TUBB3-related Tubulinopathy

Mendelian MONDO:0100154 Pathograph 18 Show in embeddings browser congenital nervous system disorder disorder of development or morphogenesis hereditary neurological disease neuronal migration disorder

TUBB3-related tubulinopathy is a neurodevelopmental disorder caused by heterozygous missense mutations in TUBB3, which encodes the neuron-specific beta-tubulin isotype III. Beta-III tubulin pairs with alpha-tubulin to form the heterodimers that polymerize into the highly dynamic neuronal microtubules required for axon outgrowth, growth-cone guidance, and microtubule-based neuronal migration. Unlike the alpha-tubulin (TUBA1A) and beta-tubulin (TUBB2B) disorders, in which cortical migration failure is the dominant defect, TUBB3 disease is distinguished by two separable, mutation-class dependent mechanistic arms that share the same upstream tubulin lesion. In one arm, kinesin-interaction-deficient mutations impair the motility of kinesin motors on microtubules and produce axon guidance failure in cranial motor neurons, causing hypoplasia of the oculomotor and other cranial nerves with the ocular motility disorder congenital fibrosis of the extraocular muscles type 3 (CFEOM3), together with corpus callosum and commissural tract dysgenesis and, in some individuals, facial weakness and a later-onset axonal sensorimotor polyneuropathy. In the other arm, mutations that alter microtubule dynamics impair radial neuronal migration and produce malformations of cortical development — cortical disorganization, polymicrogyria-like cortical dysplasia, and pontocerebellar hypoplasia — often without ocular motility defects. Shared tubulinopathy imaging hallmarks include dysmorphic basal ganglia, midline commissural hypoplasia or agenesis, and cerebellar and brainstem hypoplasia. TUBB3 is modeled here as its own beta-III-tubulin pathomechanism entry rather than lumped under generic lissencephaly or polymicrogyria, because its central skeleton uniquely couples a kinesin-dependent axon guidance / cranial dysinnervation arm to the broader microtubule-dependent neuronal migration family that includes TUBA1A, TUBB2B, TUBB5, and TUBG1.

Ask OpenScientist

Ask a research question about TUBB3-related Tubulinopathy. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

2
Mappings
1
Inheritance
5
Pathophys.
13
Phenotypes
3
Gaps
18
Pathograph
1
Genes
1
Variants
3
Medical Actions
1
Models
12
References
🔗

Mappings

MONDO
MONDO:0013541 complex cortical dysplasia with other brain malformations 1 Not Yet Curated
skos:narrowMatch MONDO
CDCBM1 is MONDO's TUBB3-specific cortical-malformation concept. This entry curates that presentation as its Cortical Dyslamination / Cortical Dysgyria arm, alongside the axon-guidance arm, so CDCBM1 is subsumed by this entry's broader disease_term MONDO:0100154 rather than equivalent to it.
MONDO:0010912 fibrosis of extraocular muscles, congenital, 3A, with or without extraocular involvement Not Yet Curated
skos:narrowMatch MONDO
CFEOM3A is MONDO's TUBB3-specific ocular-motility concept and is curated here as the Congenital Fibrosis of Extraocular Muscles phenotype downstream of this entry's axon-guidance arm. narrowMatch because this entry spans the full TUBB3 syndrome, of which CFEOM3 is the ocular component.
👪

Inheritance

1
Autosomal dominant inheritance HP:0000006
Autosomal dominant inheritance
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific beta-tubulin isotype III, result in a spectrum of human nervous system disorders that we now call the TUBB3 syndromes."
The founding TUBB3 syndrome report establishes heterozygous missense mutations as sufficient to cause the disorder, supporting autosomal dominant inheritance.
?

Discussions and Knowledge Gaps

3
Why do different TUBB3 missense mutations preferentially produce the kinesin-dependent axon guidance / CFEOM3 arm versus the microtubule-dynamics cortical migration arm, and what is the structural basis for this phenotypic divergence from a shared tubulin lesion?
KNOWLEDGE GAP OPEN gap_tubb3_arm_genotype_phenotype_divergence
Attached to
pathophysiology#Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure pathophysiology#Impaired Microtubule-Dependent Neuronal Migration
CFEOM3-associated mutations increase microtubule stability and disrupt kinesin interaction, whereas malformation-of-cortical-development mutations alter microtubule resistance to depolymerization, and the two phenotypic profiles are largely non-overlapping. The residue-to-mechanism map is only partially resolved, so it is not yet possible to predict from genotype which arm will dominate, or whether some variants engage both arms simultaneously.
Show evidence (1 reference)
PMID:20829227 SUPPORT In Vitro
"MCD mutations can alter the resistance of MTs to depolymerization. Interestingly, this finding contrasts with the increased MT stability observed in the case of CFEOM3-related mutations."
Directly supports distinct biophysical effects in the two clinical arms.
Is disruption of the kinesin-microtubule interaction sufficient and necessary to cause CFEOM3, or is altered microtubule dynamic instability alone able to produce the axon guidance defect?
KNOWLEDGE GAP OPEN gap_tubb3_kinesin_causality_for_cfeom
Attached to
pathophysiology#Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
Engineering a compensatory mutation in the kinesin L12 loop restores motility on R262 mutant microtubules and rescues axonal growth in a CFEOM3 mouse model, strongly supporting kinesin-microtubule disruption as causal for the axon-guidance arm. However, because all TUBB3 mutations also alter dynamic instability, the independent contribution of microtubule dynamics to the cranial dysinnervation phenotype is not fully excluded.
Show evidence (1 reference)
PMID:26775887 SUPPORT Model Organism
"in a CFEOM3 mouse model expressing the same mutation, overexpressing the suppressor mutant kinesin restores axonal growth in vivo."
Rescue supports kinesin-interface causality while not excluding a parallel contribution from altered dynamics.
For the TUBB3 cortical neuronal-migration arm, is the primary defect in post-mitotic migrating neurons or in apical/outer radial glial progenitors, and which features require human iPSC-derived cortical organoids or fetal tissue to resolve, given that the available knock-in disease mouse does not reproduce the human cortical malformation?
HUMAN MODEL MISMATCH OPEN gap_tubb3_cell_type_primacy_human_model_translatability
Attached to
pathophysiology#Altered Beta-III Tubulin (TUBB3) Function pathophysiology#Impaired Microtubule-Dependent Neuronal Migration pathophysiology#Cortical Dyslamination
Human TUBB3 patients show cortical malformations (dyslamination, polymicrogyria-like cortex, callosal and pontocerebellar anomalies), yet the TUBB3 knock-in disease mouse reproduces the axon-guidance arm without cortical cell-migration abnormalities, so the cell population primarily responsible for the human cortical-migration arm — post-mitotic migrating neurons versus apical or outer radial glial progenitors — cannot be assigned from the available rodent model. As for the other tubulinopathies (TUBA1A, TUBB2A/TUBB2B, TUBB5), human cortical expansion depends on outer radial glia and fetal cortical organization that lissencephalic rodents do not fully represent, so resolving progenitor-primary versus migration-primary contributions requires human iPSC-derived cortical organoid or fetal-tissue benchmarks. Captured per the cortical-malformation epic (#4098/#4101) cell-type-ambiguity and human/model-mismatch curation guidance.
Proposed experiments
TUBB3 isogenic cortical-organoid cell-type-of-origin experiment
patient-derived cortical organoid perturbation experiment Relation: this experiment is of type this experiment type This experiment is of type patient-derived cortical organoid perturbation experiment.
exp_tubb3_isogenic_cortical_organoid_celltype
Engineer recurrent cortical-malformation-associated TUBB3 missense variants into human iPSCs, correct patient-derived variants isogenically where available, and compare cortical organoid neuronal migration, radial-glial organization, microtubule dynamics, and outer-radial-glia mitosis to test whether the cortical-migration arm is primarily post-mitotic neuronal or also reflects apical/outer radial glial progenitor vulnerability not captured by the knock-in mouse.
Model systems
TUBB3 human iPSC-derived cortical organoid
Three-dimensional human cortical organoid carrying a cortical-malformation-associated TUBB3 variant, with isogenic corrected and knock-in controls.
ORGANOID namo:Organoid link
human NCBITaxon:9606 NCBI Taxonomy (NCBITaxon) Relation: this experimental model is built in this organism This experimental model is built in human, annotated with Homo sapiens (NCBITaxon:9606). NCBITaxon:9606 is an organism from the NCBI Taxonomy.
cerebral cortex UBERON:0000956 Uberon multi-species anatomy ontology (UBERON) Relation: this experimental model uses this anatomical location This experimental model uses cerebral cortex (UBERON:0000956). UBERON:0000956 is an anatomical location from the Uberon multi-species anatomy ontology.
radial glial cell CL:0000681 Cell Ontology (CL) Relation: this experimental model uses this cell type This experimental model uses radial glial cell (CL:0000681). CL:0000681 is a cell type from the Cell Ontology. migrating cortical neuron CL:0000540 Cell Ontology (CL) Relation: this experimental model uses this cell type This experimental model uses migrating cortical neuron, annotated with neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Perturbations
TUBB3 variant correction or knock-in
pathophysiology#Altered Beta-III Tubulin (TUBB3) Function
Correct a patient TUBB3 variant or introduce a recurrent cortical-malformation-associated missense variant into an isogenic human iPSC background.
TUBB3 (beta-III tubulin) hgnc:20772 HUGO Gene Nomenclature Committee (hgnc) Relation: this perturbation targets this gene This perturbation targets TUBB3 (beta-III tubulin), annotated with TUBB3 (hgnc:20772). hgnc:20772 is a gene from the HUGO Gene Nomenclature Committee.
Readouts
Cortical neuronal migration and progenitor organization
pathophysiology#Impaired Microtubule-Dependent Neuronal Migration
neuron migration GO:0001764 Gene Ontology (GO) Relation: this readout reports on this biological process This readout reports on decreased neuron migration (GO:0001764). GO:0001764 is a biological process from the Gene Ontology. ↓ DECREASED microtubule cytoskeleton organization GO:0000226 Gene Ontology (GO) Relation: this readout reports on this biological process This readout reports on dysregulated microtubule cytoskeleton organization (GO:0000226). GO:0000226 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Show evidence (2 references)
PMID:20074521 SUPPORT Model Organism
"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."
The TUBB3 knock-in mouse recapitulates the axon-guidance arm but not the cortical-migration malformation seen in human patients, making the human cortical-migration mechanism and its primary cell type a model-to-human translatability gap.
PMID:28111201 SUPPORT Other
"However, the mouse brain is naturally lissencephalic, suggesting that certain aspects of cortical development may not be adequately assessed in mice."
Supports treating rodent-to-human translation as an explicit knowledge gap for the cortical-migration arm of tubulin-related malformations, including the contribution of human outer radial glia.
⚙

