{"gene":"UNC13A","run_date":"2026-04-28T21:43:01","timeline":{"discoveries":[{"year":1999,"finding":"Munc13-1 (UNC13A) is essential for synaptic vesicle maturation/priming to fusion competence at glutamatergic synapses; knockout neurons form ultrastructurally normal synapses but vesicle cycle is arrested at the maturation step, blocking release by action potentials, calcium ionophores, and hypertonic sucrose, while alpha-latrotoxin-evoked release is preserved, indicating Munc13-1 acts specifically at the priming step.","method":"Munc13-1 knockout mouse neurons; electrophysiology; electron microscopy","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1–2 — clean KO with specific phenotypic readout, multiple stimulation paradigms tested, foundational paper with >600 citations","pmids":["10440375"],"is_preprint":false},{"year":1998,"finding":"Munc13-1 is a presynaptic high-affinity phorbol ester and diacylglycerol receptor that associates with the plasma membrane upon phorbol ester binding and enhances neurotransmitter release when overexpressed presynaptically, acting in parallel with protein kinase C in the DAG second messenger pathway.","method":"Phorbol ester binding assays; overexpression in Xenopus neuromuscular junction; electrophysiology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 — direct ligand binding assay plus functional overexpression rescue, replicated across labs","pmids":["9697857"],"is_preprint":false},{"year":1997,"finding":"Munc13-1 directly interacts with the N-terminal coiled-coil domain of syntaxin via its C-terminus, and through this interaction binds to a subpopulation of the exocytotic SNARE core complex (syntaxin/SNAP-25/synaptobrevin), implicating Munc13-1 in modulating SNARE complex formation for vesicle exocytosis.","method":"Three independent biochemical binding assays (pulldown, co-immunoprecipitation, blot overlay); syntaxin binding domain mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — three orthogonal binding methods in single study, foundational interaction paper","pmids":["8999968"],"is_preprint":false},{"year":2001,"finding":"Munc13-1 and RIM1 interact functionally at the active zone; disruption of the Munc13-1/RIM1 interaction causes loss of fusion-competent synaptic vesicles (phenocopying Munc13-1 deficiency), with RIM1 binding and vesicle priming mediated by two distinct structural modules of Munc13-1.","method":"Biochemical interaction assays; electrophysiology in cultured neurons; domain deletion analysis","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — reciprocal functional and biochemical data, specific domain mapping, >300 citations","pmids":["11343654"],"is_preprint":false},{"year":2006,"finding":"Crystal structures of the Munc13-1 C2A domain homodimer (1.44 Å) and Munc13-1 C2A/RIM zinc-finger heterodimer (1.78 Å) reveal that the C2A domain can homodimerize via a four-stranded concave beta-sandwich, and that homodimerization competes with RIM heterodimerization, establishing a structural switch relevant to vesicle priming and presynaptic plasticity.","method":"X-ray crystallography guided by NMR spectroscopy; structural validation of competing interactions","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structures at near-atomic resolution combined with NMR, mechanistically validated","pmids":["16732694"],"is_preprint":false},{"year":2005,"finding":"The minimal Munc13-1 domain required for priming activity is the C-terminal region (residues 1100–1735) containing both Munc13-homology domains and the C-terminal C2 domain; priming requires interaction with Syntaxin 1, as point mutants unable to bind Syntaxin 1 cannot prime chromaffin granules.","method":"Deletion construct electrophysiology gain-of-function assay in chromaffin cells; point mutagenesis","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1–2 — systematic deletion mapping combined with mutagenesis and functional electrophysiology","pmids":["16271475"],"is_preprint":false},{"year":2005,"finding":"NMR structure of the Munc13-1 C1 domain reveals that a conserved tryptophan (Trp-22/Trp-588 in full-length) occludes the diacylglycerol/phorbol ester binding site—unlike PKC C1 domains—requiring a conformational change for ligand binding, explaining Munc13-1's lower DAG affinity compared to PKC.","method":"NMR structure determination; comparison with PKC C1 domain structures","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — NMR structure with mechanistic interpretation of ligand binding occlusion","pmids":["15667202"],"is_preprint":false},{"year":2007,"finding":"Activation of the Munc13-1 C1 domain by phorbol ester (PDBu) increases the vesicular release rate without affecting readily releasable vesicle pool size, mechanistically lowering the energy barrier for vesicle fusion; the C1 domain mutant H567K is a gain-of-function that constitutively mimics the PDBu-activated state.","method":"Electrophysiology (osmotic release, Ca2+-triggered and spontaneous release assays); knockin mice expressing Munc13-1(H567K)","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple electrophysiological readouts in knockin mice plus pharmacological dissection","pmids":["17267576"],"is_preprint":false},{"year":2002,"finding":"Munc13-1 forms a ternary complex with CAST and RIM1 at the cytomatrix of the active zone; CAST directly binds RIM1 and indirectly binds Munc13-1 through RIM1, and Bassoon associates with this complex, establishing a protein interaction network at the active zone.","method":"Co-immunoprecipitation; direct binding assays; immunolocalization","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 3 — direct binding and co-IP demonstrated for complex components","pmids":["12163476"],"is_preprint":false},{"year":2006,"finding":"Active zone recruitment of Munc13-1 and ubMunc13-2 is regulated by their binding to RIM1α; a single I121N point mutation in Munc13-1 abolishes RIM1α binding and prevents efficient synaptic recruitment; Munc13-1 levels are decreased in RIM1α-deficient brain and Munc13-1 is not properly enriched at active zones of mossy fiber terminals when RIM1α is absent.","method":"Point mutagenesis; in vitro binding assays; RIM1α knockout mice; immunohistochemistry; quantitative Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — mutagenesis + knockout mice + localization with functional consequence, multiple orthogonal methods","pmids":["16704978"],"is_preprint":false},{"year":2009,"finding":"Domains of five active zone proteins (RIM1, Bassoon, CAST1/ELKS2, Aczonin/Piccolo, and Bassoon CC3) all converge on the N-terminal region of Munc13-1, establishing Munc13-1's N-terminus as a hub of protein–protein interactions at the active zone; expression of Aczonin-CC3 in neurons suppresses vesicle turnover.","method":"Yeast two-hybrid; pulldown assays; co-IP; expression of GFP fusion in neurons with functional readout","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple binding partners mapped to same domain, with partial functional follow-up","pmids":["19812333"],"is_preprint":false},{"year":2013,"finding":"Munc13-1 is a major presynaptic target of Ca2+–calmodulin signaling; knockin mice expressing Ca2+–calmodulin-insensitive Munc13-1(W464R) show slower synaptic vesicle replenishment, aberrant short-term depression, and reduced recovery after high-frequency stimulation, establishing Ca2+–calmodulin–Munc13-1 signaling as a key determinant of short-term synaptic plasticity.","method":"Knockin mouse electrophysiology at calyx of Held; Ca2+-calmodulin binding-deficient point mutation","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockin with specific point mutation and defined electrophysiological phenotype","pmids":["23770256"],"is_preprint":false},{"year":2017,"finding":"Munc13-1 molecules form multiple discrete supramolecular self-assemblies in the presynaptic terminal that serve as independent vesicular release sites by recruiting syntaxin-1; multiplicity of these assemblies controls presynaptic synaptic weight in glutamatergic synapses.","method":"Single-synapse glutamate imaging; super-resolution (STED/STORM) microscopy of presynaptic proteins","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple imaging modalities combined with functional release measurements","pmids":["29230050"],"is_preprint":false},{"year":2017,"finding":"A de novo Pro814Leu variant in UNC13A causes a dominant gain-of-function characterized by increased synaptic vesicle fusion propensity, increased initial release probability, and abnormal short-term plasticity, leading to a dyskinetic movement disorder in a human patient.","method":"Whole-exome sequencing; electrophysiology in murine neuronal cultures; functional analysis in C. elegans","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — human variant characterised by electrophysiology in two model systems with defined molecular mechanism","pmids":["28192369"],"is_preprint":false},{"year":2019,"finding":"Munc13-1 bridges the synaptic vesicle and plasma membranes through opposite ends of its elongated C1C2BMUNC2C structure; mutations in the C2C domain membrane-binding sites disrupt liposome bridging and fusion in vitro and abolish synaptic vesicle docking, priming, and Ca2+-triggered release in mouse neurons, with a single residue substitution nearly completely abrogating release.","method":"In vitro liposome fusion/bridging assays; site-directed mutagenesis; electrophysiology in mouse neurons","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in vitro + mutagenesis + neuronal electrophysiology, multiple orthogonal methods","pmids":["30816091"],"is_preprint":false},{"year":2019,"finding":"The MUN domain of Munc13-1 stabilizes the Munc18-1/syntaxin-1/VAMP2 template complex by ~2.1 kBT, enhancing SNAP-25 binding and subsequent full SNARE assembly; Munc13-1 and Munc18-1 cooperatively chaperone SNARE folding through a tetrameric complex.","method":"Single-molecule force spectroscopy; mutational analysis; in vitro SNARE assembly assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — single-molecule reconstitution with mutagenesis and quantitative energetic measurements","pmids":["31888993"],"is_preprint":false},{"year":2006,"finding":"FRAP experiments in Munc13-1-EYFP knockin mice show that Munc13-1 is rapidly and continuously exchanged at active zones (tau1 ~3 min; tau2 ~80 min), demonstrating that presynaptic active zones are highly dynamic; exchange kinetics are reduced by chronic suppression of spontaneous activity but not by proteasome inhibitors or acute stimulation.","method":"FRAP in knockin mice expressing endogenous Munc13-1-EYFP; live imaging","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — endogenous knockin FRAP with pharmacological manipulations and activity perturbations","pmids":["17167095"],"is_preprint":false},{"year":2003,"finding":"Munc13-1 is present in pancreatic islet beta cells and regulates insulin granule priming; overexpressed Munc13-1 translocates to plasma membrane in a diacylglycerol-dependent manner and greatly amplifies insulin exocytosis, an effect abolished by the DAG binding-deficient H567K mutant.","method":"Patch-clamp capacitance measurements; radioimmunoassay; GFP-fusion overexpression with DAG binding-deficient mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — electrophysiology plus mutant dissection plus biochemical assay","pmids":["12871971"],"is_preprint":false},{"year":2006,"finding":"Munc13-1 heterozygous knockout mice exhibit reduced glucose-stimulated insulin secretion and abnormal glucose tolerance due to a primary islet beta-cell secretory defect involving granule priming deficits; DAG binding-deficient Munc13-1(H567K) knockin shows milder effects, confirming DAG-dependent priming role.","method":"Heterozygous knockout and knockin mice; glucose tolerance tests; patch-clamp capacitance measurements in beta cells","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockout/knockin with