{"gene":"SSNA1","run_date":"2026-06-10T07:46:41","timeline":{"discoveries":[{"year":1998,"finding":"NA14 (SSNA1) is a novel 14-kDa protein with an N-terminal acidic domain containing heptad repeats characteristic of alpha-helices forming dimeric coiled-coil structures, and an alkaline C-terminal domain. It localizes to numerous punctate nuclear structures in HeLa and 3T3 cells as determined by immunofluorescence of transiently transfected tagged protein.","method":"cDNA library screening with autoimmune serum, immunoprecipitation from cell lysates, recombinant protein antibody generation, confocal immunofluorescence microscopy of tagged transfected protein","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — immunoprecipitation and direct imaging of tagged protein in two cell lines; single lab but multiple orthogonal methods","pmids":["9430706"],"is_preprint":false},{"year":2003,"finding":"DIP13 (Chlamydomonas ortholog of human NA14/SSNA1) localizes to basal bodies, flagellar axonemes, and cytoplasmic microtubules. Anti-DIP13 antibody cross-reacted with human NA14 and stained basal bodies/flagella of human sperm cells and centrosomes of HeLa cells. Antisense suppression of DIP13 in Chlamydomonas produced multinucleate, multiflagellate cells, implicating a role in proper cell division.","method":"Specific antibody immunolocalization, cross-species immunofluorescence, antisense knockdown with cellular phenotype readout","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — antibody-based localization plus functional antisense knockdown with defined cellular phenotype; single lab","pmids":["12640030"],"is_preprint":false},{"year":2004,"finding":"Spastin (SPG4) physically interacts with the centrosomal protein NA14 (SSNA1). Spastin co-fractionates with gamma-tubulin (a centrosomal marker). Deletion of the spastin region required for binding to NA14 disrupts spastin's interaction with microtubules, suggesting NA14 acts as an adaptor to target spastin activity at the centrosome.","method":"Co-immunoprecipitation, subcellular fractionation with gamma-tubulin marker, deletion mutant analysis of binding region and microtubule interaction","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and fractionation with deletion mutant epistasis; single lab, multiple methods","pmids":["15269182"],"is_preprint":false},{"year":2008,"finding":"NA14 (SSNA1) binds to the C-terminal region of the orphan receptor TPRA40/GPR175, as confirmed by GST pull-down and co-immunoprecipitation. NA14 mediates the transport of TPRA40 from cytosol to the plasma membrane; an N-terminal deletion mutant of NA14 (GFP-NA14ΔN) that cannot bind microtubules but retains TPRA40 binding inhibited TPRA40 membrane translocation. This functional membrane transport of TPRA40 by NA14 regulates cell division of early mouse embryos.","method":"Yeast two-hybrid screening, GST pull-down, co-immunoprecipitation, fluorescence microscopy of FLAG-tagged TPRA40 translocation, GFP-NA14 deletion mutant expression in HeLa cells and mouse embryos","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding confirmed by two methods (GST pull-down and Co-IP), functional mutant analysis, in vivo embryo assay; single lab","pmids":["18459117"],"is_preprint":false},{"year":2011,"finding":"Human NA14 (SSNA1) forms a highly helical, predominantly coiled-coil structure with its N- and C-termini (residues 1-13 and 105-119) lacking preferred structure. Residues 14-104 participate in NA14 self-association via a parallel coiled-coil. The protein is insoluble and forms fibrils/oligomers. Leu83 and Leu93 are hypothesized (but not fully proven) to mediate interactions with spastin and microtubules. Two conserved Tyr residues may stabilize the structure via Glu-COO⁻ |||HO-Tyr H-bonds.","method":"CD spectroscopy, NMR (of quintuple mutant and wild-type in detergent micelles), urea and thermal denaturation, site-directed mutagenesis of Cys and Leu residues","journal":"Protein engineering, design & selection : PEDS","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR and CD structural characterization with mutagenesis; single lab, multiple biophysical methods","pmids":["22008182"],"is_preprint":false},{"year":2012,"finding":"The T. brucei orthologue of SSNA1 (TbDIP13) self-assembles into fibril-like structures both in vitro and in vivo, and partially co-localizes with acetylated α-tubulin in procyclic-stage parasites. Deletion of TbDIP13 in bloodstream and procyclic stages had little effect on growth or morphology, indicating functional redundancy or a role in an alternative life-cycle stage.","method":"Comparative proteomics for interacting partners, in vitro and in vivo self-assembly assays, immunofluorescence co-localization with acetylated α-tubulin, gene deletion","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — self-assembly demonstrated in vitro and in vivo, gene deletion with defined phenotype readout; single lab with multiple methods","pmids":["22363749"],"is_preprint":false},{"year":2014,"finding":"NA14 (SSNA1) localizes specifically to centrioles in HeLa cells and rat cortical neurons. Stable NA14 knockdown dramatically impairs cell division, particularly cytokinesis. Overexpression of NA14 in neurons significantly increases axon outgrowth and branching and enhances neuronal differentiation. NA14 is proposed to act as an adaptor regulating spastin localization to centrosomes.","method":"Immunofluorescence of endogenous proteins, stable shRNA knockdown with cytokinesis phenotype readout, neuronal overexpression with axon outgrowth and branching quantification","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined cytokinesis phenotype and OE with neuronal phenotype; single lab, multiple cell-type experiments","pmids":["25390646"],"is_preprint":false},{"year":2016,"finding":"An SSNA1/DIP13 homologue in Toxoplasma gondii localizes to the conoid (apical complex) in mature and dividing cells and to the basal complex in elongating daughter cells during division. The protein self-associates into higher-order structures both in vitro and in vivo; overexpression impairs parasite division. The protein is dispensable for in vitro parasite growth.","method":"Fluorescence microscopy localization, in vitro and in vivo self-assembly assays, overexpression with division phenotype readout, conditional gene disruption","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization and in vitro/in vivo self-assembly with functional overexpression phenotype; single lab","pmids":["27324377"],"is_preprint":false},{"year":2021,"finding":"SSNA1 