Pathophysiology

5
Altered Beta-III Tubulin (TUBB3) Function
Heterozygous missense mutations in TUBB3 alter the neuron-specific beta-III tubulin isotype. Disease-associated substitutions reduce the abundance of functional alpha/beta-tubulin heterodimers and alter the dynamic instability of the microtubules that incorporate beta-III tubulin. Different residues perturb distinct microtubule properties — some alter the resistance of microtubules to depolymerization while a subset disrupts the interaction of microtubules with kinesin motors — establishing altered beta-III tubulin function as the shared initiating molecular lesion that feeds the divergent axon-guidance and neuronal-migration arms of the disorder.
migrating and post-mitotic neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves migrating and post-mitotic neuron, annotated with neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
TUBB3 hgnc:20772 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves TUBB3 (hgnc:20772). hgnc:20772 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context allele_type: missense variant_origin: DE_NOVO zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE
All reported disease alleles are heterozygous missense substitutions. The founding functional study showed that although the substitutions impair heterodimer formation, the mutant heterodimers that do fold still polymerize into microtubules, where they alter dynamic instability and, for a subset of residues, disrupt the microtubule-kinesin interaction. A mutant subunit that incorporates into the polymer and degrades a motor-binding surface acts on the wild-type polymer rather than merely subtracting one gene dose, which is why the category is DOMINANT_NEGATIVE and not haploinsufficiency. Some alleles are inherited from a mildly affected or unaffected parent, and one maternally inherited TUBB3 c.211G>A allele has been reported with milder features.
tubulin heterodimer assembly GO:0007021 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased tubulin heterodimer assembly, annotated with tubulin complex assembly (GO:0007021). GO:0007021 is a biological process from the Gene Ontology. ↓ DECREASED microtubule cytoskeleton organization GO:0000226 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated microtubule cytoskeleton organization (GO:0000226). GO:0000226 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Downstream
Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure Kinesin-interaction-deficient TUBB3 mutations impair kinesin motility on microtubules and disrupt axon guidance in cranial motor neurons.
Impaired Microtubule-Dependent Neuronal Migration Microtubule-dynamics-altering TUBB3 mutations impair the microtubule-dependent nucleokinesis required for radial cortical neuronal migration.
Cerebellar Hypoplasia TUBB3 cortical-malformation variants are associated with pontocerebellar hypoplasia through unresolved developmental intermediates.
Pontine Hypoplasia TUBB3 cortical-malformation variants are associated with pontine hypoplasia through unresolved developmental intermediates.
Dysmorphic Basal Ganglia TUBB3 dysfunction is associated with basal-ganglia dysmorphism through unresolved developmental intermediates.
Brainstem Abnormalities TUBB3 dysfunction is associated with brainstem hypoplasia through unresolved developmental intermediates.
Intellectual Disability Some TUBB3 variants produce intellectual impairment through unresolved neurodevelopmental intermediates.
Peripheral Neuropathy Some TUBB3 variants produce later-onset axonal sensorimotor polyneuropathy through unresolved intermediates.
Microcephaly A severe fetal TUBB3 cortical-malformation presentation included microcephaly through unresolved developmental intermediates.
Show evidence (4 references)
PMID:20074521 SUPPORT In Vitro
"We show that the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules."
Establishes impaired tubulin heterodimer formation as the molecular lesion caused by TUBB3 mutations, while showing the residual heterodimers still polymerize.
PMID:20074521 SUPPORT In Vitro
"Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors."
Shows that all TUBB3 mutations alter microtubule dynamic instability while only a subset additionally disrupts kinesin-microtubule interaction, establishing the basis for the two mechanistic arms.
PMID:20829227 SUPPORT In Vitro
"the mutated βIII-tubulin causing the MCD phenotype results in a reduction of heterodimer formation, yet produce correctly formed microtubules (MTs) in mammalian cells"
Confirms that cortical-malformation-causing TUBB3 mutations reduce heterodimer formation while still producing microtubules.
+ 1 more reference
Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
In the axon-guidance arm, TUBB3 mutations that affect residues mediating the kinesin-microtubule interface (notably R262) impair the motility and ATPase activity of kinesin motors moving along microtubules. Because beta-III tubulin is expressed most highly during axon outgrowth, this defect compromises kinesin-dependent axonal transport and growth-cone dynamics, producing axon guidance and projection-maintenance failure in the absence of overt cortical migration abnormalities — the mechanism underlying the cranial dysinnervation phenotype.
developing neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves developing neuron, annotated with neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology. cranial motor neuron CL:0000100 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cranial motor neuron, annotated with motor neuron (CL:0000100). CL:0000100 is a cell type from the Cell Ontology.
microtubule-based movement GO:0007018 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated microtubule-based movement (GO:0007018). GO:0007018 is a biological process from the Gene Ontology. ↕ DYSREGULATED neuron projection guidance GO:0097485 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated neuron projection guidance (GO:0097485). GO:0097485 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Animal models
Tubb3 knock-in axon-guidance mouse Mouse (Mus musculus) partially recapitulates The knock-in model reproduces the axon-guidance failure central to the CFEOM3 arm.
Downstream
Cranial Motor Nerve Maldevelopment and Ocular Dysmotility Axon guidance failure in cranial motor neurons leads to hypoplasia of the oculomotor and other cranial nerves and to commissural tract dysgenesis.
Show evidence (3 references)
PMID:20074521 SUPPORT Model Organism
"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."
A TUBB3 knock-in mouse shows that the axon-guidance arm can occur independently of cortical migration failure, defining it as a separable mechanistic branch.
PMID:26775887 SUPPORT In Vitro
"the disease-associated TUBB3 mutations R262H and R262A impair the motility and ATPase activity of the kinesin motor"
Direct biochemical demonstration that CFEOM3-associated TUBB3 mutations impair kinesin motility and ATPase activity, the molecular basis of the axon-guidance arm.
PMID:20074521 SUPPORT Model Organism
"These findings demonstrate that normal TUBB3 is required for axon guidance and maintenance in mammals."
Establishes the requirement for normal TUBB3 in axon guidance and maintenance, the process disrupted in this arm.
Cranial Motor Nerve Maldevelopment and Ocular Dysmotility
Failure of kinesin-dependent axon guidance in cranial motor neurons produces hypoplasia of the oculomotor (and trochlear/abducens) nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. The misinnervation of the extraocular muscles manifests clinically as congenital fibrosis of the extraocular muscles type 3 (CFEOM3), a restrictive non-progressive ocular motility disorder, and may be accompanied by facial weakness and a later-onset axonal sensorimotor polyneuropathy.
cranial motor neuron CL:0000100 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cranial motor neuron, annotated with motor neuron (CL:0000100). CL:0000100 is a cell type from the Cell Ontology.
neuron projection guidance GO:0097485 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased neuron projection guidance (GO:0097485). GO:0097485 is a biological process from the Gene Ontology. ↓ DECREASED neuron projection morphogenesis GO:0048812 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal neuron projection morphogenesis (GO:0048812). GO:0048812 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Congenital Fibrosis of Extraocular Muscles Cranial motor dysinnervation produces the CFEOM3 ocular phenotype.
Abnormal Corpus Callosum Morphology TUBB3 axon-guidance disruption is associated with commissural tract dysgenesis.
Show evidence (2 references)
PMID:20074521 SUPPORT Human Clinical
"Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts."
Documents oculomotor nerve hypoplasia and commissural/corticospinal tract dysgenesis as the imaging correlates of the cranial axon-guidance defect.
PMID:20829227 SUPPORT Human Clinical
"Mutations in the TUBB3 gene, encoding β-tubulin isotype III, were recently shown to be associated with various neurological syndromes which all have in common the ocular motility disorder, congenital fibrosis of the extraocular muscle type 3 (CFEOM3)"
Establishes CFEOM3 in the originally described axon-guidance-associated TUBB3 syndromes; other TUBB3 cortical-malformation variants can lack it.
Impaired Microtubule-Dependent Neuronal Migration
In the cortical arm, TUBB3 mutations that alter microtubule dynamics impair the microtubule-based nucleokinesis and radial migration of cortical neurons. Patient fibroblasts carrying malformation-of-cortical-development mutations show altered resistance of microtubules to depolymerization, contrasting with the increased microtubule stability seen with CFEOM3 mutations, so that the migration defect arises from a distinct biophysical perturbation of the same microtubule apparatus.
migrating cortical neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves migrating cortical neuron, annotated with neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
neuron migration GO:0001764 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased neuron migration (GO:0001764). GO:0001764 is a biological process from the Gene Ontology. ↓ DECREASED microtubule-based movement GO:0007018 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated microtubule-based movement (GO:0007018). GO:0007018 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Animal models
Tubb3 knock-in axon-guidance mouse Mouse (Mus musculus) fails to recapitulate The model does not reproduce the cortical neuronal-migration arm of human TUBB3 disease.
Downstream
Cortical Dyslamination Failed microtubule-dependent migration leaves cortical neurons mispositioned, producing abnormal cortical lamination and gyration.
Show evidence (3 references)
PMID:20829227 SUPPORT Human Clinical
"the spectrum of TUBB3-related phenotype is broader than previously described and includes malformations of cortical development (MCD) associated with neuronal migration and differentiation defects, axonal guidance and tract organization impairment"
Establishes that TUBB3 mutations cause malformations of cortical development associated with neuronal migration and differentiation defects, the cortical arm of the disorder.
PMID:20829227 SUPPORT In Vitro
"MCD mutations can alter the resistance of MTs to depolymerization"
Shows that cortical-malformation TUBB3 mutations alter microtubule stability, the biophysical perturbation underlying the migration defect.
PMID:35915025 SUPPORT Human Clinical
"abnormal corticogenesis due to impaired migration or lamination and abnormal growth cone dynamics of projecting and callosal axons"
Frames the cortical consequence of tubulinopathy mutations as impaired migration/lamination together with abnormal axonal growth-cone dynamics.
Cortical Dyslamination
Impaired migration of cortical neurons disrupts cortical lamination, producing cortical disorganization and focal or multifocal dysgyria with an abnormal and simplified gyral pattern.
cortical neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical neuron, annotated with neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
cerebral cortex development GO:0021987 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated cerebral cortex development (GO:0021987). GO:0021987 is a biological process from the Gene Ontology. ↕ DYSREGULATED neuron migration GO:0001764 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased neuron migration (GO:0001764). GO:0001764 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Cortical Dysgyria Cortical dyslamination manifests as abnormal and simplified gyration.
Show evidence (3 references)
PMID:20829227 SUPPORT Human Clinical
"all share cortical disorganization, axonal abnormalities associated with pontocerebellar hypoplasia, but with no ocular motility defects, CFEOM3"
Documents the cortical-arm phenotype of cortical disorganization with pontocerebellar hypoplasia occurring without the ocular motility defect.
PMID:24860126 SUPPORT Human Clinical
"By contrast, TUBB3 and TUBB5 mutations cause milder malformations with focal or multifocal polymicrogyria-like cortical dysplasia with abnormal and simplified gyral pattern"
Characterizes the TUBB3 cortical malformation as milder polymicrogyria-like cortical dysplasia with simplified gyration, distinct from TUBA1A lissencephaly.
PMID:35915025 SUPPORT Human Clinical
"Additional distinctive MRI features include dysmorphism of the basal ganglia, midline commissural structure hypoplasia or agenesis, and cerebellar and brainstem hypoplasia"
Establishes the shared tubulinopathy imaging accompaniments — dysmorphic basal ganglia, commissural hypoplasia, and cerebellar/brainstem hypoplasia.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for TUBB3-related Tubulinopathy Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

