{"gene":"TMEM126A","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":2009,"finding":"TMEM126A encodes a transmembrane mitochondrial protein; mutations in TMEM126A cause autosomal-recessive nonsyndromic optic atrophy, establishing its essential role in mitochondrial function in retinal ganglion cells.","method":"Whole-genome homozygosity mapping, positional cloning, subcellular localization (mitochondrial)","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — disease gene identification with mitochondrial localization; single study, multiple genetic families","pmids":["19327736"],"is_preprint":false},{"year":2013,"finding":"TMEM126A mRNA is enriched near mitochondria (mitochondrial located mRNA, MLR), the protein localizes to the inner mitochondrial membrane (cristae), and the second transmembrane domain is required for mitochondrial localization.","method":"Quantitative FISH, cellular fractionation, mitochondrial sub-compartmentalization by proteolysis assay and transmission electron microscopy, immunofluorescence confocal microscopy of truncated constructs","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal localization methods including proteolysis protection assay, EM, fractionation, and domain mutagenesis in a single study","pmids":["23500070"],"is_preprint":false},{"year":2012,"finding":"TMEM126A associates and co-localizes with CD137L (4-1BB ligand) in macrophages; knockdown of TMEM126A abolishes CD137L-induced tyrosine phosphorylation and regulation of pro-inflammatory cytokines (M-CSF, IL-1β, TN-C), and blocks CD137L-induced cell adherence.","method":"Yeast two-hybrid, co-localization, siRNA knockdown, stable retroviral shRNA transduction, cytokine expression assay, phosphorylation assay","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2-3 — yeast two-hybrid plus co-localization and functional knockdown; single lab, multiple methods but context may differ from mitochondrial function","pmids":["22885069"],"is_preprint":false},{"year":2014,"finding":"TMEM126A couples with TLR4 signal transduction in macrophages; loss of TMEM126A diminishes LPS/TLR4-induced upregulation of CD54, MHC II, CD86, CD40 and abolishes late-phase JNK/SAPK and IRF-3 phosphorylation.","method":"siRNA knockdown in RAW264.7 macrophages, flow cytometry, phosphorylation assays","journal":"Molecular immunology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single method set, and functional context (TLR4 signaling) may not reflect primary mitochondrial function","pmids":["25549946"],"is_preprint":false},{"year":2018,"finding":"Loss of TMEM126A induces mitochondrial dysfunction (ROS production and mitochondrial membrane potential depolarization), which activates extracellular matrix remodeling and EMT in breast cancer cells; ROS scavengers reverse these effects, placing TMEM126A upstream of ROS-mediated retrograde signaling.","method":"siRNA knockdown, overexpression, ROS measurement, mitochondrial membrane potential assay, RNA-seq, in vitro and in vivo metastasis assays, ROS scavenger rescue","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods with epistasis via ROS scavenger rescue; single lab","pmids":["30393159"],"is_preprint":false},{"year":2021,"finding":"TMEM126A is an assembly factor for the ND4-module of mitochondrial complex I; loss of TMEM126A causes isolated complex I deficiency, and TMEM126A interacts with newly synthesized mtDNA-encoded ND4 subunit as revealed by pulse-labeling interaction studies. Its function is distinct from paralogue TMEM126B (ND2-module assembly).","method":"Genome editing (CRISPR KO), interaction studies (co-immunoprecipitation), quantitative proteomics, pulse-labeling interaction studies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (genome editing, pulse-labeling Co-IP, quantitative proteomics) in a single rigorous study; independently replicated by D'Angelo et al. 2021","pmids":["33879611"],"is_preprint":false},{"year":2021,"finding":"TMEM126A (OPA7) is bound to the stable ND4 module intermediate during complex I disassembly; hierarchical ablation of NDUFS3 revealed that the ND4 module remains stable and associated with TMEM126A, confirming TMEM126A as a factor necessary for correct assembly and function of complex I.","method":"NDUFS3 ablation/gradual depletion in mammalian cell types, native PAGE, co-immunoprecipitation, BN-PAGE complex profiling","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 — independent replication of TMEM126A as ND4-module assembly factor using complementary NDUFS3-depletion approach; consistent with Formosa et al. 2021","pmids":["33882309"],"is_preprint":false},{"year":2024,"finding":"TMEM126A interacts with OXA1L (the mitochondrial inner membrane insertase) and associates with mitochondrial ribosomes and translation products; loss of TMEM126A destabilizes newly synthesized mitochondrial translation products, which are degraded by the iAAA protease, and causes cargo-blocked OXA1L complexes to also undergo iAAA-mediated proteolytic clearance, revealing a cotranslational quality control