{"gene":"TUBA4A","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2014,"finding":"TUBA4A mutants (identified in familial ALS patients) destabilize the microtubule network and diminish its repolymerization capability, as demonstrated by functional microtubule repolymerization assays in cells expressing ALS-associated TUBA4A variants.","method":"Microtubule repolymerization assay in cells expressing mutant TUBA4A","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional assay replicated across multiple ALS-associated variants, foundational study replicated by subsequent independent labs","pmids":["25374358"],"is_preprint":false},{"year":2018,"finding":"Excess tubulin-folding cofactor B (TBCB) leads to depolymerization and degradation of TUBA4A protein, establishing TBCB as a negative regulator of TUBA4A stability; this pathway (miR-1825/TBCB/TUBA4A) was confirmed in brain cortex tissue of ALS patients and caused motor axon defects in an in vivo model.","method":"Combined transcriptomic and proteomic analysis, protein-level validation in patient brain tissue, in vivo zebrafish/motor axon model","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (transcriptomics, proteomics, patient tissue validation, in vivo model) in single study","pmids":["30030593"],"is_preprint":false},{"year":2021,"finding":"A TUBA4A variant associated with familial FTD showed decreased TUBA4A protein abundance and disrupted α-tubulin function in a microtubule repolymerization assay; FTD-associated variants appear more localized to the N-terminus compared to ALS-associated variants, suggesting distinct pathogenic mechanisms.","method":"Immunoblotting, microtubule repolymerization assay","journal":"Neurology. Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional assay with protein quantification, single lab","pmids":["34169147"],"is_preprint":false},{"year":2022,"finding":"An N-terminal frameshift mutation in TUBA4A (p.Arg64Glyfs*90) produces mutant mRNA but no detectable truncated protein, and leads to decreased total TUBA4A mRNA and protein levels, indicating loss-of-function/haploinsufficiency as a pathogenic mechanism for N-terminal TUBA4A mutations, distinct from the dominant-negative mechanism proposed for C-terminal mutations.","method":"qPCR, immunoblotting, immunohistochemistry","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal molecular methods (qPCR + Western blot), single lab case study","pmids":["35327632"],"is_preprint":false},{"year":2023,"finding":"In silico molecular dynamics modeling of ALS-associated TUBA4A mutations (e.g., K430N, R215C, W407X) predicts structural deviations that impair GTP binding and destabilize tubulin polymerization; mutations R320C and K430N also significantly increase predicted aggregation propensity of TUBA4A relative to wild-type.","method":"Molecular dynamics simulation, molecular docking","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational prediction only, no experimental validation","pmids":["36747013"],"is_preprint":false},{"year":2024,"finding":"Knockdown of the zebrafish TUBA4A orthologue via antisense morpholino induced motor axonopathy and disturbed motor behavior in a dose-dependent manner; these phenotypes were rescued by addition of human wild-type TUBA4A mRNA, demonstrating functional conservation. Additionally, loss of TUBA4A caused significant changes in post-translational modifications of tubulin including acetylation, detyrosination, and polyglutamylation.","method":"Antisense morpholino knockdown in zebrafish, mRNA rescue, immunostaining of motor axons, motor behavior assay, antibody-based detection of tubulin PTMs","journal":"Frontiers in cellular neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with defined phenotype, dose-response, rescue with human WT mRNA, and PTM analysis as mechanistic readout","pmids":["38463699"],"is_preprint":false},{"year":2024,"finding":"The TUBA4A missense variant p.L227F causes cytoplasmic aggregation of TUBA4A protein that colocalizes with ubiquitin when overexpressed in a cellular model, and is associated with focal myofibrillar disorganization and rimmed vacuoles in patient muscle; immunofluorescence showed ubiquitin-positive TUBA4A aggregates in affected muscle fibres.","method":"Overexpression in cellular model, immunofluorescence, immunohistochemistry of patient muscle biopsy","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — cellular overexpression plus patient tissue validation with two orthogonal imaging methods, single lab","pmids":["38413182"],"is_preprint":false},{"year":2024,"finding":"Cultured fibroblasts from patients with distinct TUBA4A missense variants showed significant alterations in microtubule organization and dynamics, providing experimental evidence for pathogenicity of these variants.","method":"Microtubule organization/dynamics assay in patient-derived fibroblasts","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cellular assay in patient-derived cells for three independent variants, single