{"gene":"RABL2A","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":1999,"finding":"RABL2A and RABL2B were identified as two closely related genes encoding members of the RAB family of small GTPases, differing by only three conservative amino acid changes over 228 residues, with ubiquitous expression and two distinct transcripts arising from differential splicing of an intron in the 3' UTR.","method":"Northern blot analysis, genomic mapping, sequence analysis","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 — original characterization with sequence and expression analysis; single lab","pmids":["10444334"],"is_preprint":false},{"year":2019,"finding":"RABL2 (encompassing near-identical paralogs RABL2A and RABL2B) is recruited to the mother centriole in a manner dependent on distal appendage proteins CEP164 and CEP83, and positively controls ciliary localization of GPCRs (GPR161 and HTR6) by physically associating with these receptors; this function is independent of TULP3 and requires interaction with CEP19 and the IFT-B complex.","method":"siRNA silencing, overexpression, co-immunoprecipitation, immunofluorescence microscopy, epistasis with CEP19 and IFT-B complex","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KD, OE, Co-IP, epistasis), reciprocal validation of binding partners, clear cellular phenotype","pmids":["30578315"],"is_preprint":false},{"year":2020,"finding":"Two missense variants in RABL2A (L119F and V158F) destabilize the protein in vitro and, when introduced as homozygous knock-in alleles in mice, cause ciliopathy-associated phenotypes including male infertility, heterotaxia, pre-axial polydactyly, neural tube defects, and hydrocephalus, establishing RABL2A as essential for normal cilia and flagella function.","method":"In silico structural prediction, in vitro protein stability assays, knock-in mouse models (homozygous SNP mice), phenotypic analysis","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro assay + in vivo knock-in validation with multiple ciliopathy phenotypes, computational and experimental convergence","pmids":["33075816"],"is_preprint":false},{"year":2014,"finding":"RABL2A protein localizes to the tail of human sperm, with a subcellular distribution highly conserved between mouse and human, linking its localization to a potential role in sperm flagellar function.","method":"Immunostaining (immunofluorescence) of human sperm","journal":"Fertility and sterility","confidence":"Medium","confidence_rationale":"Tier 3 — direct localization by immunostaining, single lab, no functional perturbation","pmids":["24825419"],"is_preprint":false},{"year":2021,"finding":"RABL2A interacts with CCDC34 specifically in its GTP-bound state (Q80L constitutively active mutant binds CCDC34; S35N GDP-locked mutant does not), and the RABL2A-CCDC34 axis activates p38/MAPK and JNK/MAPK signaling to promote sorafenib resistance in hepatocellular carcinoma cells.","method":"Co-immunoprecipitation, immunofluorescence, GTPase mutant overexpression (Q80L and S35N), siRNA knockdown, CCK-8, TUNEL, Annexin V assays, western blot, in vivo xenograft","journal":"DNA and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP, GTPase state-dependent interaction, multiple functional readouts; single lab","pmids":["34767735"],"is_preprint":false},{"year":2023,"finding":"RABL2A physically interacts with the long noncoding RNA SNHG15 and mediates SNHG15-promoted SARS-CoV-2 spike pseudovirus entry; RABL2A knockdown abolishes the SNHG15-dependent enhancement of viral entry.","method":"SARS-CoV-2 spike pseudotyped lentivirus luciferase assay, RNA-protein interaction assay, siRNA knockdown, overexpression","journal":"RNA biology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, interaction shown but mechanism of RABL2A action in entry not biochemically defined","pmids":["37528621"],"is_preprint":false},{"year":2011,"finding":"RABL2A splice-isoform ratios are maintained at constant levels in genetically diverse human lymphoblastoid cell lines independently of gene expression level, and subtle tandem-acceptor splicing at RABL2A/B is highly constrained and depends on upstream donor sequence content, suggesting regulated alternative splicing rather than noisy processing.","method":"Quantitative isoform-ratio measurement across multiple cell lines (Pyrosequencing-based), comparison across individuals and with chimpanzee lines","journal":"Genetics","confidence":"Low","confidence_rationale":"Tier 3 — describes a splicing regulatory property but no direct functional consequence of RABL2A isoforms established","pmids":["21220357"],"is_preprint":false}],"current_model":"RABL2A is an atypical RAB-family small GTPase that, in its GTP-bound active state, localizes to the mother centriole (via CEP164/CEP83) and—through interactions with CEP19 and the IFT-B complex—controls the trafficking of GPCRs (e.g., GPR161, HTR6) into primary cilia; it also localizes to the sperm flagellum where it is essential for normal ciliary/flagellar function, and in a GTP-dependent manner it engages CCDC34 to activate p38/MAPK and JNK/MAPK signaling."