{"gene":"MEF2A","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2002,"finding":"Crystal structures of p38 MAP kinase complexed with docking site peptides from MEF2A (substrate) and MKK3b (activator) revealed that both peptides bind the same site in the C-terminal domain of p38, outside the active site and distinct from the 'CD' domain, inducing conformational changes in the active site and phosphorylation lip.","method":"X-ray crystallography; mutational analysis of p38–MEF2A docking interaction","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures solved at atomic resolution with mutational validation, single rigorous study with multiple orthogonal methods","pmids":["12086621"],"is_preprint":false},{"year":2000,"finding":"Crystal structure of MEF2A core (residues 2–78) bound to DNA at 1.5 Å resolution revealed how the absence of amino acids N-terminal to the MADS-box contributes to DNA-binding properties and that the MEF2 domain adopts a conformation considerably different from SRF and MCM1.","method":"X-ray crystallography","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure, foundational structural study","pmids":["10715212"],"is_preprint":false},{"year":2000,"finding":"NMR solution structure of the MEF2A–DNA complex showed that the MADS-box contacts both major and minor grooves, the MEF2S domain structure is entirely different from the SAM domain in SRF/MCM1, and critical protein–DNA contact differences explain the ~15° DNA bending by MEF2A versus ~70° by SRF/MCM1.","method":"NMR spectroscopy","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — solution NMR structure with detailed contact analysis, independent replication by crystal structure (PMID:10715212)","pmids":["10835359"],"is_preprint":false},{"year":2010,"finding":"Crystal structure of the MADS-box/MEF2 domain of MEF2A bound to DNA showed that the MEF2 domain participates with the MADS-box in both dimerization and DNA binding as a single domain, and that the ligand-binding pocket (for cofactors such as HDACs/myocardin family) is preformed by intrinsic folding rather than induced by cofactor binding.","method":"X-ray crystallography; homology modeling; mutagenesis","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis validation, corroborated by prior structural studies","pmids":["20132824"],"is_preprint":false},{"year":2024,"finding":"Crystal structure of an HDAC4–MEF2A–DNA complex revealed a 2:4:2 (HDAC4:MEF2A:DNA) dumbbell-shaped architecture in which two HDAC4 molecules dimerize via their glutamine-rich domain to bridge two MEF2A–DNA dimers; mutagenesis and luciferase assays confirmed that HDAC4 dimerization is required for its repression of MEF2A transcriptional activity.","method":"X-ray crystallography; biochemical mutagenesis assays; luciferase reporter assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus orthogonal mutagenesis and cell-based functional assays in a single study","pmids":["38281192"],"is_preprint":false},{"year":1993,"finding":"Mutational analysis (removal of N-terminal residues plus K154E substitution) demonstrated that DNA-binding specificity of SRF can be converted to that of MEF2A/RSRFC4, identifying that residues immediately N-terminal to the MADS box and position 154 determine binding-site specificity via an indirect mechanism not involving direct base recognition.","method":"Site-directed mutagenesis; DNA-binding assays (EMSA); ternary complex formation assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution-type mutagenesis with multiple functional readouts in a single focused study","pmids":["8095095"],"is_preprint":false},{"year":1999,"finding":"p38 MAP kinase phosphorylates MEF2A on serine and threonine residues within its transactivation domain, causing decreased electrophoretic mobility and increased transcriptional activity; PKCδ and PKCε also enhance MEF2A transactivation, whereas ERK1/2 and JNK/SAPK do not.","method":"Transient transfection reporter assays; metabolic 32P-labeling; immunoprecipitation; phosphopeptide mapping; phosphoamino acid analysis","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in-cell phosphorylation assay with peptide mapping, multiple orthogonal methods in one study","pmids":["10373581"],"is_preprint":false},{"year":2000,"finding":"HDAC5 interacts with MEF2A in vivo and in vitro and strongly represses its transcriptional activity; repression is independent of the HDAC5 deacetylase domain and instead mediated by the N-terminal non-deacetylase domain; the MADS-box/MEF2 domain of MEF2A interacts with a limited region in the N-terminal part of HDAC5.","method":"Co-immunoprecipitation (in vivo); in vitro binding assays; domain-mapping experiments; transcriptional reporter assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus in vitro binding and reporter assays, multiple orthogonal methods","pmids":["10748098"],"is_preprint":false},{"year":2003,"finding":"A 7-amino-acid deletion in MEF2A disrupts nuclear localization of MEF2A, reduces MEF2A-mediated transcription activation, and abolishes synergistic activation by MEF2A and GATA-1 through a dominant-negative mechanism; MEF2A protein is strongly expressed in the endothelium of coronary arteries.","method":"Functional luciferase reporter assays; subcellular localization studies; dominant-negative analysis","journal":"Science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional assays with multiple mechanistic readouts, single lab","pmids":["14645853"],"is_preprint":false},{"year":2006,"finding":"MEF2A is sumoylated primarily at lysine K395 both in vitro and in vivo; the nuclear E3 ligase PIAS1 promotes this sumoylation; mutation K395R abolishes sumoylation and results in enhanced transcriptional activity of MEF2A.","method":"In vitro and in vivo SUMOylation assays; site-directed mutagenesis; transcriptional reporter assays","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution plus in-cell assays, mutagenesis validation, single lab","pmids":["16563226"],"is_preprint":false},{"year":2012,"finding":"SENP2 is the de-SUMOylation enzyme for MEF2A; SENP2 knockdown or knockout increases detectable SUMOylated MEF2A; SENP2 accumulates in response to activity-dependent stimuli and thereby mediates activity-dependent MEF2A de-SUMOylation and transcriptional activation.","method":"shRNA screen; in vivo SUMOylation assays; SENP2 knockout embryos; transcriptional reporter assays","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA screen plus in vivo SUMOylation assays, single lab","pmids":["23224591"],"is_preprint":false},{"year":2014,"finding":"APC/C-Cdh1 interacts with and ubiquitinates SENP2 (recognizing a D-box motif) in the cytoplasm, targeting it for degradation; this controls MEF2A transcriptional activation in an activity-dependent manner, since activity-dependent stimuli prevent APC(Cdh1)-induced SENP2 ubiquitination, promote SENP2 nuclear accumulation, and cause MEF2A de-SUMOylation and acetylation.","method":"Co-immunoprecipitation; ubiquitination assays; luciferase reporter assays; SUMOylation/acetylation assays","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus functional ubiquitination/SUMOylation assays, single lab","pmids":["25483061"],"is_preprint":false},{"year":2002,"finding":"MEF2A-deficient mice exhibit pronounced right ventricular dilation, myofibrillar fragmentation, mitochondrial disorganization, activation of a fetal cardiac gene program, and sudden cardiac death; MEF2D transcriptional activity is paradoxically enhanced in mutant hearts, showing that MEF2D cannot compensate for MEF2A-specific functions in maintaining mitochondrial content and cytoarchitectural integrity.","method":"Mef2a knockout mouse; histology; electron microscopy; MEF2-dependent transgene reporter","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with multiple orthogonal phenotypic readouts, widely replicated concept","pmids":["12379849"],"is_preprint":false},{"year":2000,"finding":"MEF2A forms a MEF2A–MEF2D heterodimer (with no detectable MEF2A homodimers or MEF2A–MEF2C dimers) in heart and skeletal muscle; this heterodimer is the species that binds the MEF2 site in the GLUT4 promoter; immunodepletion of MEF2A–MEF2D abolishes MEF2 site binding and addition of MEF2A to diabetic nuclear extracts restores it; MEF2A is specifically down-regulated in insulin-deficient diabetes without effect on MEF2D in muscle.","method":"Co-immunoprecipitation with isoform-specific antibodies; EMSA; immunodepletion assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with multiple orthogonal binding assays, single lab","pmids":["10748204"],"is_preprint":false},{"year":1997,"finding":"The MEF2A 3′ UTR functions as a cis-acting translational repressor both in vivo and in vitro, with an internal conserved region responsible for inhibition; this repression is independent of mRNA steady-state levels and is relaxed during muscle cell differentiation.","method":"CAT reporter gene fusion assays in vivo; in vitro translation in rabbit reticulocyte lysates; RNase protection assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro reconstitution plus in-vivo reporter assays with orthogonal mRNA analysis, single lab","pmids":["9111346"],"is_preprint":false},{"year":2004,"finding":"ERK5 uses a docking domain (phi_A-X-phi_B motif) in MEF2A to promote both in vitro phosphorylation and in vivo transcriptional activation of MEF2A; the specificity determinants for ERK5 at the MEF2A docking domain are similar to those for p38; the catalytic domain of ERK5 recognizes the docking domain.","method":"In vitro kinase assays; mutational analysis of MEF2A docking domain; in vivo transcriptional activation assays","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro phosphorylation plus in-vivo activation assays, mutagenesis, single lab","pmids":["15132737"],"is_preprint":false},{"year":2013,"finding":"Sumoylated MEF2A acts as a transcriptional repressor to eliminate orphan presynaptic sites in neurons; knockdown of MEF2A in rat cerebellar cortex in vivo increases orphan presynaptic site density; sumoylated MEF2A directly represses the synaptotagmin 1 (Syt1) gene, and Syt1 repression mediates MEF2A-dependent elimination of orphan presynaptic sites, which promotes accumulation of presynaptic material at maturing boutons.","method":"In vivo knockdown (rat cerebellar cortex); direct target gene identification; reporter assays; neuronal culture experiments","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockdown with defined target gene and rescue experiments, single lab","pmids":["23486945"],"is_preprint":false},{"year":2014,"finding":"MEF2A undergoes chaperone-mediated autophagy (CMA)-dependent degradation by lysosomes under basal conditions; mild oxidative stress enhances MEF2A degradation and activity, whereas excessive oxidative stress disrupts lysosomal integrity causing accumulation of non-functional MEF2A and production of an HDAC4 N-terminal cleavage product (HDAC4-NT) by lysosomal serine proteases, which acts as a MEF2 repressor.","method":"Lysosomal fractionation; CMA pathway inhibition; oxidative stress treatments; western blot; DNA-binding and transcriptional activity assays","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple subcellular fractionation and pathway inhibition experiments, single lab","pmids":["24879151"],"is_preprint":false},{"year":2012,"finding":"MEF2A ubiquitination in dopaminergic neurons is isoform-specific (MEF2A but not MEF2C or MEF2D); ubiquitination occurs at the N-terminus, first detectable in the nuclear compartment then in the cytoplasm; ubiquitinated MEF2A has reduced DNA-binding and transcriptional activity; neurotoxins that cause proteasome pathway disruption lead to accumulation of ubiquitinated MEF2A and impaired neuronal viability.","method":"Ubiquitination assays in neuronal SN4741 