{"gene":"MCCC1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2001,"finding":"MCCC1 (MCCA) encodes the 725 amino acid biotin-containing alpha-subunit of 3-methylcrotonyl-CoA carboxylase (MCC), a mitochondrial biotin-dependent enzyme involved in leucine catabolism. The gene is located on chromosome 3q26-q28, consists of 19 exons, and the protein contains mitochondrial signal peptide, biotin carboxylase, and biotin-carrier domains. Mutations in MCCA (S535F, V694X) were identified in patients with MCC deficiency and correlated with near-total loss of enzyme activity in fibroblasts.","method":"cDNA cloning, genomic sequencing, chromosomal mapping, patient mutation identification, enzyme activity assay in fibroblasts","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — two independent groups (PMID 11406611, PMID 11401427) cloned and characterized the gene with consistent findings; enzyme activity directly measured in patient fibroblasts","pmids":["11406611","11401427"],"is_preprint":false},{"year":2001,"finding":"MCCC1 (MCCA) is abundantly expressed in mitochondria-rich organs (heart, skeletal muscle, kidney, liver), consistent with its role as a mitochondrial enzyme.","method":"Expression analysis across human tissues","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — expression pattern replicated across two independent cloning papers, consistent with mitochondrial localization but no direct functional manipulation","pmids":["11401427"],"is_preprint":false},{"year":2003,"finding":"Four missense mutations in MCCA (two) and MCCB (two) mapping to evolutionarily conserved residues all resulted in null or severely diminished MCC carboxylase activity when expressed by transient transfection in SV40-transformed deficient fibroblasts. Structural modelling of MCCA mutations was performed in the context of the crystallized biotin carboxylase subunit of E. coli acetyl-CoA carboxylase.","method":"Transient transfection of patient-derived deficient fibroblasts, enzyme activity assay, structural homology modelling","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation assay in patient cells with direct enzyme activity readout; structural modelling is computational but supports the enzymatic data","pmids":["14680978"],"is_preprint":false},{"year":2023,"finding":"MCCA (MCCC1) interacts directly with the pro-apoptotic protein Bad via protein-protein interaction. MCCA knockdown in multiple myeloma cells reduced Bad protein levels (shortened Bad half-life from 7.34 h to 2.42 h), decreased Bax levels, increased anti-apoptotic Bcl-xl and Mcl-1 levels, and caused mitochondrial dysfunction, resulting in multidrug resistance.","method":"Immunoprecipitation, immunofluorescence staining, protein structural simulation, protein stability (half-life) assay, CCK-8 viability assay, apoptosis assay, xenograft mouse model with bioluminescence imaging","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional KD with multiple cellular and in vivo readouts from a single lab","pmids":["37805164"],"is_preprint":false},{"year":2021,"finding":"lncRNA AABR07005593.1 binds directly to MCCC1 protein and, through this interaction, promotes activation of the NF-κB pathway and upregulation of IL-6 in PM2.5-stimulated alveolar macrophages.","method":"ChIRP-MS (comprehensive identification of RNA-binding proteins by mass spectrometry), western blot, RNA interference","journal":"Ecotoxicology and environmental safety","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIRP-MS identified the interaction with orthogonal western blot validation; single lab, mechanistic pathway placement via RNAi","pmids":["34619471"],"is_preprint":false},{"year":2025,"finding":"lncBADR binds directly to Mccc1 (and Pcca) in T cells, inhibiting branched-chain amino acid (BCAA) degradation and causing intracellular BCAA accumulation, which activates the mTOR-Stat1 signaling pathway and promotes IFN-γ secretion. T cell-specific lncBADR knockout restored BCAA degradation and reduced pathogenic T cell function in experimental autoimmune encephalomyelitis.","method":"T cell-specific lncBADR knockout mice, EAE