{"gene":"MTFR1","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2004,"finding":"CHPPR (later named MTFR1) is a mitochondrial protein that localizes to mitochondrial inner membranes and promotes mitochondrial fission; the domain responsible for network-to-spheroid transition spans amino acid residues 182–309 including the poly-proline region, and this effect is sequence-specific.","method":"Fluorescence/confocal microscopy, immunoelectron microscopy, domain deletion constructs, MitoTracker labeling, functional mitochondrial activity assays","journal":"Journal of cellular physiology","confidence":"High","confidence_rationale":"Tier 1–2 — direct subcellular localization with functional consequence, domain mutagenesis, replicated in multiple cell types","pmids":["15389597"],"is_preprint":false},{"year":2007,"finding":"In Mtfr1-deficient mice (gene-trap knockout), testes show downregulation of reactive oxygen species scavenging enzymes (including glutathione peroxidase 3) and oxidative DNA damage, indicating that Mtfr1 is required for antioxidant defense in the male gonad.","method":"Gene-trap knockout mouse model, real-time PCR, in situ hybridization, oxidative DNA damage assays","journal":"Reproduction (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined molecular phenotype (ROS enzyme downregulation, oxidative DNA damage), multiple orthogonal methods","pmids":["17709566"],"is_preprint":false},{"year":2010,"finding":"Mtfr1 (and its paralog Dufd1) are associated with membrane-enriched mitochondrial fractions; knockdown of Mtfr1 in testicular germ cells severely impairs O2 consumption and ATP synthesis, demonstrating a required role in mitochondrial respiration. Mtfr1-deficient mouse testes also show severely reduced O2 consumption and ATP synthesis.","method":"Subcellular fractionation, siRNA knockdown, O2 consumption assays, ATP synthesis measurement, Mtfr1-knockout mouse testes","journal":"Journal of cellular physiology","confidence":"High","confidence_rationale":"Tier 2 — KO and KD with direct biochemical readouts (O2, ATP), replicated in vitro and in vivo","pmids":["20568109"],"is_preprint":false},{"year":2015,"finding":"Mtfr1 promotes mitochondrial fission and cardiomyocyte apoptosis; it is a direct translational target of miR-324-5p, whose expression is transcriptionally repressed by NFAT4, defining the NFAT4/miR-324-5p/Mtfr1 signaling axis. Knockdown of Mtfr1 suppresses mitochondrial fission and apoptosis in cardiomyocytes.","method":"miRNA mimic/inhibitor transfection, luciferase reporter assay (confirming Mtfr1 as miR-324-5p target), siRNA knockdown of Mtfr1, mitochondrial morphology analysis, NFAT4 knockdown, in vivo myocardial infarction model","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (reporter assay, KD, in vivo model), clearly defined pathway axis","pmids":["26633713"],"is_preprint":false},{"year":2019,"finding":"Mtfr1 is a direct target of miR-324-5p in endothelial progenitor cells; overexpression of miR-324-5p suppresses Mtfr1 protein, reduces mitochondrial fragmentation, maintains membrane potential and ATP levels, and protects against oxidative stress-induced apoptosis.","method":"miRTarBase prediction, western blot (protein-level confirmation of targeting), miR-324-5p mimic transfection, mitochondrial morphology and membrane potential assays","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, western blot confirmation of target plus phenotypic readouts, no independent luciferase reporter in this study","pmids":["31066044"],"is_preprint":false},{"year":2021,"finding":"MTFR1 promotes glycolysis and proliferation/invasion of lung adenocarcinoma cells via the AMPK/mTOR signalling pathway; miR-29c-3p directly targets MTFR1 and negatively regulates its expression.","method":"Dual-luciferase reporter assay, siRNA knockdown, overexpression constructs, in vitro proliferation/invasion assays, rescue experiments, in vivo xenograft","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct target validation by luciferase + western blot, pathway inferred from AMPK/mTOR readouts by western blot, single lab","pmids":["34926459"],"is_preprint":false},{"year":2022,"finding":"MTFR1 is a direct target of miR-194-5p; SNHG1 acts as a competing endogenous RNA that sequesters miR-194-5p, thereby upregulating MTFR1 and promoting TGFβ1-induced EMT, migration and invasion in tongue squamous cell carcinoma cells.","method":"Luciferase reporter assay, RNA pull-down assay, siRNA knockdown, Transwell assays, western blot for EMT markers","journal":"Molecular biotechnology","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct target validation by luciferase and RNA pulldown, functional phenotype via KD, single