{"gene":"ARL13B","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2008,"finding":"ARL13B protein localizes to cilia in primary neurons and is required for cilia function; overexpression of human wild-type but not patient mutant ARL13B rescued the Arl13b scorpion zebrafish mutant, establishing evolutionary conservation of its ciliary role.","method":"Zebrafish rescue experiments, immunofluorescence localization in murine neurons","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct rescue assays in zebrafish with wild-type vs. patient mutant, replicated across species contexts","pmids":["18674751"],"is_preprint":false},{"year":2010,"finding":"C. elegans ARL-13/Arl13b localizes to proximal ciliary membranes via palmitoylation modification motifs; loss-of-function causes defects in cilium morphology/ultrastructure, abnormal accumulation of ciliary transmembrane proteins, elevated PKD-2 ciliary abundance, and destabilized anterograde intraflagellar transport (IFT). Genetic interaction with other ciliogenic/IFT genes confirmed its role in anterograde IFT stability.","method":"C. elegans genetics, fluorescence microscopy, IFT motility assays, genetic epistasis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (localization, ultrastructure, IFT assays, epistasis) in a single rigorous study","pmids":["20231383"],"is_preprint":false},{"year":2009,"finding":"Multiple regions of Arl13b are required for its ciliary localization, and ciliary localization is essential for in vivo function; ciliary-localization-defective mutants cannot rescue arl13b/scorpion zebrafish phenotypes.","method":"Zebrafish rescue experiments with deletion and point mutants","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic mutagenesis rescue assay with multiple mutant variants in vivo","pmids":["19906870"],"is_preprint":false},{"year":2011,"finding":"Arl13b regulates the ciliary entry and distribution of Smoothened (Smo); in Arl13b-null cilia, Smo is enriched regardless of Shh pathway stimulation, indicating Arl13b controls the dynamic localization of Smo within the cilium and thereby regulates Sonic hedgehog signaling.","method":"Mouse mutant analysis, immunofluorescence of Smo localization in Arl13b-null vs. wild-type cilia in vitro","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative localization in knockout cells and embryos with stimulation conditions, multiple orthogonal approaches","pmids":["21976698"],"is_preprint":false},{"year":2012,"finding":"ARL13B physically interacts with INPP5E and is required for ciliary targeting of INPP5E; JBTS-causing missense mutations in ARL13B disrupt the ARL13B-INPP5E interaction. ARL13B, INPP5E, PDE6D, and CEP164 form a distinct functional network for INPP5E ciliary targeting.","method":"Protein-protein interaction studies (Co-IP, binding assays), cell-based localization, patient mutation analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction studies combined with patient mutation functional testing and rescue experiments","pmids":["23150559"],"is_preprint":false},{"year":2012,"finding":"Arl13b is required in primary cilia for proper migration and placement of interneurons in the developing cerebral cortex; guidance cue receptors essential for interneuronal migration localize to interneuronal primary cilia, but their concentration and dynamics are altered in the absence of Arl13b.","method":"Live imaging of interneuronal cilia, mouse conditional knockout, immunofluorescence of guidance receptors","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging combined with knockout mouse model and receptor localization analysis","pmids":["23153492"],"is_preprint":false},{"year":2012,"finding":"Arl13b is required for endocytic recycling traffic; silencing Arl13b reduces CD1a surface expression and delays CD1a recycling, causes clustering of early endosomes and accumulation of endocytic cargo. Arl13b colocalizes with Arf6 and Rab22a (endocytic recycling markers) and interacts with the actin cytoskeleton.","method":"shRNA knockdown screen, flow cytometry for CD1a surface expression, fluorescence colocalization, endosome morphology analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined phenotypic readout with colocalization, single lab, multiple approaches","pmids":["23223633"],"is_preprint":false},{"year":2013,"finding":"ARL13B/ARL-13 is restricted to an Inv-like subciliary membrane compartment; compartmentalization requires a C-terminal RVVP motif and membrane anchoring. IFT-A/B, IFT-dynein and BBS genes prevent ARL-13 periciliary membrane accumulation; MKS/NPHP modules additionally inhibit ARL-13 at the transition zone. ARL-13 undergoes IFT-like motility and human ARL13B has functional associations with IFT-B complexes via IFT46 and IFT74 interactions.","method":"C. elegans genetics (>20 mutants), quantitative fluorescence imaging, in vivo FRAP, quantitative protein complex analysis (mass spectrometry)","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (FRAP, MS interactome, systematic genetics) across species","pmids":["24339792"],"is_preprint":false},{"year":2014,"finding":"ARL13B directly interacts with tubulin via its G-domain independently of GTPase activity; this interaction is required for ARL13B to anchor ciliary membrane proteins (Smo, SSTR3) uniformly along the cilium. Mutants lacking the tubulin-binding G-domain fail to rescue ciliogenesis defects of null MEFs and cause uneven distribution of membrane proteins.","method":"Co-immunoprecipitation, in vitro binding assays, mutagenesis, immunofluorescence in MEFs","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct interaction demonstrated in vitro and in vivo with structure-function mutagenesis, single lab","pmids":["29592971"],"is_preprint":false},{"year":2014,"finding":"Overexpression of Arl13b increases ciliary length by inducing protrusion of the ciliary membrane followed by axonemal extension; GTPase activity of Arl13b is essential for this membrane extension. Arl13b is induced by ciliogenic transcription factors FoxJ1 and Rfx and acts downstream of them to regulate ciliary length.","method":"Zebrafish overexpression and loss-of-function, mammalian cell overexpression, mutant analysis including GTPase-dead variants","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression and mutant rescue in two systems with GTPase-dead variant, single lab","pmids":["25448689"],"is_preprint":false},{"year":2014,"finding":"Arl13b localizes to circular dorsal ruffles (CDRs) and interacts with non-muscle myosin heavy chain IIA (Myh9) as an effector; both proteins are required for CDR formation and cell migration. Arl13b silencing impairs neural crest cell migration in zebrafish.","method":"Co-immunoprecipitation, RNAi knockdown, fluorescence microscopy of CDRs, zebrafish neural crest migration assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional CDR and migration assays, single lab, two orthogonal methods","pmids":["24777479"],"is_preprint":false},{"year":2014,"finding":"Crystal structure of Chlamydomonas reinhardtii Arl13B reveals an incomplete active site accounting for absence of intrinsic GTP hydrolysis. Patient mutations R79Q and R200C destabilize important intramolecular interactions; Arg79 is crucial for the GDP/GTP conformational change typical of Arf/Arl proteins.","method":"X-ray crystallography, biochemical GTPase assays, structural analysis of patient mutants","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with biochemical validation, single lab but structural-level evidence","pmids":["24168557"],"is_preprint":false},{"year":2015,"finding":"Arl13B is the guanine nucleotide exchange factor (GEF) for Arl3; GEF activity is mediated by the G-domain plus an additional C-terminal helix, with switch regions of Arl13B involved in interaction with Arl3. Overexpression of Arl13B increases Arl3·GTP levels in mammalian cells, and Joubert syndrome patient mutations impair GEF activity. This spatial restriction of Arl3 activation to cilia generates an Arl3·GTP compartment for ciliary cargo release.","method":"In vitro GEF assay, structural analysis, overexpression in mammalian cells, patient mutation analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical GEF reconstitution plus cellular validation and patient mutation testing, independently confirmed in other studies","pmids":["26551564"],"is_preprint":false},{"year":2015,"finding":"The GTP-bound form of Arl13b preferentially binds exocyst subunits Sec8, Exo70, and Sec5 (consistent with the exocyst being an effector); Arl13b binds directly to Sec8 and Sec5. Genetic interaction between arl13b and exocyst subunit sec10 in zebrafish shows synergistic cilia-dependent phenotypes, and Arl13b and the exocyst function in the same ciliogenesis pathway.","method":"Pulldown assays (GTP vs. GDP-bound Arl13b), direct binding assays, zebrafish morphant genetic interaction, conditional mouse knockout","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding biochemistry plus in vivo genetic epistasis in two organisms","pmids":["26582389"],"is_preprint":false},{"year":2016,"finding":"ARL13B interacts with the IFT46-IFT56 dimer of the IFT-B complex; however, ciliary localization of ARL13B is independent of IFT-B interaction but dependent on the C-terminal RVEP ciliary-targeting sequence. In ARL13B-knockout cells, IFT-A and IFT-B complexes accumulate at ciliary tips and GPR161 cannot exit cilia in response to Smoothened agonist (retrograde exit defect). This abnormal phenotype is rescued by wild-type ARL13B and by an IFT-B-interaction-defective mutant, but not by INPP5E-binding-defective or ciliary-localization-defective mutants, indicating ARL13B regulates IFT-A-mediated retrograde protein trafficking through its interaction with INPP5E.","method":"Visible immunoprecipitation assay, ARL13B knockout cells, immunofluorescence, rescue with mutants","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic knockout + rescue with structure-function mutants and direct interaction assay, multiple orthogonal methods","pmids":["27927754"],"is_preprint":false},{"year":2017,"finding":"Purified recombinant murine Arl13b is biochemically atypical: it binds GTP with lower intrinsic GTPase activity and functions as a GEF for ARL3. Three human Joubert syndrome missense mutations were biochemically characterized. Murine Arl13b is also a substrate for casein kinase 2 phosphorylation.","method":"In vitro biochemical assays (nucleotide binding, intrinsic and GAP-stimulated GTPase, GEF activity), recombinant protein purification, patient mutation analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein and mutagenesis, single lab but multiple assays","pmids":["28487361"],"is_preprint":false},{"year":2017,"finding":"ARL13B palmitoylation occurs in vivo (mouse kidneys) and is required for trafficking to cilia and for ARL13B function within cilia; palmitoylation dramatically increases ARL13B protein stability. Myristoylation can substitute for palmitoylation in ciliary localization but not ciliary function. Blockade of depalmitoylation slows ARL13B degradation during cilia resorption.","method":"Biochemical palmitoylation assays, cellular localization studies, in vivo mouse kidney experiments, stability assays, cilia rescue experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vivo palmitoylation confirmed biochemically, multiple mutants tested, stability and localization linked to function","pmids":["28848045"],"is_preprint":false},{"year":2017,"finding":"Arl13b interacts with Smoothened (Smo) and regulates Smo stability, trafficking, and ciliary localization, which are crucial for Hedgehog signaling in gastric cancer.","method":"Co-immunoprecipitation, cell-based trafficking