{"gene":"TRAPPC6B","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2024,"finding":"TRAPPC6B preferentially associates with the TRAPP II complex over TRAPP III, as shown by co-immunoprecipitation experiments where TRAPPC6B co-precipitated significantly more with TRAPP II, while its homologue TRAPPC6A co-precipitated equally with TRAPP II and TRAPP III.","method":"Co-immunoprecipitation from patient-derived fibroblasts and cell lines","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with comparison to paralogue TRAPPC6A, single lab, two orthogonal comparisons","pmids":["37713627"],"is_preprint":false},{"year":2024,"finding":"Loss-of-function mutation in TRAPPC6B (c.454C>T, p.Q152*) reduces the rate of trafficking into the Golgi apparatus and causes Golgi fragmentation in patient-derived fibroblasts, both of which were rescued by wild-type TRAPPC6B re-expression.","method":"Trafficking assay and Golgi morphology imaging in patient-derived fibroblasts with rescue experiment","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional rescue experiment with wild-type TRAPPC6B, direct Golgi trafficking and morphology readout, single lab with multiple orthogonal methods","pmids":["37713627"],"is_preprint":false},{"year":2024,"finding":"The TRAPPC6B p.Q152* mutant shows weakened interaction with TRAPP binding partner TRAPPC3, and patient-derived fibroblasts with this variant show reduced levels of TRAPPC6B as well as TRAPP II complex-specific members TRAPPC9 and TRAPPC10, while TRAPPC6A levels are elevated.","method":"Co-immunoprecipitation and Western blotting in patient-derived fibroblasts","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus protein level quantification, single lab, multiple TRAPP subunits assessed","pmids":["37713627"],"is_preprint":false},{"year":2024,"finding":"Neuronal knockdown of TRAPPC6B in Drosophila impairs locomotion and leads to wing posture defects, supporting a role for TRAPPC6B in neuromotor function.","method":"Drosophila TRAPPC6B-deficiency model with neuronal-specific RNAi knockdown and behavioral assays","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo loss-of-function with defined behavioral phenotype in a model organism, single lab","pmids":["37713627"],"is_preprint":false},{"year":2017,"finding":"TRAPPC6B encodes a core subunit of TRAPP I complex; a homozygous splice mutation causing exon-skipping and loss of TRAPPC6B function in patients leads to microcephaly and neuronal hyperexcitability, and zebrafish trappc6b morphants replicate the human phenotype with decreased head size and lower seizure threshold.","method":"Patient fibroblast splicing assay (minigene and endogenous transcript), zebrafish morpholino knockdown with phenotypic readout","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — zebrafish knockdown with defined phenotype and patient splicing validation, single lab","pmids":["28626029"],"is_preprint":false},{"year":2016,"finding":"A TRAPPC6B c.485G>A splice-site variant promotes exon 3-skipping and disrupts normal TRAPPC6B transcript processing, as demonstrated by minigene transfection assay and analysis of patient transcripts.","method":"Minigene transfection splicing assay and RT-PCR of patient transcripts","journal":"Parkinsonism & related disorders","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct splicing assay with minigene and patient material, single lab, single method","pmids":["27569842"],"is_preprint":false},{"year":2020,"finding":"RNAi-mediated silencing of TRAPPC6B in ACHN human renal epithelial cells confers protection against Shiga toxin 2a cytotoxicity, linking TRAPPC6B to intracellular Shiga toxin trafficking.","method":"RNAi knockdown with cell viability readout after Shiga toxin challenge","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single RNAi knockdown experiment with cytotoxicity readout, no mechanistic pathway placement, single lab","pmids":["32188865"],"is_preprint":false},{"year":2024,"finding":"Human TRAPPC6B can functionally replace its yeast counterpart (Trs33) in Saccharomyces cerevisiae, demonstrating functional conservation of the protein across species.","method":"CRISPR/Cas9-mediated humanized yeast complementation assay","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct genetic complementation in yeast with growth/function readout, single lab","pmids":["39273027"],"is_preprint":false}],"current_model":"TRAPPC6B is a core subunit of TRAPP complexes that is preferentially incorporated into the TRAPP II complex (via interaction with TRAPPC3), where it is required for normal Golgi trafficking and Golgi integrity; loss-of-function variants disrupt TRAPP II complex stability, impair membrane trafficking to the Golgi, cause Golgi fragmentation, and result in neurodevelopmental defects including microcephaly and epilepsy as demonstrated in patient fibroblasts, zebrafish, and Drosophila models."