{"gene":"RTTN","run_date":"2026-04-28T20:42:06","timeline":{"discoveries":[{"year":2012,"finding":"RTTN (Rotatin) colocalizes with basal bodies at the primary cilium, and patient fibroblasts with RTTN mutations show structural abnormalities of cilia and downregulation of BMP4, WNT5A, and WNT2B, linking RTTN to cilia structure/function and downstream signaling pathways required for cortical patterning.","method":"Immunofluorescence colocalization, knockdown in human fibroblasts and neural stem cells, gene expression analysis","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization and KD phenotype in patient cells and neural stem cells, single lab with multiple methods","pmids":["22939636"],"is_preprint":false},{"year":2017,"finding":"RTTN is recruited to the proximal end of the procentriole at early S phase and localizes to the inner luminal walls of centrioles; it directly interacts with STIL and acts downstream of STIL-mediated centriole assembly; RTTN serves as an upstream effector of CEP295, which mediates loading of POC1B and POC5 to distal-half centrioles; CRISPR knockout causes amplification of primitive procentriole bodies lacking distal-half centriolar proteins; the disease-associated RTTN(A578P) mutation shows low affinity for STIL and blocks centriole assembly.","method":"Super-resolution and electron microscopy, Co-IP, CRISPR/Cas9 knockout, mutant protein binding assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — direct interaction demonstrated by Co-IP, structural localization by super-resolution/EM, epistasis established by KO + rescue, disease mutant functional validation","pmids":["28811500"],"is_preprint":false},{"year":2018,"finding":"PPP1R35 acts downstream of RTTN and forms a complex with RTTN; RTTN is required for distal centriole elongation and functions upstream of PPP1R35 in the centriole elongation pathway.","method":"Quantitative super-resolution microscopy, live-cell imaging, loss-of-function experiments, proximity-ligation/BioID interactome","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — complex formation demonstrated, epistasis established with super-resolution mapping and functional KD in two independent proteins, replicated findings","pmids":["30168418"],"is_preprint":false},{"year":2021,"finding":"RTTN is required for normal mitotic progression and correct spindle positioning; RTTN depletion causes dispersion of pericentriolar γ-tubulin, monopolar/abnormal bipolar/multipolar spindles, altered NuMA/p150Glued congression to spindle poles, perturbed NuMA cortical localization, and reduced number and length of astral microtubules.","method":"RNAi depletion, immunofluorescence, spindle positioning assays","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2-3 — clean KD with specific mitotic phenotypic readouts and molecular markers, single lab","pmids":["34207628"],"is_preprint":false},{"year":2024,"finding":"RTTN is required for the self-organisation of neural stem cells (NSCs) into neural rosettes and for proper apico-basal polarization of NSCs; RTTN-mutant NSCs in cortical organoids show major cell cycle and mitotic abnormalities including aneuploidy, cell cycle arrest, and cell death, leading to delayed rosette formation and impaired organoid growth.","method":"CRISPR/Cas9-edited iPSC-derived NSCs, cortical organoids, live imaging, immunostaining","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 — novel function identified in human cortical organoids with CRISPR-engineered cells and multiple cellular readouts, single lab","pmids":["39680576"],"is_preprint":false}],"current_model":"RTTN (Rotatin) is a centrosomal protein that localizes to the inner luminal walls of centrioles; it directly binds STIL and acts downstream of STIL to promote centriole elongation by serving as an upstream effector of CEP295 (which loads distal centriolar proteins POC1B and POC5), and of PPP1R35 (a downstream complex partner); additionally, RTTN is required for mitotic spindle integrity and correct spindle positioning, for primary cilia structure and BMP/WNT signaling, and for neural stem cell apico-basal polarization and rosette formation during cortical development."