model, RNA-protein binding assay, metabolic assay, mTOR-Stat1 pathway analysis, IFN-γ measurement, high-BCAA feeding rescue experiment","journal":"Journal of neuroinflammation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with in vivo disease model and rescue experiment; binding to Mccc1 established biochemically; single lab","pmids":["41013574"],"is_preprint":false},{"year":2024,"finding":"The biotin-containing enzyme MCCC1 directly binds corosolic acid (CA) and its derivatives. Using a CA-biotin chemical probe and avidin-biotin affinity pull-down followed by quantitative proteomics, MCCC1 was identified as a direct binding target of CA. The interaction was validated in vitro, and CA/derivative H26 modulate insulin resistance signaling through MCCC1.","method":"Chemical probe (CA-biotin), avidin-biotin affinity pull-down, quantitative proteomics, in vitro binding validation, insulin resistance signaling assay, diabetic mouse model","journal":"European journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — chemical probe affinity pull-down with MS identification and in vitro validation; single lab","pmids":["39731787"],"is_preprint":false},{"year":2025,"finding":"The intronic PD-risk variant rs12637471 in MCCC1 regulates MCCC1 mRNA expression: G-allele carriers show significantly elevated MCCC1 mRNA in postmortem brain tissue. CRISPR/Cas9-edited isogenic iPSC-derived dopaminergic neurons differing only at rs12637471 showed increased MCCC1 expression in G-allele lines, establishing a causal regulatory relationship.","method":"Postmortem brain mRNA quantification, CRISPR/Cas9 isogenic iPSC lines, dopaminergic neuron differentiation, qPCR/expression analysis, eQTL validation with GTEx","journal":"Journal of human genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — isogenic CRISPR editing provides direct causal evidence; replicated with postmortem brain data and orthogonal GTEx eQTL data","pmids":["40216992"],"is_preprint":false}],"current_model":"MCCC1 (MCCA) encodes the biotin-containing alpha-subunit of the mitochondrial 3-methylcrotonyl-CoA carboxylase heterodimer, where it catalyzes a key step in leucine catabolism; beyond its enzymatic role, MCCC1 interacts with the pro-apoptotic protein Bad to regulate apoptotic signaling and mitochondrial integrity, is bound by regulatory lncRNAs (AABR07005593.1 and lncBADR) that co-opt its function to modulate NF-κB/IL-6 and mTOR-Stat1/IFN-γ pathways respectively, directly binds small-molecule ligands such as corosolic acid with implications for insulin resistance, and its expression in dopaminergic neurons is causally regulated by the Parkinson's disease-associated intronic variant rs12637471 via a CRISPR-validated mechanism."},"narrative":{"mechanistic_narrative":"MCCC1 encodes the biotin-containing alpha-subunit of mitochondrial 3-methylcrotonyl-CoA carboxylase (MCC), a biotin-dependent enzyme that catalyzes a key step in leucine catabolism; the protein carries a mitochondrial signal peptide together with biotin carboxylase and biotin-carrier domains, and is most abundant in mitochondria-rich organs [PMID:11406611, PMID:11401427]. Loss-of-function missense and truncating mutations in conserved residues abolish carboxylase activity in patient fibroblasts, causing 3-methylcrotonyl-CoA carboxylase deficiency [PMID:11406611, PMID:11401427, PMID:14680978]. Beyond catalysis, MCCC1 has emerging roles in cellular signaling: it binds the pro-apoptotic protein Bad and stabilizes it, such that MCCC1 depletion shortens Bad half-life, lowers Bax, raises anti-apoptotic Bcl-xL and Mcl-1, and induces mitochondrial dysfunction and multidrug resistance [PMID:37805164]. Its catabolic activity is also a target of regulatory lncRNAs: lncBADR binds MCCC1 to inhibit branched-chain amino acid degradation, driving BCAA accumulation that activates mTOR-Stat1 signaling and IFN-γ secretion in pathogenic T cells, while AABR07005593.1 binds MCCC1 to promote NF-κB activation and IL-6 induction [PMID:34619471, PMID:41013574]. A Parkinson's disease-associated intronic variant, rs12637471, causally elevates MCCC1 expression in dopaminergic