Affinage

TUBB4B

Tubulin beta-4B chain · UniProt P68371

Length
445 aa
Mass
49.8 kDa
Annotated
2026-06-10
21 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TUBB4B encodes a β-tubulin isotype with a non-redundant, organelle-specific requirement in axonemal microtubule assembly in multi-ciliated cells (PMID:38662826, PMID:38031972). In ependymal, respiratory, oviduct, and photoreceptor cells it localizes to cilia—asymmetrically along the axonemal length—and its loss produces structural axonemal defects, disrupted ependymal planar polarity, impaired cerebrospinal fluid flow with hydrocephalus, and photoreceptor abnormalities, while sparing primary cilia (PMID:38031972, PMID:41459724, PMID:40606475). Its expression in ependymal cells is driven by the master ciliogenesis transcription factor FOXJ1 (PMID:41459724), and the protein acts within the CFAP251-dependent flagellar/ciliary assembly pathway, with which it physically interacts (PMID:41943837). Pathogenic dominant-negative TUBB4B variants disrupt distinct tubulin interfaces to impair centriole and cilium biogenesis, stratifying patients into three classes of ciliopathic disease (PMID:38662826). Beyond cilia, TUBB4B participates in microtubule–vimentin interactions and focal-adhesion maturation during cell migration and EMT (PMID:31375012), controls surface trafficking of proteins such as Ephrin-B1 (PMID:35004310), is post-transcriptionally stabilized by the m6A reader IGF2BP1 (PMID:39403946), is subject to deglutamylation by CCP1 (PMID:35741845, PMID:37439173), and modulates FAK, NF-κB, and MAPK/ERK signaling as well as cell-cycle progression via P21/CyclinD1 in proliferating and tumor cells (PMID:36787097, PMID:39403946, PMID:35741845, PMID:37439173).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 2019 Medium

    Established a non-ciliary cytoskeletal role for TUBB4B by linking its downregulation to microtubule-vimentin crosstalk and migratory cell architecture during EMT.

    Evidence Biochemical interaction and polymerization assays plus transmigration in colon cancer cells with reduced TUBB4B

    PMID:31375012

    Open questions at the time
    • No reconstitution of the microtubule-vimentin interaction
    • Direct binding partner mediating the interaction not identified
    • Causal direction relative to EMT not separated from correlation
  2. 2021 Medium

    Connected TUBB4B to surface protein trafficking, showing it sustains cancer stem cells by controlling membrane localization of Ephrin-B1.

    Evidence siRNA knockdown, sphere formation, in vivo tumor initiation, membrane fractionation and co-localization in oral cancer cells

    PMID:35004310

    Open questions at the time
    • Trafficking mechanism not reconstituted
    • Whether TUBB4B acts directly or via general microtubule transport unresolved
    • No structural basis for Ephrin-B1 cargo selectivity
  3. 2022 Medium

    Demonstrated TUBB4B controls proliferation and cell-cycle progression and is reciprocally regulated with the deglutamylase CCP1, defining a post-translational regulatory loop.

    Evidence CRISPR knockout in spermatogonia with proliferation, cell-cycle, RNA-seq and Western blot analysis

    PMID:35741845

    Open questions at the time
    • Mechanism linking TUBB4B to CyclinD1/Skp2/P21 not resolved
    • Functional consequence of CCP1 deglutamylation on TUBB4B not defined
    • Lysosomal membrane defect mechanism unexplained
  4. 2023 Medium

    Extended TUBB4B's signaling reach to NF-κB and MAPK/ERK pathways and reinforced the bidirectional TUBB4B-CCP1 regulatory relationship in spermatocytes.

    Evidence Lentiviral knockdown/overexpression with RT-qPCR, Western blot and flow cytometry in GC-2 cells

    PMID:37439173

    Open questions at the time
    • Direct versus indirect effect on NF-κB/MAPK not distinguished
    • No interaction partner bridging tubulin to these pathways
    • Single cell-line context
  5. 2023 Medium

    Placed TUBB4B in a pro-survival/cell-cycle axis in cancer, identifying Bcl-xL upregulation upon its loss as a synthetic-lethal vulnerability.