function.","method":"Co-immunoprecipitation (OXA1L pulldown), ribosome association assays, mass spectrometry interactomics, loss-of-function (KO), protease activity assays, iAAA protease functional analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal biochemical methods (Co-IP, ribosome association, MS, protease assays) establishing a novel mechanistic role; published in top-tier journal","pmids":["38199007"],"is_preprint":false},{"year":2024,"finding":"Integrative XL-MS, 3D electron microscopy, and coarse-grained molecular dynamics simulations localize TMEM126A to the cristae of the inner mitochondrial membrane, validated by super-resolution microscopy.","method":"Cross-linking mass spectrometry, 3D electron microscopy, coarse-grained molecular dynamics simulation, super-resolution microscopy","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods for localization with super-resolution validation; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2024.09.11.612425"],"is_preprint":true}],"current_model":"TMEM126A is an inner mitochondrial membrane (cristae) protein that functions as an assembly factor for the ND4-module of mitochondrial complex I by cooperating with the OXA1L insertase during cotranslational insertion of mtDNA-encoded subunits, and its loss triggers iAAA protease-mediated quality control degradation of newly synthesized membrane proteins and complex I deficiency."},"narrative":{"teleology":[{"year":2009,"claim":"Identifying TMEM126A as a mitochondrial protein whose loss causes hereditary optic atrophy established that it is essential for mitochondrial function in retinal ganglion cells, but its molecular role was unknown.","evidence":"Homozygosity mapping and positional cloning in consanguineous families with autosomal-recessive optic atrophy, plus mitochondrial localization","pmids":["19327736"],"confidence":"Medium","gaps":["Single disease cohort at time of publication","No molecular function or pathway identified","Mechanism of retinal ganglion cell vulnerability unresolved"]},{"year":2013,"claim":"Demonstrating that TMEM126A resides specifically at the inner mitochondrial membrane (cristae) and that its second transmembrane domain is required for targeting resolved the sub-organellar compartment of action.","evidence":"Quantitative FISH, proteolysis protection assays, transmission EM, fractionation, and domain-truncation confocal microscopy","pmids":["23500070"],"confidence":"High","gaps":["No interaction partners or respiratory chain connection identified","How the second TM domain mediates targeting is structurally unresolved"]},{"year":2012,"claim":"An extramitochondrial role was proposed in which TMEM126A associates with CD137L and mediates macrophage inflammatory signaling, but this function diverges from the core mitochondrial role and has not been independently replicated.","evidence":"Yeast two-hybrid, co-localization, siRNA knockdown, and cytokine/phosphorylation assays in macrophages","pmids":["22885069"],"confidence":"Medium","gaps":["No reciprocal Co-IP or endogenous interaction confirmation","Not independently replicated","Relationship to mitochondrial complex I function unclear"]},{"year":2018,"claim":"Connecting TMEM126A loss to mitochondrial ROS production and membrane potential depolarization showed that its deficiency causes retrograde mitochondrial-to-nuclear signaling, but the direct molecular target remained unknown.","evidence":"siRNA knockdown and overexpression in breast cancer cells with ROS measurement, membrane potential assays, RNA-seq, and ROS-scavenger epistasis rescue","pmids":["30393159"],"confidence":"Medium","gaps":["Downstream EMT effects studied in cancer cell lines only","Direct respiratory chain target not identified in this study"]},{"year":2021,"claim":"Two independent studies converged to establish TMEM126A as a specific assembly factor for the ND4-module of complex I — distinct from its paralogue TMEM126B (ND2-module) — explaining the isolated complex I deficiency seen upon its loss.","evidence":"CRISPR KO, pulse-labeling Co-IP with newly synthesized ND4, quantitative proteomics (Formosa et al.); NDUFS3 ablation, BN-PAGE, native complex profiling (D'Angelo et al.)","pmids":["33879611","33882309"],"confidence":"High","gaps":["Structural basis of ND4 interaction unknown","Cooperative relationship with OXA1L not yet defined","How TMEM126A is itself recruited to the assembly intermediate unclear"]},{"year":2024,"claim":"Revealing that TMEM126A cooperates with the OXA1L insertase and associates with mitochondrial ribosomes established a cotranslational membrane insertion role, while showing that loss triggers iAAA protease-mediated clearance of stalled translation products and cargo-blocked OXA1L uncovered a quality-control checkpoint.","evidence":"OXA1L Co-IP, ribosome association assays, mass spectrometry interactomics, TMEM126A KO with iAAA protease functional analysis","pmids":["38199007"],"confidence":"High","gaps":["Structural details of the TMEM126A–OXA1L–ribosome complex are unknown","Whether TMEM126A assists insertion of subunits beyond ND4 is unresolved","In vivo relevance of iAAA quality-control pathway in optic atrophy pathogenesis not tested"]},{"year":null,"claim":"A high-resolution structure of TMEM126A in complex with OXA1L and/or the ND4-module assembly intermediate is needed to understand the mechanism of cotranslational insertion and how disease mutations disrupt it.