study","pmids":["38884572"],"is_preprint":false},{"year":2025,"finding":"Multiple TUBA4A missense variants identified in patients with primary myopathy cause TUBA4A protein accumulation and proteinopathy (including autophagic features) in patient myofibres; in vitro investigations indicate that these substitutions cause significant protein abnormalities and differentially impact microtubule dynamics; domain specificity within TUBA4A influences both muscle involvement pattern and extent of microtubule disruption.","method":"Immunohistochemistry of patient muscle biopsies, in silico and in vitro microtubule dynamics assays","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multi-centre study with patient tissue and in vitro validation, multiple variants and orthogonal methods","pmids":["41678358"],"is_preprint":false},{"year":2026,"finding":"A mouse model carrying the Tuba4a p.Gln176Pro missense mutation (ENU-confirmed by CRISPR engineering) develops ataxia, Purkinje neuron degeneration, and skeletal muscle defects with dominant inheritance, but does not show motor neuron degeneration, demonstrating cell-type-selective consequences of this TUBA4A mutation in vivo.","method":"ENU mutagenesis screen, genetic mapping, CRISPR knock-in confirmation, neuropathological and behavioral analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR-confirmed mouse model with defined cellular phenotypes, preprint not yet peer-reviewed","pmids":["41889878"],"is_preprint":true},{"year":2011,"finding":"A missense mutation in the mouse Tuba1 gene (encoding TUBA1/TUBA4A ortholog; aspartate to glycine substitution) causes behavioral abnormalities including hyperactivity and inattention to novel objects, with abnormal brain development, establishing a neurodevelopmental role for this α-tubulin in vivo.","method":"ENU mutagenesis, behavioral testing, brain morphological analysis, pharmacological challenge","journal":"Behavioural brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mutation with defined behavioral and morphological phenotype, single lab","pmids":["22101068"],"is_preprint":false}],"current_model":"TUBA4A encodes an α-tubulin isotype that incorporates into microtubules and is critical for microtubule network stability and repolymerization; disease-associated missense mutations (concentrated at the C-terminus for ALS/FTD, N-terminus for FTD) destabilize microtubules via dominant-negative mechanisms or cause haploinsufficiency, TUBA4A protein stability is negatively regulated by tubulin-folding cofactor B (TBCB), loss of TUBA4A alters tubulin post-translational modifications (acetylation, detyrosination, polyglutamylation), and certain mutations cause cytoplasmic protein aggregation with ubiquitin co-localization, collectively linking TUBA4A dysfunction to motor neuron disease, frontotemporal dementia, spastic ataxia, and myopathy."},"narrative":{"mechanistic_narrative":"TUBA4A encodes an α-tubulin isotype that incorporates into the microtubule network and is required for its stability and capacity to repolymerize, with disease-associated missense variants impairing these functions in cellular and patient-derived assays [PMID:25374358, PMID:38884572]. Its abundance is post-translationally controlled: excess tubulin-folding cofactor B (TBCB) drives depolymerization and degradation of TUBA4A through a miR-1825/TBCB/TUBA4A axis that is dysregulated in ALS patient cortex and produces motor axon defects in vivo [PMID:30030593]. Loss of TUBA4A function is conserved across species — zebrafish orthologue knockdown causes dose-dependent motor axonopathy rescuable by human wild-type mRNA, and additionally shifts the tubulin post-translational modification landscape including acetylation, detyrosination, and polyglutamylation [PMID:38463699]. Pathogenicity operates through distinct mechanisms tied to mutation position: C-terminal ALS-associated variants act dominant-negatively by destabilizing microtubules [PMID:25374358], whereas an N-terminal frameshift produces no detectable protein and reduces total TUBA4A, indicating haploinsufficiency [PMID:35327632]. A subset of missense variants instead cause cytoplasmic TUBA4A aggregation that colocalizes with ubiquitin and is accompanied by autophagic, proteinopathic muscle pathology [PMID:38413182, PMID:41678358]. These functional and structural perturbations collectively link TUBA4A dysfunction to a spectrum of disease spanning ALS/FTD, spastic ataxia, and primary myopathy, with domain specificity shaping the affected cell type and clinical pattern [PMID:34169147, PMID:41678358, PMID:41889878].","teleology":[{"year":2014,"claim":"Established that ALS-associated TUBA4A variants are not benign polymorphisms but functionally compromise the microtubule cytoskeleton, providing the first mechanistic link between this α-tubulin and motor neuron disease.","evidence":"Microtubule repolymerization assays in cells expressing multiple ALS-associated mutant TUBA4A variants","pmids":["25374358"],"confidence":"High","gaps":["Did