{"gene":"MFF","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2008,"finding":"MFF is a tail-anchored mitochondrial outer membrane protein that controls mitochondrial fission; it exists in separate ~200 kDa complexes from Fis1, and siRNA knockdown phenocopies Drp1 and Fis1 loss, causing mitochondrial network formation, delay in cytochrome c release, and inhibition of peroxisomal fission.","method":"siRNA knockdown, subcellular fractionation, gel filtration, fluorescence microscopy, apoptosis assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — original discovery paper with multiple orthogonal methods, >600 citations, replicated extensively","pmids":["18353969"],"is_preprint":false},{"year":2010,"finding":"Mff is an essential receptor for Drp1 recruitment to the mitochondrial outer membrane; Mff and Drp1 physically interact in vitro and in vivo (co-IP, pulldown), Mff knockdown releases Drp1 foci from mitochondria, and Mff overexpression drives mitochondrial fission independent of Fis1. A plasma membrane-targeted Mff mutant (CAAX) redirects Drp1 to the plasma membrane.","method":"Knockdown/overexpression, co-immunoprecipitation, in vitro pulldown, CAAX targeting assay, fluorescence microscopy","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal co-IP, in vitro interaction, gain/loss-of-function, >898 citations, replicated","pmids":["21149567"],"is_preprint":false},{"year":2013,"finding":"Fis1 and Mff both contribute to Drp1 recruitment and mitochondrial fission; Fis1-null and Mff-null cells show reduced Drp1 puncta on mitochondria, and MiD49 or MiD51 can each independently recruit Drp1 and mediate fission in the absence of both Fis1 and Mff.","method":"Gene knockout (Fis1-null, Mff-null, double null), immunofluorescence, Drp1 puncta quantification","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple null cell lines, orthogonal assays, >993 citations","pmids":["23283981"],"is_preprint":false},{"year":2013,"finding":"Mff functions in peroxisomal fission by localizing to peroxisomal membrane-constricted regions and recruiting DLP1 (Drp1) to peroxisomes; Mff knockdown abrogates DLP1 recruitment to peroxisomes. Mff and Pex11pβ interact in a DLP1-dependent manner to co-regulate peroxisomal fission.","method":"siRNA knockdown, immunofluorescence localization, co-immunoprecipitation, overexpression","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP and localization with functional rescue, single lab","pmids":["24167709"],"is_preprint":false},{"year":2015,"finding":"Mff selectively recruits higher-order oligomers of Drp1: assembly-deficient Drp1 mutants cannot bind Mff, whereas Drp1 mutants lacking the insert B region (which normally inhibits Mff-Drp1 interaction) form stable complexes with Mff. In contrast, MiD49/51 can recruit Drp1 dimers.","method":"Genetic and biochemical assays, recombinant protein binding, Drp1 assembly mutants","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 — reconstitution with mutants and biochemical assays, mechanistically rigorous","pmids":["26446846"],"is_preprint":false},{"year":2015,"finding":"Mff-deficient mice develop fatal dilated cardiomyopathy with reduced mitochondrial density, impaired respiratory chain activity, and increased mitophagy; concomitant deletion of the fusion gene Mfn1 completely rescues cardiac function and lifespan, demonstrating that Mff-dependent fission must be balanced against fusion for tissue integrity.","method":"Mouse knockout (Mff-null, Mff/Mfn1 double knockout), cardiac function assays, electron microscopy, metabolomics","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic epistasis with double knockout rescue, multiple phenotypic readouts","pmids":["26598616"],"is_preprint":false},{"year":2015,"finding":"The phosphorylation status of Drp1 at Ser637 is essential for its interaction with Mff; UV irradiation decreases Drp1-Ser637 phosphorylation and enhances Drp1-Mff interaction, driving mitochondrial fragmentation. Mff-mediated Drp1 recruitment does not require Bax.","method":"Co-immunoprecipitation, phosphomimetic/phospho-deficient mutants, siRNA, UV apoptosis model","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP with phospho-mutants, single lab","pmids":["26432782"],"is_preprint":false},{"year":2015,"finding":"Parkin mediates poly-ubiquitination of Mff at Lys251 upon mitochondrial depolarization; ubiquitinated Mff promotes association with the autophagic adaptor p62/SQSTM1, and Mff knockout impairs p62 and Parkin translocation to damaged mitochondria, linking Mff to mitophagy.","method":"Co-immunoprecipitation, ubiquitination assay, K251R point mutant, Mff knockout, fluorescence microscopy","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2-3 — site-specific ubiquitination with rescue by WT but not mutant, single lab","pmids":["26008206"],"is_preprint":false},{"year":2016,"finding":"Mff and Drp1 are components of the MARCH5/p97/Npl4 ubiquitin ligase complex; Mff and Drp1 knockouts reduce expression and increase ubiquitination of MiD49 and Mcl1 in a MARCH5-dependent manner, revealing that Mff negatively regulates MARCH5 E3 ligase activity toward specific OMM substrates.","method":"Gene knockout (Drp1-/-, Mff-/-, double KO with MARCH5-/-), co-immunoprecipitation, ubiquitination assay, protein stability assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — multiple KO combinations with biochemical epistasis, single lab","pmids":["27932492"],"is_preprint":false},{"year":2016,"finding":"MiD51 suppresses Mff-dependent enhancement of Drp1 GTPase activity; proximity biotin labeling shows close association between MiD51, Mff and Drp1, but not Fis1; and combined loss of MiD51 and Mff causes greater mitochondrial connectivity than loss of either alone.","method":"BioID proximity labeling, CRISPR/Cas9 knockout cell lines, Drp1 GTPase activity assay, electron microscopy","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 — GTPase assay, proximity labeling, and CRISPR knockouts, multiple orthogonal methods","pmids":["27076521"],"is_preprint":false},{"year":2017,"finding":"JNK pathway activation upregulates Mff expression/phosphorylation; elevated Mff drives excessive mitochondrial fission leading to mitochondrial apoptosis; DUSP1 (a JNK phosphatase) suppresses this pathway, and DUSP1 overexpression reduces Mff-mediated fission and protects against cardiac ischemia-reperfusion injury.","method":"Transgenic mouse model, siRNA knockdown, Western blot, mitochondrial morphology assay, apoptosis assay","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — in vivo and in vitro with pathway inhibition, single lab","pmids":["29149759"],"is_preprint":false},{"year":2017,"finding":"SENP3-mediated deSUMOylation of Drp1 selectively promotes Drp1 binding to Mff on the mitochondrial outer membrane; preventing Drp1 SUMOylation by mutating SUMO acceptor sites enhances Mff binding, while increasing Drp1 SUMOylation by SENP3 knockdown reduces Mff binding and stress-induced cytochrome c release. Directly tethering Drp1 to the OMM bypasses the need for Mff.","method":"Co-immunoprecipitation, SUMOylation site mutants, SENP3 overexpression/knockdown, cytochrome c release assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — mechanistically defined PTM–receptor interaction with multiple mutant controls, well replicated concept","pmids":["28262828"],"is_preprint":false},{"year":2018,"finding":"CK2α (casein kinase 2α), activated downstream of NR4A1 during cardiac microvascular ischemia-reperfusion, phosphorylates Mff, which enhances Drp1 translocation to mitochondria and causes fatal mitochondrial fission.","method":"NR4A1 knockout mice, CK2α inhibition, Western blot for phospho-Mff, mitochondrial morphology, apoptosis assay","journal":"Basic research in cardiology","confidence":"Medium","confidence_rationale":"Tier 2-3 — phosphorylation mechanism identified in vivo/in vitro, single lab","pmids":["29744594"],"is_preprint":false},{"year":2018,"finding":"MFF (isoforms MFF1 and MFF2) forms homo- and heterodimeric complexes with VDAC1 (voltage-dependent anion channel 1) using Arg225, Arg236, and Gln241 as key contact sites; disrupting this complex with a cell-permeable peptidomimetic acutely depolarizes mitochondria and triggers cell death selectively in tumor cells.","method":"Co-immunoprecipitation, mass spectrometry interactome, mutagenesis (Arg225, Arg236, Gln241), peptidomimetic disruption, patient-derived xenografts","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1-2 — complex identified by MS and co-IP with mutagenesis and functional validation in multiple tumor models","pmids":["31582380"],"is_preprint":false},{"year":2018,"finding":"MFF is regulated at the post-transcriptional level by the RNA-binding protein BRCA1 via transactivation of miR-593-5p, which targets the 3'UTR of MFF mRNA to suppress translation