{"gene":"TMEM126B","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2013,"finding":"TMEM126B is associated with subcomplexes of mitochondrial complex I (550 kDa and 815 kDa) that accumulate when NDUFA11 expression is suppressed, suggesting TMEM126B participates in constructing the membrane arm of complex I.","method":"Suppression of NDUFA11 expression, subcomplex isolation, mass spectrometry identification of associated proteins","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based co-fractionation with subcomplexes, single lab, but subcomplex identity and protein association established by two orthogonal approaches","pmids":["24191001"],"is_preprint":false},{"year":2016,"finding":"TMEM126B is a component of the mitochondrial complex I assembly complex (alongside ACAD9, ECSIT, NDUFAF1, and TIMMDC1), and biallelic loss-of-function variants in TMEM126B cause severe complex I deficiency; viral rescue of TMEM126B in patient cell lines restores complex I assembly as shown by complexome profiling.","method":"Complexome profiling, viral rescue experiments, patient cell line functional analysis, whole-exome sequencing","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal complexome profiling plus viral rescue rescue in patient cells, replicated across multiple families and labs","pmids":["27374774"],"is_preprint":false},{"year":2020,"finding":"TMEM126B is a core component of the mitochondrial complex I intermediate assembly (MCIA) complex required for building the ND2-module of complex I; within the MCIA complex a hierarchy of stability exists centered on ACAD9, and loss of TMEM126B destabilizes the entire MCIA complex and blocks ND2-module assembly.","method":"CRISPR/Cas9 knockout of each MCIA component, quantitative proteomics, complexome profiling, co-immunoprecipitation","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO, quantitative proteomics, complexome profiling, Co-IP) in single rigorous study","pmids":["32320651"],"is_preprint":false},{"year":2018,"finding":"TMEM126B knockdown in THP-1 macrophages reduces complex I assembly and attenuates mitochondrial ROS production upon LPS stimulation; reduced mtROS in TMEM126B-knockdown cells leads to decreased oxidation of SDHA, preserving SDH activity and thereby reducing HIF-1α stabilization and IL-1β expression.","method":"shRNA knockdown, BIAM switch assay coupled to LC-MS for protein oxidation, SDH activity assay, HIF-1α and IL-1β measurement, pharmacological SDH inhibition rescue","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA KD with multiple downstream readouts and pharmacological rescue in single lab","pmids":["30368040"],"is_preprint":false},{"year":2018,"finding":"Under chronic hypoxia, HIF-1α induces the E3-ubiquitin ligase β-TrCP1, which facilitates proteolytic degradation of TMEM126B, leading to reduced MCIA complex abundance and impaired complex I assembly.","method":"Complexome profiling of isolated mitochondria under hypoxia, HIF-1α inhibition/activation experiments, β-TrCP1 modulation, protein stability assays","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — complexome profiling plus genetic/pharmacological perturbation of HIF-1α and β-TrCP1, single lab","pmids":["29464284"],"is_preprint":false},{"year":2021,"finding":"TMEM126B and its paralogue TMEM126A have distinct functions in complex I assembly: TMEM126B acts in assembly of the ND2-module, whereas TMEM126A acts in assembly of the ND4 distal membrane module.","method":"Genome editing (knockout), pulse-labeling interaction studies with newly synthesized mtDNA-encoded subunits, quantitative proteomics, co-immunoprecipitation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal KO, pulse-labeling, and quantitative proteomics providing functional distinction between paralogs","pmids":["33879611"],"is_preprint":false},{"year":2017,"finding":"The TMEM126B p.G212V missense mutation causes incomplete assembly of the peripheral arm of complex I, reducing mature complex I levels; complementation of patient fibroblasts with wild-type TMEM126B rescues complex I assembly, confirming the assembly factor role.","method":"Whole-exome sequencing, complementation study in patient fibroblasts, OXPHOS capacity measurement, BN-PAGE complex I assessment","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — complementation in patient fibroblasts with functional readout, single lab","pmids":["29093663"],"is_preprint":false},{"year":2022,"finding":"Novel intronic (c.82-2 A>G) and