidence":"ChIP-seq for MYF5, MyoD, histone marks and Pol II in myoblasts","pmids":["26906734"],"confidence":"High","gaps":["Coactivators mediating MYF5 acetylation without activation not identified","How priming is later read by MyoD unresolved"]},{"year":2016,"claim":"Uncovered a non-transcriptional function of MYF5 as an RNA-binding protein that binds Ccnd1 mRNA and promotes CCND1 translation to support myoblast proliferation.","evidence":"RIP, biotin-RNA pulldown, UV crosslinking, EMSA and CCND1 rescue experiments","pmids":["26819411"],"confidence":"High","gaps":["RNA-binding domain/motif on MYF5 not mapped","Full mRNA target set incompletely defined"]},{"year":2018,"claim":"Established an absolute, redundant requirement for MyoD or Myf5 in muscle regeneration, with double-knockout satellite cells maintained but unable to differentiate after injury.","evidence":"Conditional MyoD/Myf5 double knockout in satellite cells with injury model and lineage tracing","pmids":["29478898"],"confidence":"High","gaps":["Molecular events that stabilize myogenic identity not detailed","Individual contributions during regeneration not separated"]},{"year":2018,"claim":"Identified SNAIL as a repressor of MYF5 in rhabdomyosarcoma, acting through an HDAC1/2 complex, linking MYF5 silencing to a tumor differentiation block.","evidence":"ChIP at MYF5 promoter, SNAIL knockdown, Co-IP of SNAIL-HDAC1/2 and xenograft model","pmids":["29844345"],"confidence":"Medium","gaps":["Single-lab characterization","Direct vs indirect repression in normal myogenesis not established"]},{"year":2019,"claim":"Implicated MLL1-mediated H3K4me3 in Myf5 promoter activation, linking this epigenetic mark to satellite cell proliferation and muscle repair.","evidence":"ChIP for H3K4me3, MLL1 knockdown, cell cycle analysis and cardiotoxin injury model","pmids":["31840352"],"confidence":"Medium","gaps":["Direct MLL1 recruitment mechanism to Myf5 not defined","Single-lab data"]},{"year":null,"claim":"How MYF5 acetylates muscle gene chromatin without activating transcription, and how this priming is subsequently decoded by MyoD to confer robust activation, remains unresolved.","evidence":"No direct experimental resolution in the available corpus","pmids":[],"confidence":"High","gaps":["Coactivators/HATs recruited by MYF5 unidentified","Molecular handoff from MYF5 priming to MyoD activation undefined","MYF5 phosphodegron, responsible kinase and E3 ligase unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,3,4,34]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[35]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[14,32,40]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[31]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,9,16,17,24]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1,34]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[16,24,20]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[31,35]}],"complexes":[],"partners":["E12","GLI2","ZIC2","DUX4C","SNAIL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P13349","full_name":"Myogenic factor 5","aliases":["Class C basic helix-loop-helix protein 2","bHLHc2"],"length_aa":255,"mass_kda":28.3,"function":"Transcriptional activator that promotes transcription of muscle-specific target genes and plays a role in muscle differentiation (PubMed:29887215). Together with MYOG and MYOD1, co-occupies muscle-specific gene promoter core region during myogenesis. Induces fibroblasts to differentiate into myoblasts. Probable sequence specific DNA-binding protein","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P13349/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MYF5","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MYF5","total_profiled":1310},"omim":[{"mim_id":"619566","title":"MUSCULAR DYSTROPHY, LIMB-GIRDLE, AUTOSOMAL RECESSIVE 27; LGMDR27","url":"https://www.omim.org/entry/619566"},{"mim_id":"618578","title":"CONGENITAL MYOPATHY 19; CMYO19","url":"https://www.omim.org/entry/618578"},{"mim_id":"618155","title":"OPHTHALMOPLEGIA, EXTERNAL, WITH RIB AND VERTEBRAL ANOMALIES; EORVA","url":"https://www.omim.org/entry/618155"},{"mim_id":"615671","title":"SET DOMAIN-CONTAINING PROTEIN 3; SETD3","url":"https://www.omim.org/entry/615671"},{"mim_id":"615581","title":"DOUBLE HOMEOBOX 4-LIKE 9; DUX4L9","url":"https://www.omim.org/entry/615581"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"skeletal muscle","ntpm":5.2},{"tissue":"tongue","ntpm":8.3}],"url":"https://www.proteinatlas.org/search/MYF5"},"hgnc":{"alias_symbol":["bHLHc2"],"prev_symbol":[]},"alphafold":{"accession":"P13349","domains":[{"cath_id":"4.10.280.10","chopping":"97-146","consensus_level":"medium","plddt":93.9214,"start":97,"end":146}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P13349","model_url":"https://alphafold.ebi.ac.uk/files/AF-P13349-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P13349-F1-predicted_aligned_error_v6.png","plddt_mean":63.91},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MYF5","jax_strain_url":"https://www.jax.org/strain/search?query=MYF5"},"sequence":{"accession":"P13349","fasta_url":"https://rest.uniprot.org/uniprotkb/P13349.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P13349/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P13349"}},"corpus_meta":[{"pmid":"11121437","id":"PMC_11121437","title":"Expression of CD34 and Myf5 defines the majority of quiescent adult skeletal muscle satellite cells.","date":"2000","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/11121437","citation_count":680,"is_preprint":false},{"pmid":"9094721","id":"PMC_9094721","title":"Redefining the genetic hierarchies controlling skeletal myogenesis: Pax-3 and Myf-5 act upstream of MyoD.","date":"1997","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9094721","citation_count":671,"is_preprint":false},{"pmid":"29127046","id":"PMC_29127046","title":"Function of the myogenic regulatory factors Myf5, MyoD, Myogenin and MRF4 in skeletal muscle, satellite cells and regenerative myogenesis.","date":"2017","source":"Seminars in cell & developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/29127046","citation_count":624,"is_preprint":false},{"pmid":"15386014","id":"PMC_15386014","title":"Mrf4 determines skeletal muscle identity in Myf5:Myod double-mutant 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High-affinity, sequence-specific DNA binding requires hetero-oligomeric association with the ubiquitous HLH protein E12 to confer muscle-specific transactivation.\",\n      \"method\": \"GAL4-fusion transactivation assay with reporter plasmid; heterodimerization with E12\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro transactivation assay with domain mapping and heterodimerization experiments, foundational biochemical characterization\",\n      \"pmids\": [\"2385294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Site-directed mutagenesis of MYF5 revealed that two clusters of basic amino acids in the conserved basic region and two amphipathic helices in the HLH domain are essential for sequence-specific DNA binding and hetero-oligomerization, respectively. Transcriptional activation requires two additional cooperative domains in the amino- and carboxyl-termini; deletion of either abolishes activity. Dimerization with E12 increases both DNA-binding affinity and transactivation independently of DNA binding. Muscle-specific transactivation requires collaboration of the two activation domains together with the DNA-binding region.