{"gene":"KATNIP","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2015,"finding":"KIAA0556 (KATNIP) protein localizes to the ciliary basal body in C. elegans and human cells, binds to microtubules in vitro, and biochemically interacts with p60/p80 katanins (a microtubule-severing enzyme complex). Overexpression in human cells appears to stabilize microtubule networks. In C. elegans, KIAA0556 regulates ciliary A-tubule number and genetically interacts with an ARL13B orthologue to control cilium integrity.","method":"In vitro microtubule binding assay, Co-immunoprecipitation (biochemical interaction with katanins and ciliary proteins), subcellular localization by imaging, C. elegans genetic epistasis (double mutants), Kiaa0556 knockout mice","journal":"Genome biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (in vitro binding, Co-IP, genetic epistasis, knockout mouse, localization), replicated across multiple organisms","pmids":["26714646"],"is_preprint":false},{"year":2016,"finding":"Knockdown of KIAA0556 (KATNIP) in zebrafish produces a ciliopathy phenotype that is rescued by co-injection of wildtype KIAA0556 cDNA, establishing loss-of-function of this gene as causative for the ciliopathy phenotype.","method":"Zebrafish morpholino knockdown with cDNA rescue experiment","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — rescue experiment in zebrafish with wildtype cDNA provides functional validation, single lab","pmids":["27245168"],"is_preprint":false},{"year":2023,"finding":"KATNIP colocalizes with CILK1 at the basal body. The CILK1 C-terminal intrinsically disordered region (IDR) is sufficient to mediate binding to KATNIP. One of three DUF domains (DUF) in KATNIP is required for association with CILK1. KATNIP binding to CILK1 drastically elevates CILK1 protein levels and TDY phosphorylation, increases phosphorylation of CILK1 substrates, and suppresses cilia length. Thus KATNIP functions as a regulatory/scaffold subunit that potentiates CILK1 activity.","method":"Co-localization by fluorescence microscopy, deletion analysis by Co-IP, phosphorylation assays (TDY motif), substrate phosphorylation assays, cilia length measurements","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-localization, deletion mapping, Co-IP, phosphorylation assays, cilia phenotype), single lab but rigorous multi-method approach","pmids":["37665596"],"is_preprint":false},{"year":2023,"finding":"In Dictyostelium discoideum, loss of Katnip causes a general defect in lysosomal delivery to autophagosomes and phagosomes, impairing degradation of endocytic cargos. Loss of Katnip has no overall effect on microtubule dynamics or organization but leads to sensitivity to GFP-tubulin expression, resulting in microtubule tangles, defective anaphase extension, and slow cell growth, indicating a role in microtubule repair/maintenance beyond cilia.","method":"Katnip knockout in Dictyostelium, lysosomal delivery assays, autophagy/phagosome assays, tubulin overexpression sensitization, live cell imaging of microtubule dynamics","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with multiple defined cellular phenotypes, non-mammalian model organism (Dictyostelium), single lab","pmids":["36598819"],"is_preprint":false},{"year":2024,"finding":"The CILK1 A615T variant (linked to juvenile myoclonic epilepsy) is not stabilized/upregulated to the same level as wild-type CILK1 when co-expressed with KATNIP scaffold protein, demonstrating that KATNIP regulation of CILK1 requires an intact IDR residue at position 615. MEFs with A612T mutant alleles show higher ciliation rate, shorter cilia, and upregulated ciliary Hedgehog signaling.","method":"Knock-in mouse model (CRISPR), co-expression assays in cells, cilia length and ciliation rate measurements, Hedgehog signaling assays, gene expression profiling","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knock-in mouse plus co-expression assay, single lab, multiple cellular readouts","pmids":["39120290"],"is_preprint":false},{"year":2025,"finding":"Three human disease-associated variants of KATNIP show loss of function with respect to CILK1 activation. The longest variant (M1474C, truncated near C-terminus) binds CILK1 via DUF2 but fails to support activating TDY phosphorylation of CILK1, phosphorylation of CILK1 substrates, or restriction of cilia length and ciliation rate. Deletion analysis identified residues 1524-1573 (encompassing predicted β-sheets and α-helix) as