},"narrative":{"teleology":[{"year":2012,"claim":"Establishing that RTTN is a cilium-associated protein whose loss disrupts cilia structure and downstream BMP/WNT signaling resolved the initial question of where and at what developmental process RTTN acts, linking it to cortical patterning defects in microcephaly patients.","evidence":"Immunofluorescence colocalization with basal bodies, patient fibroblast and NSC analysis with gene expression profiling","pmids":["22939636"],"confidence":"Medium","gaps":["Mechanism by which RTTN maintains cilium structure was not defined","Direct protein-protein interactions were not identified","Whether cilia defect is secondary to a centriolar role was untested"]},{"year":2017,"claim":"Pinpointing RTTN to the inner centriolar lumen and demonstrating its direct binding to STIL, its epistatic position upstream of CEP295 in distal centriole assembly, and the functional impact of a disease-associated missense mutation answered how RTTN contributes to centriole biogenesis at a molecular level.","evidence":"Super-resolution and electron microscopy, co-immunoprecipitation, CRISPR knockout and rescue, mutant binding assays in human cells","pmids":["28811500"],"confidence":"High","gaps":["Structural basis of the RTTN–STIL interaction is unknown","How RTTN activates CEP295 loading mechanistically was not resolved","Whether RTTN has additional partners beyond STIL at the procentriole was not tested"]},{"year":2018,"claim":"Identifying PPP1R35 as a downstream effector that forms a complex with RTTN extended the centriole elongation pathway and clarified that RTTN operates through at least two downstream branches (CEP295 and PPP1R35).","evidence":"Quantitative super-resolution microscopy, BioID proximity mapping, loss-of-function epistasis experiments","pmids":["30168418"],"confidence":"High","gaps":["Whether the RTTN–PPP1R35 complex is direct or bridged by additional subunits is unresolved","Stoichiometry and regulation of the complex during the cell cycle are unknown"]},{"year":2021,"claim":"Demonstrating that RTTN depletion causes γ-tubulin dispersal, spindle multipolarity, mislocalized NuMA/p150Glued, and reduced astral microtubules established a second major function for RTTN in mitotic spindle organization and positioning, beyond centriole assembly.","evidence":"RNAi depletion with immunofluorescence and spindle positioning assays in human cells","pmids":["34207628"],"confidence":"Medium","gaps":["Single-lab RNAi study; independent confirmation with orthogonal depletion strategies is lacking","Whether spindle defects are a direct consequence of centriole structural defects or reflect a separable RTTN function is untested","Molecular mechanism linking RTTN to NuMA cortical recruitment is unknown"]},{"year":2024,"claim":"Showing that RTTN-mutant iPSC-derived neural stem cells fail to polarize apico-basally, delay rosette self-organization, and exhibit aneuploidy and cell death in cortical organoids connected RTTN's centriolar and mitotic functions to a tissue-level developmental phenotype relevant to human microcephaly.","evidence":"CRISPR/Cas9-edited iPSC-derived cortical organoids with live imaging and immunostaining","pmids":["39680576"],"confidence":"Medium","gaps":["Single-lab organoid model; replication in animal models or independent iPSC lines would strengthen claims","Relative contributions of centriole elongation defects versus spindle positioning defects to the cortical phenotype are not delineated","Whether RTTN's role in rosette formation depends on primary cilia signaling or is purely centrosomal is unresolved"]},{"year":null,"claim":"A structural understanding of RTTN—including its domain architecture, how it bridges STIL binding to CEP295 and PPP1R35 activation, and whether its spindle-positioning function is mechanistically separable from its centriole elongation role—remains an open question.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of RTTN or its complexes exists","Separation-of-function mutations distinguishing centriole elongation from spindle positioning roles have not been generated","Regulatory inputs (phosphorylation, cell-cycle-dependent degradation) are unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,3]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,1,2,3]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,4]}],"complexes":["RTTN–PPP1R35 complex"],"partners":["STIL","CEP295","PPP1R35","POC1B","POC5"],"other_free_text":[]},"mechanistic_narrative":"RTTN (Rotatin) is a centriolar structural protein that functions in centriole elongation, mitotic spindle integrity, and primary cilium-dependent signaling. It localizes to the inner luminal walls of centrioles, where it directly binds STIL and acts downstream of STIL-mediated centriole assembly to promote distal centriole elongation through recruitment of CEP295 (which loads POC1B and POC5) and through complex formation with the downstream effector PPP1R35 [PMID:28811500, PMID:30168418]. RTTN is also required for normal mitotic spindle organization, correct spindle positioning via regulation of pericentriolar γ-tubulin, NuMA, and astral microtubule dynamics [PMID:34207628], and for primary cilium structure and BMP/WNT signaling [PMID:22939636]. Biallelic RTTN mutations cause microcephaly with abnormal cortical development, consistent with its requirement for neural stem cell apico-basal polarization, rosette formation, and cell cycle fidelity in cortical organoids [PMID:22939636, PMID:39680576]."