and attenuate mitochondrial fission and cisplatin sensitivity in tongue squamous cell carcinoma.","method":"3'UTR luciferase reporter, miR-593-5p overexpression/knockdown, BRCA1 transactivation assay, in vivo xenograft","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2-3 — 3'UTR reporter confirms direct targeting, in vivo validation, single lab","pmids":["25912308"],"is_preprint":false},{"year":2018,"finding":"MFF mediates mitochondrial fission by recruiting Drp1; Mff-deficient cardiac microvascular endothelial cells show reduced mitochondrial fission and inhibited mPTP opening via blockade of VDAC1 oligomerization and prevention of hexokinase 2 dissociation from mitochondria, reducing cardiolipin oxidation and cytochrome c release.","method":"Mff-deficient (Mffgt) mice and siRNA, mPTP opening assay, VDAC1 oligomerization assay, hexokinase 2 co-IP, mitochondrial ROS and cardiolipin oxidation measurement","journal":"Journal of the American Heart Association","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple biochemical assays in vivo and in vitro, single lab","pmids":["28288978"],"is_preprint":false},{"year":2018,"finding":"MFF is required for axonal mitochondrial size maintenance in cortical neurons; MFF downregulation increases presynaptic mitochondrial size, augments mitochondrial Ca2+ uptake during neurotransmission, and reduces presynaptic Ca2+ accumulation, decreasing neurotransmitter release and terminal axon branching.","method":"In utero electroporation, shRNA knockdown, live imaging, mitochondrial Ca2+ and membrane potential measurement, presynaptic release assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — in vivo and in vitro loss-of-function with mechanistic readouts, multiple orthogonal assays","pmids":["30479337"],"is_preprint":false},{"year":2019,"finding":"Parkin ubiquitinates Mff in a PINK1-dependent manner under non-stressed (basal) conditions to regulate constitutive Mff turnover; at least one additional ubiquitin ligase contributes to Mff proteostasis in the absence of Parkin.","method":"shRNA knockdown of Parkin/PINK1, ubiquitination assay, protein half-life measurement","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional ubiquitination assay, single lab","pmids":["31112535"],"is_preprint":false},{"year":2020,"finding":"Mff mediates formation of active MAVS clusters on the mitochondrial outer membrane, independent of mitochondrial fission and Drp1; under mitochondrial dysfunction, AMPK phosphorylates Mff, leading to disorganization of MAVS clusters and repression of antiviral signaling.","method":"Mff knockout cells, AMPK phosphorylation assay, MAVS oligomerization assay, innate immune reporter assay, confocal imaging","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal assays, knockout validation, in vivo and in vitro, single high-quality paper","pmids":["33177519"],"is_preprint":false},{"year":2021,"finding":"Mff is an oligomer (most likely a trimer) that dynamically associates through its C-terminal coiled coil (Kd ~10 µM); dynamic Mff oligomerization is required for Drp1 activation. Actin filaments enhance Mff-mediated Drp1 activation by lowering effective Mff concentration ~10-fold. TIRF microscopy shows Mff interacts with Drp1 on actin filaments in an oligomerization-dependent manner. In cells, oligomerization-defective Mff fails to rescue mitochondrial division, Drp1 recruitment, or peroxisome division in Mff-KO cells.","method":"In vitro reconstitution with purified proteins, GTPase activation assay, TIRF microscopy, Mff-KO rescue with oligomerization-defective mutants","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro with purified proteins, mutagenesis, and cell rescue experiments","pmids":["34347505"],"is_preprint":false},{"year":2021,"finding":"Protein kinase D (PKD) directly phosphorylates MFF specifically during mitosis; PKD-dependent MFF phosphorylation is required and sufficient for mitochondrial fission in mitotic (but not interphase) cells, and this fission is critical for chromosome segregation and cell survival by inhibiting adaptation of the mitotic checkpoint.","method":"In vitro kinase assay, phospho-specific antibodies, MFF phosphorylation-deficient mutants, live imaging, chromosome segregation assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro kinase assay plus cell-based rescue with phospho-mutants and functional readouts","pmids":["34010649"],"is_preprint":false},{"year":2021,"finding":"Mff preferentially binds higher-order Drp1 oligomers and only recruits active forms of Drp1, whereas MIEFs bind a wider range including lower oligomeric states and inactive Drp1. MIEFs serve as a platform facilitating Drp1 binding to Mff; loss of MIEFs severely impairs the Drp1-Mff interaction.","method":"In vivo chemical crosslinking, co-immunoprecipitation, assembly-deficient and GTPase-deficient Drp1 mutants, triple (Mff/MIEF1/MIEF2) knockout cells","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — in vivo crosslinking and co-IP with multiple mutants, single lab","pmids":["34805137"],"is_preprint":false},{"year":2021,"finding":"In an OGD/ischemia model, Mff primes Drp1 binding to Bcl-xL at the mitochondrial outer membrane; Mff and Bcl-xL interact directly through their transmembrane domains independent of Drp1. SENP3-mediated Drp1 deSUMOylation promotes the Drp1-Bcl-xL interaction and ischemia-induced cell death.","method":"Co-immunoprecipitation in vivo and in vitro, OGD model, SENP3 knockdown/overexpression, Bcl-xL transmembrane mutant","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP with multiple conditions and mutants, single lab","pmids":["34722538"],"is_preprint":false},{"year":2022,"finding":"HCMV vMIA inhibits MAVS oligomerization at peroxisomes in an MFF-dependent manner; vMIA interacts with MAVS at peroxisomes and requires MFF for peroxisomal fragmentation, but MFF is dispensable for vMIA-mediated inhibition of mitochondrial MAVS signaling.","method":"siRNA knockdown of MFF, MAVS oligomerization assay, immunofluorescence, co-immunoprecipitation, peroxisome morphology","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — mechanistic distinction between organelle-specific MFF roles, single lab","pmids":["35445031"],"is_preprint":false},{"year":2023,"finding":"CPT1A promotes succinylation of MFF at Lys302 through its lysine succinyltransferase activity; this succinylation protects MFF from Parkin-mediated ubiquitin-proteasomal degradation, stabilizing MFF to promote mitochondrial fission and ovarian cancer cell growth.","method":"Mass spectrometry, site-directed mutagenesis (K302R), co-immunoprecipitation, ubiquitination assay, in vivo xenograft","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 1-2 — PTM site identified by MS, confirmed by mutagenesis and functional assay, single lab","pmids":["37291333"],"is_preprint":false},{"year":2024,"finding":"FMRP granules are recruited to mitochondrial fission sites in axons and dendrites; FMRP promotes local translation of MFF at the mitochondrial midzone via ribosome-rich granules, specifically enabling replicative fission. Loss of FMRP dysregulates MFF local translation, increases peripheral fission, and disrupts mitochondrial nucleoid distribution.","method":"Cryo-electron tomography, real-time translation imaging (SunTag), FMRP conditional KO, live imaging, Rab7 GTPase manipulation","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-ET structural evidence, real-time translation imaging, genetic KO with defined phenotype, multiple orthogonal methods","pmids":["39548330"],"is_preprint":false},{"year":2024,"finding":"MFF is SUMOylated at Lys151; AMPK-mediated phosphorylation of MFF enhances its SUMOylation. MFF SUMOylation regulates MiD49/51 binding to MFF within trimeric DRP1-MiD-MFF fission complexes, and non-SUMOylatable MFF K151R impairs CCCP-induced mitochondrial fragmentation in MFF-KO MEFs.","method":"SUMO site identification, phosphomimetic/phospho-deficient mutants, K151R non-SUMOylatable mutant rescue, MFF-KO MEFs, CCCP stress assay","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1-2 — PTM site defined with mutagenesis and functional rescue, mechanistically linked to complex assembly","pmids":["39365854"],"is_preprint":false},{"year":2024,"finding":"Alternative splicing of Mff exon 6 insertion (just after the AMPK phosphorylation site) reduces AMPK-mediated Mff phosphorylation and impairs both mitochondrial fission and MAVS-mediated antiviral response in a phosphorylation-independent manner; tissue-specific splicing patterns regulate Mff function.","method":"Mff knockout MEFs rescued with single splice isoforms, AMPK phosphorylation assay, mitochondrial morphology, innate immune reporter assay","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 — isoform rescue in KO cells with phosphorylation and functional