essential for CILK1 activation. Thus KATNIP uses separate domains for binding vs. activating CILK1.","method":"Co-expression and Co-IP with deletion mutants and disease variants, TDY phosphorylation assays, substrate phosphorylation assays, cilia length and ciliation rate measurements","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — rigorous deletion analysis combined with disease-variant functional assays using multiple orthogonal methods (binding, phosphorylation, cilia phenotype) in a single study","pmids":["40621737"],"is_preprint":false},{"year":2026,"finding":"CRISPR-generated Katnip null mice develop severe hydrocephalus and die around postnatal day 9. Katnip-deficient brain cells exhibit higher rates of cilia formation and longer cilia than wild type, and neuroprogenitor cell proliferation is reduced. This establishes that KATNIP restricts ciliogenesis and cilia extension and supports neuroprogenitor cell proliferation in the brain.","method":"CRISPR-Cas12a Katnip knockout mouse, cilia frequency and length measurements in brain cells, neuroprogenitor proliferation assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO mouse with defined cellular phenotypes (cilia and proliferation), preprint not yet peer-reviewed, single lab","pmids":["42146598"],"is_preprint":true}],"current_model":"KATNIP (KIAA0556) is a scaffold/regulatory protein that localizes to the ciliary basal body, where it binds CILK1 kinase through its IDR to stabilize CILK1, promote activating TDY phosphorylation, and enhance substrate phosphorylation, thereby restricting cilia length and ciliation frequency; KATNIP also interacts with p60/p80 katanin microtubule-severing complexes, binds microtubules directly, and plays a broader role in maintaining microtubule function required for lysosomal trafficking and endocytic cargo degradation, with loss of function causing ciliopathy phenotypes including hydrocephalus, defective Hedgehog signaling, and Joubert syndrome."},"narrative":{"mechanistic_narrative":"KATNIP (KIAA0556) is a basal-body scaffold and regulatory protein that controls ciliary length and ciliation frequency while supporting broader microtubule function [PMID:26714646, PMID:37665596]. It localizes to the ciliary basal body, binds microtubules directly, and biochemically associates with the p60/p80 katanin microtubule-severing complex, and its loss disrupts ciliary integrity across model organisms [PMID:26714646, PMID:27245168]. Mechanistically, KATNIP functions as a regulatory subunit of the CILK1 kinase: it colocalizes with CILK1 at the basal body and engages the CILK1 C-terminal intrinsically disordered region through one of its DUF domains, thereby elevating CILK1 protein levels, promoting activating TDY-motif phosphorylation, enhancing phosphorylation of CILK1 substrates, and suppressing cilia length [PMID:37665596]. KATNIP uses separable domains for these two activities, with a distinct C-terminal region (residues 1524–1573) required for CILK1 activation independent of DUF2-mediated binding [PMID:40621737]. Loss of KATNIP function increases ciliation rate and cilia length, upregulates ciliary Hedgehog signaling, and in mice causes severe hydrocephalus, neonatal lethality, and reduced neuroprogenitor proliferation [PMID:39120290, PMID:42146598]. Beyond cilia, KATNIP maintains microtubule function required for lysosomal delivery to autophagosomes and phagosomes and for endocytic cargo degradation [PMID:36598819]. Human disease-associated KATNIP variants are loss-of-function for CILK1 activation, linking the gene to ciliopathy phenotypes [PMID:27245168, PMID:40621737].","teleology":[{"year":2015,"claim":"Established the founding biochemical and cellular identity of KATNIP: a basal-body, microtubule-binding protein that partners with the katanin severing complex and regulates ciliary integrity.","evidence":"In vitro microtubule binding, Co-IP with p60/p80 katanins, subcellular imaging, C. elegans genetic epistasis with ARL13B orthologue, and Kiaa0556 knockout mice","pmids":["26714646"],"confidence":"High","gaps":["Did not define how KATNIP regulates ciliary tubule number mechanistically","Direct enzymatic role with katanin (regulator vs. substrate) not resolved"]},{"year":2016,"claim":"Demonstrated that KATNIP loss-of-function is causative for the ciliopathy phenotype rather than correlative, using cDNA rescue.","evidence":"Zebrafish morpholino knockdown with wildtype cDNA