    Evidence CRISPR loss-of-function screen and knockout with RNA-seq, apoptosis/senescence assays, and in vivo growth in NAFLD-HCC

    PMID:36787097

    Open questions at the time
    • Mechanism of Bcl-xL induction unknown
    • Mebendazole specificity for TUBB4B not established
    • No direct molecular target connecting TUBB4B loss to apoptosis
  6. 2024 High

    Resolved the disease mechanism: dominant-negative TUBB4B variants disrupt distinct tubulin interfaces to impair centriole/cilium biogenesis, defining organelle-specific isotype function and three ciliopathy classes.

    Evidence Patient cohort genetics, mouse mutants, structure-function analysis and microtubule dynamics assays

    PMID:38662826

    Open questions at the time
    • Why specific tubulin interfaces map to specific tissues not fully mechanistic
    • Incorporation kinetics of mutant tubulin into axonemes not quantified across all classes
  7. 2024 High

    Defined TUBB4B as essential and non-redundant for motile-cilium axoneme assembly, with asymmetric distribution along multi-cilia and no role in primary cilia.

    Evidence Mouse Tubb4b knockout with ultrastructural axoneme analysis and direct localization in respiratory and oviduct MCCs

    PMID:38031972

    Open questions at the time
    • Molecular basis of asymmetric axonemal distribution unknown
    • How TUBB4B is excluded from primary cilia not explained
  8. 2024 Medium

    Identified m6A-dependent post-transcriptional control of TUBB4B by IGF2BP1 and downstream FAK activation as a driver of liver fibrosis.

    Evidence RIP-seq/m6A-seq target identification, IGF2BP1 and TUBB4B knockdown, mRNA stability and FAK pathway assays in hepatic stellate cells

    PMID:39403946

    Open questions at the time
    • Direct binding of TUBB4B to FAK pathway components not shown
    • m6A site on TUBB4B mRNA not mapped
    • Single-lab pathway placement
  9. 2024 Medium

    Showed P300 transcriptionally suppresses TUBB4B in NSCLC, with TUBB4B acting as a migration/invasion suppressor in this context.

    Evidence Expression manipulation, wound healing, Transwell, rescue experiments and xenografts in NSCLC cells

    PMID:38636368

    Open questions at the time
    • Mechanism of P300 action on TUBB4B beyond expression level unresolved
    • Context-dependent opposite roles of TUBB4B in different cancers unexplained
  10. 2024 Medium

    Established cross-species conservation of TUBB4B's ciliary function in photoreceptors and brain, recapitulating human ciliopathy phenotypes.

    Evidence Antisense morpholino knockdown in zebrafish with retinal histology

    PMID:40606475

    Open questions at the time
    • Morpholino off-target effects not excluded
    • Photoreceptor-specific axonemal defect not characterized ultrastructurally
  11. 2024 Medium

    Tested tissue specificity of a recurrent variant, showing R391 mutations spare sensory hair cell structure and audition while modestly reducing crista hair cell number.

    Evidence Zebrafish knockout/transgenic localization imaging and auditory function testing

    PMID:39515407

    Open questions at the time
    • Negative auditory result limits conclusions on hearing involvement
    • Mechanism of the small crista cell reduction unknown
  12. 2025 High

    Identified TUBB4B as the dominant ependymal β-tubulin isotype under FOXJ1 transcriptional control, linking its loss to planar polarity defects, impaired CSF flow and hydrocephalus.

    Evidence Endogenous CRISPR tagging, knockout, FOXJ1 luciferase reporter and ciliary motility/polarity assays in mouse ependymal cells

    PMID:41459724

    Open questions at the time
    • Direct FOXJ1 binding site on TUBB4B promoter not mapped
    • Mechanism connecting axonemal defect to planar polarity loss unresolved
  13. 2025 Low

    Implicated TUBB4B in immune modulation by shifting CD4+ T cell differentiation toward a regulatory phenotype.

    Evidence TUBB4B overexpression in CD4+ T cells with cytokine measurement and flow cytometry

    PMID:40793858

    Open questions at the time
    • No mechanistic pathway or interaction partner identified
    • Single-lab overexpression-only evidence
    • Endogenous relevance not established
  14. 2026 Medium

    Positioned TUBB4B within the CFAP251 flagellar/ciliary assembly pathway as a physically interacting downstream component.

    Evidence Cfap251 knockout mouse, patient exome sequencing, CFAP251-TUBB4B interaction assay and Western blot

    PMID:41943837

    Open questions at the time
    • Interaction interface not mapped
    • Whether interaction is direct or complex-mediated unresolved
    • Reciprocal validation limited
  15. 2026 Low

    Proposed a TUBB4B-STMN1-ERK/MAPK axis driving G1/S transition in pituitary tumor cells, with a small-molecule (AS-IV) inhibitor.