directly modulates all parameters of microtubule dynamic instability in vitro: it slows rates of growth, shrinkage, and catastrophe, and promotes rescue. SSNA1 forms stretches along growing microtubule ends and binds cooperatively to the microtubule lattice. SSNA1 is enriched at microtubule damage sites (both naturally occurring and induced by the severing enzyme spastin), and its binding protects microtubules against spastin-mediated severing.","method":"In vitro reconstitution with purified proteins, TIRF microscopy, quantitative analysis of dynamic instability parameters, microtubule severing assays with spastin","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified proteins, multiple orthogonal quantitative assays (growth, shrinkage, catastrophe, rescue, severing protection), direct observation by TIRF microscopy","pmids":["34970964"],"is_preprint":false},{"year":2024,"finding":"SSNA1 (C. elegans SSNA-1) forms an anti-parallel coiled-coil whose self-assembly is facilitated by 16 C-terminal residue overhangs that dock on the adjacent coiled-coil to form a triple-stranded helical junction. The microtubule-binding region resides within this triple-stranded junction, indicating that self-assembly creates hubs for effective microtubule interaction. SSNA-1 deletion in C. elegans reduces embryonic viability and causes multipolar spindles during cell division; impairing self-assembly has a comparable effect on viability as knockout.","method":"Cryo-EM structure determination (4.55 Å resolution), C. elegans genetic knockout and self-assembly-deficient mutants with embryonic viability and spindle phenotype readouts","journal":"bioRxiv (preprint); subsequently published in Nature Communications (2025)","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with mutagenesis validation and in vivo genetic epistasis; replicated in peer-reviewed publication","pmids":["39803484","40804232"],"is_preprint":false},{"year":2025,"finding":"SAS-1 (C2CD3 homologue) is essential for SSNA-1 localization to centrioles during oogenesis and to the transition zone during ciliogenesis in C. elegans. SSNA-1 localizes next to the SAS-1 C-terminus in centriole architecture. In a heterologous human cell assay, SAS-1 recruits SSNA-1 to microtubules, establishing a genetic epistasis relationship where SAS-1 acts upstream of SSNA-1 for centriole/cilium localization.","method":"U-Ex-STED super-resolution imaging, null allele genetics in C. elegans, molecular epistasis experiments with null alleles of both components, heterologous human cell recruitment assay","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — molecular epistasis with null alleles plus super-resolution imaging and cross-species heterologous assay; multiple orthogonal methods","pmids":["41124206"],"is_preprint":false},{"year":2025,"finding":"SSNA1 localizes to the distal lumen of centrioles and basal bodies in a ring-like 9-fold symmetric configuration, apart from centriolar microtubules. A C2CD3–SSNA1–LRRCC1 hierarchical targeting network operates in the distal lumen. SSNA1 promotes cilia assembly by facilitating CP110 removal. Contrary to previous reports, KO-validated antibody and microtubule co-pelleting assays show SSNA1 does not bind microtubules in vitro, and it does not reside in the nucleus, midbody, or ciliary axoneme. SSNA1 is dispensable for cell division, overall centriole organization, and duplication.","method":"KO-validated antibody immunofluorescence, super-resolution imaging with expansion microscopy (ExM), microtubule co-pelleting assays with tag-free SSNA1 and oligomerization-deficient mutants, KO analysis of ciliogenesis and CP110 removal","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO-validated antibody, super-resolution imaging, and biochemical pelleting assays; preprint, single lab, but multiple orthogonal methods; contradicts some prior findings","pmids":[],"is_preprint":true},{"year":2025,"finding":"SSNA1 is part of a distal luminal ring network (C2CD3/SFI1/centrin-2/CEP135/NA14) in the centriole. C2CD3 depletion destabilizes this luminal ring network. SSNA1 (NA14) is identified as a component of the ~100 nm luminal ring structure at the distal centriole by U-ExM and cryo-ET structural analysis.","method":"Ultrastructure Expansion Microscopy (U-ExM), iterative U-ExM, in situ cryo-electron tomography, C2CD3 depletion and network component analysis","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — cryo-ET and U-ExM structural evidence placing SSNA1 in the luminal ring; preprint, single lab","pmids":[],"is_preprint":true},{"year":2026,"finding":"SSNA1 binding increases microtubule rigidity and resistance to breakage under kinesin-driven gliding and microfluidic flow forces. SSNA1 localizes to microtubule damage sites and inhibits incorporation of new tubulin dimers at those sites, thereby blocking lattice self-repair. Conversely, SSNA1 does not recognize damage sites that have been repaired by tubulin incorporation. Thus SSNA1 reinforces mechanical strength of microtubules without promoting self-repair.","method":"In vitro reconstitution with purified proteins, TIRF microscopy, kinesin-driven gliding assays, microfluidic flow assays for microtubule mechanics, tubulin incorporation assays at damage sites","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal force assays; preprint, single lab, extends prior eLife findings","pmids":["41648615"],"is_preprint":true}],"current_model":"SSNA1/NA14 is a small coiled-coil protein that self-assembles into fibrillar structures and functions primarily at microtubule-based structures: it binds cooperatively to microtubule lattices and ends (stabilizing dynamics, slowing catastrophe, promoting rescue), acts as a sensor and mechanical reinforcer of microtubule damage sites, localizes to centrioles (specifically the distal luminal ring) where self-assembly—facilitated by C-terminal triple-stranded helical junctions—is required for effective microtubule interaction and centriole stability, is recruited to centrioles by SAS-1/C2CD3 upstream in a C2CD3–SSNA1–LRRCC1 hierarchy, promotes ciliogenesis via CP110 removal, and acts as an adaptor for the microtubule-severing AAA-ATPase spastin at the centrosome, with loss of function causing cytokinesis defects and multipolar spindles."