rescue","pmids":["27245168"],"confidence":"Medium","gaps":["Morpholino approach without genetic mutant confirmation","Molecular mechanism of the rescue not defined"]},{"year":2023,"claim":"Identified the central molecular function of KATNIP as a scaffold/regulatory subunit of CILK1 kinase, mapping the binding interface and showing KATNIP potentiates CILK1 stability, activation, and substrate phosphorylation to restrict cilia length.","evidence":"Co-localization, deletion-mapping Co-IP (DUF domain and CILK1 IDR), TDY and substrate phosphorylation assays, cilia length measurements","pmids":["37665596"],"confidence":"High","gaps":["Structural basis of CILK1 stabilization unresolved","Whether KATNIP-katanin and KATNIP-CILK1 activities are mechanistically linked unknown"]},{"year":2023,"claim":"Revealed a cilia-independent role: KATNIP maintains microtubule function required for lysosomal delivery and endocytic cargo degradation, broadening its cellular role beyond ciliogenesis.","evidence":"Dictyostelium Katnip knockout, lysosomal/autophagosome/phagosome delivery assays, tubulin-overexpression sensitization, live-cell microtubule imaging","pmids":["36598819"],"confidence":"Medium","gaps":["Performed in Dictyostelium; mammalian conservation of the trafficking role not shown","Molecular link between microtubule repair and lysosomal delivery undefined"]},{"year":2024,"claim":"Connected KATNIP-CILK1 regulation to disease by showing the CILK1 IDR residue at position 615 is required for KATNIP-mediated stabilization, with mutant mice showing dysregulated cilia and elevated Hedgehog signaling.","evidence":"CRISPR knock-in mouse, co-expression stabilization assays, cilia/ciliation measurements, Hedgehog signaling and expression profiling","pmids":["39120290"],"confidence":"Medium","gaps":["Effect studied via the CILK1 variant rather than KATNIP mutation directly","Single lab, mechanism of Hedgehog upregulation not dissected"]},{"year":2025,"claim":"Separated KATNIP binding from activation functions, showing disease variants can bind CILK1 yet fail to activate it, and mapping residues 1524-1573 as essential for activation.","evidence":"Co-expression/Co-IP with deletion mutants and disease variants, TDY and substrate phosphorylation assays, cilia length/ciliation measurements","pmids":["40621737"],"confidence":"High","gaps":["Structural mechanism by which the activation region promotes TDY phosphorylation unknown","Whether the activation region recruits an upstream kinase or acts allosterically unresolved"]},{"year":2026,"claim":"Established the in vivo physiological consequence of KATNIP loss: dysregulated ciliogenesis, hydrocephalus, neonatal lethality, and impaired neuroprogenitor proliferation.","evidence":"CRISPR-Cas12a Katnip null mouse, brain cilia frequency/length measurements, neuroprogenitor proliferation assays","pmids":["42146598"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Causal chain from cilia defect to hydrocephalus and proliferation defect not fully resolved"]},{"year":null,"claim":"How KATNIP coordinates its two arms — CILK1 kinase regulation and katanin/microtubule maintenance — within a single mechanistic framework remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of KATNIP or its complexes with CILK1 or katanin","Whether microtubule-severing regulation and CILK1 activation are independent or coupled functions is unknown","Direct molecular role at the basal body not fully defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,5]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,3]}],"pathway":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,2,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]}],"complexes":[],"partners":["CILK1","KATNA1","KATNB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60303","full_name":"Katanin-interacting protein","aliases":[],"length_aa":1618,"mass_kda":180.9,"function":"May influence the stability of microtubules (MT), possibly through interaction with the MT-severing katanin complex","subcellular_location":"Cytoplasm, cytoskeleton, cilium axoneme; Cytoplasm, cytoskeleton, cilium basal body; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/O60303/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KATNIP","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KATNIP","total_profiled":1310},"omim":[{"mim_id":"621378","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 161; CFAP161","url":"https://www.omim.org/entry/621378"},{"mim_id":"616784","title":"JOUBERT