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of TMEM126A or its complexes","Tissue-specific vulnerability (retinal ganglion cells) mechanistically unexplained","No therapeutic strategy for TMEM126A-linked optic atrophy"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,6,7]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,5,7]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[5,6,7]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,6]}],"complexes":["Mitochondrial complex I (ND4-module assembly intermediate)"],"partners":["ND4","OXA1L","TMEM126B"],"other_free_text":[]},"mechanistic_narrative":"TMEM126A is a mitochondrial inner membrane protein that functions as a dedicated assembly factor for the ND4-module of respiratory chain complex I. It localizes to the cristae membrane, where its second transmembrane domain is required for mitochondrial targeting, and it interacts cotranslationally with newly synthesized mtDNA-encoded ND4 subunit via cooperation with the OXA1L insertase and mitochondrial ribosomes [PMID:33879611, PMID:38199007]. Loss of TMEM126A causes isolated complex I deficiency by destabilizing nascent mitochondrial translation products, which are then cleared by the iAAA protease together with cargo-blocked OXA1L complexes, revealing a cotranslational quality-control checkpoint at the inner membrane [PMID:38199007, PMID:33882309]. Biallelic mutations in TMEM126A cause autosomal-recessive nonsyndromic optic atrophy [PMID:19327736]."},"prefetch_data":{"uniprot":{"accession":"Q9H061","full_name":"Transmembrane protein 126A","aliases":[],"length_aa":195,"mass_kda":21.5,"function":"Protein required for the cotranslational protein quality control in the inner membrane of the mitochondria (PubMed:38199007). Associates with newly synthesized polypeptides and may act as a chaperone that cooperates with OXA1L for the insertion of newly synthesized mitochondrial proteins into the inner membrane (PubMed:38199007). Required for the assembly of the ND4 module of mitochondrial complex I (PubMed:33879611, PubMed:33882309)","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/Q9H061/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TMEM126A","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/TMEM126A","total_profiled":1310},"omim":[{"mim_id":"612989","title":"OPTIC ATROPHY 7 WITH OR WITHOUT AUDITORY NEUROPATHY; OPA7","url":"https://www.omim.org/entry/612989"},{"mim_id":"612988","title":"TRANSMEMBRANE PROTEIN 126A; TMEM126A","url":"https://www.omim.org/entry/612988"},{"mim_id":"165500","title":"OPTIC ATROPHY 1; OPA1","url":"https://www.omim.org/entry/165500"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TMEM126A"},"hgnc":{"alias_symbol":["DKFZp586C1924","OPA7"],"prev_symbol":[]},"alphafold":{"accession":"Q9H061","domains":[{"cath_id":"-","chopping":"35-187","consensus_level":"medium","plddt":93.5639,"start":35,"end":187}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H061","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H061-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H061-F1-predicted_aligned_error_v6.png","plddt_mean":90.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TMEM126A","jax_strain_url":"https://www.jax.org/strain/search?query=TMEM126A"},"sequence":{"accession":"Q9H061","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H061.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H061/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H061"}},"corpus_meta":[{"pmid":"19327736","id":"PMC_19327736","title":"TMEM126A, encoding a mitochondrial protein, is mutated in autosomal-recessive nonsyndromic optic atrophy.","date":"2009","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19327736","citation_count":76,"is_preprint":false},{"pmid":"20405026","id":"PMC_20405026","title":"Nonsense mutation in TMEM126A causing autosomal recessive optic atrophy and auditory neuropathy.","date":"2010","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/20405026","citation_count":39,"is_preprint":false},{"pmid":"30393159","id":"PMC_30393159","title":"Loss of TMEM126A promotes extracellular matrix remodeling, epithelial-to-mesenchymal transition, and breast cancer metastasis by regulating mitochondrial retrograde signaling.","date":"2018","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/30393159","citation_count":29,"is_preprint":false},{"pmid":"33882309","id":"PMC_33882309","title":"NDUFS3 depletion permits complex I maturation and reveals TMEM126A/OPA7 as an assembly factor binding the ND4-module intermediate.","date":"2021","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/33882309","citation_count":23,"is_preprint":false},{"pmid":"23500070","id":"PMC_23500070","title":"TMEM126A