assays, single lab","pmids":["39293584"],"is_preprint":false},{"year":2025,"finding":"TRIM21 mediates ubiquitination and proteasomal degradation of MFF; ciprofloxacin upregulates TRIM21, reducing MFF levels and causing mitochondrial dysfunction and trophoblast cell senescence leading to miscarriage.","method":"Co-immunoprecipitation, ubiquitination assay, TRIM21 knockdown/overexpression, mouse model, trophoblast cell line","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — ubiquitination mechanism with in vivo validation, single lab, new finding","pmids":["41650744"],"is_preprint":false},{"year":2026,"finding":"MFF traffics between mitochondria and melanosomes and localizes to melanosome fission events; MFF downregulation causes melanosome enlargement, intracellular melanin accumulation, and increased lumenal catabolism independent of Drp1. MFF interacts with regulators of the ARP2/3 complex; actin filaments accumulate at MFF-enriched membrane constriction sites between melanosomes, and silencing ARP2/3 subunits phenocopies MFF loss, revealing an extramitochondrial MFF function in actin-dependent melanosome fission.","method":"MFF knockdown, live imaging, co-immunoprecipitation with ARP2/3 regulators, actin staining, ARP2/3 subunit knockdown, melanosome morphology and melanin quantification","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods, novel extramitochondrial function, single lab","pmids":["41832149"],"is_preprint":false}],"current_model":"MFF is a tail-anchored mitochondrial outer membrane protein that serves as the primary receptor recruiting cytosolic Drp1 oligomers to drive mitochondrial (and peroxisomal) fission; it forms oligomers through its C-terminal coiled coil, and actin filaments enhance Mff-mediated Drp1 GTPase activation. MFF activity is regulated by multiple post-translational modifications—AMPK-mediated phosphorylation (enhanced by kinases including JNK and CK2α, suppressed by phosphatases like DUSP1), SUMOylation at Lys151 (which controls MiD49/51 binding and complex composition), succinylation at Lys302 (protecting it from Parkin-mediated degradation), and Parkin-mediated ubiquitination (for constitutive turnover and mitophagy). MFF selectively binds higher-order Drp1 oligomers (unlike MiD49/51 which recruit dimers), and Drp1 deSUMOylation by SENP3 enhances this interaction. Beyond fission, MFF independently promotes active MAVS cluster formation for antiviral immunity, forms complexes with VDAC1 to regulate mitochondrial outer membrane permeability, and mediates actin-dependent melanosome fission via ARP2/3 complex interactions; additionally, local MFF translation in neurons is controlled by FMRP granules at fission sites to spatially regulate mitochondrial division."},"narrative":{"teleology":[{"year":2008,"claim":"MFF was identified as a novel mitochondrial fission factor, resolving the question of whether mammalian fission required additional receptors beyond Fis1: MFF knockdown phenocopied Drp1 loss, establishing it as a core fission component.","evidence":"siRNA knockdown with subcellular fractionation, gel filtration, and fluorescence microscopy in mammalian cells","pmids":["18353969"],"confidence":"High","gaps":["Direct physical interaction with Drp1 not yet demonstrated","Mechanism of MFF action at the membrane unknown"]},{"year":2010,"claim":"The key question of whether MFF directly recruits Drp1 was answered: MFF physically binds Drp1 in vitro and in vivo, and plasma membrane-retargeted MFF redirects Drp1, establishing MFF as a bona fide Drp1 receptor independent of Fis1.","evidence":"Reciprocal co-IP, in vitro pulldown, CAAX plasma membrane targeting, gain/loss-of-function","pmids":["21149567"],"confidence":"High","gaps":["Structural basis of MFF-Drp1 interaction unresolved","Whether MFF distinguishes Drp1 oligomeric states unknown"]},{"year":2013,"claim":"The question of receptor redundancy was addressed: MiD49/51 can independently recruit Drp1 in Mff-null/Fis1-null cells, and MFF also functions in peroxisomal fission by recruiting Drp1 to peroxisomes in cooperation with Pex11pβ.","evidence":"Fis1-null, Mff-null, and double-null cell lines; Drp1 puncta quantification; co-IP of MFF-Pex11pβ","pmids":["23283981","24167709"],"confidence":"High","gaps":["Relative contributions of MFF versus MiD49/51 in different tissues unclear","Pex11pβ-MFF interaction not reconstituted in vitro"]},{"year":2015,"claim":"Multiple advances resolved how MFF selectivity, regulation, and physiological importance operate: MFF selectively binds higher-order Drp1 oligomers (unlike MiD49/51 which recruit dimers), Drp1 Ser637 dephosphorylation enhances MFF binding, Parkin ubiquitinates MFF at Lys251 to link it to mitophagy, and Mff-knockout mice develop fatal dilated cardiomyopathy rescued by concomitant Mfn1 deletion.","evidence":"Recombinant protein binding with assembly mutants; phosphomimetic/phospho-deficient Drp1 mutants and co-IP; ubiquitination assay with K251R mutant; Mff-null and Mff/Mfn1 double-knockout mice with cardiac phenotyping","pmids":["26446846","26432782","26008206","26598616"],"confidence":"High","gaps":["Structural basis of oligomer selectivity not defined","Identity of kinase/phosphatase for Drp1 Ser637 in this context not fully resolved","Whether additional E3 ligases ubiquitinate MFF unknown"]},{"year":2016,"claim":"MFF was placed within a broader regulatory network: MiD51 suppresses MFF-dependent Drp1 GTPase activation, and MFF/Drp1 negatively regulate MARCH5 E3 ligase activity toward OMM substrates including MiD49 and Mcl1.","evidence":"BioID proximity labeling, CRISPR knockouts, Drp1 GTPase assay; multiple KO combinations with ubiquitination and stability assays","pmids":["27076521","27932492"],"confidence":"High","gaps":["How MFF inhibits MARCH5 mechanistically is unclear","Whether MiD51-MFF interplay is tissue-specific not tested"]},{"year":2017,"claim":"Post-translational control of the MFF-Drp1 axis was expanded: SENP3-mediated deSUMOylation of Drp1 selectively promotes Drp1 binding to MFF, and JNK-mediated MFF phosphorylation/upregulation drives pathological fission counteracted by DUSP1.","evidence":"SUMO site mutants with co-IP; SENP3 knockdown/overexpression; transgenic mouse cardiac ischemia-reperfusion model with DUSP1","pmids":["28262828","29149759"],"confidence":"High","gaps":["Direct phosphorylation sites on MFF by JNK not mapped","Whether SENP3-Drp1-MFF axis operates in all tissues unknown"]},{"year":2018,"claim":"MFF was shown to function beyond simple fission: it forms complexes with VDAC1 to regulate mitochondrial outer membrane permeability, controls neuronal mitochondrial size and presynaptic calcium/neurotransmitter release, and CK2α was identified as an upstream kinase phosphorylating MFF during cardiac ischemia.","evidence":"MFF-VDAC1 co-IP with mutagenesis and peptidomimetic disruption; in utero electroporation with shRNA and Ca2+ imaging in neurons; NR4A1 KO mice with CK2α inhibition","pmids":["31582380","30479337","29744594"],"confidence":"High","gaps":["Structural detail of MFF-VDAC1 complex lacking","Whether MFF-VDAC1 interaction is relevant to non-tumor physiology untested","Specific phosphorylation sites for CK2α on MFF not mapped"]},{"year":2020,"claim":"An entirely fission-independent function was established: MFF promotes active MAVS cluster formation on mitochondria for antiviral signaling, and AMPK phosphorylation of MFF under metabolic stress disorganizes MAVS clusters to suppress innate immunity.","evidence":"Mff knockout cells, AMPK phosphorylation assay, MAVS oligomerization and innate immune reporter assays","pmids":["33177519"],"confidence":"High","gaps":["Structural basis of MFF-MAVS interaction unknown","Whether MFF organizes other signaling platforms not explored"]},{"year":2021,"claim":"The biophysical mechanism of MFF was resolved: MFF is an oligomer (likely trimer) whose dynamic self-assembly through its coiled coil is essential for Drp1 activation, and actin filaments enhance this by lowering the effective MFF concentration ~10-fold; separately, PKD was identified as the mitosis-specific MFF kinase required for chromosome segregation.","evidence":"In vitro reconstitution with purified proteins, TIRF microscopy, GTPase assay, Mff-KO rescue with oligomerization-defective mutants; in vitro kinase assay with phospho-mutant rescue and chromosome segregation assays","pmids":["34347505","34010649"],"confidence":"High","gaps":["Atomic structure of MFF oligomer not determined","How actin filaments are positioned at fission sites relative to MFF in vivo unclear","Whether PKD phosphorylation affects MFF oligomerization untested"]},{"year":2023,"claim":"A novel stabilizing modification was identified: CPT1A-mediated succinylation of MFF at Lys302 protects MFF from Parkin-mediated ubiquitin-proteasomal degradation, linking