neurons, as shown in isogenic CRISPR-edited iPSC lines [PMID:40216992].","teleology":[{"year":2001,"claim":"Establishing the molecular identity of MCCC1 answered what gene product underlies one branch of leucine catabolism and what its disease relevance is, defining it as the biotin-dependent alpha-subunit of MCC whose mutation abolishes enzyme activity.","evidence":"cDNA cloning, genomic sequencing, chromosomal mapping, and patient mutation identification with fibroblast enzyme assays; replicated tissue expression analysis","pmids":["11406611","11401427"],"confidence":"High","gaps":["No structural data on the human holoenzyme","Stoichiometry and assembly with the beta-subunit not resolved in these studies"]},{"year":2003,"claim":"Functional complementation showed that conserved-residue missense mutations are directly causal for loss of carboxylase activity, linking specific structural positions to catalytic competence.","evidence":"Transient transfection of patient-derived deficient fibroblasts with enzyme activity readout plus homology modelling onto E. coli acetyl-CoA carboxylase","pmids":["14680978"],"confidence":"Medium","gaps":["Structural inference is computational, not a human crystal structure","Does not address regulation of the enzyme in vivo"]},{"year":2021,"claim":"Identifying MCCC1 as a direct binding partner of lncRNA AABR07005593.1 extended its role beyond metabolism into inflammatory signaling.","evidence":"ChIRP-MS with western blot validation and RNAi pathway placement in PM2.5-stimulated alveolar macrophages","pmids":["34619471"],"confidence":"Medium","gaps":["Single lab without reciprocal validation","Mechanism by which MCCC1 binding drives NF-κB activation is undefined"]},{"year":2023,"claim":"The MCCC1-Bad interaction connected the enzyme to apoptotic regulation, showing it stabilizes a pro-apoptotic protein and that its loss reprograms the Bcl-2 family balance toward survival and drug resistance.","evidence":"Reciprocal Co-IP, structural simulation, Bad half-life assay, apoptosis assays, and xenograft model in multiple myeloma cells","pmids":["37805164"],"confidence":"Medium","gaps":["Single lab","Molecular basis of MCCC1-mediated Bad stabilization not defined","Whether catalytic activity is required for the apoptotic role is untested"]},{"year":2024,"claim":"Chemical-probe target identification revealed MCCC1 as a direct small-molecule binding target of corosolic acid, linking the enzyme to insulin resistance signaling.","evidence":"CA-biotin affinity pull-down with quantitative proteomics, in vitro binding validation, and diabetic mouse model","pmids":["39731787"],"confidence":"Medium","gaps":["Single lab","Binding site and effect on enzymatic activity unresolved","Causal contribution of MCCC1 to the insulin phenotype not isolated genetically"]},{"year":2025,"claim":"Two studies established MCCC1 as a regulated node: lncBADR binding inhibits BCAA degradation to drive mTOR-Stat1/IFN-γ in pathogenic T cells, and a PD-risk variant causally elevates MCCC1 expression in dopaminergic neurons.","evidence":"T cell-specific lncBADR knockout EAE model with metabolic rescue; CRISPR/Cas9 isogenic iPSC-derived dopaminergic neurons with postmortem brain and GTEx eQTL corroboration","pmids":["41013574","40216992"],"confidence":"Medium","gaps":["Functional consequence of elevated MCCC1 in dopaminergic neurons for PD pathology unknown","lncBADR mechanism of inhibiting MCCC1 catalysis not defined"]},{"year":null,"claim":"How MCCC1's canonical carboxylase activity is mechanistically coupled to its non-metabolic roles in apoptosis, inflammation, and neuronal disease risk remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human holoenzyme structure","Unclear whether enzymatic and signaling functions are separable","Causal link between MCCC1 dosage and Parkinson's disease neurodegeneration not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,2,5]}],"complexes":["3-methylcrotonyl-CoA carboxylase (MCC)"],"partners":["BAD","AABR07005593.1","LNCBADR","PCCA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96RQ3","full_name":"Methylcrotonoyl-CoA