\",\n      \"method\": \"Site-directed mutagenesis; chimeric GAL4-Myf5 fusion reporter assays; co-transfection transactivation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutagenesis and multiple orthogonal reporter assays in a single rigorous study\",\n      \"pmids\": [\"1582413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"PKA phosphorylates MYF5 and MyoD in vitro but does not affect their DNA-binding ability. Nevertheless, elevated cAMP/PKA represses the transcriptional activation of muscle-specific genes by MYF5 and MyoD through the basic HLH domain and E-box motif, acting post-translationally at a step after DNA binding, specifically inhibiting myogenic bHLH proteins but not ubiquitous HLH proteins E12/E47.\",\n      \"method\": \"In vitro PKA phosphorylation assay; reporter co-transfection; dominant-negative and overexpression of PKA catalytic subunit\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus functional reporter experiments with multiple lines of evidence in one study\",\n      \"pmids\": [\"8387507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"All four MRFs including MYF5 can transactivate the mouse desmin gene through E-box elements in its promoter and enhancer, as demonstrated by co-transfection of each factor with desmin-CAT constructs into 10T1/2 cells.\",\n      \"method\": \"Co-transfection reporter assay (desmin-CAT); gel electrophoretic mobility shift assay (EMSA)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro transactivation assay, single lab, single method for MYF5 specifically\",\n      \"pmids\": [\"8382796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Ectopic expression of bovine MYF5 (bmyf) in transgenic mice under a viral promoter caused ectopic skeletal muscle differentiation in brain and heart, activating endogenous skeletal myogenic determination genes, demonstrating that MYF5 can initiate myogenic differentiation in vivo.\",\n      \"method\": \"Transgenic mouse overexpression; histology; in situ hybridization; immunohistochemistry\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain-of-function with multiple tissue readouts, direct demonstration of ectopic myogenesis\",\n      \"pmids\": [\"8413206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"MYF5 alone (without MyoD, myogenin, or MRF4) is sufficient to establish and maintain the myoblast phenotype in C3H10T1/2 mesenchymal cells, but cross-activation of other endogenous MRF genes does not occur at the myoblast stage in these cells; autoactivation of the Myf5 gene also does not occur.\",\n      \"method\": \"Stable transfection of C3H10T1/2 cells with MRF cDNAs; RT-PCR; phenotypic characterization\",\n      \"journal\": \"Differentiation; research in biological diversity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean loss/gain-of-function cell system, single lab\",\n      \"pmids\": [\"8187980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"MYF5 expression is restricted to a subset of subdomains in the embryonic brain (mesencephalon and secondary prosencephalon), where it functions as an axonal marker but does not cause myogenic conversion, as Myf5 protein is absent in neurons despite correct mRNA splicing, indicating post-transcriptional regulation of Myf5 specifically in neurons.\",\n      \"method\": \"Gene-targeted nlacZ knock-in mouse; beta-galactosidase reporter expression; immunofluorescence; immunoblotting; RT-PCR\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knock-in reporter mouse combined with protein detection and RT-PCR demonstrating translational/stability regulation in neurons\",\n      \"pmids\": [\"8575308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Genetic epistasis experiments using Pax-3 (splotch) and Myf-5 double homozygous mutant mice showed complete absence of body muscles not seen in individual mutants, because MyoD activation depends on either Pax-3 or Myf-5. Therefore Pax-3 and Myf-5 define two distinct upstream myogenic pathways and MyoD acts genetically downstream of both in the body.\",\n      \"method\": \"Genetic epistasis using double homozygous mutant mice (Pax3/Myf5); lacZ reporter for lineage tracing; histology\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — double-mutant epistasis independently establishing pathway hierarchy, replicated across multiple groups\",\n      \"pmids\": [\"9094721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Ectopic Pax-3 retroviral infection in embryonic tissues is sufficient to induce expression of MyoD, Myf-5, and myogenin in paraxial and lateral plate mesoderm and the neural tube in the absence of inducing tissues, placing Pax-3 upstream of both MYF5 and MyoD.\",\n      \"method\": \"Retroviral infection of chick embryo explants; in situ hybridization\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function retroviral experiment in chick embryos with direct molecular readout\",\n      \"pmids\": [\"9094722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Myf-5 and MyoD define development of distinct muscle compartments: Myf5(-/-) embryos showed delayed epaxial (paraspinal/intercostal) but normal limb muscle development, while MyoD(-/-) embryos showed delayed limb but normal epaxial muscle development, indicating that Myf-5 is specifically required for epaxial and MyoD for hypaxial myogenesis.\",\n      \"method\": \"Knockout mouse analysis; immunohistochemistry; in situ hybridization for multiple muscle markers\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple knockout mouse lines, multiple orthogonal markers, independently replicated across labs\",\n      \"pmids\": [\"9428409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Myf-5 and MyoD are not expressed in the same muscle precursor cell but rather determine different muscle cell lineages arising from independently committed stem cell populations. Selective ablation of Myf5-expressing precursors from differentiating ES cells does not prevent MyoD-dependent muscle differentiation, and early Myf5-progenitors do not develop into later MyoD cells even when Myf5 is inactivated.\",\n      \"method\": \"Selective cell ablation in differentiating ES cells; lineage analysis; immunofluorescence\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell ablation experiments with lineage analysis, multiple approaches\",\n      \"pmids\": [\"8617206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Targeted knock-in of myogenin cDNA into the Myf5 locus (replacing Myf5 function) rescued rib cage defects and viability in Myf5-null mice, demonstrating functional redundancy of Myf5 and myogenin for rib formation.\",\n      \"method\": \"Homologous recombination knock-in mouse; phenotypic rescue analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — precise genetic rescue experiment demonstrating functional equivalence at the same locus\",\n      \"pmids\": [\"8587605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Wnt1 (from dorsal neural tube) preferentially activates Myf5, while Wnt7a (from dorsal ectoderm) preferentially activates MyoD in paraxial mesoderm explants, demonstrating that different Wnt molecules activate myogenesis through distinct pathways acting on MYF5 and MyoD differentially.\",\n      \"method\": \"Paraxial mesoderm explant culture with Wnt-expressing cells; lacZ reporter for Myf5 (Myf5-nlacZ mice); in situ hybridization\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — explant culture system with specific ligands and genetic reporters, multiple Wnt molecules tested\",\n      \"pmids\": [\"9753670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"RhoA GTPase and serum response factor (SRF) selectively control MyoD expression without affecting Myf5 expression in mouse myoblasts. Blocking RhoA activity or inactivating SRF extinguishes MyoD but not Myf5, demonstrating that MyoD and Myf5 are regulated by different upstream signaling cascades.