metabolic rewiring to fission control in cancer.","evidence":"Mass spectrometry identification of succinylation site, K302R mutagenesis, ubiquitination assay, in vivo xenograft","pmids":["37291333"],"confidence":"Medium","gaps":["Whether succinylation-ubiquitination crosstalk on MFF operates in non-cancer contexts unknown","Desuccinylase for Lys302 not identified"]},{"year":2024,"claim":"Two regulatory layers were defined: AMPK-dependent phosphorylation enhances MFF SUMOylation at Lys151, which controls MiD49/51 binding within trimeric DRP1-MiD-MFF complexes; and FMRP granules control local MFF translation at mitochondrial fission sites in neurons to spatially regulate replicative versus peripheral fission.","evidence":"SUMO site ID with K151R rescue in MFF-KO MEFs; cryo-ET, real-time SunTag translation imaging, FMRP conditional KO in neurons; isoform rescue with splice variants in KO MEFs","pmids":["39365854","39548330","39293584"],"confidence":"High","gaps":["How SUMOylation structurally alters MFF-MiD binding not resolved","Whether FMRP-dependent local translation of MFF occurs outside neurons unknown","Functional significance of most MFF splice isoforms untested in vivo"]},{"year":2025,"claim":"An additional E3 ubiquitin ligase, TRIM21, was identified as mediating MFF degradation, linking MFF turnover to trophoblast senescence and miscarriage; separately, MFF was shown to traffic to melanosomes and drive actin/ARP2/3-dependent melanosome fission independent of Drp1.","evidence":"TRIM21 co-IP and ubiquitination assay with in vivo mouse model; MFF knockdown with live imaging, ARP2/3 subunit knockdown, and melanosome morphology in melanocytes","pmids":["41650744","41832149"],"confidence":"Medium","gaps":["TRIM21-MFF ubiquitination sites not mapped","Whether MFF-ARP2/3 interaction is direct or mediated by adaptors unclear","Mechanism of MFF trafficking from mitochondria to melanosomes unknown"]},{"year":null,"claim":"Key unresolved questions include the atomic structure of MFF (as monomer and oligomer), the structural basis of its selective recognition of higher-order Drp1 oligomers, how MFF coordinates its dual fission-dependent and fission-independent functions (MAVS signaling, VDAC1 regulation, melanosome fission), and the full landscape of tissue-specific splice isoform functions in vivo.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of MFF available","Mechanism of MFF trafficking between organelles unknown","Relative in vivo contributions of multiple MFF kinases and E3 ligases not systematically compared"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,4,19]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,18,26]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,5,16,19]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]},{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[3,23]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[29]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,1,5,19,20]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[18,23,27]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[7,15]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[7,17]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[20]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[17,24,28]}],"complexes":["DRP1-MFF fission complex","DRP1-MiD49/51-MFF trimeric complex","MFF-VDAC1 complex"],"partners":["DNM1L","VDAC1","MAVS","PRKN","MIEF1","MIEF2","PRKAA1","PRKD1"],"other_free_text":[]},"mechanistic_narrative":"MFF is a tail-anchored outer mitochondrial membrane protein that functions as the primary receptor for recruiting higher-order Drp1 oligomers to drive mitochondrial and peroxisomal fission, with its activity amplified by actin filaments and dependent on its own oligomerization through a C-terminal coiled coil [PMID:18353969, PMID:21149567, PMID:34347505]. MFF activity is regulated by a convergence of post-translational modifications: AMPK, PKD, JNK/CK2α-mediated phosphorylation promotes Drp1 recruitment and fission; SUMOylation at Lys151 controls MiD49/51 binding within trimeric fission complexes; succinylation at Lys302 protects MFF from Parkin-mediated degradation; and ubiquitination by Parkin or TRIM21 directs its constitutive turnover [PMID:39365854, PMID:34010649, PMID:37291333, PMID:31112535, PMID:41650744]. Beyond organelle division, MFF independently promotes active MAVS cluster formation on the mitochondrial surface for innate antiviral signaling, forms complexes with VDAC1 to regulate outer membrane permeability, and mediates ARP2/3-dependent actin-based melanosome fission [PMID:33177519, PMID:31582380, PMID:41832149]. In neurons, local MFF translation at mitochondrial fission sites is spatially controlled by FMRP-containing RNA granules, and Mff-deficient mice develop fatal dilated cardiomyopathy rescued by concomitant loss of the fusion factor Mfn1 [PMID:39548330, PMID:26598616]."},"prefetch_data":{"uniprot":{"accession":"Q9GZY8","full_name":"Mitochondrial fission factor","aliases":[],"length_aa":342,"mass_kda":38.5,"function":"Plays a role in mitochondrial and peroxisomal fission (PubMed:18353969, PubMed:23530241, PubMed:24196833). Promotes the recruitment and association of the fission mediator dynamin-related protein 1 (DNM1L) to the mitochondrial surface (PubMed:23530241). 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all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MFF"},"hgnc":{"alias_symbol":["GL004"],"prev_symbol":["C2orf33"]},"alphafold":{"accession":"Q9GZY8","domains":[{"cath_id":"1.20.5","chopping":"292-342","consensus_level":"medium","plddt":87.2114,"start":292,"end":342}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9GZY8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9GZY8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9GZY8-F1-predicted_aligned_error_v6.png","plddt_mean":63.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MFF","jax_strain_url":"https://www.jax.org/strain/search?query=MFF"},"sequence":{"accession":"Q9GZY8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9GZY8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9GZY8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9GZY8"}},"corpus_meta":[{"pmid":"23283981","id":"PMC_23283981","title":"Fis1, Mff, MiD49, and MiD51 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migration.","date":"2024","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38940352","citation_count":0,"is_preprint":false},{"pmid":"41650744","id":"PMC_41650744","title":"Environmental ciprofloxacin triggers pregnancy loss: senescence-driven miscarriage via TRIM21-mediated MFF degradation.","date":"2026","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/41650744","citation_count":0,"is_preprint":false},{"pmid":"40589089","id":"PMC_40589089","title":"MFF-HPO: Protein-Phenotype Associations Prediction Based on Sequence Using Multi-Feature Fusion.","date":"2025","source":"Journal of computational biology : a journal of computational molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40589089","citation_count":0,"is_preprint":false},{"pmid":"41447962","id":"PMC_41447962","title":"Anti-inflammatory gut immune modulation induced by direct-fed endospores of bacteriostatic lipopeptide-producing Bacillus velezensis MFF 2.2 and B. subtilis TC12 in BALB/c mice: A first step toward a probiotic additive to prevent post-weaning diarrhea.","date":"2025","source":"Research in veterinary science","url":"https://pubmed.ncbi.nlm.nih.gov/41447962","citation_count":0,"is_preprint":false},{"pmid":"36946373","id":"PMC_36946373","title":"Bilateral plaque like macular atrophy and pigmentary retinopathy in an infant with a missense mutation in the MFF gene.","date":"2023","source":"Ophthalmic genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36946373","citation_count":0,"is_preprint":false},{"pmid":"41549306","id":"PMC_41549306","title":"Targeting MFF succinylation: a novel therapeutic strategy for premature ovarian insufficiency by restoring mitochondrial dynamics in granulosa cells.","date":"2026","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/41549306","citation_count":0,"is_preprint":false},{"pmid":"41828350","id":"PMC_41828350","title":"MFF-AE: Enhanced Quality Control for Proteomics Mass Spectrometry Data via Multi-Scale Feature Fusion.","date":"2026","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41828350","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.11.25.690461","title":"Illuminating the Role of Asymmetric Mitochondrial Fission on Beta-Cell Health","date":"2025-11-28","source":"bioRxiv","url":"https://doi.org/10.1101/2025.11.25.690461","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.08.18.670752","title":"The Cancer/Testis Antigen FATE1 Antagonizes Fission and Preserves Mitochondrial Network Integrity under Cytotoxic