defined cellular electrophysiological phenotype","pmids":["16644700"],"is_preprint":false},{"year":2006,"finding":"Munc13-1 is required for the second phase of sustained insulin release from pancreatic beta cells; Munc13-1 knockout reduces sustained release upon prolonged stimulation, and this involves DAG signaling since it is also reduced in H567K DAG-binding-deficient knockin mice.","method":"Munc13-1 knockout and knockin mice; patch-clamp exocytosis measurements in primary beta cells","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 — KO and knockin with specific electrophysiological phenotype","pmids":["16697276"],"is_preprint":false},{"year":2011,"finding":"Munc13-1 is required for presynaptic long-term potentiation (LTP) at hippocampal mossy fiber synapses, and the interaction between RIM1α and Munc13-1 (via the RIM-binding domain) is required for this plasticity, implicating modulation of vesicle priming as the substrate for mossy fiber LTP.","method":"Acute in vivo viral expression of Munc13-1 domain constructs; electrophysiology at mossy fiber synapses; genetic epistasis","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — domain-specific constructs with separable functions tested in native synapse with defined plasticity readout","pmids":["21849565"],"is_preprint":false},{"year":2016,"finding":"Homozygous loss-of-function nonsense mutation in the N-terminal domain of MUNC13-1 (truncating after residue 101) causes marked depletion of the readily releasable pool of quanta at the neuromuscular junction with normal quantal release probability, and produces a fatal syndrome of microcephaly, cortical hyperexcitability, and myasthenia; mechanistically interpreted as syntaxin 1B being consigned to a nonfunctional closed state.","method":"Exome sequencing; in vitro microelectrode studies of neuromuscular transmission; electron microscopy of neuromuscular junctions","journal":"Neurology. Genetics","confidence":"High","confidence_rationale":"Tier 2 — human loss-of-function variant with electrophysiological characterization of specific priming defect","pmids":["27648472"],"is_preprint":false},{"year":2021,"finding":"Two distinct membrane-binding faces of the Munc13-1 C1C2B region control neurotransmitter release: a polybasic face (K603, R769) mediates Ca2+-independent liposome bridging and is essential for synaptic vesicle priming; a DAG/Ca2+/PIP2-binding face modulates Ca2+-evoked release and short-term plasticity.","method":"Site-directed mutagenesis; in vitro liposome bridging/fusion reconstitution; electrophysiology in hippocampal cultures","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — reconstitution plus mutagenesis plus neuronal electrophysiology with multiple complementary mutations","pmids":["34779770"],"is_preprint":false},{"year":2021,"finding":"Munc13-1 regulates synaptic vesicle replenishment via a Ca2+-phospholipid-dependent mechanism through its C2B domain; knockin mice with mutations abolishing Ca2+-phospholipid binding show increased synaptic depression and slowed recovery, while enhanced binding has opposite effects, establishing Munc13-1 as a core vesicle priming hub adjusting SV re-supply to demand.","method":"Knockin mouse lines with C2B domain point mutations; electrophysiology at calyx of Held","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockin with bidirectional mutations and defined electrophysiological phenotype","pmids":["34706220"],"is_preprint":false},{"year":2020,"finding":"NMR spectroscopy and SNARE assembly experiments show that Munc13-1 opens syntaxin-1 via interactions with the syntaxin-1 linker region (part of the closed conformation); point mutations in the linker strongly impair SNARE complex assembly and liposome fusion mediated by Munc13-1 fragments, even though direct binding of the linker to Munc13-1 is barely detectable; the syntaxin-1 SNARE motif binds Munc13-1 but disrupting this does not affect SNARE assembly.","method":"NMR spectroscopy; SNARE complex assembly assays; liposome fusion assays; mutagenesis","journal":"Protein science : a publication of the Protein Society","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal in vitro methods with systematic mutagenesis","pmids":["32086964"],"is_preprint":false},{"year":2022,"finding":"TDP-43 represses a cryptic exon-splicing event in UNC13A; loss of TDP-43 from the nucleus in human brain, neuronal cell lines, and iPSC-derived motor neurons causes inclusion of a cryptic exon in UNC13A mRNA and reduced UNC13A protein expression; ALS/FTD risk SNPs in the intron harboring the cryptic exon increase its inclusion in the context of TDP-43 dysfunction.","method":"TDP-43 knockdown/depletion in cell lines and iPSC-derived neurons; RNA splicing assays; patient brain tissue analysis; SNP functional testing","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — multiple model systems, patient tissue validation, SNP functional characterization, replicated independently in same issue","pmids":["35197626"],"is_preprint":false},{"year":2022,"finding":"TDP-43 depletion induces robust inclusion of a cryptic exon in UNC13A, resulting in nonsense-mediated decay and loss of UNC13A protein; two common intronic UNC13A polymorphisms at TDP-43 binding sites potentiate cryptic exon inclusion in cultured cells and in patient brain/spinal cord tissue.","method":"TDP-43 knockdown; RNA-seq; NMD inhibition assays; patient brain and spinal cord tissue; cell-based cryptic exon reporter assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in human patient tissue and cell models, replicated independently in same issue","pmids":["35197628"],"is_preprint":false},{"year":2023,"finding":"TDP-43's extreme N-terminus is important for repressing UNC13A cryptic exon inclusion; hnRNP L, hnRNP A1, and hnRNP A2B1 independently bind UNC13A RNA and repress cryptic exon inclusion in a TDP-43-independent manner; higher hnRNP L protein levels correlate with lower UNC13A cryptic RNA burden in ALS/FTD brains.","method":"TDP-43 domain deletion; RNA-binding protein knockdown; patient brain tissue correlation; RNA-immunoprecipitation","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — domain mapping plus independent RBP knockdowns plus patient tissue validation","pmids":["36930682"],"is_preprint":false},{"year":2018,"finding":"TNF-α impedes Fbxo45-dependent ubiquitination of Munc13-1 in spinal dorsal horn neurons, causing Munc13-1 accumulation at the presynaptic area; this accumulation increases mEPSC frequency and underlies neuropathic allodynia; knockdown of Fbxo45 in naive animals phenocopies neuropathic injury.","method":"Co-immunoprecipitation; ubiquitination assay; siRNA knockdown; behavioral allodynia testing; electrophysiology (mEPSC recording) in rat spinal cord","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-IP for complex, ubiquitination assay, siRNA knockdown with functional behavioral readout","pmids":["30042425"],"is_preprint":false},{"year":2013,"finding":"Munc13-1 translocates to the plasma membrane in a Doc2B- and Ca2+-dependent manner; co-expression with Doc2B enables Ca2+-triggered Munc13-1 plasma membrane recruitment; accumulation at the membrane depends on DAG, as the DAG-binding-deficient H567K mutant shows reduced accumulation.","method":"Live-cell imaging of fluorescently tagged proteins in PC12 cells; Ca2+ stimulation; H567K mutant comparison","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 3 — live imaging with mutant comparison, single lab","pmids":["24062723"],"is_preprint":false},{"year":2013,"finding":"Munc13-1 at the C1 domain directly binds alcohols (ethanol, butanol, octanol) with the binding site mapped to Glu-582 by photoaffinity labeling and mass spectrometry; Glu-582 mutations reduce alcohol binding; Drosophila Dunc-13 loss increases ethanol self-administration, rescued by rat Munc13-1 expression.","method":"Intrinsic fluorescence quenching; photoaffinity labeling with mass spectrometry; site-directed mutagenesis; Drosophila behavioral genetics","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding mapped to specific residue with multiple methods, in vivo rescue","pmids":["23692447"],"is_preprint":false},{"year":2024,"finding":"The Munc13-1 N-terminal region exerts autoinhibitory control over the C-terminal MUN domain: the C2A domain and CaM-binding domain each interact with the MUN domain and suppress SNARE assembly/liposome fusion activity; these inhibitory interactions are relieved by RIM2α zinc-finger domain and calmodulin, respectively.","method":"Purification of near-full-length Munc13-1 fragment; liposome fusion assays; NMR spectroscopy","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with NMR, first purification of near-full-length protein, mechanistically validated","pmids":["38417672"],"is_preprint":false},{"year":2021,"finding":"Munc13-1 self-assembles into nano-clusters on supported lipid bilayers; only clusters of ≥6 copies efficiently capture and retain synaptic vesicles; the C-terminal C2C domain is required for vesicle capture but not for clustering.","method":"Quantitative TIRF microscopy; step-wise photobleaching; reconstitution on supported lipid bilayers","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — reconstitution assay with quantitative imaging and domain dissection","pmids":["34227103"],"is_preprint":false},{"year":2024,"finding":"Munc13-1 clusters multiple SNARE complexes at the release site to synchronize fusion events, while Munc18-1 stoichiometrically interacts with trans-SNARE complexes to enhance N-to-C terminal zippering; when both are present, they differentially access dynamic trans-SNARE complexes to regulate fusion pore properties and quantal size.","method":"Single-vesicle fusion reconstitution; single-molecule imaging; SNARE complex assembly assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — single-molecule reconstitution with mechanistic dissection of SNARE chaperone roles","pmids":["38755165"],"is_preprint":false},{"year":2025,"finding":"A negatively charged polyE sequence in the Munc13-1 N-terminus (unique to Munc13-1 among Munc13 isoforms) binds the MUN domain via charge-charge interactions, inhibiting MUN activity in SNARE complex assembly; Ca2+ ions at ~40 μM compete with the polyE-MUN interaction to relieve this autoinhibition, providing a mechanism by which presynaptic Ca2+ influx activates Munc13-1.","method":"In vitro binding assays; SNARE complex assembly assays; mutagenesis (pseudophosphorylation); Ca2+ binding experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis and quantitative Ca2+ competition experiments","pmids":["40489622"],"is_preprint":false},{"year":2025,"finding":"ALS-associated RBPs MATR3, FUS, and hnRNPA1 regulate UNC13A transcription by binding to and downregulating REST mRNA, thereby de-repressing UNC13A transcription; loss of any of these RBPs in cultured cells or iPSC-derived motor neurons leads to REST overexpression and reduced UNC13A, the same pattern observed in motor neurons of ALS patients.","method":"RBP knockdown in cell lines; iPSC-derived motor neurons; patient tissue analysis; RNA-binding assays","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 — multiple RBPs tested in multiple systems with patient tissue validation, single lab","pmids":["40707625"],"is_preprint":false},{"year":2024,"finding":"TDP-43 depletion causes severe reduction in synaptic transmission (asynchronous network activity) largely driven by loss of UNC13A protein from cryptic exon inclusion; antisense oligonucleotides targeting the UNC13A cryptic exon rescue UNC13A protein levels and restore normal synaptic function.","method":"TDP-43 depletion in iPSC-derived neurons; MEA recordings; ASO treatment rescue experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — functional rescue by ASO establishes causal link between UNC13A loss and synaptic deficit, preprint","pmids":["38979232"],"is_preprint":true},{"year":2025,"finding":"Germline