},"prefetch_data":{"uniprot":{"accession":"Q86VV8","full_name":"Rotatin","aliases":[],"length_aa":2226,"mass_kda":248.6,"function":"Involved in the genetic cascade that governs left-right specification. Plays a role in the maintenance of a normal ciliary structure. Required for correct asymmetric expression of NODAL, LEFTY and PITX2","subcellular_location":"Cytoplasm, cytoskeleton, cilium basal body; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome","url":"https://www.uniprot.org/uniprotkb/Q86VV8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RTTN","classification":"Not Classified","n_dependent_lines":628,"n_total_lines":1208,"dependency_fraction":0.5198675496688742},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RTTN","total_profiled":1310},"omim":[{"mim_id":"618937","title":"PROTEIN PHOSPHATASE 1, REGULATORY SUBUNIT 35; PPP1R35","url":"https://www.omim.org/entry/618937"},{"mim_id":"614833","title":"MICROCEPHALY, SHORT STATURE, AND POLYMICROGYRIA WITH OR WITHOUT SEIZURES; MSSP","url":"https://www.omim.org/entry/614833"},{"mim_id":"610436","title":"ROTATIN; RTTN","url":"https://www.omim.org/entry/610436"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Cytosol","reliability":"Uncertain"},{"location":"Centrosome","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RTTN"},"hgnc":{"alias_symbol":["DKFZP434G145"],"prev_symbol":[]},"alphafold":{"accession":"Q86VV8","domains":[{"cath_id":"1.25.10.10","chopping":"2-114","consensus_level":"high","plddt":86.991,"start":2,"end":114},{"cath_id":"-","chopping":"379-533","consensus_level":"medium","plddt":90.5681,"start":379,"end":533},{"cath_id":"-","chopping":"764-840_860-964_975-996","consensus_level":"high","plddt":85.7094,"start":764,"end":996},{"cath_id":"-","chopping":"1227-1343","consensus_level":"medium","plddt":79.9174,"start":1227,"end":1343},{"cath_id":"1.25.10.10","chopping":"2054-2063_2072-2226","consensus_level":"high","plddt":82.2593,"start":2054,"end":2226},{"cath_id":"1.20.930","chopping":"181-277_370-377","consensus_level":"medium","plddt":84.6301,"start":181,"end":377},{"cath_id":"1.20.870","chopping":"590-718","consensus_level":"medium","plddt":87.7779,"start":590,"end":718},{"cath_id":"1.25.40","chopping":"1068-1188_1204-1222","consensus_level":"medium","plddt":80.3599,"start":1068,"end":1222}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86VV8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86VV8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86VV8-F1-predicted_aligned_error_v6.png","plddt_mean":77.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RTTN","jax_strain_url":"https://www.jax.org/strain/search?query=RTTN"},"sequence":{"accession":"Q86VV8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86VV8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86VV8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86VV8"}},"corpus_meta":[{"pmid":"22939636","id":"PMC_22939636","title":"RTTN mutations link primary cilia function to organization of the human cerebral cortex.","date":"2012","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22939636","citation_count":58,"is_preprint":false},{"pmid":"28811500","id":"PMC_28811500","title":"Human microcephaly protein RTTN interacts with STIL and is required to build full-length centrioles.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28811500","citation_count":39,"is_preprint":false},{"pmid":"26608784","id":"PMC_26608784","title":"RTTN Mutations Cause Primary Microcephaly and Primordial Dwarfism in Humans.","date":"2015","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26608784","citation_count":38,"is_preprint":false},{"pmid":"30168418","id":"PMC_30168418","title":"PPP1R35 is a novel centrosomal protein that regulates centriole length in concert with the microcephaly protein RTTN.