exonic insertion (c.290dupT) TMEM126B mutations cause exon skipping (complete exon 2 skipping and partial/complete exon 3 skipping, respectively), leading to frameshifts, premature termination, loss of TMEM126B protein, and severe complex I assembly defect in patient lymphocytes.","method":"Minigene splicing assay, patient RNA analysis, functional analysis of complex I content and assembly in patient-derived lymphocytes","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — minigene splicing assays combined with patient RNA and functional complex I analysis, single lab","pmids":["36482121"],"is_preprint":false}],"current_model":"TMEM126B is an integral component of the mitochondrial complex I intermediate assembly (MCIA) complex (with ACAD9, ECSIT, NDUFAF1, and TIMMDC1) that is specifically required for biogenesis of the ND2-module of the membrane arm of complex I; it is subject to HIF-1α–induced proteasomal degradation via β-TrCP1 under chronic hypoxia, and its loss reduces mitochondrial ROS signaling with downstream effects on SDHA oxidation, HIF-1α stabilization, and IL-1β expression in macrophages."},"narrative":{"mechanistic_narrative":"TMEM126B is a core subunit of the mitochondrial complex I intermediate assembly (MCIA) complex—together with ACAD9, ECSIT, NDUFAF1, and TIMMDC1—that drives biogenesis of the membrane arm of respiratory complex I [PMID:27374774, PMID:32320651]. Within the MCIA complex, which is organized around a stability hierarchy centered on ACAD9, loss of TMEM126B destabilizes the entire assembly module and specifically blocks construction of the ND2-module, a role distinct from its paralogue TMEM126A, which instead supports assembly of the ND4 distal membrane module [PMID:32320651, PMID:33879611]. Consistent with this assembly-factor function, biallelic loss-of-function, missense, and splice-disrupting variants in TMEM126B cause severe complex I deficiency, and re-expression of wild-type TMEM126B in patient cells restores complex I assembly [PMID:27374774, PMID:29093663, PMID:36482121]. Beyond its constitutive assembly role, TMEM126B is a regulatory node coupling complex I biogenesis to redox and hypoxic signaling: its loss attenuates LPS-induced mitochondrial ROS production, reducing SDHA oxidation and thereby limiting HIF-1α stabilization and IL-1β expression in macrophages [PMID:30368040], while under chronic hypoxia HIF-1α–induced β-TrCP1 targets TMEM126B for proteolytic degradation, lowering MCIA abundance and complex I assembly [PMID:29464284].","teleology":[{"year":2013,"claim":"Established that TMEM126B physically associates with complex I biogenesis, situating an uncharacterized membrane protein within respiratory chain assembly.","evidence":"NDUFA11 suppression with subcomplex isolation and mass spectrometry identifying TMEM126B in 550/815 kDa membrane-arm subcomplexes","pmids":["24191001"],"confidence":"Medium","gaps":["Did not define which assembly step or module TMEM126B serves","Association inferred from subcomplex accumulation rather than direct functional assay"]},{"year":2016,"claim":"Defined TMEM126B as a bona fide MCIA complex component and established disease causation, answering whether its loss is pathogenic.","evidence":"Complexome profiling plus viral rescue in patient cell lines and whole-exome sequencing across families","pmids":["27374774"],"confidence":"High","gaps":["Did not resolve the specific module within complex I that requires TMEM126B","Stoichiometry and architecture within MCIA not defined"]},{"year":2017,"claim":"Confirmed the assembly-factor role through a specific missense allele, linking peripheral arm assembly defects to reduced mature complex I.","evidence":"Whole-exome sequencing and complementation of patient fibroblasts with OXPHOS and BN-PAGE readouts for the p.G212V mutation","pmids":["29093663"],"confidence":"Medium","gaps":["Single-family/single-lab functional validation","Mechanism by which the missense change disrupts assembly not resolved"]},{"year":2018,"claim":"Connected TMEM126B-dependent complex I assembly to inflammatory redox signaling, showing it is not merely a housekeeping assembly factor.","evidence":"shRNA knockdown in THP-1 macrophages with BIAM-switch LC-MS oxidation profiling, SDH activity, HIF-1α/IL-1β measurement, and pharmacological SDH inhibition rescue","pmids":["30368040"],"confidence":"Medium","gaps":["Knockdown rather than clean knockout","Causal chain from mtROS to SDHA oxidation inferred via pharmacology