{"gene":"TTC19","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2011,"finding":"TTC19 is embedded in the inner mitochondrial membrane as part of two high-molecular-weight complexes, one of which coincides with complex III (cIII), and physically interacts with cIII as demonstrated by coimmunoprecipitation. Loss of TTC19 causes accumulation of cIII-specific assembly intermediates, establishing TTC19 as a cIII assembly factor.","method":"Coimmunoprecipitation, Blue-Native gel electrophoresis, subcellular fractionation, Drosophila knockout model with locomotor/biochemical readouts","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, organellar fractionation, and orthogonal Drosophila KO model with defined biochemical phenotype; replicated in subsequent studies","pmids":["21278747"],"is_preprint":false},{"year":2017,"finding":"TTC19 binds to the fully assembled complex III dimer only after incorporation of the iron-sulfur Rieske protein (UQCRFS1). During in situ maturation of UQCRFS1, N-terminal polypeptide fragments are produced and remain bound to the holocomplex; TTC19 is required for their rapid removal. In the absence of TTC19 these fragments accumulate within complex III, causing structural and functional impairment of the enzyme.","method":"Ttc19−/− mouse model biochemical characterization, BN-PAGE, mass spectrometry of UQCRFS1 fragments, human cell line knockdown/rescue experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mouse KO model, human cell lines, mass spectrometry, BN-PAGE) in a single rigorous study with mechanistic follow-up","pmids":["28673544"],"is_preprint":false},{"year":2011,"finding":"Drosophila melanogaster knockout of TTC19 results in low fertility, adult-onset locomotor impairment, and bang sensitivity, associated with cIII deficiency, establishing a causal in vivo link between TTC19 loss and mitochondrial complex III dysfunction.","method":"Drosophila knockout model; locomotor assays; biochemical cIII activity measurement","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined locomotor and biochemical phenotypic readouts, replicated in subsequent mammalian models","pmids":["21278747"],"is_preprint":false},{"year":2013,"finding":"Loss-of-function mutation in TTC19 results in near-complete absence of TTC19 protein, defective assembly of complex III in muscle, and enhanced production of reactive oxygen species in cultured skin fibroblasts, linking TTC19 to ROS regulation downstream of cIII assembly.","method":"Western blot (protein absence), biochemical cIII assembly assay (muscle), ROS measurement in fibroblasts","journal":"Neurogenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Western blot, BN-PAGE, ROS assay) in patient-derived cells, single lab","pmids":["23532514"],"is_preprint":false},{"year":2014,"finding":"A novel homozygous frameshift rearrangement in TTC19 (c.213_229dup) causes absence of TTC19 protein and accumulation of cIII-specific assembly intermediates detectable by Blue-Native Gel Electrophoresis, confirming that TTC19 is required for normal cIII assembly/stability.","method":"Western blot, Blue-Native Gel Electrophoresis in patient fibroblasts","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (protein blot, BN-PAGE) in patient-derived cells, single lab","pmids":["25452764"],"is_preprint":false},{"year":2017,"finding":"TTC19-deficient mice show progressive neurological and metabolic decline, decreased complex III activity, and increased production of reactive oxygen species, confirming the mammalian in vivo role of TTC19 in complex III function and ROS homeostasis.","method":"Ttc19−/− mouse model; spectrophotometric cIII activity assay; ROS measurement","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse with defined biochemical phenotypic readouts (enzyme activity, ROS), replicated across mouse and human cell systems in the same study","pmids":["28673544"],"is_preprint":false},{"year":2023,"finding":"XPOT (Exportin-T) preferentially transports tRNA-Ala-AGC-10-1 to the cytoplasm, driving translation of TTC19; knockdown of TTC19 is indispensable for cytokinesis completion and proliferation of triple-negative breast cancer (TNBC) cells, revealing a non-mitochondrial role for TTC19 in cell division.","method":"XPOT knockdown, RNA-seq, high-throughput tRNA sequencing, codon preferential analysis, protein mass spectrometry, TTC19 knockdown with cytokinesis/proliferation readouts in TNBC cell lines","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RNA-seq, tRNA-seq, mass spectrometry, functional KD) in a single lab study; novel finding not yet independently replicated","pmids":["37928256"],"is_preprint":false},{"year":2026,"finding":"A novel intronic 31 bp deletion in TTC19 disrupts splicing, producing aberrant transcripts, reduced TTC19 gene expression, and mitochondrial dysfunction in patient-derived fibroblasts, functionally confirming the pathogenicity of a splice-site variant.","method":"Splicing