SYNDROME 26; JBTS26","url":"https://www.omim.org/entry/616784"},{"mim_id":"616650","title":"KATANIN-INTERACTING PROTEIN; KATNIP","url":"https://www.omim.org/entry/616650"},{"mim_id":"213300","title":"JOUBERT SYNDROME 1; JBTS1","url":"https://www.omim.org/entry/213300"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Basal body","reliability":"Approved"},{"location":"Primary cilium","reliability":"Additional"},{"location":"Centriolar satellite","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KATNIP"},"hgnc":{"alias_symbol":["JBTS26"],"prev_symbol":["KIAA0556"]},"alphafold":{"accession":"O60303","domains":[{"cath_id":"2.60.60,2.60.60","chopping":"477-533_542-623","consensus_level":"high","plddt":82.7656,"start":477,"end":623},{"cath_id":"-","chopping":"974-1139","consensus_level":"high","plddt":90.3356,"start":974,"end":1139},{"cath_id":"-","chopping":"1208-1370","consensus_level":"high","plddt":89.5001,"start":1208,"end":1370},{"cath_id":"-","chopping":"1399-1537_1546-1566","consensus_level":"high","plddt":88.9649,"start":1399,"end":1566}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60303","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60303-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60303-F1-predicted_aligned_error_v6.png","plddt_mean":58.41},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KATNIP","jax_strain_url":"https://www.jax.org/strain/search?query=KATNIP"},"sequence":{"accession":"O60303","fasta_url":"https://rest.uniprot.org/uniprotkb/O60303.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60303/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60303"}},"corpus_meta":[{"pmid":"26714646","id":"PMC_26714646","title":"KIAA0556 is a novel ciliary basal body component mutated in Joubert syndrome.","date":"2015","source":"Genome biology","url":"https://pubmed.ncbi.nlm.nih.gov/26714646","citation_count":60,"is_preprint":false},{"pmid":"31197031","id":"PMC_31197031","title":"Pathogenic variants of DYNC2H1, KIAA0556, and PTPN11 associated with hypothalamic hamartoma.","date":"2019","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/31197031","citation_count":26,"is_preprint":false},{"pmid":"27245168","id":"PMC_27245168","title":"Identification of a homozygous nonsense mutation in KIAA0556 in a consanguineous family displaying Joubert syndrome.","date":"2016","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27245168","citation_count":20,"is_preprint":false},{"pmid":"37665596","id":"PMC_37665596","title":"The Scaffold Protein KATNIP Enhances CILK1 Control of Primary Cilia.","date":"2023","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/37665596","citation_count":7,"is_preprint":false},{"pmid":"39120290","id":"PMC_39120290","title":"An Epilepsy-Associated CILK1 Variant Compromises KATNIP Regulation and Impairs Primary Cilia and Hedgehog Signaling.","date":"2024","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/39120290","citation_count":2,"is_preprint":false},{"pmid":"40621737","id":"PMC_40621737","title":"Human disease variants of KATNIP fail to support CILK1 activation and control of primary cilia.","date":"2025","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/40621737","citation_count":2,"is_preprint":false},{"pmid":"36598819","id":"PMC_36598819","title":"Katnip is needed to maintain microtubule function and lysosomal delivery to autophagosomes and phagosomes.","date":"2023","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/36598819","citation_count":1,"is_preprint":false},{"pmid":"38798407","id":"PMC_38798407","title":"An epilepsy-associated CILK1 variant compromises KATNIP regulation and impairs primary cilia and Hedgehog signaling.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38798407","citation_count":0,"is_preprint":false},{"pmid":"40428346","id":"PMC_40428346","title":"Phenotypic Spectrum of KATNIP-Associated Joubert Syndrome: Possible Association with Esophageal Atresia and Review of the Literature.","date":"2025","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/40428346","citation_count":0,"is_preprint":false},{"pmid":"41798972","id":"PMC_41798972","title":"PITUITARY STALK INTERRUPTION SYNDROME CAUSED BY NOVEL COMPOUND HETEROZYGOUS MUTATIONS IN THE KATNIP GENE.","date":"2025","source":"Acta endocrinologica (Bucharest, Romania : 2005)","url":"https://pubmed.ncbi.nlm.nih.gov/41798972","citation_count":0,"is_preprint":false},{"pmid":"42146598","id":"PMC_42146598","title":"Hydrocephalus caused by Katnip deletion is linked to increased ciliogenesis and reduced proliferation of neuroprogenitor cells.