    Evidence Overexpression/knockout, EdU/TUNEL, U0126 ERK-inhibitor rescue and AS-IV binding/docking in pituitary tumor cells

    PMID:41930558

    Open questions at the time
    • Binding affinity data incompletely described
    • Direct TUBB4B-STMN1 regulatory link not biochemically proven
    • Single-lab inhibitor-based mechanism

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single β-tubulin isotype achieves its non-redundant, tissue- and organelle-specific axonemal function—and what determines its asymmetric distribution and exclusion from primary cilia—remains unresolved.
  • No structural model of TUBB4B-specific axonemal incorporation
  • Determinants of asymmetric distribution along multi-cilia unknown
  • Reconciliation of ciliary versus signaling/trafficking roles in non-ciliated cells not achieved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3 GO:0008092 cytoskeletal protein binding 1
Localization
GO:0005856 cytoskeleton 3 GO:0005929 cilium 2 GO:0005815 microtubule organizing center 1
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 3 R-HSA-1640170 Cell Cycle 2
Partners
CCP1CFAP251IGF2BP1VIMENTIN
Complex memberships
axoneme

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2024 TUBB4B variants specifically perturb centriole and cilium biogenesis in a dominant-negative manner; distinct variants disrupt different tubulin interfaces, stratifying patients into three classes of ciliopathic disease. Structure-function studies established that different TUBB4B variants disrupt distinct tubulin interfaces, demonstrating organelle-specific, non-redundant functions for this isotype in axonemal microtubules. Patient cohort genetic analysis, mouse mutants, structure-function studies with dominant-negative variant characterization, microtubule dynamics assays Science High 38662826
2024 Tubb4b localizes specifically to cilia in multi-ciliated cells (MCCs) and is asymmetrically distributed within multi-cilia along the axonemal length. Deletion of Tubb4b causes striking structural defects in axonemes of multi-cilia without affecting primary cilia, establishing that Tubb4b is essential for formation of a specific MT-based subcellular organelle. Mouse knockout (Tubb4b deletion), direct localization by imaging in respiratory and oviduct MCCs, ultrastructural analysis of axonemes Development High 38031972
2025 TUBB4B is the most abundant β-tubulin isotype in ependymal cilia. TUBB4B expression in ependymal cells is specifically regulated by the ciliogenesis transcription factor FOXJ1 (demonstrated by luciferase reporter assay). TUBB4B deficiency disrupts planar polarity of ependymal cells and impairs cerebrospinal fluid flow, resulting in hydrocephalus. CRISPR/Cas9 endogenous tagging with HA/GFP for isotype identification, TUBB4B knockout, luciferase reporter assay for FOXJ1 regulation, ciliary motility and polarity assays in mouse ependymal cells Journal of molecular cell biology High 41459724
2019 Downregulation of TUBB4B during EMT in colon cancer cells contributes to microtubule-vimentin interaction, maintenance of cell polarity in migrating cells, and faster microtubule polymerization. Decreased TUBB4B is accompanied by cell elongation and increased number of matured focal adhesion sites. Biochemical assays (microtubule-vimentin interaction), transmigration assay, microscopy, polymerization kinetics in cells with reduced TUBB4B levels Cells Medium 31375012
2021 TUBB4B knockdown in oral cancer cells downregulates pluripotency markers, depletes ALDH1A1+ population, decreases sphere formation, and diminishes tumor initiation potential in vivo. TUBB4B depletion reduces membrane expression of Ephrin-B1, and TUBB4B and Ephrin-B1 co-localize in the cancer stem cell niche, indicating TUBB4B controls surface localization of proteins that sustain cancer stem cells. siRNA knockdown, in vitro sphere formation assay, in vivo tumor initiation assay, co-localization imaging, membrane fractionation Frontiers in oncology Medium 35004310
2023 TUBB4B knockout in NAFLD-HCC cells promotes apoptosis, cell cycle arrest, and cellular senescence. TUBB4B knockout induces upregulation of pro-survival Bcl-xL, and combination of TUBB4B inhibition (by mebendazole) with navitoclax (Bcl-xL inhibitor) synergistically inhibits NAFLD-HCC growth via induction of intrinsic and extrinsic apoptosis pathways. CRISPR/Cas9 library screening (loss-of-function), TUBB4B KO in cell lines, RNA-sequencing, in vitro and in vivo growth assays, apoptosis/senescence assays The Journal of pathology Medium 36787097