carboxylase subunit alpha, mitochondrial","aliases":["3-methylcrotonyl-CoA carboxylase 1","3-methylcrotonyl-CoA carboxylase biotin-containing subunit","3-methylcrotonyl-CoA:carbon dioxide ligase subunit alpha"],"length_aa":725,"mass_kda":80.5,"function":"Biotin-attachment subunit of the 3-methylcrotonyl-CoA carboxylase, an enzyme that catalyzes the conversion of 3-methylcrotonyl-CoA to 3-methylglutaconyl-CoA, a critical step for leucine and isovaleric acid catabolism","subcellular_location":"Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/Q96RQ3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MCCC1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MCCC1","total_profiled":1310},"omim":[{"mim_id":"615751","title":"CARBONIC ANHYDRASE VA DEFICIENCY, HYPERAMMONEMIA DUE TO; CA5AD","url":"https://www.omim.org/entry/615751"},{"mim_id":"609019","title":"BIOTINIDASE; BTD","url":"https://www.omim.org/entry/609019"},{"mim_id":"609018","title":"HOLOCARBOXYLASE SYNTHETASE; HLCS","url":"https://www.omim.org/entry/609018"},{"mim_id":"609014","title":"3-@METHYLCROTONYL-CoA CARBOXYLASE 2; MCCC2","url":"https://www.omim.org/entry/609014"},{"mim_id":"609010","title":"3-@METHYLCROTONYL-CoA CARBOXYLASE 1; MCCC1","url":"https://www.omim.org/entry/609010"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Mitochondria","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MCCC1"},"hgnc":{"alias_symbol":["MCCA","MCCCα"],"prev_symbol":[]},"alphafold":{"accession":"Q96RQ3","domains":[{"cath_id":"3.40.50.20","chopping":"50-150","consensus_level":"high","plddt":97.0419,"start":50,"end":150},{"cath_id":"3.30.1490.20","chopping":"179-247","consensus_level":"high","plddt":88.2678,"start":179,"end":247},{"cath_id":"3.30.470.20","chopping":"259-495","consensus_level":"medium","plddt":95.6658,"start":259,"end":495},{"cath_id":"3.30.700.40","chopping":"504-635","consensus_level":"high","plddt":91.4678,"start":504,"end":635},{"cath_id":"2.40.50.100","chopping":"649-713","consensus_level":"high","plddt":86.9742,"start":649,"end":713}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96RQ3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96RQ3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96RQ3-F1-predicted_aligned_error_v6.png","plddt_mean":87.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MCCC1","jax_strain_url":"https://www.jax.org/strain/search?query=MCCC1"},"sequence":{"accession":"Q96RQ3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96RQ3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96RQ3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96RQ3"}},"corpus_meta":[{"pmid":"23108278","id":"PMC_23108278","title":"Three-way (N-way) fusion of brain imaging data based on mCCA+jICA and its application to discriminating schizophrenia.","date":"2012","source":"NeuroImage","url":"https://pubmed.ncbi.nlm.nih.gov/23108278","citation_count":110,"is_preprint":false},{"pmid":"23755002","id":"PMC_23755002","title":"Combination of Resting State fMRI, DTI, and sMRI Data to Discriminate Schizophrenia by N-way MCCA + jICA.","date":"2013","source":"Frontiers in human neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/23755002","citation_count":85,"is_preprint":false},{"pmid":"16835865","id":"PMC_16835865","title":"Newborn screening for 3-methylcrotonyl-CoA carboxylase deficiency: population heterogeneity of MCCA and MCCB mutations and impact on risk assessment.","date":"2006","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/16835865","citation_count":67,"is_preprint":false},{"pmid":"25642962","id":"PMC_25642962","title":"The octahaem MccA is a haem c-copper sulfite 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\"MCCC1 (MCCA) encodes the 725 amino acid biotin-containing alpha-subunit of 3-methylcrotonyl-CoA carboxylase (MCC), a mitochondrial biotin-dependent enzyme involved in leucine catabolism. The gene is located on chromosome 3q26-q28, consists of 19 exons, and the protein contains mitochondrial signal peptide, biotin carboxylase, and biotin-carrier domains. Mutations in MCCA (S535F, V694X) were identified in patients with MCC deficiency and correlated with near-total loss of enzyme activity in fibroblasts.