13
Head and Neck 2
Facial Palsy HP:0010628 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Facial palsy (HP:0010628). HP:0010628 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy."
The primary TUBB3 series explicitly reports facial paralysis.
Microcephaly HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"At the extreme severe end of the spectrum, only one fetus was reported with microlissencephaly and corpus callosum agenesis, severe brain stem and cerebellar hypoplasia, and dysmorphic basal ganglia"
GeneReviews confines this observation to one fetus at the severe end of the TUBB3 spectrum.
Musculoskeletal 1
Spasticity HP:0001257 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spasticity (HP:0001257). HP:0001257 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Supportive management, including an individualized therapy plan that includes physical therapy to manage the complications of spasticity"
GeneReviews explicitly includes management of spasticity in tubulinopathy supportive care.
Nervous System 5
Abnormal Corpus Callosum Morphology HP:0001273 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal corpus callosum morphology (HP:0001273). HP:0001273 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts"
Documents corpus callosum and commissural tract dysgenesis as a TUBB3 neuroimaging feature.
Cerebellar Hypoplasia HP:0001321 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebellar hypoplasia (HP:0001321). HP:0001321 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30016746 SUPPORT Human Clinical
"cerebellar hypoplasia or dysplasia and dysmorphism of the hind-brain structures"
Documents cerebellar hypoplasia/dysplasia and hindbrain dysmorphism as tubulinopathy hallmarks.
Dysmorphic Basal Ganglia Abnormal basal ganglia morphology HP:0002134 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal basal ganglia morphology (HP:0002134). HP:0002134 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:24860126 SUPPORT Human Clinical
"Dysmorphic basal ganglia are the hallmark of tubulinopathies (found in 75% of cases)"
Establishes dysmorphic basal ganglia as the imaging hallmark of tubulinopathies, present in the majority of cases.
Intellectual Disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"some also result in intellectual and behavioral impairments"
Documents intellectual and behavioral impairment as a feature of a subset of TUBB3 syndrome patients.
Seizure HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Epilepsy varies significantly among affected individuals and is not necessarily determined by the severity of the cortical malformation, the gene involved, or the causative pathogenic variant"
GeneReviews documents epilepsy as a variable tubulinopathy phenotype without licensing a TUBB3-specific frequency.
Other 5
Congenital Fibrosis of Extraocular Muscles HP:0001491 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Congenital fibrosis of extraocular muscles (HP:0001491). HP:0001491 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20829227 SUPPORT Human Clinical
"the ocular motility disorder, congenital fibrosis of the extraocular muscle type 3 (CFEOM3)"
Names CFEOM3 as the ocular phenotype in the originally described TUBB3 axon-guidance cohort.
Cortical Dysgyria HP:0032398 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dysgyria (HP:0032398). HP:0032398 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:24860126 SUPPORT Human Clinical
"By contrast, TUBB3 and TUBB5 mutations cause milder malformations with focal or multifocal polymicrogyria-like cortical dysplasia with abnormal and simplified gyral pattern"
Identifies polymicrogyria-like cortical dysplasia as the core cortical phenotype of TUBB3 mutations.
Pontine Hypoplasia Hypoplasia of the pons HP:0012110 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pontine hypoplasia, annotated with Hypoplasia of the pons (HP:0012110). HP:0012110 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:20829227 SUPPORT Human Clinical
"axonal abnormalities associated with pontocerebellar hypoplasia, but with no ocular motility defects, CFEOM3."
The clinical series explicitly identifies pontocerebellar hypoplasia in the TUBB3 cortical-malformation spectrum.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Brain stem & cerebellar vermian hypoplasia & basal ganglia dysmorphism; CFEOM"
The TUBB3 row in GeneReviews specifically lists brainstem and cerebellar vermian hypoplasia.
Brainstem Abnormalities Abnormal brainstem morphology HP:0002363 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal brainstem morphology (HP:0002363). HP:0002363 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35915025 SUPPORT Human Clinical
"cerebellar and brainstem hypoplasia"
Documents brainstem (and cerebellar) hypoplasia as a distinctive MRI feature of tubulinopathies.
Peripheral Neuropathy Peripheral axonal neuropathy HP:0003477 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Peripheral axonal neuropathy (HP:0003477). HP:0003477 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy."
Documents a later-onset axonal sensorimotor polyneuropathy as part of the TUBB3 syndrome spectrum.
🧬

Genetic Associations

1
TUBB3 (Causative)
Gene: TUBB3 (beta-III tubulin) hgnc:20772 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TUBB3 (beta-III tubulin), annotated with TUBB3 (hgnc:20772). hgnc:20772 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:20074521 SUPPORT Human Clinical
"We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific beta-tubulin isotype III, result in a spectrum of human nervous system disorders that we now call the TUBB3 syndromes."
Founding report establishing heterozygous TUBB3 missense mutations as the cause of the TUBB3 syndromes.
PMID:35915025 SUPPORT Human Clinical
"More than 100 MCD-associated mutations have been reported in TUBA1A, TUBB2B, or TUBB3 genes"
Establishes TUBB3 as one of the most frequently mutated tubulin genes in malformations of cortical development.
Variants (1)
TUBB3 p.Arg262His Pathogenic
Gene: TUBB3 hgnc:20772 HUGO Gene Nomenclature Committee (hgnc) Relation: this variant is in this gene This variant is in TUBB3 (hgnc:20772). hgnc:20772 is a gene from the HUGO Gene Nomenclature Committee.
A recurrent CFEOM3-associated missense change at the kinesin–microtubule interface. Recombinant-mutant and mouse rescue experiments show impaired kinesin motility/ATPase activity and axonal growth, linking this allele to the axon-guidance arm.
Show evidence (1 reference)
PMID:26775887 SUPPORT In Vitro
"the disease-associated TUBB3 mutations R262H and R262A impair the motility and ATPase activity of the kinesin motor"
Direct functional evidence for the p.Arg262His kinesin-interface defect.
💊

Medical Actions

3
CFEOM3 ophthalmologic management
Action: surgical procedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is surgical procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Individuals with CFEOM3 may require nonsurgical or surgical ophthalmologic management. These approaches address ocular manifestations rather than the underlying neurodevelopmental mechanism.
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Those with congenital fibrosis of the extraocular muscles may require nonsurgical and/or surgical treatment."
GeneReviews supports surgical or nonsurgical management for CFEOM.
Supportive and Rehabilitative Care
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Multidisciplinary supportive care including developmental, physical, and occupational therapy for individuals with cortical involvement, intellectual disability, or polyneuropathy, and anti-seizure medication where epilepsy is present.
Show evidence (2 references)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Supportive management, including an individualized therapy plan that includes physical therapy to manage the complications of spasticity, occupational therapy, speech therapy, and vision therapy for oculomotor deficits and/or strabismus should begin at the time of diagnosis"
GeneReviews supports early individualized multidisciplinary therapies.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Seizures are treated with anti-seizure medications based on the specific seizure type."
Supports the conditional antiseizure-management component.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Genetic counseling should address autosomal-dominant inheritance, the predominantly de novo occurrence of tubulinopathy variants, parental testing, and recurrence risk.
Show evidence (3 references)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"More than 95% of individuals diagnosed with a tubulinopathy have a de novo pathogenic variant in TUBA1A, TUBB2A, TUBB2B, TUBB3, TUBB (TUBB5), or TUBG1."
Supports counseling about the predominantly de novo autosomal-dominant occurrence.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Rarely, an individual diagnosed with a tubulinopathy has an affected parent. These individuals generally have either a TUBB3 or (less frequently) TUBB2B pathogenic variant."
GeneReviews identifies TUBB3 as the principal exception to the predominantly de novo pattern.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"molecular genetic testing is recommended for the parents of the proband to confirm their genetic status and to allow reliable recurrence risk counseling."
Supports parental testing and recurrence-risk counseling.
🔬

Diagnosis

2
Brain and cranial-nerve magnetic resonance imaging
MRI defines the cortical gyral pattern and evaluates the corpus callosum, basal ganglia, cerebellum, brainstem, and cranial nerves; the combination helps distinguish the cortical-malformation and CFEOM3-predominant arms.
magnetic resonance imaging NCIT:C16809 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts."
Supports MRI assessment of cranial nerves and commissural/long-tract abnormalities.
Molecular confirmation of a heterozygous TUBB3 pathogenic variant
Molecular testing using a tubulinopathy or cortical-malformation panel, or exome/genome sequencing, establishes the genetic diagnosis and informs parental testing and recurrence-risk counseling.
genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Molecular genetic testing approaches can include a combination of gene-targeted testing (multigene panel) and comprehensive genomic testing (exome sequencing, genome sequencing)."
GeneReviews recommends panel or genomic approaches for molecular diagnosis.
📈

Progression

2
Congenital neurodevelopmental presentation
Age: Prenatal period to infancy
Structural brain and cranial-nerve abnormalities arise during development; the phenotype varies by allele between a CFEOM3/axon-guidance presentation and a cortical-malformation presentation that may lack ocular dysmotility.
Show evidence (1 reference)
PMID:20829227 SUPPORT Human Clinical
"nine patients that all share cortical disorganization, axonal abnormalities associated with pontocerebellar hypoplasia, but with no ocular motility defects, CFEOM3."
Documents congenital cortical and axonal malformations without CFEOM3 in the cortical-malformation cohort.
Later neurologic course in some axon-guidance variants
Age: Later childhood to adulthood
Some individuals develop later-onset axonal sensorimotor polyneuropathy; this is variant-dependent rather than a universal progressive phase.
Show evidence (1 reference)
PMID:20074521 SUPPORT Human Clinical
"some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy."
Directly supports a later-onset neuropathy in a subset.
⚖️

Clinical Burden

High
Burden ranges widely with the structural brain phenotype. Cortical forms can cause severe motor and intellectual disability and epilepsy, while milder axon-guidance forms may survive into adulthood but require ophthalmologic, developmental, and sometimes neuropathy care.
Show evidence (1 reference)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"While most affected individuals have severe-to-profound intellectual disability, a minority have less extensive cortical malformations that result in only moderate intellectual disability, and a few have limited malformations that allow near-normal cognitive abilities."
GeneReviews documents the broad severity spectrum and substantial cognitive burden.
🐁