in a single lab","In vivo relevance not tested"]},{"year":2018,"claim":"Revealed that TMEM126B abundance is dynamically regulated, identifying HIF-1α/β-TrCP1–mediated degradation as a hypoxic control point on complex I assembly.","evidence":"Complexome profiling of mitochondria under hypoxia with HIF-1α and β-TrCP1 modulation and protein stability assays","pmids":["29464284"],"confidence":"Medium","gaps":["Direct ubiquitination site/E3 engagement not mapped","Single-lab evidence for the degradation axis"]},{"year":2020,"claim":"Resolved the module specificity and intra-complex hierarchy, showing TMEM126B is required to build the ND2-module and that its loss collapses the whole MCIA complex.","evidence":"CRISPR/Cas9 knockout of each MCIA component with quantitative proteomics, complexome profiling, and co-immunoprecipitation","pmids":["32320651"],"confidence":"High","gaps":["Atomic/structural basis of ND2-module handover not defined","Order of subunit recruitment within ND2 assembly not fully resolved"]},{"year":2021,"claim":"Distinguished TMEM126B from its paralogue TMEM126A, assigning each to a separate membrane module and clarifying non-redundant functions.","evidence":"Knockout, pulse-labeling of newly synthesized mtDNA-encoded subunits, quantitative proteomics, and co-immunoprecipitation","pmids":["33879611"],"confidence":"High","gaps":["How the two paralogues partition substrate modules mechanistically is unresolved","Whether they ever cooperate at module interfaces unknown"]},{"year":2022,"claim":"Extended the mutational spectrum to splice-disrupting alleles, showing loss of protein via exon skipping recapitulates the severe complex I defect.","evidence":"Minigene splicing assays, patient RNA analysis, and functional complex I assessment in patient lymphocytes for intronic and insertion variants","pmids":["36482121"],"confidence":"Medium","gaps":["Genotype–phenotype correlation across allele types not systematized","Single-lab functional validation"]},{"year":null,"claim":"How TMEM126B mechanistically templates ND2-module assembly and how its degradation is structurally triggered remain unresolved.","evidence":"No structural model of TMEM126B within MCIA or of its ND2-module handover is present in the corpus","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of TMEM126B in the MCIA complex","Ubiquitination determinants for β-TrCP1 not mapped","In vivo significance of the redox/hypoxia regulatory axis untested"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,2,4]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,2,5]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2]}],"complexes":["MCIA complex (mitochondrial complex I intermediate assembly complex)"],"partners":["ACAD9","ECSIT","NDUFAF1","TIMMDC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IUX1","full_name":"Complex I assembly factor TMEM126B, mitochondrial","aliases":["Transmembrane protein 126B"],"length_aa":230,"mass_kda":25.9,"function":"As part of the MCIA complex, involved in the assembly of the mitochondrial complex I (PubMed:27374773, PubMed:27374774, PubMed:32320651). Participates in constructing the membrane arm of complex I (PubMed:24191001)","subcellular_location":"Mitochondrion membrane","url":"https://www.uniprot.org/uniprotkb/Q8IUX1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TMEM126B","classification":"Not Classified","n_dependent_lines":14,"n_total_lines":1208,"dependency_fraction":0.011589403973509934},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TMEM126B","total_profiled":1310},"omim":[{"mim_id":"618250","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 29; MC1DN29","url":"https://www.omim.org/entry/618250"},{"mim_id":"615533","title":"TRANSMEMBRANE PROTEIN 126B; TMEM126B","url":"https://www.omim.org/entry/615533"},{"mim_id":"612988","title":"TRANSMEMBRANE PROTEIN 126A; TMEM126A","url":"https://www.omim.org/entry/612988"},{"mim_id":"252010","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 1; MC1DN1","url":"https://www.omim.org/entry/252010"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TMEM126B"},"hgnc":{"alias_symbol":["HT007"],"prev_symbol":[]},"alphafold":{"accession":"Q8IUX1","domains":[{"cath_id":"-","chopping":"63-226","consensus_level":"high","plddt":92.8726,"start":63,"end":226}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IUX1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IUX1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IUX1-F1-predicted_aligned_error_v6.png","plddt_mean":81.