},"narrative":{"mechanistic_narrative":"TRAPPC6B is a core subunit of the multimeric TRAPP (transport protein particle) tethering complexes required for membrane trafficking to and integrity of the Golgi apparatus [PMID:37713627, PMID:28626029]. It is preferentially incorporated into the TRAPP II complex through interaction with TRAPPC3, distinguishing it from its paralogue TRAPPC6A, which partitions equally between TRAPP II and TRAPP III [PMID:37713627]. Loss-of-function variants destabilize the complex: the p.Q152* truncation weakens binding to TRAPPC3 and lowers cellular levels of TRAPPC6B together with the TRAPP II-specific subunits TRAPPC9 and TRAPPC10, with a compensatory rise in TRAPPC6A [PMID:37713627]. The functional consequence is slowed trafficking into the Golgi and Golgi fragmentation, both rescued by wild-type re-expression [PMID:37713627]. This trafficking function is evolutionarily conserved, as human TRAPPC6B complements deletion of its yeast orthologue Trs33 [PMID:39273027]. Disrupting TRAPPC6B causes a neurodevelopmental disorder featuring microcephaly, neuronal hyperexcitability, and epilepsy, established through patient variants and recapitulated by zebrafish morphants showing reduced head size and lowered seizure threshold and by neuronal Drosophila knockdown causing locomotor and wing-posture defects [PMID:37713627, PMID:28626029].","teleology":[{"year":2016,"claim":"Established that specific TRAPPC6B sequence variants disrupt normal transcript processing, providing the first molecular handle on how the gene is inactivated in disease.","evidence":"Minigene transfection splicing assay and RT-PCR of patient transcripts","pmids":["27569842"],"confidence":"Medium","gaps":["Did not assess the consequence for TRAPP complex assembly or trafficking","No in vivo phenotype linked to the splicing defect"]},{"year":2017,"claim":"Connected TRAPPC6B loss-of-function to a defined neurodevelopmental phenotype, demonstrating the gene is required for normal brain development and neuronal excitability.","evidence":"Patient fibroblast splicing assay plus zebrafish morpholino knockdown with microcephaly and seizure-threshold readouts","pmids":["28626029"],"confidence":"Medium","gaps":["Morpholino knockdown susceptible to off-target effects, no rescue reported","Subcellular trafficking mechanism not addressed","Assigned to TRAPP I rather than resolving complex specificity"]},{"year":2020,"claim":"Implicated TRAPPC6B in an intracellular toxin trafficking route, hinting at the breadth of cargo whose transport depends on the protein.","evidence":"RNAi knockdown in ACHN renal epithelial cells with Shiga toxin 2a cytotoxicity readout","pmids":["32188865"],"confidence":"Low","gaps":["Single RNAi knockdown without rescue or reciprocal validation","No mechanistic placement within the trafficking pathway","Relevance to neuronal phenotype unestablished"]},{"year":2024,"claim":"Resolved which TRAPP subcomplex TRAPPC6B belongs to and showed how a truncating variant destabilizes it, explaining the trafficking defect mechanistically.","evidence":"Co-IP comparing TRAPP II vs III association and against paralogue TRAPPC6A, Western blot quantification, Golgi trafficking/morphology assays with wild-type rescue in patient fibroblasts, plus Drosophila neuronal RNAi behavioral assays","pmids":["37713627"],"confidence":"High","gaps":["No structural model of how TRAPPC6B is incorporated into TRAPP II","Mechanism by which TRAPP II loss produces neuronal hyperexcitability not defined","Identity of GTPase substrate/effectors at the Golgi not addressed"]},{"year":2024,"claim":"Demonstrated functional conservation of TRAPPC6B from yeast to human, confirming the core trafficking role is preserved across species.","evidence":"CRISPR/Cas9 humanized yeast complementation of