assay, RT-PCR for aberrant transcript, gene expression analysis, mitochondrial function assay in patient fibroblasts","journal":"Mitochondrion","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional splicing assay with multiple readouts (aberrant transcript, expression, mitochondrial function) in patient cells, single lab","pmids":["42250897"],"is_preprint":false}],"current_model":"TTC19 is a mitochondrial inner membrane protein that associates with the fully assembled complex III (cIII) dimer after UQCRFS1 (Rieske iron-sulfur protein) incorporation, where it acts as a 'husbandry factor' that removes N-terminal UQCRFS1 maturation fragments from the holocomplex; without TTC19 these fragments accumulate, impairing cIII structure and function, reducing electron transfer, and elevating reactive oxygen species production. Separately, TTC19 translation is driven by XPOT-dependent nuclear export of a specific tRNA isodecoder, and TTC19 is required for cytokinesis in cancer cells, suggesting an additional non-mitochondrial function in cell division."},"narrative":{"mechanistic_narrative":"TTC19 is a mitochondrial inner-membrane protein that functions in the late maturation of respiratory chain complex III (cIII) [PMID:21278747]. It assembles into high-molecular-weight complexes that coincide with cIII and physically associates with the holocomplex, and its loss causes accumulation of cIII-specific assembly intermediates [PMID:21278747]. Mechanistically, TTC19 binds the fully assembled cIII dimer only after incorporation of the Rieske iron-sulfur protein UQCRFS1, and is required for the rapid removal of N-terminal UQCRFS1 maturation fragments that otherwise remain bound to and impair the holocomplex [PMID:28673544]. Loss of TTC19 across Drosophila, mouse, and patient-derived systems produces cIII deficiency with reduced enzyme activity and elevated reactive oxygen species [PMID:28673544, PMID:23532514], and causative loss-of-function and splice-disrupting mutations link TTC19 to mitochondrial dysfunction in patients [PMID:25452764, PMID:42250897]. A distinct non-mitochondrial role has been described in which XPOT-dependent tRNA export drives TTC19 translation and TTC19 is required for cytokinesis and proliferation of triple-negative breast cancer cells [PMID:37928256].","teleology":[{"year":2011,"claim":"Established that TTC19 is a mitochondrial inner-membrane protein required for complex III biogenesis, answering whether it had any role in the respiratory chain.","evidence":"Co-IP, BN-PAGE, subcellular fractionation, and a Drosophila knockout with locomotor and biochemical readouts","pmids":["21278747"],"confidence":"High","gaps":["Did not define the specific assembly step TTC19 acts on","Did not identify the molecular substrate or binding determinants"]},{"year":2013,"claim":"Connected human TTC19 loss to defective cIII assembly in muscle and elevated ROS in patient cells, extending the assembly role to a redox consequence.","evidence":"Western blot, biochemical cIII assembly assay, and ROS measurement in patient-derived muscle and fibroblasts","pmids":["23532514"],"confidence":"Medium","gaps":["Single-lab patient study","Mechanism linking assembly defect to ROS not resolved"]},{"year":2014,"claim":"Confirmed via an independent causative frameshift that TTC19 absence leads to accumulation of cIII assembly intermediates, reinforcing its assembly/stability function.","evidence":"Western blot and BN-PAGE in patient fibroblasts carrying a homozygous frameshift","pmids":["25452764"],"confidence":"Medium","gaps":["Single-lab patient study","Did not address the biochemical identity of the accumulating intermediate"]},{"year":2017,"claim":"Defined the precise molecular function: TTC19 acts after UQCRFS1 incorporation to clear N-terminal Rieske maturation fragments from assembled cIII, explaining how its loss destabilizes the enzyme.","evidence":"Ttc19-/- mouse model, human cell knockdown/rescue, BN-PAGE, and mass spectrometry of UQCRFS1 fragments; mouse showed reduced cIII activity and increased ROS in vivo","pmids":["28673544"],"confidence":"High","gaps":["Did not establish a structural model of the TTC19–cIII interaction","Mechanism of fragment removal/degradation not detailed"]},{"year":2023,"claim":"Revealed a non-mitochondrial role by linking XPOT-dependent tRNA export to TTC19 translation and showing TTC19 is required for cytokinesis and proliferation in cancer cells.","evidence":"XPOT knockdown, RNA-seq, tRNA-seq, codon analysis, mass spectrometry, and TTC19 knockdown with cytokinesis/proliferation readouts in TNBC lines","pmids":["37928256"],"confidence":"Medium","gaps":["Not independently replicated","Molecular basis of the cytokinesis role undefined","Relationship to the mitochondrial function unclear"]},{"year":2026,"claim":"Functionally validated a splice-disrupting intronic variant as pathogenic, showing aberrant transcripts and mitochondrial