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TMEM126B","jax_strain_url":"https://www.jax.org/strain/search?query=TMEM126B"},"sequence":{"accession":"Q8IUX1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IUX1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IUX1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IUX1"}},"corpus_meta":[{"pmid":"27290639","id":"PMC_27290639","title":"New perspective in diagnostics of mitochondrial disorders: two years' experience with whole-exome sequencing at a national paediatric centre.","date":"2016","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27290639","citation_count":193,"is_preprint":false},{"pmid":"24191001","id":"PMC_24191001","title":"Assembly factors for the membrane arm of human complex I.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/24191001","citation_count":116,"is_preprint":false},{"pmid":"32320651","id":"PMC_32320651","title":"Dissecting the Roles of Mitochondrial Complex I Intermediate Assembly Complex Factors in the Biogenesis of Complex I.","date":"2020","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/32320651","citation_count":85,"is_preprint":false},{"pmid":"30368040","id":"PMC_30368040","title":"TMEM126B deficiency reduces mitochondrial SDH oxidation by LPS, attenuating HIF-1α stabilization and IL-1β expression.","date":"2018","source":"Redox biology","url":"https://pubmed.ncbi.nlm.nih.gov/30368040","citation_count":54,"is_preprint":false},{"pmid":"27374774","id":"PMC_27374774","title":"Biallelic Mutations in TMEM126B Cause Severe Complex I Deficiency with a Variable Clinical Phenotype.","date":"2016","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27374774","citation_count":54,"is_preprint":false},{"pmid":"27048931","id":"PMC_27048931","title":"The origin of the supernumerary subunits and assembly factors of complex I: A treasure trove of pathway evolution.","date":"2016","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/27048931","citation_count":48,"is_preprint":false},{"pmid":"29464284","id":"PMC_29464284","title":"Degradation of the mitochondrial complex I assembly factor TMEM126B under chronic hypoxia.","date":"2018","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/29464284","citation_count":35,"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":"30781698","id":"PMC_30781698","title":"Chronic Hypoxia Enhances β-Oxidation-Dependent Electron Transport via Electron Transferring Flavoproteins.","date":"2019","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/30781698","citation_count":19,"is_preprint":false},{"pmid":"38052461","id":"PMC_38052461","title":"Proteomic-based stratification of intermediate-risk prostate cancer patients.","date":"2023","source":"Life science alliance","url":"https://pubmed.ncbi.nlm.nih.gov/38052461","citation_count":17,"is_preprint":false},{"pmid":"29093663","id":"PMC_29093663","title":"Selection and Characterization of Palmitic Acid Responsive Patients with an OXPHOS Complex I Defect.","date":"2017","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/29093663","citation_count":12,"is_preprint":false},{"pmid":"30580996","id":"PMC_30580996","title":"Transmembrane protein 126B protects against high fat diet (HFD)-induced renal injury by suppressing dyslipidemia via inhibition of ROS.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/30580996","citation_count":8,"is_preprint":false},{"pmid":"36482121","id":"PMC_36482121","title":"Novel biallelic mutations in TMEM126B cause splicing defects and lead to Leigh-like syndrome with severe complex I deficiency.","date":"2022","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36482121","citation_count":6,"is_preprint":false},{"pmid":"31178133","id":"PMC_31178133","title":"Ablation of TMEM126B protects against heart injury via improving mitochondrial function in high fat diet (HFD)-induced mice.","date":"2019","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/31178133","citation_count":4,"is_preprint":false},{"pmid":"33075301","id":"PMC_33075301","title":"Ablation of TMEM126B protects against oxygen-glucose deprivation/reoxygenation-induced injuries of PC12 cells via maintaining mitochondrial anti-apoptotic functions.","date":"2020","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/33075301","citation_count":4,"is_preprint":false},{"pmid":"41154849","id":"PMC_41154849","title":"Genome-Wide Association Study Revealed Candidate Genes Associated with Litter Size, Weight, and