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/42146598","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7032,"output_tokens":2107,"usd":0.02635,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9078,"output_tokens":2902,"usd":0.05897,"stage2_stop_reason":"end_turn"},"total_usd":0.08532,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"KIAA0556 (KATNIP) protein localizes to the ciliary basal body in C. elegans and human cells, binds to microtubules in vitro, and biochemically interacts with p60/p80 katanins (a microtubule-severing enzyme complex). Overexpression in human cells appears to stabilize microtubule networks. In C. elegans, KIAA0556 regulates ciliary A-tubule number and genetically interacts with an ARL13B orthologue to control cilium integrity.\",\n      \"method\": \"In vitro microtubule binding assay, Co-immunoprecipitation (biochemical interaction with katanins and ciliary proteins), subcellular localization by imaging, C. elegans genetic epistasis (double mutants), Kiaa0556 knockout mice\",\n      \"journal\": \"Genome biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (in vitro binding, Co-IP, genetic epistasis, knockout mouse, localization), replicated across multiple organisms\",\n      \"pmids\": [\"26714646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Knockdown of KIAA0556 (KATNIP) in zebrafish produces a ciliopathy phenotype that is rescued by co-injection of wildtype KIAA0556 cDNA, establishing loss-of-function of this gene as causative for the ciliopathy phenotype.\",\n      \"method\": \"Zebrafish morpholino knockdown with cDNA rescue experiment\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — rescue experiment in zebrafish with wildtype cDNA provides functional validation, single lab\",\n      \"pmids\": [\"27245168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KATNIP colocalizes with CILK1 at the basal body. The CILK1 C-terminal intrinsically disordered region (IDR) is sufficient to mediate binding to KATNIP. One of three DUF domains (DUF) in KATNIP is required for association with CILK1. KATNIP binding to CILK1 drastically elevates CILK1 protein levels and TDY phosphorylation, increases phosphorylation of CILK1 substrates, and suppresses cilia length. Thus KATNIP functions as a regulatory/scaffold subunit that potentiates CILK1 activity.\",\n      \"method\": \"Co-localization by fluorescence microscopy, deletion analysis by Co-IP, phosphorylation assays (TDY motif), substrate phosphorylation assays, cilia length measurements\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-localization, deletion mapping, Co-IP, phosphorylation assays, cilia phenotype), single lab but rigorous multi-method approach\",\n      \"pmids\": [\"37665596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In Dictyostelium discoideum, loss of Katnip causes a general defect in lysosomal delivery to autophagosomes and phagosomes, impairing degradation of endocytic cargos. Loss of Katnip has no overall effect on microtubule dynamics or organization but leads to sensitivity to GFP-tubulin expression, resulting in microtubule tangles, defective anaphase extension, and slow cell growth, indicating a role in microtubule repair/maintenance beyond cilia.\",\n      \"method\": \"Katnip knockout in Dictyostelium, lysosomal delivery assays, autophagy/phagosome assays, tubulin overexpression sensitization, live cell imaging of microtubule dynamics\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with multiple defined cellular phenotypes, non-mammalian model organism (Dictyostelium), single lab\",\n      \"pmids\": [\"36598819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The CILK1 A615T variant (linked to juvenile myoclonic epilepsy) is not stabilized/upregulated to the same level as wild-type CILK1 when co-expressed with KATNIP scaffold protein, demonstrating that KATNIP regulation of CILK1 requires an intact IDR residue at position 615. MEFs with A612T mutant alleles show higher ciliation rate, shorter cilia, and upregulated ciliary Hedgehog signaling.