Trs33 deletion with growth readout","pmids":["39273027"],"confidence":"Medium","gaps":["Complementation does not map the human-specific TRAPP II interactions","Does not address neuronal function directly"]},{"year":null,"claim":"How TRAPP II-dependent Golgi trafficking failure translates into microcephaly and neuronal hyperexcitability at the cellular level remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No identified molecular link between Golgi fragmentation and neuronal excitability","No structural basis for TRAPPC6B incorporation into TRAPP II","Cargo spectrum requiring TRAPPC6B in neurons undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,2,4]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,4]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[1]}],"complexes":["TRAPP II","TRAPP complex"],"partners":["TRAPPC3","TRAPPC9","TRAPPC10"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q86SZ2","full_name":"Trafficking protein particle complex subunit 6B","aliases":[],"length_aa":158,"mass_kda":18.0,"function":"Component of a transport protein particle (TRAPP) complex that may function in specific stages of inter-organelle traffic (PubMed:16025134, PubMed:16828797). Specifically involved in the early development of neural circuitry, likely by controlling the frequency and amplitude of intracellular calcium transients implicated in the regulation of neuron differentiation and survival (Probable)","subcellular_location":"Golgi apparatus, cis-Golgi network; Endoplasmic reticulum","url":"https://www.uniprot.org/uniprotkb/Q86SZ2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TRAPPC6B","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"TRAPPC11","stoichiometry":10.0},{"gene":"TRAPPC2","stoichiometry":10.0},{"gene":"TRAPPC1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/TRAPPC6B","total_profiled":1310},"omim":[{"mim_id":"617862","title":"NEURODEVELOPMENTAL DISORDER WITH MICROCEPHALY, EPILEPSY, AND BRAIN ATROPHY; NEDMEBA","url":"https://www.omim.org/entry/617862"},{"mim_id":"610397","title":"TRAFFICKING PROTEIN PARTICLE COMPLEX, SUBUNIT 6B; TRAPPC6B","url":"https://www.omim.org/entry/610397"},{"mim_id":"610396","title":"TRAFFICKING PROTEIN PARTICLE COMPLEX, SUBUNIT 6A; TRAPPC6A","url":"https://www.omim.org/entry/610396"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TRAPPC6B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q86SZ2","domains":[{"cath_id":"3.30.1380.20","chopping":"1-158","consensus_level":"medium","plddt":92.1328,"start":1,"end":158}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86SZ2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86SZ2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86SZ2-F1-predicted_aligned_error_v6.png","plddt_mean":92.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TRAPPC6B","jax_strain_url":"https://www.jax.org/strain/search?query=TRAPPC6B"},"sequence":{"accession":"Q86SZ2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86SZ2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86SZ2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86SZ2"}},"corpus_meta":[{"pmid":"28397838","id":"PMC_28397838","title":"Mapping autosomal recessive intellectual disability: combined microarray and exome sequencing identifies 26 novel candidate genes in 192 consanguineous families.","date":"2017","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/28397838","citation_count":146,"is_preprint":false},{"pmid":"28626029","id":"PMC_28626029","title":"A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features.","date":"2017","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28626029","citation_count":40,"is_preprint":false},{"pmid":"33708385","id":"PMC_33708385","title":"Circular RNA TRAPPC6B inhibits intracellular Mycobacterium tuberculosis growth while inducing autophagy in macrophages by targeting microRNA-874-3p.","date":"2021","source":"Clinical & translational immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33708385","citation_count":35,"is_preprint":false},{"pmid":"27672095","id":"PMC_27672095","title":"Trs33-Containing TRAPP IV: A Novel Autophagy-Specific Ypt1 GEF.","date":"2016","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27672095","citation_count":26,"is_preprint":false},{"pmid":"32188865","id":"PMC_32188865","title":"RAB5A and TRAPPC6B are novel targets for Shiga toxin 2a inactivation in kidney epithelial cells.