Animal Models

1
Tubb3 knock-in axon-guidance mouse
The knock-in mouse reproduces axon-guidance defects without the cortical cell-migration abnormalities seen in human cortical-malformation variants, making it informative for the CFEOM3 arm but incomplete for the full spectrum.
Species
Mouse (Mus musculus)
Genotype
Tubb3 knock-in disease model
Pathograph links
Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure partially recapitulates fidelity: moderate The knock-in model reproduces the axon-guidance failure central to the CFEOM3 arm.
Limitations: The cited report establishes axon-guidance defects but does not show that every molecular feature or human cranial dysinnervation outcome is reproduced.
Show evidence (1 reference)
PMID:20074521 SUPPORT Model Organism
"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."
Directly supports partial recapitulation of the axon-guidance mechanism.
Impaired Microtubule-Dependent Neuronal Migration fails to recapitulate fidelity: low The model does not reproduce the cortical neuronal-migration arm of human TUBB3 disease.
Limitations: Absence of cortical cell-migration abnormalities makes this model unsuitable for validating the cortical-malformation arm.
Show evidence (1 reference)
PMID:20074521 NO_EVIDENCE Model Organism
"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."
The reported negative finding directly substantiates failure to recapitulate neuronal migration abnormalities.
Show evidence (1 reference)
PMID:20074521 SUPPORT Model Organism
"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."
Defines both the model's mechanistic fidelity and its cortical-migration limitation.
{ }