},"narrative":{"mechanistic_narrative":"SSNA1 (NA14/DIP13) is a small coiled-coil protein that self-assembles into fibrillar higher-order structures and functions at microtubule-based and centriolar structures to support cell division and ciliogenesis [PMID:22008182, PMID:25390646, PMID:39803484, PMID:40804232]. The protein forms a predominantly coiled-coil fold in which a central self-association region drives oligomerization, and structural work establishes an anti-parallel coiled-coil whose C-terminal residue overhangs dock onto adjacent molecules to form triple-stranded helical junctions; this self-assembly creates the hubs required for effective microtubule interaction, and impairing self-assembly phenocopies loss of the gene [PMID:22008182, PMID:39803484, PMID:40804232]. In reconstituted systems SSNA1 binds cooperatively along the microtubule lattice and growing ends and modulates all parameters of dynamic instability—slowing growth, shrinkage, and catastrophe while promoting rescue—and it becomes enriched at microtubule damage sites where it protects against spastin-mediated severing, increases lattice rigidity, and blocks incorporation of new tubulin to reinforce mechanical strength rather than promote repair [PMID:34970964, PMID:41648615]. At centrioles SSNA1 occupies a distal luminal ring in a 9-fold symmetric configuration as part of a C2CD3/SAS-1–dependent luminal network, is recruited there upstream by SAS-1/C2CD3 within a C2CD3–SSNA1–LRRCC1 targeting hierarchy, and promotes cilia assembly by facilitating CP110 removal [PMID:41124206]. SSNA1 acts as an adaptor for the microtubule-severing AAA-ATPase spastin at the centrosome, and its loss impairs cell division, producing cytokinesis defects and multipolar spindles [PMID:15269182, PMID:25390646, PMID:39803484, PMID:40804232]. Across diverse eukaryotes, orthologs localize to basal bodies, flagella, conoid, and cytoplasmic microtubules and their disruption perturbs cell division, indicating a conserved role at microtubule-organizing structures [PMID:12640030, PMID:22363749, PMID:27324377].","teleology":[{"year":1998,"claim":"Established SSNA1/NA14 as a discrete small protein with a coiled-coil-forming architecture, defining the structural basis for all later self-assembly work.","evidence":"cDNA cloning from autoimmune serum, immunoprecipitation, and immunofluorescence of tagged protein in HeLa and 3T3 cells","pmids":["9430706"],"confidence":"Medium","gaps":["Punctate nuclear localization of tagged protein was later contradicted by KO-validated imaging","No microtubule or centriole link yet established"]},{"year":2003,"claim":"Connected the protein to microtubule-organizing structures and cell division by showing the Chlamydomonas ortholog at basal bodies, axonemes, and microtubules with division defects on knockdown.","evidence":"Antibody immunolocalization, cross-species staining of human cells, and antisense suppression in Chlamydomonas","pmids":["12640030"],"confidence":"Medium","gaps":["Antisense phenotype not mechanistically dissected","Direct microtubule binding not tested biochemically"]},{"year":2004,"claim":"Identified SSNA1 as a centrosomal adaptor that physically engages the severing enzyme spastin, framing its functional partnership with microtubule remodeling machinery.","evidence":"Co-immunoprecipitation, gamma-tubulin co-fractionation, and deletion-mutant binding analysis","pmids":["15269182"],"confidence":"Medium","gaps":["Adaptor model inferred from binding/fractionation, not direct recruitment assay","Functional consequence of spastin targeting not measured here"]},{"year":2008,"claim":"Reported a separable microtubule-independent function—binding and plasma-membrane transport of the orphan receptor TPRA40/GPR175—via an N-terminal-deletion mutant that uncouples receptor binding from microtubule binding.","evidence":"Yeast two-hybrid, GST pull-down, co-IP, and translocation assays in HeLa cells and mouse embryos","pmids":["18459117"],"confidence":"Medium","gaps":["TPRA40 transport role not corroborated by later structural/centriolar studies","Single-lab finding without independent replication"]},{"year":2011,"claim":"Defined the biophysical basis of self-association, mapping the parallel coiled-coil self-association region and candidate residues for spastin/microtubule contacts.","evidence":"CD spectroscopy, NMR, denaturation studies, and site-directed mutagenesis","pmids":["22008182"],"confidence":"Medium","gaps":["Leu83/Leu93 contribution to spastin/microtubule binding hypothesized but not proven","Coiled-coil orientation later revised to anti-parallel"]},{"year":2012,"claim":"Demonstrated that self-assembly into fibrils is an intrinsic, conserved property of the protein family, here for the T. brucei ortholog co-localizing with acetylated tubulin.","evidence":"In vitro and in vivo self-assembly assays, immunofluorescence, and gene deletion in T. brucei","pmids":["22363749"],"confidence":"Medium","gaps":["Deletion produced little phenotype, leaving functional role unresolved in this organism","Direct microtubule binding not biochemically tested"]},{"year":2014,"claim":"Localized SSNA1 to centrioles in human cells and neurons and linked its loss to cytokinesis failure while overexpression drives axon outgrowth, establishing cell-type-spanning division/morphogenesis roles.","evidence":"Endogenous immunofluorescence, stable shRNA knockdown, and neuronal overexpression with quantified phenotypes","pmids":["25390646"],"confidence":"Medium","gaps":["Cytokinesis-essential role later disputed by KO-validated study","Mechanism linking centriole localization to neuronal outgrowth unresolved"]},{"year":2016,"claim":"Extended conserved self-assembly and division-modulating function to the Toxoplasma conoid/basal complex, reinforcing a pan-eukaryotic role at apical microtubule-organizing structures.","evidence":"Fluorescence localization, in vitro/in vivo self-assembly, overexpression, and conditional disruption in T. gondii","pmids":["27324377"],"confidence":"Medium","gaps":["Protein dispensable for in vitro growth, leaving essential function unclear","No structural mechanism for self-association defined here"]},{"year":2021,"claim":"Provided definitive in vitro evidence that SSNA1 directly regulates microtubule dynamic instability and protects against spastin severing, resolving its biochemical activity on microtubules.","evidence":"In vitro reconstitution with purified proteins, TIRF microscopy, and severing assays","pmids":["34970964"],"confidence":"High","gaps":["In vitro lattice binding later contested by KO-validated co-pelleting assays in another study","Cellular contribution of damage-site enrichment not yet quantified"]},{"year":2024,"claim":"Solved the self-assembly architecture by cryo-EM, showing