dysfunction.","evidence":"Splicing assay, RT-PCR, expression analysis, and mitochondrial function assay in patient fibroblasts","pmids":["42250897"],"confidence":"Medium","gaps":["Single-lab patient study","Did not assess cIII-specific assembly intermediates directly"]},{"year":null,"claim":"How the mitochondrial cIII maturation role and the reported XPOT-linked cytokinesis function are mechanistically related, if at all, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of TTC19 bound to cIII","Mechanism of UQCRFS1 fragment removal not defined","Non-mitochondrial cytokinesis role not independently confirmed"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,5]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,1]}],"complexes":["respiratory chain complex III"],"partners":["UQCRFS1","XPOT"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q6DKK2","full_name":"Tetratricopeptide repeat protein 19, mitochondrial","aliases":[],"length_aa":380,"mass_kda":42.5,"function":"Required for the preservation of the structural and functional integrity of mitochondrial respiratory complex III by allowing the physiological turnover of the Rieske protein UQCRFS1 (PubMed:21278747, PubMed:28673544). Involved in the clearance of UQCRFS1 N-terminal fragments, which are produced upon incorporation of UQCRFS1 into the complex III and whose presence is detrimental for its catalytic activity (PubMed:28673544)","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/Q6DKK2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TTC19","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TTC19","total_profiled":1310},"omim":[{"mim_id":"615157","title":"MITOCHONDRIAL COMPLEX III DEFICIENCY, NUCLEAR TYPE 2; MC3DN2","url":"https://www.omim.org/entry/615157"},{"mim_id":"613814","title":"TETRATRICOPEPTIDE REPEAT DOMAIN-CONTAINING PROTEIN 19; TTC19","url":"https://www.omim.org/entry/613814"},{"mim_id":"607858","title":"PRESENILIN-ASSOCIATED RHOMBOID-LIKE PROTEIN; PARL","url":"https://www.omim.org/entry/607858"},{"mim_id":"124000","title":"MITOCHONDRIAL COMPLEX III DEFICIENCY, NUCLEAR TYPE 1; MC3DN1","url":"https://www.omim.org/entry/124000"}],"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/TTC19"},"hgnc":{"alias_symbol":["FLJ20343","MGC19520"],"prev_symbol":[]},"alphafold":{"accession":"Q6DKK2","domains":[{"cath_id":"1.25.40.10","chopping":"272-371","consensus_level":"medium","plddt":96.4362,"start":272,"end":371}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6DKK2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6DKK2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6DKK2-F1-predicted_aligned_error_v6.png","plddt_mean":79.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TTC19","jax_strain_url":"https://www.jax.org/strain/search?query=TTC19"},"sequence":{"accession":"Q6DKK2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6DKK2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6DKK2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6DKK2"}},"corpus_meta":[{"pmid":"21278747","id":"PMC_21278747","title":"Mutations in TTC19 cause mitochondrial complex III deficiency and neurological impairment in humans and flies.","date":"2011","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21278747","citation_count":133,"is_preprint":false},{"pmid":"28673544","id":"PMC_28673544","title":"TTC19 Plays a Husbandry Role on UQCRFS1 Turnover in the Biogenesis of Mitochondrial Respiratory Complex III.","date":"2017","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/28673544","citation_count":69,"is_preprint":false},{"pmid":"23532514","id":"PMC_23532514","title":"Novel TTC19 mutation in a family with severe psychiatric manifestations and complex III deficiency.","date":"2013","source":"Neurogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/23532514","citation_count":42,"is_preprint":false},{"pmid":"24397319","id":"PMC_24397319","title":"Exome sequencing reveals a novel TTC19 mutation in an autosomal recessive spinocerebellar ataxia patient.","date":"2014","source":"BMC neurology","url":"https://pubmed.ncbi.nlm.nih.gov/24397319","citation_count":31,"is_preprint":false},{"pmid":"25899669","id":"PMC_25899669","title":"Phenotypic variation of TTC19-deficient mitochondrial complex III deficiency: a case report and literature review.","date":"2015","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/25899669","citation_count":29,"is_preprint":false},{"pmid":"24368687","id":"PMC_24368687","title":"Mutations in the Complex III Assembly Factor Tetratricopeptide 19 Gene TTC19 Are a Rare Cause of Leigh Syndrome.","date":"2013","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/24368687","citation_count":29,"is_preprint":false},{"pmid":"25887401","id":"PMC_25887401","title":"Mutations in TTC19: expanding the molecular, clinical and biochemical phenotype.","date":"2015","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/25887401","citation_count":26,"is_preprint":false},{"pmid":"31551910","id":"PMC_31551910","title":"A