},"narrative":{"teleology":[{"year":1999,"claim":"Identification of RABL2A and its near-identical paralog RABL2B as ubiquitously expressed RAB-family GTPases established a new gene pair whose functional significance was unknown.","evidence":"Northern blot, genomic mapping, and sequence analysis","pmids":["10444334"],"confidence":"Medium","gaps":["No functional role assigned beyond sequence classification as RAB-family members","Functional distinction between RABL2A and RABL2B not addressed"]},{"year":2011,"claim":"Demonstration that RABL2A splice-isoform ratios are tightly constrained across genetically diverse individuals suggested regulated post-transcriptional control, but did not define a functional consequence of isoform choice.","evidence":"Pyrosequencing-based isoform quantification across human lymphoblastoid cell lines","pmids":["21220357"],"confidence":"Low","gaps":["No functional consequence of the alternative isoforms was established","Mechanism regulating the constrained splicing ratio not elucidated"]},{"year":2014,"claim":"Localization of RABL2A to the sperm flagellum in both mouse and human provided the first subcellular context linking RABL2A to ciliary/flagellar biology.","evidence":"Immunofluorescence staining of human sperm","pmids":["24825419"],"confidence":"Medium","gaps":["Purely observational localization without functional perturbation","Molecular partners at the flagellum not identified"]},{"year":2019,"claim":"Establishing that RABL2 is recruited to the mother centriole via CEP164/CEP83 and controls GPCR ciliary entry through CEP19 and IFT-B defined a molecular pathway linking a centriolar GTPase to receptor trafficking into primary cilia.","evidence":"siRNA knockdown, overexpression, co-immunoprecipitation, immunofluorescence, epistasis analysis in cultured cells","pmids":["30578315"],"confidence":"High","gaps":["Structural basis of RABL2–CEP19 and RABL2–IFT-B interactions not resolved","How RABL2 GTP/GDP cycling is regulated at the centriole remains unknown","Whether RABL2A and RABL2B are functionally redundant in this pathway was not determined"]},{"year":2020,"claim":"In vivo knock-in of destabilizing RABL2A missense variants demonstrated that RABL2A is essential for cilia and flagella function, producing a spectrum of ciliopathy phenotypes including male infertility, heterotaxia, polydactyly, and neural tube defects.","evidence":"Homozygous knock-in mouse models (L119F, V158F), in vitro protein stability assays, phenotypic characterization","pmids":["33075816"],"confidence":"High","gaps":["Whether the variants specifically impair RABL2A–IFT-B or RABL2A–CEP19 interactions was not tested","Contribution of RABL2B compensation in vivo not defined","No human Mendelian disease family reported"]},{"year":2021,"claim":"Discovery that RABL2A engages CCDC34 in a GTP-dependent manner to activate p38/MAPK and JNK/MAPK signaling revealed a non-ciliary effector axis for this GTPase.","evidence":"Co-immunoprecipitation with GTPase-locked mutants (Q80L, S35N), siRNA knockdown, western blot, xenograft assays in hepatocellular carcinoma cells","pmids":["34767735"],"confidence":"Medium","gaps":["Whether the RABL2A–CCDC34 axis operates outside hepatocellular carcinoma contexts is unknown","Direct biochemical mechanism by which CCDC34 activates MAPK cascades not defined","Relationship between this signaling role and ciliary function not explored"]},{"year":2023,"claim":"A physical interaction between RABL2A and lncRNA SNHG15 was implicated in SARS-CoV-2 pseudovirus entry, but the biochemical mechanism remains undefined.","evidence":"Pseudotyped lentivirus luciferase assay, RNA-protein interaction assay, siRNA knockdown","pmids":["37528621"],"confidence":"Low","gaps":["Mechanism by which RABL2A facilitates viral entry is not biochemically defined","Finding not independently replicated","Physiological relevance to actual SARS-CoV-2 infection not established"]},{"year":null,"claim":"Key open questions include the identity of RABL2A's GEF and GAP, the structural basis of its effector interactions, whether RABL2A and RABL2B are functionally redundant in vivo, and whether human RABL2A mutations cause Mendelian ciliopathies.","evidence":"","pmids":[],"confidence":"Low","gaps":["No