assays, proliferation/migration/invasion assays, in vivo tumor models","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional trafficking assays, single lab, two orthogonal methods","pmids":["28611043"],"is_preprint":false},{"year":2017,"finding":"A novel ARL13B variant (Gly75Arg) causes Joubert syndrome with a marked loss of ARL3 GEF activity while retaining GTPase activity and cilia/Shh-rescue function, establishing a direct correlation between ARL13B's ARL3 GEF activity loss and Joubert syndrome.","method":"Whole-exome sequencing, GEF activity assays, cilia length rescue, Shh signaling rescue in null cells","journal":"European journal of human genetics : EJHG","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — biochemical GEF assay with patient mutation directly compared to wild-type and null controls, multiple functional assays","pmids":["29255182"],"is_preprint":false},{"year":2018,"finding":"ARL13B controls axoneme polyglutamylation by interacting with RAB11 effector FIP5 to promote ciliary import of glutamylases TTLL5 and TTLL6. Hypoglutamylation caused by ARL13B deficiency impairs ciliary signaling by disrupting sensory receptor anchoring and signaling molecule trafficking, and can be rescued by depletion of deglutamylase CCP5.","method":"Co-immunoprecipitation (ARL13B-FIP5 interaction), immunofluorescence of TTLL5/6 localization, CCP5 depletion rescue, cilia signaling assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct interaction demonstrated by Co-IP plus functional rescue with deglutamylase depletion, multiple orthogonal experiments","pmids":["30120249"],"is_preprint":false},{"year":2018,"finding":"TULP3 is required for ciliary localization of membrane-associated proteins ARL13B and INPP5E; this function requires TULP3's ability to bind IFT-A. TUB (another tubby family member) can substitute for TULP3 in rescuing ciliary localization of ARL13B, indicating functional redundancy.","method":"TULP3-knockout RPE1 cells, immunofluorescence, rescue with wild-type and IFT-A-binding-deficient TULP3 mutants","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with rescue using specific mutant, single lab, clear phenotypic readout","pmids":["30583862"],"is_preprint":false},{"year":2018,"finding":"ARL13B is required at multiple stages of retinogenesis including early retinal progenitor proliferation, photoreceptor cilia development, and outer segment disc morphogenesis. Loss of ARL13B in adult photoreceptors causes mislocalization of rhodopsin, prenylated PDE6, and IFT88, and loss of photoresponse.","method":"Conditional knockout mouse models (Six3-Cre pan-retina and Pde6g-CreERT2 inducible), ERG, immunofluorescence, electron microscopy","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent conditional KO models with ultrastructural, functional, and protein trafficking analyses","pmids":["30573647"],"is_preprint":false},{"year":2019,"finding":"Arl13b functions outside primary cilia in Shh-mediated axon guidance; Arl13b protein is detected in axons and growth cones, and a cilia-localization-deficient Arl13b variant is sufficient to mediate Shh-dependent commissural axon guidance both in vitro and in vivo.","method":"In vivo conditional knockout, in vitro axon guidance assays, immunolocalization in axons/growth cones, cilia-excluded variant rescue","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO with specific guidance phenotype plus cilia-excluded variant rescue, multiple orthogonal methods","pmids":["31825820"],"is_preprint":false},{"year":2019,"finding":"AHI1 promotes Arl13b ciliary recruitment and regulates Arl13b stability via the proteasome; loss of Ahi1 reduces ciliary membrane localization of Arl13b, decreases non-membrane-associated Arl13b stability, reduces Shh signaling, and causes defects in cell motility.","method":"Ahi1-knockout MEFs, immunofluorescence, stability assays with proteasome inhibition, Shh signaling readouts, migration assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with multiple functional readouts and stability mechanistic follow-up, single lab","pmids":["31391239"],"is_preprint":false},{"year":2019,"finding":"Arl13b localizes to focal adhesions in breast cancer cells and interacts with β3-integrin; Arl13b silencing increases β3-integrin cell surface levels and FA size while inhibiting integrin-mediated signaling, revealing a mechanism for Arl13b in regulating cell migration and invasion.","method":"siRNA knockdown, immunofluorescence localization to focal adhesions, Co-immunoprecipitation with β3-integrin, flow cytometry for surface integrin, in vitro migration/invasion assays, in vivo mouse orthotopic model","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional localization and in vivo data, single lab","pmids":["31569511"],"is_preprint":false},{"year":2020,"finding":"ARL13B's role within cilia can be uncoupled from its function outside of cilia; a cilia-excluded ARL13B variant (V358A) that retains all known biochemical activities (GEF for ARL3, etc.) results in normal Shh signal transduction but short cilia lacking ciliary ARL3 and INPP5E, demonstrating that ARL13B's Shh-regulatory function is primarily extraciliary.","method":"Knock-in mouse model (V358A cilia-excluded allele), immunofluorescence, Shh pathway readouts, retrograde transport blockade experiments","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — engineered knock-in allele with retention of biochemical activity but loss of ciliary localization, rigorous in vivo phenotyping","pmids":["32129762"],"is_preprint":false},{"year":2022,"finding":"ARL13B interacts with VEGFR2 (by GST-fusion protein-protein interaction and Co-IP), and regulates membrane and ciliary localization of VEGFR2, thereby activating its downstream signaling in endothelial cells. Additionally, ARL13B enhances VEGFA expression by activating Hedgehog signaling in glioma cells; this is transcriptionally regulated by ZEB1.","method":"GST-pulldown, Co-immunoprecipitation, immunofluorescence, dual-luciferase reporter assay, endothelial conditional KO/OE mouse models","journal":"Neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction assays plus functional localization and signaling data, single lab","pmids":["36322624"],"is_preprint":false},{"year":2023,"finding":"TULP3's tubby domain interacts with the N-terminal amphipathic helix of ARL13B (a ciliary localization sequence) to mediate ciliary trafficking of ARL13B, independently of palmitoylation. This requires TULP3 binding to IFT-A but not phosphoinositides. TULP3-mediated ARL13B trafficking also controls ciliary enrichment of downstream farnesylated and myristoylated effectors.","method":"TULP3-knockout cells, rescue with mutants, domain mapping, immunofluorescence, biochemical interaction assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic mutant rescue dissecting specific domains required for interaction, multiple conditions tested, mechanistic pathway established","pmids":["36652335"],"is_preprint":false},{"year":2023,"finding":"Rab8-GDP (but not Rab8-GTP) and TNPO1 simultaneously and directly bind to the C-terminal 17-amino acid ciliary targeting sequence (CTS) of Arl13b containing the RVEP motif; Rab8-GDP enhances the TNPO1-CTS interaction. The RVEP motif is essential for these interactions, and knockdown of Rab8 or TNPO1 decreases ciliary localization of endogenous Arl13b.","method":"Pulldown assays with cell lysates and purified recombinant proteins, TurboID-based proximity ligation, truncation/point mutation mapping, RNAi knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — reconstitution with purified proteins plus cellular validation with RNAi, multiple orthogonal methods","pmids":["36907439"],"is_preprint":false},{"year":2025,"finding":"Ciliary ARL13B is essential for body weight regulation in adult mice; cilia-excluded ARL13B (V358A) mice are hyperphagic, obese, and insulin resistant. ARL13B's ARL3 GEF activity is not required for body weight regulation. Induced re-expression of wild-type ARL13B (which localizes to cilia) in 4-week-old obese mice rescues obesity and metabolic impairments, indicating a role in adult homeostatic signaling within cilia.","method":"Knock-in mouse models (V358A cilia-excluded, R79Q GEF-deficient), conditional inducible re-expression, metabolic phenotyping (body weight, insulin resistance, hyperphagia)","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 2 / Moderate — two distinct engineered alleles with clear in vivo metabolic phenotype and rescue experiment, single lab but rigorous design","pmids":["37577625"],"is_preprint":true},{"year":2025,"finding":"Ciliary ARL13B and its ARL3 GEF activity are required for Pkd1-dependent renal cystogenesis; loss of ciliary ARL13B (V358A) or mutation of the ARL3 GEF-critical residue (R79Q) suppresses Pkd1-dependent cysts, reducing kidney size, cystic index, BUN, renal fibrosis, injury markers, and β-catenin/cyclin D1 levels.","method":"Two distinct Arl13b knock-in alleles crossed with Pkd1-deficient adult mouse model, histology, BUN measurements, fibrosis staining, immunofluorescence, Western blotting","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two distinct alleles in disease model with multiple readouts, single lab, preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"Ciliary ARL13B is required for cone photoreceptor function and outer segment morphology; the cilia-excluded V358A variant causes early loss of cone-mediated vision followed by rod vision decline, shortened cone axonemes, structural cone outer segment abnormalities, mislocalization of IFT88 and TULP1 in photoreceptors. The GEF-impaired R79Q variant does not cause similar photoreceptor functional changes.","method":"Knock-in mouse models (V358A and R79Q), ERG, immunohistochemistry, transmission electron microscopy","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — two distinct knock-in alleles with ERG, ultrastructural, and protein localization analyses dissecting ciliary vs. GEF function","pmids":["40721319"],"is_preprint":false},{"year":2025,"finding":"ARL13B males rescued from embryonic lethality by ARL13B-Cerulean fail to sire offspring, revealing a role for ARL13B in spermatogenesis.","method":"Conditional knock-in rescue mouse model (Arl13bhnn/hnn expressing ARL13B-Cerulean), breeding assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — defined phenotypic readout from genetic rescue model, single lab, single method","pmids":["40916698"],"is_preprint":false},{"year":2025,"finding":"Complete ARL13B knockout abolishes primary ciliogenesis entirely (not just shortens cilia) in multiple cell lines, and also abolishes cellular response to SMO-mediated Hedgehog stimulation. Multiple regions of ARL13B are necessary for rescue.","method":"CRISPR/Cas9 knockout cell lines, immunofluorescence for cilia, Hedgehog stimulation assays, rescue with truncation mutants","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with rescue experiments, multiple cell lines tested, single lab","pmids":["40707593"],"is_preprint":false},{"year":2025,"finding":"PRPF8 regulates alternative splicing of ARL13B; loss of PRPF8 increases expression of an ARL13B isoform lacking exon 9. Overexpression of the exon-9-lacking ARL13B isoform in zebrafish perturbs cilium formation and causes laterality defects. The shorter ARL13B isoform lacks interactions with intraflagellar transport proteins.","method":"Mouse and zebrafish mutant analysis, RNA splicing assays, zebrafish overexpression of alternative isoform, protein interaction studies","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — splicing regulation demonstrated biochemically plus functional overexpression in zebrafish with interaction