Novel TTC19 Mutation in a Patient With Neurological, Psychological, and Gastrointestinal Impairment.","date":"2019","source":"Frontiers in neurology","url":"https://pubmed.ncbi.nlm.nih.gov/31551910","citation_count":19,"is_preprint":false},{"pmid":"25452764","id":"PMC_25452764","title":"A novel mutation in TTC19 associated with isolated complex III deficiency, cerebellar hypoplasia, and bilateral basal ganglia lesions.","date":"2014","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25452764","citation_count":18,"is_preprint":false},{"pmid":"25652355","id":"PMC_25652355","title":"A Japanese case of cerebellar ataxia, spastic paraparesis and deep sensory impairment associated with a novel homozygous TTC19 mutation.","date":"2015","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25652355","citation_count":17,"is_preprint":false},{"pmid":"25772319","id":"PMC_25772319","title":"Mitochondrial Complex III Deficiency Caused by TTC19 Defects: Report of a Novel Mutation and Review of Literature.","date":"2015","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/25772319","citation_count":16,"is_preprint":false},{"pmid":"29961508","id":"PMC_29961508","title":"Novel Homozygous Variant in TTC19 Causing Mitochondrial Complex III Deficiency with Recurrent Stroke-Like Episodes: Expanding the Phenotype.","date":"2018","source":"Seminars in pediatric neurology","url":"https://pubmed.ncbi.nlm.nih.gov/29961508","citation_count":15,"is_preprint":false},{"pmid":"37928256","id":"PMC_37928256","title":"XPOT Disruption Suppresses TNBC Growth through Inhibition of Specific tRNA Nuclear Exportation and TTC19 Expression to Induce Cytokinesis Failure.","date":"2023","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37928256","citation_count":7,"is_preprint":false},{"pmid":"37927170","id":"PMC_37927170","title":"A TTC19 mutation associated with progressive movement disorders and peripheral neuropathy: Case report and systematic review.","date":"2023","source":"CNS neuroscience & therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/37927170","citation_count":6,"is_preprint":false},{"pmid":"41818954","id":"PMC_41818954","title":"TTC19-related mitochondrial complex III deficiency: Clinical and genetic characterization of 10 patients from 5 unrelated Arab families.","date":"2026","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/41818954","citation_count":1,"is_preprint":false},{"pmid":"40946707","id":"PMC_40946707","title":"Motor Neuropathy in a Patient With Mitochondrial Disease and a Novel TTC19 Variant: An Underrecognized Phenotypic Feature.","date":"2025","source":"Journal of the peripheral nervous system : JPNS","url":"https://pubmed.ncbi.nlm.nih.gov/40946707","citation_count":1,"is_preprint":false},{"pmid":"40652486","id":"PMC_40652486","title":"Expanding the Clinical, Pathological, and Molecular Phenotypes of Tetratricopeptide 19 (TTC19) Gene Mutations: A Case Report from India.","date":"2025","source":"Neurology India","url":"https://pubmed.ncbi.nlm.nih.gov/40652486","citation_count":0,"is_preprint":false},{"pmid":"42250897","id":"PMC_42250897","title":"TTC19 and FMNL2 gene variants in a pediatric case of mitochondrial disorder with renal tubular acidosis.","date":"2026","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/42250897","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10299,"output_tokens":1996,"usd":0.030419,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9016,"output_tokens":2130,"usd":0.049165,"stage2_stop_reason":"end_turn"},"total_usd":0.079584,"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\": 2011,\n      \"finding\": \"TTC19 is embedded in the inner mitochondrial membrane as part of two high-molecular-weight complexes, one of which coincides with complex III (cIII), and physically interacts with cIII as demonstrated by coimmunoprecipitation. Loss of TTC19 causes accumulation of cIII-specific assembly intermediates, establishing TTC19 as a cIII assembly factor.\",\n      \"method\": \"Coimmunoprecipitation, Blue-Native gel electrophoresis, subcellular fractionation, Drosophila knockout model with locomotor/biochemical readouts\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, organellar fractionation, and orthogonal Drosophila KO model with defined biochemical phenotype; replicated in subsequent studies\",\n      \"pmids\": [\"21278747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TTC19 binds to the fully assembled complex III dimer only after incorporation of the iron-sulfur Rieske protein (UQCRFS1). During in situ maturation of UQCRFS1, N-terminal polypeptide fragments are produced and remain bound to the holocomplex; TTC19 is required for their rapid removal. In the absence of TTC19 these fragments accumulate within complex III, causing structural and functional impairment of the enzyme.