\",\n      \"method\": \"Dominant-negative RhoA; C3-transferase; lovastatin treatment; SRF inactivation; immunoblot; promoter-reporter assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological and genetic tools with reporter and protein readouts in a single study\",\n      \"pmids\": [\"9658178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MYF5 protein undergoes cell cycle-regulated expression in proliferating myoblasts: it is high in G0, decreases during G1, reappears at end of G1 and is stable until mitosis. Myf5 is proteolytically degraded in a phosphorylation-dependent manner specifically in mitotic cells (G2/M), representing the first transcription factor shown to undergo cell cycle-regulated degradation.\",\n      \"method\": \"Immunoblotting of synchronized cultures; nocodazole mitotic block; immunocytolocalization; cell cycle analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical demonstration of cell cycle-phase-specific protein phosphorylation and proteolysis, multiple synchronization methods\",\n      \"pmids\": [\"9425159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"In proliferating C2 myoblasts, MyoD and Myf-5 expression patterns are mutually exclusive during differentiation. Cell cycle analysis showed MYF5 protein is high in G0 and S/G2/M but falls in G1, while MyoD peaks in mid-G1. High Myf5 (low MyoD) correlates with failure to differentiate, and high MyoD (low Myf5) correlates with entry into differentiation.\",\n      \"method\": \"Immunofluorescence; cell synchronization; immunoblot; isolation of undifferentiated subpopulations\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — synchronized cultures with multiple protein-level readouts and functional differentiation correlation\",\n      \"pmids\": [\"9744876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Sonic hedgehog (Shh) has an essential inductive function for early activation of Myf5 (and MyoD) specifically in epaxial somite cells in the mouse embryo. Myf5, not MyoD, is the direct target of Shh signaling in the epaxial dermomyotome, as shown by failure of MyoD activation by recombinant Shh in presomitic mesoderm explants from Myf5-null embryos.\",\n      \"method\": \"Shh-null mouse analysis; presomitic mesoderm explants with recombinant Shh protein; Myf5-null mouse cross; in situ hybridization\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null mutant combined with explant rescue experiments, independently replicated across labs\",\n      \"pmids\": [\"10457014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The Myf5 gene is controlled by multiple discrete and dispersed enhancers spread throughout 14 kb spanning the MRF4/Myf5 locus, each driving reporter expression in a particular subset of skeletal muscle precursors. Separate enhancers control epaxial body, some hypaxial body, facial muscle, and CNS expression, demonstrating modular long-range transcriptional control.\",\n      \"method\": \"Transgenic mouse reporter analysis; lacZ transgene constructs with various upstream deletions\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple independent transgenic lines with systematic deletion mapping, replicated across labs\",\n      \"pmids\": [\"10934019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Quiescent satellite cells express both CD34 and MYF5 (via beta-galactosidase activity in Myf5-nlacZ mice), and all CD34-positive satellite cells co-express MYF5, establishing MYF5 as a marker of committed, quiescent muscle satellite cells.\",\n      \"method\": \"Isolated myofiber preparation; immunofluorescence; Myf5-nlacZ knock-in reporter mice; flow cytometry\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic reporter plus immunofluorescence on primary tissue, multiple markers co-analyzed\",\n      \"pmids\": [\"11121437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MYF5 protein is absent in neurons despite correct splicing of Myf5 mRNA, indicating that post-transcriptional regulation (at the level of mRNA translation or protein stability) prevents Myf5 protein accumulation in neurons, which accounts for the lack of myogenic conversion in the brain.\",\n      \"method\": \"Immunofluorescence; immunoblotting; RT-PCR in brain neurons; Myf5-nlacZ transgenic mice; retrograde DiI labeling\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — protein and mRNA detection in same tissue, genetic reporter, multiple methods\",\n      \"pmids\": [\"10603349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Delta1-activated Notch signaling in chick limb bud inhibits muscle differentiation by preventing Myf5-expressing myoblasts from progressing to the MyoD-expressing stage, without affecting Myf5 or Pax3 expression, placing Notch action between the Myf5 and MyoD steps in the myogenic hierarchy.\",\n      \"method\": \"Retroviral misexpression of Delta1 in chick limb; in situ hybridization for Myf5, Pax3, MyoD; immunohistochemistry\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain-of-function with multiple molecular readouts placing Notch between Myf5 and MyoD steps\",\n      \"pmids\": [\"11060246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Myf5 is a direct target of long-range Shh signaling through positive regulation by Gli transcription factors. A Gli-binding site within the Myf5 epaxial somite (ES) enhancer is required for enhancer activation by Shh signaling in transfected 3T3 cells and in transgenic embryos; deletion of this Gli site abolishes activity in Shh-null embryos.\",\n      \"method\": \"Transgenic lacZ reporter analysis; luciferase reporter in Shh-responsive 3T3 cells; Gli-site mutagenesis; Shh heterozygous and homozygous null embryo analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — enhancer mutagenesis combined with in vivo transgenic validation and null mutant analysis\",\n      \"pmids\": [\"11782449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"p300 acetyltransferase (HAT) activity is specifically required for induction of Myf5 and MyoD expression upstream of these MRFs; embryos lacking p300 protein show severely attenuated Myf5 induction, while ES cells with p300 null or HAT-dead mutations fail to activate Myf5 efficiently despite normal Pax3 expression. CBP HAT activity is not required for Myf5 activation.\",\n      \"method\": \"Genetic mouse knockouts and ES cells with point mutations (p300 AT-dead, p300 null, CBP AT-dead); RT-PCR; immunostaining\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple allelic series of knockouts with molecular readouts, places p300 HAT activity upstream of Myf5\",\n      \"pmids\": [\"14517256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In the absence of both Myf5 and MyoD, Mrf4 expression (when intact) is sufficient to confer skeletal muscle identity, revising the epistatic relationship: both Myf5 and Mrf4 act upstream of MyoD as muscle determination genes.\",\n      \"method\": \"Allelic series of three Myf5 mutants differentially affecting Mrf4 expression; Myf5:MyoD double-null mice; histology; molecular analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — allelic series with genetic epistasis, multiple mutant combinations, replicated\",\n      \"pmids\": [\"15386014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Canonical Wnt/beta-catenin signaling directly activates Myf5 transcription in epaxial somite progenitors via Frizzled receptors (Fz1 and/or Fz6) and Tcf/Lef-binding sites immediately 5' to the Myf5 early epaxial enhancer. Blocking Wnt/beta-catenin dramatically reduces Myf5 activation, while activated beta-catenin is sufficient to activate Myf5 in somites. The Wnt/beta-catenin and Shh/Gli pathways act synergistically.