data, preprint","pmids":["40501629"],"is_preprint":true},{"year":2018,"finding":"ARL13B localizes to the ciliary membrane and is required in the photoreceptor connecting cilium; loss of ARL13B disrupts proper basal body docking at inner segments and prevents photoreceptor outer segment disc formation (established by conditional KO).","method":"Conditional knockout mice, electron microscopy, immunofluorescence","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent conditional mouse models with ultrastructural analysis, already incorporated into PMID 30573647 discovery above","pmids":["30573647"],"is_preprint":false},{"year":2012,"finding":"Arl13b is required non-autonomously for BMP signaling and Wnt ligand expression in the dorsal neural tube; dorsal patterning defects in Arl13b(hnn) mutants result from abnormal Shh signaling environment that indirectly disrupts BMP signaling, while downstream Wnt signaling remains normal.","method":"Mouse mutant analysis (Arl13b(hnn)), in situ hybridization, immunofluorescence for BMP/Wnt pathway components","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis via genetic mutant showing non-autonomous pathway relationship, single lab","pmids":["21539826"],"is_preprint":false},{"year":2012,"finding":"ARL13B (via its effect on Gli activator/repressor balance) controls a critical period of neural tube patterning before E10.5; temporal deletion experiments show that improperly patterned cells recover to wild-type pattern by E12.5, and this recovery requires Gli3 (the primary Gli repressor), establishing ARL13B as an uncoupler of GliA and GliR regulation.","method":"Conditional/temporal deletion of Arl13b in mouse, genetic epistasis with Gli3, neural tube patterning assays","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — temporal conditional deletion plus epistasis with Gli3, single lab","pmids":["23014696"],"is_preprint":false},{"year":2022,"finding":"PAK2 signaling in zebrafish regulates ARL13B expression and ciliogenesis in brain endothelial cells; overexpression of ARL13B-GFP rescues cilia numbers and cerebral hemorrhage in pak2a (redhead) mutants. In primary human brain microvascular ECs, PDGF-BB and VEGF-A trigger PAK2-ARL13B ciliogenesis signaling through VEGFR-2.","method":"Zebrafish genetic model, mRNA overexpression rescue, primary EC culture, biochemical signaling assays","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo rescue plus in vitro signaling pathway, single lab, two orthogonal systems","pmids":["35700757"],"is_preprint":false}],"current_model":"ARL13B is an atypical ciliary GTPase and guanine nucleotide exchange factor (GEF) for ARL3 that localizes to the ciliary membrane via palmitoylation and a C-terminal RVEP ciliary targeting sequence (transported by TULP3/IFT-A and Rab8/TNPO1 adaptors); within cilia it regulates Smoothened and GPR161 ciliary trafficking, controls IFT-A-mediated retrograde protein exit, promotes INPP5E ciliary targeting, interacts with tubulin to anchor membrane proteins along the axoneme, drives axoneme polyglutamylation via RAB11-FIP5-TTLL5/6 trafficking, and activates ARL3·GTP to release lipidated cargo—while outside cilia it regulates endocytic recycling, actin-dependent cell migration via Myh9 and integrin signaling, and Shh-mediated axon guidance, with its ciliary GEF activity required for Pkd1-dependent renal cystogenesis and body weight homeostasis."},"narrative":{"mechanistic_narrative":"ARL13B is an atypical, ciliary-membrane-anchored small GTPase of the ARF/ARL family that organizes the protein composition and signaling output of the primary cilium [PMID:18674751, PMID:20231383, PMID:24168557]. Its structure carries an incomplete active site that abolishes intrinsic GTP hydrolysis, and biochemically it acts principally as a guanine nucleotide exchange factor (GEF) for ARL3, generating a spatially restricted ARL3·GTP compartment within cilia that drives release of lipidated ciliary cargo [PMID:24168557, PMID:26551564, PMID:28487361]. Membrane targeting depends on N-terminal palmitoylation—which also stabilizes the protein—and a C-terminal RVEP/RVVP ciliary-targeting sequence, with ciliary delivery mediated by TULP3/IFT-A and by a Rab8-GDP/TNPO1 import system; AHI1 promotes its ciliary recruitment and proteasomal stability [PMID:28848045, PMID:36652335, PMID:36907439, PMID:24339792, PMID:31391239]. Within cilia, ARL13B controls trafficking and dynamic distribution of signaling receptors including Smoothened and GPR161, promotes ciliary targeting of INPP5E, binds tubulin through its G-domain to anchor membrane proteins along the axoneme, and directs axoneme polyglutamylation via a RAB11-FIP5–dependent import of TTLL5/6 glutamylases—together enabling Sonic hedgehog signal transduction [PMID:21976698, PMID:27927754, PMID:23150559, PMID:30120249, PMID:40707593]. Engineered cilia-excluded (V358A) and GEF-deficient (R79Q) alleles separate these activities, showing that Shh regulation is largely extraciliary while ciliary ARL13B and its ARL3 GEF activity are required for Pkd1-dependent renal cystogenesis, and ciliary ARL13B governs body-weight homeostasis and photoreceptor outer-segment function [PMID:32129762, PMID:37577625, PMID:40721319, PMID:30573647]. Beyond cilia ARL13B operates in endocytic recycling and in actin- and integrin-dependent cell migration through interactions with Myh9 and β3-integrin [PMID:23223633, PMID:24777479, PMID:31569511]. Missense mutations that disrupt the ARL13B–INPP5E interaction or impair ARL3 GEF activity cause Joubert syndrome [PMID:23150559, PMID:29255182].","teleology":[{"year":2008,"claim":"Established that ARL13B is a bona fide ciliary protein whose function is evolutionarily conserved and disease-relevant, anchoring all subsequent mechanistic work.","evidence":"Zebrafish rescue with wild-type versus patient-mutant ARL13B and immunolocalization in murine neurons","pmids":["18674751"],"confidence":"High","gaps":["Did not define the molecular activity of ARL13B","No partners or substrates identified"]},{"year":2010,"claim":"Defined how ARL13B reaches and acts at the cilium, linking membrane anchoring to maintenance of ciliary ultrastructure, transmembrane protein content, and IFT stability.","evidence":"C. elegans genetics, IFT motility assays, and epistasis with ciliogenic/IFT genes","pmids":["20231383"],"confidence":"High","gaps":["Palmitoylation inferred from motifs, not yet demonstrated biochemically","Direct IFT-complex partners not yet mapped"]},{"year":2009,"claim":"Showed that correct ciliary localization is necessary for in vivo function, framing ARL13B targeting as a mechanistic requirement rather than a passive marker.","evidence":"Systematic deletion/point-mutant rescue in arl13b/scorpion zebrafish","pmids":["19906870"],"confidence":"High","gaps":["Targeting sequences not yet molecularly resolved","Did not separate ciliary from extraciliary roles"]},{"year":2011,"claim":"Connected ARL13B to Sonic hedgehog signaling by showing it controls dynamic Smoothened distribution in cilia.","evidence":"Smo immunofluorescence in Arl13b-null versus wild-type cilia under Shh stimulation","pmids":["21976698"],"confidence":"High","gaps":["Mechanism of Smo control (direct vs indirect) not resolved","Did not address other Hh-pathway receptors"]},{"year":2012,"claim":"Identified ARL13B as a hub for ciliary lipid-signaling by demonstrating a direct INPP5E interaction required for INPP5E ciliary targeting, with Joubert mutations disrupting this link.","evidence":"Co-IP/binding assays, ciliary localization, and patient mutation analysis defining an ARL13B-INPP5E-PDE6D-CEP164 network","pmids":["23150559"],"confidence":"High","gaps":["GEF activity toward ARL3 not yet established","Mechanism coupling INPP5E import to downstream signaling unresolved"]},{"year":2012,"claim":"Extended ARL13B function to neuronal cilia, showing it controls guidance-receptor dynamics needed for interneuron migration and placement.","evidence":"Conditional knockout mice, live imaging of interneuronal cilia, guidance-receptor immunofluorescence","pmids":["23153492"],"confidence":"High","gaps":["Specific receptors mechanistically regulated not fully defined","Cilia-dependence versus extraciliary contribution not separated"]},{"year":2012,"claim":"Revealed an extraciliary role in endocytic recycling, indicating ARL13B function is not confined to the cilium.","evidence":"shRNA knockdown, CD1a surface/recycling flow cytometry, endosome morphology, colocalization with Arf6/Rab22a","pmids":["23223633"],"confidence":"Medium","gaps":["Direct effectors in recycling pathway not identified","Single lab; mechanism of endosome clustering unresolved"]},{"year":2012,"claim":"Placed ARL13B within neural-tube patterning logic, showing it uncouples Gli activator/repressor balance during a defined critical period and acts non-autonomously on BMP signaling.","evidence":"Temporal/conditional Arl13b deletion, Gli3 epistasis, in situ hybridization for BMP/Wnt components","pmids":["23014696","21539826"],"confidence":"Medium","gaps":["Molecular mechanism linking ARL13B to GliA/GliR ratio unresolved","Non-autonomous BMP effect mechanistically indirect"]},{"year":2013,"claim":"Defined the subciliary compartmentalization of ARL13B and its requirement for an RVVP motif and membrane anchoring, while mapping IFT-B associations and IFT-like motility.","evidence":"C. elegans genetics across >20 mutants, in vivo FRAP, and mass-spectrometry interactome (IFT46, IFT74)","pmids":["24339792"],"confidence":"High","gaps":["Functional importance of IFT-B binding versus localization not separated here","Human relevance of compartment boundaries not tested"]},{"year":2014,"claim":"Established a structural basis for ARL13B's atypical biochemistry, showing an incomplete active site explains absent intrinsic hydrolysis and that patient mutations destabilize key conformational residues.","evidence":"X-ray crystallography of Chlamydomonas Arl13B with biochemical GTPase assays and mutant analysis","pmids":["24168557"],"confidence":"High","gaps":["No human full-length structure","Catalytic partner (GEF target) not yet identified structurally"]},{"year":2014,"claim":"Showed ARL13B directly binds tubulin via its G-domain independently of GTPase activity to anchor ciliary membrane proteins uniformly along the axoneme.","evidence":"Co-IP, in vitro binding, structure-function mutagenesis, and rescue of null MEF ciliogenesis defects","pmids":["29592971"],"confidence":"High","gaps":["Tubulin-binding interface not mapped at residue level","How anchoring couples to signaling output unresolved"]},{"year":2014,"claim":"Linked ARL13B GTPase activity to ciliary membrane extension and placed it downstream of ciliogenic transcription factors FoxJ1/Rfx.","evidence":"Zebrafish and mammalian overexpression/loss-of-function with GTPase-dead variants","pmids":["25448689"],"confidence":"Medium","gaps":["Mechanism of membrane protrusion not defined","Single lab; relationship to GEF activity unaddressed"]},{"year":2014,"claim":"Uncovered extraciliary migration functions through GTP-dependent exocyst binding and a Myh9-dependent role in circular dorsal ruffles.","evidence":"GTP/GDP pulldowns, direct binding to Sec8/Sec5, Co-IP with Myh9, RNAi, and zebrafish neural-crest migration assays","pmids":["26582389","24777479"],"confidence":"Medium","gaps":["Whether exocyst binding operates at cilia or elsewhere not resolved","Direct versus indirect Myh9 effect on migration unresolved"]},{"year":2015,"claim":"Defined ARL13B's central enzymatic identity as the GEF for ARL3, establishing that it spatially restricts ARL3·GTP to cilia to license cargo release, with Joubert mutations impairing this activity.","evidence":"In vitro GEF reconstitution, structural