Body Size Traits in Tianmu Polytocous Sheep (Ovis aries).","date":"2025","source":"Biology","url":"https://pubmed.ncbi.nlm.nih.gov/41154849","citation_count":1,"is_preprint":false},{"pmid":"41686563","id":"PMC_41686563","title":"Decoding lactylation in neuropathic pain: Immune cell infiltration patterns and machine learning-identified candidate biomarkers.","date":"2026","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41686563","citation_count":0,"is_preprint":false},{"pmid":"41278337","id":"PMC_41278337","title":"Diagnostic Yield of Whole-Genome Sequencing in Patients With Kidney Failure of Undetermined Etiology at Age 50 Years or Younger.","date":"2025","source":"Kidney international reports","url":"https://pubmed.ncbi.nlm.nih.gov/41278337","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11466,"output_tokens":1925,"usd":0.031636,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8953,"output_tokens":2766,"usd":0.056958,"stage2_stop_reason":"end_turn"},"total_usd":0.088594,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"TMEM126B is associated with subcomplexes of mitochondrial complex I (550 kDa and 815 kDa) that accumulate when NDUFA11 expression is suppressed, suggesting TMEM126B participates in constructing the membrane arm of complex I.\",\n      \"method\": \"Suppression of NDUFA11 expression, subcomplex isolation, mass spectrometry identification of associated proteins\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based co-fractionation with subcomplexes, single lab, but subcomplex identity and protein association established by two orthogonal approaches\",\n      \"pmids\": [\"24191001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TMEM126B is a component of the mitochondrial complex I assembly complex (alongside ACAD9, ECSIT, NDUFAF1, and TIMMDC1), and biallelic loss-of-function variants in TMEM126B cause severe complex I deficiency; viral rescue of TMEM126B in patient cell lines restores complex I assembly as shown by complexome profiling.\",\n      \"method\": \"Complexome profiling, viral rescue experiments, patient cell line functional analysis, whole-exome sequencing\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal complexome profiling plus viral rescue rescue in patient cells, replicated across multiple families and labs\",\n      \"pmids\": [\"27374774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM126B is a core component of the mitochondrial complex I intermediate assembly (MCIA) complex required for building the ND2-module of complex I; within the MCIA complex a hierarchy of stability exists centered on ACAD9, and loss of TMEM126B destabilizes the entire MCIA complex and blocks ND2-module assembly.\",\n      \"method\": \"CRISPR/Cas9 knockout of each MCIA component, quantitative proteomics, complexome profiling, co-immunoprecipitation\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO, quantitative proteomics, complexome profiling, Co-IP) in single rigorous study\",\n      \"pmids\": [\"32320651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TMEM126B knockdown in THP-1 macrophages reduces complex I assembly and attenuates mitochondrial ROS production upon LPS stimulation; reduced mtROS in TMEM126B-knockdown cells leads to decreased oxidation of SDHA, preserving SDH activity and thereby reducing HIF-1α stabilization and IL-1β expression.\",\n      \"method\": \"shRNA knockdown, BIAM switch assay coupled to LC-MS for protein oxidation, SDH activity assay, HIF-1α and IL-1β measurement, pharmacological SDH inhibition rescue\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA KD with multiple downstream readouts and pharmacological rescue in single lab\",\n      \"pmids\": [\"30368040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Under chronic hypoxia, HIF-1α induces the E3-ubiquitin ligase β-TrCP1, which facilitates proteolytic degradation of TMEM126B, leading to reduced MCIA complex abundance and impaired complex I assembly.\",\n      \"method\": \"Complexome profiling of isolated mitochondria under hypoxia, HIF-1α inhibition/activation experiments, β-TrCP1 modulation, protein stability assays\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — complexome profiling plus genetic/pharmacological perturbation of HIF-1α and β-TrCP1, single lab\",\n      \"pmids\": [\"29464284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TMEM126B and its paralogue TMEM126A have distinct functions in complex I assembly: TMEM126B acts in assembly of the ND2-module, whereas TMEM126A acts in assembly of the ND4 distal membrane module.