Stress","date":"2025-08-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.18.670752","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.10.27.684912","title":"Systems modeling of mitochondrial dynamics in different exercise regimes","date":"2025-10-28","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.27.684912","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.18.643978","title":"Scale drop disease virus (SDDV) triggering ferroptosis both <i>in vivo</i> and <i>in vitro</i> facilitates virus infection via targeting transferrin receptor 1 (TfR1)","date":"2025-03-18","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.18.643978","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.25.620016","title":"Snapshots of Mitochondrial Fission Imaged by Cryo-Scanning Transmission Electron Tomography","date":"2024-10-25","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.25.620016","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.07.631801","title":"Fis1 is required for the development of the dendritic mitochondrial network in pyramidal cortical neurons","date":"2025-01-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.07.631801","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.16.628220","title":"Maladaptive response of an endemic California oak to climatic warming is previewed by interannual variation in growth and survival","date":"2024-12-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.16.628220","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.06.05.597619","title":"Depletion of chemoresponsive mitochondrial fission mediator DRP1 does not mitigate sarcoma resistance","date":"2024-06-08","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.05.597619","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.01.601612","title":"Microglia Morphological Response to Mesenchymal Stromal Cell Extracellular Vesicles Demonstrates EV Therapeutic Potential for Modulating Neuroinflammation","date":"2024-07-03","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.01.601612","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45720,"output_tokens":7310,"usd":0.123405},"stage2":{"model":"claude-opus-4-6","input_tokens":11006,"output_tokens":3880,"usd":0.228045},"total_usd":0.35145,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"MFF is a tail-anchored mitochondrial outer membrane protein that controls mitochondrial fission; it exists in separate ~200 kDa complexes from Fis1, and siRNA knockdown phenocopies Drp1 and Fis1 loss, causing mitochondrial network formation, delay in cytochrome c release, and inhibition of peroxisomal fission.\",\n      \"method\": \"siRNA knockdown, subcellular fractionation, gel filtration, fluorescence microscopy, apoptosis assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — original discovery paper with multiple orthogonal methods, >600 citations, replicated extensively\",\n      \"pmids\": [\"18353969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Mff is an essential receptor for Drp1 recruitment to the mitochondrial outer membrane; Mff and Drp1 physically interact in vitro and in vivo (co-IP, pulldown), Mff knockdown releases Drp1 foci from mitochondria, and Mff overexpression drives mitochondrial fission independent of Fis1. A plasma membrane-targeted Mff mutant (CAAX) redirects Drp1 to the plasma membrane.\",\n      \"method\": \"Knockdown/overexpression, co-immunoprecipitation, in vitro pulldown, CAAX targeting assay, fluorescence microscopy\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal co-IP, in vitro interaction, gain/loss-of-function, >898 citations, replicated\",\n      \"pmids\": [\"21149567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Fis1 and Mff both contribute to Drp1 recruitment and mitochondrial fission; Fis1-null and Mff-null cells show reduced Drp1 puncta on mitochondria, and MiD49 or MiD51 can each independently recruit Drp1 and mediate fission in the absence of both Fis1 and Mff.\",\n      \"method\": \"Gene knockout (Fis1-null, Mff-null, double null), immunofluorescence, Drp1 puncta quantification\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple null cell lines, orthogonal assays, >993 citations\",\n      \"pmids\": [\"23283981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mff functions in peroxisomal fission by localizing to peroxisomal membrane-constricted regions and recruiting DLP1 (Drp1) to peroxisomes; Mff knockdown abrogates DLP1 recruitment to peroxisomes. Mff and Pex11pβ interact in a DLP1-dependent manner to co-regulate peroxisomal fission.\",\n      \"method\": \"siRNA knockdown, immunofluorescence localization, co-immunoprecipitation, overexpression\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP and localization with functional rescue, single lab\",\n      \"pmids\": [\"24167709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mff selectively recruits higher-order oligomers of Drp1: assembly-deficient Drp1 mutants cannot bind Mff, whereas Drp1 mutants lacking the insert B region (which normally inhibits Mff-Drp1 interaction) form stable complexes with Mff. In contrast, MiD49/51 can recruit Drp1 dimers.\",\n      \"method\": \"Genetic and biochemical assays, recombinant protein binding, Drp1 assembly mutants\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstitution with mutants and biochemical assays, mechanistically rigorous\",\n      \"pmids\": [\"26446846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mff-deficient mice develop fatal dilated cardiomyopathy with reduced mitochondrial density, impaired respiratory chain activity, and increased mitophagy; concomitant deletion of the fusion gene Mfn1 completely rescues cardiac function and lifespan, demonstrating that Mff-dependent fission must be balanced against fusion for tissue integrity.\",\n      \"method\": \"Mouse knockout (Mff-null, Mff/Mfn1 double knockout), cardiac function assays, electron microscopy, metabolomics\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic epistasis with double knockout rescue, multiple phenotypic readouts\",\n      \"pmids\": [\"26598616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The phosphorylation status of Drp1 at Ser637 is essential for its interaction with Mff; UV irradiation decreases Drp1-Ser637 phosphorylation and enhances Drp1-Mff interaction, driving mitochondrial fragmentation. Mff-mediated Drp1 recruitment does not require Bax.\",\n      \"method\": \"Co-immunoprecipitation, phosphomimetic/phospho-deficient mutants, siRNA, UV apoptosis model\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP with phospho-mutants, single lab\",\n      \"pmids\": [\"26432782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Parkin mediates poly-ubiquitination of Mff at Lys251 upon mitochondrial depolarization; ubiquitinated Mff promotes association with the autophagic adaptor p62/SQSTM1, and Mff knockout impairs p62 and Parkin translocation to damaged mitochondria, linking Mff to mitophagy.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, K251R point mutant, Mff knockout, fluorescence microscopy\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — site-specific ubiquitination with rescue by WT but not mutant, single lab\",\n      \"pmids\": [\"26008206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Mff and Drp1 are components of the MARCH5/p97/Npl4 ubiquitin ligase complex; Mff and Drp1 knockouts reduce expression and increase ubiquitination of MiD49 and Mcl1 in a MARCH5-dependent manner, revealing that Mff negatively regulates MARCH5 E3 ligase activity toward specific OMM substrates.\",\n      \"method\": \"Gene knockout (Drp1-/-, Mff-/-, double KO with MARCH5-/-), co-immunoprecipitation, ubiquitination assay, protein stability assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple KO combinations with biochemical epistasis, single lab\",\n      \"pmids\": [\"27932492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MiD51 suppresses Mff-dependent enhancement of Drp1 GTPase activity; proximity biotin labeling shows close association between MiD51, Mff and Drp1, but not Fis1; and combined loss of MiD51 and Mff causes greater mitochondrial connectivity than loss of either alone.\",\n      \"method\": \"BioID proximity labeling, CRISPR/Cas9 knockout cell lines, Drp1 GTPase activity assay, electron microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — GTPase assay, proximity labeling, and CRISPR knockouts, multiple orthogonal methods\",\n      \"pmids\": [\"27076521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"JNK pathway activation upregulates Mff expression/phosphorylation; elevated Mff drives excessive mitochondrial fission leading to mitochondrial apoptosis; DUSP1 (a JNK phosphatase) suppresses this pathway, and DUSP1 overexpression reduces Mff-mediated fission and protects against cardiac ischemia-reperfusion injury.