lab","pmids":["35107755"],"is_preprint":false},{"year":2025,"finding":"Under glucose deprivation, MTFR1 interacts with NEK1 kinase; NEK1 phosphorylates MTFR1 at serine 119, which switches mitochondrial dynamics from fission to fusion, supporting oxidative phosphorylation and colon cancer cell survival under metabolic stress.","method":"Mass spectrometry (interacting proteins and phosphorylation site identification), MitoTracker staining, MitoSOX, JC-1, Seahorse metabolic flux assay, co-immunoprecipitation, site-directed mutagenesis (implied by phosphosite identification)","journal":"Neoplasia (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 — MS-identified interaction and phosphosite, multiple functional mitochondrial readouts, single lab","pmids":["40121946"],"is_preprint":false},{"year":2025,"finding":"MTFR1 is a direct target of miR-142; in miR-142-knockout CD4+ T cells, MTFR1 protein is overexpressed, leading to impaired mitochondrial function, metabolic reprogramming toward glycolysis with restrained oxidative phosphorylation, increased apoptosis, and reduced proliferation.","method":"Luciferase reporter assay, western blot, Seahorse metabolic analysis, flow cytometry, single-cell sequencing, miR-142-/- mouse model, mitochondrial staining and electron microscopy","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — direct target validation, KO mouse model, multiple orthogonal metabolic and mitochondrial readouts, single lab","pmids":["40334625"],"is_preprint":false},{"year":2025,"finding":"MTFR1 knockdown in triple-negative breast cancer cells inhibits proliferation, migration, invasion, and mitochondrial function, and suppresses activation of the NF-κB signalling pathway, as confirmed by transcriptome sequencing and western blot.","method":"siRNA knockdown, CCK-8, wound healing, Transwell assays, nude mouse xenograft, RNA-seq, western blot for NF-κB pathway components","journal":"IUBMB life","confidence":"Medium","confidence_rationale":"Tier 2–3 — KD with defined pathway readout (NF-κB), supported by transcriptomics and in vivo model, single lab","pmids":["41222164"],"is_preprint":false}],"current_model":"MTFR1 (originally identified as CHPPR) is a nuclear-encoded mitochondrial inner-membrane protein that promotes mitochondrial fission through a sequence-specific domain (residues 182–309); it is required for mitochondrial respiration (O2 consumption and ATP synthesis) and antioxidant defense in vivo, and its activity is regulated post-translationally by NEK1-mediated phosphorylation at serine 119 (which can switch its effect toward fusion under metabolic stress) and at the expression level by multiple miRNAs (miR-324-5p, miR-29c-3p, miR-194-5p, miR-142) that target it to modulate mitochondrial dynamics, cell survival, and metabolic reprogramming in contexts ranging from cardiomyocytes to cancer cells."},"narrative":{"teleology":[{"year":2004,"claim":"The first mechanistic question—where MTFR1 localizes and what it does to mitochondrial morphology—was resolved by showing it is an inner-membrane protein whose residues 182–309 are both necessary and sufficient for driving mitochondrial fission.","evidence":"Confocal/immuno-EM localization, domain deletion constructs, and MitoTracker labeling in multiple cell lines","pmids":["15389597"],"confidence":"High","gaps":["No enzymatic activity identified for the 182–309 domain","Mechanism by which the poly-proline region promotes fission is unknown","No binding partners on the mitochondrial membrane identified"]},{"year":2007,"claim":"Using a gene-trap knockout mouse, MTFR1 was established as necessary for antioxidant defense in vivo, linking its loss to downregulation of ROS-scavenging enzymes and oxidative DNA damage in the testis.","evidence":"Mtfr1-knockout mouse, real-time PCR, in situ hybridization, oxidative DNA damage assays in testes","pmids":["17709566"],"confidence":"High","gaps":["Whether the antioxidant phenotype is a direct or indirect consequence of mitochondrial dysfunction is unresolved","Phenotype characterized only in testis"]},{"year":2010,"claim":"The requirement of MTFR1 for mitochondrial respiration was directly demonstrated: knockdown and knockout each severely reduced O₂ consumption and ATP synthesis, establishing MTFR1 as a functional regulator of oxidative phosphorylation, not merely a morphology factor.","evidence":"siRNA knockdown in germ cells plus Mtfr1-knockout mouse testes with direct O₂ consumption and ATP assays","pmids":["20568109"],"confidence":"High","gaps":["Whether MTFR1 acts on a specific respiratory complex or indirectly through membrane remodeling is unknown","Paralog Dufd1 was identified but its functional redundancy was not tested"]},{"year":2015,"claim":"MTFR1 was placed