C-terminal overhangs form triple-stranded helical junctions that house the microtubule-binding region, mechanistically coupling self-assembly to function in vivo.","evidence":"Cryo-EM structure (4.55 Å) with C. elegans knockout and self-assembly-deficient mutants scored for viability and spindle phenotypes","pmids":["39803484","40804232"],"confidence":"High","gaps":["Resolution limits atomic detail of the junction","How self-assembly hubs engage centriolar versus cytoplasmic microtubules not separated"]},{"year":2025,"claim":"Placed SSNA1 in a defined centriolar targeting hierarchy and luminal ring, showing SAS-1/C2CD3 recruits it upstream of LRRCC1 and that it promotes ciliogenesis via CP110 removal, while challenging earlier microtubule-binding and nuclear/cytokinesis claims.","evidence":"Super-resolution/expansion microscopy, cryo-ET, null-allele epistasis in C. elegans, heterologous recruitment assays, and KO-validated antibody/co-pelleting assays","pmids":["41124206"],"confidence":"High","gaps":["Direct in vitro microtubule binding remains contested between datasets (preprint co-pelleting vs reconstitution)","Molecular mechanism by which SSNA1 drives CP110 removal undefined"]},{"year":2026,"claim":"Refined the microtubule-protection mechanism, showing SSNA1 mechanically reinforces lattices and blocks tubulin re-incorporation at damage sites rather than promoting self-repair.","evidence":"In vitro reconstitution with TIRF, kinesin-gliding, microfluidic-flow mechanics, and damage-site tubulin incorporation assays (preprint)","pmids":["41648615"],"confidence":"Medium","gaps":["Preprint, single lab","In vivo relevance of mechanical reinforcement not established"]},{"year":null,"claim":"Whether SSNA1's in vitro microtubule lattice binding and dynamics regulation reflect its principal in-cell function, or whether its dominant cellular role is as a centriolar distal-luminal ring component recruited by C2CD3, remains unresolved.","evidence":"Direct conflict between reconstitution data and KO-validated cellular co-pelleting/localization data","pmids":[],"confidence":"Medium","gaps":["No single study reconciles microtubule-binding and luminal-ring models","Substrate/mechanism of CP110 removal unknown","Spastin-adaptor role not retested with KO-validated reagents"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[8,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,6]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[9,13]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[1,2,6]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,5,8]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[10,11]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6,9]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[10,11]}],"complexes":["centriole distal luminal ring (C2CD3/SFI1/centrin-2/CEP135/NA14)"],"partners":["SPAST","C2CD3","LRRCC1","TPRA40"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43805","full_name":"Microtubule nucleation factor SSNA1","aliases":["Nuclear autoantigen of 14 kDa","Sjoegren syndrome nuclear autoantigen 1"],"length_aa":119,"mass_kda":13.6,"function":"Microtubule-binding protein which stabilizes dynamic microtubules by slowing growth and shrinkage at both plus and minus ends and serves as a sensor of microtubule damage, protecting microtubules from the microtubule-severing enzyme SPAST (PubMed:34970964). Induces microtubule branching which is mediated by the formation of long SSNA1 fibrils which guide microtubule protofilaments to split apart from the mother microtubule and form daughter microtubules (By similarity). Plays a role in axon outgrowth and branching (PubMed:25390646). Required for cell division (PubMed:25390646)","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome, centriole; Midbody; Cytoplasm, cytoskeleton, flagellum basal body; Cytoplasm, cytoskeleton, flagellum axoneme; Cell projection, axon","url":"https://www.uniprot.org/uniprotkb/O43805/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SSNA1","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SSNA1","total_profiled":1310},"omim":[{"mim_id":"616720","title":"MYASTHENIC SYNDROME, CONGENITAL, 19; CMS19","url":"https://www.omim.org/entry/616720"},{"mim_id":"610882","title":"SS NUCLEAR AUTOANTIGEN 1; SSNA1","url":"https://www.omim.org/entry/610882"},{"mim_id":"604277","title":"SPASTIN; SPAST","url":"https://www.omim.org/entry/604277"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Basal body","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SSNA1"},"hgnc":{"alias_symbol":["NA14","N14"],"prev_symbol":[]},"alphafold":{"accession":"O43805","domains":[{"cath_id":"1.20.5","chopping":"1-73","consensus_level":"medium","plddt":97.0499,"start":1,"end":73}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43805","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43805-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43805-F1-predicted_aligned_error_v6.png","plddt_mean":93.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SSNA1","jax_strain_url":"https://www.jax.org/strain/search?query=SSNA1"},"sequence":{"accession":"O43805","fasta_url":"https://rest.uniprot.org/uniprotkb/O43805.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43805/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43805"}},"corpus_meta":[{"pmid":"11518718","id":"PMC_11518718","title":"Murine notch homologs (N1-4) undergo 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Replication of the backcross test and molecular characterization of the N14 locus.","date":"1998","source":"Genetica","url":"https://pubmed.ncbi.nlm.nih.gov/9949700","citation_count":13,"is_preprint":false},{"pmid":"36940584","id":"PMC_36940584","title":"Production of acetone, butanol, and ethanol by electro-fermentation with Clostridium saccharoperbutylacetonicum N1-4.","date":"2023","source":"Bioelectrochemistry (Amsterdam, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/36940584","citation_count":12,"is_preprint":false},{"pmid":"22008182","id":"PMC_22008182","title":"Characterization of the structure and self-recognition of the human centrosomal protein NA14: implications for stability and function.","date":"2011","source":"Protein engineering, design & selection : PEDS","url":"https://pubmed.ncbi.nlm.nih.gov/22008182","citation_count":11,"is_preprint":false},{"pmid":"32103460","id":"PMC_32103460","title":"Investigation of secondary metabolism in the industrial butanol 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direct production of acetone-butanol-ethanol from native starches