\",\n      \"method\": \"Transgenic mouse model, siRNA knockdown, Western blot, mitochondrial morphology assay, apoptosis assay\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — in vivo and in vitro with pathway inhibition, single lab\",\n      \"pmids\": [\"29149759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SENP3-mediated deSUMOylation of Drp1 selectively promotes Drp1 binding to Mff on the mitochondrial outer membrane; preventing Drp1 SUMOylation by mutating SUMO acceptor sites enhances Mff binding, while increasing Drp1 SUMOylation by SENP3 knockdown reduces Mff binding and stress-induced cytochrome c release. Directly tethering Drp1 to the OMM bypasses the need for Mff.\",\n      \"method\": \"Co-immunoprecipitation, SUMOylation site mutants, SENP3 overexpression/knockdown, cytochrome c release assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mechanistically defined PTM–receptor interaction with multiple mutant controls, well replicated concept\",\n      \"pmids\": [\"28262828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CK2α (casein kinase 2α), activated downstream of NR4A1 during cardiac microvascular ischemia-reperfusion, phosphorylates Mff, which enhances Drp1 translocation to mitochondria and causes fatal mitochondrial fission.\",\n      \"method\": \"NR4A1 knockout mice, CK2α inhibition, Western blot for phospho-Mff, mitochondrial morphology, apoptosis assay\",\n      \"journal\": \"Basic research in cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — phosphorylation mechanism identified in vivo/in vitro, single lab\",\n      \"pmids\": [\"29744594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MFF (isoforms MFF1 and MFF2) forms homo- and heterodimeric complexes with VDAC1 (voltage-dependent anion channel 1) using Arg225, Arg236, and Gln241 as key contact sites; disrupting this complex with a cell-permeable peptidomimetic acutely depolarizes mitochondria and triggers cell death selectively in tumor cells.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry interactome, mutagenesis (Arg225, Arg236, Gln241), peptidomimetic disruption, patient-derived xenografts\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — complex identified by MS and co-IP with mutagenesis and functional validation in multiple tumor models\",\n      \"pmids\": [\"31582380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MFF is regulated at the post-transcriptional level by the RNA-binding protein BRCA1 via transactivation of miR-593-5p, which targets the 3'UTR of MFF mRNA to suppress translation and attenuate mitochondrial fission and cisplatin sensitivity in tongue squamous cell carcinoma.\",\n      \"method\": \"3'UTR luciferase reporter, miR-593-5p overexpression/knockdown, BRCA1 transactivation assay, in vivo xenograft\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — 3'UTR reporter confirms direct targeting, in vivo validation, single lab\",\n      \"pmids\": [\"25912308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MFF mediates mitochondrial fission by recruiting Drp1; Mff-deficient cardiac microvascular endothelial cells show reduced mitochondrial fission and inhibited mPTP opening via blockade of VDAC1 oligomerization and prevention of hexokinase 2 dissociation from mitochondria, reducing cardiolipin oxidation and cytochrome c release.\",\n      \"method\": \"Mff-deficient (Mffgt) mice and siRNA, mPTP opening assay, VDAC1 oligomerization assay, hexokinase 2 co-IP, mitochondrial ROS and cardiolipin oxidation measurement\",\n      \"journal\": \"Journal of the American Heart Association\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple biochemical assays in vivo and in vitro, single lab\",\n      \"pmids\": [\"28288978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MFF is required for axonal mitochondrial size maintenance in cortical neurons; MFF downregulation increases presynaptic mitochondrial size, augments mitochondrial Ca2+ uptake during neurotransmission, and reduces presynaptic Ca2+ accumulation, decreasing neurotransmitter release and terminal axon branching.\",\n      \"method\": \"In utero electroporation, shRNA knockdown, live imaging, mitochondrial Ca2+ and membrane potential measurement, presynaptic release assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo and in vitro loss-of-function with mechanistic readouts, multiple orthogonal assays\",\n      \"pmids\": [\"30479337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Parkin ubiquitinates Mff in a PINK1-dependent manner under non-stressed (basal) conditions to regulate constitutive Mff turnover; at least one additional ubiquitin ligase contributes to Mff proteostasis in the absence of Parkin.\",\n      \"method\": \"shRNA knockdown of Parkin/PINK1, ubiquitination assay, protein half-life measurement\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional ubiquitination assay, single lab\",\n      \"pmids\": [\"31112535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mff mediates formation of active MAVS clusters on the mitochondrial outer membrane, independent of mitochondrial fission and Drp1; under mitochondrial dysfunction, AMPK phosphorylates Mff, leading to disorganization of MAVS clusters and repression of antiviral signaling.\",\n      \"method\": \"Mff knockout cells, AMPK phosphorylation assay, MAVS oligomerization assay, innate immune reporter assay, confocal imaging\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays, knockout validation, in vivo and in vitro, single high-quality paper\",\n      \"pmids\": [\"33177519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mff is an oligomer (most likely a trimer) that dynamically associates through its C-terminal coiled coil (Kd ~10 µM); dynamic Mff oligomerization is required for Drp1 activation. Actin filaments enhance Mff-mediated Drp1 activation by lowering effective Mff concentration ~10-fold. TIRF microscopy shows Mff interacts with Drp1 on actin filaments in an oligomerization-dependent manner. In cells, oligomerization-defective Mff fails to rescue mitochondrial division, Drp1 recruitment, or peroxisome division in Mff-KO cells.\",\n      \"method\": \"In vitro reconstitution with purified proteins, GTPase activation assay, TIRF microscopy, Mff-KO rescue with oligomerization-defective mutants\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro with purified proteins, mutagenesis, and cell rescue experiments\",\n      \"pmids\": [\"34347505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Protein kinase D (PKD) directly phosphorylates MFF specifically during mitosis; PKD-dependent MFF phosphorylation is required and sufficient for mitochondrial fission in mitotic (but not interphase) cells, and this fission is critical for chromosome segregation and cell survival by inhibiting adaptation of the mitotic checkpoint.\",\n      \"method\": \"In vitro kinase assay, phospho-specific antibodies, MFF phosphorylation-deficient mutants, live imaging, chromosome segregation assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro kinase assay plus cell-based rescue with phospho-mutants and functional readouts\",\n      \"pmids\": [\"34010649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mff preferentially binds higher-order Drp1 oligomers and only recruits active forms of Drp1, whereas MIEFs bind a wider range including lower oligomeric states and inactive Drp1. MIEFs serve as a platform facilitating Drp1 binding to Mff; loss of MIEFs severely impairs the Drp1-Mff interaction.\",\n      \"method\": \"In vivo chemical crosslinking, co-immunoprecipitation, assembly-deficient and GTPase-deficient Drp1 mutants, triple (Mff/MIEF1/MIEF2) knockout cells\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — in vivo crosslinking and co-IP with multiple mutants, single lab\",\n      \"pmids\": [\"34805137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In an OGD/ischemia model, Mff primes Drp1 binding to Bcl-xL at the mitochondrial outer membrane; Mff and Bcl-xL interact directly through their transmembrane domains independent of Drp1. SENP3-mediated Drp1 deSUMOylation promotes the Drp1-Bcl-xL interaction and ischemia-induced cell death.\",\n      \"method\": \"Co-immunoprecipitation in vivo and in vitro, OGD model, SENP3 knockdown/overexpression, Bcl-xL transmembrane mutant\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP with multiple conditions and mutants, single lab\",\n      \"pmids\": [\"34722538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HCMV vMIA inhibits MAVS oligomerization at peroxisomes in an MFF-dependent manner; vMIA interacts with MAVS at peroxisomes and requires MFF for peroxisomal fragmentation, but MFF is dispensable for vMIA-mediated inhibition of mitochondrial MAVS signaling.