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/30168418","citation_count":29,"is_preprint":false},{"pmid":"26940245","id":"PMC_26940245","title":"Expanding the phenotype of RTTN variations: a new family with primary microcephaly, severe growth failure, brain malformations and dermatitis.","date":"2016","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26940245","citation_count":21,"is_preprint":false},{"pmid":"30121372","id":"PMC_30121372","title":"Recurrent RTTN mutation leading to severe microcephaly, polymicrogyria and growth restriction.","date":"2018","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30121372","citation_count":13,"is_preprint":false},{"pmid":"29883675","id":"PMC_29883675","title":"Biallelic mutations in RTTN are associated with microcephaly, short stature and a wide range of brain malformations.","date":"2018","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29883675","citation_count":11,"is_preprint":false},{"pmid":"34207628","id":"PMC_34207628","title":"Human Microcephaly Protein RTTN Is Required for Proper Mitotic Progression and Correct Spindle Position.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34207628","citation_count":8,"is_preprint":false},{"pmid":"29356416","id":"PMC_29356416","title":"A neuropathological study of novel RTTN gene mutations causing a familial microcephaly with simplified gyral pattern.","date":"2018","source":"Birth defects research","url":"https://pubmed.ncbi.nlm.nih.gov/29356416","citation_count":8,"is_preprint":false},{"pmid":"37371259","id":"PMC_37371259","title":"Microcephaly, Short Stature, Intellectual Disability, Speech Absence and Cataract Are Associated with Novel Bi-Allelic Missense Variant in RTTN Gene: A Seckel Syndrome Case Report.","date":"2023","source":"Children (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/37371259","citation_count":7,"is_preprint":false},{"pmid":"34012324","id":"PMC_34012324","title":"Exome sequencing reveled a compound heterozygous mutations in RTTN gene causing developmental delay and primary microcephaly.","date":"2021","source":"Saudi journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34012324","citation_count":6,"is_preprint":false},{"pmid":"30927481","id":"PMC_30927481","title":"Primary microcephaly, primordial dwarfism, and brachydactyly in adult cases with biallelic skipping of RTTN exon 42.","date":"2019","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/30927481","citation_count":3,"is_preprint":false},{"pmid":"39680576","id":"PMC_39680576","title":"A Taybi-Linder syndrome-related RTTN variant impedes neural rosette formation in human cortical organoids.","date":"2024","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39680576","citation_count":2,"is_preprint":false},{"pmid":"40151166","id":"PMC_40151166","title":"Radial Microbrain (Micrencephaly) Is Caused by a Recurrent Variant in the RTTN Gene.","date":"2025","source":"Neurology. Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40151166","citation_count":1,"is_preprint":false},{"pmid":"38178912","id":"PMC_38178912","title":"Case Report: Novel biallelic moderately damaging variants in RTTN in a patient with cerebellar dysplasia.","date":"2023","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/38178912","citation_count":1,"is_preprint":false},{"pmid":"41719742","id":"PMC_41719742","title":"Generation of the iPSC line CRNLi001-A from a patient with microcephaly and harbouring the most recurrent RTTN variant, c.2953A>G, at homozygous state.","date":"2026","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/41719742","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8275,"output_tokens":1306,"usd":0.022208},"stage2":{"model":"claude-opus-4-6","input_tokens":4525,"output_tokens":1890,"usd":0.104813},"total_usd":0.127021,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"RTTN (Rotatin) colocalizes with basal bodies at the primary cilium, and patient fibroblasts with RTTN mutations show structural abnormalities of cilia and downregulation of BMP4, WNT5A, and WNT2B, linking RTTN to cilia structure/function and downstream signaling pathways required for cortical patterning.\",\n      \"method\": \"Immunofluorescence colocalization, knockdown in human fibroblasts and neural stem cells, gene expression analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization and KD phenotype in patient cells and neural stem cells, single lab with multiple methods\",\n      \"pmids\": [\"22939636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RTTN is recruited to the proximal end of the procentriole at early S phase and localizes to the inner luminal walls of centrioles; it directly interacts with STIL and acts downstream of STIL-mediated centriole assembly; RTTN serves as an upstream effector of CEP295, which mediates loading of POC1B and POC5 to distal-half centrioles; CRISPR knockout causes amplification of primitive procentriole bodies lacking distal-half centriolar proteins; the disease-associated RTTN(A578P) mutation shows low affinity for STIL and blocks centriole assembly.