cells; subcellular fractionation; DNA-binding activity assays; proteasome inhibitor treatments","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal assays in neuronal cells, single lab","pmids":["22764880"],"is_preprint":false},{"year":2003,"finding":"p300/CBP binds the N-terminal domain of both TR and MEF2A via the same C-terminal portion of p300; TR, MEF2A, and p300 form a ternary complex in vivo; p300/CBP modulates transactivation of the TR-RxR-MEF2A complex at a thyroid hormone response element; adenovirus E1A inhibits TR-RxR-MEF2A-p300 activation but not TR-RxR-MEF2A alone, indicating p300 recruits an inhibitor.","method":"GST pull-down; co-immunoprecipitation; domain mapping; CAT reporter assays in U2OS cells","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pulldown plus co-IP plus reporter assays, single lab","pmids":["12371907"],"is_preprint":false},{"year":2004,"finding":"PITX2a directly interacts with MEF2A (demonstrated by yeast two-hybrid and GST pull-down); coexpression of MEF2A and PITX2a/Pitx2c results in strong synergistic activation of the ANF promoter in a cell-type- and promoter-context-specific manner (LS8 cells but not NIH/3T3, CHO, or C2C12); synergism requires MEF2 binding sites and DNA binding by MEF2A.","method":"Yeast two-hybrid; GST pull-down; luciferase reporter assays; cell-type specificity analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus GST pulldown plus reporter assays, single lab","pmids":["15466416"],"is_preprint":false},{"year":2008,"finding":"GLUT4 enhancer factor (GEF) dimerizes with hypophosphorylated MEF2A with increased affinity; MEF2A binding to its cognate site increases the DNA binding activity of GEF to Domain I of the GLUT4 promoter; HDAC5 interacts with GEF and specifically inhibits GLUT4 promoter activity.","method":"Co-immunoprecipitation; EMSA; luciferase reporter assays; domain mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus EMSA plus reporter assays, single lab","pmids":["18216015"],"is_preprint":false},{"year":2006,"finding":"Myomaxin (a Xin-related protein) is a direct downstream transcriptional target of MEF2A; it is markedly down-regulated in Mef2a knockout hearts; myomaxin localizes to the Z-disc/costameric region and interacts with the sarcomeric Z-disc protein alpha-actinin-2.","method":"Mef2a knockout mouse; microarray expression analysis; co-immunoprecipitation (myomaxin–alpha-actinin-2); immunolocalization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout plus Co-IP plus localization, single lab","pmids":["17046827"],"is_preprint":false},{"year":2006,"finding":"Myospryn is a direct downstream transcriptional target of MEF2A, identified by microarray in Mef2a knockout mice; myospryn localizes to the costamere and interacts with alpha-actinin-2.","method":"Mef2a knockout mouse; microarray expression analysis; co-immunoprecipitation (myospryn–alpha-actinin-2); immunolocalization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout plus Co-IP plus localization, single lab","pmids":["16407236"],"is_preprint":false},{"year":2011,"finding":"MEF2A directly regulates a cohort of costamere genes in cardiac muscle; acute knockdown of Mef2a in primary neonatal cardiomyocytes causes profound myofibril and focal adhesion malformations and adhesion-dependent programmed cell death, identifying a role for MEF2A in cardiomyocyte survival through regulation of costamere integrity.","method":"Mef2a knockout mouse; expression analysis; Mef2a siRNA knockdown in primary cardiomyocytes; immunofluorescence; apoptosis assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout corroborated by acute knockdown with defined cellular phenotypes, single lab","pmids":["21724844"],"is_preprint":false},{"year":2012,"finding":"MEF2A directly regulates the Gtl2-Dio3 miRNA mega-cluster; Gtl2-Dio3-encoded miRNAs repress secreted Frizzled-related proteins (sFRPs), inhibitors of WNT signaling; in Mef2a knockout regenerating muscle these miRNAs are downregulated, sFRP expression is upregulated, and WNT activity is attenuated; myogenic differentiation in MEF2A-deficient myoblasts is rescued by miR-410/miR-433 overexpression or recombinant WNT3A/WNT5A treatment.","method":"Mef2a knockout mouse; muscle regeneration assays; miRNA expression profiling; rescue with miRNA overexpression and recombinant WNTs","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout with mechanistic rescue experiments, single lab","pmids":["23154418"],"is_preprint":false},{"year":2010,"finding":"MEF2A activates Xirp2 expression in response to angiotensin II by directly stimulating MEF2A transcriptional activity at the Xirp2 promoter; Xirp2 (an actin-binding protein) functions downstream of MEF2A to modulate Ang II-mediated pathological cardiac remodeling.","method":"Xirp2 promoter characterization; MEF2A binding assays; Xirp2 hypomorphic mouse with Ang II infusion","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter binding assays plus in vivo hypomorphic model, single lab","pmids":["20093629"],"is_preprint":false},{"year":2009,"finding":"TGF-β transcriptionally induces MMP-10 through MEF2A; TGF-β promotes proteasome-dependent degradation of class IIa HDACs, resulting in increased histone acetylation around the MEF2 site on the MMP-10 promoter and increased MEF2A binding; knockdown of MEF2A reduces and overexpression increases TGF-β-induced MMP-10 expression.","method":"MEF2A knockdown/overexpression; ChIP assay; luciferase reporter assays; HDAC knockdown/overexpression","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus knockdown/overexpression plus reporter assays, single lab","pmids":["19935709"],"is_preprint":false},{"year":2008,"finding":"CaMK II activation during exercise is required for histone H3 hyperacetylation at the GLUT4 MEF2 site and for increased MEF2A binding to this site in vivo; inhibition of CaMK II with KN93 prior to exercise abolishes these increases and attenuates exercise-induced GLUT4 mRNA and protein increases.","method":"In vivo exercise model; chromatin immunoprecipitation (ChIP); Western blot; RT-PCR; CaMK II inhibitor (KN93)","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP in vivo with pharmacological inhibition, single lab","pmids":["18647882"],"is_preprint":false},{"year":2006,"finding":"Exercise increases MEF2A binding to the GLUT4 promoter in vivo; CaMK signaling mediates MEF2A/DNA associations, as constitutively active CaMK IV increases MEF2A binding by ~75% compared to dominant-negative CaMK IV in C2C12 myotubes.","method":"In vivo exercise model; ChIP assay; constitutively active and dominant-negative CaMK IV overexpression","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo ChIP corroborated by CaMK gain/loss-of-function in cell culture, single lab","pmids":["16985263"],"is_preprint":false},{"year":2010,"finding":"MEF2A is present on the c-Jun promoter in macrophages; MEF2A/MEF2D heterodimers strongly interact with HDAC1 (and to a lesser extent HDAC7) in macrophages; endogenous p300 associates with MEF2A only in differentiated macrophages (not undifferentiated cells or monocytes), indicating a switch from repressor to activator complex during differentiation.","method":"Chromatin immunoprecipitation (ChIP); co-immunoprecipitation; trichostatin A treatment","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus reciprocal Co-IP, single lab","pmids":["20590529"],"is_preprint":false},{"year":2022,"finding":"HDAC5 interacts with MEF2A and suppresses MEF2A binding to the Smad7 promoter, resulting in Smad7 promoter activity repression; luciferase reporter and ChIP-qPCR assays confirmed this interaction; HDAC5 deficiency increases Smad7 expression, which in turn decreases TGF-β1-induced Smad2/3 phosphorylation.","method":"Luciferase reporter assays; ChIP-qPCR; HDAC5 knockdown; in vivo scar model","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus reporter assays plus in vitro/in vivo knockdown, single lab","pmids":["36263180"],"is_preprint":false},{"year":2004,"finding":"MEF2A nuclear translocation is regulated by p38 and calcineurin in a biphasic, time-dependent manner in response to static stretch; stretch produces increased p38 phosphorylation preceding MEF2A nuclear translocation; inhibition of p38 (SB-203580) or calcineurin (cyclosporine A) blocks MEF2A phosphorylation and nuclear translocation.","method":"Pharmacological inhibition (SB-203580, cyclosporine A); Western blot; subcellular fractionation/nuclear translocation assays; static stretch application in C2C12 myocytes","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with multiple readouts, single lab","pmids":["15483225"],"is_preprint":false},{"year":2011,"finding":"MEF2A directly binds MEF2A-binding sites in the promoter region of Xirp2 (Myomaxin/Myospryn network) and a cohort of costamere genes, establishing MEF2A as a direct transcriptional regulator of a costamere gene program in cardiac muscle.","method":"ChIP assay; Mef2a knockout mouse; luciferase reporter assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP in vivo plus reporter assays, single lab","pmids":["21724844"],"is_preprint":false},{"year":2014,"finding":"MEF2A binds the Cpt1b promoter in skeletal muscle; exercise training elevates MEF2A binding and reduces HDAC5 binding at the Cpt1b promoter; exercise induces MEF2A hyperacetylation which correlates with enhanced DNA-binding; HDAC5 and HDAC3 binding to MEF2A decreases with exercise; MEF2A overexpression increases Cpt1b mRNA expression suppressed by HDAC5.","method":"ChIP assay; co-immunoprecipitation; MEF2A overexpression; luciferase reporter assays; exercise treadmill model","journal":"Acta physiologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus Co-IP plus reporter assays in exercise model, single lab","pmids":["25213552"],"is_preprint":false},{"year":2011,"finding":"MEF2A directly binds the promoter region of ZEB2 and CTNNB1 to initiate their transcription in colorectal cancer cells, promoting EMT and WNT/β-catenin signaling; demonstrated by direct promoter binding assays.","method":"ChIP assay; luciferase reporter assays; MEF2A overexpression/knockdown","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus reporter assays plus gain/loss-of-function, single lab","pmids":["33863999"],"is_preprint":false},{"year":2011,"finding":"AMPKα2 regulates MEF2A nuclear translocation and MEF2A binding to the Glut4 promoter; overexpression of AMPKα2 increases nuclear MEF2A content and promoter-bound MEF2A, while knockout attenuates these effects; however, AMPKα2 does not regulate HDAC5 nuclear export after 28 days of training.","method":"AMPKα2 OE and KO mice; treadmill training; ChIP assay; Western blot; co-immunoprecipitation","journal":"Medicine and science in sports and exercise","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic OE and KO mice with ChIP and Co-IP, single lab","pmids":["21233771"],"is_preprint":false},{"year":2018,"finding":"MEF2A is required for Group I mGluR-mediated GluA2 AMPA receptor internalization in neurons; knockdown of MEF2A specifically abolishes mGluR-dependent GluA2 internalisation without affecting basal AMPAR expression or trafficking; this process is independent of Arc/Arg3.1 expression.","method":"MEF2A knockdown in primary neuronal culture; GluA2 trafficking assays; Arc/Arg3.1 expression analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with defined trafficking readout and negative control for Arc, single lab","pmids":["29588465"],"is_preprint":false},{"year":2017,"finding":"MEF2A/D-dependent transcription (specifically MEF2A/D) is required for synapse silencing (depression of AMPAR transmission) induced by 1-hour theta-frequency burst firing in CA1 neurons; MEF2A/D-induced Arc expression contributes to synapse silencing and elimination; more prolonged (24-hr) firing-induced spine elimination did not require