GEF or GAP for RABL2A has been identified","No crystal or cryo-EM structure of RABL2A or its complexes is available","Functional redundancy between RABL2A and RABL2B in vivo remains unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[0,1,4]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[1]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]}],"complexes":[],"partners":["CEP19","CEP164","CEP83","CCDC34","GPR161","HTR6"],"other_free_text":[]},"mechanistic_narrative":"RABL2A is an atypical RAB-family small GTPase that functions as a GTP-dependent regulator of ciliary trafficking and flagellar assembly. In its active GTP-bound state, RABL2A is recruited to the mother centriole through distal appendage proteins CEP164 and CEP83 and, via interactions with CEP19 and the IFT-B complex, controls the ciliary entry of GPCRs such as GPR161 and HTR6 independently of TULP3 [PMID:30578315]. Homozygous destabilizing missense mutations in mice cause ciliopathy phenotypes including heterotaxia, polydactyly, neural tube defects, hydrocephalus, and male infertility, establishing RABL2A as essential for normal cilia and flagella function [PMID:33075816]. RABL2A also engages CCDC34 in a GTP-dependent manner to activate p38/MAPK and JNK/MAPK signaling [PMID:34767735]."},"prefetch_data":{"uniprot":{"accession":"Q9UBK7","full_name":"Rab-like protein 2A","aliases":[],"length_aa":228,"mass_kda":26.1,"function":"Small GTPase that plays an essential role in male fertility, sperm intra-flagellar transport, and tail assembly. Binds, in a GTP-regulated manner, to a specific set of effector proteins including key proteins involved in cilia development and function and delivers them into the growing sperm tail","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9UBK7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RABL2A","classification":"Not Classified","n_dependent_lines":230,"n_total_lines":1047,"dependency_fraction":0.21967526265520534},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RABL2A","total_profiled":1310},"omim":[{"mim_id":"605413","title":"RAB, MEMBER OF RAS ONCOGENE FAMILY-LIKE 2B; RABL2B","url":"https://www.omim.org/entry/605413"},{"mim_id":"605412","title":"RAB, MEMBER OF RAS ONCOGENE FAMILY-LIKE 2A; RABL2A","url":"https://www.omim.org/entry/605412"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Centrosome","reliability":"Approved"},{"location":"Basal body","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"fallopian tube","ntpm":20.1}],"url":"https://www.proteinatlas.org/search/RABL2A"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9UBK7","domains":[{"cath_id":"3.40.50.300","chopping":"18-176","consensus_level":"high","plddt":88.1607,"start":18,"end":176}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBK7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBK7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBK7-F1-predicted_aligned_error_v6.png","plddt_mean":79.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RABL2A","jax_strain_url":"https://www.jax.org/strain/search?query=RABL2A"},"sequence":{"accession":"Q9UBK7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UBK7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UBK7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBK7"}},"corpus_meta":[{"pmid":"32058959","id":"PMC_32058959","title":"Multi-omics Data Integration for Identifying Osteoporosis Biomarkers and Their Biological Interaction and Causal Mechanisms.","date":"2020","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/32058959","citation_count":47,"is_preprint":false},{"pmid":"10444334","id":"PMC_10444334","title":"Two novel human RAB genes with near identical sequence each map to a telomere-associated region: the subtelomeric region of 22q13.3 and the ancestral telomere band 2q13.","date":"1999","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/10444334","citation_count":33,"is_preprint":false},{"pmid":"21655357","id":"PMC_21655357","title":"Genetic networks in the mouse retina: growth associated protein 43 and phosphatase tensin homolog network.","date":"2011","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/21655357","citation_count":28,"is_preprint":false},{"pmid":"30578315","id":"PMC_30578315","title":"RABL2 positively controls localization of GPCRs in mammalian primary cilia.