using granular starch hydrolyzing enzyme by Clostridium saccharoperbutylacetonicum N1-4.","date":"2013","source":"Applied biochemistry and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/24272773","citation_count":7,"is_preprint":false},{"pmid":"22999358","id":"PMC_22999358","title":"Decreased hydrogen production leads to selective butanol production in co-cultures of Clostridium thermocellum and Clostridium saccharoperbutylacetonicum strain N1-4.","date":"2012","source":"Journal of bioscience and bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/22999358","citation_count":7,"is_preprint":false},{"pmid":"33803393","id":"PMC_33803393","title":"Effect of Dietary Supplementation of Immunobiotic Lactiplantibacillusplantarum N14 Fermented Rakkyo (Allium chinense) Pickled Juice on the Immunocompetence and Production Performance of Pigs.","date":"2021","source":"Animals : an open access journal from 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The Japanese journal of clinical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/7511184","citation_count":0,"is_preprint":false},{"pmid":"1318860","id":"PMC_1318860","title":"[Clinical significance of N-14 antibody (ELISA) in diagnosis of non-A, non-B liver disease].","date":"1992","source":"Fukuoka igaku zasshi = Hukuoka acta medica","url":"https://pubmed.ncbi.nlm.nih.gov/1318860","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.28.648957","title":"SSNA1 organizes the distal luminal centriolar network and promotes ciliogenesis without microtubule association","date":"2025-04-28","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.28.648957","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.17.660204","title":"The Luminal Ring Protein C2CD3 Acts as a Radial In-to-Out Organizer of the Distal Centriole and Appendages","date":"2025-06-18","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.17.660204","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.05.29.655717","title":"Visualizing the Chronicle of Multiple Cell Fate using a Near-IR Dual-RNA/DNA-Targeting Probe","date":"2025-06-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.29.655717","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.29.24311191","title":"Clinical Response to fMRI-guided Compared to Non-Image Guided rTMS in Depression and PTSD: A Randomized Trial","date":"2024-07-31","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.29.24311191","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":29005,"output_tokens":4216,"usd":0.075127,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12041,"output_tokens":4145,"usd":0.081915,"stage2_stop_reason":"end_turn"},"total_usd":0.157042,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"NA14 (SSNA1) is a novel 14-kDa protein with an N-terminal acidic domain containing heptad repeats characteristic of alpha-helices forming dimeric coiled-coil structures, and an alkaline C-terminal domain. It localizes to numerous punctate nuclear structures in HeLa and 3T3 cells as determined by immunofluorescence of transiently transfected tagged protein.\",\n      \"method\": \"cDNA library screening with autoimmune serum, immunoprecipitation from cell lysates, recombinant protein antibody generation, confocal immunofluorescence microscopy of tagged transfected protein\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunoprecipitation and direct imaging of tagged protein in two cell lines; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"9430706\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"DIP13 (Chlamydomonas ortholog of human NA14/SSNA1) localizes to basal bodies, flagellar axonemes, and cytoplasmic microtubules. Anti-DIP13 antibody cross-reacted with human NA14 and stained basal bodies/flagella of human sperm cells and centrosomes of HeLa cells. Antisense suppression of DIP13 in Chlamydomonas produced multinucleate, multiflagellate cells, implicating a role in proper cell division.\",\n      \"method\": \"Specific antibody immunolocalization, cross-species immunofluorescence, antisense knockdown with cellular phenotype readout\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — antibody-based localization plus functional antisense knockdown with defined cellular phenotype; single lab\",\n      \"pmids\": [\"12640030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Spastin (SPG4) physically interacts with the centrosomal protein NA14 (SSNA1). Spastin co-fractionates with gamma-tubulin (a centrosomal marker). Deletion of the spastin region required for binding to NA14 disrupts spastin's interaction with microtubules, suggesting NA14 acts as an adaptor to target spastin activity at the centrosome.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation with gamma-tubulin marker, deletion mutant analysis of binding region and microtubule interaction\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and fractionation with deletion mutant epistasis; single lab, multiple methods\",\n      \"pmids\": [\"15269182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NA14 (SSNA1) binds to the C-terminal region of the orphan receptor TPRA40/GPR175, as confirmed by GST pull-down and co-immunoprecipitation. NA14 mediates the transport of TPRA40 from cytosol to the plasma membrane; an N-terminal deletion mutant of NA14 (GFP-NA14ΔN) that cannot bind microtubules but retains TPRA40 binding inhibited TPRA40 membrane translocation. This functional membrane transport of TPRA40 by NA14 regulates cell division of early mouse embryos.\",\n      \"method\": \"Yeast two-hybrid screening, GST pull-down, co-immunoprecipitation, fluorescence microscopy of FLAG-tagged TPRA40 translocation, GFP-NA14 deletion mutant expression in HeLa cells and mouse embryos\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding confirmed by two methods (GST pull-down and Co-IP), functional mutant analysis, in vivo embryo assay; single lab\",\n      \"pmids\": [\"18459117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Human NA14 (SSNA1) forms a highly helical, predominantly coiled-coil structure with its N- and C-termini (residues 1-13 and 105-119) lacking preferred structure. Residues 14-104 participate in NA14 self-association via a parallel coiled-coil. The protein is insoluble and forms fibrils/oligomers. Leu83 and Leu93 are hypothesized (but not fully proven) to mediate interactions with spastin and microtubules. Two conserved Tyr residues may stabilize the structure via Glu-COO⁻ |||HO-Tyr H-bonds.