MEF2A/D.","method":"Optogenetics; MEF2A/D loss-of-function; Arc expression measurement; electrophysiology (AMPAR and NMDAR EPSCs); de novo transcription inhibition","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — optogenetic manipulation plus loss-of-function with electrophysiological readouts, single lab","pmids":["28901289"],"is_preprint":false},{"year":2018,"finding":"MEF2A directly binds the Calpain 3 (Capn3) promoter and positively regulates Capn3 expression; demonstrated by luciferase reporter assay, EMSA, and ChIP in rat denervated gastrocnemius muscle; MEF2A siRNA knockdown in L6 myoblasts reduces Capn3 protein.","method":"Luciferase reporter assay; EMSA; ChIP; siRNA knockdown; Western blot","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus EMSA plus reporter assays plus siRNA, single lab","pmids":["29783071"],"is_preprint":false},{"year":2020,"finding":"MEF2A loss-of-function variant (p.Gly240*) abolishes transactivation on target genes MYH6 and FHL2 and nullifies synergistic activation between MEF2A and GATA4, establishing MEF2A loss-of-function as predisposing to dilated cardiomyopathy.","method":"Whole-exome sequencing; Sanger sequencing; dual-luciferase assay; functional characterization of variant","journal":"Clinical chemistry and laboratory medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct luciferase functional assays with defined target genes and co-factor synergy, single lab","pmids":["33554560"],"is_preprint":false},{"year":2017,"finding":"MEF2A immunoprecipitation followed by RNA isolation confirmed direct binding of MEF2A protein to pri-miR-494 RNA, suggesting a novel post-transcriptional function of MEF2A as an RNA-binding protein regulating processing of 14q32 microRNAs miR-329 and miR-494.","method":"MEF2A immunoprecipitation followed by RNA isolation and RT-qPCR; in vivo hind-limb ischemia model with MEF2A gene silencing","journal":"Molecular therapy. Nucleic acids","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single RIP experiment in one lab; novel and unexpected function requiring further validation","pmids":["28624225"],"is_preprint":false},{"year":2023,"finding":"MEF2A loss leads to R-loop accumulation and activates the DDX41–cGAS–STING interferon pathway; MEF2A-deficient cells show ATR kinase activation, which is necessary for STING activation; MEF2A thus sustains transcriptional homeostasis and suppresses unscheduled interferon responses.","method":"MEF2A loss-of-function; R-loop detection assays; ATR inhibition experiments; STING pathway activation measurements; interferon reporter assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple pathway readouts and epistasis (ATR inhibition), single lab","pmids":["37467105"],"is_preprint":false},{"year":2017,"finding":"MEF2A transcriptional activation in response to oxytocin (OT) involves reduced phosphorylation of MEF2A at Serine 408, under control of the OTR-coupled MAPK (MEK1/2) pathway; MEK1/2 inhibition (U0126) blocks MEF2A activation; siRNA-mediated MEF2A knockdown prevents OT-induced neurite retraction in hypothalamic neurons.","method":"Pharmacological inhibition (U0126); siRNA knockdown of MEF2A; Western blot for pSer408-MEF2A; neurite morphology measurements","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA plus pharmacological inhibition with defined morphological readout, single lab","pmids":["29928931"],"is_preprint":false},{"year":2018,"finding":"MEF2A and MEF2D function as scaffold proteins interacting with HDAC1 (in undifferentiated THP-1 cells) or p300 (in TPA-differentiated THP-1 cells) at the SOD3 promoter region, mediating switches between repression and activation of SOD3 gene expression.","method":"ChIP assay; co-immunoprecipitation; MEF2A/MEF2D knockdown; Western blot","journal":"Free radical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus Co-IP plus knockdown with defined gene expression readout, single lab","pmids":["29842805"],"is_preprint":false},{"year":2024,"finding":"MEF2A directly activates transcription of PGC1α and inhibits transcription of KEAP1, thereby promoting mitochondrial biogenesis and activating the KEAP1/NRF2 pathway to modulate reactive oxygen species levels and confer cisplatin resistance in gastric cancer cells.","method":"MEF2A overexpression/knockdown; luciferase reporter assays for PGC1α and KEAP1 promoters; in vitro and in vivo cisplatin sensitivity assays","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assays plus gain/loss-of-function in vitro and in vivo, single lab","pmids":["39237047"],"is_preprint":false},{"year":2024,"finding":"MEF2A directly modulates CYP7A1 transcription as confirmed by dual luciferase reporter assays; MEF2A knockdown in HepG2 cells leads to CYP7A1 downregulation and lipid accumulation, while overexpression reverses these effects; reduced MEF2A expression in offspring of HFD-fed dams is attributable to DNA hypermethylation in the MEF2A promoter region.","method":"Dual luciferase reporter assays; MEF2A knockdown/overexpression; MassARRAY EpiTYPER methylation analysis; 5-azacitidine treatment","journal":"Cellular & molecular biology letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct reporter assay plus gain/loss-of-function plus methylation analysis, single lab","pmids":["39695937"],"is_preprint":false}],"current_model":"MEF2A is a MADS-box/MEF2-domain transcription factor that binds A+T-rich DNA as homodimers or heterodimers (predominantly MEF2A–MEF2D in muscle), is activated by p38 MAPK and ERK5 phosphorylation at its transactivation domain and by CaMK-dependent mechanisms, and is repressed by class IIa HDACs (HDAC4/5) that bind its MEF2 domain and by SUMO-1 modification at K395 (with PIAS1 as E3 ligase and SENP2 as the de-SUMOylation enzyme); it directly regulates programs of muscle-specific structural genes (costamere, GLUT4, Cpt1b, myomaxin, myospryn), controls mitochondrial biogenesis and cytoarchitectural integrity in the postnatal heart, drives skeletal muscle regeneration via the Gtl2-Dio3 miRNA–WNT signaling axis, and in neurons governs activity-dependent synapse elimination, AMPAR trafficking, and interferon threshold via transcriptional homeostasis."},"narrative":{"mechanistic_narrative":"MEF2A is a MADS-box/MEF2-domain transcription factor that binds A+T-rich DNA and orchestrates muscle, cardiac, and neuronal gene programs through combinatorial cofactor recruitment and signal-dependent post-translational control [PMID:20132824, PMID:12379849]. Its core MADS-box plus MEF2 domain functions as a single integrated module mediating both dimerization and DNA binding, contacting major and minor grooves to bend DNA ~15° and presenting a preformed cofactor-binding pocket; residues N-terminal to the MADS-box and position 154 dictate the binding-site specificity that distinguishes MEF2A from SRF [PMID:10835359, PMID:20132824, PMID:8095095]. In muscle MEF2A predominantly acts as a MEF2A–MEF2D heterodimer, the species that occupies sites such as the GLUT4 promoter [PMID:10748204]. MEF2A activity is gated by an opposing set of inputs: p38 MAPK and ERK5 dock on its transactivation domain and phosphorylate it to increase activity, while class IIa HDACs (HDAC4/HDAC5) bind the MADS-box/MEF2 domain to repress it—HDAC4 dimerizing via its glutamine-rich region to bridge two MEF2A–DNA complexes—and CaMK signaling promotes MEF2A nuclear translocation and promoter binding [PMID:12086621, PMID:38281192, PMID:10373581, PMID:10748098, PMID:15132737, PMID:16985263]. A SUMOylation switch at K395, installed by PIAS1 and reversed by SENP2 (whose stability is in turn controlled by APC/C-Cdh1), converts MEF2A between repressive and active states in an activity-dependent manner [PMID:16563226, PMID:23224591, PMID:25483061]. Functionally, MEF2A directly drives a costamere/Z-disc structural gene program (myomaxin, myospryn, Xirp2) required for cardiomyocyte cytoarchitecture and survival, and its loss in mice causes mitochondrial disorganization, myofibrillar fragmentation, and sudden cardiac death that MEF2D cannot rescue [PMID:12379849, PMID:17046827, PMID:16407236, PMID:21724844]. In neurons, SUMOylated MEF2A represses synaptotagmin-1 to eliminate orphan presynaptic sites and MEF2A/D-dependent transcription drives activity-dependent synapse silencing and AMPAR trafficking [PMID:23486945, PMID:29588465, PMID:28901289]. A loss-of-function variant (p.Gly240*) that abolishes MYH6/FHL2 transactivation and MEF2A–GATA4 synergy links MEF2A to dilated cardiomyopathy [PMID:33554560]. MEF2A also sustains genome/transcriptional homeostasis, with its loss provoking R-loop accumulation and DDX41–cGAS–STING interferon activation [PMID:37467105].","teleology":[{"year":1993,"claim":"Before MEF2A's DNA-recognition logic was known, it was unclear how a MADS-box factor achieves binding specificity distinct from SRF; swapping defined residues established that specificity is encoded by sequences N-terminal to the MADS-box and position 154 through an indirect mechanism.","evidence":"Site-directed mutagenesis converting SRF specificity to MEF2A, with EMSA and ternary complex assays","pmids":["8095095"],"confidence":"High","gaps":["Did not resolve the atomic basis of the indirect specificity","Did not address dimer partner contributions to site selection"]},{"year":2000,"claim":"To explain how MEF2A engages DNA differently from related MADS-box proteins, structural studies showed the MEF2 domain adopts a fold distinct from SRF/MCM1, contacts both grooves, and bends DNA only ~15°.","evidence":"X-ray crystallography (1.5 Å) and NMR solution structure of MEF2A–DNA complexes","pmids":["10715212","10835359"],"confidence":"High","gaps":["Did not capture cofactor-bound states","Limited to the DNA-binding core, not full-length protein"]},{"year":2000,"claim":"It was unknown which MEF2 species binds physiological promoters in muscle; isoform-specific antibody work showed MEF2A acts as a MEF2A–MEF2D heterodimer that occupies the GLUT4 promoter and is selectively lost in diabetic muscle.","evidence":"Co-IP with isoform-specific antibodies, EMSA, and immunodepletion from heart/muscle extracts","pmids":["10748204"],"confidence":"High","gaps":["Did not establish heterodimer composition across non-muscle tissues","Mechanism of diabetes-specific MEF2A downregulation unresolved"]},{"year":1999,"claim":"To define activating signals, it was shown that p38 MAPK (and PKCδ/ε) but not ERK1/2 or JNK phosphorylates the MEF2A transactivation domain to increase its transcriptional output.","evidence":"Reporter assays, 32P metabolic labeling, phosphopeptide mapping","pmids":["10373581"],"confidence":"High","gaps":["Did not map all phospho-sites to downstream gene programs","In vivo relevance of PKC inputs untested"]},{"year":2002,"claim":"The structural basis of MEF2A as a kinase substrate was resolved by showing p38 docks MEF2A and its activator MKK3b at the same C-terminal site outside the active site, coupling docking to active-site rearrangement.","evidence":"Crystal structures of p38–MEF2A and p38–MKK3b docking peptides with mutational analysis","pmids":["12086621"],"confidence":"High","gaps":["Did not address how docking specificity is shared with ERK5","Full-length kinase–substrate complex not solved"]},{"year":2004,"claim":"A second MAPK input was defined: ERK5 uses a phi_A-X-phi_B docking motif in MEF2A—similar to p38 determinants—to phosphorylate and activate it.","evidence":"In vitro kinase assays and docking-domain mutagenesis with in vivo activation readouts","pmids":["15132737"],"confidence":"Medium","gaps":["Target gene specificity of ERK5 versus p38 signaling unresolved","Structural docking model not directly determined"]},{"year":2000,"claim":"The repressive arm of MEF2A control was identified: HDAC5 binds the MADS-box/MEF2 domain via its N-terminal non-deacetylase region to