2024 IGF2BP1 (an m6A reader) stabilizes TUBB4B mRNA in an m6A-dependent manner, upregulating TUBB4B protein expression in activated hepatic stellate cells. TUBB4B in turn induces liver fibrosis by activating the FAK signaling pathway. RIP-seq and m6A-seq re-analysis to identify TUBB4B as IGF2BP1 target, siRNA knockdown of IGF2BP1 and TUBB4B, mRNA stability assay (implied by m6A-dependent stabilization), FAK pathway activation assay Journal of gastroenterology and hepatology Medium 39403946
2024 P300 (E1A binding protein p300) negatively regulates TUBB4B expression in NSCLC cells. P300 overexpression inhibits TUBB4B, while P300 silencing increases TUBB4B expression. TUBB4B overexpression suppresses NSCLC cell migration, invasion and EMT; rescue experiments confirmed that P300 promotes migration/invasion through TUBB4B suppression. qRT-PCR, Western blot, wound healing assay, Transwell invasion assay, rescue experiments (P300 and TUBB4B co-manipulation), xenograft tumor model Tissue & cell Medium 38636368
2022 Tubb4b knockout in mouse spermatogonia causes abnormal lysosomal membranes, cell morphology defects, slower proliferation, and G1/0 cell cycle arrest. Tubb4b KO significantly reduces CyclinsD1, Skp2, and cell growth factors, and upregulates Cdkn1a (P21). TUBB4B and CCP1 mutually regulate each other's expression in spermatogonia (confirmed in separate study): CCP1 can deglutamylate TUBB4B. CRISPR/Cas9 Tubb4b knockout in spermatogonia cell line, CCK8 proliferation assay, flow cytometry cell cycle analysis, RNA-seq, RT-qPCR, Western blot Genes Medium 35741845
2023 TUBB4B and CCP1 (Agtpbp1/cytosolic carboxypeptidase-like 1) mutually positively regulate each other in primary spermatocytes (GC-2 cells): TUBB4B silencing or overexpression causes concordant changes in CCP1, and CCP1 knockdown/restoration causes concordant changes in TUBB4B. CCP1 can deglutamylate TUBB4B. TUBB4B silencing or overexpression causes significant changes in NF-κB (p65, p-p65) and MAPK (ERK1/2, p-ERK1/2) signaling pathway proteins. Lentiviral knockdown and overexpression, RT-qPCR, Western blot, immunofluorescence, CCK8, flow cytometry Nan fang yi ke da xue xue bao Medium 37439173
2026 CFAP251 physically interacts with TUBB4B (confirmed by co-immunoprecipitation or equivalent), and CFAP251 deficiency leads to downregulation of TUBB4B, impairing spermiogenesis and ciliary function. This establishes TUBB4B as a downstream component of the CFAP251-dependent assembly pathway for sperm flagella and cilia. Cfap251 knockout mouse, whole-exome sequencing of patients, protein interaction assay (CFAP251-TUBB4B), Western blot for TUBB4B levels in KO International journal of biological sciences Medium 41943837
2024 Knockdown of tubb4b in zebrafish causes cone and rod photoreceptor abnormalities in the retina and hydrocephalus in the developing brain, resulting in early larval lethality. This demonstrates conservation of TUBB4B ciliary function in photoreceptors between zebrafish and humans. Antisense morpholino knockdown of tubb4b in zebrafish, retinal histology Molecular vision Medium 40606475
2026 TUBB4B activates the ERK/MAPK signaling pathway by upregulating Stathmin 1 (STMN1) expression, promoting G1/S phase transition in pituitary tumor cells. Astragaloside IV (AS-IV) binds TUBB4B with high affinity, forming a stable complex and inhibiting TUBB4B function. The ERK-specific inhibitor U0126 reverses the pro-proliferative effect of TUBB4B, confirming pathway placement. CCK-8, TUNEL, EdU, IHC, Western blot, TUBB4B overexpression/KO, molecular docking/binding assay (AS-IV to TUBB4B), U0126 ERK inhibitor rescue experiment International journal of molecular medicine Low 41930558
2025 TUBB4B overexpression in CD4+ T cells decreases frequencies of IL-17+ and IFN-γ+ CD4+ T cells and reduces IL-17 and IFN-γ production, while upregulating CD4+CD25+FOXP3+ (Treg) frequency and enhancing IL-10 secretion, establishing a direct role for TUBB4B in modulating Th17/Th1/Treg balance. TUBB4B overexpression in CD4+ T cells, cytokine measurement, flow cytometry for T cell subset frequencies Investigative ophthalmology & visual science Low 40793858
2024 In a zebrafish model, R391 TUBB4B mutations do not impair localization of TuBB4b within sensory hair cells nor their structure, but induce a small decrease in sensory hair cell number from anterior crista. Expression of R391 mutations in sensory hair cells has no effect on zebrafish audition (negative result for auditory functional deficit). Zebrafish knockout and transgenic approaches, localization imaging, auditory function testing Developmental biology Medium 39515407