not resolve whether the defect is dominant-negative versus loss-of-function","No in vivo or patient-tissue confirmation in this study"]},{"year":2018,"claim":"Answered how TUBA4A protein levels are controlled by identifying TBCB as a negative regulator whose excess degrades TUBA4A, embedding TUBA4A in a miR-1825/TBCB regulatory axis relevant to ALS.","evidence":"Transcriptomic/proteomic analysis with protein validation in ALS patient cortex and an in vivo motor-axon model","pmids":["30030593"],"confidence":"High","gaps":["Structural basis of TBCB-driven TUBA4A degradation not defined","Does not establish whether this axis is causal or secondary in sporadic ALS"]},{"year":2021,"claim":"Extended TUBA4A dysfunction beyond ALS to FTD and introduced the idea that mutation position correlates with phenotype, with FTD variants clustering N-terminally.","evidence":"Immunoblotting and microtubule repolymerization assay for an FTD-associated variant","pmids":["34169147"],"confidence":"Medium","gaps":["Single variant analyzed","Domain-phenotype correlation based on positional clustering rather than direct mechanistic comparison"]},{"year":2022,"claim":"Distinguished a haploinsufficiency mechanism for N-terminal mutations by showing a frameshift variant yields no detectable protein and lowers total TUBA4A, contrasting with the dominant-negative model for C-terminal variants.","evidence":"qPCR, immunoblotting, and immunohistochemistry of patient material","pmids":["35327632"],"confidence":"Medium","gaps":["Single case study","Does not test whether reduced dosage alone reproduces neuronal phenotypes"]},{"year":2023,"claim":"Proposed atomic-level explanations for variant pathogenicity, predicting impaired GTP binding, destabilized polymerization, and increased aggregation propensity for specific mutations.","evidence":"Molecular dynamics simulation and docking of ALS-associated mutations","pmids":["36747013"],"confidence":"Low","gaps":["Computational prediction with no experimental validation","Aggregation propensity predicted, not measured","GTP-binding defect not biochemically confirmed"]},{"year":2024,"claim":"Provided in vivo loss-of-function evidence and connected TUBA4A to tubulin PTM homeostasis, showing knockdown causes motor axonopathy rescuable by human wild-type mRNA and alters acetylation, detyrosination, and polyglutamylation.","evidence":"Antisense morpholino knockdown in zebrafish with mRNA rescue, motor axon imaging, behavior assay, and antibody-based PTM detection","pmids":["38463699"],"confidence":"High","gaps":["Mechanism linking TUBA4A loss to altered PTMs not defined","Morpholino-based knockdown not complemented by stable genetic null"]},{"year":2024,"claim":"Identified a proteinopathy mechanism in which a TUBA4A missense variant aggregates and colocalizes with ubiquitin, linking TUBA4A to myopathy with rimmed vacuoles and broadening the phenotypic spectrum to muscle.","evidence":"Overexpression in a cellular model with immunofluorescence and immunohistochemistry of patient muscle biopsy","pmids":["38413182"],"confidence":"Medium","gaps":["Aggregation shown by overexpression, not at endogenous levels","Single variant and single lab"]},{"year":2024,"claim":"Confirmed pathogenicity of distinct missense variants in disease-relevant patient cells by demonstrating altered microtubule organization and dynamics.","evidence":"Microtubule organization/dynamics assays in patient-derived fibroblasts for three independent variants","pmids":["38884572"],"confidence":"Medium","gaps":["Mechanistic basis (dynamics defect vs. dosage) not disentangled per variant","Single study"]},{"year":2025,"claim":"Established TUBA4A as a primary myopathy gene and demonstrated domain specificity, showing variants cause protein accumulation with autophagic proteinopathy and differentially impact microtubule dynamics depending on the affected domain.","evidence":"Immunohistochemistry of patient muscle biopsies with in silico and in vitro microtubule dynamics assays across multiple variants","pmids":["41678358"],"confidence":"Medium","gaps":["Causal link between accumulation and autophagy not resolved","Domain-to-phenotype mapping correlative"]},{"year":2026,"claim":"Demonstrated cell-type-selective consequences of a TUBA4A mutation in a mammalian model, with ataxia, Purkinje degeneration, and muscle defects but no motor neuron degeneration.","evidence":"ENU screen with CRISPR knock-in confirmation of Tuba4a p.Gln176Pro, neuropathological and behavioral analysis in mouse (preprint)","pmids":["41889878"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Molecular basis of cell-type selectivity unexplained","Single mutation modeled"]},{"year":null,"claim":"It remains unresolved why TUBA4A variants of differing position and biochemical effect produce divergent tissue tropism (motor neuron, cortical, cerebellar, muscle), and how dominant-negative, haploinsufficiency, and aggregation mechanisms are selected in each context.