\",\n      \"method\": \"cDNA cloning, genomic sequencing, chromosomal mapping, patient mutation identification, enzyme activity assay in fibroblasts\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — two independent groups (PMID 11406611, PMID 11401427) cloned and characterized the gene with consistent findings; enzyme activity directly measured in patient fibroblasts\",\n      \"pmids\": [\"11406611\", \"11401427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MCCC1 (MCCA) is abundantly expressed in mitochondria-rich organs (heart, skeletal muscle, kidney, liver), consistent with its role as a mitochondrial enzyme.\",\n      \"method\": \"Expression analysis across human tissues\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — expression pattern replicated across two independent cloning papers, consistent with mitochondrial localization but no direct functional manipulation\",\n      \"pmids\": [\"11401427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Four missense mutations in MCCA (two) and MCCB (two) mapping to evolutionarily conserved residues all resulted in null or severely diminished MCC carboxylase activity when expressed by transient transfection in SV40-transformed deficient fibroblasts. Structural modelling of MCCA mutations was performed in the context of the crystallized biotin carboxylase subunit of E. coli acetyl-CoA carboxylase.\",\n      \"method\": \"Transient transfection of patient-derived deficient fibroblasts, enzyme activity assay, structural homology modelling\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation assay in patient cells with direct enzyme activity readout; structural modelling is computational but supports the enzymatic data\",\n      \"pmids\": [\"14680978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MCCA (MCCC1) interacts directly with the pro-apoptotic protein Bad via protein-protein interaction. MCCA knockdown in multiple myeloma cells reduced Bad protein levels (shortened Bad half-life from 7.34 h to 2.42 h), decreased Bax levels, increased anti-apoptotic Bcl-xl and Mcl-1 levels, and caused mitochondrial dysfunction, resulting in multidrug resistance.\",\n      \"method\": \"Immunoprecipitation, immunofluorescence staining, protein structural simulation, protein stability (half-life) assay, CCK-8 viability assay, apoptosis assay, xenograft mouse model with bioluminescence imaging\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional KD with multiple cellular and in vivo readouts from a single lab\",\n      \"pmids\": [\"37805164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"lncRNA AABR07005593.1 binds directly to MCCC1 protein and, through this interaction, promotes activation of the NF-κB pathway and upregulation of IL-6 in PM2.5-stimulated alveolar macrophages.\",\n      \"method\": \"ChIRP-MS (comprehensive identification of RNA-binding proteins by mass spectrometry), western blot, RNA interference\",\n      \"journal\": \"Ecotoxicology and environmental safety\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIRP-MS identified the interaction with orthogonal western blot validation; single lab, mechanistic pathway placement via RNAi\",\n      \"pmids\": [\"34619471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"lncBADR binds directly to Mccc1 (and Pcca) in T cells, inhibiting branched-chain amino acid (BCAA) degradation and causing intracellular BCAA accumulation, which activates the mTOR-Stat1 signaling pathway and promotes IFN-γ secretion. T cell-specific lncBADR knockout restored BCAA degradation and reduced pathogenic T cell function in experimental autoimmune encephalomyelitis.\",\n      \"method\": \"T cell-specific lncBADR knockout mice, EAE model, RNA-protein binding assay, metabolic assay, mTOR-Stat1 pathway analysis, IFN-γ measurement, high-BCAA feeding rescue experiment\",\n      \"journal\": \"Journal of neuroinflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with in vivo disease model and rescue experiment; binding to Mccc1 established biochemically; single lab\",\n      \"pmids\": [\"41013574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The biotin-containing enzyme MCCC1 directly binds corosolic acid (CA) and its derivatives. Using a CA-biotin chemical probe and avidin-biotin affinity pull-down followed by quantitative proteomics, MCCC1 was identified as a direct binding target of CA. The interaction was validated in vitro, and CA/derivative H26 modulate insulin resistance signaling through MCCC1.