repress activity independently of catalysis.","evidence":"Reciprocal Co-IP, in vitro binding, domain mapping, reporter assays","pmids":["10748098"],"confidence":"High","gaps":["Did not define the stoichiometry of the repressive complex","Signals releasing HDAC5 not addressed here"]},{"year":2010,"claim":"Structural work clarified that the MADS-box/MEF2 domain folds the cofactor pocket intrinsically and acts as one DNA-binding/dimerization unit, explaining how HDAC and myocardin-family cofactors share a preformed binding surface.","evidence":"Crystal structure of the MADS-box/MEF2 domain on DNA with homology modeling and mutagenesis","pmids":["20132824"],"confidence":"High","gaps":["Did not capture an actual cofactor in the pocket","Competition between activators and repressors not structurally resolved"]},{"year":2024,"claim":"The architecture of HDAC-mediated repression was solved, showing two HDAC4 molecules dimerize through their glutamine-rich domain to bridge two MEF2A–DNA dimers, and that this dimerization is required for repression.","evidence":"Crystal structure of HDAC4–MEF2A–DNA (2:4:2) with mutagenesis and luciferase assays","pmids":["38281192"],"confidence":"High","gaps":["In vivo prevalence of the dumbbell complex unquantified","Whether HDAC5 adopts the same architecture not shown"]},{"year":2006,"claim":"A SUMO-based off-switch was identified: MEF2A is SUMOylated at K395 by PIAS1, and the K395R mutant has enhanced transcriptional activity.","evidence":"In vitro and in vivo SUMOylation assays, mutagenesis, reporter assays","pmids":["16563226"],"confidence":"Medium","gaps":["Did not identify the de-SUMOylation enzyme","Gene-specific consequences of K395 SUMOylation not mapped"]},{"year":2012,"claim":"The reversal of the SUMO switch was assigned to SENP2, which de-SUMOylates MEF2A and accumulates after activity-dependent stimuli to drive activation.","evidence":"shRNA screen, in vivo SUMOylation assays, SENP2 knockout embryos, reporter assays","pmids":["23224591"],"confidence":"Medium","gaps":["How activity stabilizes SENP2 was not yet explained","Direct neuronal target genes not enumerated"]},{"year":2014,"claim":"The upstream control of SENP2 was traced to APC/C-Cdh1, which ubiquitinates SENP2 via a D-box; activity-dependent signals block this degradation, allowing nuclear SENP2 to de-SUMOylate and de-repress MEF2A.","evidence":"Co-IP, ubiquitination assays, reporter and SUMOylation/acetylation assays","pmids":["25483061"],"confidence":"Medium","gaps":["The signal coupling activity to APC/C inhibition not defined","Single-lab pathway without independent confirmation"]},{"year":2002,"claim":"The in vivo physiological requirement for MEF2A was established by knockout mice showing right ventricular dilation, mitochondrial disorganization, myofibrillar fragmentation, and sudden death not rescued by MEF2D.","evidence":"Mef2a knockout mouse with histology, EM, and MEF2-dependent transgene reporter","pmids":["12379849"],"confidence":"High","gaps":["Did not identify the direct target genes responsible for the phenotype","Basis of MEF2D non-redundancy not molecularly defined"]},{"year":2006,"claim":"Direct cardiac structural targets were identified—myomaxin and myospryn—both downregulated in Mef2a-null hearts and localizing to the Z-disc/costamere via alpha-actinin-2.","evidence":"Mef2a knockout microarray, Co-IP with alpha-actinin-2, immunolocalization","pmids":["17046827","16407236"],"confidence":"Medium","gaps":["Direct promoter occupancy not shown in these reports","Functional contribution of each target to phenotype untested"]},{"year":2011,"claim":"MEF2A was shown to directly bind a cohort of costamere gene promoters, and acute knockdown caused myofibril/focal-adhesion malformations and adhesion-dependent cell death, defining a survival role through costamere integrity.","evidence":"ChIP, Mef2a knockout, siRNA in primary cardiomyocytes, immunofluorescence, apoptosis assays","pmids":["21724844","33863999"],"confidence":"Medium","gaps":["Which individual costamere targets are essential for survival not isolated","Mechanism linking costamere loss to apoptosis incomplete"]},{"year":2012,"claim":"A regeneration mechanism was defined whereby MEF2A drives the Gtl2-Dio3 miRNA cluster that represses sFRPs to sustain WNT signaling, with myogenic defects rescued by miR-410/433 or recombinant WNTs.","evidence":"Mef2a knockout muscle regeneration, miRNA profiling, miRNA and WNT rescue","pmids":["23154418"],"confidence":"Medium","gaps":["Direct MEF2A occupancy at the Gtl2-Dio3 locus quantification limited","Generalizability beyond regeneration context untested"]},{"year":2013,"claim":"In neurons, SUMOylated MEF2A was shown to function as a repressor of synaptotagmin-1 to eliminate orphan presynaptic sites, linking the SUMO switch to synaptic refinement.","evidence":"In vivo knockdown in rat cerebellar cortex, target gene identification, reporter assays","pmids":["23486945"],"confidence":"Medium","gaps":["Full repressive cofactor complex on Syt1 not defined","Single-lab in vivo result"]},{"year":2018,"claim":"MEF2A's role in postsynaptic plasticity was extended by showing MEF2A is required for Group I mGluR-mediated GluA2 AMPAR internalization, independent of Arc, and MEF2A/D transcription drives activity-dependent synapse silencing.","evidence":"siRNA/loss-of-function with GluA2 trafficking and electrophysiology, optogenetics","pmids":["29588465","28901289"],"confidence":"Medium","gaps":["The MEF2A target genes mediating GluA2 internalization not identified","Distinction of MEF2A versus MEF2D contributions incomplete"]},{"year":2020,"claim":"A human disease link was established: the MEF2A p.Gly240* loss-of-function variant abolishes MYH6/FHL2 transactivation and MEF2A–GATA4 synergy, predisposing to dilated cardiomyopathy.","evidence":"Whole-exome/Sanger sequencing with dual-luciferase functional characterization","pmids":["33554560"],"confidence":"Medium","gaps":["Causality in a model organism not demonstrated","Penetrance and mechanism in patient hearts not established"]},{"year":2023,"claim":"A genome-homeostasis function was revealed: MEF2A loss causes R-loop accumulation and ATR-dependent activation of the DDX41–cGAS–STING interferon pathway, positioning MEF2A as a suppressor of unscheduled interferon responses.","evidence":"Loss-of-function with R-loop detection, ATR-inhibition epistasis, STING/interferon reporters","pmids":["37467105"],"confidence":"Medium","gaps":["Whether R-loops arise from direct MEF2A transcriptional targets unclear","Tissue contexts for this homeostatic role untested"]},{"year":null,"claim":"How the competing post-translational inputs (MAPK phosphorylation, SUMOylation, acetylation, ubiquitination, CMA-mediated turnover) are integrated at specific promoters to select repressor versus activator complexes in a given tissue remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of the modification code","Cell-type-specific cofactor selection rules undefined","Direct genome-wide MEF2A target maps not integrated with modification states"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,6,12,16,33,40,45]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[2,3,5,13,33,39]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[41]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[8,32,36]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11,18]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,6,12,33]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,15,28,32]},{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[12,22,23,24]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[16,37,38]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[12,25]}],"complexes":["MEF2A–MEF2D heterodimer","HDAC4–MEF2A–DNA repressive complex","TR–RxR–MEF2A–p300 complex"],"partners":["MEF2D","HDAC5","HDAC4","HDAC1","P300","GATA4","PITX2","SENP2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q02078","full_name":"Myocyte-specific enhancer factor 2A","aliases":["Serum response factor-like protein 1"],"length_aa":507,"mass_kda":54.8,"function":"Transcriptional activator which binds specifically to the MEF2 element, 5'-YTA[AT](4)TAR-3', found in numerous muscle-specific genes. Also involved in the activation of numerous growth factor- and stress-induced genes. Mediates cellular functions not only in skeletal and cardiac muscle development, but also in neuronal differentiation and survival. Plays diverse roles in the control of cell growth, survival and apoptosis via p38 MAPK signaling in muscle-specific and/or growth factor-related transcription. In cerebellar granule neurons, phosphorylated and sumoylated MEF2A represses transcription of NUR77 promoting synaptic differentiation. Associates with chromatin to the ZNF16 promoter","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q02078/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MEF2A","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MEF2A","total_profiled":1310},"omim":[{"mim_id":"616246","title":"MYOREGULIN; MRLN","url":"https://www.omim.org/entry/616246"},{"mim_id":"612193","title":"CARDIOMYOPATHY-ASSOCIATED PROTEIN 5; CMYA5","url":"https://www.omim.org/entry/612193"},{"mim_id":"610254","title":"MICRO RNA 133A1; MIR133A1","url":"https://www.omim.org/entry/610254"},{"mim_id":"609979","title":"VESTIGIAL-LIKE 2; VGLL2","url":"https://www.omim.org/entry/609979"},{"mim_id":"609778","title":"XIN ACTIN-BINDING REPEAT-CONTAINING PROTEIN 2; XIRP2","url":"https://www.omim.org/entry/609778"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MEF2A"},"hgnc":{"alias_symbol":["RSRFC4","RSRFC9"],"prev_symbol":[]},"alphafold":{"accession":"Q02078","domains":[{"cath_id":"3.40.1810.10","chopping":"13-93","consensus_level":"high","plddt":95.9436,"start":13,"end":93}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02078","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q02078-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q02078-F1-predicted_aligned_error_v6.png","plddt_mean":54.72},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MEF2A","jax_strain_url":"https://www.jax.org/strain/search?query=MEF2A"},"sequence":{"accession":"Q02078","fasta_url":"https://rest.uniprot.org/uniprotkb/Q02078.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q02078/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02078"}},"corpus_meta":[{"pmid":"19188439","id":"PMC_19188439","title":"MicroRNA-1 negatively regulates expression of the hypertrophy-associated calmodulin and Mef2a genes.","date":"2009","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19188439","citation_count":334,"is_preprint":false},{"pmid":"12086621","id":"PMC_12086621","title":"Crystal structures of MAP kinase p38 complexed to the docking sites on its nuclear substrate MEF2A and activator MKK3b.","date":"2002","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/12086621","citation_count":271,"is_preprint":false},{"pmid":"12379849","id":"PMC_12379849","title":"Mitochondrial deficiency and cardiac sudden death in mice lacking the MEF2A transcription factor.","date":"2002","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/12379849","citation_count":270,"is_preprint":false},{"pmid":"14645853","id":"PMC_14645853","title":"Mutation of MEF2A in an inherited disorder with features of coronary artery disease.","date":"2003","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/14645853","citation_count":264,"is_preprint":false},{"pmid":"24591619","id":"PMC_24591619","title":"Requirement of MEF2A, C, and D for skeletal muscle regeneration.","date":"2014","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/24591619","citation_count":180,"is_preprint":false},{"pmid":"10748098","id":"PMC_10748098","title":"mHDA1/HDAC5 histone deacetylase interacts with and represses MEF2A transcriptional activity.