within a defined signaling axis in cardiomyocytes: NFAT4 transcriptionally represses miR-324-5p, which directly targets MTFR1 mRNA, thereby controlling mitochondrial fission and apoptosis during myocardial ischemia.","evidence":"Luciferase reporter assay confirming MTFR1 as miR-324-5p target, siRNA knockdown, NFAT4 knockdown, in vivo myocardial infarction model","pmids":["26633713"],"confidence":"High","gaps":["Whether MTFR1 is the sole effector of miR-324-5p in cardiomyocyte apoptosis is unclear","No structural basis for how fission leads to apoptosis commitment"]},{"year":2019,"claim":"The miR-324-5p/MTFR1 axis was extended to endothelial progenitor cells, where miR-324-5p-mediated suppression of MTFR1 preserves membrane potential and protects against oxidative stress-induced apoptosis, generalizing the regulatory mechanism beyond cardiomyocytes.","evidence":"miR-324-5p mimic transfection, western blot, mitochondrial morphology and membrane potential assays in endothelial progenitor cells","pmids":["31066044"],"confidence":"Medium","gaps":["No independent luciferase reporter validation in this study","Single cell type and single lab"]},{"year":2021,"claim":"MTFR1 was linked to metabolic reprogramming in cancer: it promotes glycolysis and tumor growth through AMPK/mTOR signaling in lung adenocarcinoma, and is directly repressed by miR-29c-3p, revealing an additional miRNA layer of control.","evidence":"Dual-luciferase reporter, siRNA/overexpression, AMPK/mTOR western blots, xenograft model","pmids":["34926459"],"confidence":"Medium","gaps":["Whether MTFR1 directly activates AMPK or alters its activity indirectly through mitochondrial dysfunction is unresolved","Single cancer type"]},{"year":2022,"claim":"A competing endogenous RNA mechanism was established: lncRNA SNHG1 sponges miR-194-5p to de-repress MTFR1, promoting EMT in tongue squamous cell carcinoma and adding a lncRNA regulatory layer.","evidence":"Luciferase reporter, RNA pull-down, siRNA knockdown, Transwell and western blot for EMT markers","pmids":["35107755"],"confidence":"Medium","gaps":["Whether MTFR1 directly drives EMT or acts through mitochondrial fragmentation-dependent ROS is unknown","Single cancer type, single lab"]},{"year":2025,"claim":"Post-translational regulation of MTFR1 was uncovered: NEK1 phosphorylates MTFR1 at Ser119 under glucose deprivation, converting it from a fission promoter to a fusion promoter and thereby sustaining oxidative phosphorylation and cancer cell survival during metabolic stress.","evidence":"Mass spectrometry for interaction and phosphosite, co-immunoprecipitation, MitoTracker/JC-1/Seahorse assays in colon cancer cells","pmids":["40121946"],"confidence":"Medium","gaps":["Structural basis for how a single phosphorylation reverses fission to fusion is unknown","Not independently confirmed outside colon cancer cells","No in vivo validation of the phospho-switch"]},{"year":2025,"claim":"Consolidating the miRNA regulatory theme, miR-142 was shown to restrain MTFR1 in CD4⁺ T cells; loss of miR-142 leads to MTFR1 overexpression, impaired mitochondrial function, metabolic shift toward glycolysis, and reduced T cell fitness, extending MTFR1's role to adaptive immunity.","evidence":"Luciferase reporter, miR-142−/− mouse model, Seahorse, flow cytometry, single-cell sequencing, electron microscopy","pmids":["40334625"],"confidence":"Medium","gaps":["Whether MTFR1 is the dominant miR-142 target responsible for the T cell metabolic phenotype is not excluded","Human T cell relevance not tested"]},{"year":2025,"claim":"MTFR1 was connected to NF-κB signaling in triple-negative breast cancer, where its knockdown suppresses proliferation, migration, invasion, and NF-κB pathway activation, broadening its oncogenic relevance.","evidence":"siRNA knockdown, RNA-seq, western blot for NF-κB, xenograft model","pmids":["41222164"],"confidence":"Medium","gaps":["Whether NF-κB activation is a direct consequence of MTFR1-driven mitochondrial fission or an indirect effect is unclear","Single cancer subtype"]},{"year":null,"claim":"Key unresolved questions include the biochemical activity of MTFR1 (no enzymatic function identified), the structural mechanism by which Ser119 phosphorylation reverses its fission/fusion role, and whether its pro-fission and pro-respiration functions are mechanistically separable.","evidence":"","pmids":[],"confidence":"High","gaps":["No enzymatic or structural characterization of MTFR1","Fission-promoting versus respiration-promoting functions have not been dissected","No reconstituted in vitro system for MTFR1-mediated