coding or splice-site variants in UNC13A cause a neurodevelopmental syndrome; three mechanisms of pathogenicity are identified: (1) reduced synaptic strength from reduced UNC13A protein expression, (2) increased neurotransmission from UNC13A gain-of-function, and (3) impaired regulation of neurotransmission by second messenger signalling—validated in mouse hippocampal neurons and C. elegans.","method":"Variant expression in mouse hippocampal neurons; C. elegans functional assays; electrophysiology; exome sequencing of patient cohort","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple variants characterized in two model systems with defined electrophysiological phenotypes, genotype-phenotype correlation","pmids":["41125872"],"is_preprint":false},{"year":2023,"finding":"Unc13A's calmodulin-binding domain (CaM-domain) dynamically stabilizes vesicle priming at release sites; CaM-domain mutation causes constitutive stabilization, increasing baseline transmission while blocking both short-term facilitation and presynaptic homeostatic potentiation; phorbol ester treatment similarly enhances release and blocks plasticity in wild-type, and is occluded by the CaM-domain mutation.","method":"Drosophila NMJ genetics; electrophysiology; STED super-resolution microscopy; mathematical modeling","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — genetic mutagenesis in Drosophila ortholog with electrophysiology, super-resolution imaging, and mathematical modeling","pmids":["37243591"],"is_preprint":false},{"year":2019,"finding":"RIM-BP2 primes synaptic vesicles at hippocampal mossy fiber synapses via recruitment and stabilization of Munc13-1 at the active zone; loss of RIM-BP2 reduces Munc13-1 at mossy fiber active zones and impairs vesicle docking/priming and release probability at this synapse type but has only mild effects at CA3-CA1 synapses.","method":"RIM-BP2 knockout mice; electrophysiology at two synapse types; immunogold electron microscopy for Munc13-1 localization","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — conditional knockout with direct protein localization measurement and synapse-type-specific electrophysiology","pmids":["31535974"],"is_preprint":false}],"current_model":"UNC13A (Munc13-1) is an essential presynaptic active zone protein that primes synaptic vesicles to a fusion-competent state by opening syntaxin-1 from its closed conformation and chaperoning SNARE complex assembly (together with Munc18-1) via its MUN domain; it bridges synaptic vesicle and plasma membranes through its elongated C1C2BMUNC2C structure, self-assembles into nanoclusters that determine the number of release sites, and its activity is regulated by diacylglycerol (C1 domain), Ca2+-calmodulin (CaM-binding domain), Ca2+-phospholipid (C2B domain), and RIM1α (C2A domain), with an autoinhibitory mechanism involving the polyE and C2A/CaM-binding domains suppressing the MUN domain until relieved by presynaptic Ca2+ and RIM/calmodulin; in ALS/FTD, nuclear loss of TDP-43 causes aberrant cryptic exon inclusion in UNC13A mRNA, nonsense-mediated decay, and loss of UNC13A protein, with disease-associated intronic SNPs at TDP-43 binding sites potentiating this mis-splicing."},"narrative":{"teleology":[{"year":1997,"claim":"Establishing how UNC13A contacts the exocytotic machinery: Munc13-1 was shown to directly bind the N-terminal domain of syntaxin-1 and associate with assembled SNARE complexes, placing it at the heart of vesicle fusion regulation.","evidence":"Three orthogonal biochemical binding assays (pulldown, co-IP, blot overlay) with syntaxin domain mapping","pmids":["8999968"],"confidence":"High","gaps":["Whether syntaxin binding is sufficient for priming was unknown","The functional consequence of the Munc13-1–SNARE interaction was not tested in neurons"]},{"year":1998,"claim":"Identifying UNC13A as a DAG/phorbol ester receptor independent of PKC resolved how diacylglycerol second-messenger signaling directly potentiates neurotransmitter release at the presynaptic terminal.","evidence":"Direct phorbol ester binding assays; overexpression at Xenopus NMJ with electrophysiology","pmids":["9697857"],"confidence":"High","gaps":["Whether DAG binding was required for the priming function per se was untested","Structural basis of DAG recognition was unknown"]},{"year":1999,"claim":"Knockout analysis definitively placed UNC13A at the vesicle priming step: Munc13-1-null neurons formed normal synapses but completely failed to generate a fusion-competent vesicle pool, blocking all physiological release while leaving latrotoxin-evoked release intact.","evidence":"Munc13-1 knockout mouse neurons; electrophysiology with multiple stimulation paradigms; electron microscopy","pmids":["10440375"],"confidence":"High","gaps":["Whether Munc13-1 directly opens syntaxin was unknown","The minimal priming domain had not been defined"]},{"year":2001,"claim":"Discovery that RIM1 binding is required for Munc13-1 priming function established the RIM–Munc13 axis as a core active zone module, with disruption phenocopying Munc13-1 loss.","evidence":"Biochemical interaction assays and electrophysiology in cultured neurons with domain deletions","pmids":["11343654"],"confidence":"High","gaps":["Structural basis of the RIM–Munc13 switch was unknown","Whether RIM controls Munc13-1 localization or activity was not distinguished"]},{"year":2005,"claim":"Mapping the minimal priming module to the C-terminal MUN-containing region (residues 1100–1735) and showing its dependence on syntaxin-1 binding established the domain architecture underlying Munc13-1's core catalytic function.","evidence":"Systematic deletion construct electrophysiology in chromaffin cells; point mutagenesis abolishing syntaxin binding","pmids":["16271475"],"confidence":"High","gaps":["How the MUN domain opens syntaxin mechanistically was unresolved","Role of C2C domain in membrane bridging was unknown"]},{"year":2005,"claim":"The NMR structure of the C1 domain revealed that a conserved tryptophan occludes the DAG-binding pocket, explaining why Munc13-1 has lower DAG affinity than PKC and requires conformational change for activation.","evidence":"NMR structure determination; comparison with PKC C1 domain","pmids":["15667202"],"confidence":"High","gaps":["Whether the occluded state serves as an autoinhibitory mechanism in vivo was unclear"]},{"year":2006,"claim":"Multiple studies in 2006 resolved the structural basis of the C2A homodimer/RIM heterodimer switch, demonstrated that RIM1α controls Munc13-1 active zone recruitment, and revealed rapid dynamic exchange of Munc13-1 at active zones—together establishing how Munc13-1 is targeted and retained at release sites.","evidence":"X-ray crystallography of C2A homodimer and C2A–RIM heterodimer; I121N mutagenesis in RIM1α KO mice; FRAP in Munc13-1-EYFP knockin mice","pmids":["16732694","16704978","17167095"],"confidence":"High","gaps":["Whether homodimerization has an autoinhibitory role in vivo was not resolved","Full-length structural context was missing"]},{"year":2006,"claim":"Studies in pancreatic beta cells established a non-neuronal priming role for Munc13-1: heterozygous knockout mice showed impaired glucose-stimulated insulin secretion and abnormal glucose tolerance, with DAG-dependent priming required for sustained insulin release.","evidence":"Munc13-1 heterozygous KO and H567K knockin mice; patch-clamp capacitance in beta cells; glucose tolerance tests","pmids":["16644700","16697276","12871971"],"confidence":"High","gaps":["Whether Munc13-1 regulates other non-neuronal secretory cell types was unknown","Relative contribution of Munc13-1 versus ubMunc13-2 in beta cells was not fully resolved"]},{"year":2007,"claim":"Activation of the C1 domain by phorbol ester increases vesicular release rate without affecting pool size, demonstrating that DAG signaling lowers the energy barrier for fusion rather than increasing the number of primed vesicles.","evidence":"Electrophysiology in H567K knockin mice with osmotic and Ca²⁺-triggered release paradigms","pmids":["17267576"],"confidence":"High","gaps":["How C1 domain activation structurally communicates to the MUN domain was unknown"]},{"year":2011,"claim":"Demonstrating that Munc13-1 and the RIM1α–Munc13-1 interaction are required for presynaptic long-term potentiation at mossy fiber synapses established vesicle priming modulation as a substrate for long-term plasticity.","evidence":"Acute viral expression of Munc13-1 domain constructs; electrophysiology at hippocampal mossy fiber synapses","pmids":["21849565"],"confidence":"High","gaps":["Whether other synapses use the same mechanism for presynaptic LTP was untested","The signaling cascade upstream of RIM–Munc13 during LTP was unresolved"]},{"year":2013,"claim":"Ca²⁺–calmodulin binding to Munc13-1 was shown to be a key determinant of short-term plasticity: knockin mice with a CaM-insensitive mutation showed slowed vesicle replenishment and aberrant depression, identifying Ca²⁺–CaM–Munc13-1 as the activity-dependent refilling signal.","evidence":"Knockin mouse (W464R) electrophysiology at calyx of Held","pmids":["23770256"],"confidence":"High","gaps":["How CaM binding structurally modulates MUN domain activity was not known","Whether CaM-mediated regulation is conserved across synapse types was unclear"]},{"year":2016,"claim":"A human homozygous truncating mutation in UNC13A causing fatal microcephaly, cortical hyperexcitability, and myasthenia directly linked UNC13A loss-of-function to human disease through depletion of the readily releasable vesicle pool.","evidence":"Exome sequencing; in vitro microelectrode studies at the neuromuscular junction; electron microscopy","pmids":["27648472"],"confidence":"High","gaps":["Whether partial loss-of-function variants produce milder phenotypes was unknown at the time"]},{"year":2017,"claim":"Super-resolution imaging revealed that Munc13-1 forms discrete nanoclusters that each constitute an independent release site, with the number of clusters determining synaptic weight—establishing a structural basis for how presynaptic strength is set.","evidence":"STED/STORM super-resolution microscopy with single-synapse glutamate imaging","pmids":["29230050"],"confidence":"High","gaps":["Molecular determinants of cluster formation were unresolved","Minimum copy number per functional cluster was not defined in neurons"]},{"year":2017,"claim":"A de novo gain-of-function variant (P814L) in UNC13A was identified as the cause of a dyskinetic movement disorder, demonstrating that increased vesicle fusion propensity from a single amino acid change produces a dominant disease phenotype.","evidence":"Whole-exome sequencing; electrophysiology in murine neurons and C. elegans","pmids":["28192369"],"confidence":"High","gaps":["Whether other gain-of-function variants produce similar phenotypes was unknown","Structural mechanism of P814L hyperactivity was not determined"]},{"year":2019,"claim":"Reconstitution and mutagenesis of the C1C2BMUNC2C region established that the C2C domain bridges vesicle and plasma membranes and is essential for docking, priming, and Ca²⁺-triggered release, completing the membrane-bridging model of Munc13-1 function.","evidence":"In vitro liposome bridging/fusion assays; C2C domain mutagenesis; electrophysiology in mouse neurons","pmids":["30816091"],"confidence":"High","gaps":["Full-length structural context of membrane bridging was not available","How C2C cooperates with C1-C2B region in intact protein was modeled but not directly shown"]},{"year":2019,"claim":"Single-molecule force spectroscopy demonstrated that the MUN domain stabilizes the Munc18-1/syntaxin-1/VAMP2 template complex by ~2.1 kBT and promotes SNAP-25 binding, providing the first quantitative energetic framework for how Munc13-1 and Munc18-1 cooperatively chaperone SNARE assembly.","evidence":"Single-molecule force spectroscopy; SNARE assembly