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model linking mutation domain to cell-type vulnerability","No structural data on mutant tubulin in assembled microtubules","Relationship between altered PTMs and disease phenotype undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,7]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,7]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6]}],"pathway":[],"complexes":["microtubule"],"partners":["TBCB"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P68366","full_name":"Tubulin alpha-4A chain","aliases":["Alpha-tubulin 1","Testis-specific alpha-tubulin","Tubulin H2-alpha","Tubulin alpha-1 chain"],"length_aa":448,"mass_kda":49.9,"function":"Tubulin is the major constituent of microtubules, a cylinder consisting of laterally associated linear protofilaments composed of alpha- and beta-tubulin heterodimers. Microtubules grow by the addition of GTP-tubulin dimers to the microtubule end, where a stabilizing cap forms. Below the cap, tubulin dimers are in GDP-bound state, owing to GTPase activity of alpha-tubulin","subcellular_location":"Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/P68366/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TUBA4A","classification":"Not Classified","n_dependent_lines":18,"n_total_lines":1208,"dependency_fraction":0.014900662251655629},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TUBA4A","total_profiled":1310},"omim":[{"mim_id":"621392","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 157; CFAP157","url":"https://www.omim.org/entry/621392"},{"mim_id":"621231","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 23; OZEMA23","url":"https://www.omim.org/entry/621231"},{"mim_id":"621226","title":"SPASTIC ATAXIA 11, AUTOSOMAL DOMINANT; SPAX11","url":"https://www.omim.org/entry/621226"},{"mim_id":"621225","title":"CONGENITAL MYOPATHY 26; CMYO26","url":"https://www.omim.org/entry/621225"},{"mim_id":"621161","title":"TUBULIN, ALPHA-1C; TUBA1C","url":"https://www.omim.org/entry/621161"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Microtubules","reliability":"Enhanced"},{"location":"Primary cilium","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":345.9},{"tissue":"tongue","ntpm":249.0}],"url":"https://www.proteinatlas.org/search/TUBA4A"},"hgnc":{"alias_symbol":["FLJ30169","H2-ALPHA"],"prev_symbol":["TUBA1"]},"alphafold":{"accession":"P68366","domains":[{"cath_id":"3.40.50.1440","chopping":"1-36_47-198_387-448","consensus_level":"medium","plddt":93.1817,"start":1,"end":448}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P68366","model_url":"https://alphafold.ebi.ac.uk/files/AF-P68366-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P68366-F1-predicted_aligned_error_v6.png","plddt_mean":91.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TUBA4A","jax_strain_url":"https://www.jax.org/strain/search?query=TUBA4A"},"sequence":{"accession":"P68366","fasta_url":"https://rest.uniprot.org/uniprotkb/P68366.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P68366/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P68366"}},"corpus_meta":[{"pmid":"25374358","id":"PMC_25374358","title":"Exome-wide rare variant analysis identifies TUBA4A mutations associated with familial ALS.","date":"2014","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/25374358","citation_count":294,"is_preprint":false},{"pmid":"28069311","id":"PMC_28069311","title":"Investigating the role of ALS genes CHCHD10 and TUBA4A in Belgian FTD-ALS spectrum patients.","date":"2016","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/28069311","citation_count":60,"is_preprint":false},{"pmid":"30030593","id":"PMC_30030593","title":"Dysregulation of a novel miR-1825/TBCB/TUBA4A pathway in sporadic and familial ALS.","date":"2018","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/30030593","citation_count":38,"is_preprint":false},{"pmid":"34169147","id":"PMC_34169147","title":"Novel TUBA4A Variant Associated With Familial Frontotemporal Dementia.","date":"2021","source":"Neurology. 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expressing mutant TUBA4A\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional assay replicated across multiple ALS-associated variants, foundational study replicated by subsequent independent labs\",\n      \"pmids\": [\"25374358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Excess tubulin-folding cofactor B (TBCB) leads to depolymerization and degradation of TUBA4A protein, establishing TBCB as a negative regulator of TUBA4A stability; this pathway (miR-1825/TBCB/TUBA4A) was confirmed in brain cortex tissue of ALS patients and caused motor axon defects in an in vivo model.