fission"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,7]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,2]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,3,7]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,5,8]}],"complexes":[],"partners":["NEK1"],"other_free_text":[]},"mechanistic_narrative":"MTFR1 is a nuclear-encoded mitochondrial inner-membrane protein that promotes mitochondrial fission and is essential for mitochondrial respiration and cellular redox homeostasis. Its pro-fission activity maps to a sequence-specific domain spanning residues 182–309; overexpression drives a network-to-spheroid mitochondrial transition, while loss of function severely impairs O₂ consumption, ATP synthesis, and antioxidant defense in vivo [PMID:15389597, PMID:20568109, PMID:17709566]. NEK1-mediated phosphorylation at serine 119 under glucose deprivation switches MTFR1 from a fission-promoting to a fusion-promoting factor, sustaining oxidative phosphorylation during metabolic stress [PMID:40121946]. MTFR1 expression is tightly regulated by multiple miRNAs—including miR-324-5p, miR-29c-3p, miR-194-5p, and miR-142—that modulate its levels to control mitochondrial dynamics, apoptosis, and metabolic reprogramming in cardiomyocytes, immune cells, and cancer cells [PMID:26633713, PMID:34926459, PMID:35107755, PMID:40334625]."},"prefetch_data":{"uniprot":{"accession":"Q15390","full_name":"Mitochondrial fission regulator 1","aliases":["Chondrocyte protein with a poly-proline region"],"length_aa":333,"mass_kda":37.0,"function":"May play a role in mitochondrial aerobic respiration. May also regulate mitochondrial organization and fission (By similarity)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q15390/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MTFR1","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":[{"gene":"ACTB","stoichiometry":0.2},{"gene":"ACTG1","stoichiometry":0.2},{"gene":"CALD1","stoichiometry":0.2},{"gene":"PFN1","stoichiometry":0.2},{"gene":"RANBP1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MTFR1","total_profiled":1310},"omim":[{"mim_id":"620765","title":"MITOCHONDRIAL FISSION REGULATOR 1-LIKE PROTEIN; MTFR1L","url":"https://www.omim.org/entry/620765"},{"mim_id":"619414","title":"MITOCHONDRIAL FISSION REGULATOR 1; MTFR1","url":"https://www.omim.org/entry/619414"},{"mim_id":"617702","title":"CANCER SUSCEPTIBILITY CANDIDATE 21, NONCODING; CASC21","url":"https://www.omim.org/entry/617702"},{"mim_id":"605609","title":"OXIDATION RESISTANCE 1; OXR1","url":"https://www.omim.org/entry/605609"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MTFR1"},"hgnc":{"alias_symbol":["CHPPR","KIAA0009","FAM54A2"],"prev_symbol":[]},"alphafold":{"accession":"Q15390","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15390","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15390-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15390-F1-predicted_aligned_error_v6.png","plddt_mean":65.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MTFR1","jax_strain_url":"https://www.jax.org/strain/search?query=MTFR1"},"sequence":{"accession":"Q15390","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15390.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15390/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15390"}},"corpus_meta":[{"pmid":"26633713","id":"PMC_26633713","title":"NFAT4-dependent miR-324-5p regulates mitochondrial morphology and cardiomyocyte cell death by targeting Mtfr1.","date":"2015","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/26633713","citation_count":52,"is_preprint":false},{"pmid":"31622017","id":"PMC_31622017","title":"Inhibition of the LncRNA Gpr19 attenuates ischemia-reperfusion injury after acute myocardial infarction by inhibiting apoptosis and oxidative stress via the miR-324-5p/Mtfr1 axis.","date":"2019","source":"IUBMB life","url":"https://pubmed.ncbi.nlm.nih.gov/31622017","citation_count":48,"is_preprint":false},{"pmid":"20568109","id":"PMC_20568109","title":"The nuclear genes Mtfr1 and Dufd1 regulate mitochondrial dynamic and cellular respiration.","date":"2010","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/20568109","citation_count":44,"is_preprint":false},{"pmid":"15389597","id":"PMC_15389597","title":"Chondrocyte protein with a poly-proline region (CHPPR) is a novel mitochondrial protein and promotes mitochondrial fission.","date":"2004","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/15389597","citation_count":28,"is_preprint":false},{"pmid":"31066044","id":"PMC_31066044","title":"miR-324-5p protects against oxidative stress-induced endothelial progenitor cell injury by targeting Mtfr1.","date":"2019","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/31066044","citation_count":22,"is_preprint":false},{"pmid":"34926459","id":"PMC_34926459","title":"Negatively Regulated by miR-29c-3p, MTFR1 Promotes the Progression and Glycolysis in Lung Adenocarcinoma via the AMPK/mTOR Signalling Pathway.