reconstitution with purified components","pmids":["31888993"],"confidence":"High","gaps":["Whether additional regulatory domains modulate this cooperativity was not tested in this system"]},{"year":2020,"claim":"NMR and functional studies showed that Munc13-1 opens syntaxin-1 by acting on its linker region rather than the SNARE motif, clarifying the specific molecular step at which Munc13-1 converts syntaxin from closed to open conformation.","evidence":"NMR spectroscopy; SNARE complex assembly and liposome fusion assays with syntaxin linker mutations","pmids":["32086964"],"confidence":"High","gaps":["Direct binding of the linker to Munc13-1 was barely detectable, suggesting a transient or catalytic mechanism not fully captured"]},{"year":2021,"claim":"Dissection of the C1-C2B region revealed two functionally separable membrane-binding faces: a polybasic face essential for Ca²⁺-independent priming and a DAG/Ca²⁺/PIP₂ face that modulates evoked release and plasticity, resolving how one domain integrates constitutive priming with activity-dependent modulation.","evidence":"Site-directed mutagenesis; liposome reconstitution; hippocampal electrophysiology","pmids":["34779770"],"confidence":"High","gaps":["How these two faces are coordinated in vivo during trains of activity was not resolved"]},{"year":2021,"claim":"C2B domain knockin mice with bidirectional mutations established Ca²⁺-phospholipid binding at C2B as a core mechanism for activity-dependent vesicle replenishment, with enhanced binding accelerating recovery and impaired binding slowing it.","evidence":"Knockin mouse lines; electrophysiology at calyx of Held","pmids":["34706220"],"confidence":"High","gaps":["Whether C2B Ca²⁺ sensing cooperates with CaM binding during high-frequency firing was not directly tested"]},{"year":2022,"claim":"Two independent studies demonstrated that TDP-43 nuclear depletion—a hallmark of ALS/FTD—causes cryptic exon inclusion in UNC13A mRNA leading to nonsense-mediated decay and loss of protein, with common intronic risk SNPs at TDP-43 binding sites potentiating mis-splicing, thereby linking UNC13A loss to neurodegeneration.","evidence":"TDP-43 knockdown in cell lines and iPSC-neurons; patient brain/spinal cord tissue; SNP functional reporter assays; RNA-seq","pmids":["35197626","35197628"],"confidence":"High","gaps":["Whether UNC13A loss is causally sufficient for synaptic dysfunction in ALS was not yet shown with rescue experiments in peer-reviewed literature","Therapeutic targeting of the cryptic exon had not been validated in vivo"]},{"year":2023,"claim":"Additional RNA-binding proteins (hnRNP L, hnRNP A1, hnRNP A2B1) were identified as TDP-43-independent repressors of UNC13A cryptic exon inclusion, with hnRNP L levels inversely correlating with cryptic RNA burden in ALS/FTD brains, expanding the regulatory network controlling UNC13A mRNA integrity.","evidence":"RBP knockdown; RNA-immunoprecipitation; patient brain tissue correlation","pmids":["36930682"],"confidence":"High","gaps":["Whether modulating these hnRNPs can therapeutically compensate for TDP-43 loss was not tested","Mechanism of TDP-43-independent repression was not structurally defined"]},{"year":2024,"claim":"Near-full-length Munc13-1 reconstitution revealed dual autoinhibitory mechanisms: the C2A domain and CaM-binding domain each independently suppress MUN domain activity, and are specifically relieved by RIM and calmodulin respectively, providing the first integrated autoinhibition model.","evidence":"Purification of near-full-length Munc13-1; liposome fusion reconstitution; NMR spectroscopy","pmids":["38417672"],"confidence":"High","gaps":["Whether all inhibitory interactions are simultaneously engaged in the resting state was not determined","In vivo validation of the dual autoinhibition model was lacking"]},{"year":2024,"claim":"Single-vesicle reconstitution showed that Munc13-1 clusters multiple SNARE complexes at release sites to synchronize fusion pore opening, while Munc18-1 stoichiometrically engages trans-SNARE complexes to regulate zippering—revealing how both chaperones differentially control fusion pore properties.","evidence":"Single-vesicle fusion and single-molecule imaging reconstitution","pmids":["38755165"],"confidence":"High","gaps":["Whether SNARE clustering by Munc13-1 controls quantal size in vivo was not tested","The minimum Munc13-1 copy number for functional clustering in neurons remains debated"]},{"year":2025,"claim":"The polyE motif unique to Munc13-1 was identified as a Ca²⁺-sensitive autoinhibitory element: it binds the MUN domain via electrostatic interactions and is displaced by ~40 µM Ca²⁺, providing a direct mechanism linking presynaptic Ca²⁺ influx to relief of Munc13-1 autoinhibition.","evidence":"In vitro binding and SNARE assembly assays; Ca²⁺ competition experiments; charge-reversal mutagenesis","pmids":["40489622"],"confidence":"High","gaps":["In vivo relevance of polyE-mediated inhibition has not been tested with knockin animals","Whether polyE and C2A/CaM inhibitory mechanisms act sequentially or in parallel is unresolved"]},{"year":2025,"claim":"A comprehensive variant study established that germline UNC13A coding variants cause a neurodevelopmental syndrome through three distinct mechanisms—reduced synaptic strength, gain-of-function hyperactivation, and impaired second-messenger regulation—broadening the spectrum of UNC13A-associated disease.","evidence":"Patient cohort exome sequencing; variant expression in mouse hippocampal neurons and C. elegans with electrophysiology","pmids":["41125872"],"confidence":"High","gaps":["Genotype-phenotype correlation for milder variants is incomplete","Whether compensatory mechanisms by other Munc13 isoforms modulate disease severity is unknown"]},{"year":null,"claim":"Key open questions include: the full-length atomic structure of Munc13-1 in its autoinhibited and active conformations, in vivo validation of the polyE autoinhibitory mechanism, therapeutic efficacy of UNC13A cryptic exon-targeting ASOs in ALS/FTD animal models, and how Munc13-1 nanocluster stoichiometry is dynamically regulated during plasticity.","evidence":"","pmids":[],"confidence":"Low","gaps":["No full-length high-resolution structure exists","In vivo polyE knockin validation is lacking","ASO rescue of UNC13A cryptic exon has not been tested in animal models of ALS/FTD in peer-reviewed studies","How nanocluster copy number is regulated during plasticity is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,6,7,17,22]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,5,14,15,24,31,33,34]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[12,32,33]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,14,17,22,29]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[16]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,3,11,12,13,14,20,21,23,37,38]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,5,14,15,22,33]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,7,17,18,19,22,34]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[25,26,27,35]}],"complexes":["SNARE complex (syntaxin-1/SNAP-25/VAMP2)","RIM1–Munc13-1–CAST active zone complex"],"partners":["STX1A","RIMS1","RIMS2","UNC18A","CALM1","RIMBP2","ERC1","DOC2B"],"other_free_text":[]},"mechanistic_narrative":"UNC13A (Munc13-1) is an essential presynaptic active zone protein that primes synaptic vesicles to a fusion-competent state by opening syntaxin-1 from its closed conformation and cooperatively chaperoning SNARE complex assembly together with Munc18-1 via its MUN domain [PMID:10440375, PMID:15667202, PMID:31888993, PMID:32086964]. Its elongated C1C2BMUNC2C structure bridges synaptic vesicle and plasma membranes through distinct membrane-binding faces, with the C2C domain capturing vesicles and the C1-C2B region sensing diacylglycerol, Ca²⁺, and PIP₂ to modulate release probability and short-term plasticity; self-assembly into nanoclusters at the active zone defines the number of independent release sites and clusters multiple SNARE complexes to synchronize fusion [PMID:30816091, PMID:34779770, PMID:29230050, PMID:38755165]. Multiple autoinhibitory mechanisms—involving the polyE motif, C2A homodimerization, and CaM-binding domain interactions with the MUN domain—suppress priming activity until relieved by presynaptic Ca²⁺, RIM, and calmodulin, thereby coupling vesicle priming to synaptic activity and enabling presynaptic forms of short- and long-term plasticity [PMID:38417672, PMID:40489622, PMID:23770256, PMID:21849565]. Germline coding variants in UNC13A cause a neurodevelopmental syndrome through loss-of-function, gain-of-function, or impaired second-messenger regulation of neurotransmission, while in ALS/FTD, nuclear loss of TDP-43 triggers cryptic exon inclusion in UNC13A mRNA leading to nonsense-mediated decay and UNC13A protein depletion, a process potentiated by common intronic risk SNPs [PMID:41125872, PMID:35197626, PMID:35197628]."},"prefetch_data":{"uniprot":{"accession":"Q9UPW8","full_name":"Protein unc-13 homolog A","aliases":["Munc13-1"],"length_aa":1703,"mass_kda":193.0,"function":"Plays a role in vesicle maturation during exocytosis as a target of the diacylglycerol second messenger pathway. Involved in neurotransmitter release by acting in synaptic vesicle priming prior to vesicle fusion and participates in the activity-dependent refilling of readily releasable vesicle pool (RRP). Essential for synaptic vesicle maturation in most excitatory/glutamatergic but not inhibitory/GABA-mediated synapses. Facilitates neuronal dense core vesicles fusion as well as controls the location and efficiency of their synaptic release (By similarity). Also involved in secretory granule priming in insulin secretion. Plays a role in dendrite formation by melanocytes (PubMed:23999003)","subcellular_location":"Cytoplasm; Cell membrane; Presynaptic cell membrane; Presynaptic active zone","url":"https://www.uniprot.org/uniprotkb/Q9UPW8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/UNC13A","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/UNC13A","total_profiled":1310},"omim":[{"mim_id":"621457","title":"INTELLECTUAL DEVELOPMENTAL DISORDER WITH SEIZURES AND DYSMORPHIC FACIES; IDDSF","url":"https://www.omim.org/entry/621457"},{"mim_id":"621456","title":"NEURODEVELOPMENTAL DISORDER WITH SPEECH DELAY, MOVEMENT ABNORMALITIES, AND SEIZURES; NEDSMS","url":"https://www.omim.org/entry/621456"},{"mim_id":"621455","title":"NEURODEVELOPMENTAL DISORDER WITH HYPOTONIA, EPILEPSY, AND ABSENT SPEECH; NEDHES","url":"https://www.omim.org/entry/621455"},{"mim_id":"619305","title":"TANDEM C2 DOMAINS PROTEIN, NUCLEAR; TC2N","url":"https://www.omim.org/entry/619305"},{"mim_id":"617250","title":"ELKS/RAB6-INTERACTING/CAST FAMILY, MEMBER 2; ERC2","url":"https://www.omim.org/entry/617250"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":40.0},{"tissue":"pituitary gland","ntpm":30.1},{"tissue":"retina","ntpm":17.1}],"url":"https://www.proteinatlas.org/search/UNC13A"},"hgnc":{"alias_symbol":["KIAA1032","Munc13-1"],"prev_symbol":[]},"alphafold":{"accession":"Q9UPW8","domains":[{"cath_id":"2.60.40.150","chopping":"3-151","consensus_level":"high","plddt":83.6764,"start":3,"end":151},{"cath_id":"-","chopping":"514-672_814-911","consensus_level":"medium","plddt":84.1559,"start":514,"end":911},{"cath_id":"2.60.40.150","chopping":"686-793","consensus_level":"high","plddt":80.9568,"start":686,"end":793},{"cath_id":"-","chopping":"918-991","consensus_level":"medium","plddt":87.6823,"start":918,"end":991},{"cath_id":"-","chopping":"1000-1138","consensus_level":"high","plddt":89.9892,"start":1000,"end":1138},{"cath_id":"1.10.357.50","chopping":"1151-1328_1340-1396","consensus_level":"medium","plddt":90.9754,"start":1151,"end":1396},{"cath_id":"2.60.40.150","chopping":"1504-1690","consensus_level":"high","plddt":84.7933,"start":1504,"end":1690}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UPW8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UPW8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UPW8-F1-predicted_aligned_error_v6.png","plddt_mean":73.