Source YAML

click to show 
name: TUBB3-related Tubulinopathy
creation_date: "2026-06-11T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: TUBB3-related tubulinopathy
  term:
    id: MONDO:0100154
    label: TUBB3-related tubulinopathy
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We report that eight heterozygous missense mutations in TUBB3, encoding
      the neuron-specific beta-tubulin isotype III, result in a spectrum of
      human nervous system disorders that we now call the TUBB3 syndromes.
    explanation: >-
      The founding TUBB3 syndrome report establishes heterozygous missense
      mutations as sufficient to cause the disorder, supporting autosomal
      dominant inheritance.
description: >-
  TUBB3-related tubulinopathy is a neurodevelopmental disorder caused by
  heterozygous missense mutations in TUBB3, which encodes the neuron-specific
  beta-tubulin isotype III. Beta-III tubulin pairs with alpha-tubulin to form
  the heterodimers that polymerize into the highly dynamic neuronal
  microtubules required for axon outgrowth, growth-cone guidance, and
  microtubule-based neuronal migration. Unlike the alpha-tubulin (TUBA1A) and
  beta-tubulin (TUBB2B) disorders, in which cortical migration failure is the
  dominant defect, TUBB3 disease is distinguished by two separable, mutation-class
  dependent mechanistic arms that share the same upstream tubulin lesion. In one
  arm, kinesin-interaction-deficient mutations impair the motility of kinesin
  motors on microtubules and produce axon guidance failure in cranial motor
  neurons, causing hypoplasia of the oculomotor and other cranial nerves with the
  ocular motility disorder congenital fibrosis of the extraocular muscles type 3
  (CFEOM3), together with corpus callosum and commissural tract dysgenesis and,
  in some individuals, facial weakness and a later-onset axonal sensorimotor
  polyneuropathy. In the other arm, mutations that alter microtubule dynamics
  impair radial neuronal migration and produce malformations of cortical
  development — cortical disorganization, polymicrogyria-like cortical dysplasia,
  and pontocerebellar hypoplasia — often without ocular motility defects. Shared
  tubulinopathy imaging hallmarks include dysmorphic basal ganglia, midline
  commissural hypoplasia or agenesis, and cerebellar and brainstem hypoplasia.
  TUBB3 is modeled here as its own beta-III-tubulin pathomechanism entry rather
  than lumped under generic lissencephaly or polymicrogyria, because its central
  skeleton uniquely couples a kinesin-dependent axon guidance / cranial
  dysinnervation arm to the broader microtubule-dependent neuronal migration
  family that includes TUBA1A, TUBB2B, TUBB5, and TUBG1.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0013541
      label: complex cortical dysplasia with other brain malformations 1
    mapping_predicate: skos:narrowMatch
    mapping_source: MONDO
    mapping_justification: >-
      CDCBM1 is MONDO's TUBB3-specific cortical-malformation concept. This entry
      curates that presentation as its Cortical Dyslamination / Cortical
      Dysgyria arm, alongside the axon-guidance arm, so CDCBM1 is subsumed by
      this entry's broader disease_term MONDO:0100154 rather than equivalent to
      it.
  - term:
      id: MONDO:0010912
      label: fibrosis of extraocular muscles, congenital, 3A, with or without extraocular involvement
    mapping_predicate: skos:narrowMatch
    mapping_source: MONDO
    mapping_justification: >-
      CFEOM3A is MONDO's TUBB3-specific ocular-motility concept and is curated
      here as the Congenital Fibrosis of Extraocular Muscles phenotype
      downstream of this entry's axon-guidance arm. narrowMatch because this
      entry spans the full TUBB3 syndrome, of which CFEOM3 is the ocular
      component.
parents:
- congenital nervous system disorder
- disorder of development or morphogenesis
- hereditary neurological disease
- neuronal migration disorder
references:
- reference: PMID:20074521
  title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
- reference: PMID:20829227
  title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
- reference: PMID:26775887
  title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
- reference: PMID:30016746
  title: "Tubulin genes and malformations of cortical development."
- reference: PMID:35915025
  title: "Tubulin mutations in human neurodevelopmental disorders."
- reference: PMID:41152456
  title: "Expanding genetic and clinical spectra of β-tubulinopathies: A Korean study."
- reference: PMID:41153399
  title: "The p.Ile202Thr Substitution in TUBB2B Can Be Associated with Syndromic Presentation of Congenital Fibrosis of the Extraocular Muscles."
- reference: PMID:42593952
  title: "Developmental Profiles Associated with TUBA1A, TUBB2A, TUBB2B, and TUBB3 Tubulinopathy Conditions."
- reference: PMID:42310787
  title: "Identification of tubulin gene variants in patients with dandy-walker malformation: expanding the spectrum of tubulinopathies."
- reference: PMID:24860126
  title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
- reference: PMID:27010057
  title: Tubulinopathies Overview.
  tags:
  - GeneReviews
- reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
  title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
  tags:
  - GeneReviews
pathophysiology:
- name: Altered Beta-III Tubulin (TUBB3) Function
  role: TRIGGER
  biological_scale: MOLECULAR
  conforms_to: "microtubule_dependent_neuronal_migration_failure#Microtubule Apparatus Perturbation"
  description: >-
    Heterozygous missense mutations in TUBB3 alter the neuron-specific beta-III
    tubulin isotype. Disease-associated substitutions reduce the abundance of
    functional alpha/beta-tubulin heterodimers and alter the dynamic instability
    of the microtubules that incorporate beta-III tubulin. Different residues
    perturb distinct microtubule properties — some alter the resistance of
    microtubules to depolymerization while a subset disrupts the interaction of
    microtubules with kinesin motors — establishing altered beta-III tubulin
    function as the shared initiating molecular lesion that feeds the divergent
    axon-guidance and neuronal-migration arms of the disorder.
  genetic_context:
    functional_impact_category: DOMINANT_NEGATIVE
    variant_origin: DE_NOVO
    zygosity: HETEROZYGOUS
    allele_type: missense
    description: >-
      All reported disease alleles are heterozygous missense substitutions. The
      founding functional study showed that although the substitutions impair
      heterodimer formation, the mutant heterodimers that do fold still
      polymerize into microtubules, where they alter dynamic instability and, for
      a subset of residues, disrupt the microtubule-kinesin interaction. A mutant
      subunit that incorporates into the polymer and degrades a motor-binding
      surface acts on the wild-type polymer rather than merely subtracting one
      gene dose, which is why the category is DOMINANT_NEGATIVE and not
      haploinsufficiency. Some alleles are inherited from a mildly affected or
      unaffected parent, and one maternally inherited TUBB3 c.211G>A allele has
      been reported with milder features.
  cell_types:
  - preferred_term: migrating and post-mitotic neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: tubulin heterodimer assembly
    term:
      id: GO:0007021
      label: tubulin complex assembly
    modifier: DECREASED
  - preferred_term: microtubule cytoskeleton organization
    term:
      id: GO:0000226
      label: microtubule cytoskeleton organization
    modifier: DYSREGULATED
  genes:
  - preferred_term: TUBB3
    term:
      id: hgnc:20772
      label: TUBB3
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We show that the disease-associated mutations can impair tubulin
      heterodimer formation in vitro, although folded mutant heterodimers can
      still polymerize into microtubules.
    explanation: >-
      Establishes impaired tubulin heterodimer formation as the molecular lesion
      caused by TUBB3 mutations, while showing the residual heterodimers still
      polymerize.
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Modeling each mutation in yeast tubulin demonstrates that all alter
      dynamic instability whereas a subset disrupts the interaction of
      microtubules with kinesin motors.
    explanation: >-
      Shows that all TUBB3 mutations alter microtubule dynamic instability while
      only a subset additionally disrupts kinesin-microtubule interaction,
      establishing the basis for the two mechanistic arms.
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      the mutated βIII-tubulin causing the MCD phenotype results in a reduction
      of heterodimer formation, yet produce correctly formed microtubules (MTs)
      in mammalian cells
    explanation: >-
      Confirms that cortical-malformation-causing TUBB3 mutations reduce
      heterodimer formation while still producing microtubules.
  - reference: PMID:41152456
    reference_title: "Expanding genetic and clinical spectra of β-tubulinopathies: A Korean study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most variants were de novo, but one was a maternally inherited variant,