analysis, mammalian overexpression, and patient mutation testing","pmids":["26551564"],"confidence":"High","gaps":["Full set of lipidated cargoes released downstream not enumerated","In vivo requirement of GEF activity not yet tested by knock-in"]},{"year":2017,"claim":"Consolidated the atypical GTPase/GEF biochemistry with purified protein and identified casein kinase 2 phosphorylation as a regulatory modification.","evidence":"Recombinant murine Arl13b nucleotide-binding, GTPase, and GEF assays plus mutation characterization","pmids":["28487361"],"confidence":"High","gaps":["Functional consequence of CK2 phosphorylation not defined","Regulation of GEF activity in vivo unresolved"]},{"year":2017,"claim":"Established palmitoylation as the in vivo determinant of ciliary trafficking, stability, and function, distinguishing localization from function.","evidence":"Biochemical palmitoylation assays in mouse kidney, myristoylation substitution, stability and rescue experiments","pmids":["28848045"],"confidence":"High","gaps":["Palmitoyltransferase/thioesterase enzymes not identified","How palmitoylation supports function beyond localization unresolved"]},{"year":2016,"claim":"Resolved the order of trafficking determinants, showing ciliary localization depends on the RVEP CTS and that INPP5E binding—not IFT-B binding—drives IFT-A-mediated retrograde GPR161 exit.","evidence":"Visible immunoprecipitation, ARL13B-knockout cells, and rescue with interaction-specific mutants","pmids":["27927754"],"confidence":"High","gaps":["Precise step at which retrograde exit fails not defined","Mechanistic coupling of INPP5E to IFT-A machinery unresolved"]},{"year":2017,"claim":"Implicated ARL13B-Smo interaction in cancer Hedgehog signaling via control of Smo stability and trafficking.","evidence":"Co-IP, trafficking assays, tumor proliferation/invasion assays, and in vivo gastric cancer models","pmids":["28611043"],"confidence":"Medium","gaps":["Direct versus indirect Smo binding not biochemically resolved","Single disease context"]},{"year":2018,"claim":"Connected ARL13B to axoneme tubulin polyglutamylation through RAB11-FIP5-dependent import of TTLL5/6 glutamylases, mechanistically linking it to sensory receptor anchoring.","evidence":"Co-IP for ARL13B-FIP5, TTLL5/6 localization, and CCP5-depletion rescue of hypoglutamylation","pmids":["30120249"],"confidence":"High","gaps":["Whether GEF or GTPase activity is required for this trafficking unresolved","Direct glutamylase recruitment mechanism not fully defined"]},{"year":2018,"claim":"Identified TULP3 as a trafficking adaptor that delivers ARL13B (and INPP5E) to cilia via IFT-A binding, with TUB redundancy.","evidence":"TULP3-knockout RPE1 cells rescued with wild-type and IFT-A-binding-deficient TULP3","pmids":["30583862"],"confidence":"Medium","gaps":["Relationship to palmitoylation-dependent targeting not resolved here","Single lab"]},{"year":2018,"claim":"Established ARL13B as essential across retinogenesis stages and for photoreceptor outer-segment morphogenesis and protein trafficking.","evidence":"Pan-retina and inducible conditional knockout mice with ERG, immunofluorescence, and electron microscopy","pmids":["30573647"],"confidence":"High","gaps":["Ciliary versus GEF contributions not separated in this study","Specific cargo-trafficking step disrupted not fully defined"]},{"year":2018,"claim":"Tied loss of ARL3 GEF activity directly to Joubert syndrome through a patient variant that selectively abolishes GEF function while preserving GTPase and rescue capacity.","evidence":"Whole-exome sequencing plus GEF, cilia-length, and Shh rescue assays for the Gly75Arg variant","pmids":["29255182"],"confidence":"High","gaps":["Which downstream cargo defect causes disease not pinpointed","Genotype-phenotype breadth across patients not addressed"]},{"year":2019,"claim":"Demonstrated a cilia-independent ARL13B function in Shh-mediated axon guidance, with a cilia-excluded variant sufficient for guidance.","evidence":"Conditional knockout, in vitro axon guidance assays, and cilia-excluded variant rescue","pmids":["31825820"],"confidence":"High","gaps":["Molecular effectors of axonal ARL13B not identified","How extraciliary ARL13B transduces Shh locally unresolved"]},{"year":2019,"claim":"Identified AHI1 as a regulator of ARL13B ciliary recruitment and proteasomal stability, affecting Shh signaling and motility.","evidence":"Ahi1-knockout MEFs with localization, proteasome-inhibition stability assays, Shh readouts, and migration assays","pmids":["31391239"],"confidence":"Medium","gaps":["Whether AHI1 acts directly on ARL13B unresolved","E3 ligase controlling degradation not identified"]},{"year":2019,"claim":"Defined an extraciliary migration mechanism through focal-adhesion localization and β3-integrin interaction controlling surface integrin and adhesion dynamics.","evidence":"siRNA, focal-adhesion immunofluorescence, Co-IP with β3-integrin, surface flow cytometry, and orthotopic breast cancer model","pmids":["31569511"],"confidence":"Medium","gaps":["Nucleotide-state dependence of integrin binding not defined","Single lab"]},{"year":2020,"claim":"Genetically uncoupled ciliary from extraciliary ARL13B, showing the V358A cilia-excluded allele supports normal Shh signaling despite short cilia lacking ARL3 and INPP5E—establishing Shh regulation as primarily extraciliary.","evidence":"V358A knock-in mouse with Shh readouts and retrograde-transport blockade experiments","pmids":["32129762"],"confidence":"High","gaps":["Where extraciliary Shh transduction occurs spatially not resolved","Mechanism of short cilia in V358A not fully defined"]},{"year":2022,"claim":"Linked ARL13B to vascular signaling via VEGFR2 interaction and localization control, and to PAK2-driven ciliogenesis in brain endothelium.","evidence":"GST-pulldown, Co-IP, luciferase reporters, endothelial mouse models, and zebrafish pak2a rescue","pmids":["36322624","35700757"],"confidence":"Medium","gaps":["Direct versus indirect VEGFR2 regulation not fully resolved","Single lab per context"]},{"year":2023,"claim":"Mapped the molecular logic of ARL13B ciliary import, defining a TULP3-tubby/N-terminal amphipathic helix route and a Rab8-GDP/TNPO1 system recognizing the RVEP CTS.","evidence":"Domain mapping with knockout rescue, purified-protein pulldowns, TurboID proximity labeling, and RNAi","pmids":["36652335","36907439"],"confidence":"High","gaps":["Hand-off between palmitoylation, TULP3, and Rab8/TNPO1 routes not integrated","Regulation of Rab8 nucleotide state in this context unresolved"]},{"year":2025,"claim":"Dissected in vivo physiological requirements using V358A and R79Q alleles, showing ciliary ARL13B is required for body-weight homeostasis (GEF-independent) and that ciliary localization plus GEF activity are required for Pkd1-dependent renal cystogenesis.","evidence":"Knock-in mouse models with inducible re-expression, metabolic phenotyping, and Pkd1-cross cystogenesis readouts","pmids":["37577625"],"confidence":"High","gaps":["Cyst study is a preprint without listed PMID","Downstream ciliary signal mediating weight control not identified"]},{"year":2025,"claim":"Further separated ciliary from GEF activity in photoreceptors and revealed roles in spermatogenesis and absolute ciliogenesis, while connecting splicing regulation to ARL13B isoform function.","evidence":"V358A/R79Q knock-in ERG/EM analyses, CRISPR knockouts, rescue breeding, and PRPF8-dependent splicing with zebrafish isoform overexpression","pmids":["40721319","40707593","40916698","40501629"],"confidence":"Medium","gaps":["Mechanism of spermatogenesis role undefined","Functional role of exon-9-lacking isoform partly preprint-stage"]},{"year":null,"claim":"How ARL13B's distinct biochemical activities (ARL3 GEF, tubulin binding, atypical GTP binding) are individually deployed across its many ciliary and extraciliary functions, and which downstream effectors transduce each, remains incompletely resolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking nucleotide state to specific cargo decisions","Extraciliary Shh transduction mechanism unknown","Enzymes controlling palmitoylation cycle and degradation unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[12,15,18]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[12,15]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,14,19]},{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[11,15]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,1,3,7,16,35]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[16,24,26]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[6,10]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,12,17,25]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[6,13,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,22,36,37]},{"term_id":"R-HSA-9609507","term_label":"Protein 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May regulate ARF6- and RAB22A-dependent endocytic recycling traffic (PubMed:23223633)","subcellular_location":"Cell projection, cilium membrane; Cell projection, cilium; Cell membrane; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q3SXY8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARL13B","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000169379","cell_line_id":"CID000485","localizations":[{"compartment":"centrosome","grade":3}],"interactors":[{"gene":"GEMIN4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000485","total_profiled":1310},"omim":[{"mim_id":"620866","title":"GLUTAMATE-RICH PROTEIN 3; ERICH3","url":"https://www.omim.org/entry/620866"},{"mim_id":"619849","title":"CHOLESTASIS, PROGRESSIVE FAMILIAL INTRAHEPATIC, 9; PFIC9","url":"https://www.omim.org/entry/619849"},{"mim_id":"619635","title":"ZINC FINGER FYVE DOMAIN-CONTAINING PROTEIN 19; ZFYVE19","url":"https://www.omim.org/entry/619635"},{"mim_id":"619306","title":"NEURODEVELOPMENTAL DISORDER WITH DYSMORPHIC FACIES AND CEREBELLAR HYPOPLASIA; NEDFACH","url":"https://www.omim.org/entry/619306"},{"mim_id":"618161","title":"JOUBERT SYNDROME 35; JBTS35","url":"https://www.omim.org/entry/618161"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Microtubules","reliability":"Supported"},{"location":"Primary cilium","reliability":"Supported"},{"location":"Primary cilium transition zone","reliability":"Supported"},{"location":"Cytokinetic bridge","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"},{"location":"Acrosome","reliability":"Additional"},{"location":"Equatorial segment","reliability":"Additional"},{"location":"Mid 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many","driving_tissues":[{"tissue":"retina","ntpm":16.8}],"url":"https://www.proteinatlas.org/search/ARL13B"},"hgnc":{"alias_symbol":["DKFZp761H079","JBTS8"],"prev_symbol":["ARL2L1"]},"alphafold":{"accession":"Q3SXY8","domains":[{"cath_id":"3.40.50.300","chopping":"17-196","consensus_level":"high","plddt":95.2424,"start":17,"end":196}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q3SXY8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q3SXY8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q3SXY8-F1-predicted_aligned_error_v6.png","plddt_mean":72.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARL13B","jax_strain_url":"https://www.jax.org/strain/search?query=ARL13B"},"sequence":{"accession":"Q3SXY8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q3SXY8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q3SXY8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q3SXY8"}},"corpus_meta":[{"pmid":"18674751","id":"PMC_18674751","title":"Mutations 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overexpression of human wild-type but not patient mutant ARL13B rescued the Arl13b scorpion zebrafish mutant, establishing evolutionary conservation of its ciliary role.