is a mitochondrial located mRNA (MLR) protein of the mitochondrial inner membrane.","date":"2013","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/23500070","citation_count":21,"is_preprint":false},{"pmid":"33879611","id":"PMC_33879611","title":"Optic atrophy-associated TMEM126A is an assembly factor for the ND4-module of mitochondrial complex I.","date":"2021","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/33879611","citation_count":21,"is_preprint":false},{"pmid":"38199007","id":"PMC_38199007","title":"Identification of TMEM126A as OXA1L-interacting protein reveals cotranslational quality control in mitochondria.","date":"2024","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/38199007","citation_count":18,"is_preprint":false},{"pmid":"22815638","id":"PMC_22815638","title":"TMEM126A mutation in a Moroccan family with autosomal recessive optic atrophy.","date":"2012","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/22815638","citation_count":18,"is_preprint":false},{"pmid":"22885069","id":"PMC_22885069","title":"Novel transmembrane protein 126A (TMEM126A) couples with CD137L reverse signals in myeloid cells.","date":"2012","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/22885069","citation_count":11,"is_preprint":false},{"pmid":"25549946","id":"PMC_25549946","title":"TMEM126A, a CD137 ligand binding protein, couples with the TLR4 signal transduction pathway in macrophages.","date":"2014","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/25549946","citation_count":10,"is_preprint":false},{"pmid":"30961538","id":"PMC_30961538","title":"Novel likely pathogenic variants in TMEM126A identified in non-syndromic autosomal recessive optic atrophy: two case reports.","date":"2019","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30961538","citation_count":10,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.17.676758","title":"Proteomic and Kinetic Characterization of Prion Seeding in Distinct Human CJD Strains Unveils Early Diagnostic Biomarkers","date":"2025-09-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.17.676758","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.11.612425","title":"Integrative Molecular Dynamics Simulations Untangle Cross-Linking Data to Unveil Mitochondrial Protein Distributions","date":"2024-09-13","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.11.612425","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7682,"output_tokens":2180,"usd":0.027873},"stage2":{"model":"claude-opus-4-6","input_tokens":5474,"output_tokens":1763,"usd":0.107167},"total_usd":0.13504,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"TMEM126A encodes a transmembrane mitochondrial protein; mutations in TMEM126A cause autosomal-recessive nonsyndromic optic atrophy, establishing its essential role in mitochondrial function in retinal ganglion cells.\",\n      \"method\": \"Whole-genome homozygosity mapping, positional cloning, subcellular localization (mitochondrial)\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — disease gene identification with mitochondrial localization; single study, multiple genetic families\",\n      \"pmids\": [\"19327736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TMEM126A mRNA is enriched near mitochondria (mitochondrial located mRNA, MLR), the protein localizes to the inner mitochondrial membrane (cristae), and the second transmembrane domain is required for mitochondrial localization.\",\n      \"method\": \"Quantitative FISH, cellular fractionation, mitochondrial sub-compartmentalization by proteolysis assay and transmission electron microscopy, immunofluorescence confocal microscopy of truncated constructs\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal localization methods including proteolysis protection assay, EM, fractionation, and domain mutagenesis in a single study\",\n      \"pmids\": [\"23500070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TMEM126A associates and co-localizes with CD137L (4-1BB ligand) in macrophages; knockdown of TMEM126A abolishes CD137L-induced tyrosine phosphorylation and regulation of pro-inflammatory cytokines (M-CSF, IL-1β, TN-C), and blocks CD137L-induced cell adherence.\",\n      \"method\": \"Yeast two-hybrid, co-localization, siRNA knockdown, stable retroviral shRNA transduction, cytokine expression assay, phosphorylation assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — yeast two-hybrid plus co-localization and functional knockdown; single lab, multiple methods but context may differ from mitochondrial function\",\n      \"pmids\": [\"22885069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TMEM126A couples with TLR4 signal transduction in macrophages; loss of TMEM126A diminishes LPS/TLR4-induced upregulation of CD54, MHC II, CD86, CD40 and abolishes late-phase JNK/SAPK and IRF-3 phosphorylation.