\",\n      \"method\": \"Ttc19−/− mouse model biochemical characterization, BN-PAGE, mass spectrometry of UQCRFS1 fragments, human cell line knockdown/rescue experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mouse KO model, human cell lines, mass spectrometry, BN-PAGE) in a single rigorous study with mechanistic follow-up\",\n      \"pmids\": [\"28673544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Drosophila melanogaster knockout of TTC19 results in low fertility, adult-onset locomotor impairment, and bang sensitivity, associated with cIII deficiency, establishing a causal in vivo link between TTC19 loss and mitochondrial complex III dysfunction.\",\n      \"method\": \"Drosophila knockout model; locomotor assays; biochemical cIII activity measurement\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined locomotor and biochemical phenotypic readouts, replicated in subsequent mammalian models\",\n      \"pmids\": [\"21278747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Loss-of-function mutation in TTC19 results in near-complete absence of TTC19 protein, defective assembly of complex III in muscle, and enhanced production of reactive oxygen species in cultured skin fibroblasts, linking TTC19 to ROS regulation downstream of cIII assembly.\",\n      \"method\": \"Western blot (protein absence), biochemical cIII assembly assay (muscle), ROS measurement in fibroblasts\",\n      \"journal\": \"Neurogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Western blot, BN-PAGE, ROS assay) in patient-derived cells, single lab\",\n      \"pmids\": [\"23532514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A novel homozygous frameshift rearrangement in TTC19 (c.213_229dup) causes absence of TTC19 protein and accumulation of cIII-specific assembly intermediates detectable by Blue-Native Gel Electrophoresis, confirming that TTC19 is required for normal cIII assembly/stability.\",\n      \"method\": \"Western blot, Blue-Native Gel Electrophoresis in patient fibroblasts\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (protein blot, BN-PAGE) in patient-derived cells, single lab\",\n      \"pmids\": [\"25452764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TTC19-deficient mice show progressive neurological and metabolic decline, decreased complex III activity, and increased production of reactive oxygen species, confirming the mammalian in vivo role of TTC19 in complex III function and ROS homeostasis.\",\n      \"method\": \"Ttc19−/− mouse model; spectrophotometric cIII activity assay; ROS measurement\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse with defined biochemical phenotypic readouts (enzyme activity, ROS), replicated across mouse and human cell systems in the same study\",\n      \"pmids\": [\"28673544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"XPOT (Exportin-T) preferentially transports tRNA-Ala-AGC-10-1 to the cytoplasm, driving translation of TTC19; knockdown of TTC19 is indispensable for cytokinesis completion and proliferation of triple-negative breast cancer (TNBC) cells, revealing a non-mitochondrial role for TTC19 in cell division.\",\n      \"method\": \"XPOT knockdown, RNA-seq, high-throughput tRNA sequencing, codon preferential analysis, protein mass spectrometry, TTC19 knockdown with cytokinesis/proliferation readouts in TNBC cell lines\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RNA-seq, tRNA-seq, mass spectrometry, functional KD) in a single lab study; novel finding not yet independently replicated\",\n      \"pmids\": [\"37928256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A novel intronic 31 bp deletion in TTC19 disrupts splicing, producing aberrant transcripts, reduced TTC19 gene expression, and mitochondrial dysfunction in patient-derived fibroblasts, functionally confirming the pathogenicity of a splice-site variant.\",\n      \"method\": \"Splicing assay, RT-PCR for aberrant transcript, gene expression analysis, mitochondrial function assay in patient fibroblasts\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional splicing assay with multiple readouts (aberrant transcript, expression, mitochondrial function) in patient cells, single lab\",\n      \"pmids\": [\"42250897\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TTC19 is a mitochondrial inner membrane protein that associates with the fully assembled complex III (cIII) dimer after UQCRFS1 (Rieske iron-sulfur protein) incorporation, where it acts as a 'husbandry factor' that removes N-terminal UQCRFS1 maturation fragments from the holocomplex; without TTC19 these fragments accumulate, impairing cIII structure and function, reducing electron transfer, and elevating reactive oxygen species production. Separately, TTC19 translation is driven by XPOT-dependent nuclear export of a specific tRNA isodecoder, and TTC19 is required for cytokinesis in cancer cells, suggesting an additional non-mitochondrial function in cell division.