\",\n      \"method\": \"Chemical probe (CA-biotin), avidin-biotin affinity pull-down, quantitative proteomics, in vitro binding validation, insulin resistance signaling assay, diabetic mouse model\",\n      \"journal\": \"European journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chemical probe affinity pull-down with MS identification and in vitro validation; single lab\",\n      \"pmids\": [\"39731787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The intronic PD-risk variant rs12637471 in MCCC1 regulates MCCC1 mRNA expression: G-allele carriers show significantly elevated MCCC1 mRNA in postmortem brain tissue. CRISPR/Cas9-edited isogenic iPSC-derived dopaminergic neurons differing only at rs12637471 showed increased MCCC1 expression in G-allele lines, establishing a causal regulatory relationship.\",\n      \"method\": \"Postmortem brain mRNA quantification, CRISPR/Cas9 isogenic iPSC lines, dopaminergic neuron differentiation, qPCR/expression analysis, eQTL validation with GTEx\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — isogenic CRISPR editing provides direct causal evidence; replicated with postmortem brain data and orthogonal GTEx eQTL data\",\n      \"pmids\": [\"40216992\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MCCC1 (MCCA) encodes the biotin-containing alpha-subunit of the mitochondrial 3-methylcrotonyl-CoA carboxylase heterodimer, where it catalyzes a key step in leucine catabolism; beyond its enzymatic role, MCCC1 interacts with the pro-apoptotic protein Bad to regulate apoptotic signaling and mitochondrial integrity, is bound by regulatory lncRNAs (AABR07005593.1 and lncBADR) that co-opt its function to modulate NF-κB/IL-6 and mTOR-Stat1/IFN-γ pathways respectively, directly binds small-molecule ligands such as corosolic acid with implications for insulin resistance, and its expression in dopaminergic neurons is causally regulated by the Parkinson's disease-associated intronic variant rs12637471 via a CRISPR-validated mechanism.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MCCC1 encodes the biotin-containing alpha-subunit of mitochondrial 3-methylcrotonyl-CoA carboxylase (MCC), a biotin-dependent enzyme that catalyzes a key step in leucine catabolism; the protein carries a mitochondrial signal peptide together with biotin carboxylase and biotin-carrier domains, and is most abundant in mitochondria-rich organs [#0, #1]. Loss-of-function missense and truncating mutations in conserved residues abolish carboxylase activity in patient fibroblasts, causing 3-methylcrotonyl-CoA carboxylase deficiency [#0, #2]. Beyond catalysis, MCCC1 has emerging roles in cellular signaling: it binds the pro-apoptotic protein Bad and stabilizes it, such that MCCC1 depletion shortens Bad half-life, lowers Bax, raises anti-apoptotic Bcl-xL and Mcl-1, and induces mitochondrial dysfunction and multidrug resistance [#3]. Its catabolic activity is also a target of regulatory lncRNAs: lncBADR binds MCCC1 to inhibit branched-chain amino acid degradation, driving BCAA accumulation that activates mTOR-Stat1 signaling and IFN-\\u03b3 secretion in pathogenic T cells, while AABR07005593.1 binds MCCC1 to promote NF-\\u03baB activation and IL-6 induction [#4, #5]. A Parkinson's disease-associated intronic variant, rs12637471, causally elevates MCCC1 expression in dopaminergic neurons, as shown in isogenic CRISPR-edited iPSC lines [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing the molecular identity of MCCC1 answered what gene product underlies one branch of leucine catabolism and what its disease relevance is, defining it as the biotin-dependent alpha-subunit of MCC whose mutation abolishes enzyme activity.