\",\n      \"method\": \"Zebrafish rescue experiments, immunofluorescence localization in murine neurons\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct rescue assays in zebrafish with wild-type vs. patient mutant, replicated across species contexts\",\n      \"pmids\": [\"18674751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"C. elegans ARL-13/Arl13b localizes to proximal ciliary membranes via palmitoylation modification motifs; loss-of-function causes defects in cilium morphology/ultrastructure, abnormal accumulation of ciliary transmembrane proteins, elevated PKD-2 ciliary abundance, and destabilized anterograde intraflagellar transport (IFT). Genetic interaction with other ciliogenic/IFT genes confirmed its role in anterograde IFT stability.\",\n      \"method\": \"C. elegans genetics, fluorescence microscopy, IFT motility assays, genetic epistasis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (localization, ultrastructure, IFT assays, epistasis) in a single rigorous study\",\n      \"pmids\": [\"20231383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Multiple regions of Arl13b are required for its ciliary localization, and ciliary localization is essential for in vivo function; ciliary-localization-defective mutants cannot rescue arl13b/scorpion zebrafish phenotypes.\",\n      \"method\": \"Zebrafish rescue experiments with deletion and point mutants\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic mutagenesis rescue assay with multiple mutant variants in vivo\",\n      \"pmids\": [\"19906870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Arl13b regulates the ciliary entry and distribution of Smoothened (Smo); in Arl13b-null cilia, Smo is enriched regardless of Shh pathway stimulation, indicating Arl13b controls the dynamic localization of Smo within the cilium and thereby regulates Sonic hedgehog signaling.\",\n      \"method\": \"Mouse mutant analysis, immunofluorescence of Smo localization in Arl13b-null vs. wild-type cilia in vitro\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative localization in knockout cells and embryos with stimulation conditions, multiple orthogonal approaches\",\n      \"pmids\": [\"21976698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ARL13B physically interacts with INPP5E and is required for ciliary targeting of INPP5E; JBTS-causing missense mutations in ARL13B disrupt the ARL13B-INPP5E interaction. ARL13B, INPP5E, PDE6D, and CEP164 form a distinct functional network for INPP5E ciliary targeting.\",\n      \"method\": \"Protein-protein interaction studies (Co-IP, binding assays), cell-based localization, patient mutation analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction studies combined with patient mutation functional testing and rescue experiments\",\n      \"pmids\": [\"23150559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Arl13b is required in primary cilia for proper migration and placement of interneurons in the developing cerebral cortex; guidance cue receptors essential for interneuronal migration localize to interneuronal primary cilia, but their concentration and dynamics are altered in the absence of Arl13b.\",\n      \"method\": \"Live imaging of interneuronal cilia, mouse conditional knockout, immunofluorescence of guidance receptors\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging combined with knockout mouse model and receptor localization analysis\",\n      \"pmids\": [\"23153492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Arl13b is required for endocytic recycling traffic; silencing Arl13b reduces CD1a surface expression and delays CD1a recycling, causes clustering of early endosomes and accumulation of endocytic cargo. Arl13b colocalizes with Arf6 and Rab22a (endocytic recycling markers) and interacts with the actin cytoskeleton.\",\n      \"method\": \"shRNA knockdown screen, flow cytometry for CD1a surface expression, fluorescence colocalization, endosome morphology analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined phenotypic readout with colocalization, single lab, multiple approaches\",\n      \"pmids\": [\"23223633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ARL13B/ARL-13 is restricted to an Inv-like subciliary membrane compartment; compartmentalization requires a C-terminal RVVP motif and membrane anchoring. IFT-A/B, IFT-dynein and BBS genes prevent ARL-13 periciliary membrane accumulation; MKS/NPHP modules additionally inhibit ARL-13 at the transition zone. ARL-13 undergoes IFT-like motility and human ARL13B has functional associations with IFT-B complexes via IFT46 and IFT74 interactions.\",\n      \"method\": \"C. elegans genetics (>20 mutants), quantitative fluorescence imaging, in vivo FRAP, quantitative protein complex analysis (mass spectrometry)\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (FRAP, MS interactome, systematic genetics) across species\",\n      \"pmids\": [\"24339792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ARL13B directly interacts with tubulin via its G-domain independently of GTPase activity; this interaction is required for ARL13B to anchor ciliary membrane proteins (Smo, SSTR3) uniformly along the cilium. Mutants lacking the tubulin-binding G-domain fail to rescue ciliogenesis defects of null MEFs and cause uneven distribution of membrane proteins.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assays, mutagenesis, immunofluorescence in MEFs\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct interaction demonstrated in vitro and in vivo with structure-function mutagenesis, single lab\",\n      \"pmids\": [\"29592971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Overexpression of Arl13b increases ciliary length by inducing protrusion of the ciliary membrane followed by axonemal extension; GTPase activity of Arl13b is essential for this membrane extension. Arl13b is induced by ciliogenic transcription factors FoxJ1 and Rfx and acts downstream of them to regulate ciliary length.\",\n      \"method\": \"Zebrafish overexpression and loss-of-function, mammalian cell overexpression, mutant analysis including GTPase-dead variants\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression and mutant rescue in two systems with GTPase-dead variant, single lab\",\n      \"pmids\": [\"25448689\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Arl13b localizes to circular dorsal ruffles (CDRs) and interacts with non-muscle myosin heavy chain IIA (Myh9) as an effector; both proteins are required for CDR formation and cell migration. Arl13b silencing impairs neural crest cell migration in zebrafish.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, fluorescence microscopy of CDRs, zebrafish neural crest migration assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional CDR and migration assays, single lab, two orthogonal methods\",\n      \"pmids\": [\"24777479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structure of Chlamydomonas reinhardtii Arl13B reveals an incomplete active site accounting for absence of intrinsic GTP hydrolysis. Patient mutations R79Q and R200C destabilize important intramolecular interactions; Arg79 is crucial for the GDP/GTP conformational change typical of Arf/Arl proteins.\",\n      \"method\": \"X-ray crystallography, biochemical GTPase assays, structural analysis of patient mutants\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with biochemical validation, single lab but structural-level evidence\",\n      \"pmids\": [\"24168557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Arl13B is the guanine nucleotide exchange factor (GEF) for Arl3; GEF activity is mediated by the G-domain plus an additional C-terminal helix, with switch regions of Arl13B involved in interaction with Arl3. Overexpression of Arl13B increases Arl3·GTP levels in mammalian cells, and Joubert syndrome patient mutations impair GEF activity. This spatial restriction of Arl3 activation to cilia generates an Arl3·GTP compartment for ciliary cargo release.\",\n      \"method\": \"In vitro GEF assay, structural analysis, overexpression in mammalian cells, patient mutation analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical GEF reconstitution plus cellular validation and patient mutation testing, independently confirmed in other studies\",\n      \"pmids\": [\"26551564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The GTP-bound form of Arl13b preferentially binds exocyst subunits Sec8, Exo70, and Sec5 (consistent with the exocyst being an effector); Arl13b binds directly to Sec8 and Sec5. Genetic interaction between arl13b and exocyst subunit sec10 in zebrafish shows synergistic cilia-dependent phenotypes, and Arl13b and the exocyst function in the same ciliogenesis pathway.\",\n      \"method\": \"Pulldown assays (GTP vs. GDP-bound Arl13b), direct binding assays, zebrafish morphant genetic interaction, conditional mouse knockout\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding biochemistry plus in vivo genetic epistasis in two organisms\",\n      \"pmids\": [\"26582389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ARL13B interacts with the IFT46-IFT56 dimer of the IFT-B complex; however, ciliary localization of ARL13B is independent of IFT-B interaction but dependent on the C-terminal RVEP ciliary-targeting sequence. In ARL13B-knockout cells, IFT-A and IFT-B complexes accumulate at ciliary tips and GPR161 cannot exit cilia in response to Smoothened agonist (retrograde exit defect). This abnormal phenotype is rescued by wild-type ARL13B and by an IFT-B-interaction-defective mutant, but not by INPP5E-binding-defective or ciliary-localization-defective mutants, indicating ARL13B regulates IFT-A-mediated retrograde protein trafficking through its interaction with INPP5E.\",\n      \"method\": \"Visible immunoprecipitation assay, ARL13B knockout cells, immunofluorescence, rescue with mutants\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic knockout + rescue with structure-function mutants and direct interaction assay, multiple orthogonal methods\",\n      \"pmids\": [\"27927754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Purified recombinant murine Arl13b is biochemically atypical: it binds GTP with lower intrinsic GTPase activity and functions as a GEF for ARL3. Three human Joubert syndrome missense mutations were biochemically characterized. Murine Arl13b is also a substrate for casein kinase 2 phosphorylation.\",\n      \"method\": \"In vitro biochemical assays (nucleotide binding, intrinsic and GAP-stimulated GTPase, GEF activity), recombinant protein purification, patient mutation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein and mutagenesis, single lab but multiple assays\",\n      \"pmids\": [\"28487361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ARL13B palmitoylation occurs in vivo (mouse kidneys) and is required for trafficking to cilia and for ARL13B function within cilia; palmitoylation dramatically increases ARL13B protein stability. Myristoylation can substitute for palmitoylation in ciliary localization but not ciliary function. Blockade of depalmitoylation slows ARL13B degradation during cilia resorption.\",\n      \"method\": \"Biochemical palmitoylation assays, cellular localization studies, in vivo mouse kidney experiments, stability assays, cilia rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vivo palmitoylation confirmed biochemically, multiple mutants tested, stability and localization linked to function\",\n      \"pmids\": [\"28848045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Arl13b interacts with Smoothened (Smo) and regulates Smo stability, trafficking, and ciliary localization, which are crucial for Hedgehog signaling in gastric cancer.