\",\n      \"method\": \"Genome editing (knockout), pulse-labeling interaction studies with newly synthesized mtDNA-encoded subunits, quantitative proteomics, co-immunoprecipitation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal KO, pulse-labeling, and quantitative proteomics providing functional distinction between paralogs\",\n      \"pmids\": [\"33879611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The TMEM126B p.G212V missense mutation causes incomplete assembly of the peripheral arm of complex I, reducing mature complex I levels; complementation of patient fibroblasts with wild-type TMEM126B rescues complex I assembly, confirming the assembly factor role.\",\n      \"method\": \"Whole-exome sequencing, complementation study in patient fibroblasts, OXPHOS capacity measurement, BN-PAGE complex I assessment\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — complementation in patient fibroblasts with functional readout, single lab\",\n      \"pmids\": [\"29093663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Novel intronic (c.82-2 A>G) and exonic insertion (c.290dupT) TMEM126B mutations cause exon skipping (complete exon 2 skipping and partial/complete exon 3 skipping, respectively), leading to frameshifts, premature termination, loss of TMEM126B protein, and severe complex I assembly defect in patient lymphocytes.\",\n      \"method\": \"Minigene splicing assay, patient RNA analysis, functional analysis of complex I content and assembly in patient-derived lymphocytes\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — minigene splicing assays combined with patient RNA and functional complex I analysis, single lab\",\n      \"pmids\": [\"36482121\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TMEM126B is an integral component of the mitochondrial complex I intermediate assembly (MCIA) complex (with ACAD9, ECSIT, NDUFAF1, and TIMMDC1) that is specifically required for biogenesis of the ND2-module of the membrane arm of complex I; it is subject to HIF-1α–induced proteasomal degradation via β-TrCP1 under chronic hypoxia, and its loss reduces mitochondrial ROS signaling with downstream effects on SDHA oxidation, HIF-1α stabilization, and IL-1β expression in macrophages.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TMEM126B is a core subunit of the mitochondrial complex I intermediate assembly (MCIA) complex—together with ACAD9, ECSIT, NDUFAF1, and TIMMDC1—that drives biogenesis of the membrane arm of respiratory complex I [#1, #2]. Within the MCIA complex, which is organized around a stability hierarchy centered on ACAD9, loss of TMEM126B destabilizes the entire assembly module and specifically blocks construction of the ND2-module, a role distinct from its paralogue TMEM126A, which instead supports assembly of the ND4 distal membrane module [#2, #5]. Consistent with this assembly-factor function, biallelic loss-of-function, missense, and splice-disrupting variants in TMEM126B cause severe complex I deficiency, and re-expression of wild-type TMEM126B in patient cells restores complex I assembly [#1, #6, #7]. Beyond its constitutive assembly role, TMEM126B is a regulatory node coupling complex I biogenesis to redox and hypoxic signaling: its loss attenuates LPS-induced mitochondrial ROS production, reducing SDHA oxidation and thereby limiting HIF-1\\u03b1 stabilization and IL-1\\u03b2 expression in macrophages [#3], while under chronic hypoxia HIF-1\\u03b1\\u2013induced \\u03b2-TrCP1 targets TMEM126B for proteolytic degradation, lowering MCIA abundance and complex I assembly [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established that TMEM126B physically associates with complex I biogenesis, situating an uncharacterized membrane protein within respiratory chain assembly.\",\n      \"evidence\": \"NDUFA11 suppression with subcomplex isolation and mass spectrometry identifying TMEM126B in 550/815 kDa membrane-arm subcomplexes\",\n      \"pmids\": [\"24191001\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define which assembly step or module TMEM126B serves\", \"Association inferred from subcomplex accumulation rather than direct functional assay\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined TMEM126B as a bona fide MCIA complex component and established disease causation, answering whether its loss is pathogenic.