\",\n      \"method\": \"siRNA knockdown of MFF, MAVS oligomerization assay, immunofluorescence, co-immunoprecipitation, peroxisome morphology\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — mechanistic distinction between organelle-specific MFF roles, single lab\",\n      \"pmids\": [\"35445031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CPT1A promotes succinylation of MFF at Lys302 through its lysine succinyltransferase activity; this succinylation protects MFF from Parkin-mediated ubiquitin-proteasomal degradation, stabilizing MFF to promote mitochondrial fission and ovarian cancer cell growth.\",\n      \"method\": \"Mass spectrometry, site-directed mutagenesis (K302R), co-immunoprecipitation, ubiquitination assay, in vivo xenograft\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — PTM site identified by MS, confirmed by mutagenesis and functional assay, single lab\",\n      \"pmids\": [\"37291333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FMRP granules are recruited to mitochondrial fission sites in axons and dendrites; FMRP promotes local translation of MFF at the mitochondrial midzone via ribosome-rich granules, specifically enabling replicative fission. Loss of FMRP dysregulates MFF local translation, increases peripheral fission, and disrupts mitochondrial nucleoid distribution.\",\n      \"method\": \"Cryo-electron tomography, real-time translation imaging (SunTag), FMRP conditional KO, live imaging, Rab7 GTPase manipulation\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-ET structural evidence, real-time translation imaging, genetic KO with defined phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"39548330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MFF is SUMOylated at Lys151; AMPK-mediated phosphorylation of MFF enhances its SUMOylation. MFF SUMOylation regulates MiD49/51 binding to MFF within trimeric DRP1-MiD-MFF fission complexes, and non-SUMOylatable MFF K151R impairs CCCP-induced mitochondrial fragmentation in MFF-KO MEFs.\",\n      \"method\": \"SUMO site identification, phosphomimetic/phospho-deficient mutants, K151R non-SUMOylatable mutant rescue, MFF-KO MEFs, CCCP stress assay\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — PTM site defined with mutagenesis and functional rescue, mechanistically linked to complex assembly\",\n      \"pmids\": [\"39365854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Alternative splicing of Mff exon 6 insertion (just after the AMPK phosphorylation site) reduces AMPK-mediated Mff phosphorylation and impairs both mitochondrial fission and MAVS-mediated antiviral response in a phosphorylation-independent manner; tissue-specific splicing patterns regulate Mff function.\",\n      \"method\": \"Mff knockout MEFs rescued with single splice isoforms, AMPK phosphorylation assay, mitochondrial morphology, innate immune reporter assay\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — isoform rescue in KO cells with phosphorylation and functional assays, single lab\",\n      \"pmids\": [\"39293584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TRIM21 mediates ubiquitination and proteasomal degradation of MFF; ciprofloxacin upregulates TRIM21, reducing MFF levels and causing mitochondrial dysfunction and trophoblast cell senescence leading to miscarriage.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, TRIM21 knockdown/overexpression, mouse model, trophoblast cell line\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — ubiquitination mechanism with in vivo validation, single lab, new finding\",\n      \"pmids\": [\"41650744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"MFF traffics between mitochondria and melanosomes and localizes to melanosome fission events; MFF downregulation causes melanosome enlargement, intracellular melanin accumulation, and increased lumenal catabolism independent of Drp1. MFF interacts with regulators of the ARP2/3 complex; actin filaments accumulate at MFF-enriched membrane constriction sites between melanosomes, and silencing ARP2/3 subunits phenocopies MFF loss, revealing an extramitochondrial MFF function in actin-dependent melanosome fission.\",\n      \"method\": \"MFF knockdown, live imaging, co-immunoprecipitation with ARP2/3 regulators, actin staining, ARP2/3 subunit knockdown, melanosome morphology and melanin quantification\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, novel extramitochondrial function, single lab\",\n      \"pmids\": [\"41832149\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MFF is a tail-anchored mitochondrial outer membrane protein that serves as the primary receptor recruiting cytosolic Drp1 oligomers to drive mitochondrial (and peroxisomal) fission; it forms oligomers through its C-terminal coiled coil, and actin filaments enhance Mff-mediated Drp1 GTPase activation. MFF activity is regulated by multiple post-translational modifications—AMPK-mediated phosphorylation (enhanced by kinases including JNK and CK2α, suppressed by phosphatases like DUSP1), SUMOylation at Lys151 (which controls MiD49/51 binding and complex composition), succinylation at Lys302 (protecting it from Parkin-mediated degradation), and Parkin-mediated ubiquitination (for constitutive turnover and mitophagy). MFF selectively binds higher-order Drp1 oligomers (unlike MiD49/51 which recruit dimers), and Drp1 deSUMOylation by SENP3 enhances this interaction. Beyond fission, MFF independently promotes active MAVS cluster formation for antiviral immunity, forms complexes with VDAC1 to regulate mitochondrial outer membrane permeability, and mediates actin-dependent melanosome fission via ARP2/3 complex interactions; additionally, local MFF translation in neurons is controlled by FMRP granules at fission sites to spatially regulate mitochondrial division.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MFF is a tail-anchored outer mitochondrial membrane protein that functions as the primary receptor for recruiting higher-order Drp1 oligomers to drive mitochondrial and peroxisomal fission, with its activity amplified by actin filaments and dependent on its own oligomerization through a C-terminal coiled coil [PMID:18353969, PMID:21149567, PMID:34347505]. MFF activity is regulated by a convergence of post-translational modifications: AMPK, PKD, JNK/CK2α-mediated phosphorylation promotes Drp1 recruitment and fission; SUMOylation at Lys151 controls MiD49/51 binding within trimeric fission complexes; succinylation at Lys302 protects MFF from Parkin-mediated degradation; and ubiquitination by Parkin or TRIM21 directs its constitutive turnover [PMID:39365854, PMID:34010649, PMID:37291333, PMID:31112535, PMID:41650744]. Beyond organelle division, MFF independently promotes active MAVS cluster formation on the mitochondrial surface for innate antiviral signaling, forms complexes with VDAC1 to regulate outer membrane permeability, and mediates ARP2/3-dependent actin-based melanosome fission [PMID:33177519, PMID:31582380, PMID:41832149]. In neurons, local MFF translation at mitochondrial fission sites is spatially controlled by FMRP-containing RNA granules, and Mff-deficient mice develop fatal dilated cardiomyopathy rescued by concomitant loss of the fusion factor Mfn1 [PMID:39548330, PMID:26598616].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"MFF was identified as a novel mitochondrial fission factor, resolving the question of whether mammalian fission required additional receptors beyond Fis1: MFF knockdown phenocopied Drp1 loss, establishing it as a core fission component.\",\n      \"evidence\": \"siRNA knockdown with subcellular fractionation, gel filtration, and fluorescence microscopy in mammalian cells\",\n      \"pmids\": [\"18353969\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction with Drp1 not yet demonstrated\", \"Mechanism of MFF action at the membrane unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The key question of whether MFF directly recruits Drp1 was answered: MFF physically binds Drp1 in vitro and in vivo, and plasma membrane-retargeted MFF redirects Drp1, establishing MFF as a bona fide Drp1 receptor independent of Fis1.\",\n      \"evidence\": \"Reciprocal co-IP, in vitro pulldown, CAAX plasma membrane targeting, gain/loss-of-function\",\n      \"pmids\": [\"21149567\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MFF-Drp1 interaction unresolved\", \"Whether MFF distinguishes Drp1 oligomeric states unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The question of receptor redundancy was addressed: MiD49/51 can independently recruit Drp1 in Mff-null/Fis1-null cells, and MFF also functions in peroxisomal fission by recruiting Drp1 to peroxisomes in cooperation with Pex11pβ.