\",\n      \"method\": \"Tcf/Lef site mutation in transgenic mice; gain-of-function and loss-of-function of beta-catenin in somites; Frizzled knockdown; reporter assays\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis of regulatory elements in vivo combined with gain/loss-of-function, multiple orthogonal methods\",\n      \"pmids\": [\"16936075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Six1 and Six4 homeoproteins bind a 145-bp Myf5 limb enhancer element (at -57.5 kb) in vitro (EMSA) and in vivo (ChIP), and Six1 transactivates a reporter under the control of this sequence. Myf5 expression is severely impaired in limb buds of Six1(-/-) and Six1(-/-)/Six4(-/+) mutant mice despite presence of myogenic progenitors, establishing Six1/4 as direct upstream regulators of Myf5 in limb myogenesis.\",\n      \"method\": \"EMSA; ChIP with embryonic extracts; transactivation reporter assay; transgenic enhancer mutagenesis; Six1/Six4 mutant mouse analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding plus in vivo ChIP plus enhancer mutagenesis plus genetic knockout, multiple orthogonal methods\",\n      \"pmids\": [\"17592144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Myf5-null adult mice exhibit perturbed muscle regeneration with increased fiber hypertrophy, delayed differentiation, adipocyte accumulation, and fibrosis after freeze-injury. Mrf4 is not expressed in normal or Myf5-null satellite cells, excluding Mrf4 from a role in adult muscle progenitors. Myf5-null myoblasts show impaired proliferation in vitro.\",\n      \"method\": \"Myf5-null mouse; freeze-injury regeneration model; histology; satellite cell isolation; in vitro proliferation assay\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null mouse with in vivo and in vitro readouts, defines Myf5 role in adult regeneration\",\n      \"pmids\": [\"17961534\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Lineage tracing and conditional cell ablation demonstrated two distinct myogenic lineages in mouse skeletal muscle: a Myf5-lineage and a Myf5-independent lineage. Ablating the Myf5 lineage is compatible with myogenesis sustained by Myf5-independent, MyoD-expressing myoblasts. Myf5-lineage cells also contribute significantly to rib development.\",\n      \"method\": \"Conditional cell ablation using Myf5-Cre; Cre-dependent reporter lineage tracing; genetic mouse crosses\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional cell ablation plus lineage tracing, multiple genetic tools\",\n      \"pmids\": [\"18331721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DUX4c over-expression induces MYF5 protein and its DNA-binding activity in human myoblasts. DUX4c and MYF5 interact by co-immunoprecipitation, suggesting DUX4c stabilizes MYF5 protein. DUX4c-induced MYF5 increase promotes myoblast proliferation and inhibits differentiation.\",\n      \"method\": \"Western blot; DNA-binding assay; co-immunoprecipitation; overexpression in primary human myoblasts\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP for interaction, overexpression with functional readout, single lab\",\n      \"pmids\": [\"19829708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A Pax3/Dmrt2/Myf5 regulatory cascade operates in epaxial dermomyotome stem cells: Pax3 directly binds a conserved sequence at -18 kb from Dmrt2 (shown by gel shift and ChIP), Dmrt2 directly binds and transactivates the Myf5 early epaxial enhancer (shown by gel shift and transactivation assay), and conditional Dmrt2 overexpression in Pax3-expressing somite cells activates Myf5.\",\n      \"method\": \"Gel shift (EMSA); ChIP; transgenic enhancer analysis; Dmrt2 mutant embryo analysis; conditional overexpression\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — EMSA plus in vivo ChIP plus enhancer mutagenesis plus gain/loss-of-function genetics, multiple orthogonal methods\",\n      \"pmids\": [\"20368965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Zic1 and Zic2 co-localize with Myf5 and Pax3 in the dorsal medial dermomyotome and potentiate Gli-dependent activation of the Myf5 epaxial somite enhancer. Zic2 co-immunoprecipitates with Gli2, indicating Zic2 forms complexes with Gli2 to promote Myf5 expression. Myf5 expression in newly forming somites is deficient in Zic2 mutant embryos.\",\n      \"method\": \"In situ hybridization; immunohistochemistry; functional reporter assays in 3T3 cells; co-immunoprecipitation; Zic2 mutant mouse analysis; presomitic mesoderm explants\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional reporter plus in vivo genetic mutant, multiple methods\",\n      \"pmids\": [\"21211521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In quiescent satellite cells, Myf5 mRNA is sequestered in mRNP granules together with microRNA-31 which suppresses its translation. Upon satellite cell activation, mRNP granules dissociate, miR-31 levels decrease, and Myf5 protein accumulates via translation (not transcription). Conditions maintaining mRNP granules delay myogenesis; manipulating miR-31 levels affects satellite cell differentiation and muscle regeneration in vivo.\",\n      \"method\": \"RNA immunoprecipitation; FISH for mRNP granules; miR-31 manipulation (overexpression/knockdown); in vitro translation assay; satellite cell ex vivo culture; in vivo muscle regeneration\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (RIP, FISH, functional miRNA manipulation, in vivo) establishing post-transcriptional mechanism\",\n      \"pmids\": [\"22770245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Emerin associates with the Myf5 genomic locus in proliferating myogenic progenitors (ChIP). Before transcriptional activation, the Myf5 locus localizes to the nuclear lamina; upon activation during differentiation it moves to the nucleoplasm. Both emerin and HDAC3 are required for proper Myf5 localization to the nuclear lamina and its repression; activation of HDAC3 catalytic activity rescues Myf5 lamina localization.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP); fluorescence in situ hybridization (FISH) for nuclear position; emerin and HDAC3 knockdown; HDAC3 catalytic activation\",\n      \"journal\": \"Chromosome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ChIP plus FISH for localization, single lab, functional connection to expression\",\n      \"pmids\": [\"24062260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Pax3 synergizes with Gli2 and Zic1 in transactivating the Myf5 epaxial somite (ES) enhancer. This synergy requires conserved functional domains of each protein, a novel homeodomain motif in the Myf5 promoter, and the essential Gli motif in the ES enhancer. Overexpression of Zic1 and Pax3 in 10T1/2 cells results in their enrichment at the endogenous Myf5 locus (ChIP) and induction of Myf5 expression.\",\n      \"method\": \"Transactivation reporter assay; domain mutagenesis; ChIP at endogenous Myf5 locus; overexpression in 10T1/2 cells\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reporter assay with mutagenesis plus in vivo ChIP at endogenous locus, multiple factor combinations tested\",\n      \"pmids\": [\"24036067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MYF5 and MyoD bind the same genomic sites genome-wide but have distinct molecular functions: Myf5 induces histone acetylation without Pol II recruitment or robust gene activation, whereas MyoD induces histone acetylation, recruits Pol II, and robustly activates gene transcription. Thus initial muscle lineage specification by Myf5 occurs without significant induction of gene transcription.