\",\n      \"method\": \"CD spectroscopy, NMR (of quintuple mutant and wild-type in detergent micelles), urea and thermal denaturation, site-directed mutagenesis of Cys and Leu residues\",\n      \"journal\": \"Protein engineering, design & selection : PEDS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR and CD structural characterization with mutagenesis; single lab, multiple biophysical methods\",\n      \"pmids\": [\"22008182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The T. brucei orthologue of SSNA1 (TbDIP13) self-assembles into fibril-like structures both in vitro and in vivo, and partially co-localizes with acetylated α-tubulin in procyclic-stage parasites. Deletion of TbDIP13 in bloodstream and procyclic stages had little effect on growth or morphology, indicating functional redundancy or a role in an alternative life-cycle stage.\",\n      \"method\": \"Comparative proteomics for interacting partners, in vitro and in vivo self-assembly assays, immunofluorescence co-localization with acetylated α-tubulin, gene deletion\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — self-assembly demonstrated in vitro and in vivo, gene deletion with defined phenotype readout; single lab with multiple methods\",\n      \"pmids\": [\"22363749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NA14 (SSNA1) localizes specifically to centrioles in HeLa cells and rat cortical neurons. Stable NA14 knockdown dramatically impairs cell division, particularly cytokinesis. Overexpression of NA14 in neurons significantly increases axon outgrowth and branching and enhances neuronal differentiation. NA14 is proposed to act as an adaptor regulating spastin localization to centrosomes.\",\n      \"method\": \"Immunofluorescence of endogenous proteins, stable shRNA knockdown with cytokinesis phenotype readout, neuronal overexpression with axon outgrowth and branching quantification\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined cytokinesis phenotype and OE with neuronal phenotype; single lab, multiple cell-type experiments\",\n      \"pmids\": [\"25390646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"An SSNA1/DIP13 homologue in Toxoplasma gondii localizes to the conoid (apical complex) in mature and dividing cells and to the basal complex in elongating daughter cells during division. The protein self-associates into higher-order structures both in vitro and in vivo; overexpression impairs parasite division. The protein is dispensable for in vitro parasite growth.\",\n      \"method\": \"Fluorescence microscopy localization, in vitro and in vivo self-assembly assays, overexpression with division phenotype readout, conditional gene disruption\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization and in vitro/in vivo self-assembly with functional overexpression phenotype; single lab\",\n      \"pmids\": [\"27324377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SSNA1 directly modulates all parameters of microtubule dynamic instability in vitro: it slows rates of growth, shrinkage, and catastrophe, and promotes rescue. SSNA1 forms stretches along growing microtubule ends and binds cooperatively to the microtubule lattice. SSNA1 is enriched at microtubule damage sites (both naturally occurring and induced by the severing enzyme spastin), and its binding protects microtubules against spastin-mediated severing.\",\n      \"method\": \"In vitro reconstitution with purified proteins, TIRF microscopy, quantitative analysis of dynamic instability parameters, microtubule severing assays with spastin\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified proteins, multiple orthogonal quantitative assays (growth, shrinkage, catastrophe, rescue, severing protection), direct observation by TIRF microscopy\",\n      \"pmids\": [\"34970964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SSNA1 (C. elegans SSNA-1) forms an anti-parallel coiled-coil whose self-assembly is facilitated by 16 C-terminal residue overhangs that dock on the adjacent coiled-coil to form a triple-stranded helical junction. The microtubule-binding region resides within this triple-stranded junction, indicating that self-assembly creates hubs for effective microtubule interaction. SSNA-1 deletion in C. elegans reduces embryonic viability and causes multipolar spindles during cell division; impairing self-assembly has a comparable effect on viability as knockout.\",\n      \"method\": \"Cryo-EM structure determination (4.55 Å resolution), C. elegans genetic knockout and self-assembly-deficient mutants with embryonic viability and spindle phenotype readouts\",\n      \"journal\": \"bioRxiv (preprint); subsequently published in Nature Communications (2025)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with mutagenesis validation and in vivo genetic epistasis; replicated in peer-reviewed publication\",\n      \"pmids\": [\"39803484\", \"40804232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SAS-1 (C2CD3 homologue) is essential for SSNA-1 localization to centrioles during oogenesis and to the transition zone during ciliogenesis in C. elegans. SSNA-1 localizes next to the SAS-1 C-terminus in centriole architecture. In a heterologous human cell assay, SAS-1 recruits SSNA-1 to microtubules, establishing a genetic epistasis relationship where SAS-1 acts upstream of SSNA-1 for centriole/cilium localization.\",\n      \"method\": \"U-Ex-STED super-resolution imaging, null allele genetics in C. elegans, molecular epistasis experiments with null alleles of both components, heterologous human cell recruitment assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — molecular epistasis with null alleles plus super-resolution imaging and cross-species heterologous assay; multiple orthogonal methods\",\n      \"pmids\": [\"41124206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SSNA1 localizes to the distal lumen of centrioles and basal bodies in a ring-like 9-fold symmetric configuration, apart from centriolar microtubules. A C2CD3–SSNA1–LRRCC1 hierarchical targeting network operates in the distal lumen. SSNA1 promotes cilia assembly by facilitating CP110 removal. Contrary to previous reports, KO-validated antibody and microtubule co-pelleting assays show SSNA1 does not bind microtubules in vitro, and it does not reside in the nucleus, midbody, or ciliary axoneme. SSNA1 is dispensable for cell division, overall centriole organization, and duplication.