\",\n      \"method\": \"siRNA knockdown in RAW264.7 macrophages, flow cytometry, phosphorylation assays\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single method set, and functional context (TLR4 signaling) may not reflect primary mitochondrial function\",\n      \"pmids\": [\"25549946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Loss of TMEM126A induces mitochondrial dysfunction (ROS production and mitochondrial membrane potential depolarization), which activates extracellular matrix remodeling and EMT in breast cancer cells; ROS scavengers reverse these effects, placing TMEM126A upstream of ROS-mediated retrograde signaling.\",\n      \"method\": \"siRNA knockdown, overexpression, ROS measurement, mitochondrial membrane potential assay, RNA-seq, in vitro and in vivo metastasis assays, ROS scavenger rescue\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods with epistasis via ROS scavenger rescue; single lab\",\n      \"pmids\": [\"30393159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TMEM126A is an assembly factor for the ND4-module of mitochondrial complex I; loss of TMEM126A causes isolated complex I deficiency, and TMEM126A interacts with newly synthesized mtDNA-encoded ND4 subunit as revealed by pulse-labeling interaction studies. Its function is distinct from paralogue TMEM126B (ND2-module assembly).\",\n      \"method\": \"Genome editing (CRISPR KO), interaction studies (co-immunoprecipitation), quantitative proteomics, pulse-labeling interaction studies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (genome editing, pulse-labeling Co-IP, quantitative proteomics) in a single rigorous study; independently replicated by D'Angelo et al. 2021\",\n      \"pmids\": [\"33879611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TMEM126A (OPA7) is bound to the stable ND4 module intermediate during complex I disassembly; hierarchical ablation of NDUFS3 revealed that the ND4 module remains stable and associated with TMEM126A, confirming TMEM126A as a factor necessary for correct assembly and function of complex I.\",\n      \"method\": \"NDUFS3 ablation/gradual depletion in mammalian cell types, native PAGE, co-immunoprecipitation, BN-PAGE complex profiling\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — independent replication of TMEM126A as ND4-module assembly factor using complementary NDUFS3-depletion approach; consistent with Formosa et al. 2021\",\n      \"pmids\": [\"33882309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TMEM126A interacts with OXA1L (the mitochondrial inner membrane insertase) and associates with mitochondrial ribosomes and translation products; loss of TMEM126A destabilizes newly synthesized mitochondrial translation products, which are degraded by the iAAA protease, and causes cargo-blocked OXA1L complexes to also undergo iAAA-mediated proteolytic clearance, revealing a cotranslational quality control function.\",\n      \"method\": \"Co-immunoprecipitation (OXA1L pulldown), ribosome association assays, mass spectrometry interactomics, loss-of-function (KO), protease activity assays, iAAA protease functional analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal biochemical methods (Co-IP, ribosome association, MS, protease assays) establishing a novel mechanistic role; published in top-tier journal\",\n      \"pmids\": [\"38199007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Integrative XL-MS, 3D electron microscopy, and coarse-grained molecular dynamics simulations localize TMEM126A to the cristae of the inner mitochondrial membrane, validated by super-resolution microscopy.\",\n      \"method\": \"Cross-linking mass spectrometry, 3D electron microscopy, coarse-grained molecular dynamics simulation, super-resolution microscopy\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods for localization with super-resolution validation; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.09.11.612425\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"TMEM126A is an inner mitochondrial membrane (cristae) protein that functions as an assembly factor for the ND4-module of mitochondrial complex I by cooperating with the OXA1L insertase during cotranslational insertion of mtDNA-encoded subunits, and its loss triggers iAAA protease-mediated quality control degradation of newly synthesized membrane proteins and complex I deficiency.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TMEM126A is a mitochondrial inner membrane protein that functions as a dedicated assembly factor for the ND4-module of respiratory chain complex I. It localizes to the cristae membrane, where its second transmembrane domain is required for mitochondrial targeting, and it interacts cotranslationally with newly synthesized mtDNA-encoded ND4 subunit via cooperation with the OXA1L insertase and mitochondrial ribosomes [PMID:33879611, PMID:38199007]. Loss of TMEM126A causes isolated complex I deficiency by destabilizing nascent mitochondrial translation products, which are then cleared by the iAAA protease together with cargo-blocked OXA1L complexes, revealing a cotranslational quality-control checkpoint at the inner membrane [PMID:38199007, PMID:33882309]. Biallelic mutations in TMEM126A cause autosomal-recessive nonsyndromic optic atrophy [PMID:19327736].