\",\n      \"method\": \"Co-immunoprecipitation, cell-based trafficking assays, proliferation/migration/invasion assays, in vivo tumor models\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional trafficking assays, single lab, two orthogonal methods\",\n      \"pmids\": [\"28611043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A novel ARL13B variant (Gly75Arg) causes Joubert syndrome with a marked loss of ARL3 GEF activity while retaining GTPase activity and cilia/Shh-rescue function, establishing a direct correlation between ARL13B's ARL3 GEF activity loss and Joubert syndrome.\",\n      \"method\": \"Whole-exome sequencing, GEF activity assays, cilia length rescue, Shh signaling rescue in null cells\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — biochemical GEF assay with patient mutation directly compared to wild-type and null controls, multiple functional assays\",\n      \"pmids\": [\"29255182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ARL13B controls axoneme polyglutamylation by interacting with RAB11 effector FIP5 to promote ciliary import of glutamylases TTLL5 and TTLL6. Hypoglutamylation caused by ARL13B deficiency impairs ciliary signaling by disrupting sensory receptor anchoring and signaling molecule trafficking, and can be rescued by depletion of deglutamylase CCP5.\",\n      \"method\": \"Co-immunoprecipitation (ARL13B-FIP5 interaction), immunofluorescence of TTLL5/6 localization, CCP5 depletion rescue, cilia signaling assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct interaction demonstrated by Co-IP plus functional rescue with deglutamylase depletion, multiple orthogonal experiments\",\n      \"pmids\": [\"30120249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TULP3 is required for ciliary localization of membrane-associated proteins ARL13B and INPP5E; this function requires TULP3's ability to bind IFT-A. TUB (another tubby family member) can substitute for TULP3 in rescuing ciliary localization of ARL13B, indicating functional redundancy.\",\n      \"method\": \"TULP3-knockout RPE1 cells, immunofluorescence, rescue with wild-type and IFT-A-binding-deficient TULP3 mutants\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with rescue using specific mutant, single lab, clear phenotypic readout\",\n      \"pmids\": [\"30583862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ARL13B is required at multiple stages of retinogenesis including early retinal progenitor proliferation, photoreceptor cilia development, and outer segment disc morphogenesis. Loss of ARL13B in adult photoreceptors causes mislocalization of rhodopsin, prenylated PDE6, and IFT88, and loss of photoresponse.\",\n      \"method\": \"Conditional knockout mouse models (Six3-Cre pan-retina and Pde6g-CreERT2 inducible), ERG, immunofluorescence, electron microscopy\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent conditional KO models with ultrastructural, functional, and protein trafficking analyses\",\n      \"pmids\": [\"30573647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Arl13b functions outside primary cilia in Shh-mediated axon guidance; Arl13b protein is detected in axons and growth cones, and a cilia-localization-deficient Arl13b variant is sufficient to mediate Shh-dependent commissural axon guidance both in vitro and in vivo.\",\n      \"method\": \"In vivo conditional knockout, in vitro axon guidance assays, immunolocalization in axons/growth cones, cilia-excluded variant rescue\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO with specific guidance phenotype plus cilia-excluded variant rescue, multiple orthogonal methods\",\n      \"pmids\": [\"31825820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"AHI1 promotes Arl13b ciliary recruitment and regulates Arl13b stability via the proteasome; loss of Ahi1 reduces ciliary membrane localization of Arl13b, decreases non-membrane-associated Arl13b stability, reduces Shh signaling, and causes defects in cell motility.\",\n      \"method\": \"Ahi1-knockout MEFs, immunofluorescence, stability assays with proteasome inhibition, Shh signaling readouts, migration assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with multiple functional readouts and stability mechanistic follow-up, single lab\",\n      \"pmids\": [\"31391239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Arl13b localizes to focal adhesions in breast cancer cells and interacts with β3-integrin; Arl13b silencing increases β3-integrin cell surface levels and FA size while inhibiting integrin-mediated signaling, revealing a mechanism for Arl13b in regulating cell migration and invasion.\",\n      \"method\": \"siRNA knockdown, immunofluorescence localization to focal adhesions, Co-immunoprecipitation with β3-integrin, flow cytometry for surface integrin, in vitro migration/invasion assays, in vivo mouse orthotopic model\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional localization and in vivo data, single lab\",\n      \"pmids\": [\"31569511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ARL13B's role within cilia can be uncoupled from its function outside of cilia; a cilia-excluded ARL13B variant (V358A) that retains all known biochemical activities (GEF for ARL3, etc.) results in normal Shh signal transduction but short cilia lacking ciliary ARL3 and INPP5E, demonstrating that ARL13B's Shh-regulatory function is primarily extraciliary.\",\n      \"method\": \"Knock-in mouse model (V358A cilia-excluded allele), immunofluorescence, Shh pathway readouts, retrograde transport blockade experiments\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — engineered knock-in allele with retention of biochemical activity but loss of ciliary localization, rigorous in vivo phenotyping\",\n      \"pmids\": [\"32129762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARL13B interacts with VEGFR2 (by GST-fusion protein-protein interaction and Co-IP), and regulates membrane and ciliary localization of VEGFR2, thereby activating its downstream signaling in endothelial cells. Additionally, ARL13B enhances VEGFA expression by activating Hedgehog signaling in glioma cells; this is transcriptionally regulated by ZEB1.\",\n      \"method\": \"GST-pulldown, Co-immunoprecipitation, immunofluorescence, dual-luciferase reporter assay, endothelial conditional KO/OE mouse models\",\n      \"journal\": \"Neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction assays plus functional localization and signaling data, single lab\",\n      \"pmids\": [\"36322624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TULP3's tubby domain interacts with the N-terminal amphipathic helix of ARL13B (a ciliary localization sequence) to mediate ciliary trafficking of ARL13B, independently of palmitoylation. This requires TULP3 binding to IFT-A but not phosphoinositides. TULP3-mediated ARL13B trafficking also controls ciliary enrichment of downstream farnesylated and myristoylated effectors.\",\n      \"method\": \"TULP3-knockout cells, rescue with mutants, domain mapping, immunofluorescence, biochemical interaction assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic mutant rescue dissecting specific domains required for interaction, multiple conditions tested, mechanistic pathway established\",\n      \"pmids\": [\"36652335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Rab8-GDP (but not Rab8-GTP) and TNPO1 simultaneously and directly bind to the C-terminal 17-amino acid ciliary targeting sequence (CTS) of Arl13b containing the RVEP motif; Rab8-GDP enhances the TNPO1-CTS interaction. The RVEP motif is essential for these interactions, and knockdown of Rab8 or TNPO1 decreases ciliary localization of endogenous Arl13b.\",\n      \"method\": \"Pulldown assays with cell lysates and purified recombinant proteins, TurboID-based proximity ligation, truncation/point mutation mapping, RNAi knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — reconstitution with purified proteins plus cellular validation with RNAi, multiple orthogonal methods\",\n      \"pmids\": [\"36907439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Ciliary ARL13B is essential for body weight regulation in adult mice; cilia-excluded ARL13B (V358A) mice are hyperphagic, obese, and insulin resistant. ARL13B's ARL3 GEF activity is not required for body weight regulation. Induced re-expression of wild-type ARL13B (which localizes to cilia) in 4-week-old obese mice rescues obesity and metabolic impairments, indicating a role in adult homeostatic signaling within cilia.\",\n      \"method\": \"Knock-in mouse models (V358A cilia-excluded, R79Q GEF-deficient), conditional inducible re-expression, metabolic phenotyping (body weight, insulin resistance, hyperphagia)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two distinct engineered alleles with clear in vivo metabolic phenotype and rescue experiment, single lab but rigorous design\",\n      \"pmids\": [\"37577625\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Ciliary ARL13B and its ARL3 GEF activity are required for Pkd1-dependent renal cystogenesis; loss of ciliary ARL13B (V358A) or mutation of the ARL3 GEF-critical residue (R79Q) suppresses Pkd1-dependent cysts, reducing kidney size, cystic index, BUN, renal fibrosis, injury markers, and β-catenin/cyclin D1 levels.\",\n      \"method\": \"Two distinct Arl13b knock-in alleles crossed with Pkd1-deficient adult mouse model, histology, BUN measurements, fibrosis staining, immunofluorescence, Western blotting\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two distinct alleles in disease model with multiple readouts, single lab, preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Ciliary ARL13B is required for cone photoreceptor function and outer segment morphology; the cilia-excluded V358A variant causes early loss of cone-mediated vision followed by rod vision decline, shortened cone axonemes, structural cone outer segment abnormalities, mislocalization of IFT88 and TULP1 in photoreceptors. The GEF-impaired R79Q variant does not cause similar photoreceptor functional changes.\",\n      \"method\": \"Knock-in mouse models (V358A and R79Q), ERG, immunohistochemistry, transmission electron microscopy\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two distinct knock-in alleles with ERG, ultrastructural, and protein localization analyses dissecting ciliary vs. GEF function\",\n      \"pmids\": [\"40721319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARL13B males rescued from embryonic lethality by ARL13B-Cerulean fail to sire offspring, revealing a role for ARL13B in spermatogenesis.\",\n      \"method\": \"Conditional knock-in rescue mouse model (Arl13bhnn/hnn expressing ARL13B-Cerulean), breeding assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — defined phenotypic readout from genetic rescue model, single lab, single method\",\n      \"pmids\": [\"40916698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Complete ARL13B knockout abolishes primary ciliogenesis entirely (not just shortens cilia) in multiple cell lines, and also abolishes cellular response to SMO-mediated Hedgehog stimulation. Multiple regions of ARL13B are necessary for rescue.\",\n      \"method\": \"CRISPR/Cas9 knockout cell lines, immunofluorescence for cilia, Hedgehog stimulation assays, rescue with truncation mutants\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with rescue experiments, multiple cell lines tested, single lab\",\n      \"pmids\": [\"40707593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRPF8 regulates alternative splicing of ARL13B; loss of PRPF8 increases expression of an ARL13B isoform lacking exon 9. Overexpression of the exon-9-lacking ARL13B isoform in zebrafish perturbs cilium formation and causes laterality defects. The shorter ARL13B isoform lacks interactions with intraflagellar transport proteins.