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34926459","citation_count":18,"is_preprint":false},{"pmid":"17709566","id":"PMC_17709566","title":"Impaired expression of genes coding for reactive oxygen species scavenging enzymes in testes of Mtfr1/Chppr-deficient mice.","date":"2007","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/17709566","citation_count":15,"is_preprint":false},{"pmid":"35107755","id":"PMC_35107755","title":"SNHG1/miR-194-5p/MTFR1 Axis Promotes TGFβ1-Induced EMT, Migration and Invasion of Tongue Squamous Cell Carcinoma Cells.","date":"2022","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/35107755","citation_count":12,"is_preprint":false},{"pmid":"38170222","id":"PMC_38170222","title":"Overexpression of MTFR1 promotes cancer progression and drug-resistance on cisplatin and is related to the immune microenvironment in lung adenocarcinoma.","date":"2024","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/38170222","citation_count":3,"is_preprint":false},{"pmid":"40121946","id":"PMC_40121946","title":"MTFR1 phosphorylation-activated adaptive mitochondrial fusion is essential for colon cancer cell survival during glucose deprivation.","date":"2025","source":"Neoplasia (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/40121946","citation_count":3,"is_preprint":false},{"pmid":"40334625","id":"PMC_40334625","title":"miR142 silencing alleviates retinal inflammation by impairing mitochondrial function and reprogramming metabolism of CD4+ T cells via targeting MTFR1.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40334625","citation_count":0,"is_preprint":false},{"pmid":"41222164","id":"PMC_41222164","title":"MTFR1 Promotes Proliferation and Metastasis of Triple-Negative Breast Cancer by Regulating Mitochondrial Metabolism.","date":"2025","source":"IUBMB life","url":"https://pubmed.ncbi.nlm.nih.gov/41222164","citation_count":0,"is_preprint":false},{"pmid":"36120573","id":"PMC_36120573","title":"Corrigendum: Negatively regulated by miR-29c-3p, MTFR1 promotes the progression and glycolysis in lung adenocarcinoma via the AMPK/mTOR signalling pathway.","date":"2022","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/36120573","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8021,"output_tokens":2542,"usd":0.031096},"stage2":{"model":"claude-opus-4-6","input_tokens":5875,"output_tokens":2732,"usd":0.146512},"total_usd":0.177608,"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\": 2004,\n      \"finding\": \"CHPPR (later named MTFR1) is a mitochondrial protein that localizes to mitochondrial inner membranes and promotes mitochondrial fission; the domain responsible for network-to-spheroid transition spans amino acid residues 182–309 including the poly-proline region, and this effect is sequence-specific.\",\n      \"method\": \"Fluorescence/confocal microscopy, immunoelectron microscopy, domain deletion constructs, MitoTracker labeling, functional mitochondrial activity assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct subcellular localization with functional consequence, domain mutagenesis, replicated in multiple cell types\",\n      \"pmids\": [\"15389597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In Mtfr1-deficient mice (gene-trap knockout), testes show downregulation of reactive oxygen species scavenging enzymes (including glutathione peroxidase 3) and oxidative DNA damage, indicating that Mtfr1 is required for antioxidant defense in the male gonad.\",\n      \"method\": \"Gene-trap knockout mouse model, real-time PCR, in situ hybridization, oxidative DNA damage assays\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined molecular phenotype (ROS enzyme downregulation, oxidative DNA damage), multiple orthogonal methods\",\n      \"pmids\": [\"17709566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Mtfr1 (and its paralog Dufd1) are associated with membrane-enriched mitochondrial fractions; knockdown of Mtfr1 in testicular germ cells severely impairs O2 consumption and ATP synthesis, demonstrating a required role in mitochondrial respiration. Mtfr1-deficient mouse testes also show severely reduced O2 consumption and ATP synthesis.\",\n      \"method\": \"Subcellular fractionation, siRNA knockdown, O2 consumption assays, ATP synthesis measurement, Mtfr1-knockout mouse testes\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO and KD with direct biochemical readouts (O2, ATP), replicated in vitro and in vivo\",\n      \"pmids\": [\"20568109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mtfr1 promotes mitochondrial fission and cardiomyocyte apoptosis; it is a direct translational target of miR-324-5p, whose expression is transcriptionally repressed by NFAT4, defining the NFAT4/miR-324-5p/Mtfr1 signaling axis. Knockdown of Mtfr1 suppresses mitochondrial fission and apoptosis in cardiomyocytes.