\",\n      \"method\": \"Combined transcriptomic and proteomic analysis, protein-level validation in patient brain tissue, in vivo zebrafish/motor axon model\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (transcriptomics, proteomics, patient tissue validation, in vivo model) in single study\",\n      \"pmids\": [\"30030593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A TUBA4A variant associated with familial FTD showed decreased TUBA4A protein abundance and disrupted α-tubulin function in a microtubule repolymerization assay; FTD-associated variants appear more localized to the N-terminus compared to ALS-associated variants, suggesting distinct pathogenic mechanisms.\",\n      \"method\": \"Immunoblotting, microtubule repolymerization assay\",\n      \"journal\": \"Neurology. Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional assay with protein quantification, single lab\",\n      \"pmids\": [\"34169147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"An N-terminal frameshift mutation in TUBA4A (p.Arg64Glyfs*90) produces mutant mRNA but no detectable truncated protein, and leads to decreased total TUBA4A mRNA and protein levels, indicating loss-of-function/haploinsufficiency as a pathogenic mechanism for N-terminal TUBA4A mutations, distinct from the dominant-negative mechanism proposed for C-terminal mutations.\",\n      \"method\": \"qPCR, immunoblotting, immunohistochemistry\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal molecular methods (qPCR + Western blot), single lab case study\",\n      \"pmids\": [\"35327632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In silico molecular dynamics modeling of ALS-associated TUBA4A mutations (e.g., K430N, R215C, W407X) predicts structural deviations that impair GTP binding and destabilize tubulin polymerization; mutations R320C and K430N also significantly increase predicted aggregation propensity of TUBA4A relative to wild-type.\",\n      \"method\": \"Molecular dynamics simulation, molecular docking\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational prediction only, no experimental validation\",\n      \"pmids\": [\"36747013\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Knockdown of the zebrafish TUBA4A orthologue via antisense morpholino induced motor axonopathy and disturbed motor behavior in a dose-dependent manner; these phenotypes were rescued by addition of human wild-type TUBA4A mRNA, demonstrating functional conservation. Additionally, loss of TUBA4A caused significant changes in post-translational modifications of tubulin including acetylation, detyrosination, and polyglutamylation.\",\n      \"method\": \"Antisense morpholino knockdown in zebrafish, mRNA rescue, immunostaining of motor axons, motor behavior assay, antibody-based detection of tubulin PTMs\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with defined phenotype, dose-response, rescue with human WT mRNA, and PTM analysis as mechanistic readout\",\n      \"pmids\": [\"38463699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The TUBA4A missense variant p.L227F causes cytoplasmic aggregation of TUBA4A protein that colocalizes with ubiquitin when overexpressed in a cellular model, and is associated with focal myofibrillar disorganization and rimmed vacuoles in patient muscle; immunofluorescence showed ubiquitin-positive TUBA4A aggregates in affected muscle fibres.\",\n      \"method\": \"Overexpression in cellular model, immunofluorescence, immunohistochemistry of patient muscle biopsy\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — cellular overexpression plus patient tissue validation with two orthogonal imaging methods, single lab\",\n      \"pmids\": [\"38413182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cultured fibroblasts from patients with distinct TUBA4A missense variants showed significant alterations in microtubule organization and dynamics, providing experimental evidence for pathogenicity of these variants.\",\n      \"method\": \"Microtubule organization/dynamics assay in patient-derived fibroblasts\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cellular assay in patient-derived cells for three independent variants, single study\",\n      \"pmids\": [\"38884572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Multiple TUBA4A missense variants identified in patients with primary myopathy cause TUBA4A protein accumulation and proteinopathy (including autophagic features) in patient myofibres; in vitro investigations indicate that these substitutions cause significant protein abnormalities and differentially impact microtubule dynamics; domain specificity within TUBA4A influences both muscle involvement pattern and extent of microtubule disruption.\",\n      \"method\": \"Immunohistochemistry of patient muscle biopsies, in silico and in vitro microtubule dynamics assays\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multi-centre study with patient tissue and in vitro validation, multiple variants and orthogonal methods\",\n      \"pmids\": [\"41678358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A mouse model carrying the Tuba4a p.Gln176Pro missense mutation (ENU-confirmed by CRISPR engineering) develops ataxia, Purkinje neuron degeneration, and skeletal muscle defects with dominant inheritance, but does not show motor neuron degeneration, demonstrating cell-type-selective consequences of this TUBA4A mutation in vivo.