\",\n      \"evidence\": \"Fis1-null, Mff-null, and double-null cell lines; Drp1 puncta quantification; co-IP of MFF-Pex11pβ\",\n      \"pmids\": [\"23283981\", \"24167709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of MFF versus MiD49/51 in different tissues unclear\", \"Pex11pβ-MFF interaction not reconstituted in vitro\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Multiple advances resolved how MFF selectivity, regulation, and physiological importance operate: MFF selectively binds higher-order Drp1 oligomers (unlike MiD49/51 which recruit dimers), Drp1 Ser637 dephosphorylation enhances MFF binding, Parkin ubiquitinates MFF at Lys251 to link it to mitophagy, and Mff-knockout mice develop fatal dilated cardiomyopathy rescued by concomitant Mfn1 deletion.\",\n      \"evidence\": \"Recombinant protein binding with assembly mutants; phosphomimetic/phospho-deficient Drp1 mutants and co-IP; ubiquitination assay with K251R mutant; Mff-null and Mff/Mfn1 double-knockout mice with cardiac phenotyping\",\n      \"pmids\": [\"26446846\", \"26432782\", \"26008206\", \"26598616\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of oligomer selectivity not defined\", \"Identity of kinase/phosphatase for Drp1 Ser637 in this context not fully resolved\", \"Whether additional E3 ligases ubiquitinate MFF unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"MFF was placed within a broader regulatory network: MiD51 suppresses MFF-dependent Drp1 GTPase activation, and MFF/Drp1 negatively regulate MARCH5 E3 ligase activity toward OMM substrates including MiD49 and Mcl1.\",\n      \"evidence\": \"BioID proximity labeling, CRISPR knockouts, Drp1 GTPase assay; multiple KO combinations with ubiquitination and stability assays\",\n      \"pmids\": [\"27076521\", \"27932492\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MFF inhibits MARCH5 mechanistically is unclear\", \"Whether MiD51-MFF interplay is tissue-specific not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Post-translational control of the MFF-Drp1 axis was expanded: SENP3-mediated deSUMOylation of Drp1 selectively promotes Drp1 binding to MFF, and JNK-mediated MFF phosphorylation/upregulation drives pathological fission counteracted by DUSP1.\",\n      \"evidence\": \"SUMO site mutants with co-IP; SENP3 knockdown/overexpression; transgenic mouse cardiac ischemia-reperfusion model with DUSP1\",\n      \"pmids\": [\"28262828\", \"29149759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct phosphorylation sites on MFF by JNK not mapped\", \"Whether SENP3-Drp1-MFF axis operates in all tissues unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"MFF was shown to function beyond simple fission: it forms complexes with VDAC1 to regulate mitochondrial outer membrane permeability, controls neuronal mitochondrial size and presynaptic calcium/neurotransmitter release, and CK2α was identified as an upstream kinase phosphorylating MFF during cardiac ischemia.\",\n      \"evidence\": \"MFF-VDAC1 co-IP with mutagenesis and peptidomimetic disruption; in utero electroporation with shRNA and Ca2+ imaging in neurons; NR4A1 KO mice with CK2α inhibition\",\n      \"pmids\": [\"31582380\", \"30479337\", \"29744594\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural detail of MFF-VDAC1 complex lacking\", \"Whether MFF-VDAC1 interaction is relevant to non-tumor physiology untested\", \"Specific phosphorylation sites for CK2α on MFF not mapped\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"An entirely fission-independent function was established: MFF promotes active MAVS cluster formation on mitochondria for antiviral signaling, and AMPK phosphorylation of MFF under metabolic stress disorganizes MAVS clusters to suppress innate immunity.\",\n      \"evidence\": \"Mff knockout cells, AMPK phosphorylation assay, MAVS oligomerization and innate immune reporter assays\",\n      \"pmids\": [\"33177519\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MFF-MAVS interaction unknown\", \"Whether MFF organizes other signaling platforms not explored\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The biophysical mechanism of MFF was resolved: MFF is an oligomer (likely trimer) whose dynamic self-assembly through its coiled coil is essential for Drp1 activation, and actin filaments enhance this by lowering the effective MFF concentration ~10-fold; separately, PKD was identified as the mitosis-specific MFF kinase required for chromosome segregation.\",\n      \"evidence\": \"In vitro reconstitution with purified proteins, TIRF microscopy, GTPase assay, Mff-KO rescue with oligomerization-defective mutants; in vitro kinase assay with phospho-mutant rescue and chromosome segregation assays\",\n      \"pmids\": [\"34347505\", \"34010649\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of MFF oligomer not determined\", \"How actin filaments are positioned at fission sites relative to MFF in vivo unclear\", \"Whether PKD phosphorylation affects MFF oligomerization untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A novel stabilizing modification was identified: CPT1A-mediated succinylation of MFF at Lys302 protects MFF from Parkin-mediated ubiquitin-proteasomal degradation, linking metabolic rewiring to fission control in cancer.\",\n      \"evidence\": \"Mass spectrometry identification of succinylation site, K302R mutagenesis, ubiquitination assay, in vivo xenograft\",\n      \"pmids\": [\"37291333\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether succinylation-ubiquitination crosstalk on MFF operates in non-cancer contexts unknown\", \"Desuccinylase for Lys302 not identified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two regulatory layers were defined: AMPK-dependent phosphorylation enhances MFF SUMOylation at Lys151, which controls MiD49/51 binding within trimeric DRP1-MiD-MFF complexes; and FMRP granules control local MFF translation at mitochondrial fission sites in neurons to spatially regulate replicative versus peripheral fission.\",\n      \"evidence\": \"SUMO site ID with K151R rescue in MFF-KO MEFs; cryo-ET, real-time SunTag translation imaging, FMRP conditional KO in neurons; isoform rescue with splice variants in KO MEFs\",\n      \"pmids\": [\"39365854\", \"39548330\", \"39293584\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SUMOylation structurally alters MFF-MiD binding not resolved\", \"Whether FMRP-dependent local translation of MFF occurs outside neurons unknown\", \"Functional significance of most MFF splice isoforms untested in vivo\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"An additional E3 ubiquitin ligase, TRIM21, was identified as mediating MFF degradation, linking MFF turnover to trophoblast senescence and miscarriage; separately, MFF was shown to traffic to melanosomes and drive actin/ARP2/3-dependent melanosome fission independent of Drp1.\",\n      \"evidence\": \"TRIM21 co-IP and ubiquitination assay with in vivo mouse model; MFF knockdown with live imaging, ARP2/3 subunit knockdown, and melanosome morphology in melanocytes\",\n      \"pmids\": [\"41650744\", \"41832149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"TRIM21-MFF ubiquitination sites not mapped\", \"Whether MFF-ARP2/3 interaction is direct or mediated by adaptors unclear\", \"Mechanism of MFF trafficking from mitochondria to melanosomes unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the atomic structure of MFF (as monomer and oligomer), the structural basis of its selective recognition of higher-order Drp1 oligomers, how MFF coordinates its dual fission-dependent and fission-independent functions (MAVS signaling, VDAC1 regulation, melanosome fission), and the full landscape of tissue-specific splice isoform functions in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of MFF available\", \"Mechanism of MFF trafficking between organelles unknown\", \"Relative in vivo contributions of multiple MFF kinases and E3 ligases not systematically compared\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 4, 19]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 18, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 5, 16, 19]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [3, 23]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [29]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 1, 5, 19, 20]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [18, 23, 27]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [7, 15]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [7, 17]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [20]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [17, 24, 28]}\n    ],\n    \"complexes\": [\n      \"DRP1-MFF fission complex\",\n      \"DRP1-MiD49/51-MFF trimeric complex\",\n      \"MFF-VDAC1 complex\"\n    ],\n    \"partners\": [\n      \"DNM1L\",\n      \"VDAC1\",\n      \"MAVS\",\n      \"PRKN\",\n      \"MIEF1\",\n      \"MIEF2\",\n      \"PRKAA1\",\n      \"PRKD1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}