\",\n      \"method\": \"ChIP-seq for MYF5, MyoD, histone marks, Pol II; genome-wide binding comparison in myoblasts\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — genome-wide ChIP-seq with multiple marks, rigorous comparison of two factors at same loci\",\n      \"pmids\": [\"26906734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MYF5 functions as an RNA-binding protein in myoblasts, associating with a subset of mRNAs including Ccnd1 (Cyclin D1) mRNA. MYF5 binds the 3' UTR and coding region of Ccnd1 mRNA (shown by biotin-RNA pulldown, UV-crosslinking, gel shift, and RIP), promotes CCND1 protein translation, and modestly increases Ccnd1 transcription. MYF5-dependent CCND1 upregulation is required for normal myoblast proliferation and differentiation.\",\n      \"method\": \"Ribonucleoprotein immunoprecipitation (RIP); biotin-RNA pulldown; UV crosslinking; gel shift (EMSA); MYF5 knockdown/overexpression; polysome profiling implied; rescue by CCND1 restoration\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal binding assays (RIP, pulldown, UV-crosslink, EMSA) plus functional rescue experiments\",\n      \"pmids\": [\"26819411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Satellite cells lacking both MyoD and Myf5 (double knockout) are maintained in uninjured muscle but fail to regenerate injured muscle; dKO satellite cell progeny accumulate in damaged muscle without undergoing muscle differentiation, demonstrating an absolute requirement for either MyoD or Myf5 in muscle regeneration and showing their expression stabilizes myogenic identity.\",\n      \"method\": \"Conditional double knockout (MyoD/Myf5) in satellite cells; muscle injury model; histology; immunofluorescence; lineage tracing\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional double-KO with injury model, multiple molecular and cellular readouts\",\n      \"pmids\": [\"29478898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SNAIL transcription factor binds to the MYF5 promoter and suppresses its expression. SNAIL silencing in alveolar rhabdomyosarcoma cells allows re-expression of MYF5 and promotes myogenic differentiation. SNAIL forms a repressive complex with HDAC1/2 to regulate MYF5 and other differentiation genes.\",\n      \"method\": \"ChIP for SNAIL at MYF5 promoter; SNAIL knockdown; reporter assays; co-immunoprecipitation of SNAIL-HDAC1/2 complex; xenograft tumor model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ChIP plus Co-IP plus functional knockdown, single lab\",\n      \"pmids\": [\"29844345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MLL1 transcriptionally regulates Myf5 by mediating H3K4me3 on its promoter. ChIP showed H3K4me3 enrichment at the Myf5 promoter is MLL1-dependent; MLL1 knockdown reduced Myf5 expression and caused G1 cell cycle arrest in myoblasts. MLL1 is required for satellite cell proliferation and muscle repair in vivo.\",\n      \"method\": \"ChIP for H3K4me3 at Myf5 promoter; siRNA knockdown of MLL1; cell cycle analysis; cardiotoxin injury model in vivo\",\n      \"journal\": \"Cell proliferation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ChIP plus knockdown functional assay, single lab\",\n      \"pmids\": [\"31840352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PTEN deletion with myf5-Cre selectively expands Myf5-lineage adipocytes, causing lipomatosis and partial lipodystrophy, demonstrating that PI3K/PTEN signaling specifically controls the Myf5+ adipocyte lineage and that Myf5+ mesenchymal precursors give rise not only to brown adipocytes and muscle but also to subsets of white adipocytes.\",\n      \"method\": \"Conditional Pten knockout using Myf5-Cre; lineage tracing; fat depot analysis; histology\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with lineage tracing, defined cellular phenotype, multiple depot analyses\",\n      \"pmids\": [\"22940198\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"TGF-beta1 treatment of retinal pericytes induces nuclear translocation of Myf5 (along with Smad2), switching cells from a growth-potentiated to growth-arrested/contractile phenotype marked by alpha-SMA upregulation, while FGF-2 antagonizes this TGF-beta1-induced Myf5 nuclear translocation and phenotype switch.\",\n      \"method\": \"RT-PCR; immunoprecipitation; EMSA; indirect immunofluorescence for nuclear translocation in primary pericytes\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/immunofluorescence, single lab, mechanism not fully established\",\n      \"pmids\": [\"14578427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"9-cis-retinoic acid (acting via retinoid X receptors) represses Myf5 mRNA levels in C2 and L6 myoblast cell lines, likely at the transcriptional level, because Myf5 mRNA stability is unaffected; cycloheximide does not block the repression, suggesting direct involvement of RA receptors.\",\n      \"method\": \"Northern blot; mRNA stability assay; cycloheximide treatment; retinoid receptor-selective agonists in cell culture\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — mRNA stability and transcriptional analysis with receptor-selective compounds, single lab\",\n      \"pmids\": [\"8404668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The Mrf4/Myf5 locus is regulated by a novel mechanism involving equilibria among enhancers, promoters, and transcription balancing sequences (which can act as cryptic promoters). These elements collectively ensure that enhancers and promoters produce the highly dynamic expression patterns of both genes; nonproductive interactions between enhancers and cryptic promoters explain the unexpected phenotypes of different Mrf4 knockout alleles.\",\n      \"method\": \"Enhancer-promoter composition manipulation in transgenic mice; BAC/YAC reporter series; in vivo expression analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic in vivo enhancer-promoter dissection in transgenic mice, novel regulatory mechanism defined\",\n      \"pmids\": [\"18198342\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MYF5 is a basic helix-loop-helix (bHLH) transcription factor and the earliest myogenic regulatory factor expressed in skeletal muscle progenitors; it heterodimerizes with E-proteins (E12/E47) to bind E-box sequences and activate muscle genes through two cooperative N- and C-terminal transactivation domains, acts genetically upstream of MyoD as one of two parallel determination pathways (alongside Pax3) for skeletal myogenesis, is directly regulated at its multiple dispersed enhancers by the Shh/Gli, Wnt/β-catenin, Pax3/Dmrt2, Six1/4, Zic1/2, and MLL1-H3K4me3 pathways, undergoes cell cycle-dependent phosphorylation and mitotic proteasomal degradation, is post-transcriptionally suppressed in quiescent satellite cells by miR-31-mediated sequestration in mRNP granules, and—unlike MyoD—induces histone acetylation at muscle gene loci without recruiting RNA Pol II or robustly activating transcription, thereby marking the initial chromatin-priming step of muscle lineage specification prior to full transcriptional activation by MyoD; MYF5 also functions as an RNA-binding protein that enhances CCND1 mRNA translation to support myoblast proliferation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MYF5 is a basic helix-loop-helix transcription factor that acts as one of the earliest determinants of skeletal muscle lineage, heterodimerizing