\",\n      \"method\": \"KO-validated antibody immunofluorescence, super-resolution imaging with expansion microscopy (ExM), microtubule co-pelleting assays with tag-free SSNA1 and oligomerization-deficient mutants, KO analysis of ciliogenesis and CP110 removal\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO-validated antibody, super-resolution imaging, and biochemical pelleting assays; preprint, single lab, but multiple orthogonal methods; contradicts some prior findings\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SSNA1 is part of a distal luminal ring network (C2CD3/SFI1/centrin-2/CEP135/NA14) in the centriole. C2CD3 depletion destabilizes this luminal ring network. SSNA1 (NA14) is identified as a component of the ~100 nm luminal ring structure at the distal centriole by U-ExM and cryo-ET structural analysis.\",\n      \"method\": \"Ultrastructure Expansion Microscopy (U-ExM), iterative U-ExM, in situ cryo-electron tomography, C2CD3 depletion and network component analysis\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-ET and U-ExM structural evidence placing SSNA1 in the luminal ring; preprint, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"SSNA1 binding increases microtubule rigidity and resistance to breakage under kinesin-driven gliding and microfluidic flow forces. SSNA1 localizes to microtubule damage sites and inhibits incorporation of new tubulin dimers at those sites, thereby blocking lattice self-repair. Conversely, SSNA1 does not recognize damage sites that have been repaired by tubulin incorporation. Thus SSNA1 reinforces mechanical strength of microtubules without promoting self-repair.\",\n      \"method\": \"In vitro reconstitution with purified proteins, TIRF microscopy, kinesin-driven gliding assays, microfluidic flow assays for microtubule mechanics, tubulin incorporation assays at damage sites\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal force assays; preprint, single lab, extends prior eLife findings\",\n      \"pmids\": [\"41648615\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"SSNA1/NA14 is a small coiled-coil protein that self-assembles into fibrillar structures and functions primarily at microtubule-based structures: it binds cooperatively to microtubule lattices and ends (stabilizing dynamics, slowing catastrophe, promoting rescue), acts as a sensor and mechanical reinforcer of microtubule damage sites, localizes to centrioles (specifically the distal luminal ring) where self-assembly—facilitated by C-terminal triple-stranded helical junctions—is required for effective microtubule interaction and centriole stability, is recruited to centrioles by SAS-1/C2CD3 upstream in a C2CD3–SSNA1–LRRCC1 hierarchy, promotes ciliogenesis via CP110 removal, and acts as an adaptor for the microtubule-severing AAA-ATPase spastin at the centrosome, with loss of function causing cytokinesis defects and multipolar spindles.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SSNA1 (NA14/DIP13) is a small coiled-coil protein that self-assembles into fibrillar higher-order structures and functions at microtubule-based and centriolar structures to support cell division and ciliogenesis [#4, #6, #9]. The protein forms a predominantly coiled-coil fold in which a central self-association region drives oligomerization, and structural work establishes an anti-parallel coiled-coil whose C-terminal residue overhangs dock onto adjacent molecules to form triple-stranded helical junctions; this self-assembly creates the hubs required for effective microtubule interaction, and impairing self-assembly phenocopies loss of the gene [#4, #9]. In reconstituted systems SSNA1 binds cooperatively along the microtubule lattice and growing ends and modulates all parameters of dynamic instability—slowing growth, shrinkage, and catastrophe while promoting rescue—and it becomes enriched at microtubule damage sites where it protects against spastin-mediated severing, increases lattice rigidity, and blocks incorporation of new tubulin to reinforce mechanical strength rather than promote repair [#8, #13]. At centrioles SSNA1 occupies a distal luminal ring in a 9-fold symmetric configuration as part of a C2CD3/SAS-1–dependent luminal network, is recruited there upstream by SAS-1/C2CD3 within a C2CD3–SSNA1–LRRCC1 targeting hierarchy, and promotes cilia assembly by facilitating CP110 removal [#10, #11, #12]. SSNA1 acts as an adaptor for the microtubule-severing AAA-ATPase spastin at the centrosome, and its loss impairs cell division, producing cytokinesis defects and multipolar spindles [#2, #6, #9]. Across diverse eukaryotes, orthologs localize to basal bodies, flagella, conoid, and cytoplasmic microtubules and their disruption perturbs cell division, indicating a conserved role at microtubule-organizing structures [#1, #5, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established SSNA1/NA14 as a discrete small protein with a coiled-coil-forming architecture, defining the structural basis for all later self-assembly work.\",\n      \"evidence\": \"cDNA cloning from autoimmune serum, immunoprecipitation, and immunofluorescence of tagged protein in HeLa and 3T3 cells\",\n      \"pmids\": [\"9430706\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Punctate nuclear localization of tagged protein was later contradicted by KO-validated imaging\", \"No microtubule or centriole link yet established\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Connected the protein to microtubule-organizing structures and cell division by showing the Chlamydomonas ortholog at basal bodies, axonemes, and microtubules with division defects on knockdown.\",\n      \"evidence\": \"Antibody immunolocalization, cross-species staining of human cells, and antisense suppression in Chlamydomonas\",\n      \"pmids\": [\"12640030\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antisense phenotype not mechanistically dissected\", \"Direct microtubule binding not tested biochemically\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified SSNA1 as a centrosomal adaptor that physically engages the severing enzyme spastin, framing its functional partnership with microtubule remodeling machinery.\",\n      \"evidence\": \"Co-immunoprecipitation, gamma-tubulin co-fractionation, and deletion-mutant binding analysis\",\n      \"pmids\": [\"15269182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Adaptor model inferred from binding/fractionation, not direct recruitment assay\", \"Functional consequence of spastin targeting not measured here\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Reported a separable microtubule-independent function—binding and plasma-membrane transport of the orphan receptor TPRA40/GPR175—via an N-terminal-deletion mutant that uncouples receptor binding from microtubule binding.