\",\n      \"method\": \"miRNA mimic/inhibitor transfection, luciferase reporter assay (confirming Mtfr1 as miR-324-5p target), siRNA knockdown of Mtfr1, mitochondrial morphology analysis, NFAT4 knockdown, in vivo myocardial infarction model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (reporter assay, KD, in vivo model), clearly defined pathway axis\",\n      \"pmids\": [\"26633713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mtfr1 is a direct target of miR-324-5p in endothelial progenitor cells; overexpression of miR-324-5p suppresses Mtfr1 protein, reduces mitochondrial fragmentation, maintains membrane potential and ATP levels, and protects against oxidative stress-induced apoptosis.\",\n      \"method\": \"miRTarBase prediction, western blot (protein-level confirmation of targeting), miR-324-5p mimic transfection, mitochondrial morphology and membrane potential assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, western blot confirmation of target plus phenotypic readouts, no independent luciferase reporter in this study\",\n      \"pmids\": [\"31066044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MTFR1 promotes glycolysis and proliferation/invasion of lung adenocarcinoma cells via the AMPK/mTOR signalling pathway; miR-29c-3p directly targets MTFR1 and negatively regulates its expression.\",\n      \"method\": \"Dual-luciferase reporter assay, siRNA knockdown, overexpression constructs, in vitro proliferation/invasion assays, rescue experiments, in vivo xenograft\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct target validation by luciferase + western blot, pathway inferred from AMPK/mTOR readouts by western blot, single lab\",\n      \"pmids\": [\"34926459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MTFR1 is a direct target of miR-194-5p; SNHG1 acts as a competing endogenous RNA that sequesters miR-194-5p, thereby upregulating MTFR1 and promoting TGFβ1-induced EMT, migration and invasion in tongue squamous cell carcinoma cells.\",\n      \"method\": \"Luciferase reporter assay, RNA pull-down assay, siRNA knockdown, Transwell assays, western blot for EMT markers\",\n      \"journal\": \"Molecular biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct target validation by luciferase and RNA pulldown, functional phenotype via KD, single lab\",\n      \"pmids\": [\"35107755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Under glucose deprivation, MTFR1 interacts with NEK1 kinase; NEK1 phosphorylates MTFR1 at serine 119, which switches mitochondrial dynamics from fission to fusion, supporting oxidative phosphorylation and colon cancer cell survival under metabolic stress.\",\n      \"method\": \"Mass spectrometry (interacting proteins and phosphorylation site identification), MitoTracker staining, MitoSOX, JC-1, Seahorse metabolic flux assay, co-immunoprecipitation, site-directed mutagenesis (implied by phosphosite identification)\",\n      \"journal\": \"Neoplasia (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS-identified interaction and phosphosite, multiple functional mitochondrial readouts, single lab\",\n      \"pmids\": [\"40121946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MTFR1 is a direct target of miR-142; in miR-142-knockout CD4+ T cells, MTFR1 protein is overexpressed, leading to impaired mitochondrial function, metabolic reprogramming toward glycolysis with restrained oxidative phosphorylation, increased apoptosis, and reduced proliferation.\",\n      \"method\": \"Luciferase reporter assay, western blot, Seahorse metabolic analysis, flow cytometry, single-cell sequencing, miR-142-/- mouse model, mitochondrial staining and electron microscopy\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct target validation, KO mouse model, multiple orthogonal metabolic and mitochondrial readouts, single lab\",\n      \"pmids\": [\"40334625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MTFR1 knockdown in triple-negative breast cancer cells inhibits proliferation, migration, invasion, and mitochondrial function, and suppresses activation of the NF-κB signalling pathway, as confirmed by transcriptome sequencing and western blot.