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/30578315","citation_count":25,"is_preprint":false},{"pmid":"25112678","id":"PMC_25112678","title":"Complexin-1 and Foxp1 Expression Changes Are Novel Brain Effects of Alpha-Synuclein Pathology.","date":"2014","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/25112678","citation_count":23,"is_preprint":false},{"pmid":"33075816","id":"PMC_33075816","title":"Variants in RABL2A causing male infertility and ciliopathy.","date":"2020","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33075816","citation_count":14,"is_preprint":false},{"pmid":"24825419","id":"PMC_24825419","title":"Genetic variants in the RABL2A gene in fertile and oligoasthenospermic infertile men.","date":"2014","source":"Fertility and sterility","url":"https://pubmed.ncbi.nlm.nih.gov/24825419","citation_count":12,"is_preprint":false},{"pmid":"21220357","id":"PMC_21220357","title":"Constant splice-isoform ratios in human lymphoblastoid cells support the concept of a splico-stat.","date":"2011","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21220357","citation_count":10,"is_preprint":false},{"pmid":"20138207","id":"PMC_20138207","title":"Analysis of relative gene dosage and expression differences of the paralogs RABL2A and RABL2B by Pyrosequencing.","date":"2010","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/20138207","citation_count":9,"is_preprint":false},{"pmid":"34767735","id":"PMC_34767735","title":"RABL2A-CCDC34 Axis Promotes Sorafenib Resistance in Hepatocellular Carcinoma.","date":"2021","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/34767735","citation_count":7,"is_preprint":false},{"pmid":"23185754","id":"PMC_23185754","title":"[Study on gene differential expressions of substance and energy metabolism in chronic superficial gastritis patients of Pi deficiency syndrome and of pi-wei hygropyrexia syndrome].","date":"2012","source":"Zhongguo Zhong xi yi jie he za zhi Zhongguo Zhongxiyi jiehe zazhi = Chinese journal of integrated traditional and Western medicine","url":"https://pubmed.ncbi.nlm.nih.gov/23185754","citation_count":7,"is_preprint":false},{"pmid":"38846986","id":"PMC_38846986","title":"A transcriptome-wide association study identified susceptibility genes for hepatocellular carcinoma in East Asia.","date":"2024","source":"Gastroenterology report","url":"https://pubmed.ncbi.nlm.nih.gov/38846986","citation_count":4,"is_preprint":false},{"pmid":"37528621","id":"PMC_37528621","title":"SNHG15 aids SARS-CoV-2 entry via RABL2A.","date":"2023","source":"RNA biology","url":"https://pubmed.ncbi.nlm.nih.gov/37528621","citation_count":3,"is_preprint":false},{"pmid":"31528310","id":"PMC_31528310","title":"Highlighted role of VEGFA in follow up of celiac disease.","date":"2019","source":"Gastroenterology and hepatology from bed to bench","url":"https://pubmed.ncbi.nlm.nih.gov/31528310","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8788,"output_tokens":1707,"usd":0.025985},"stage2":{"model":"claude-opus-4-6","input_tokens":4969,"output_tokens":2028,"usd":0.113318},"total_usd":0.139303,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"RABL2A and RABL2B were identified as two closely related genes encoding members of the RAB family of small GTPases, differing by only three conservative amino acid changes over 228 residues, with ubiquitous expression and two distinct transcripts arising from differential splicing of an intron in the 3' UTR.\",\n      \"method\": \"Northern blot analysis, genomic mapping, sequence analysis\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — original characterization with sequence and expression analysis; single lab\",\n      \"pmids\": [\"10444334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RABL2 (encompassing near-identical paralogs RABL2A and RABL2B) is recruited to the mother centriole in a manner dependent on distal appendage proteins CEP164 and CEP83, and positively controls ciliary localization of GPCRs (GPR161 and HTR6) by physically associating with these receptors; this function is independent of TULP3 and requires interaction with CEP19 and the IFT-B complex.\",\n      \"method\": \"siRNA silencing, overexpression, co-immunoprecipitation, immunofluorescence microscopy, epistasis with CEP19 and IFT-B complex\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KD, OE, Co-IP, epistasis), reciprocal validation of binding partners, clear cellular phenotype\",\n      \"pmids\": [\"30578315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Two missense variants in RABL2A (L119F and V158F) destabilize the protein in vitro and, when introduced as homozygous knock-in alleles in mice, cause ciliopathy-associated phenotypes including male infertility, heterotaxia, pre-axial polydactyly, neural tube defects, and hydrocephalus, establishing RABL2A as essential for normal cilia and flagella function.