\",\n      \"evidence\": \"Complexome profiling plus viral rescue in patient cell lines and whole-exome sequencing across families\",\n      \"pmids\": [\"27374774\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the specific module within complex I that requires TMEM126B\", \"Stoichiometry and architecture within MCIA not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Confirmed the assembly-factor role through a specific missense allele, linking peripheral arm assembly defects to reduced mature complex I.\",\n      \"evidence\": \"Whole-exome sequencing and complementation of patient fibroblasts with OXPHOS and BN-PAGE readouts for the p.G212V mutation\",\n      \"pmids\": [\"29093663\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-family/single-lab functional validation\", \"Mechanism by which the missense change disrupts assembly not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected TMEM126B-dependent complex I assembly to inflammatory redox signaling, showing it is not merely a housekeeping assembly factor.\",\n      \"evidence\": \"shRNA knockdown in THP-1 macrophages with BIAM-switch LC-MS oxidation profiling, SDH activity, HIF-1\\u03b1/IL-1\\u03b2 measurement, and pharmacological SDH inhibition rescue\",\n      \"pmids\": [\"30368040\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Knockdown rather than clean knockout\", \"Causal chain from mtROS to SDHA oxidation inferred via pharmacology in a single lab\", \"In vivo relevance not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed that TMEM126B abundance is dynamically regulated, identifying HIF-1\\u03b1/\\u03b2-TrCP1\\u2013mediated degradation as a hypoxic control point on complex I assembly.\",\n      \"evidence\": \"Complexome profiling of mitochondria under hypoxia with HIF-1\\u03b1 and \\u03b2-TrCP1 modulation and protein stability assays\",\n      \"pmids\": [\"29464284\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination site/E3 engagement not mapped\", \"Single-lab evidence for the degradation axis\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved the module specificity and intra-complex hierarchy, showing TMEM126B is required to build the ND2-module and that its loss collapses the whole MCIA complex.\",\n      \"evidence\": \"CRISPR/Cas9 knockout of each MCIA component with quantitative proteomics, complexome profiling, and co-immunoprecipitation\",\n      \"pmids\": [\"32320651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic/structural basis of ND2-module handover not defined\", \"Order of subunit recruitment within ND2 assembly not fully resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Distinguished TMEM126B from its paralogue TMEM126A, assigning each to a separate membrane module and clarifying non-redundant functions.\",\n      \"evidence\": \"Knockout, pulse-labeling of newly synthesized mtDNA-encoded subunits, quantitative proteomics, and co-immunoprecipitation\",\n      \"pmids\": [\"33879611\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the two paralogues partition substrate modules mechanistically is unresolved\", \"Whether they ever cooperate at module interfaces unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the mutational spectrum to splice-disrupting alleles, showing loss of protein via exon skipping recapitulates the severe complex I defect.\",\n      \"evidence\": \"Minigene splicing assays, patient RNA analysis, and functional complex I assessment in patient lymphocytes for intronic and insertion variants\",\n      \"pmids\": [\"36482121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genotype\\u2013phenotype correlation across allele types not systematized\", \"Single-lab functional validation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TMEM126B mechanistically templates ND2-module assembly and how its degradation is structurally triggered remain unresolved.\",\n      \"evidence\": \"No structural model of TMEM126B within MCIA or of its ND2-module handover is present in the corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of TMEM126B in the MCIA complex\", \"Ubiquitination determinants for \\u03b2-TrCP1 not mapped\", \"In vivo significance of the redox/hypoxia regulatory axis untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 2, 5]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\"MCIA complex (mitochondrial complex I intermediate assembly complex)\"],\n    \"partners\": [\"ACAD9\", \"ECSIT\", \"NDUFAF1\", \"TIMMDC1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}