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10748098","citation_count":175,"is_preprint":false},{"pmid":"21379568","id":"PMC_21379568","title":"The cardiac transcription network modulated by Gata4, Mef2a, Nkx2.5, Srf, histone modifications, and microRNAs.","date":"2011","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21379568","citation_count":170,"is_preprint":false},{"pmid":"23154418","id":"PMC_23154418","title":"MEF2A regulates the Gtl2-Dio3 microRNA mega-cluster to modulate WNT signaling in skeletal muscle regeneration.","date":"2012","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/23154418","citation_count":100,"is_preprint":false},{"pmid":"10748204","id":"PMC_10748204","title":"The MEF2A isoform is required for striated muscle-specific expression of the insulin-responsive GLUT4 glucose transporter.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10748204","citation_count":94,"is_preprint":false},{"pmid":"10373581","id":"PMC_10373581","title":"Post-translational control of the MEF2A transcriptional regulatory protein.","date":"1999","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/10373581","citation_count":91,"is_preprint":false},{"pmid":"10715212","id":"PMC_10715212","title":"Crystal structure of MEF2A core bound to DNA at 1.5 A resolution.","date":"2000","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10715212","citation_count":89,"is_preprint":false},{"pmid":"18647882","id":"PMC_18647882","title":"CaMK activation during exercise is required for histone hyperacetylation and MEF2A binding at the MEF2 site on the Glut4 gene.","date":"2008","source":"American journal of physiology. 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mutational analysis of p38–MEF2A docking interaction\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures solved at atomic resolution with mutational validation, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"12086621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Crystal structure of MEF2A core (residues 2–78) bound to DNA at 1.5 Å resolution revealed how the absence of amino acids N-terminal to the MADS-box contributes to DNA-binding properties and that the MEF2 domain adopts a conformation considerably different from SRF and MCM1.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure, foundational structural study\",\n      \"pmids\": [\"10715212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"NMR solution structure of the MEF2A–DNA complex showed that the MADS-box contacts both major and minor grooves, the MEF2S domain structure is entirely different from the SAM domain in SRF/MCM1, and critical protein–DNA contact differences explain the ~15° DNA bending by MEF2A versus ~70° by SRF/MCM1.\",\n      \"method\": \"NMR spectroscopy\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — solution NMR structure with detailed contact analysis, independent replication by crystal structure (PMID:10715212)\",\n      \"pmids\": [\"10835359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Crystal structure of the MADS-box/MEF2 domain of MEF2A bound to DNA showed that the MEF2 domain participates with the MADS-box in both dimerization and DNA binding as a single domain, and that the ligand-binding pocket (for cofactors such as HDACs/myocardin family) is preformed by intrinsic folding rather than induced by cofactor binding.\",\n      \"method\": \"X-ray crystallography; homology modeling; mutagenesis\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis validation, corroborated by prior structural studies\",\n      \"pmids\": [\"20132824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Crystal structure of an HDAC4–MEF2A–DNA complex revealed a 2:4:2 (HDAC4:MEF2A:DNA) dumbbell-shaped architecture in which two HDAC4 molecules dimerize via their glutamine-rich domain to bridge two MEF2A–DNA dimers; mutagenesis and luciferase assays confirmed that HDAC4 dimerization is required for its repression of MEF2A transcriptional activity.\",\n      \"method\": \"X-ray crystallography; biochemical mutagenesis assays; luciferase reporter assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus orthogonal mutagenesis and cell-based functional assays in a single study\",\n      \"pmids\": [\"38281192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Mutational analysis (removal of N-terminal residues plus K154E substitution) demonstrated that DNA-binding specificity of SRF can be converted to that of MEF2A/RSRFC4, identifying that residues immediately N-terminal to the MADS box and position 154 determine binding-site specificity via an indirect mechanism not involving direct base recognition.\",\n      \"method\": \"Site-directed mutagenesis; DNA-binding assays (EMSA); ternary complex formation assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution-type mutagenesis with multiple functional readouts in a single focused study\",\n      \"pmids\": [\"8095095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"p38 MAP kinase phosphorylates MEF2A on serine and threonine residues within its transactivation domain, causing decreased electrophoretic mobility and increased transcriptional activity; PKCδ and PKCε also enhance MEF2A transactivation, whereas ERK1/2 and JNK/SAPK do not.\",\n      \"method\": \"Transient transfection reporter assays; metabolic 32P-labeling; immunoprecipitation; phosphopeptide mapping; phosphoamino acid analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in-cell phosphorylation assay with peptide mapping, multiple orthogonal methods in one study\",\n      \"pmids\": [\"10373581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"HDAC5 interacts with MEF2A in vivo and in vitro and strongly represses its transcriptional activity; repression is independent of the HDAC5 deacetylase domain and instead mediated by the N-terminal non-deacetylase domain; the MADS-box/MEF2 domain of MEF2A interacts with a limited region in the N-terminal part of HDAC5.\",\n      \"method\": \"Co-immunoprecipitation (in vivo); in vitro binding assays; domain-mapping experiments; transcriptional reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus in vitro binding and reporter assays, multiple orthogonal methods\",\n      \"pmids\": [\"10748098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A 7-amino-acid deletion in MEF2A disrupts nuclear localization of MEF2A, reduces MEF2A-mediated transcription activation, and abolishes synergistic activation by MEF2A and GATA-1 through a dominant-negative mechanism; MEF2A protein is strongly expressed in the endothelium of coronary arteries.\",\n      \"method\": \"Functional luciferase reporter assays; subcellular localization studies; dominant-negative analysis\",\n      \"journal\": \"Science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional assays with multiple mechanistic readouts, single lab\",\n      \"pmids\": [\"14645853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MEF2A is sumoylated primarily at lysine K395 both in vitro and in vivo; the nuclear E3 ligase PIAS1 promotes this sumoylation; mutation K395R abolishes sumoylation and results in enhanced transcriptional activity of MEF2A.\",\n      \"method\": \"In vitro and in vivo SUMOylation assays; site-directed mutagenesis; transcriptional reporter assays\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution plus in-cell assays, mutagenesis validation, single lab\",\n      \"pmids\": [\"16563226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SENP2 is the de-SUMOylation enzyme for MEF2A; SENP2 knockdown or knockout increases detectable SUMOylated MEF2A; SENP2 accumulates in response to activity-dependent stimuli and thereby mediates activity-dependent MEF2A de-SUMOylation and transcriptional activation.\",\n      \"method\": \"shRNA screen; in vivo SUMOylation assays; SENP2 knockout embryos; transcriptional reporter assays\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA screen plus in vivo SUMOylation assays, single lab\",\n      \"pmids\": [\"23224591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"APC/C-Cdh1 interacts with and ubiquitinates SENP2 (recognizing a D-box motif) in the cytoplasm, targeting it for degradation; this controls MEF2A transcriptional activation in an activity-dependent manner, since activity-dependent stimuli prevent APC(Cdh1)-induced SENP2 ubiquitination, promote SENP2 nuclear accumulation, and cause MEF2A de-SUMOylation and acetylation.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assays; luciferase reporter assays; SUMOylation/acetylation assays\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus functional ubiquitination/SUMOylation assays, single lab\",\n      \"pmids\": [\"25483061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MEF2A-deficient mice exhibit pronounced right ventricular dilation, myofibrillar fragmentation, mitochondrial disorganization, activation of a fetal cardiac gene program, and sudden cardiac death; MEF2D transcriptional activity is paradoxically enhanced in mutant hearts, showing that MEF2D cannot compensate for MEF2A-specific functions in maintaining mitochondrial content and cytoarchitectural integrity.\",\n      \"method\": \"Mef2a knockout mouse; histology; electron microscopy; MEF2-dependent transgene reporter\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with multiple orthogonal phenotypic readouts, widely replicated concept\",\n      \"pmids\": [\"12379849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MEF2A forms a MEF2A–MEF2D heterodimer (with no detectable MEF2A homodimers or MEF2A–MEF2C dimers) in heart and skeletal muscle; this heterodimer is the species that binds the MEF2 site in the GLUT4 promoter; immunodepletion of MEF2A–MEF2D abolishes MEF2 site binding and addition of MEF2A to diabetic nuclear extracts restores it; MEF2A is specifically down-regulated in insulin-deficient diabetes without effect on MEF2D in muscle.\",\n      \"method\": \"Co-immunoprecipitation with isoform-specific antibodies; EMSA; immunodepletion assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with multiple orthogonal binding assays, single lab\",\n      \"pmids\": [\"10748204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The MEF2A 3′ UTR functions as a cis-acting translational repressor both in vivo and in vitro, with an internal conserved region responsible for inhibition; this repression is independent of mRNA steady-state levels and is relaxed during muscle cell differentiation.\",\n      \"method\": \"CAT reporter gene fusion assays in vivo; in vitro translation in rabbit reticulocyte lysates; RNase protection assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro reconstitution plus in-vivo reporter assays with orthogonal mRNA analysis, single lab\",\n      \"pmids\": [\"9111346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ERK5 uses a docking domain (phi_A-X-phi_B motif) in MEF2A to promote both in vitro phosphorylation and in vivo transcriptional activation of MEF2A; the specificity determinants for ERK5 at the MEF2A docking domain are similar to those for p38; the catalytic domain of ERK5 recognizes the docking domain.\",\n      \"method\": \"In vitro kinase assays; mutational analysis of MEF2A docking domain; in vivo transcriptional activation assays\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro phosphorylation plus in-vivo activation assays, mutagenesis, single lab\",\n      \"pmids\": [\"15132737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Sumoylated MEF2A acts as a transcriptional repressor to eliminate orphan presynaptic sites in neurons; knockdown of MEF2A in rat cerebellar cortex in vivo increases orphan presynaptic site density; sumoylated MEF2A directly represses the synaptotagmin 1 (Syt1) gene, and Syt1 repression mediates MEF2A-dependent elimination of orphan presynaptic sites, which promotes accumulation of presynaptic material at maturing boutons.