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UNC13A","jax_strain_url":"https://www.jax.org/strain/search?query=UNC13A"},"sequence":{"accession":"Q9UPW8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UPW8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UPW8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UPW8"}},"corpus_meta":[{"pmid":"10440375","id":"PMC_10440375","title":"Munc13-1 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specifically at the priming step.\",\n      \"method\": \"Munc13-1 knockout mouse neurons; electrophysiology; electron microscopy\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — clean KO with specific phenotypic readout, multiple stimulation paradigms tested, foundational paper with >600 citations\",\n      \"pmids\": [\"10440375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Munc13-1 is a presynaptic high-affinity phorbol ester and diacylglycerol receptor that associates with the plasma membrane upon phorbol ester binding and enhances neurotransmitter release when overexpressed presynaptically, acting in parallel with protein kinase C in the DAG second messenger pathway.\",\n      \"method\": \"Phorbol ester binding assays; overexpression in Xenopus neuromuscular junction; electrophysiology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct ligand binding assay plus functional overexpression rescue, replicated across labs\",\n      \"pmids\": [\"9697857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Munc13-1 directly interacts with the N-terminal coiled-coil domain of syntaxin via its C-terminus, and through this interaction binds to a subpopulation of the exocytotic SNARE core complex (syntaxin/SNAP-25/synaptobrevin), implicating Munc13-1 in modulating SNARE complex formation for vesicle exocytosis.\",\n      \"method\": \"Three independent biochemical binding assays (pulldown, co-immunoprecipitation, blot overlay); syntaxin binding domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — three orthogonal binding methods in single study, foundational interaction paper\",\n      \"pmids\": [\"8999968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Munc13-1 and RIM1 interact functionally at the active zone; disruption of the Munc13-1/RIM1 interaction causes loss of fusion-competent synaptic vesicles (phenocopying Munc13-1 deficiency), with RIM1 binding and vesicle priming mediated by two distinct structural modules of Munc13-1.\",\n      \"method\": \"Biochemical interaction assays; electrophysiology in cultured neurons; domain deletion analysis\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal functional and biochemical data, specific domain mapping, >300 citations\",\n      \"pmids\": [\"11343654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structures of the Munc13-1 C2A domain homodimer (1.44 Å) and Munc13-1 C2A/RIM zinc-finger heterodimer (1.78 Å) reveal that the C2A domain can homodimerize via a four-stranded concave beta-sandwich, and that homodimerization competes with RIM heterodimerization, establishing a structural switch relevant to vesicle priming and presynaptic plasticity.\",\n      \"method\": \"X-ray crystallography guided by NMR spectroscopy; structural validation of competing interactions\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures at near-atomic resolution combined with NMR, mechanistically validated\",\n      \"pmids\": [\"16732694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The minimal Munc13-1 domain required for priming activity is the C-terminal region (residues 1100–1735) containing both Munc13-homology domains and the C-terminal C2 domain; priming requires interaction with Syntaxin 1, as point mutants unable to bind Syntaxin 1 cannot prime chromaffin granules.\",\n      \"method\": \"Deletion construct electrophysiology gain-of-function assay in chromaffin cells; point mutagenesis\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — systematic deletion mapping combined with mutagenesis and functional electrophysiology\",\n      \"pmids\": [\"16271475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NMR structure of the Munc13-1 C1 domain reveals that a conserved tryptophan (Trp-22/Trp-588 in full-length) occludes the diacylglycerol/phorbol ester binding site—unlike PKC C1 domains—requiring a conformational change for ligand binding, explaining Munc13-1's lower DAG affinity compared to PKC.\",\n      \"method\": \"NMR structure determination; comparison with PKC C1 domain structures\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structure with mechanistic interpretation of ligand binding occlusion\",\n      \"pmids\": [\"15667202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Activation of the Munc13-1 C1 domain by phorbol ester (PDBu) increases the vesicular release rate without affecting readily releasable vesicle pool size, mechanistically lowering the energy barrier for vesicle fusion; the C1 domain mutant H567K is a gain-of-function that constitutively mimics the PDBu-activated state.\",\n      \"method\": \"Electrophysiology (osmotic release, Ca2+-triggered and spontaneous release assays); knockin mice expressing Munc13-1(H567K)\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple electrophysiological readouts in knockin mice plus pharmacological dissection\",\n      \"pmids\": [\"17267576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Munc13-1 forms a ternary complex with CAST and RIM1 at the cytomatrix of the active zone; CAST directly binds RIM1 and indirectly binds Munc13-1 through RIM1, and Bassoon associates with this complex, establishing a protein interaction network at the active zone.\",\n      \"method\": \"Co-immunoprecipitation; direct binding assays; immunolocalization\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct binding and co-IP demonstrated for complex components\",\n      \"pmids\": [\"12163476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Active zone recruitment of Munc13-1 and ubMunc13-2 is regulated by their binding to RIM1α; a single I121N point mutation in Munc13-1 abolishes RIM1α binding and prevents efficient synaptic recruitment; Munc13-1 levels are decreased in RIM1α-deficient brain and Munc13-1 is not properly enriched at active zones of mossy fiber terminals when RIM1α is absent.\",\n      \"method\": \"Point mutagenesis; in vitro binding assays; RIM1α knockout mice; immunohistochemistry; quantitative Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis + knockout mice + localization with functional consequence, multiple orthogonal methods\",\n      \"pmids\": [\"16704978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Domains of five active zone proteins (RIM1, Bassoon, CAST1/ELKS2, Aczonin/Piccolo, and Bassoon CC3) all converge on the N-terminal region of Munc13-1, establishing Munc13-1's N-terminus as a hub of protein–protein interactions at the active zone; expression of Aczonin-CC3 in neurons suppresses vesicle turnover.\",\n      \"method\": \"Yeast two-hybrid; pulldown assays; co-IP; expression of GFP fusion in neurons with functional readout\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple binding partners mapped to same domain, with partial functional follow-up\",\n      \"pmids\": [\"19812333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Munc13-1 is a major presynaptic target of Ca2+–calmodulin signaling; knockin mice expressing Ca2+–calmodulin-insensitive Munc13-1(W464R) show slower synaptic vesicle replenishment, aberrant short-term depression, and reduced recovery after high-frequency stimulation, establishing Ca2+–calmodulin–Munc13-1 signaling as a key determinant of short-term synaptic plasticity.\",\n      \"method\": \"Knockin mouse electrophysiology at calyx of Held; Ca2+-calmodulin binding-deficient point mutation\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockin with specific point mutation and defined electrophysiological phenotype\",\n      \"pmids\": [\"23770256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Munc13-1 molecules form multiple discrete supramolecular self-assemblies in the presynaptic terminal that serve as independent vesicular release sites by recruiting syntaxin-1; multiplicity of these assemblies controls presynaptic synaptic weight in glutamatergic synapses.\",\n      \"method\": \"Single-synapse glutamate imaging; super-resolution (STED/STORM) microscopy of presynaptic proteins\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple imaging modalities combined with functional release measurements\",\n      \"pmids\": [\"29230050\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A de novo Pro814Leu variant in UNC13A causes a dominant gain-of-function characterized by increased synaptic vesicle fusion propensity, increased initial release probability, and abnormal short-term plasticity, leading to a dyskinetic movement disorder in a human patient.\",\n      \"method\": \"Whole-exome sequencing; electrophysiology in murine neuronal cultures; functional analysis in C. elegans\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human variant characterised by electrophysiology in two model systems with defined molecular mechanism\",\n      \"pmids\": [\"28192369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Munc13-1 bridges the synaptic vesicle and plasma membranes through opposite ends of its elongated C1C2BMUNC2C structure; mutations in the C2C domain membrane-binding sites disrupt liposome bridging and fusion in vitro and abolish synaptic vesicle docking, priming, and Ca2+-triggered release in mouse neurons, with a single residue substitution nearly completely abrogating release.\",\n      \"method\": \"In vitro liposome fusion/bridging assays; site-directed mutagenesis; electrophysiology in mouse neurons\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in vitro + mutagenesis + neuronal electrophysiology, multiple orthogonal methods\",\n      \"pmids\": [\"30816091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The MUN domain of Munc13-1 stabilizes the Munc18-1/syntaxin-1/VAMP2 template complex by ~2.1 kBT, enhancing SNAP-25 binding and subsequent full SNARE assembly; Munc13-1 and Munc18-1 cooperatively chaperone SNARE folding through a tetrameric complex.\",\n      \"method\": \"Single-molecule force spectroscopy; mutational analysis; in vitro SNARE assembly assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule reconstitution with mutagenesis and quantitative energetic measurements\",\n      \"pmids\": [\"31888993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"FRAP experiments in Munc13-1-EYFP knockin mice show that Munc13-1 is rapidly and continuously exchanged at active zones (tau1 ~3 min; tau2 ~80 min), demonstrating that presynaptic active zones are highly dynamic; exchange kinetics are reduced by chronic suppression of spontaneous activity but not by proteasome inhibitors or acute stimulation.\",\n      \"method\": \"FRAP in knockin mice expressing endogenous Munc13-1-EYFP; live imaging\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — endogenous knockin FRAP with pharmacological manipulations and activity perturbations\",\n      \"pmids\": [\"17167095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Munc13-1 is present in pancreatic islet beta cells and regulates insulin granule priming; overexpressed Munc13-1 translocates to plasma membrane in a diacylglycerol-dependent manner and greatly amplifies insulin exocytosis, an effect abolished by the DAG binding-deficient H567K mutant.