\",\n      \"method\": \"Super-resolution and electron microscopy, Co-IP, CRISPR/Cas9 knockout, mutant protein binding assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct interaction demonstrated by Co-IP, structural localization by super-resolution/EM, epistasis established by KO + rescue, disease mutant functional validation\",\n      \"pmids\": [\"28811500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PPP1R35 acts downstream of RTTN and forms a complex with RTTN; RTTN is required for distal centriole elongation and functions upstream of PPP1R35 in the centriole elongation pathway.\",\n      \"method\": \"Quantitative super-resolution microscopy, live-cell imaging, loss-of-function experiments, proximity-ligation/BioID interactome\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — complex formation demonstrated, epistasis established with super-resolution mapping and functional KD in two independent proteins, replicated findings\",\n      \"pmids\": [\"30168418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RTTN is required for normal mitotic progression and correct spindle positioning; RTTN depletion causes dispersion of pericentriolar γ-tubulin, monopolar/abnormal bipolar/multipolar spindles, altered NuMA/p150Glued congression to spindle poles, perturbed NuMA cortical localization, and reduced number and length of astral microtubules.\",\n      \"method\": \"RNAi depletion, immunofluorescence, spindle positioning assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — clean KD with specific mitotic phenotypic readouts and molecular markers, single lab\",\n      \"pmids\": [\"34207628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RTTN is required for the self-organisation of neural stem cells (NSCs) into neural rosettes and for proper apico-basal polarization of NSCs; RTTN-mutant NSCs in cortical organoids show major cell cycle and mitotic abnormalities including aneuploidy, cell cycle arrest, and cell death, leading to delayed rosette formation and impaired organoid growth.\",\n      \"method\": \"CRISPR/Cas9-edited iPSC-derived NSCs, cortical organoids, live imaging, immunostaining\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — novel function identified in human cortical organoids with CRISPR-engineered cells and multiple cellular readouts, single lab\",\n      \"pmids\": [\"39680576\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RTTN (Rotatin) is a centrosomal protein that localizes to the inner luminal walls of centrioles; it directly binds STIL and acts downstream of STIL to promote centriole elongation by serving as an upstream effector of CEP295 (which loads distal centriolar proteins POC1B and POC5), and of PPP1R35 (a downstream complex partner); additionally, RTTN is required for mitotic spindle integrity and correct spindle positioning, for primary cilia structure and BMP/WNT signaling, and for neural stem cell apico-basal polarization and rosette formation during cortical development.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RTTN (Rotatin) is a centriolar structural protein that functions in centriole elongation, mitotic spindle integrity, and primary cilium-dependent signaling. It localizes to the inner luminal walls of centrioles, where it directly binds STIL and acts downstream of STIL-mediated centriole assembly to promote distal centriole elongation through recruitment of CEP295 (which loads POC1B and POC5) and through complex formation with the downstream effector PPP1R35 [PMID:28811500, PMID:30168418]. RTTN is also required for normal mitotic spindle organization, correct spindle positioning via regulation of pericentriolar γ-tubulin, NuMA, and astral microtubule dynamics [PMID:34207628], and for primary cilium structure and BMP/WNT signaling [PMID:22939636]. Biallelic RTTN mutations cause microcephaly with abnormal cortical development, consistent with its requirement for neural stem cell apico-basal polarization, rosette formation, and cell cycle fidelity in cortical organoids [PMID:22939636, PMID:39680576].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Establishing that RTTN is a cilium-associated protein whose loss disrupts cilia structure and downstream BMP/WNT signaling resolved the initial question of where and at what developmental process RTTN acts, linking it to cortical patterning defects in microcephaly patients.