      c.211 G > A in TUBB3, which was associated with milder features.
    explanation: >-
      Qualifies the de novo variant_origin recorded on this node: a minority of
      TUBB3 alleles are inherited from a mildly affected or unaffected parent,
      and the inherited allele in this cohort tracked with a milder phenotype.
  downstream:
  - target: Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
    description: >-
      Kinesin-interaction-deficient TUBB3 mutations impair kinesin motility on
      microtubules and disrupt axon guidance in cranial motor neurons.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Modeling each mutation in yeast tubulin demonstrates that all alter
        dynamic instability whereas a subset disrupts the interaction of
        microtubules with kinesin motors.
      explanation: Directly supports the variant-specific kinesin-interaction branch.
  - target: Impaired Microtubule-Dependent Neuronal Migration
    description: >-
      Microtubule-dynamics-altering TUBB3 mutations impair the
      microtubule-dependent nucleokinesis required for radial cortical neuronal
      migration.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20829227
      reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        MCD mutations can alter the resistance of MTs to depolymerization
      explanation: Supports altered microtubule behavior in MCD variants; the full route to neuronal migration failure remains incompletely resolved.
  - target: Cerebellar Hypoplasia
    description: TUBB3 cortical-malformation variants are associated with pontocerebellar hypoplasia through unresolved developmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20829227
      reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        nine patients that all share cortical disorganization, axonal abnormalities
        associated with pontocerebellar hypoplasia
      explanation: Documents the TUBB3-associated endpoint but not the causal intermediates.
  - target: Pontine Hypoplasia
    description: TUBB3 cortical-malformation variants are associated with pontine hypoplasia through unresolved developmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20829227
      reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        nine patients that all share cortical disorganization, axonal abnormalities
        associated with pontocerebellar hypoplasia
      explanation: Documents the TUBB3-associated pontine endpoint but not the causal intermediates.
  - target: Dysmorphic Basal Ganglia
    description: TUBB3 dysfunction is associated with basal-ganglia dysmorphism through unresolved developmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
      reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Brain stem & cerebellar vermian
        hypoplasia & basal ganglia
        dysmorphism; CFEOM
      explanation: GeneReviews lists the TUBB3-associated endpoint without resolving its mechanism.
  - target: Brainstem Abnormalities
    description: TUBB3 dysfunction is associated with brainstem hypoplasia through unresolved developmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
      reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Brain stem & cerebellar vermian
        hypoplasia & basal ganglia
        dysmorphism; CFEOM
      explanation: GeneReviews lists the TUBB3-associated endpoint without resolving its mechanism.
  - target: Intellectual Disability
    description: Some TUBB3 variants produce intellectual impairment through unresolved neurodevelopmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        some also result in intellectual and behavioral impairments
      explanation: Establishes a variant-dependent human outcome without specifying its complete causal route.
  - target: Peripheral Neuropathy
    description: Some TUBB3 variants produce later-onset axonal sensorimotor polyneuropathy through unresolved intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        some also result in intellectual and behavioral impairments, facial
        paralysis, and/or later-onset axonal sensorimotor polyneuropathy.
      explanation: Establishes a variant-dependent human outcome without specifying its complete causal route.
  - target: Microcephaly
    description: A severe fetal TUBB3 cortical-malformation presentation included microcephaly through unresolved developmental intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
      reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        At the extreme severe end of the spectrum, only one fetus was reported with microlissencephaly and corpus callosum agenesis,
        severe brain stem and cerebellar hypoplasia, and dysmorphic basal ganglia
      explanation: The GeneReview documents a single severe fetal TUBB3 presentation; the causal intermediates and generalizability are unresolved.
- name: Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
  role: CENTRAL_EFFECTOR
  biological_scale: CELLULAR
  conforms_to: "microtubule_dependent_neuronal_migration_failure#Axon Guidance and Projection Wiring Defects"
  description: >-
    In the axon-guidance arm, TUBB3 mutations that affect residues mediating the
    kinesin-microtubule interface (notably R262) impair the motility and ATPase
    activity of kinesin motors moving along microtubules. Because beta-III
    tubulin is expressed most highly during axon outgrowth, this defect
    compromises kinesin-dependent axonal transport and growth-cone dynamics,
    producing axon guidance and projection-maintenance failure in the absence of
    overt cortical migration abnormalities — the mechanism underlying the
    cranial dysinnervation phenotype.
  cell_types:
  - preferred_term: developing neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: cranial motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: microtubule-based movement
    term:
      id: GO:0007018
      label: microtubule-based movement
    modifier: DYSREGULATED
  - preferred_term: neuron projection guidance
    term:
      id: GO:0097485
      label: neuron projection guidance
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      A knock-in disease mouse model reveals axon guidance defects without
      evidence of cortical cell migration abnormalities.
    explanation: >-
      A TUBB3 knock-in mouse shows that the axon-guidance arm can occur
      independently of cortical migration failure, defining it as a separable
      mechanistic branch.
  - reference: PMID:26775887
    reference_title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      the disease-associated TUBB3 mutations R262H and R262A impair the motility
      and ATPase activity of the kinesin motor
    explanation: >-
      Direct biochemical demonstration that CFEOM3-associated TUBB3 mutations
      impair kinesin motility and ATPase activity, the molecular basis of the
      axon-guidance arm.
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These findings demonstrate that normal TUBB3 is required for axon guidance
      and maintenance in mammals.
    explanation: >-
      Establishes the requirement for normal TUBB3 in axon guidance and
      maintenance, the process disrupted in this arm.
  downstream:
  - target: Cranial Motor Nerve Maldevelopment and Ocular Dysmotility
    description: >-
      Axon guidance failure in cranial motor neurons leads to hypoplasia of the
      oculomotor and other cranial nerves and to commissural tract dysgenesis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:26775887
      reference_title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        in a CFEOM3 mouse model expressing the same mutation, overexpressing the
        suppressor mutant kinesin restores axonal growth in vivo.
      explanation: Rescue of axonal growth by restoring the kinesin–microtubule interface supports this causal transition.
- name: Cranial Motor Nerve Maldevelopment and Ocular Dysmotility
  role: DOWNSTREAM
  biological_scale: TISSUE
  description: >-
    Failure of kinesin-dependent axon guidance in cranial motor neurons produces
    hypoplasia of the oculomotor (and trochlear/abducens) nerves and dysgenesis
    of the corpus callosum, anterior commissure, and corticospinal tracts. The
    misinnervation of the extraocular muscles manifests clinically as congenital
    fibrosis of the extraocular muscles type 3 (CFEOM3), a restrictive
    non-progressive ocular motility disorder, and may be accompanied by facial
    weakness and a later-onset axonal sensorimotor polyneuropathy.
  cell_types:
  - preferred_term: cranial motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: neuron projection guidance
    term:
      id: GO:0097485
      label: neuron projection guidance
    modifier: DECREASED
  - preferred_term: neuron projection morphogenesis
    term:
      id: GO:0048812
      label: neuron projection morphogenesis
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neuroimaging reveals a spectrum of abnormalities including hypoplasia of
      oculomotor nerves and dysgenesis of the corpus callosum, anterior
      commissure, and corticospinal tracts.
    explanation: >-
      Documents oculomotor nerve hypoplasia and commissural/corticospinal tract
      dysgenesis as the imaging correlates of the cranial axon-guidance defect.