\",\n      \"method\": \"Knock-in mouse model (CRISPR), co-expression assays in cells, cilia length and ciliation rate measurements, Hedgehog signaling assays, gene expression profiling\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knock-in mouse plus co-expression assay, single lab, multiple cellular readouts\",\n      \"pmids\": [\"39120290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Three human disease-associated variants of KATNIP show loss of function with respect to CILK1 activation. The longest variant (M1474C, truncated near C-terminus) binds CILK1 via DUF2 but fails to support activating TDY phosphorylation of CILK1, phosphorylation of CILK1 substrates, or restriction of cilia length and ciliation rate. Deletion analysis identified residues 1524-1573 (encompassing predicted β-sheets and α-helix) as essential for CILK1 activation. Thus KATNIP uses separate domains for binding vs. activating CILK1.\",\n      \"method\": \"Co-expression and Co-IP with deletion mutants and disease variants, TDY phosphorylation assays, substrate phosphorylation assays, cilia length and ciliation rate measurements\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — rigorous deletion analysis combined with disease-variant functional assays using multiple orthogonal methods (binding, phosphorylation, cilia phenotype) in a single study\",\n      \"pmids\": [\"40621737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CRISPR-generated Katnip null mice develop severe hydrocephalus and die around postnatal day 9. Katnip-deficient brain cells exhibit higher rates of cilia formation and longer cilia than wild type, and neuroprogenitor cell proliferation is reduced. This establishes that KATNIP restricts ciliogenesis and cilia extension and supports neuroprogenitor cell proliferation in the brain.\",\n      \"method\": \"CRISPR-Cas12a Katnip knockout mouse, cilia frequency and length measurements in brain cells, neuroprogenitor proliferation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO mouse with defined cellular phenotypes (cilia and proliferation), preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"42146598\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"KATNIP (KIAA0556) is a scaffold/regulatory protein that localizes to the ciliary basal body, where it binds CILK1 kinase through its IDR to stabilize CILK1, promote activating TDY phosphorylation, and enhance substrate phosphorylation, thereby restricting cilia length and ciliation frequency; KATNIP also interacts with p60/p80 katanin microtubule-severing complexes, binds microtubules directly, and plays a broader role in maintaining microtubule function required for lysosomal trafficking and endocytic cargo degradation, with loss of function causing ciliopathy phenotypes including hydrocephalus, defective Hedgehog signaling, and Joubert syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KATNIP (KIAA0556) is a basal-body scaffold and regulatory protein that controls ciliary length and ciliation frequency while supporting broader microtubule function [#0, #2]. It localizes to the ciliary basal body, binds microtubules directly, and biochemically associates with the p60/p80 katanin microtubule-severing complex, and its loss disrupts ciliary integrity across model organisms [#0, #1]. Mechanistically, KATNIP functions as a regulatory subunit of the CILK1 kinase: it colocalizes with CILK1 at the basal body and engages the CILK1 C-terminal intrinsically disordered region through one of its DUF domains, thereby elevating CILK1 protein levels, promoting activating TDY-motif phosphorylation, enhancing phosphorylation of CILK1 substrates, and suppressing cilia length [#2]. KATNIP uses separable domains for these two activities, with a distinct C-terminal region (residues 1524–1573) required for CILK1 activation independent of DUF2-mediated binding [#5]. Loss of KATNIP function increases ciliation rate and cilia length, upregulates ciliary Hedgehog signaling, and in mice causes severe hydrocephalus, neonatal lethality, and reduced neuroprogenitor proliferation [#4, #6]. Beyond cilia, KATNIP maintains microtubule function required for lysosomal delivery to autophagosomes and phagosomes and for endocytic cargo degradation [#3]. Human disease-associated KATNIP variants are loss-of-function for CILK1 activation, linking the gene to ciliopathy phenotypes [#1, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established the founding biochemical and cellular identity of KATNIP: a basal-body, microtubule-binding protein that partners with the katanin severing complex and regulates ciliary integrity.