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, co-IP, and translocation assays in HeLa cells and mouse embryos\",\n      \"pmids\": [\"18459117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"TPRA40 transport role not corroborated by later structural/centriolar studies\", \"Single-lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined the biophysical basis of self-association, mapping the parallel coiled-coil self-association region and candidate residues for spastin/microtubule contacts.\",\n      \"evidence\": \"CD spectroscopy, NMR, denaturation studies, and site-directed mutagenesis\",\n      \"pmids\": [\"22008182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Leu83/Leu93 contribution to spastin/microtubule binding hypothesized but not proven\", \"Coiled-coil orientation later revised to anti-parallel\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated that self-assembly into fibrils is an intrinsic, conserved property of the protein family, here for the T. brucei ortholog co-localizing with acetylated tubulin.\",\n      \"evidence\": \"In vitro and in vivo self-assembly assays, immunofluorescence, and gene deletion in T. brucei\",\n      \"pmids\": [\"22363749\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Deletion produced little phenotype, leaving functional role unresolved in this organism\", \"Direct microtubule binding not biochemically tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Localized SSNA1 to centrioles in human cells and neurons and linked its loss to cytokinesis failure while overexpression drives axon outgrowth, establishing cell-type-spanning division/morphogenesis roles.\",\n      \"evidence\": \"Endogenous immunofluorescence, stable shRNA knockdown, and neuronal overexpression with quantified phenotypes\",\n      \"pmids\": [\"25390646\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cytokinesis-essential role later disputed by KO-validated study\", \"Mechanism linking centriole localization to neuronal outgrowth unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended conserved self-assembly and division-modulating function to the Toxoplasma conoid/basal complex, reinforcing a pan-eukaryotic role at apical microtubule-organizing structures.\",\n      \"evidence\": \"Fluorescence localization, in vitro/in vivo self-assembly, overexpression, and conditional disruption in T. gondii\",\n      \"pmids\": [\"27324377\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Protein dispensable for in vitro growth, leaving essential function unclear\", \"No structural mechanism for self-association defined here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided definitive in vitro evidence that SSNA1 directly regulates microtubule dynamic instability and protects against spastin severing, resolving its biochemical activity on microtubules.\",\n      \"evidence\": \"In vitro reconstitution with purified proteins, TIRF microscopy, and severing assays\",\n      \"pmids\": [\"34970964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro lattice binding later contested by KO-validated co-pelleting assays in another study\", \"Cellular contribution of damage-site enrichment not yet quantified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Solved the self-assembly architecture by cryo-EM, showing C-terminal overhangs form triple-stranded helical junctions that house the microtubule-binding region, mechanistically coupling self-assembly to function in vivo.\",\n      \"evidence\": \"Cryo-EM structure (4.55 Å) with C. elegans knockout and self-assembly-deficient mutants scored for viability and spindle phenotypes\",\n      \"pmids\": [\"39803484\", \"40804232\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Resolution limits atomic detail of the junction\", \"How self-assembly hubs engage centriolar versus cytoplasmic microtubules not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed SSNA1 in a defined centriolar targeting hierarchy and luminal ring, showing SAS-1/C2CD3 recruits it upstream of LRRCC1 and that it promotes ciliogenesis via CP110 removal, while challenging earlier microtubule-binding and nuclear/cytokinesis claims.\",\n      \"evidence\": \"Super-resolution/expansion microscopy, cryo-ET, null-allele epistasis in C. elegans, heterologous recruitment assays, and KO-validated antibody/co-pelleting assays\",\n      \"pmids\": [\"41124206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct in vitro microtubule binding remains contested between datasets (preprint co-pelleting vs reconstitution)\", \"Molecular mechanism by which SSNA1 drives CP110 removal undefined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Refined the microtubule-protection mechanism, showing SSNA1 mechanically reinforces lattices and blocks tubulin re-incorporation at damage sites rather than promoting self-repair.\",\n      \"evidence\": \"In vitro reconstitution with TIRF, kinesin-gliding, microfluidic-flow mechanics, and damage-site tubulin incorporation assays (preprint)\",\n      \"pmids\": [\"41648615\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, single lab\", \"In vivo relevance of mechanical reinforcement not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether SSNA1's in vitro microtubule lattice binding and dynamics regulation reflect its principal in-cell function, or whether its dominant cellular role is as a centriolar distal-luminal ring component recruited by C2CD3, remains unresolved.\",\n      \"evidence\": \"Direct conflict between reconstitution data and KO-validated cellular co-pelleting/localization data\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No single study reconciles microtubule-binding and luminal-ring models\", \"Substrate/mechanism of CP110 removal unknown\", \"Spastin-adaptor role not retested with KO-validated reagents\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [8, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [9, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [1, 2, 6]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 5, 8]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [10, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6, 9]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [10, 11]}\n    ],\n    \"complexes\": [\"centriole distal luminal ring (C2CD3/SFI1/centrin-2/CEP135/NA14)\"],\n    \"partners\": [\"SPAST\", \"C2CD3\", \"LRRCC1\", \"TPRA40\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}