\",\n      \"method\": \"Patch-clamp capacitance measurements; radioimmunoassay; GFP-fusion overexpression with DAG binding-deficient mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology plus mutant dissection plus biochemical assay\",\n      \"pmids\": [\"12871971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Munc13-1 heterozygous knockout mice exhibit reduced glucose-stimulated insulin secretion and abnormal glucose tolerance due to a primary islet beta-cell secretory defect involving granule priming deficits; DAG binding-deficient Munc13-1(H567K) knockin shows milder effects, confirming DAG-dependent priming role.\",\n      \"method\": \"Heterozygous knockout and knockin mice; glucose tolerance tests; patch-clamp capacitance measurements in beta cells\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockout/knockin with defined cellular electrophysiological phenotype\",\n      \"pmids\": [\"16644700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Munc13-1 is required for the second phase of sustained insulin release from pancreatic beta cells; Munc13-1 knockout reduces sustained release upon prolonged stimulation, and this involves DAG signaling since it is also reduced in H567K DAG-binding-deficient knockin mice.\",\n      \"method\": \"Munc13-1 knockout and knockin mice; patch-clamp exocytosis measurements in primary beta cells\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO and knockin with specific electrophysiological phenotype\",\n      \"pmids\": [\"16697276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Munc13-1 is required for presynaptic long-term potentiation (LTP) at hippocampal mossy fiber synapses, and the interaction between RIM1α and Munc13-1 (via the RIM-binding domain) is required for this plasticity, implicating modulation of vesicle priming as the substrate for mossy fiber LTP.\",\n      \"method\": \"Acute in vivo viral expression of Munc13-1 domain constructs; electrophysiology at mossy fiber synapses; genetic epistasis\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain-specific constructs with separable functions tested in native synapse with defined plasticity readout\",\n      \"pmids\": [\"21849565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Homozygous loss-of-function nonsense mutation in the N-terminal domain of MUNC13-1 (truncating after residue 101) causes marked depletion of the readily releasable pool of quanta at the neuromuscular junction with normal quantal release probability, and produces a fatal syndrome of microcephaly, cortical hyperexcitability, and myasthenia; mechanistically interpreted as syntaxin 1B being consigned to a nonfunctional closed state.\",\n      \"method\": \"Exome sequencing; in vitro microelectrode studies of neuromuscular transmission; electron microscopy of neuromuscular junctions\",\n      \"journal\": \"Neurology. Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human loss-of-function variant with electrophysiological characterization of specific priming defect\",\n      \"pmids\": [\"27648472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Two distinct membrane-binding faces of the Munc13-1 C1C2B region control neurotransmitter release: a polybasic face (K603, R769) mediates Ca2+-independent liposome bridging and is essential for synaptic vesicle priming; a DAG/Ca2+/PIP2-binding face modulates Ca2+-evoked release and short-term plasticity.\",\n      \"method\": \"Site-directed mutagenesis; in vitro liposome bridging/fusion reconstitution; electrophysiology in hippocampal cultures\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution plus mutagenesis plus neuronal electrophysiology with multiple complementary mutations\",\n      \"pmids\": [\"34779770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Munc13-1 regulates synaptic vesicle replenishment via a Ca2+-phospholipid-dependent mechanism through its C2B domain; knockin mice with mutations abolishing Ca2+-phospholipid binding show increased synaptic depression and slowed recovery, while enhanced binding has opposite effects, establishing Munc13-1 as a core vesicle priming hub adjusting SV re-supply to demand.\",\n      \"method\": \"Knockin mouse lines with C2B domain point mutations; electrophysiology at calyx of Held\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockin with bidirectional mutations and defined electrophysiological phenotype\",\n      \"pmids\": [\"34706220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NMR spectroscopy and SNARE assembly experiments show that Munc13-1 opens syntaxin-1 via interactions with the syntaxin-1 linker region (part of the closed conformation); point mutations in the linker strongly impair SNARE complex assembly and liposome fusion mediated by Munc13-1 fragments, even though direct binding of the linker to Munc13-1 is barely detectable; the syntaxin-1 SNARE motif binds Munc13-1 but disrupting this does not affect SNARE assembly.\",\n      \"method\": \"NMR spectroscopy; SNARE complex assembly assays; liposome fusion assays; mutagenesis\",\n      \"journal\": \"Protein science : a publication of the Protein Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal in vitro methods with systematic mutagenesis\",\n      \"pmids\": [\"32086964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TDP-43 represses a cryptic exon-splicing event in UNC13A; loss of TDP-43 from the nucleus in human brain, neuronal cell lines, and iPSC-derived motor neurons causes inclusion of a cryptic exon in UNC13A mRNA and reduced UNC13A protein expression; ALS/FTD risk SNPs in the intron harboring the cryptic exon increase its inclusion in the context of TDP-43 dysfunction.\",\n      \"method\": \"TDP-43 knockdown/depletion in cell lines and iPSC-derived neurons; RNA splicing assays; patient brain tissue analysis; SNP functional testing\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple model systems, patient tissue validation, SNP functional characterization, replicated independently in same issue\",\n      \"pmids\": [\"35197626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TDP-43 depletion induces robust inclusion of a cryptic exon in UNC13A, resulting in nonsense-mediated decay and loss of UNC13A protein; two common intronic UNC13A polymorphisms at TDP-43 binding sites potentiate cryptic exon inclusion in cultured cells and in patient brain/spinal cord tissue.\",\n      \"method\": \"TDP-43 knockdown; RNA-seq; NMD inhibition assays; patient brain and spinal cord tissue; cell-based cryptic exon reporter assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in human patient tissue and cell models, replicated independently in same issue\",\n      \"pmids\": [\"35197628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TDP-43's extreme N-terminus is important for repressing UNC13A cryptic exon inclusion; hnRNP L, hnRNP A1, and hnRNP A2B1 independently bind UNC13A RNA and repress cryptic exon inclusion in a TDP-43-independent manner; higher hnRNP L protein levels correlate with lower UNC13A cryptic RNA burden in ALS/FTD brains.\",\n      \"method\": \"TDP-43 domain deletion; RNA-binding protein knockdown; patient brain tissue correlation; RNA-immunoprecipitation\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain mapping plus independent RBP knockdowns plus patient tissue validation\",\n      \"pmids\": [\"36930682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TNF-α impedes Fbxo45-dependent ubiquitination of Munc13-1 in spinal dorsal horn neurons, causing Munc13-1 accumulation at the presynaptic area; this accumulation increases mEPSC frequency and underlies neuropathic allodynia; knockdown of Fbxo45 in naive animals phenocopies neuropathic injury.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay; siRNA knockdown; behavioral allodynia testing; electrophysiology (mEPSC recording) in rat spinal cord\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP for complex, ubiquitination assay, siRNA knockdown with functional behavioral readout\",\n      \"pmids\": [\"30042425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Munc13-1 translocates to the plasma membrane in a Doc2B- and Ca2+-dependent manner; co-expression with Doc2B enables Ca2+-triggered Munc13-1 plasma membrane recruitment; accumulation at the membrane depends on DAG, as the DAG-binding-deficient H567K mutant shows reduced accumulation.\",\n      \"method\": \"Live-cell imaging of fluorescently tagged proteins in PC12 cells; Ca2+ stimulation; H567K mutant comparison\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — live imaging with mutant comparison, single lab\",\n      \"pmids\": [\"24062723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Munc13-1 at the C1 domain directly binds alcohols (ethanol, butanol, octanol) with the binding site mapped to Glu-582 by photoaffinity labeling and mass spectrometry; Glu-582 mutations reduce alcohol binding; Drosophila Dunc-13 loss increases ethanol self-administration, rescued by rat Munc13-1 expression.\",\n      \"method\": \"Intrinsic fluorescence quenching; photoaffinity labeling with mass spectrometry; site-directed mutagenesis; Drosophila behavioral genetics\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding mapped to specific residue with multiple methods, in vivo rescue\",\n      \"pmids\": [\"23692447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The Munc13-1 N-terminal region exerts autoinhibitory control over the C-terminal MUN domain: the C2A domain and CaM-binding domain each interact with the MUN domain and suppress SNARE assembly/liposome fusion activity; these inhibitory interactions are relieved by RIM2α zinc-finger domain and calmodulin, respectively.\",\n      \"method\": \"Purification of near-full-length Munc13-1 fragment; liposome fusion assays; NMR spectroscopy\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with NMR, first purification of near-full-length protein, mechanistically validated\",\n      \"pmids\": [\"38417672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Munc13-1 self-assembles into nano-clusters on supported lipid bilayers; only clusters of ≥6 copies efficiently capture and retain synaptic vesicles; the C-terminal C2C domain is required for vesicle capture but not for clustering.\",\n      \"method\": \"Quantitative TIRF microscopy; step-wise photobleaching; reconstitution on supported lipid bilayers\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reconstitution assay with quantitative imaging and domain dissection\",\n      \"pmids\": [\"34227103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Munc13-1 clusters multiple SNARE complexes at the release site to synchronize fusion events, while Munc18-1 stoichiometrically interacts with trans-SNARE complexes to enhance N-to-C terminal zippering; when both are present, they differentially access dynamic trans-SNARE complexes to regulate fusion pore properties and quantal size.\",\n      \"method\": \"Single-vesicle fusion reconstitution; single-molecule imaging; SNARE complex assembly assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule reconstitution with mechanistic dissection of SNARE chaperone roles\",\n      \"pmids\": [\"38755165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A negatively charged polyE sequence in the Munc13-1 N-terminus (unique to Munc13-1 among Munc13 isoforms) binds the MUN domain via charge-charge interactions, inhibiting MUN activity in SNARE complex assembly; Ca2+ ions at ~40 μM compete with the polyE-MUN interaction to relieve this autoinhibition, providing a mechanism by which presynaptic Ca2+ influx activates Munc13-1.\",\n      \"method\": \"In vitro binding assays; SNARE complex assembly assays; mutagenesis (pseudophosphorylation); Ca2+ binding experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis and quantitative Ca2+ competition experiments\",\n      \"pmids\": [\"40489622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ALS-associated RBPs MATR3, FUS, and hnRNPA1 regulate UNC13A transcription by binding to and downregulating REST mRNA, thereby de-repressing UNC13A transcription; loss of any of these RBPs in cultured cells or iPSC-derived motor neurons leads to REST overexpression and reduced UNC13A, the same pattern observed in motor neurons of ALS patients.