\",\n      \"method\": \"siRNA knockdown, CCK-8, wound healing, Transwell assays, nude mouse xenograft, RNA-seq, western blot for NF-κB pathway components\",\n      \"journal\": \"IUBMB life\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — KD with defined pathway readout (NF-κB), supported by transcriptomics and in vivo model, single lab\",\n      \"pmids\": [\"41222164\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MTFR1 (originally identified as CHPPR) is a nuclear-encoded mitochondrial inner-membrane protein that promotes mitochondrial fission through a sequence-specific domain (residues 182–309); it is required for mitochondrial respiration (O2 consumption and ATP synthesis) and antioxidant defense in vivo, and its activity is regulated post-translationally by NEK1-mediated phosphorylation at serine 119 (which can switch its effect toward fusion under metabolic stress) and at the expression level by multiple miRNAs (miR-324-5p, miR-29c-3p, miR-194-5p, miR-142) that target it to modulate mitochondrial dynamics, cell survival, and metabolic reprogramming in contexts ranging from cardiomyocytes to cancer cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MTFR1 is a nuclear-encoded mitochondrial inner-membrane protein that promotes mitochondrial fission and is essential for mitochondrial respiration and cellular redox homeostasis. Its pro-fission activity maps to a sequence-specific domain spanning residues 182–309; overexpression drives a network-to-spheroid mitochondrial transition, while loss of function severely impairs O₂ consumption, ATP synthesis, and antioxidant defense in vivo [PMID:15389597, PMID:20568109, PMID:17709566]. NEK1-mediated phosphorylation at serine 119 under glucose deprivation switches MTFR1 from a fission-promoting to a fusion-promoting factor, sustaining oxidative phosphorylation during metabolic stress [PMID:40121946]. MTFR1 expression is tightly regulated by multiple miRNAs—including miR-324-5p, miR-29c-3p, miR-194-5p, and miR-142—that modulate its levels to control mitochondrial dynamics, apoptosis, and metabolic reprogramming in cardiomyocytes, immune cells, and cancer cells [PMID:26633713, PMID:34926459, PMID:35107755, PMID:40334625].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"The first mechanistic question—where MTFR1 localizes and what it does to mitochondrial morphology—was resolved by showing it is an inner-membrane protein whose residues 182–309 are both necessary and sufficient for driving mitochondrial fission.\",\n      \"evidence\": \"Confocal/immuno-EM localization, domain deletion constructs, and MitoTracker labeling in multiple cell lines\",\n      \"pmids\": [\"15389597\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No enzymatic activity identified for the 182–309 domain\",\n        \"Mechanism by which the poly-proline region promotes fission is unknown\",\n        \"No binding partners on the mitochondrial membrane identified\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Using a gene-trap knockout mouse, MTFR1 was established as necessary for antioxidant defense in vivo, linking its loss to downregulation of ROS-scavenging enzymes and oxidative DNA damage in the testis.\",\n      \"evidence\": \"Mtfr1-knockout mouse, real-time PCR, in situ hybridization, oxidative DNA damage assays in testes\",\n      \"pmids\": [\"17709566\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the antioxidant phenotype is a direct or indirect consequence of mitochondrial dysfunction is unresolved\",\n        \"Phenotype characterized only in testis\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The requirement of MTFR1 for mitochondrial respiration was directly demonstrated: knockdown and knockout each severely reduced O₂ consumption and ATP synthesis, establishing MTFR1 as a functional regulator of oxidative phosphorylation, not merely a morphology factor.\",\n      \"evidence\": \"siRNA knockdown in germ cells plus Mtfr1-knockout mouse testes with direct O₂ consumption and ATP assays\",\n      \"pmids\": [\"20568109\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether MTFR1 acts on a specific respiratory complex or indirectly through membrane remodeling is unknown\",\n        \"Paralog Dufd1 was identified but its functional redundancy was not tested\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"MTFR1 was placed within a defined signaling axis in cardiomyocytes: NFAT4 transcriptionally represses miR-324-5p, which directly targets MTFR1 mRNA, thereby controlling mitochondrial fission and apoptosis during myocardial ischemia.\",\n      \"evidence\": \"Luciferase reporter assay confirming MTFR1 as miR-324-5p target, siRNA knockdown, NFAT4 knockdown, in vivo myocardial infarction model\",\n      \"pmids\": [\"26633713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether MTFR1 is the sole effector of miR-324-5p in cardiomyocyte apoptosis is unclear\",\n        \"No structural basis for how fission leads to apoptosis commitment\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The miR-324-5p/MTFR1 axis was extended to endothelial progenitor cells, where miR-324-5p-mediated suppression of MTFR1 preserves membrane potential and protects against oxidative stress-induced apoptosis, generalizing the regulatory mechanism beyond cardiomyocytes.