\",\n      \"method\": \"Mouse and zebrafish mutant analysis, RNA splicing assays, zebrafish overexpression of alternative isoform, protein interaction studies\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — splicing regulation demonstrated biochemically plus functional overexpression in zebrafish with interaction data, preprint\",\n      \"pmids\": [\"40501629\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ARL13B localizes to the ciliary membrane and is required in the photoreceptor connecting cilium; loss of ARL13B disrupts proper basal body docking at inner segments and prevents photoreceptor outer segment disc formation (established by conditional KO).\",\n      \"method\": \"Conditional knockout mice, electron microscopy, immunofluorescence\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent conditional mouse models with ultrastructural analysis, already incorporated into PMID 30573647 discovery above\",\n      \"pmids\": [\"30573647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Arl13b is required non-autonomously for BMP signaling and Wnt ligand expression in the dorsal neural tube; dorsal patterning defects in Arl13b(hnn) mutants result from abnormal Shh signaling environment that indirectly disrupts BMP signaling, while downstream Wnt signaling remains normal.\",\n      \"method\": \"Mouse mutant analysis (Arl13b(hnn)), in situ hybridization, immunofluorescence for BMP/Wnt pathway components\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis via genetic mutant showing non-autonomous pathway relationship, single lab\",\n      \"pmids\": [\"21539826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ARL13B (via its effect on Gli activator/repressor balance) controls a critical period of neural tube patterning before E10.5; temporal deletion experiments show that improperly patterned cells recover to wild-type pattern by E12.5, and this recovery requires Gli3 (the primary Gli repressor), establishing ARL13B as an uncoupler of GliA and GliR regulation.\",\n      \"method\": \"Conditional/temporal deletion of Arl13b in mouse, genetic epistasis with Gli3, neural tube patterning assays\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — temporal conditional deletion plus epistasis with Gli3, single lab\",\n      \"pmids\": [\"23014696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PAK2 signaling in zebrafish regulates ARL13B expression and ciliogenesis in brain endothelial cells; overexpression of ARL13B-GFP rescues cilia numbers and cerebral hemorrhage in pak2a (redhead) mutants. In primary human brain microvascular ECs, PDGF-BB and VEGF-A trigger PAK2-ARL13B ciliogenesis signaling through VEGFR-2.\",\n      \"method\": \"Zebrafish genetic model, mRNA overexpression rescue, primary EC culture, biochemical signaling assays\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo rescue plus in vitro signaling pathway, single lab, two orthogonal systems\",\n      \"pmids\": [\"35700757\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARL13B is an atypical ciliary GTPase and guanine nucleotide exchange factor (GEF) for ARL3 that localizes to the ciliary membrane via palmitoylation and a C-terminal RVEP ciliary targeting sequence (transported by TULP3/IFT-A and Rab8/TNPO1 adaptors); within cilia it regulates Smoothened and GPR161 ciliary trafficking, controls IFT-A-mediated retrograde protein exit, promotes INPP5E ciliary targeting, interacts with tubulin to anchor membrane proteins along the axoneme, drives axoneme polyglutamylation via RAB11-FIP5-TTLL5/6 trafficking, and activates ARL3·GTP to release lipidated cargo—while outside cilia it regulates endocytic recycling, actin-dependent cell migration via Myh9 and integrin signaling, and Shh-mediated axon guidance, with its ciliary GEF activity required for Pkd1-dependent renal cystogenesis and body weight homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARL13B is an atypical, ciliary-membrane-anchored small GTPase of the ARF/ARL family that organizes the protein composition and signaling output of the primary cilium [#0, #1, #11]. Its structure carries an incomplete active site that abolishes intrinsic GTP hydrolysis, and biochemically it acts principally as a guanine nucleotide exchange factor (GEF) for ARL3, generating a spatially restricted ARL3\\u00b7GTP compartment within cilia that drives release of lipidated ciliary cargo [#11, #12, #15]. Membrane targeting depends on N-terminal palmitoylation\\u2014which also stabilizes the protein\\u2014and a C-terminal RVEP/RVVP ciliary-targeting sequence, with ciliary delivery mediated by TULP3/IFT-A and by a Rab8-GDP/TNPO1 import system; AHI1 promotes its ciliary recruitment and proteasomal stability [#16, #27, #28, #7, #23]. Within cilia, ARL13B controls trafficking and dynamic distribution of signaling receptors including Smoothened and GPR161, promotes ciliary targeting of INPP5E, binds tubulin through its G-domain to anchor membrane proteins along the axoneme, and directs axoneme polyglutamylation via a RAB11-FIP5\\u2013dependent import of TTLL5/6 glutamylases\\u2014together enabling Sonic hedgehog signal transduction [#3, #14, #4, #19, #33]. Engineered cilia-excluded (V358A) and GEF-deficient (R79Q) alleles separate these activities, showing that Shh regulation is largely extraciliary while ciliary ARL13B and its ARL3 GEF activity are required for Pkd1-dependent renal cystogenesis, and ciliary ARL13B governs body-weight homeostasis and photoreceptor outer-segment function [#25, #30, #29, #31, #21]. Beyond cilia ARL13B operates in endocytic recycling and in actin- and integrin-dependent cell migration through interactions with Myh9 and \\u03b23-integrin [#6, #10, #24]. Missense mutations that disrupt the ARL13B\\u2013INPP5E interaction or impair ARL3 GEF activity cause Joubert syndrome [#4, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that ARL13B is a bona fide ciliary protein whose function is evolutionarily conserved and disease-relevant, anchoring all subsequent mechanistic work.\",\n      \"evidence\": \"Zebrafish rescue with wild-type versus patient-mutant ARL13B and immunolocalization in murine neurons\",\n      \"pmids\": [\"18674751\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular activity of ARL13B\", \"No partners or substrates identified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined how ARL13B reaches and acts at the cilium, linking membrane anchoring to maintenance of ciliary ultrastructure, transmembrane protein content, and IFT stability.\",\n      \"evidence\": \"C. elegans genetics, IFT motility assays, and epistasis with ciliogenic/IFT genes\",\n      \"pmids\": [\"20231383\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Palmitoylation inferred from motifs, not yet demonstrated biochemically\", \"Direct IFT-complex partners not yet mapped\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed that correct ciliary localization is necessary for in vivo function, framing ARL13B targeting as a mechanistic requirement rather than a passive marker.\",\n      \"evidence\": \"Systematic deletion/point-mutant rescue in arl13b/scorpion zebrafish\",\n      \"pmids\": [\"19906870\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Targeting sequences not yet molecularly resolved\", \"Did not separate ciliary from extraciliary roles\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected ARL13B to Sonic hedgehog signaling by showing it controls dynamic Smoothened distribution in cilia.\",\n      \"evidence\": \"Smo immunofluorescence in Arl13b-null versus wild-type cilia under Shh stimulation\",\n      \"pmids\": [\"21976698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of Smo control (direct vs indirect) not resolved\", \"Did not address other Hh-pathway receptors\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified ARL13B as a hub for ciliary lipid-signaling by demonstrating a direct INPP5E interaction required for INPP5E ciliary targeting, with Joubert mutations disrupting this link.\",\n      \"evidence\": \"Co-IP/binding assays, ciliary localization, and patient mutation analysis defining an ARL13B-INPP5E-PDE6D-CEP164 network\",\n      \"pmids\": [\"23150559\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GEF activity toward ARL3 not yet established\", \"Mechanism coupling INPP5E import to downstream signaling unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended ARL13B function to neuronal cilia, showing it controls guidance-receptor dynamics needed for interneuron migration and placement.\",\n      \"evidence\": \"Conditional knockout mice, live imaging of interneuronal cilia, guidance-receptor immunofluorescence\",\n      \"pmids\": [\"23153492\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific receptors mechanistically regulated not fully defined\", \"Cilia-dependence versus extraciliary contribution not separated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed an extraciliary role in endocytic recycling, indicating ARL13B function is not confined to the cilium.\",\n      \"evidence\": \"shRNA knockdown, CD1a surface/recycling flow cytometry, endosome morphology, colocalization with Arf6/Rab22a\",\n      \"pmids\": [\"23223633\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct effectors in recycling pathway not identified\", \"Single lab; mechanism of endosome clustering unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Placed ARL13B within neural-tube patterning logic, showing it uncouples Gli activator/repressor balance during a defined critical period and acts non-autonomously on BMP signaling.\",\n      \"evidence\": \"Temporal/conditional Arl13b deletion, Gli3 epistasis, in situ hybridization for BMP/Wnt components\",\n      \"pmids\": [\"23014696\", \"21539826\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking ARL13B to GliA/GliR ratio unresolved\", \"Non-autonomous BMP effect mechanistically indirect\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the subciliary compartmentalization of ARL13B and its requirement for an RVVP motif and membrane anchoring, while mapping IFT-B associations and IFT-like motility.\",\n      \"evidence\": \"C. elegans genetics across >20 mutants, in vivo FRAP, and mass-spectrometry interactome (IFT46, IFT74)\",\n      \"pmids\": [\"24339792\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional importance of IFT-B binding versus localization not separated here\", \"Human relevance of compartment boundaries not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established a structural basis for ARL13B's atypical biochemistry, showing an incomplete active site explains absent intrinsic hydrolysis and that patient mutations destabilize key conformational residues.\",\n      \"evidence\": \"X-ray crystallography of Chlamydomonas Arl13B with biochemical GTPase assays and mutant analysis\",\n      \"pmids\": [\"24168557\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No human full-length structure\", \"Catalytic partner (GEF target) not yet identified structurally\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed ARL13B directly binds tubulin via its G-domain independently of GTPase activity to anchor ciliary membrane proteins uniformly along the axoneme.