\",\n      \"method\": \"RBP knockdown in cell lines; iPSC-derived motor neurons; patient tissue analysis; RNA-binding assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple RBPs tested in multiple systems with patient tissue validation, single lab\",\n      \"pmids\": [\"40707625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TDP-43 depletion causes severe reduction in synaptic transmission (asynchronous network activity) largely driven by loss of UNC13A protein from cryptic exon inclusion; antisense oligonucleotides targeting the UNC13A cryptic exon rescue UNC13A protein levels and restore normal synaptic function.\",\n      \"method\": \"TDP-43 depletion in iPSC-derived neurons; MEA recordings; ASO treatment rescue experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional rescue by ASO establishes causal link between UNC13A loss and synaptic deficit, preprint\",\n      \"pmids\": [\"38979232\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Germline coding or splice-site variants in UNC13A cause a neurodevelopmental syndrome; three mechanisms of pathogenicity are identified: (1) reduced synaptic strength from reduced UNC13A protein expression, (2) increased neurotransmission from UNC13A gain-of-function, and (3) impaired regulation of neurotransmission by second messenger signalling—validated in mouse hippocampal neurons and C. elegans.\",\n      \"method\": \"Variant expression in mouse hippocampal neurons; C. elegans functional assays; electrophysiology; exome sequencing of patient cohort\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple variants characterized in two model systems with defined electrophysiological phenotypes, genotype-phenotype correlation\",\n      \"pmids\": [\"41125872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Unc13A's calmodulin-binding domain (CaM-domain) dynamically stabilizes vesicle priming at release sites; CaM-domain mutation causes constitutive stabilization, increasing baseline transmission while blocking both short-term facilitation and presynaptic homeostatic potentiation; phorbol ester treatment similarly enhances release and blocks plasticity in wild-type, and is occluded by the CaM-domain mutation.\",\n      \"method\": \"Drosophila NMJ genetics; electrophysiology; STED super-resolution microscopy; mathematical modeling\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic mutagenesis in Drosophila ortholog with electrophysiology, super-resolution imaging, and mathematical modeling\",\n      \"pmids\": [\"37243591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RIM-BP2 primes synaptic vesicles at hippocampal mossy fiber synapses via recruitment and stabilization of Munc13-1 at the active zone; loss of RIM-BP2 reduces Munc13-1 at mossy fiber active zones and impairs vesicle docking/priming and release probability at this synapse type but has only mild effects at CA3-CA1 synapses.\",\n      \"method\": \"RIM-BP2 knockout mice; electrophysiology at two synapse types; immunogold electron microscopy for Munc13-1 localization\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional knockout with direct protein localization measurement and synapse-type-specific electrophysiology\",\n      \"pmids\": [\"31535974\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UNC13A (Munc13-1) is an essential presynaptic active zone protein that primes synaptic vesicles to a fusion-competent state by opening syntaxin-1 from its closed conformation and chaperoning SNARE complex assembly (together with Munc18-1) via its MUN domain; it bridges synaptic vesicle and plasma membranes through its elongated C1C2BMUNC2C structure, self-assembles into nanoclusters that determine the number of release sites, and its activity is regulated by diacylglycerol (C1 domain), Ca2+-calmodulin (CaM-binding domain), Ca2+-phospholipid (C2B domain), and RIM1α (C2A domain), with an autoinhibitory mechanism involving the polyE and C2A/CaM-binding domains suppressing the MUN domain until relieved by presynaptic Ca2+ and RIM/calmodulin; in ALS/FTD, nuclear loss of TDP-43 causes aberrant cryptic exon inclusion in UNC13A mRNA, nonsense-mediated decay, and loss of UNC13A protein, with disease-associated intronic SNPs at TDP-43 binding sites potentiating this mis-splicing.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"UNC13A (Munc13-1) is an essential presynaptic active zone protein that primes synaptic vesicles to a fusion-competent state by opening syntaxin-1 from its closed conformation and cooperatively chaperoning SNARE complex assembly together with Munc18-1 via its MUN domain [PMID:10440375, PMID:15667202, PMID:31888993, PMID:32086964]. Its elongated C1C2BMUNC2C structure bridges synaptic vesicle and plasma membranes through distinct membrane-binding faces, with the C2C domain capturing vesicles and the C1-C2B region sensing diacylglycerol, Ca²⁺, and PIP₂ to modulate release probability and short-term plasticity; self-assembly into nanoclusters at the active zone defines the number of independent release sites and clusters multiple SNARE complexes to synchronize fusion [PMID:30816091, PMID:34779770, PMID:29230050, PMID:38755165]. Multiple autoinhibitory mechanisms—involving the polyE motif, C2A homodimerization, and CaM-binding domain interactions with the MUN domain—suppress priming activity until relieved by presynaptic Ca²⁺, RIM, and calmodulin, thereby coupling vesicle priming to synaptic activity and enabling presynaptic forms of short- and long-term plasticity [PMID:38417672, PMID:40489622, PMID:23770256, PMID:21849565]. Germline coding variants in UNC13A cause a neurodevelopmental syndrome through loss-of-function, gain-of-function, or impaired second-messenger regulation of neurotransmission, while in ALS/FTD, nuclear loss of TDP-43 triggers cryptic exon inclusion in UNC13A mRNA leading to nonsense-mediated decay and UNC13A protein depletion, a process potentiated by common intronic risk SNPs [PMID:41125872, PMID:35197626, PMID:35197628].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing how UNC13A contacts the exocytotic machinery: Munc13-1 was shown to directly bind the N-terminal domain of syntaxin-1 and associate with assembled SNARE complexes, placing it at the heart of vesicle fusion regulation.\",\n      \"evidence\": \"Three orthogonal biochemical binding assays (pulldown, co-IP, blot overlay) with syntaxin domain mapping\",\n      \"pmids\": [\"8999968\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether syntaxin binding is sufficient for priming was unknown\", \"The functional consequence of the Munc13-1–SNARE interaction was not tested in neurons\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identifying UNC13A as a DAG/phorbol ester receptor independent of PKC resolved how diacylglycerol second-messenger signaling directly potentiates neurotransmitter release at the presynaptic terminal.\",\n      \"evidence\": \"Direct phorbol ester binding assays; overexpression at Xenopus NMJ with electrophysiology\",\n      \"pmids\": [\"9697857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether DAG binding was required for the priming function per se was untested\", \"Structural basis of DAG recognition was unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Knockout analysis definitively placed UNC13A at the vesicle priming step: Munc13-1-null neurons formed normal synapses but completely failed to generate a fusion-competent vesicle pool, blocking all physiological release while leaving latrotoxin-evoked release intact.\",\n      \"evidence\": \"Munc13-1 knockout mouse neurons; electrophysiology with multiple stimulation paradigms; electron microscopy\",\n      \"pmids\": [\"10440375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Munc13-1 directly opens syntaxin was unknown\", \"The minimal priming domain had not been defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Discovery that RIM1 binding is required for Munc13-1 priming function established the RIM–Munc13 axis as a core active zone module, with disruption phenocopying Munc13-1 loss.\",\n      \"evidence\": \"Biochemical interaction assays and electrophysiology in cultured neurons with domain deletions\",\n      \"pmids\": [\"11343654\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the RIM–Munc13 switch was unknown\", \"Whether RIM controls Munc13-1 localization or activity was not distinguished\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Mapping the minimal priming module to the C-terminal MUN-containing region (residues 1100–1735) and showing its dependence on syntaxin-1 binding established the domain architecture underlying Munc13-1's core catalytic function.\",\n      \"evidence\": \"Systematic deletion construct electrophysiology in chromaffin cells; point mutagenesis abolishing syntaxin binding\",\n      \"pmids\": [\"16271475\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the MUN domain opens syntaxin mechanistically was unresolved\", \"Role of C2C domain in membrane bridging was unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The NMR structure of the C1 domain revealed that a conserved tryptophan occludes the DAG-binding pocket, explaining why Munc13-1 has lower DAG affinity than PKC and requires conformational change for activation.\",\n      \"evidence\": \"NMR structure determination; comparison with PKC C1 domain\",\n      \"pmids\": [\"15667202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the occluded state serves as an autoinhibitory mechanism in vivo was unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Multiple studies in 2006 resolved the structural basis of the C2A homodimer/RIM heterodimer switch, demonstrated that RIM1α controls Munc13-1 active zone recruitment, and revealed rapid dynamic exchange of Munc13-1 at active zones—together establishing how Munc13-1 is targeted and retained at release sites.\",\n      \"evidence\": \"X-ray crystallography of C2A homodimer and C2A–RIM heterodimer; I121N mutagenesis in RIM1α KO mice; FRAP in Munc13-1-EYFP knockin mice\",\n      \"pmids\": [\"16732694\", \"16704978\", \"17167095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether homodimerization has an autoinhibitory role in vivo was not resolved\", \"Full-length structural context was missing\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Studies in pancreatic beta cells established a non-neuronal priming role for Munc13-1: heterozygous knockout mice showed impaired glucose-stimulated insulin secretion and abnormal glucose tolerance, with DAG-dependent priming required for sustained insulin release.\",\n      \"evidence\": \"Munc13-1 heterozygous KO and H567K knockin mice; patch-clamp capacitance in beta cells; glucose tolerance tests\",\n      \"pmids\": [\"16644700\", \"16697276\", \"12871971\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Munc13-1 regulates other non-neuronal secretory cell types was unknown\", \"Relative contribution of Munc13-1 versus ubMunc13-2 in beta cells was not fully resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Activation of the C1 domain by phorbol ester increases vesicular release rate without affecting pool size, demonstrating that DAG signaling lowers the energy barrier for fusion rather than increasing the number of primed vesicles.\",\n      \"evidence\": \"Electrophysiology in H567K knockin mice with osmotic and Ca²⁺-triggered release paradigms\",\n      \"pmids\": [\"17267576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How C1 domain activation structurally communicates to the MUN domain was unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that Munc13-1 and the RIM1α–Munc13-1 interaction are required for presynaptic long-term potentiation at mossy fiber synapses established vesicle priming modulation as a substrate for long-term plasticity.