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TTC19 is a mitochondrial inner-membrane protein that functions in the late maturation of respiratory chain complex III (cIII) [#0]. It assembles into high-molecular-weight complexes that coincide with cIII and physically associates with the holocomplex, and its loss causes accumulation of cIII-specific assembly intermediates [#0]. Mechanistically, TTC19 binds the fully assembled cIII dimer only after incorporation of the Rieske iron-sulfur protein UQCRFS1, and is required for the rapid removal of N-terminal UQCRFS1 maturation fragments that otherwise remain bound to and impair the holocomplex [#1]. Loss of TTC19 across Drosophila, mouse, and patient-derived systems produces cIII deficiency with reduced enzyme activity and elevated reactive oxygen species [#1, #5, #3], and causative loss-of-function and splice-disrupting mutations link TTC19 to mitochondrial dysfunction in patients [#4, #7]. A distinct non-mitochondrial role has been described in which XPOT-dependent tRNA export drives TTC19 translation and TTC19 is required for cytokinesis and proliferation of triple-negative breast cancer cells [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established that TTC19 is a mitochondrial inner-membrane protein required for complex III biogenesis, answering whether it had any role in the respiratory chain.\",\n      \"evidence\": \"Co-IP, BN-PAGE, subcellular fractionation, and a Drosophila knockout with locomotor and biochemical readouts\",\n      \"pmids\": [\"21278747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the specific assembly step TTC19 acts on\", \"Did not identify the molecular substrate or binding determinants\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected human TTC19 loss to defective cIII assembly in muscle and elevated ROS in patient cells, extending the assembly role to a redox consequence.\",\n      \"evidence\": \"Western blot, biochemical cIII assembly assay, and ROS measurement in patient-derived muscle and fibroblasts\",\n      \"pmids\": [\"23532514\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab patient study\", \"Mechanism linking assembly defect to ROS not resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Confirmed via an independent causative frameshift that TTC19 absence leads to accumulation of cIII assembly intermediates, reinforcing its assembly/stability function.\",\n      \"evidence\": \"Western blot and BN-PAGE in patient fibroblasts carrying a homozygous frameshift\",\n      \"pmids\": [\"25452764\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab patient study\", \"Did not address the biochemical identity of the accumulating intermediate\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the precise molecular function: TTC19 acts after UQCRFS1 incorporation to clear N-terminal Rieske maturation fragments from assembled cIII, explaining how its loss destabilizes the enzyme.\",\n      \"evidence\": \"Ttc19-/- mouse model, human cell knockdown/rescue, BN-PAGE, and mass spectrometry of UQCRFS1 fragments; mouse showed reduced cIII activity and increased ROS in vivo\",\n      \"pmids\": [\"28673544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish a structural model of the TTC19–cIII interaction\", \"Mechanism of fragment removal/degradation not detailed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a non-mitochondrial role by linking XPOT-dependent tRNA export to TTC19 translation and showing TTC19 is required for cytokinesis and proliferation in cancer cells.\",\n      \"evidence\": \"XPOT knockdown, RNA-seq, tRNA-seq, codon analysis, mass spectrometry, and TTC19 knockdown with cytokinesis/proliferation readouts in TNBC lines\",\n      \"pmids\": [\"37928256\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Not independently replicated\", \"Molecular basis of the cytokinesis role undefined\", \"Relationship to the mitochondrial function unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Functionally validated a splice-disrupting intronic variant as pathogenic, showing aberrant transcripts and mitochondrial dysfunction.\",\n      \"evidence\": \"Splicing assay, RT-PCR, expression analysis, and mitochondrial function assay in patient fibroblasts\",\n      \"pmids\": [\"42250897\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab patient study\", \"Did not assess cIII-specific assembly intermediates directly\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the mitochondrial cIII maturation role and the reported XPOT-linked cytokinesis function are mechanistically related, if at all, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of TTC19 bound to cIII\", \"Mechanism of UQCRFS1 fragment removal not defined\", \"Non-mitochondrial cytokinesis role not independently confirmed\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\"respiratory chain complex III\"],\n    \"partners\": [\"UQCRFS1\", \"XPOT\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":4,"faith_total":5,"faith_pct":80.0}}