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32188865","citation_count":10,"is_preprint":false},{"pmid":"27569842","id":"PMC_27569842","title":"A TRAPPC6B splicing variant associates to restless legs syndrome.","date":"2016","source":"Parkinsonism & related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/27569842","citation_count":8,"is_preprint":false},{"pmid":"37713627","id":"PMC_37713627","title":"TRAPPC6B biallelic variants cause a neurodevelopmental disorder with TRAPP II and trafficking disruptions.","date":"2024","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/37713627","citation_count":5,"is_preprint":false},{"pmid":"39273027","id":"PMC_39273027","title":"A Humanized Yeast Model for Studying TRAPP Complex Mutations; Proof-of-Concept Using Variants from an Individual with a TRAPPC1-Associated Neurodevelopmental Syndrome.","date":"2024","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/39273027","citation_count":4,"is_preprint":false},{"pmid":"31687267","id":"PMC_31687267","title":"Further Delineation of the TRAPPC6B Disorder: Report on a New Family and Review.","date":"2019","source":"Journal of pediatric genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31687267","citation_count":3,"is_preprint":false},{"pmid":"35150401","id":"PMC_35150401","title":"Description of novel variants in consanguineous Pakistani families affected with intellectual disability.","date":"2022","source":"Genes & genomics","url":"https://pubmed.ncbi.nlm.nih.gov/35150401","citation_count":1,"is_preprint":false},{"pmid":"40350395","id":"PMC_40350395","title":"[Analysis of clinical phenotype and gene variation of a child with neurodevelopmental disorder caused by homozygous variation of TRAPPC6B gene].","date":"2025","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40350395","citation_count":0,"is_preprint":false},{"pmid":"41356416","id":"PMC_41356416","title":"Macrophage targeted cellular microparticles synergize anti-tuberculosis therapy combining CircRNA-mediated host immune defense and antibiotic killing.","date":"2025","source":"Materials today. Bio","url":"https://pubmed.ncbi.nlm.nih.gov/41356416","citation_count":0,"is_preprint":false},{"pmid":"42238340","id":"PMC_42238340","title":"Transcriptome-wide association study of prostate cancer in the Chinese population.","date":"2025","source":"Asian journal of urology","url":"https://pubmed.ncbi.nlm.nih.gov/42238340","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.08.04.605925","title":"A humanized yeast model for studying TRAPP complex mutations; proof-of-concept using variants from an individual with a  <i>TRAPPC1</i>  -associated neurodevelopmental syndrome","date":"2024-08-06","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.04.605925","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9761,"output_tokens":1717,"usd":0.027519,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8593,"output_tokens":2164,"usd":0.048532,"stage2_stop_reason":"end_turn"},"total_usd":0.076051,"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\": 2024,\n      \"finding\": \"TRAPPC6B preferentially associates with the TRAPP II complex over TRAPP III, as shown by co-immunoprecipitation experiments where TRAPPC6B co-precipitated significantly more with TRAPP II, while its homologue TRAPPC6A co-precipitated equally with TRAPP II and TRAPP III.\",\n      \"method\": \"Co-immunoprecipitation from patient-derived fibroblasts and cell lines\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with comparison to paralogue TRAPPC6A, single lab, two orthogonal comparisons\",\n      \"pmids\": [\"37713627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss-of-function mutation in TRAPPC6B (c.454C>T, p.Q152*) reduces the rate of trafficking into the Golgi apparatus and causes Golgi fragmentation in patient-derived fibroblasts, both of which were rescued by wild-type TRAPPC6B re-expression.\",\n      \"method\": \"Trafficking assay and Golgi morphology imaging in patient-derived fibroblasts with rescue experiment\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue experiment with wild-type TRAPPC6B, direct Golgi trafficking and morphology readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37713627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The TRAPPC6B p.Q152* mutant shows weakened interaction with TRAPP binding partner TRAPPC3, and patient-derived fibroblasts with this variant show reduced levels of TRAPPC6B as well as TRAPP II complex-specific members TRAPPC9 and TRAPPC10, while TRAPPC6A levels are elevated.