\",\n      \"method\": \"In silico structural prediction, in vitro protein stability assays, knock-in mouse models (homozygous SNP mice), phenotypic analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro assay + in vivo knock-in validation with multiple ciliopathy phenotypes, computational and experimental convergence\",\n      \"pmids\": [\"33075816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RABL2A protein localizes to the tail of human sperm, with a subcellular distribution highly conserved between mouse and human, linking its localization to a potential role in sperm flagellar function.\",\n      \"method\": \"Immunostaining (immunofluorescence) of human sperm\",\n      \"journal\": \"Fertility and sterility\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct localization by immunostaining, single lab, no functional perturbation\",\n      \"pmids\": [\"24825419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RABL2A interacts with CCDC34 specifically in its GTP-bound state (Q80L constitutively active mutant binds CCDC34; S35N GDP-locked mutant does not), and the RABL2A-CCDC34 axis activates p38/MAPK and JNK/MAPK signaling to promote sorafenib resistance in hepatocellular carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, GTPase mutant overexpression (Q80L and S35N), siRNA knockdown, CCK-8, TUNEL, Annexin V assays, western blot, in vivo xenograft\",\n      \"journal\": \"DNA and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, GTPase state-dependent interaction, multiple functional readouts; single lab\",\n      \"pmids\": [\"34767735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RABL2A physically interacts with the long noncoding RNA SNHG15 and mediates SNHG15-promoted SARS-CoV-2 spike pseudovirus entry; RABL2A knockdown abolishes the SNHG15-dependent enhancement of viral entry.\",\n      \"method\": \"SARS-CoV-2 spike pseudotyped lentivirus luciferase assay, RNA-protein interaction assay, siRNA knockdown, overexpression\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, interaction shown but mechanism of RABL2A action in entry not biochemically defined\",\n      \"pmids\": [\"37528621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RABL2A splice-isoform ratios are maintained at constant levels in genetically diverse human lymphoblastoid cell lines independently of gene expression level, and subtle tandem-acceptor splicing at RABL2A/B is highly constrained and depends on upstream donor sequence content, suggesting regulated alternative splicing rather than noisy processing.\",\n      \"method\": \"Quantitative isoform-ratio measurement across multiple cell lines (Pyrosequencing-based), comparison across individuals and with chimpanzee lines\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — describes a splicing regulatory property but no direct functional consequence of RABL2A isoforms established\",\n      \"pmids\": [\"21220357\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RABL2A is an atypical RAB-family small GTPase that, in its GTP-bound active state, localizes to the mother centriole (via CEP164/CEP83) and—through interactions with CEP19 and the IFT-B complex—controls the trafficking of GPCRs (e.g., GPR161, HTR6) into primary cilia; it also localizes to the sperm flagellum where it is essential for normal ciliary/flagellar function, and in a GTP-dependent manner it engages CCDC34 to activate p38/MAPK and JNK/MAPK signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RABL2A is an atypical RAB-family small GTPase that functions as a GTP-dependent regulator of ciliary trafficking and flagellar assembly. In its active GTP-bound state, RABL2A is recruited to the mother centriole through distal appendage proteins CEP164 and CEP83 and, via interactions with CEP19 and the IFT-B complex, controls the ciliary entry of GPCRs such as GPR161 and HTR6 independently of TULP3 [PMID:30578315]. Homozygous destabilizing missense mutations in mice cause ciliopathy phenotypes including heterotaxia, polydactyly, neural tube defects, hydrocephalus, and male infertility, establishing RABL2A as essential for normal cilia and flagella function [PMID:33075816]. RABL2A also engages CCDC34 in a GTP-dependent manner to activate p38/MAPK and JNK/MAPK signaling [PMID:34767735].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of RABL2A and its near-identical paralog RABL2B as ubiquitously expressed RAB-family GTPases established a new gene pair whose functional significance was unknown.\",\n      \"evidence\": \"Northern blot, genomic mapping, and sequence analysis\",\n      \"pmids\": [\"10444334\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No functional role assigned beyond sequence classification as RAB-family members\",\n        \"Functional distinction between RABL2A and RABL2B not addressed\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstration that RABL2A splice-isoform ratios are tightly constrained across genetically diverse individuals suggested regulated post-transcriptional control, but did not define a functional consequence of isoform choice.