with the ubiquitous E-protein E12 to achieve high-affinity, sequence-specific E-box binding and muscle-specific transactivation through two cooperative N- and C-terminal activation domains that function together with the DNA-binding region [#0, #1]. Gain-of-function expression of MYF5 is sufficient to establish the myoblast phenotype in mesenchymal cells and to drive ectopic skeletal myogenesis in vivo [#4, #5]. Genetically, MYF5 defines a determination pathway parallel to Pax3 that acts upstream of MyoD, with Pax3 and Myf5 doubly required for body muscle formation and Mrf4 able to substitute as a determination gene in their combined absence [#7, #23]; the two factors also pattern distinct muscle compartments and lineages, MYF5 being required for epaxial myogenesis [#9, #10]. Despite binding the same genomic sites as MyoD, MYF5 induces histone acetylation without recruiting RNA Pol II or robustly activating transcription, marking an initial chromatin-priming step in lineage specification that precedes full activation by MyoD [#34]. MYF5 transcription is controlled by multiple dispersed, compartment-specific enhancers integrating Shh/Gli, Wnt/\\u03b2-catenin, Pax3/Dmrt2, Six1/4, and Zic signaling [#17, #21, #24, #25, #29, #33]. Its protein output is gated post-translationally and post-transcriptionally: MYF5 undergoes cell cycle-dependent phosphorylation and mitotic proteasomal degradation [#14], and in quiescent satellite cells its mRNA is sequestered in mRNP granules with miR-31 to suppress translation until activation [#31]. Beyond its transcriptional role, MYF5 is itself an RNA-binding protein that binds Ccnd1 mRNA and enhances CCND1 translation to support myoblast proliferation [#35]. MYF5 marks committed quiescent satellite cells and is required, redundantly with MyoD, for muscle regeneration [#18, #36].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established the biochemical basis of MYF5 function by showing it carries an intrinsic activation domain separable from its HLH motif and requires heterodimerization with E12 for high-affinity DNA binding and muscle-specific transactivation.\",\n      \"evidence\": \"GAL4-fusion transactivation assays and heterodimerization with E12\",\n      \"pmids\": [\"2385294\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map the full set of in vivo target genes\", \"E-protein partner choice in vivo not addressed\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Resolved the structure-function logic of MYF5, defining the basic region and HLH helices for DNA binding/dimerization and two cooperative terminal activation domains both required for activity.\",\n      \"evidence\": \"Site-directed mutagenesis and chimeric GAL4-Myf5 reporter assays\",\n      \"pmids\": [\"1582413\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coactivator partners of the activation domains not identified\", \"No structural model of the activation domains\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Showed MYF5 transcriptional output is modulated post-translationally, as PKA phosphorylation and cAMP repress bHLH-driven muscle gene activation without altering DNA binding, identifying a signaling brake on differentiation.\",\n      \"evidence\": \"In vitro PKA kinase assay plus reporter co-transfection with PKA manipulation\",\n      \"pmids\": [\"8387507\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PKA phosphorylation sites on MYF5 not mapped\", \"Mechanism of post-DNA-binding inhibition unresolved\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Demonstrated MYF5 can transactivate a specific muscle structural gene (desmin) through E-box elements, linking the factor to direct downstream target regulation.\",\n      \"evidence\": \"Co-transfection desmin-CAT reporter and EMSA in 10T1/2 cells\",\n      \"pmids\": [\"8382796\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single target gene tested for MYF5 specifically\", \"In vivo relevance not established\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Established that MYF5 alone establishes the myoblast phenotype without cross-activating other MRFs or autoactivating, indicating it acts as a committed determinant rather than through an MRF amplification loop in this context.\",\n      \"evidence\": \"Stable transfection of C3H10T1/2 cells with MRF cDNAs and RT-PCR\",\n      \"pmids\": [\"8187980\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single cell system\", \"May not reflect cross-regulation in embryonic context\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Identified retinoid signaling as a transcriptional repressor of Myf5, showing 9-cis-RA via RXR lowers Myf5 mRNA without affecting stability.\",\n      \"evidence\": \"Northern blot, mRNA stability and cycloheximide assays with receptor-selective retinoids in myoblast lines\",\n      \"pmids\": [\"8404668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct RA-responsive element not mapped\", \"Single-lab cell-line data\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Provided in vivo proof of MYF5's myogenic determination capacity by showing ectopic expression converts brain and heart to skeletal muscle and activates endogenous determination genes.\",\n      \"evidence\": \"Transgenic mouse overexpression with histology and in situ hybridization\",\n      \"pmids\": [\"8413206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of cross-lineage conversion not detailed\", \"Direct vs indirect target activation not separated\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Defined MYF5 and MyoD as marking distinct, independently committed muscle lineages rather than sequential states of one cell.\",\n      \"evidence\": \"Selective cell ablation in differentiating ES cells with lineage analysis\",\n      \"pmids\": [\"8617206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of lineage divergence unknown\", \"ES-cell model may not capture all embryonic lineages\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Showed functional redundancy between Myf5 and myogenin for rib formation by rescuing Myf5-null defects with myogenin knocked into the Myf5 locus.\",\n      \"evidence\": \"Homologous recombination knock-in and phenotypic rescue in mice\",\n      \"pmids\": [\"8587605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address muscle-specific roles distinguishing the factors\", \"Locus context vs protein function not fully separated\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Established the epistatic hierarchy by showing MyoD activation requires either Pax3 or Myf5, defining two parallel upstream determination pathways with MyoD downstream.\",\n      \"evidence\": \"Pax3/Myf5 double-mutant mouse epistasis with lacZ lineage tracing\",\n      \"pmids\": [\"9094721\", \"9094722\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from Pax3 to Myf5 not yet defined here\", \"Compartment-specific contributions not detailed\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed Myf5 and MyoD govern distinct muscle compartments, with Myf5 specifically required for epaxial and MyoD for hypaxial/limb myogenesis.\",\n      \"evidence\": \"Knockout mouse analysis with multiple muscle markers\",\n      \"pmids\": [\"9428409\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic basis of compartment specificity unresolved\", \"Does not address regeneration roles\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Discovered cell cycle coupling of MYF5 protein levels, identifying it as the first transcription factor subject to phosphorylation-dependent mitotic proteolysis.