\",\n      \"evidence\": \"miR-324-5p mimic transfection, western blot, mitochondrial morphology and membrane potential assays in endothelial progenitor cells\",\n      \"pmids\": [\"31066044\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No independent luciferase reporter validation in this study\",\n        \"Single cell type and single lab\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"MTFR1 was linked to metabolic reprogramming in cancer: it promotes glycolysis and tumor growth through AMPK/mTOR signaling in lung adenocarcinoma, and is directly repressed by miR-29c-3p, revealing an additional miRNA layer of control.\",\n      \"evidence\": \"Dual-luciferase reporter, siRNA/overexpression, AMPK/mTOR western blots, xenograft model\",\n      \"pmids\": [\"34926459\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MTFR1 directly activates AMPK or alters its activity indirectly through mitochondrial dysfunction is unresolved\",\n        \"Single cancer type\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A competing endogenous RNA mechanism was established: lncRNA SNHG1 sponges miR-194-5p to de-repress MTFR1, promoting EMT in tongue squamous cell carcinoma and adding a lncRNA regulatory layer.\",\n      \"evidence\": \"Luciferase reporter, RNA pull-down, siRNA knockdown, Transwell and western blot for EMT markers\",\n      \"pmids\": [\"35107755\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MTFR1 directly drives EMT or acts through mitochondrial fragmentation-dependent ROS is unknown\",\n        \"Single cancer type, single lab\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Post-translational regulation of MTFR1 was uncovered: NEK1 phosphorylates MTFR1 at Ser119 under glucose deprivation, converting it from a fission promoter to a fusion promoter and thereby sustaining oxidative phosphorylation and cancer cell survival during metabolic stress.\",\n      \"evidence\": \"Mass spectrometry for interaction and phosphosite, co-immunoprecipitation, MitoTracker/JC-1/Seahorse assays in colon cancer cells\",\n      \"pmids\": [\"40121946\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Structural basis for how a single phosphorylation reverses fission to fusion is unknown\",\n        \"Not independently confirmed outside colon cancer cells\",\n        \"No in vivo validation of the phospho-switch\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Consolidating the miRNA regulatory theme, miR-142 was shown to restrain MTFR1 in CD4⁺ T cells; loss of miR-142 leads to MTFR1 overexpression, impaired mitochondrial function, metabolic shift toward glycolysis, and reduced T cell fitness, extending MTFR1's role to adaptive immunity.\",\n      \"evidence\": \"Luciferase reporter, miR-142−/− mouse model, Seahorse, flow cytometry, single-cell sequencing, electron microscopy\",\n      \"pmids\": [\"40334625\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MTFR1 is the dominant miR-142 target responsible for the T cell metabolic phenotype is not excluded\",\n        \"Human T cell relevance not tested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"MTFR1 was connected to NF-κB signaling in triple-negative breast cancer, where its knockdown suppresses proliferation, migration, invasion, and NF-κB pathway activation, broadening its oncogenic relevance.\",\n      \"evidence\": \"siRNA knockdown, RNA-seq, western blot for NF-κB, xenograft model\",\n      \"pmids\": [\"41222164\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether NF-κB activation is a direct consequence of MTFR1-driven mitochondrial fission or an indirect effect is unclear\",\n        \"Single cancer subtype\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the biochemical activity of MTFR1 (no enzymatic function identified), the structural mechanism by which Ser119 phosphorylation reverses its fission/fusion role, and whether its pro-fission and pro-respiration functions are mechanistically separable.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No enzymatic or structural characterization of MTFR1\",\n        \"Fission-promoting versus respiration-promoting functions have not been dissected\",\n        \"No reconstituted in vitro system for MTFR1-mediated fission\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 3, 7]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 5, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"NEK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}