\",\n      \"evidence\": \"Pyrosequencing-based isoform quantification across human lymphoblastoid cell lines\",\n      \"pmids\": [\"21220357\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No functional consequence of the alternative isoforms was established\",\n        \"Mechanism regulating the constrained splicing ratio not elucidated\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Localization of RABL2A to the sperm flagellum in both mouse and human provided the first subcellular context linking RABL2A to ciliary/flagellar biology.\",\n      \"evidence\": \"Immunofluorescence staining of human sperm\",\n      \"pmids\": [\"24825419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Purely observational localization without functional perturbation\",\n        \"Molecular partners at the flagellum not identified\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing that RABL2 is recruited to the mother centriole via CEP164/CEP83 and controls GPCR ciliary entry through CEP19 and IFT-B defined a molecular pathway linking a centriolar GTPase to receptor trafficking into primary cilia.\",\n      \"evidence\": \"siRNA knockdown, overexpression, co-immunoprecipitation, immunofluorescence, epistasis analysis in cultured cells\",\n      \"pmids\": [\"30578315\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of RABL2–CEP19 and RABL2–IFT-B interactions not resolved\",\n        \"How RABL2 GTP/GDP cycling is regulated at the centriole remains unknown\",\n        \"Whether RABL2A and RABL2B are functionally redundant in this pathway was not determined\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"In vivo knock-in of destabilizing RABL2A missense variants demonstrated that RABL2A is essential for cilia and flagella function, producing a spectrum of ciliopathy phenotypes including male infertility, heterotaxia, polydactyly, and neural tube defects.\",\n      \"evidence\": \"Homozygous knock-in mouse models (L119F, V158F), in vitro protein stability assays, phenotypic characterization\",\n      \"pmids\": [\"33075816\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the variants specifically impair RABL2A–IFT-B or RABL2A–CEP19 interactions was not tested\",\n        \"Contribution of RABL2B compensation in vivo not defined\",\n        \"No human Mendelian disease family reported\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Discovery that RABL2A engages CCDC34 in a GTP-dependent manner to activate p38/MAPK and JNK/MAPK signaling revealed a non-ciliary effector axis for this GTPase.\",\n      \"evidence\": \"Co-immunoprecipitation with GTPase-locked mutants (Q80L, S35N), siRNA knockdown, western blot, xenograft assays in hepatocellular carcinoma cells\",\n      \"pmids\": [\"34767735\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the RABL2A–CCDC34 axis operates outside hepatocellular carcinoma contexts is unknown\",\n        \"Direct biochemical mechanism by which CCDC34 activates MAPK cascades not defined\",\n        \"Relationship between this signaling role and ciliary function not explored\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A physical interaction between RABL2A and lncRNA SNHG15 was implicated in SARS-CoV-2 pseudovirus entry, but the biochemical mechanism remains undefined.\",\n      \"evidence\": \"Pseudotyped lentivirus luciferase assay, RNA-protein interaction assay, siRNA knockdown\",\n      \"pmids\": [\"37528621\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Mechanism by which RABL2A facilitates viral entry is not biochemically defined\",\n        \"Finding not independently replicated\",\n        \"Physiological relevance to actual SARS-CoV-2 infection not established\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the identity of RABL2A's GEF and GAP, the structural basis of its effector interactions, whether RABL2A and RABL2B are functionally redundant in vivo, and whether human RABL2A mutations cause Mendelian ciliopathies.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No GEF or GAP for RABL2A has been identified\",\n        \"No crystal or cryo-EM structure of RABL2A or its complexes is available\",\n        \"Functional redundancy between RABL2A and RABL2B in vivo remains unresolved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"CEP19\",\n      \"CEP164\",\n      \"CEP83\",\n      \"CCDC34\",\n      \"GPR161\",\n      \"HTR6\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}