\",\n      \"method\": \"ENU mutagenesis screen, genetic mapping, CRISPR knock-in confirmation, neuropathological and behavioral analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR-confirmed mouse model with defined cellular phenotypes, preprint not yet peer-reviewed\",\n      \"pmids\": [\"41889878\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A missense mutation in the mouse Tuba1 gene (encoding TUBA1/TUBA4A ortholog; aspartate to glycine substitution) causes behavioral abnormalities including hyperactivity and inattention to novel objects, with abnormal brain development, establishing a neurodevelopmental role for this α-tubulin in vivo.\",\n      \"method\": \"ENU mutagenesis, behavioral testing, brain morphological analysis, pharmacological challenge\",\n      \"journal\": \"Behavioural brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mutation with defined behavioral and morphological phenotype, single lab\",\n      \"pmids\": [\"22101068\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TUBA4A encodes an α-tubulin isotype that incorporates into microtubules and is critical for microtubule network stability and repolymerization; disease-associated missense mutations (concentrated at the C-terminus for ALS/FTD, N-terminus for FTD) destabilize microtubules via dominant-negative mechanisms or cause haploinsufficiency, TUBA4A protein stability is negatively regulated by tubulin-folding cofactor B (TBCB), loss of TUBA4A alters tubulin post-translational modifications (acetylation, detyrosination, polyglutamylation), and certain mutations cause cytoplasmic protein aggregation with ubiquitin co-localization, collectively linking TUBA4A dysfunction to motor neuron disease, frontotemporal dementia, spastic ataxia, and myopathy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TUBA4A encodes an α-tubulin isotype that incorporates into the microtubule network and is required for its stability and capacity to repolymerize, with disease-associated missense variants impairing these functions in cellular and patient-derived assays [#0, #7]. Its abundance is post-translationally controlled: excess tubulin-folding cofactor B (TBCB) drives depolymerization and degradation of TUBA4A through a miR-1825/TBCB/TUBA4A axis that is dysregulated in ALS patient cortex and produces motor axon defects in vivo [#1]. Loss of TUBA4A function is conserved across species — zebrafish orthologue knockdown causes dose-dependent motor axonopathy rescuable by human wild-type mRNA, and additionally shifts the tubulin post-translational modification landscape including acetylation, detyrosination, and polyglutamylation [#5]. Pathogenicity operates through distinct mechanisms tied to mutation position: C-terminal ALS-associated variants act dominant-negatively by destabilizing microtubules [#0], whereas an N-terminal frameshift produces no detectable protein and reduces total TUBA4A, indicating haploinsufficiency [#3]. A subset of missense variants instead cause cytoplasmic TUBA4A aggregation that colocalizes with ubiquitin and is accompanied by autophagic, proteinopathic muscle pathology [#6, #8]. These functional and structural perturbations collectively link TUBA4A dysfunction to a spectrum of disease spanning ALS/FTD, spastic ataxia, and primary myopathy, with domain specificity shaping the affected cell type and clinical pattern [#2, #8, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established that ALS-associated TUBA4A variants are not benign polymorphisms but functionally compromise the microtubule cytoskeleton, providing the first mechanistic link between this α-tubulin and motor neuron disease.\",\n      \"evidence\": \"Microtubule repolymerization assays in cells expressing multiple ALS-associated mutant TUBA4A variants\",\n      \"pmids\": [\"25374358\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether the defect is dominant-negative versus loss-of-function\", \"No in vivo or patient-tissue confirmation in this study\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Answered how TUBA4A protein levels are controlled by identifying TBCB as a negative regulator whose excess degrades TUBA4A, embedding TUBA4A in a miR-1825/TBCB regulatory axis relevant to ALS.\",\n      \"evidence\": \"Transcriptomic/proteomic analysis with protein validation in ALS patient cortex and an in vivo motor-axon model\",\n      \"pmids\": [\"30030593\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of TBCB-driven TUBA4A degradation not defined\", \"Does not establish whether this axis is causal or secondary in sporadic ALS\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended TUBA4A dysfunction beyond ALS to FTD and introduced the idea that mutation position correlates with phenotype, with FTD variants clustering N-terminally.