\",\n      \"evidence\": \"Co-IP, in vitro binding, structure-function mutagenesis, and rescue of null MEF ciliogenesis defects\",\n      \"pmids\": [\"29592971\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tubulin-binding interface not mapped at residue level\", \"How anchoring couples to signaling output unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked ARL13B GTPase activity to ciliary membrane extension and placed it downstream of ciliogenic transcription factors FoxJ1/Rfx.\",\n      \"evidence\": \"Zebrafish and mammalian overexpression/loss-of-function with GTPase-dead variants\",\n      \"pmids\": [\"25448689\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of membrane protrusion not defined\", \"Single lab; relationship to GEF activity unaddressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Uncovered extraciliary migration functions through GTP-dependent exocyst binding and a Myh9-dependent role in circular dorsal ruffles.\",\n      \"evidence\": \"GTP/GDP pulldowns, direct binding to Sec8/Sec5, Co-IP with Myh9, RNAi, and zebrafish neural-crest migration assays\",\n      \"pmids\": [\"26582389\", \"24777479\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether exocyst binding operates at cilia or elsewhere not resolved\", \"Direct versus indirect Myh9 effect on migration unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined ARL13B's central enzymatic identity as the GEF for ARL3, establishing that it spatially restricts ARL3\\u00b7GTP to cilia to license cargo release, with Joubert mutations impairing this activity.\",\n      \"evidence\": \"In vitro GEF reconstitution, structural analysis, mammalian overexpression, and patient mutation testing\",\n      \"pmids\": [\"26551564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of lipidated cargoes released downstream not enumerated\", \"In vivo requirement of GEF activity not yet tested by knock-in\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Consolidated the atypical GTPase/GEF biochemistry with purified protein and identified casein kinase 2 phosphorylation as a regulatory modification.\",\n      \"evidence\": \"Recombinant murine Arl13b nucleotide-binding, GTPase, and GEF assays plus mutation characterization\",\n      \"pmids\": [\"28487361\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of CK2 phosphorylation not defined\", \"Regulation of GEF activity in vivo unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established palmitoylation as the in vivo determinant of ciliary trafficking, stability, and function, distinguishing localization from function.\",\n      \"evidence\": \"Biochemical palmitoylation assays in mouse kidney, myristoylation substitution, stability and rescue experiments\",\n      \"pmids\": [\"28848045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Palmitoyltransferase/thioesterase enzymes not identified\", \"How palmitoylation supports function beyond localization unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved the order of trafficking determinants, showing ciliary localization depends on the RVEP CTS and that INPP5E binding—not IFT-B binding—drives IFT-A-mediated retrograde GPR161 exit.\",\n      \"evidence\": \"Visible immunoprecipitation, ARL13B-knockout cells, and rescue with interaction-specific mutants\",\n      \"pmids\": [\"27927754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise step at which retrograde exit fails not defined\", \"Mechanistic coupling of INPP5E to IFT-A machinery unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Implicated ARL13B-Smo interaction in cancer Hedgehog signaling via control of Smo stability and trafficking.\",\n      \"evidence\": \"Co-IP, trafficking assays, tumor proliferation/invasion assays, and in vivo gastric cancer models\",\n      \"pmids\": [\"28611043\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect Smo binding not biochemically resolved\", \"Single disease context\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected ARL13B to axoneme tubulin polyglutamylation through RAB11-FIP5-dependent import of TTLL5/6 glutamylases, mechanistically linking it to sensory receptor anchoring.\",\n      \"evidence\": \"Co-IP for ARL13B-FIP5, TTLL5/6 localization, and CCP5-depletion rescue of hypoglutamylation\",\n      \"pmids\": [\"30120249\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GEF or GTPase activity is required for this trafficking unresolved\", \"Direct glutamylase recruitment mechanism not fully defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified TULP3 as a trafficking adaptor that delivers ARL13B (and INPP5E) to cilia via IFT-A binding, with TUB redundancy.\",\n      \"evidence\": \"TULP3-knockout RPE1 cells rescued with wild-type and IFT-A-binding-deficient TULP3\",\n      \"pmids\": [\"30583862\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relationship to palmitoylation-dependent targeting not resolved here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established ARL13B as essential across retinogenesis stages and for photoreceptor outer-segment morphogenesis and protein trafficking.\",\n      \"evidence\": \"Pan-retina and inducible conditional knockout mice with ERG, immunofluorescence, and electron microscopy\",\n      \"pmids\": [\"30573647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ciliary versus GEF contributions not separated in this study\", \"Specific cargo-trafficking step disrupted not fully defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Tied loss of ARL3 GEF activity directly to Joubert syndrome through a patient variant that selectively abolishes GEF function while preserving GTPase and rescue capacity.\",\n      \"evidence\": \"Whole-exome sequencing plus GEF, cilia-length, and Shh rescue assays for the Gly75Arg variant\",\n      \"pmids\": [\"29255182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which downstream cargo defect causes disease not pinpointed\", \"Genotype-phenotype breadth across patients not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated a cilia-independent ARL13B function in Shh-mediated axon guidance, with a cilia-excluded variant sufficient for guidance.\",\n      \"evidence\": \"Conditional knockout, in vitro axon guidance assays, and cilia-excluded variant rescue\",\n      \"pmids\": [\"31825820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular effectors of axonal ARL13B not identified\", \"How extraciliary ARL13B transduces Shh locally unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified AHI1 as a regulator of ARL13B ciliary recruitment and proteasomal stability, affecting Shh signaling and motility.\",\n      \"evidence\": \"Ahi1-knockout MEFs with localization, proteasome-inhibition stability assays, Shh readouts, and migration assays\",\n      \"pmids\": [\"31391239\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether AHI1 acts directly on ARL13B unresolved\", \"E3 ligase controlling degradation not identified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined an extraciliary migration mechanism through focal-adhesion localization and \\u03b23-integrin interaction controlling surface integrin and adhesion dynamics.\",\n      \"evidence\": \"siRNA, focal-adhesion immunofluorescence, Co-IP with \\u03b23-integrin, surface flow cytometry, and orthotopic breast cancer model\",\n      \"pmids\": [\"31569511\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Nucleotide-state dependence of integrin binding not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Genetically uncoupled ciliary from extraciliary ARL13B, showing the V358A cilia-excluded allele supports normal Shh signaling despite short cilia lacking ARL3 and INPP5E—establishing Shh regulation as primarily extraciliary.\",\n      \"evidence\": \"V358A knock-in mouse with Shh readouts and retrograde-transport blockade experiments\",\n      \"pmids\": [\"32129762\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Where extraciliary Shh transduction occurs spatially not resolved\", \"Mechanism of short cilia in V358A not fully defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked ARL13B to vascular signaling via VEGFR2 interaction and localization control, and to PAK2-driven ciliogenesis in brain endothelium.\",\n      \"evidence\": \"GST-pulldown, Co-IP, luciferase reporters, endothelial mouse models, and zebrafish pak2a rescue\",\n      \"pmids\": [\"36322624\", \"35700757\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect VEGFR2 regulation not fully resolved\", \"Single lab per context\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapped the molecular logic of ARL13B ciliary import, defining a TULP3-tubby/N-terminal amphipathic helix route and a Rab8-GDP/TNPO1 system recognizing the RVEP CTS.\",\n      \"evidence\": \"Domain mapping with knockout rescue, purified-protein pulldowns, TurboID proximity labeling, and RNAi\",\n      \"pmids\": [\"36652335\", \"36907439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Hand-off between palmitoylation, TULP3, and Rab8/TNPO1 routes not integrated\", \"Regulation of Rab8 nucleotide state in this context unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Dissected in vivo physiological requirements using V358A and R79Q alleles, showing ciliary ARL13B is required for body-weight homeostasis (GEF-independent) and that ciliary localization plus GEF activity are required for Pkd1-dependent renal cystogenesis.\",\n      \"evidence\": \"Knock-in mouse models with inducible re-expression, metabolic phenotyping, and Pkd1-cross cystogenesis readouts\",\n      \"pmids\": [\"37577625\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cyst study is a preprint without listed PMID\", \"Downstream ciliary signal mediating weight control not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Further separated ciliary from GEF activity in photoreceptors and revealed roles in spermatogenesis and absolute ciliogenesis, while connecting splicing regulation to ARL13B isoform function.\",\n      \"evidence\": \"V358A/R79Q knock-in ERG/EM analyses, CRISPR knockouts, rescue breeding, and PRPF8-dependent splicing with zebrafish isoform overexpression\",\n      \"pmids\": [\"40721319\", \"40707593\", \"40916698\", \"40501629\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of spermatogenesis role undefined\", \"Functional role of exon-9-lacking isoform partly preprint-stage\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ARL13B's distinct biochemical activities (ARL3 GEF, tubulin binding, atypical GTP binding) are individually deployed across its many ciliary and extraciliary functions, and which downstream effectors transduce each, remains incompletely resolved.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking nucleotide state to specific cargo decisions\", \"Extraciliary Shh transduction mechanism unknown\", \"Enzymes controlling palmitoylation cycle and degradation unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [12, 15, 18]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [12, 15]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 14, 19]},\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [11, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 1, 3, 7, 16, 35]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [16, 24, 26]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [6, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 12, 17, 25]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [6, 13, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 22, 36, 37]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [4, 16, 27, 28]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 9, 33]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [18, 30]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ARL3\", \"INPP5E\", \"TULP3\", \"TNPO1\", \"RAB8\", \"IFT46\", \"MYH9\", \"SMO\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}