\",\n      \"method\": \"Co-immunoprecipitation and Western blotting in patient-derived fibroblasts\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus protein level quantification, single lab, multiple TRAPP subunits assessed\",\n      \"pmids\": [\"37713627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Neuronal knockdown of TRAPPC6B in Drosophila impairs locomotion and leads to wing posture defects, supporting a role for TRAPPC6B in neuromotor function.\",\n      \"method\": \"Drosophila TRAPPC6B-deficiency model with neuronal-specific RNAi knockdown and behavioral assays\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo loss-of-function with defined behavioral phenotype in a model organism, single lab\",\n      \"pmids\": [\"37713627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRAPPC6B encodes a core subunit of TRAPP I complex; a homozygous splice mutation causing exon-skipping and loss of TRAPPC6B function in patients leads to microcephaly and neuronal hyperexcitability, and zebrafish trappc6b morphants replicate the human phenotype with decreased head size and lower seizure threshold.\",\n      \"method\": \"Patient fibroblast splicing assay (minigene and endogenous transcript), zebrafish morpholino knockdown with phenotypic readout\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — zebrafish knockdown with defined phenotype and patient splicing validation, single lab\",\n      \"pmids\": [\"28626029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A TRAPPC6B c.485G>A splice-site variant promotes exon 3-skipping and disrupts normal TRAPPC6B transcript processing, as demonstrated by minigene transfection assay and analysis of patient transcripts.\",\n      \"method\": \"Minigene transfection splicing assay and RT-PCR of patient transcripts\",\n      \"journal\": \"Parkinsonism & related disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct splicing assay with minigene and patient material, single lab, single method\",\n      \"pmids\": [\"27569842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RNAi-mediated silencing of TRAPPC6B in ACHN human renal epithelial cells confers protection against Shiga toxin 2a cytotoxicity, linking TRAPPC6B to intracellular Shiga toxin trafficking.\",\n      \"method\": \"RNAi knockdown with cell viability readout after Shiga toxin challenge\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single RNAi knockdown experiment with cytotoxicity readout, no mechanistic pathway placement, single lab\",\n      \"pmids\": [\"32188865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Human TRAPPC6B can functionally replace its yeast counterpart (Trs33) in Saccharomyces cerevisiae, demonstrating functional conservation of the protein across species.\",\n      \"method\": \"CRISPR/Cas9-mediated humanized yeast complementation assay\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct genetic complementation in yeast with growth/function readout, single lab\",\n      \"pmids\": [\"39273027\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TRAPPC6B is a core subunit of TRAPP complexes that is preferentially incorporated into the TRAPP II complex (via interaction with TRAPPC3), where it is required for normal Golgi trafficking and Golgi integrity; loss-of-function variants disrupt TRAPP II complex stability, impair membrane trafficking to the Golgi, cause Golgi fragmentation, and result in neurodevelopmental defects including microcephaly and epilepsy as demonstrated in patient fibroblasts, zebrafish, and Drosophila models.