\",\n      \"evidence\": \"Immunoblotting of synchronized cultures with nocodazole block and immunolocalization\",\n      \"pmids\": [\"9425159\", \"9744876\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Responsible kinase and E3 ligase not identified\", \"Phosphodegron not mapped\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated differential upstream signaling by showing distinct Wnt ligands, and RhoA/SRF, selectively regulate Myf5 versus MyoD.\",\n      \"evidence\": \"Paraxial mesoderm explants with Wnt-expressing cells, genetic reporters, and RhoA/SRF perturbation\",\n      \"pmids\": [\"9753670\", \"9658178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct Myf5 cis-elements for these pathways not yet defined here\", \"Receptor specificity not fully resolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified Myf5 as the direct epaxial target of Shh, placing hedgehog signaling at the top of epaxial muscle induction.\",\n      \"evidence\": \"Shh-null mice and presomitic mesoderm explants with recombinant Shh, including Myf5-null crosses\",\n      \"pmids\": [\"10457014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cis-element not yet mapped at this stage\", \"Region-specific dependence not generalized\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Revealed modular long-range control of Myf5 through multiple dispersed compartment-specific enhancers across the MRF4/Myf5 locus.\",\n      \"evidence\": \"Transgenic lacZ reporter analysis with systematic upstream deletions\",\n      \"pmids\": [\"10934019\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trans-acting factors for each enhancer not all identified at this stage\", \"Enhancer-promoter interaction logic not yet resolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Established MYF5 as a marker of committed, quiescent CD34+ satellite cells, linking the factor to the adult muscle stem cell compartment.\",\n      \"evidence\": \"Isolated myofibers, Myf5-nlacZ reporter mice, immunofluorescence and flow cytometry\",\n      \"pmids\": [\"11121437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of MYF5 in quiescence not addressed here\", \"Does not explain how protein is restrained in quiescence\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed Myf5 is regulated post-transcriptionally in neurons, where mRNA is correctly spliced but protein is absent, explaining the absence of myogenic conversion in brain.\",\n      \"evidence\": \"Protein and mRNA detection in brain neurons with Myf5-nlacZ reporter and retrograde labeling\",\n      \"pmids\": [\"8575308\", \"10603349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery blocking translation/stability in neurons not identified\", \"Whether this overlaps the satellite cell mechanism unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Positioned Notch signaling as acting between the Myf5 and MyoD steps, blocking progression of Myf5+ myoblasts to the MyoD stage without altering Myf5 expression.\",\n      \"evidence\": \"Retroviral Delta1 misexpression in chick limb with in situ hybridization\",\n      \"pmids\": [\"11060246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular targets of Notch at this transition not defined\", \"Mammalian validation not in this study\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapped a direct Gli-binding site in the Myf5 epaxial enhancer required for Shh-dependent activation, converting the Shh dependence into a defined cis-regulatory mechanism.\",\n      \"evidence\": \"Transgenic and luciferase reporters with Gli-site mutagenesis in Shh-null embryos\",\n      \"pmids\": [\"11782449\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cooperating factors at the enhancer not all defined here\", \"Other enhancers' direct inputs not addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Placed p300 HAT activity upstream of Myf5 induction, showing histone acetylation is specifically required for activating the determination gene.\",\n      \"evidence\": \"Allelic series of p300/CBP knockout and HAT-dead mice and ES cells with RT-PCR and immunostaining\",\n      \"pmids\": [\"14517256\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct recruitment of p300 to the Myf5 locus not demonstrated\", \"CBP/p300 nonredundancy mechanism unresolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linked Myf5 nuclear translocation to TGF-\\u03b2/Smad-driven contractile phenotype switching in pericytes, antagonized by FGF-2, suggesting a context outside classical myogenesis.\",\n      \"evidence\": \"RT-PCR, immunoprecipitation, EMSA and immunofluorescence in primary retinal pericytes\",\n      \"pmids\": [\"14578427\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-lab Co-IP/immunofluorescence without orthogonal validation\", \"Direct role of MYF5 in the phenotype switch not established\", \"Physiological significance unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Revised the determination hierarchy by showing Mrf4 can confer muscle identity when both Myf5 and MyoD are absent, placing Mrf4 alongside Myf5 upstream of MyoD.\",\n      \"evidence\": \"Allelic series of Myf5 mutants and Myf5:MyoD double-null mice with histology\",\n      \"pmids\": [\"15386014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of each determination gene by lineage unresolved\", \"Adult relevance addressed separately\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined direct Wnt/\\u03b2-catenin control of Myf5 through Tcf/Lef sites at the epaxial enhancer and showed synergy with the Shh/Gli pathway.\",\n      \"evidence\": \"In vivo Tcf/Lef site mutagenesis, \\u03b2-catenin gain/loss-of-function, Frizzled knockdown and reporters\",\n      \"pmids\": [\"16936075\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Integration with other enhancer inputs not fully mapped\", \"Quantitative contribution vs Shh not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified Six1/Six4 as direct regulators of Myf5 in limb myogenesis through binding a distal limb enhancer.\",\n      \"evidence\": \"EMSA, in vivo ChIP, enhancer mutagenesis and Six1/Six4 mutant mouse analysis\",\n      \"pmids\": [\"17592144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cooperating limb factors not all defined\", \"Relationship to Pax3 input at limb not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined a role for Myf5 in adult muscle regeneration, with Myf5-null muscle showing impaired regeneration, fibrosis, adipocyte accumulation and impaired myoblast proliferation.\",\n      \"evidence\": \"Myf5-null freeze-injury model with histology and in vitro proliferation assays\",\n      \"pmids\": [\"17961534\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinct from MyoD-redundant requirement not yet separated here\", \"Molecular mediators of the proliferation defect unidentified at this stage\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated by lineage tracing and ablation that a Myf5-independent MyoD lineage can sustain myogenesis, refining the two-lineage model and showing Myf5-lineage contribution to ribs.\",\n      \"evidence\": \"Myf5-Cre conditional ablation and Cre-dependent lineage tracing\",\n      \"pmids\": [\"18331721\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular determinants of the alternative lineage unknown\", \"Functional equivalence of the two lineages unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined a complex enhancer-promoter equilibrium mechanism with transcription balancing/cryptic promoter sequences governing the dynamic Mrf4/Myf5 expression patterns.