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutations in the TUBB3 gene, encoding β-tubulin isotype III, were recently
      shown to be associated with various neurological syndromes which all have
      in common the ocular motility disorder, congenital fibrosis of the
      extraocular muscle type 3 (CFEOM3)
    explanation: >-
      Establishes CFEOM3 in the originally described axon-guidance-associated
      TUBB3 syndromes; other TUBB3 cortical-malformation variants can lack it.
  downstream:
  - target: Congenital Fibrosis of Extraocular Muscles
    description: Cranial motor dysinnervation produces the CFEOM3 ocular phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:26775887
      reference_title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In CFEOM3, the oculomotor nervous system develops abnormally due to
        impaired axon guidance and maintenance
      explanation: Directly states the cranial axon-guidance basis of CFEOM3.
  - target: Abnormal Corpus Callosum Morphology
    description: TUBB3 axon-guidance disruption is associated with commissural tract dysgenesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Neuroimaging reveals a spectrum of abnormalities including hypoplasia of
        oculomotor nerves and dysgenesis of the corpus callosum, anterior
        commissure, and corticospinal tracts.
      explanation: Documents commissural dysgenesis in the axon-guidance syndrome while leaving the intervening developmental route unspecified.
- name: Impaired Microtubule-Dependent Neuronal Migration
  role: CENTRAL_EFFECTOR
  biological_scale: CELLULAR
  conforms_to: "microtubule_dependent_neuronal_migration_failure#Microtubule-Based Neuronal Motility Failure"
  description: >-
    In the cortical arm, TUBB3 mutations that alter microtubule dynamics impair
    the microtubule-based nucleokinesis and radial migration of cortical
    neurons. Patient fibroblasts carrying malformation-of-cortical-development
    mutations show altered resistance of microtubules to depolymerization,
    contrasting with the increased microtubule stability seen with CFEOM3
    mutations, so that the migration defect arises from a distinct biophysical
    perturbation of the same microtubule apparatus.
  cell_types:
  - preferred_term: migrating cortical neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DECREASED
  - preferred_term: microtubule-based movement
    term:
      id: GO:0007018
      label: microtubule-based movement
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the spectrum of TUBB3-related phenotype is broader than previously
      described and includes malformations of cortical development (MCD)
      associated with neuronal migration and differentiation defects, axonal
      guidance and tract organization impairment
    explanation: >-
      Establishes that TUBB3 mutations cause malformations of cortical
      development associated with neuronal migration and differentiation
      defects, the cortical arm of the disorder.
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      MCD mutations can alter the resistance of MTs to depolymerization
    explanation: >-
      Shows that cortical-malformation TUBB3 mutations alter microtubule
      stability, the biophysical perturbation underlying the migration defect.
  - reference: PMID:35915025
    reference_title: "Tubulin mutations in human neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      abnormal corticogenesis due to impaired migration or lamination and
      abnormal growth cone dynamics of projecting and callosal axons
    explanation: >-
      Frames the cortical consequence of tubulinopathy mutations as impaired
      migration/lamination together with abnormal axonal growth-cone dynamics.
  downstream:
  - target: Cortical Dyslamination
    description: >-
      Failed microtubule-dependent migration leaves cortical neurons
      mispositioned, producing abnormal cortical lamination and gyration.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - abnormal neuronal positioning and cortical lamination
    evidence:
    - reference: PMID:20829227
      reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        includes malformations of cortical development (MCD) associated with
        neuronal migration and differentiation defects, axonal guidance and
        tract organization impairment.
      explanation: Directly associates TUBB3 cortical malformation with neuronal migration and differentiation defects.
- name: Cortical Dyslamination
  role: DOWNSTREAM
  biological_scale: TISSUE
  conforms_to: "microtubule_dependent_neuronal_migration_failure#Cortical Dyslamination and Neuronal Ectopia"
  description: >-
    Impaired migration of cortical neurons disrupts cortical lamination,
    producing cortical disorganization and focal or multifocal dysgyria with an
    abnormal and simplified gyral pattern.
  cell_types:
  - preferred_term: cortical neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: cerebral cortex development
    term:
      id: GO:0021987
      label: cerebral cortex development
    modifier: DYSREGULATED
  - preferred_term: neuron migration
    term:
      id: GO:0001764
      label: neuron migration
    modifier: DECREASED
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      all share cortical disorganization, axonal abnormalities associated with
      pontocerebellar hypoplasia, but with no ocular motility defects, CFEOM3
    explanation: >-
      Documents the cortical-arm phenotype of cortical disorganization with
      pontocerebellar hypoplasia occurring without the ocular motility defect.
  - reference: PMID:24860126
    reference_title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      By contrast, TUBB3 and TUBB5 mutations cause milder malformations with
      focal or multifocal polymicrogyria-like cortical dysplasia with abnormal
      and simplified gyral pattern
    explanation: >-
      Characterizes the TUBB3 cortical malformation as milder polymicrogyria-like
      cortical dysplasia with simplified gyration, distinct from TUBA1A
      lissencephaly.
  - reference: PMID:35915025
    reference_title: "Tubulin mutations in human neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional distinctive MRI features include dysmorphism of the basal
      ganglia, midline commissural structure hypoplasia or agenesis, and
      cerebellar and brainstem hypoplasia
    explanation: >-
      Establishes the shared tubulinopathy imaging accompaniments — dysmorphic
      basal ganglia, commissural hypoplasia, and cerebellar/brainstem hypoplasia.
  downstream:
  - target: Cortical Dysgyria
    description: Cortical dyslamination manifests as abnormal and simplified gyration.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24860126
      reference_title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        TUBB3 and TUBB5 mutations cause milder malformations with focal or
        multifocal polymicrogyria-like cortical dysplasia with abnormal and
        simplified gyral pattern.
      explanation: Directly supports the TUBB3 dysgyria phenotype.
phenotypes:
- name: Congenital Fibrosis of Extraocular Muscles
  description: >-
    Congenital fibrosis of the extraocular muscles type 3 (CFEOM3), a restrictive
    non-progressive ocular motility disorder caused by maldevelopment of the
    oculomotor system, is characteristic of the TUBB3 axon-guidance arm but may
    be absent in the cortical-malformation arm.
  phenotype_term:
    preferred_term: Congenital fibrosis of extraocular muscles
    term:
      id: HP:0001491
      label: Congenital fibrosis of extraocular muscles
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the ocular motility disorder, congenital fibrosis of the extraocular
      muscle type 3 (CFEOM3)
    explanation: >-
      Names CFEOM3 as the ocular phenotype in the originally described TUBB3
      axon-guidance cohort.
- name: Abnormal Corpus Callosum Morphology
  description: >-
    The corpus callosum can be dysgenic, hypoplastic, or absent in the TUBB3
    spectrum, alongside abnormalities of other commissural tracts.
  phenotype_term:
    preferred_term: Abnormal corpus callosum morphology
    term:
      id: HP:0001273
      label: Abnormal corpus callosum morphology
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      dysgenesis of the corpus callosum, anterior commissure, and corticospinal
      tracts
    explanation: >-
      Documents corpus callosum and commissural tract dysgenesis as a TUBB3
      neuroimaging feature.
- name: Cortical Dysgyria
  description: >-
    Focal or multifocal cortical dysgyria with abnormal simplified gyration is
    characteristic of the TUBB3 migration arm. Older reports called this
    polymicrogyria-like cortical dysplasia.
  phenotype_term:
    preferred_term: Dysgyria
    term:
      id: HP:0032398
      label: Dysgyria
  evidence:
  - reference: PMID:24860126
    reference_title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      By contrast, TUBB3 and TUBB5 mutations cause milder malformations with
      focal or multifocal polymicrogyria-like cortical dysplasia with abnormal
      and simplified gyral pattern
    explanation: >-