\",\n      \"evidence\": \"Acute viral expression of Munc13-1 domain constructs; electrophysiology at hippocampal mossy fiber synapses\",\n      \"pmids\": [\"21849565\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other synapses use the same mechanism for presynaptic LTP was untested\", \"The signaling cascade upstream of RIM–Munc13 during LTP was unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Ca²⁺–calmodulin binding to Munc13-1 was shown to be a key determinant of short-term plasticity: knockin mice with a CaM-insensitive mutation showed slowed vesicle replenishment and aberrant depression, identifying Ca²⁺–CaM–Munc13-1 as the activity-dependent refilling signal.\",\n      \"evidence\": \"Knockin mouse (W464R) electrophysiology at calyx of Held\",\n      \"pmids\": [\"23770256\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CaM binding structurally modulates MUN domain activity was not known\", \"Whether CaM-mediated regulation is conserved across synapse types was unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"A human homozygous truncating mutation in UNC13A causing fatal microcephaly, cortical hyperexcitability, and myasthenia directly linked UNC13A loss-of-function to human disease through depletion of the readily releasable vesicle pool.\",\n      \"evidence\": \"Exome sequencing; in vitro microelectrode studies at the neuromuscular junction; electron microscopy\",\n      \"pmids\": [\"27648472\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether partial loss-of-function variants produce milder phenotypes was unknown at the time\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Super-resolution imaging revealed that Munc13-1 forms discrete nanoclusters that each constitute an independent release site, with the number of clusters determining synaptic weight—establishing a structural basis for how presynaptic strength is set.\",\n      \"evidence\": \"STED/STORM super-resolution microscopy with single-synapse glutamate imaging\",\n      \"pmids\": [\"29230050\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular determinants of cluster formation were unresolved\", \"Minimum copy number per functional cluster was not defined in neurons\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"A de novo gain-of-function variant (P814L) in UNC13A was identified as the cause of a dyskinetic movement disorder, demonstrating that increased vesicle fusion propensity from a single amino acid change produces a dominant disease phenotype.\",\n      \"evidence\": \"Whole-exome sequencing; electrophysiology in murine neurons and C. elegans\",\n      \"pmids\": [\"28192369\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other gain-of-function variants produce similar phenotypes was unknown\", \"Structural mechanism of P814L hyperactivity was not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Reconstitution and mutagenesis of the C1C2BMUNC2C region established that the C2C domain bridges vesicle and plasma membranes and is essential for docking, priming, and Ca²⁺-triggered release, completing the membrane-bridging model of Munc13-1 function.\",\n      \"evidence\": \"In vitro liposome bridging/fusion assays; C2C domain mutagenesis; electrophysiology in mouse neurons\",\n      \"pmids\": [\"30816091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length structural context of membrane bridging was not available\", \"How C2C cooperates with C1-C2B region in intact protein was modeled but not directly shown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Single-molecule force spectroscopy demonstrated that the MUN domain stabilizes the Munc18-1/syntaxin-1/VAMP2 template complex by ~2.1 kBT and promotes SNAP-25 binding, providing the first quantitative energetic framework for how Munc13-1 and Munc18-1 cooperatively chaperone SNARE assembly.\",\n      \"evidence\": \"Single-molecule force spectroscopy; SNARE assembly reconstitution with purified components\",\n      \"pmids\": [\"31888993\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether additional regulatory domains modulate this cooperativity was not tested in this system\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"NMR and functional studies showed that Munc13-1 opens syntaxin-1 by acting on its linker region rather than the SNARE motif, clarifying the specific molecular step at which Munc13-1 converts syntaxin from closed to open conformation.\",\n      \"evidence\": \"NMR spectroscopy; SNARE complex assembly and liposome fusion assays with syntaxin linker mutations\",\n      \"pmids\": [\"32086964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding of the linker to Munc13-1 was barely detectable, suggesting a transient or catalytic mechanism not fully captured\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Dissection of the C1-C2B region revealed two functionally separable membrane-binding faces: a polybasic face essential for Ca²⁺-independent priming and a DAG/Ca²⁺/PIP₂ face that modulates evoked release and plasticity, resolving how one domain integrates constitutive priming with activity-dependent modulation.\",\n      \"evidence\": \"Site-directed mutagenesis; liposome reconstitution; hippocampal electrophysiology\",\n      \"pmids\": [\"34779770\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How these two faces are coordinated in vivo during trains of activity was not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"C2B domain knockin mice with bidirectional mutations established Ca²⁺-phospholipid binding at C2B as a core mechanism for activity-dependent vesicle replenishment, with enhanced binding accelerating recovery and impaired binding slowing it.\",\n      \"evidence\": \"Knockin mouse lines; electrophysiology at calyx of Held\",\n      \"pmids\": [\"34706220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether C2B Ca²⁺ sensing cooperates with CaM binding during high-frequency firing was not directly tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Two independent studies demonstrated that TDP-43 nuclear depletion—a hallmark of ALS/FTD—causes cryptic exon inclusion in UNC13A mRNA leading to nonsense-mediated decay and loss of protein, with common intronic risk SNPs at TDP-43 binding sites potentiating mis-splicing, thereby linking UNC13A loss to neurodegeneration.\",\n      \"evidence\": \"TDP-43 knockdown in cell lines and iPSC-neurons; patient brain/spinal cord tissue; SNP functional reporter assays; RNA-seq\",\n      \"pmids\": [\"35197626\", \"35197628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether UNC13A loss is causally sufficient for synaptic dysfunction in ALS was not yet shown with rescue experiments in peer-reviewed literature\", \"Therapeutic targeting of the cryptic exon had not been validated in vivo\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Additional RNA-binding proteins (hnRNP L, hnRNP A1, hnRNP A2B1) were identified as TDP-43-independent repressors of UNC13A cryptic exon inclusion, with hnRNP L levels inversely correlating with cryptic RNA burden in ALS/FTD brains, expanding the regulatory network controlling UNC13A mRNA integrity.\",\n      \"evidence\": \"RBP knockdown; RNA-immunoprecipitation; patient brain tissue correlation\",\n      \"pmids\": [\"36930682\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether modulating these hnRNPs can therapeutically compensate for TDP-43 loss was not tested\", \"Mechanism of TDP-43-independent repression was not structurally defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Near-full-length Munc13-1 reconstitution revealed dual autoinhibitory mechanisms: the C2A domain and CaM-binding domain each independently suppress MUN domain activity, and are specifically relieved by RIM and calmodulin respectively, providing the first integrated autoinhibition model.\",\n      \"evidence\": \"Purification of near-full-length Munc13-1; liposome fusion reconstitution; NMR spectroscopy\",\n      \"pmids\": [\"38417672\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether all inhibitory interactions are simultaneously engaged in the resting state was not determined\", \"In vivo validation of the dual autoinhibition model was lacking\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Single-vesicle reconstitution showed that Munc13-1 clusters multiple SNARE complexes at release sites to synchronize fusion pore opening, while Munc18-1 stoichiometrically engages trans-SNARE complexes to regulate zippering—revealing how both chaperones differentially control fusion pore properties.\",\n      \"evidence\": \"Single-vesicle fusion and single-molecule imaging reconstitution\",\n      \"pmids\": [\"38755165\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SNARE clustering by Munc13-1 controls quantal size in vivo was not tested\", \"The minimum Munc13-1 copy number for functional clustering in neurons remains debated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The polyE motif unique to Munc13-1 was identified as a Ca²⁺-sensitive autoinhibitory element: it binds the MUN domain via electrostatic interactions and is displaced by ~40 µM Ca²⁺, providing a direct mechanism linking presynaptic Ca²⁺ influx to relief of Munc13-1 autoinhibition.\",\n      \"evidence\": \"In vitro binding and SNARE assembly assays; Ca²⁺ competition experiments; charge-reversal mutagenesis\",\n      \"pmids\": [\"40489622\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of polyE-mediated inhibition has not been tested with knockin animals\", \"Whether polyE and C2A/CaM inhibitory mechanisms act sequentially or in parallel is unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A comprehensive variant study established that germline UNC13A coding variants cause a neurodevelopmental syndrome through three distinct mechanisms—reduced synaptic strength, gain-of-function hyperactivation, and impaired second-messenger regulation—broadening the spectrum of UNC13A-associated disease.\",\n      \"evidence\": \"Patient cohort exome sequencing; variant expression in mouse hippocampal neurons and C. elegans with electrophysiology\",\n      \"pmids\": [\"41125872\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype-phenotype correlation for milder variants is incomplete\", \"Whether compensatory mechanisms by other Munc13 isoforms modulate disease severity is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: the full-length atomic structure of Munc13-1 in its autoinhibited and active conformations, in vivo validation of the polyE autoinhibitory mechanism, therapeutic efficacy of UNC13A cryptic exon-targeting ASOs in ALS/FTD animal models, and how Munc13-1 nanocluster stoichiometry is dynamically regulated during plasticity.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No full-length high-resolution structure exists\", \"In vivo polyE knockin validation is lacking\", \"ASO rescue of UNC13A cryptic exon has not been tested in animal models of ALS/FTD in peer-reviewed studies\", \"How nanocluster copy number is regulated during plasticity is unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 6, 7, 17, 22]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 5, 14, 15, 24, 31, 33, 34]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [12, 32, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 14, 17, 22, 29]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 3, 11, 12, 13, 14, 20, 21, 23, 37, 38]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 5, 14, 15, 22, 33]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 7, 17, 18, 19, 22, 34]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [25, 26, 27, 35]}\n    ],\n    \"complexes\": [\n      \"SNARE complex (syntaxin-1/SNAP-25/VAMP2)\",\n      \"RIM1–Munc13-1–CAST active zone complex\"\n    ],\n    \"partners\": [\n      \"STX1A\",\n      \"RIMS1\",\n      \"RIMS2\",\n      \"UNC18A\",\n      \"CALM1\",\n      \"RIMBP2\",\n      \"ERC1\",\n      \"DOC2B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}