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Identifying TMEM126A as a mitochondrial protein whose loss causes hereditary optic atrophy established that it is essential for mitochondrial function in retinal ganglion cells, but its molecular role was unknown.\",\n      \"evidence\": \"Homozygosity mapping and positional cloning in consanguineous families with autosomal-recessive optic atrophy, plus mitochondrial localization\",\n      \"pmids\": [\"19327736\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single disease cohort at time of publication\", \"No molecular function or pathway identified\", \"Mechanism of retinal ganglion cell vulnerability unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrating that TMEM126A resides specifically at the inner mitochondrial membrane (cristae) and that its second transmembrane domain is required for targeting resolved the sub-organellar compartment of action.\",\n      \"evidence\": \"Quantitative FISH, proteolysis protection assays, transmission EM, fractionation, and domain-truncation confocal microscopy\",\n      \"pmids\": [\"23500070\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No interaction partners or respiratory chain connection identified\", \"How the second TM domain mediates targeting is structurally unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"An extramitochondrial role was proposed in which TMEM126A associates with CD137L and mediates macrophage inflammatory signaling, but this function diverges from the core mitochondrial role and has not been independently replicated.\",\n      \"evidence\": \"Yeast two-hybrid, co-localization, siRNA knockdown, and cytokine/phosphorylation assays in macrophages\",\n      \"pmids\": [\"22885069\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal Co-IP or endogenous interaction confirmation\", \"Not independently replicated\", \"Relationship to mitochondrial complex I function unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connecting TMEM126A loss to mitochondrial ROS production and membrane potential depolarization showed that its deficiency causes retrograde mitochondrial-to-nuclear signaling, but the direct molecular target remained unknown.\",\n      \"evidence\": \"siRNA knockdown and overexpression in breast cancer cells with ROS measurement, membrane potential assays, RNA-seq, and ROS-scavenger epistasis rescue\",\n      \"pmids\": [\"30393159\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream EMT effects studied in cancer cell lines only\", \"Direct respiratory chain target not identified in this study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Two independent studies converged to establish TMEM126A as a specific assembly factor for the ND4-module of complex I — distinct from its paralogue TMEM126B (ND2-module) — explaining the isolated complex I deficiency seen upon its loss.\",\n      \"evidence\": \"CRISPR KO, pulse-labeling Co-IP with newly synthesized ND4, quantitative proteomics (Formosa et al.); NDUFS3 ablation, BN-PAGE, native complex profiling (D'Angelo et al.)\",\n      \"pmids\": [\"33879611\", \"33882309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ND4 interaction unknown\", \"Cooperative relationship with OXA1L not yet defined\", \"How TMEM126A is itself recruited to the assembly intermediate unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealing that TMEM126A cooperates with the OXA1L insertase and associates with mitochondrial ribosomes established a cotranslational membrane insertion role, while showing that loss triggers iAAA protease-mediated clearance of stalled translation products and cargo-blocked OXA1L uncovered a quality-control checkpoint.\",\n      \"evidence\": \"OXA1L Co-IP, ribosome association assays, mass spectrometry interactomics, TMEM126A KO with iAAA protease functional analysis\",\n      \"pmids\": [\"38199007\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural details of the TMEM126A–OXA1L–ribosome complex are unknown\", \"Whether TMEM126A assists insertion of subunits beyond ND4 is unresolved\", \"In vivo relevance of iAAA quality-control pathway in optic atrophy pathogenesis not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of TMEM126A in complex with OXA1L and/or the ND4-module assembly intermediate is needed to understand the mechanism of cotranslational insertion and how disease mutations disrupt it.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution structure of TMEM126A or its complexes\", \"Tissue-specific vulnerability (retinal ganglion cells) mechanistically unexplained\", \"No therapeutic strategy for TMEM126A-linked optic atrophy\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 5, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [5, 6, 7]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"complexes\": [\n      \"Mitochondrial complex I (ND4-module assembly intermediate)\"\n    ],\n    \"partners\": [\n      \"ND4\",\n      \"OXA1L\",\n      \"TMEM126B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}