\",\n      \"evidence\": \"Immunofluorescence colocalization with basal bodies, patient fibroblast and NSC analysis with gene expression profiling\",\n      \"pmids\": [\"22939636\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which RTTN maintains cilium structure was not defined\",\n        \"Direct protein-protein interactions were not identified\",\n        \"Whether cilia defect is secondary to a centriolar role was untested\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Pinpointing RTTN to the inner centriolar lumen and demonstrating its direct binding to STIL, its epistatic position upstream of CEP295 in distal centriole assembly, and the functional impact of a disease-associated missense mutation answered how RTTN contributes to centriole biogenesis at a molecular level.\",\n      \"evidence\": \"Super-resolution and electron microscopy, co-immunoprecipitation, CRISPR knockout and rescue, mutant binding assays in human cells\",\n      \"pmids\": [\"28811500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the RTTN–STIL interaction is unknown\",\n        \"How RTTN activates CEP295 loading mechanistically was not resolved\",\n        \"Whether RTTN has additional partners beyond STIL at the procentriole was not tested\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identifying PPP1R35 as a downstream effector that forms a complex with RTTN extended the centriole elongation pathway and clarified that RTTN operates through at least two downstream branches (CEP295 and PPP1R35).\",\n      \"evidence\": \"Quantitative super-resolution microscopy, BioID proximity mapping, loss-of-function epistasis experiments\",\n      \"pmids\": [\"30168418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the RTTN–PPP1R35 complex is direct or bridged by additional subunits is unresolved\",\n        \"Stoichiometry and regulation of the complex during the cell cycle are unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating that RTTN depletion causes γ-tubulin dispersal, spindle multipolarity, mislocalized NuMA/p150Glued, and reduced astral microtubules established a second major function for RTTN in mitotic spindle organization and positioning, beyond centriole assembly.\",\n      \"evidence\": \"RNAi depletion with immunofluorescence and spindle positioning assays in human cells\",\n      \"pmids\": [\"34207628\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab RNAi study; independent confirmation with orthogonal depletion strategies is lacking\",\n        \"Whether spindle defects are a direct consequence of centriole structural defects or reflect a separable RTTN function is untested\",\n        \"Molecular mechanism linking RTTN to NuMA cortical recruitment is unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showing that RTTN-mutant iPSC-derived neural stem cells fail to polarize apico-basally, delay rosette self-organization, and exhibit aneuploidy and cell death in cortical organoids connected RTTN's centriolar and mitotic functions to a tissue-level developmental phenotype relevant to human microcephaly.\",\n      \"evidence\": \"CRISPR/Cas9-edited iPSC-derived cortical organoids with live imaging and immunostaining\",\n      \"pmids\": [\"39680576\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab organoid model; replication in animal models or independent iPSC lines would strengthen claims\",\n        \"Relative contributions of centriole elongation defects versus spindle positioning defects to the cortical phenotype are not delineated\",\n        \"Whether RTTN's role in rosette formation depends on primary cilia signaling or is purely centrosomal is unresolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A structural understanding of RTTN—including its domain architecture, how it bridges STIL binding to CEP295 and PPP1R35 activation, and whether its spindle-positioning function is mechanistically separable from its centriole elongation role—remains an open question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of RTTN or its complexes exists\",\n        \"Separation-of-function mutations distinguishing centriole elongation from spindle positioning roles have not been generated\",\n        \"Regulatory inputs (phosphorylation, cell-cycle-dependent degradation) are unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\n      \"RTTN–PPP1R35 complex\"\n    ],\n    \"partners\": [\n      \"STIL\",\n      \"CEP295\",\n      \"PPP1R35\",\n      \"POC1B\",\n      \"POC5\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}