\",\n      \"method\": \"In vivo knockdown (rat cerebellar cortex); direct target gene identification; reporter assays; neuronal culture experiments\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockdown with defined target gene and rescue experiments, single lab\",\n      \"pmids\": [\"23486945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MEF2A undergoes chaperone-mediated autophagy (CMA)-dependent degradation by lysosomes under basal conditions; mild oxidative stress enhances MEF2A degradation and activity, whereas excessive oxidative stress disrupts lysosomal integrity causing accumulation of non-functional MEF2A and production of an HDAC4 N-terminal cleavage product (HDAC4-NT) by lysosomal serine proteases, which acts as a MEF2 repressor.\",\n      \"method\": \"Lysosomal fractionation; CMA pathway inhibition; oxidative stress treatments; western blot; DNA-binding and transcriptional activity assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple subcellular fractionation and pathway inhibition experiments, single lab\",\n      \"pmids\": [\"24879151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MEF2A ubiquitination in dopaminergic neurons is isoform-specific (MEF2A but not MEF2C or MEF2D); ubiquitination occurs at the N-terminus, first detectable in the nuclear compartment then in the cytoplasm; ubiquitinated MEF2A has reduced DNA-binding and transcriptional activity; neurotoxins that cause proteasome pathway disruption lead to accumulation of ubiquitinated MEF2A and impaired neuronal viability.\",\n      \"method\": \"Ubiquitination assays in neuronal SN4741 cells; subcellular fractionation; DNA-binding activity assays; proteasome inhibitor treatments\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal assays in neuronal cells, single lab\",\n      \"pmids\": [\"22764880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"p300/CBP binds the N-terminal domain of both TR and MEF2A via the same C-terminal portion of p300; TR, MEF2A, and p300 form a ternary complex in vivo; p300/CBP modulates transactivation of the TR-RxR-MEF2A complex at a thyroid hormone response element; adenovirus E1A inhibits TR-RxR-MEF2A-p300 activation but not TR-RxR-MEF2A alone, indicating p300 recruits an inhibitor.\",\n      \"method\": \"GST pull-down; co-immunoprecipitation; domain mapping; CAT reporter assays in U2OS cells\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST pulldown plus co-IP plus reporter assays, single lab\",\n      \"pmids\": [\"12371907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PITX2a directly interacts with MEF2A (demonstrated by yeast two-hybrid and GST pull-down); coexpression of MEF2A and PITX2a/Pitx2c results in strong synergistic activation of the ANF promoter in a cell-type- and promoter-context-specific manner (LS8 cells but not NIH/3T3, CHO, or C2C12); synergism requires MEF2 binding sites and DNA binding by MEF2A.\",\n      \"method\": \"Yeast two-hybrid; GST pull-down; luciferase reporter assays; cell-type specificity analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus GST pulldown plus reporter assays, single lab\",\n      \"pmids\": [\"15466416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GLUT4 enhancer factor (GEF) dimerizes with hypophosphorylated MEF2A with increased affinity; MEF2A binding to its cognate site increases the DNA binding activity of GEF to Domain I of the GLUT4 promoter; HDAC5 interacts with GEF and specifically inhibits GLUT4 promoter activity.\",\n      \"method\": \"Co-immunoprecipitation; EMSA; luciferase reporter assays; domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus EMSA plus reporter assays, single lab\",\n      \"pmids\": [\"18216015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Myomaxin (a Xin-related protein) is a direct downstream transcriptional target of MEF2A; it is markedly down-regulated in Mef2a knockout hearts; myomaxin localizes to the Z-disc/costameric region and interacts with the sarcomeric Z-disc protein alpha-actinin-2.\",\n      \"method\": \"Mef2a knockout mouse; microarray expression analysis; co-immunoprecipitation (myomaxin–alpha-actinin-2); immunolocalization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout plus Co-IP plus localization, single lab\",\n      \"pmids\": [\"17046827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Myospryn is a direct downstream transcriptional target of MEF2A, identified by microarray in Mef2a knockout mice; myospryn localizes to the costamere and interacts with alpha-actinin-2.\",\n      \"method\": \"Mef2a knockout mouse; microarray expression analysis; co-immunoprecipitation (myospryn–alpha-actinin-2); immunolocalization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout plus Co-IP plus localization, single lab\",\n      \"pmids\": [\"16407236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEF2A directly regulates a cohort of costamere genes in cardiac muscle; acute knockdown of Mef2a in primary neonatal cardiomyocytes causes profound myofibril and focal adhesion malformations and adhesion-dependent programmed cell death, identifying a role for MEF2A in cardiomyocyte survival through regulation of costamere integrity.\",\n      \"method\": \"Mef2a knockout mouse; expression analysis; Mef2a siRNA knockdown in primary cardiomyocytes; immunofluorescence; apoptosis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout corroborated by acute knockdown with defined cellular phenotypes, single lab\",\n      \"pmids\": [\"21724844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MEF2A directly regulates the Gtl2-Dio3 miRNA mega-cluster; Gtl2-Dio3-encoded miRNAs repress secreted Frizzled-related proteins (sFRPs), inhibitors of WNT signaling; in Mef2a knockout regenerating muscle these miRNAs are downregulated, sFRP expression is upregulated, and WNT activity is attenuated; myogenic differentiation in MEF2A-deficient myoblasts is rescued by miR-410/miR-433 overexpression or recombinant WNT3A/WNT5A treatment.\",\n      \"method\": \"Mef2a knockout mouse; muscle regeneration assays; miRNA expression profiling; rescue with miRNA overexpression and recombinant WNTs\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout with mechanistic rescue experiments, single lab\",\n      \"pmids\": [\"23154418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MEF2A activates Xirp2 expression in response to angiotensin II by directly stimulating MEF2A transcriptional activity at the Xirp2 promoter; Xirp2 (an actin-binding protein) functions downstream of MEF2A to modulate Ang II-mediated pathological cardiac remodeling.\",\n      \"method\": \"Xirp2 promoter characterization; MEF2A binding assays; Xirp2 hypomorphic mouse with Ang II infusion\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter binding assays plus in vivo hypomorphic model, single lab\",\n      \"pmids\": [\"20093629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TGF-β transcriptionally induces MMP-10 through MEF2A; TGF-β promotes proteasome-dependent degradation of class IIa HDACs, resulting in increased histone acetylation around the MEF2 site on the MMP-10 promoter and increased MEF2A binding; knockdown of MEF2A reduces and overexpression increases TGF-β-induced MMP-10 expression.\",\n      \"method\": \"MEF2A knockdown/overexpression; ChIP assay; luciferase reporter assays; HDAC knockdown/overexpression\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus knockdown/overexpression plus reporter assays, single lab\",\n      \"pmids\": [\"19935709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CaMK II activation during exercise is required for histone H3 hyperacetylation at the GLUT4 MEF2 site and for increased MEF2A binding to this site in vivo; inhibition of CaMK II with KN93 prior to exercise abolishes these increases and attenuates exercise-induced GLUT4 mRNA and protein increases.\",\n      \"method\": \"In vivo exercise model; chromatin immunoprecipitation (ChIP); Western blot; RT-PCR; CaMK II inhibitor (KN93)\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP in vivo with pharmacological inhibition, single lab\",\n      \"pmids\": [\"18647882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Exercise increases MEF2A binding to the GLUT4 promoter in vivo; CaMK signaling mediates MEF2A/DNA associations, as constitutively active CaMK IV increases MEF2A binding by ~75% compared to dominant-negative CaMK IV in C2C12 myotubes.\",\n      \"method\": \"In vivo exercise model; ChIP assay; constitutively active and dominant-negative CaMK IV overexpression\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo ChIP corroborated by CaMK gain/loss-of-function in cell culture, single lab\",\n      \"pmids\": [\"16985263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MEF2A is present on the c-Jun promoter in macrophages; MEF2A/MEF2D heterodimers strongly interact with HDAC1 (and to a lesser extent HDAC7) in macrophages; endogenous p300 associates with MEF2A only in differentiated macrophages (not undifferentiated cells or monocytes), indicating a switch from repressor to activator complex during differentiation.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP); co-immunoprecipitation; trichostatin A treatment\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus reciprocal Co-IP, single lab\",\n      \"pmids\": [\"20590529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HDAC5 interacts with MEF2A and suppresses MEF2A binding to the Smad7 promoter, resulting in Smad7 promoter activity repression; luciferase reporter and ChIP-qPCR assays confirmed this interaction; HDAC5 deficiency increases Smad7 expression, which in turn decreases TGF-β1-induced Smad2/3 phosphorylation.\",\n      \"method\": \"Luciferase reporter assays; ChIP-qPCR; HDAC5 knockdown; in vivo scar model\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus reporter assays plus in vitro/in vivo knockdown, single lab\",\n      \"pmids\": [\"36263180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"MEF2A nuclear translocation is regulated by p38 and calcineurin in a biphasic, time-dependent manner in response to static stretch; stretch produces increased p38 phosphorylation preceding MEF2A nuclear translocation; inhibition of p38 (SB-203580) or calcineurin (cyclosporine A) blocks MEF2A phosphorylation and nuclear translocation.\",\n      \"method\": \"Pharmacological inhibition (SB-203580, cyclosporine A); Western blot; subcellular fractionation/nuclear translocation assays; static stretch application in C2C12 myocytes\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with multiple readouts, single lab\",\n      \"pmids\": [\"15483225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEF2A directly binds MEF2A-binding sites in the promoter region of Xirp2 (Myomaxin/Myospryn network) and a cohort of costamere genes, establishing MEF2A as a direct transcriptional regulator of a costamere gene program in cardiac muscle.\",\n      \"method\": \"ChIP assay; Mef2a knockout mouse; luciferase reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP in vivo plus reporter assays, single lab\",\n      \"pmids\": [\"21724844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MEF2A binds the Cpt1b promoter in skeletal muscle; exercise training elevates MEF2A binding and reduces HDAC5 binding at the Cpt1b promoter; exercise induces MEF2A hyperacetylation which correlates with enhanced DNA-binding; HDAC5 and HDAC3 binding to MEF2A decreases with exercise; MEF2A overexpression increases Cpt1b mRNA expression suppressed by HDAC5.