\",\n      \"evidence\": \"In vitro microtubule binding, Co-IP with p60/p80 katanins, subcellular imaging, C. elegans genetic epistasis with ARL13B orthologue, and Kiaa0556 knockout mice\",\n      \"pmids\": [\"26714646\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how KATNIP regulates ciliary tubule number mechanistically\", \"Direct enzymatic role with katanin (regulator vs. substrate) not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated that KATNIP loss-of-function is causative for the ciliopathy phenotype rather than correlative, using cDNA rescue.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with wildtype cDNA rescue\",\n      \"pmids\": [\"27245168\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino approach without genetic mutant confirmation\", \"Molecular mechanism of the rescue not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified the central molecular function of KATNIP as a scaffold/regulatory subunit of CILK1 kinase, mapping the binding interface and showing KATNIP potentiates CILK1 stability, activation, and substrate phosphorylation to restrict cilia length.\",\n      \"evidence\": \"Co-localization, deletion-mapping Co-IP (DUF domain and CILK1 IDR), TDY and substrate phosphorylation assays, cilia length measurements\",\n      \"pmids\": [\"37665596\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CILK1 stabilization unresolved\", \"Whether KATNIP-katanin and KATNIP-CILK1 activities are mechanistically linked unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a cilia-independent role: KATNIP maintains microtubule function required for lysosomal delivery and endocytic cargo degradation, broadening its cellular role beyond ciliogenesis.\",\n      \"evidence\": \"Dictyostelium Katnip knockout, lysosomal/autophagosome/phagosome delivery assays, tubulin-overexpression sensitization, live-cell microtubule imaging\",\n      \"pmids\": [\"36598819\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Performed in Dictyostelium; mammalian conservation of the trafficking role not shown\", \"Molecular link between microtubule repair and lysosomal delivery undefined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected KATNIP-CILK1 regulation to disease by showing the CILK1 IDR residue at position 615 is required for KATNIP-mediated stabilization, with mutant mice showing dysregulated cilia and elevated Hedgehog signaling.\",\n      \"evidence\": \"CRISPR knock-in mouse, co-expression stabilization assays, cilia/ciliation measurements, Hedgehog signaling and expression profiling\",\n      \"pmids\": [\"39120290\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Effect studied via the CILK1 variant rather than KATNIP mutation directly\", \"Single lab, mechanism of Hedgehog upregulation not dissected\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Separated KATNIP binding from activation functions, showing disease variants can bind CILK1 yet fail to activate it, and mapping residues 1524-1573 as essential for activation.\",\n      \"evidence\": \"Co-expression/Co-IP with deletion mutants and disease variants, TDY and substrate phosphorylation assays, cilia length/ciliation measurements\",\n      \"pmids\": [\"40621737\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism by which the activation region promotes TDY phosphorylation unknown\", \"Whether the activation region recruits an upstream kinase or acts allosterically unresolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Established the in vivo physiological consequence of KATNIP loss: dysregulated ciliogenesis, hydrocephalus, neonatal lethality, and impaired neuroprogenitor proliferation.\",\n      \"evidence\": \"CRISPR-Cas12a Katnip null mouse, brain cilia frequency/length measurements, neuroprogenitor proliferation assays\",\n      \"pmids\": [\"42146598\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Causal chain from cilia defect to hydrocephalus and proliferation defect not fully resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How KATNIP coordinates its two arms — CILK1 kinase regulation and katanin/microtubule maintenance — within a single mechanistic framework remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of KATNIP or its complexes with CILK1 or katanin\", \"Whether microtubule-severing regulation and CILK1 activation are independent or coupled functions is unknown\", \"Direct molecular role at the basal body not fully defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CILK1\", \"KATNA1\", \"KATNB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}