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TRAPPC6B is a core subunit of the multimeric TRAPP (transport protein particle) tethering complexes required for membrane trafficking to and integrity of the Golgi apparatus [#1, #4]. It is preferentially incorporated into the TRAPP II complex through interaction with TRAPPC3, distinguishing it from its paralogue TRAPPC6A, which partitions equally between TRAPP II and TRAPP III [#0]. Loss-of-function variants destabilize the complex: the p.Q152* truncation weakens binding to TRAPPC3 and lowers cellular levels of TRAPPC6B together with the TRAPP II-specific subunits TRAPPC9 and TRAPPC10, with a compensatory rise in TRAPPC6A [#2]. The functional consequence is slowed trafficking into the Golgi and Golgi fragmentation, both rescued by wild-type re-expression [#1]. This trafficking function is evolutionarily conserved, as human TRAPPC6B complements deletion of its yeast orthologue Trs33 [#7]. Disrupting TRAPPC6B causes a neurodevelopmental disorder featuring microcephaly, neuronal hyperexcitability, and epilepsy, established through patient variants and recapitulated by zebrafish morphants showing reduced head size and lowered seizure threshold and by neuronal Drosophila knockdown causing locomotor and wing-posture defects [#3, #4].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established that specific TRAPPC6B sequence variants disrupt normal transcript processing, providing the first molecular handle on how the gene is inactivated in disease.\",\n      \"evidence\": \"Minigene transfection splicing assay and RT-PCR of patient transcripts\",\n      \"pmids\": [\"27569842\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not assess the consequence for TRAPP complex assembly or trafficking\", \"No in vivo phenotype linked to the splicing defect\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected TRAPPC6B loss-of-function to a defined neurodevelopmental phenotype, demonstrating the gene is required for normal brain development and neuronal excitability.\",\n      \"evidence\": \"Patient fibroblast splicing assay plus zebrafish morpholino knockdown with microcephaly and seizure-threshold readouts\",\n      \"pmids\": [\"28626029\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino knockdown susceptible to off-target effects, no rescue reported\", \"Subcellular trafficking mechanism not addressed\", \"Assigned to TRAPP I rather than resolving complex specificity\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Implicated TRAPPC6B in an intracellular toxin trafficking route, hinting at the breadth of cargo whose transport depends on the protein.\",\n      \"evidence\": \"RNAi knockdown in ACHN renal epithelial cells with Shiga toxin 2a cytotoxicity readout\",\n      \"pmids\": [\"32188865\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single RNAi knockdown without rescue or reciprocal validation\", \"No mechanistic placement within the trafficking pathway\", \"Relevance to neuronal phenotype unestablished\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved which TRAPP subcomplex TRAPPC6B belongs to and showed how a truncating variant destabilizes it, explaining the trafficking defect mechanistically.\",\n      \"evidence\": \"Co-IP comparing TRAPP II vs III association and against paralogue TRAPPC6A, Western blot quantification, Golgi trafficking/morphology assays with wild-type rescue in patient fibroblasts, plus Drosophila neuronal RNAi behavioral assays\",\n      \"pmids\": [\"37713627\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of how TRAPPC6B is incorporated into TRAPP II\", \"Mechanism by which TRAPP II loss produces neuronal hyperexcitability not defined\", \"Identity of GTPase substrate/effectors at the Golgi not addressed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated functional conservation of TRAPPC6B from yeast to human, confirming the core trafficking role is preserved across species.\",\n      \"evidence\": \"CRISPR/Cas9 humanized yeast complementation of Trs33 deletion with growth readout\",\n      \"pmids\": [\"39273027\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Complementation does not map the human-specific TRAPP II interactions\", \"Does not address neuronal function directly\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TRAPP II-dependent Golgi trafficking failure translates into microcephaly and neuronal hyperexcitability at the cellular level remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identified molecular link between Golgi fragmentation and neuronal excitability\", \"No structural basis for TRAPPC6B incorporation into TRAPP II\", \"Cargo spectrum requiring TRAPPC6B in neurons undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [\"TRAPP II\", \"TRAPP complex\"],\n    \"partners\": [\"TRAPPC3\", \"TRAPPC9\", \"TRAPPC10\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}