\",\n      \"method\": \"ChIP assay; co-immunoprecipitation; MEF2A overexpression; luciferase reporter assays; exercise treadmill model\",\n      \"journal\": \"Acta physiologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus Co-IP plus reporter assays in exercise model, single lab\",\n      \"pmids\": [\"25213552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEF2A directly binds the promoter region of ZEB2 and CTNNB1 to initiate their transcription in colorectal cancer cells, promoting EMT and WNT/β-catenin signaling; demonstrated by direct promoter binding assays.\",\n      \"method\": \"ChIP assay; luciferase reporter assays; MEF2A overexpression/knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus reporter assays plus gain/loss-of-function, single lab\",\n      \"pmids\": [\"33863999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AMPKα2 regulates MEF2A nuclear translocation and MEF2A binding to the Glut4 promoter; overexpression of AMPKα2 increases nuclear MEF2A content and promoter-bound MEF2A, while knockout attenuates these effects; however, AMPKα2 does not regulate HDAC5 nuclear export after 28 days of training.\",\n      \"method\": \"AMPKα2 OE and KO mice; treadmill training; ChIP assay; Western blot; co-immunoprecipitation\",\n      \"journal\": \"Medicine and science in sports and exercise\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic OE and KO mice with ChIP and Co-IP, single lab\",\n      \"pmids\": [\"21233771\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEF2A is required for Group I mGluR-mediated GluA2 AMPA receptor internalization in neurons; knockdown of MEF2A specifically abolishes mGluR-dependent GluA2 internalisation without affecting basal AMPAR expression or trafficking; this process is independent of Arc/Arg3.1 expression.\",\n      \"method\": \"MEF2A knockdown in primary neuronal culture; GluA2 trafficking assays; Arc/Arg3.1 expression analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with defined trafficking readout and negative control for Arc, single lab\",\n      \"pmids\": [\"29588465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MEF2A/D-dependent transcription (specifically MEF2A/D) is required for synapse silencing (depression of AMPAR transmission) induced by 1-hour theta-frequency burst firing in CA1 neurons; MEF2A/D-induced Arc expression contributes to synapse silencing and elimination; more prolonged (24-hr) firing-induced spine elimination did not require MEF2A/D.\",\n      \"method\": \"Optogenetics; MEF2A/D loss-of-function; Arc expression measurement; electrophysiology (AMPAR and NMDAR EPSCs); de novo transcription inhibition\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — optogenetic manipulation plus loss-of-function with electrophysiological readouts, single lab\",\n      \"pmids\": [\"28901289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEF2A directly binds the Calpain 3 (Capn3) promoter and positively regulates Capn3 expression; demonstrated by luciferase reporter assay, EMSA, and ChIP in rat denervated gastrocnemius muscle; MEF2A siRNA knockdown in L6 myoblasts reduces Capn3 protein.\",\n      \"method\": \"Luciferase reporter assay; EMSA; ChIP; siRNA knockdown; Western blot\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus EMSA plus reporter assays plus siRNA, single lab\",\n      \"pmids\": [\"29783071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MEF2A loss-of-function variant (p.Gly240*) abolishes transactivation on target genes MYH6 and FHL2 and nullifies synergistic activation between MEF2A and GATA4, establishing MEF2A loss-of-function as predisposing to dilated cardiomyopathy.\",\n      \"method\": \"Whole-exome sequencing; Sanger sequencing; dual-luciferase assay; functional characterization of variant\",\n      \"journal\": \"Clinical chemistry and laboratory medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct luciferase functional assays with defined target genes and co-factor synergy, single lab\",\n      \"pmids\": [\"33554560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MEF2A immunoprecipitation followed by RNA isolation confirmed direct binding of MEF2A protein to pri-miR-494 RNA, suggesting a novel post-transcriptional function of MEF2A as an RNA-binding protein regulating processing of 14q32 microRNAs miR-329 and miR-494.\",\n      \"method\": \"MEF2A immunoprecipitation followed by RNA isolation and RT-qPCR; in vivo hind-limb ischemia model with MEF2A gene silencing\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single RIP experiment in one lab; novel and unexpected function requiring further validation\",\n      \"pmids\": [\"28624225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEF2A loss leads to R-loop accumulation and activates the DDX41–cGAS–STING interferon pathway; MEF2A-deficient cells show ATR kinase activation, which is necessary for STING activation; MEF2A thus sustains transcriptional homeostasis and suppresses unscheduled interferon responses.\",\n      \"method\": \"MEF2A loss-of-function; R-loop detection assays; ATR inhibition experiments; STING pathway activation measurements; interferon reporter assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple pathway readouts and epistasis (ATR inhibition), single lab\",\n      \"pmids\": [\"37467105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MEF2A transcriptional activation in response to oxytocin (OT) involves reduced phosphorylation of MEF2A at Serine 408, under control of the OTR-coupled MAPK (MEK1/2) pathway; MEK1/2 inhibition (U0126) blocks MEF2A activation; siRNA-mediated MEF2A knockdown prevents OT-induced neurite retraction in hypothalamic neurons.\",\n      \"method\": \"Pharmacological inhibition (U0126); siRNA knockdown of MEF2A; Western blot for pSer408-MEF2A; neurite morphology measurements\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA plus pharmacological inhibition with defined morphological readout, single lab\",\n      \"pmids\": [\"29928931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEF2A and MEF2D function as scaffold proteins interacting with HDAC1 (in undifferentiated THP-1 cells) or p300 (in TPA-differentiated THP-1 cells) at the SOD3 promoter region, mediating switches between repression and activation of SOD3 gene expression.\",\n      \"method\": \"ChIP assay; co-immunoprecipitation; MEF2A/MEF2D knockdown; Western blot\",\n      \"journal\": \"Free radical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus Co-IP plus knockdown with defined gene expression readout, single lab\",\n      \"pmids\": [\"29842805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MEF2A directly activates transcription of PGC1α and inhibits transcription of KEAP1, thereby promoting mitochondrial biogenesis and activating the KEAP1/NRF2 pathway to modulate reactive oxygen species levels and confer cisplatin resistance in gastric cancer cells.\",\n      \"method\": \"MEF2A overexpression/knockdown; luciferase reporter assays for PGC1α and KEAP1 promoters; in vitro and in vivo cisplatin sensitivity assays\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assays plus gain/loss-of-function in vitro and in vivo, single lab\",\n      \"pmids\": [\"39237047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MEF2A directly modulates CYP7A1 transcription as confirmed by dual luciferase reporter assays; MEF2A knockdown in HepG2 cells leads to CYP7A1 downregulation and lipid accumulation, while overexpression reverses these effects; reduced MEF2A expression in offspring of HFD-fed dams is attributable to DNA hypermethylation in the MEF2A promoter region.\",\n      \"method\": \"Dual luciferase reporter assays; MEF2A knockdown/overexpression; MassARRAY EpiTYPER methylation analysis; 5-azacitidine treatment\",\n      \"journal\": \"Cellular & molecular biology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct reporter assay plus gain/loss-of-function plus methylation analysis, single lab\",\n      \"pmids\": [\"39695937\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MEF2A is a MADS-box/MEF2-domain transcription factor that binds A+T-rich DNA as homodimers or heterodimers (predominantly MEF2A–MEF2D in muscle), is activated by p38 MAPK and ERK5 phosphorylation at its transactivation domain and by CaMK-dependent mechanisms, and is repressed by class IIa HDACs (HDAC4/5) that bind its MEF2 domain and by SUMO-1 modification at K395 (with PIAS1 as E3 ligase and SENP2 as the de-SUMOylation enzyme); it directly regulates programs of muscle-specific structural genes (costamere, GLUT4, Cpt1b, myomaxin, myospryn), controls mitochondrial biogenesis and cytoarchitectural integrity in the postnatal heart, drives skeletal muscle regeneration via the Gtl2-Dio3 miRNA–WNT signaling axis, and in neurons governs activity-dependent synapse elimination, AMPAR trafficking, and interferon threshold via transcriptional homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MEF2A is a MADS-box/MEF2-domain transcription factor that binds A+T-rich DNA and orchestrates muscle, cardiac, and neuronal gene programs through combinatorial cofactor recruitment and signal-dependent post-translational control [#3, #12]. Its core MADS-box plus MEF2 domain functions as a single integrated module mediating both dimerization and DNA binding, contacting major and minor grooves to bend DNA ~15° and presenting a preformed cofactor-binding pocket; residues N-terminal to the MADS-box and position 154 dictate the binding-site specificity that distinguishes MEF2A from SRF [#2, #3, #5]. In muscle MEF2A predominantly acts as a MEF2A–MEF2D heterodimer, the species that occupies sites such as the GLUT4 promoter [#13]. MEF2A activity is gated by an opposing set of inputs: p38 MAPK and ERK5 dock on its transactivation domain and phosphorylate it to increase activity, while class IIa HDACs (HDAC4/HDAC5) bind the MADS-box/MEF2 domain to repress it—HDAC4 dimerizing via its glutamine-rich region to bridge two MEF2A–DNA complexes—and CaMK signaling promotes MEF2A nuclear translocation and promoter binding [#0, #4, #6, #7, #15, #29]. A SUMOylation switch at K395, installed by PIAS1 and reversed by SENP2 (whose stability is in turn controlled by APC/C-Cdh1), converts MEF2A between repressive and active states in an activity-dependent manner [#9, #10, #11]. Functionally, MEF2A directly drives a costamere/Z-disc structural gene program (myomaxin, myospryn, Xirp2) required for cardiomyocyte cytoarchitecture and survival, and its loss in mice causes mitochondrial disorganization, myofibrillar fragmentation, and sudden cardiac death that MEF2D cannot rescue [#12, #22, #23, #24, #33]. In neurons, SUMOylated MEF2A represses synaptotagmin-1 to eliminate orphan presynaptic sites and MEF2A/D-dependent transcription drives activity-dependent synapse silencing and AMPAR trafficking [#16, #37, #38]. A loss-of-function variant (p.Gly240*) that abolishes MYH6/FHL2 transactivation and MEF2A–GATA4 synergy links MEF2A to dilated cardiomyopathy [#40]. MEF2A also sustains genome/transcriptional homeostasis, with its loss provoking R-loop accumulation and DDX41–cGAS–STING interferon activation [#42].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Before MEF2A's DNA-recognition logic was known, it was unclear how a MADS-box factor achieves binding specificity distinct from SRF; swapping defined residues established that specificity is encoded by sequences N-terminal to the MADS-box and position 154 through an indirect mechanism.\",\n      \"evidence\": \"Site-directed mutagenesis converting SRF specificity to MEF2A, with EMSA and ternary complex assays\",\n      \"pmids\": [\"8095095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the atomic basis of the indirect specificity\", \"Did not address dimer partner contributions to site selection\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"To explain how MEF2A engages DNA differently from related MADS-box proteins, structural studies showed the MEF2 domain adopts a fold distinct from SRF/MCM1, contacts both grooves, and bends DNA only ~15°.