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 TUBB4B Downregulation Is Critical for Increasing Migration of Metastatic Colon Cancer Cells. Cells 37 31375012
2024 Ciliopathy patient variants reveal organelle-specific functions for TUBB4B in axonemal microtubules. Science (New York, N.Y.) 33 38662826
2021 β-Tubulin Isotype, TUBB4B, Regulates The Maintenance of Cancer Stem Cells. Frontiers in oncology 20 35004310
2024 Tubb4b is required for multi-ciliogenesis in the mouse. Development (Cambridge, England) 13 38031972
2023 TUBB4B is a novel therapeutic target in non-alcoholic fatty liver disease-associated hepatocellular carcinoma. The Journal of pathology 13 36787097
2023 Clinical, genetic, and structural characterization of a novel TUBB4B tubulinopathy. Molecular genetics and metabolism reports 13 37448631
2022 TUBB4B gene mutation in Leber phenotype of congenital amaurosis syndrome associated with early-onset deafness. European journal of medical genetics 13 35240325
2022 Tubulin TUBB4B Is Involved in Spermatogonia Proliferation and Cell Cycle Processes. Genes 12 35741845
2025 A Novel Variant in TUBB4B Causes Progressive Cone-Rod Dystrophy and Early Onset Sensorineural Hearing Loss. Molecular genetics & genomic medicine 4 39876836
2025 DNA 5-Hydroxymethylcytosine Landscape and Transcriptional Profile Highlight the TUBB4B-Mediated Th17/Th1/Treg Imbalance in Behçet's Uveitis. Investigative ophthalmology & visual science 4 40793858
2024 Comprehensive analysis of two hotspot codons in the TUBB4B gene and associated phenotypes. Scientific reports 4 38719929
2025 Mutation of beta-tubulin 4B gene (TUBB4B) causes autosomal dominant retinitis pigmentosa with sensorineural hearing loss in a multigenerational family. Molecular vision 2 40606475
2024 The m6A reader IGF2BP1 contributes to the activation of hepatic stellate cells through facilitating TUBB4B mRNA stabilization. Journal of gastroenterology and hepatology 2 39403946
2025 Screening the composition of tubulin isotypes reveals the most abundant TUBB4B for ciliary polarity in ependymal cells. Journal of molecular cell biology 1 41459724
2024 P300 reduces TUBB4B expression to facilitate the biological process of migration and invasion of non-small cell lung cancer cells. Tissue & cell 1 38636368
2024 Rare variants and handedness: spotlight on TUBB4B. Trends in genetics : TIG 1 38749881
2023 [Expression of TUBB4B in mouse primary spermatocyte GC-2 cells and its regulatory effect on NF-κB and MAPK signaling pathway]. Nan fang yi ke da xue xue bao = Journal of Southern Medical University 1 37439173
2026 Astragaloside IV targets TUBB4B to inhibit proliferation and promote apoptosis of pituitary tumor cells via the STMN1/ERK pathway. International journal of molecular medicine 0 41930558
2026 CFAP251 Deficiency Induces Male Infertility and PCD-like Ciliary Defects by Disrupting TUBB4B and SLC25A4 Recruitment in Humans and Mice. International journal of biological sciences 0 41943837
2025 A novel missense TUBB4B variant outside of the canonical hotspot is associated with cone-rod dystrophy and sensorineural hearing loss. Ophthalmic genetics 0 41057290
2024 R391 human dominant mutation does not affect TubB4b localization and sensory hair cells structure in zebrafish inner ear and lateral line. Developmental biology 0 39515407

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