\",\n      \"evidence\": \"Immunoblotting and microtubule repolymerization assay for an FTD-associated variant\",\n      \"pmids\": [\"34169147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single variant analyzed\", \"Domain-phenotype correlation based on positional clustering rather than direct mechanistic comparison\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Distinguished a haploinsufficiency mechanism for N-terminal mutations by showing a frameshift variant yields no detectable protein and lowers total TUBA4A, contrasting with the dominant-negative model for C-terminal variants.\",\n      \"evidence\": \"qPCR, immunoblotting, and immunohistochemistry of patient material\",\n      \"pmids\": [\"35327632\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single case study\", \"Does not test whether reduced dosage alone reproduces neuronal phenotypes\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Proposed atomic-level explanations for variant pathogenicity, predicting impaired GTP binding, destabilized polymerization, and increased aggregation propensity for specific mutations.\",\n      \"evidence\": \"Molecular dynamics simulation and docking of ALS-associated mutations\",\n      \"pmids\": [\"36747013\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational prediction with no experimental validation\", \"Aggregation propensity predicted, not measured\", \"GTP-binding defect not biochemically confirmed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided in vivo loss-of-function evidence and connected TUBA4A to tubulin PTM homeostasis, showing knockdown causes motor axonopathy rescuable by human wild-type mRNA and alters acetylation, detyrosination, and polyglutamylation.\",\n      \"evidence\": \"Antisense morpholino knockdown in zebrafish with mRNA rescue, motor axon imaging, behavior assay, and antibody-based PTM detection\",\n      \"pmids\": [\"38463699\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking TUBA4A loss to altered PTMs not defined\", \"Morpholino-based knockdown not complemented by stable genetic null\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified a proteinopathy mechanism in which a TUBA4A missense variant aggregates and colocalizes with ubiquitin, linking TUBA4A to myopathy with rimmed vacuoles and broadening the phenotypic spectrum to muscle.\",\n      \"evidence\": \"Overexpression in a cellular model with immunofluorescence and immunohistochemistry of patient muscle biopsy\",\n      \"pmids\": [\"38413182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Aggregation shown by overexpression, not at endogenous levels\", \"Single variant and single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Confirmed pathogenicity of distinct missense variants in disease-relevant patient cells by demonstrating altered microtubule organization and dynamics.\",\n      \"evidence\": \"Microtubule organization/dynamics assays in patient-derived fibroblasts for three independent variants\",\n      \"pmids\": [\"38884572\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis (dynamics defect vs. dosage) not disentangled per variant\", \"Single study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established TUBA4A as a primary myopathy gene and demonstrated domain specificity, showing variants cause protein accumulation with autophagic proteinopathy and differentially impact microtubule dynamics depending on the affected domain.\",\n      \"evidence\": \"Immunohistochemistry of patient muscle biopsies with in silico and in vitro microtubule dynamics assays across multiple variants\",\n      \"pmids\": [\"41678358\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal link between accumulation and autophagy not resolved\", \"Domain-to-phenotype mapping correlative\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated cell-type-selective consequences of a TUBA4A mutation in a mammalian model, with ataxia, Purkinje degeneration, and muscle defects but no motor neuron degeneration.\",\n      \"evidence\": \"ENU screen with CRISPR knock-in confirmation of Tuba4a p.Gln176Pro, neuropathological and behavioral analysis in mouse (preprint)\",\n      \"pmids\": [\"41889878\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Molecular basis of cell-type selectivity unexplained\", \"Single mutation modeled\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved why TUBA4A variants of differing position and biochemical effect produce divergent tissue tropism (motor neuron, cortical, cerebellar, muscle), and how dominant-negative, haploinsufficiency, and aggregation mechanisms are selected in each context.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model linking mutation domain to cell-type vulnerability\", \"No structural data on mutant tubulin in assembled microtubules\", \"Relationship between altered PTMs and disease phenotype undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0005525\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [\"microtubule\"],\n    \"partners\": [\"TBCB\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}