\",\n      \"evidence\": \"X-ray crystallography (1.5 Å) and NMR solution structure of MEF2A–DNA complexes\",\n      \"pmids\": [\"10715212\", \"10835359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture cofactor-bound states\", \"Limited to the DNA-binding core, not full-length protein\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"It was unknown which MEF2 species binds physiological promoters in muscle; isoform-specific antibody work showed MEF2A acts as a MEF2A–MEF2D heterodimer that occupies the GLUT4 promoter and is selectively lost in diabetic muscle.\",\n      \"evidence\": \"Co-IP with isoform-specific antibodies, EMSA, and immunodepletion from heart/muscle extracts\",\n      \"pmids\": [\"10748204\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish heterodimer composition across non-muscle tissues\", \"Mechanism of diabetes-specific MEF2A downregulation unresolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"To define activating signals, it was shown that p38 MAPK (and PKCδ/ε) but not ERK1/2 or JNK phosphorylates the MEF2A transactivation domain to increase its transcriptional output.\",\n      \"evidence\": \"Reporter assays, 32P metabolic labeling, phosphopeptide mapping\",\n      \"pmids\": [\"10373581\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map all phospho-sites to downstream gene programs\", \"In vivo relevance of PKC inputs untested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The structural basis of MEF2A as a kinase substrate was resolved by showing p38 docks MEF2A and its activator MKK3b at the same C-terminal site outside the active site, coupling docking to active-site rearrangement.\",\n      \"evidence\": \"Crystal structures of p38–MEF2A and p38–MKK3b docking peptides with mutational analysis\",\n      \"pmids\": [\"12086621\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address how docking specificity is shared with ERK5\", \"Full-length kinase–substrate complex not solved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"A second MAPK input was defined: ERK5 uses a phi_A-X-phi_B docking motif in MEF2A—similar to p38 determinants—to phosphorylate and activate it.\",\n      \"evidence\": \"In vitro kinase assays and docking-domain mutagenesis with in vivo activation readouts\",\n      \"pmids\": [\"15132737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Target gene specificity of ERK5 versus p38 signaling unresolved\", \"Structural docking model not directly determined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The repressive arm of MEF2A control was identified: HDAC5 binds the MADS-box/MEF2 domain via its N-terminal non-deacetylase region to repress activity independently of catalysis.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro binding, domain mapping, reporter assays\",\n      \"pmids\": [\"10748098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the stoichiometry of the repressive complex\", \"Signals releasing HDAC5 not addressed here\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Structural work clarified that the MADS-box/MEF2 domain folds the cofactor pocket intrinsically and acts as one DNA-binding/dimerization unit, explaining how HDAC and myocardin-family cofactors share a preformed binding surface.\",\n      \"evidence\": \"Crystal structure of the MADS-box/MEF2 domain on DNA with homology modeling and mutagenesis\",\n      \"pmids\": [\"20132824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture an actual cofactor in the pocket\", \"Competition between activators and repressors not structurally resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The architecture of HDAC-mediated repression was solved, showing two HDAC4 molecules dimerize through their glutamine-rich domain to bridge two MEF2A–DNA dimers, and that this dimerization is required for repression.\",\n      \"evidence\": \"Crystal structure of HDAC4–MEF2A–DNA (2:4:2) with mutagenesis and luciferase assays\",\n      \"pmids\": [\"38281192\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo prevalence of the dumbbell complex unquantified\", \"Whether HDAC5 adopts the same architecture not shown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"A SUMO-based off-switch was identified: MEF2A is SUMOylated at K395 by PIAS1, and the K395R mutant has enhanced transcriptional activity.\",\n      \"evidence\": \"In vitro and in vivo SUMOylation assays, mutagenesis, reporter assays\",\n      \"pmids\": [\"16563226\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not identify the de-SUMOylation enzyme\", \"Gene-specific consequences of K395 SUMOylation not mapped\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The reversal of the SUMO switch was assigned to SENP2, which de-SUMOylates MEF2A and accumulates after activity-dependent stimuli to drive activation.\",\n      \"evidence\": \"shRNA screen, in vivo SUMOylation assays, SENP2 knockout embryos, reporter assays\",\n      \"pmids\": [\"23224591\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How activity stabilizes SENP2 was not yet explained\", \"Direct neuronal target genes not enumerated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The upstream control of SENP2 was traced to APC/C-Cdh1, which ubiquitinates SENP2 via a D-box; activity-dependent signals block this degradation, allowing nuclear SENP2 to de-SUMOylate and de-repress MEF2A.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, reporter and SUMOylation/acetylation assays\",\n      \"pmids\": [\"25483061\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The signal coupling activity to APC/C inhibition not defined\", \"Single-lab pathway without independent confirmation\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The in vivo physiological requirement for MEF2A was established by knockout mice showing right ventricular dilation, mitochondrial disorganization, myofibrillar fragmentation, and sudden death not rescued by MEF2D.\",\n      \"evidence\": \"Mef2a knockout mouse with histology, EM, and MEF2-dependent transgene reporter\",\n      \"pmids\": [\"12379849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the direct target genes responsible for the phenotype\", \"Basis of MEF2D non-redundancy not molecularly defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Direct cardiac structural targets were identified—myomaxin and myospryn—both downregulated in Mef2a-null hearts and localizing to the Z-disc/costamere via alpha-actinin-2.\",\n      \"evidence\": \"Mef2a knockout microarray, Co-IP with alpha-actinin-2, immunolocalization\",\n      \"pmids\": [\"17046827\", \"16407236\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct promoter occupancy not shown in these reports\", \"Functional contribution of each target to phenotype untested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"MEF2A was shown to directly bind a cohort of costamere gene promoters, and acute knockdown caused myofibril/focal-adhesion malformations and adhesion-dependent cell death, defining a survival role through costamere integrity.\",\n      \"evidence\": \"ChIP, Mef2a knockout, siRNA in primary cardiomyocytes, immunofluorescence, apoptosis assays\",\n      \"pmids\": [\"21724844\", \"33863999\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which individual costamere targets are essential for survival not isolated\", \"Mechanism linking costamere loss to apoptosis incomplete\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"A regeneration mechanism was defined whereby MEF2A drives the Gtl2-Dio3 miRNA cluster that represses sFRPs to sustain WNT signaling, with myogenic defects rescued by miR-410/433 or recombinant WNTs.\",\n      \"evidence\": \"Mef2a knockout muscle regeneration, miRNA profiling, miRNA and WNT rescue\",\n      \"pmids\": [\"23154418\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct MEF2A occupancy at the Gtl2-Dio3 locus quantification limited\", \"Generalizability beyond regeneration context untested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"In neurons, SUMOylated MEF2A was shown to function as a repressor of synaptotagmin-1 to eliminate orphan presynaptic sites, linking the SUMO switch to synaptic refinement.\",\n      \"evidence\": \"In vivo knockdown in rat cerebellar cortex, target gene identification, reporter assays\",\n      \"pmids\": [\"23486945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full repressive cofactor complex on Syt1 not defined\", \"Single-lab in vivo result\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"MEF2A's role in postsynaptic plasticity was extended by showing MEF2A is required for Group I mGluR-mediated GluA2 AMPAR internalization, independent of Arc, and MEF2A/D transcription drives activity-dependent synapse silencing.\",\n      \"evidence\": \"siRNA/loss-of-function with GluA2 trafficking and electrophysiology, optogenetics\",\n      \"pmids\": [\"29588465\", \"28901289\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The MEF2A target genes mediating GluA2 internalization not identified\", \"Distinction of MEF2A versus MEF2D contributions incomplete\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A human disease link was established: the MEF2A p.Gly240* loss-of-function variant abolishes MYH6/FHL2 transactivation and MEF2A–GATA4 synergy, predisposing to dilated cardiomyopathy.\",\n      \"evidence\": \"Whole-exome/Sanger sequencing with dual-luciferase functional characterization\",\n      \"pmids\": [\"33554560\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality in a model organism not demonstrated\", \"Penetrance and mechanism in patient hearts not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A genome-homeostasis function was revealed: MEF2A loss causes R-loop accumulation and ATR-dependent activation of the DDX41–cGAS–STING interferon pathway, positioning MEF2A as a suppressor of unscheduled interferon responses.\",\n      \"evidence\": \"Loss-of-function with R-loop detection, ATR-inhibition epistasis, STING/interferon reporters\",\n      \"pmids\": [\"37467105\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether R-loops arise from direct MEF2A transcriptional targets unclear\", \"Tissue contexts for this homeostatic role untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the competing post-translational inputs (MAPK phosphorylation, SUMOylation, acetylation, ubiquitination, CMA-mediated turnover) are integrated at specific promoters to select repressor versus activator complexes in a given tissue remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of the modification code\", \"Cell-type-specific cofactor selection rules undefined\", \"Direct genome-wide MEF2A target maps not integrated with modification states\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 6, 12, 16, 33, 40, 45]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [2, 3, 5, 13, 33, 39]},\n      {\"term_id\": \"GO:0046983\", \"supporting_discovery_ids\": [3, 13]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [41]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [8, 32, 36]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 6, 12, 33]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 15, 28, 32]},\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [12, 22, 23, 24]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [16, 37, 38]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [12, 25]}\n    ],\n    \"complexes\": [\n      \"MEF2A–MEF2D heterodimer\",\n      \"HDAC4–MEF2A–DNA repressive complex\",\n      \"TR–RxR–MEF2A–p300 complex\"\n    ],\n    \"partners\": [\n      \"MEF2D\",\n      \"HDAC5\",\n      \"HDAC4\",\n      \"HDAC1\",\n      \"p300\",\n      \"GATA4\",\n      \"PITX2\",\n      \"SENP2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}