\",\n      \"evidence\": \"Transgenic BAC/YAC reporter series with enhancer-promoter composition manipulation\",\n      \"pmids\": [\"18198342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Chromatin architecture mediating these equilibria not resolved\", \"Trans factors enforcing balancing not identified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked DUX4c to MYF5 protein stabilization and a proliferative, differentiation-inhibited myoblast state via physical interaction.\",\n      \"evidence\": \"Western blot, DNA-binding assay and single co-immunoprecipitation with overexpression in human myoblasts\",\n      \"pmids\": [\"19829708\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation\", \"Mechanism of stabilization not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined a Pax3\\u2192Dmrt2\\u2192Myf5 cascade in which Dmrt2 directly binds and transactivates the Myf5 epaxial enhancer, providing a molecular link from Pax3 to Myf5.\",\n      \"evidence\": \"EMSA, ChIP, transgenic enhancer analysis and conditional overexpression in mice\",\n      \"pmids\": [\"20368965\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How this cascade integrates with Shh/Wnt inputs not fully resolved\", \"Temporal ordering relative to other enhancer factors unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed Zic1/Zic2 potentiate Gli-dependent Myf5 activation, with Zic2 forming complexes with Gli2, integrating multiple dermomyotome inputs at the epaxial enhancer.\",\n      \"evidence\": \"In situ hybridization, reporter assays, co-immunoprecipitation and Zic2 mutant mouse analysis\",\n      \"pmids\": [\"21211521\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry/architecture of the Zic-Gli complex unknown\", \"Quantitative enhancer contribution not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established a translational control mechanism in quiescent satellite cells, where Myf5 mRNA is sequestered in mRNP granules with miR-31 and released upon activation, explaining MYF5 protein restraint despite mRNA presence.\",\n      \"evidence\": \"RNA immunoprecipitation, FISH, miR-31 manipulation, in vitro translation and in vivo regeneration\",\n      \"pmids\": [\"22770245\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full granule composition and assembly factors not defined\", \"Whether neuronal silencing uses the same machinery unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the Myf5 lineage as a precursor source for adipocytes, showing PTEN/PI3K signaling controls Myf5+ adipocyte expansion and that Myf5+ precursors yield brown and some white adipocytes.\",\n      \"evidence\": \"Myf5-Cre conditional Pten knockout with lineage tracing and fat depot analysis\",\n      \"pmids\": [\"22940198\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of MYF5 protein itself (vs lineage marking) in adipogenesis not addressed\", \"Mechanism of lineage bifurcation unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected Myf5 locus repression to nuclear lamina positioning, with emerin and HDAC3 required for lamina tethering before activation and relocation to nucleoplasm upon differentiation.\",\n      \"evidence\": \"ChIP, FISH for nuclear position, emerin/HDAC3 knockdown and HDAC3 catalytic activation\",\n      \"pmids\": [\"24062260\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality between positioning and expression not fully separated\", \"Single-lab data\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed Pax3 synergizes with Gli2 and Zic1 at the Myf5 epaxial enhancer and a novel promoter homeodomain motif, integrating the determination inputs onto endogenous Myf5.\",\n      \"evidence\": \"Transactivation reporters with domain mutagenesis and ChIP at endogenous Myf5 in 10T1/2 cells\",\n      \"pmids\": [\"24036067\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo requirement of the promoter motif not established\", \"Order of factor assembly unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Distinguished MYF5 from MyoD mechanistically by genome-wide ChIP-seq, showing MYF5 induces histone acetylation without Pol II recruitment or robust transcription, defining a chromatin-priming role preceding MyoD activation.\",\n      \"evidence\": \"ChIP-seq for MYF5, MyoD, histone marks and Pol II in myoblasts\",\n      \"pmids\": [\"26906734\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coactivators mediating MYF5 acetylation without activation not identified\", \"How priming is later read by MyoD unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Uncovered a non-transcriptional function of MYF5 as an RNA-binding protein that binds Ccnd1 mRNA and promotes CCND1 translation to support myoblast proliferation.\",\n      \"evidence\": \"RIP, biotin-RNA pulldown, UV crosslinking, EMSA and CCND1 rescue experiments\",\n      \"pmids\": [\"26819411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RNA-binding domain/motif on MYF5 not mapped\", \"Full mRNA target set incompletely defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established an absolute, redundant requirement for MyoD or Myf5 in muscle regeneration, with double-knockout satellite cells maintained but unable to differentiate after injury.\",\n      \"evidence\": \"Conditional MyoD/Myf5 double knockout in satellite cells with injury model and lineage tracing\",\n      \"pmids\": [\"29478898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular events that stabilize myogenic identity not detailed\", \"Individual contributions during regeneration not separated\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified SNAIL as a repressor of MYF5 in rhabdomyosarcoma, acting through an HDAC1/2 complex, linking MYF5 silencing to a tumor differentiation block.\",\n      \"evidence\": \"ChIP at MYF5 promoter, SNAIL knockdown, Co-IP of SNAIL-HDAC1/2 and xenograft model\",\n      \"pmids\": [\"29844345\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab characterization\", \"Direct vs indirect repression in normal myogenesis not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Implicated MLL1-mediated H3K4me3 in Myf5 promoter activation, linking this epigenetic mark to satellite cell proliferation and muscle repair.\",\n      \"evidence\": \"ChIP for H3K4me3, MLL1 knockdown, cell cycle analysis and cardiotoxin injury model\",\n      \"pmids\": [\"31840352\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct MLL1 recruitment mechanism to Myf5 not defined\", \"Single-lab data\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MYF5 acetylates muscle gene chromatin without activating transcription, and how this priming is subsequently decoded by MyoD to confer robust activation, remains unresolved.\",\n      \"evidence\": \"No direct experimental resolution in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coactivators/HATs recruited by MYF5 unidentified\", \"Molecular handoff from MYF5 priming to MyoD activation undefined\", \"MYF5 phosphodegron, responsible kinase and E3 ligase unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 3, 4, 34]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [35]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [14, 32, 40]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [31]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 9, 16, 17, 24]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1, 34]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 24, 20]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [31, 35]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"E12\", \"Gli2\", \"Zic2\", \"DUX4c\", \"SNAIL\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}