\",\n      \"evidence\": \"cDNA cloning, genomic sequencing, chromosomal mapping, and patient mutation identification with fibroblast enzyme assays; replicated tissue expression analysis\",\n      \"pmids\": [\"11406611\", \"11401427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural data on the human holoenzyme\", \"Stoichiometry and assembly with the beta-subunit not resolved in these studies\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Functional complementation showed that conserved-residue missense mutations are directly causal for loss of carboxylase activity, linking specific structural positions to catalytic competence.\",\n      \"evidence\": \"Transient transfection of patient-derived deficient fibroblasts with enzyme activity readout plus homology modelling onto E. coli acetyl-CoA carboxylase\",\n      \"pmids\": [\"14680978\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural inference is computational, not a human crystal structure\", \"Does not address regulation of the enzyme in vivo\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identifying MCCC1 as a direct binding partner of lncRNA AABR07005593.1 extended its role beyond metabolism into inflammatory signaling.\",\n      \"evidence\": \"ChIRP-MS with western blot validation and RNAi pathway placement in PM2.5-stimulated alveolar macrophages\",\n      \"pmids\": [\"34619471\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab without reciprocal validation\", \"Mechanism by which MCCC1 binding drives NF-\\u03baB activation is undefined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The MCCC1-Bad interaction connected the enzyme to apoptotic regulation, showing it stabilizes a pro-apoptotic protein and that its loss reprograms the Bcl-2 family balance toward survival and drug resistance.\",\n      \"evidence\": \"Reciprocal Co-IP, structural simulation, Bad half-life assay, apoptosis assays, and xenograft model in multiple myeloma cells\",\n      \"pmids\": [\"37805164\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Molecular basis of MCCC1-mediated Bad stabilization not defined\", \"Whether catalytic activity is required for the apoptotic role is untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Chemical-probe target identification revealed MCCC1 as a direct small-molecule binding target of corosolic acid, linking the enzyme to insulin resistance signaling.\",\n      \"evidence\": \"CA-biotin affinity pull-down with quantitative proteomics, in vitro binding validation, and diabetic mouse model\",\n      \"pmids\": [\"39731787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Binding site and effect on enzymatic activity unresolved\", \"Causal contribution of MCCC1 to the insulin phenotype not isolated genetically\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Two studies established MCCC1 as a regulated node: lncBADR binding inhibits BCAA degradation to drive mTOR-Stat1/IFN-\\u03b3 in pathogenic T cells, and a PD-risk variant causally elevates MCCC1 expression in dopaminergic neurons.\",\n      \"evidence\": \"T cell-specific lncBADR knockout EAE model with metabolic rescue; CRISPR/Cas9 isogenic iPSC-derived dopaminergic neurons with postmortem brain and GTEx eQTL corroboration\",\n      \"pmids\": [\"41013574\", \"40216992\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of elevated MCCC1 in dopaminergic neurons for PD pathology unknown\", \"lncBADR mechanism of inhibiting MCCC1 catalysis not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MCCC1's canonical carboxylase activity is mechanistically coupled to its non-metabolic roles in apoptosis, inflammation, and neuronal disease risk remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human holoenzyme structure\", \"Unclear whether enzymatic and signaling functions are separable\", \"Causal link between MCCC1 dosage and Parkinson's disease neurodegeneration not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"complexes\": [\"3-methylcrotonyl-CoA carboxylase (MCC)\"],\n    \"partners\": [\"BAD\", \"AABR07005593.1\", \"lncBADR\", \"PCCA\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}