      Identifies polymicrogyria-like cortical dysplasia as the core cortical
      phenotype of TUBB3 mutations.
- name: Cerebellar Hypoplasia
  description: >-
    Cerebellar hypoplasia or dysplasia, frequently with pontine hypoplasia, is a
    characteristic infratentorial accompaniment of the TUBB3 cortical
    malformation.
  phenotype_term:
    preferred_term: Cerebellar hypoplasia
    term:
      id: HP:0001321
      label: Cerebellar hypoplasia
  evidence:
  - reference: PMID:30016746
    reference_title: "Tubulin genes and malformations of cortical development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar hypoplasia or dysplasia and dysmorphism of the hind-brain
      structures
    explanation: >-
      Documents cerebellar hypoplasia/dysplasia and hindbrain dysmorphism as
      tubulinopathy hallmarks.
- name: Pontine Hypoplasia
  description: >-
    Pontine hypoplasia can accompany cerebellar vermian hypoplasia in the TUBB3
    cortical-malformation arm.
  phenotype_term:
    preferred_term: Pontine hypoplasia
    term:
      id: HP:0012110
      label: Hypoplasia of the pons
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      axonal abnormalities associated with pontocerebellar hypoplasia, but with no
      ocular motility defects, CFEOM3.
    explanation: The clinical series explicitly identifies pontocerebellar hypoplasia in the TUBB3 cortical-malformation spectrum.
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Brain stem & cerebellar vermian
      hypoplasia & basal ganglia
      dysmorphism; CFEOM
    explanation: The TUBB3 row in GeneReviews specifically lists brainstem and cerebellar vermian hypoplasia.
- name: Dysmorphic Basal Ganglia
  description: >-
    Dysmorphic basal ganglia, with fusion of the caudate nucleus and putamen and
    abnormalities of the internal capsule, are an imaging hallmark across
    tubulinopathies and are represented in the TUBB3 spectrum.
  phenotype_term:
    preferred_term: Abnormal basal ganglia morphology
    term:
      id: HP:0002134
      label: Abnormal basal ganglia morphology
  evidence:
  - reference: PMID:24860126
    reference_title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dysmorphic basal ganglia are the hallmark of tubulinopathies (found in
      75% of cases)
    explanation: >-
      Establishes dysmorphic basal ganglia as the imaging hallmark of
      tubulinopathies, present in the majority of cases.
- name: Brainstem Abnormalities
  description: >-
    Brainstem hypoplasia can accompany the cortical and cerebellar malformation
    pattern in the TUBB3 spectrum.
  phenotype_term:
    preferred_term: Abnormal brainstem morphology
    term:
      id: HP:0002363
      label: Abnormal brainstem morphology
  evidence:
  - reference: PMID:35915025
    reference_title: "Tubulin mutations in human neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      cerebellar and brainstem hypoplasia
    explanation: >-
      Documents brainstem (and cerebellar) hypoplasia as a distinctive MRI
      feature of tubulinopathies.
- name: Intellectual Disability
  description: >-
    Intellectual and behavioral impairment occurs in a subset of individuals
    with TUBB3 syndromes, more frequently in those with cortical involvement.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some also result in intellectual and behavioral impairments
    explanation: >-
      Documents intellectual and behavioral impairment as a feature of a subset
      of TUBB3 syndrome patients.
- name: Peripheral Neuropathy
  description: >-
    A later-onset axonal sensorimotor polyneuropathy occurs in some individuals,
    consistent with the role of TUBB3 in long-range axon maintenance.
  phenotype_term:
    preferred_term: Peripheral axonal neuropathy
    term:
      id: HP:0003477
      label: Peripheral axonal neuropathy
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some also result in intellectual and behavioral impairments, facial
      paralysis, and/or later-onset axonal sensorimotor polyneuropathy.
    explanation: >-
      Documents a later-onset axonal sensorimotor polyneuropathy as part of the
      TUBB3 syndrome spectrum.
- name: Facial Palsy
  description: Facial paralysis occurs in a subset of individuals with TUBB3-related syndromes.
  phenotype_term:
    preferred_term: Facial palsy
    term:
      id: HP:0010628
      label: Facial palsy
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some also result in intellectual and behavioral impairments, facial
      paralysis, and/or later-onset axonal sensorimotor polyneuropathy.
    explanation: The primary TUBB3 series explicitly reports facial paralysis.
- name: Seizure
  description: >-
    Epilepsy occurs variably across tubulinopathies and is not reliably predicted
    by the causative gene, variant, or cortical-malformation severity.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Epilepsy varies significantly among affected individuals and is not necessarily determined by the severity of the
      cortical malformation, the gene involved, or the causative pathogenic variant
    explanation: GeneReviews documents epilepsy as a variable tubulinopathy phenotype without licensing a TUBB3-specific frequency.
- name: Spasticity
  description: >-
    Spasticity can contribute to motor disability and requires early prevention
    of contractures, loss of range of motion, and secondary complications.
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Supportive management, including an individualized therapy plan that includes physical therapy to manage the
      complications of spasticity
    explanation: GeneReviews explicitly includes management of spasticity in tubulinopathy supportive care.
- name: Microcephaly
  description: >-
    Microcephaly has been reported at the extreme severe end of the TUBB3
    spectrum in a fetus with microlissencephaly and extensive hindbrain and
    basal-ganglia abnormalities; it is not presented as a general TUBB3 feature.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      At the extreme severe end of the spectrum, only one fetus was reported with microlissencephaly and corpus callosum agenesis,
      severe brain stem and cerebellar hypoplasia, and dysmorphic basal ganglia
    explanation: GeneReviews confines this observation to one fetus at the severe end of the TUBB3 spectrum.
genetic:
- name: TUBB3
  association: Causative
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: TUBB3 (beta-III tubulin)
    term:
      id: hgnc:20772
      label: TUBB3
  variants:
  - name: TUBB3 p.Arg262His
    description: >-
      A recurrent CFEOM3-associated missense change at the kinesin–microtubule
      interface. Recombinant-mutant and mouse rescue experiments show impaired
      kinesin motility/ATPase activity and axonal growth, linking this allele to
      the axon-guidance arm.
    gene:
      preferred_term: TUBB3
      term:
        id: hgnc:20772
        label: TUBB3
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:26775887
      reference_title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        the disease-associated TUBB3 mutations R262H and R262A impair the motility
        and ATPase activity of the kinesin motor
      explanation: Direct functional evidence for the p.Arg262His kinesin-interface defect.
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We report that eight heterozygous missense mutations in TUBB3, encoding
      the neuron-specific beta-tubulin isotype III, result in a spectrum of
      human nervous system disorders that we now call the TUBB3 syndromes.
    explanation: >-
      Founding report establishing heterozygous TUBB3 missense mutations as the
      cause of the TUBB3 syndromes.
  - reference: PMID:35915025
    reference_title: "Tubulin mutations in human neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      More than 100 MCD-associated mutations have been reported in TUBA1A,
      TUBB2B, or TUBB3 genes
    explanation: >-
      Establishes TUBB3 as one of the most frequently mutated tubulin genes in
      malformations of cortical development.
progression:
- phase: Congenital neurodevelopmental presentation
  age_range: Prenatal period to infancy
  notes: >-
    Structural brain and cranial-nerve abnormalities arise during development;
    the phenotype varies by allele between a CFEOM3/axon-guidance presentation
    and a cortical-malformation presentation that may lack ocular dysmotility.
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      nine patients that all share cortical disorganization, axonal abnormalities
      associated with pontocerebellar hypoplasia, but with no ocular motility
      defects, CFEOM3.
    explanation: Documents congenital cortical and axonal malformations without CFEOM3 in the cortical-malformation cohort.
- phase: Later neurologic course in some axon-guidance variants
  age_range: Later childhood to adulthood
  notes: >-
    Some individuals develop later-onset axonal sensorimotor polyneuropathy;
    this is variant-dependent rather than a universal progressive phase.
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some also result in intellectual and behavioral impairments, facial
      paralysis, and/or later-onset axonal sensorimotor polyneuropathy.
    explanation: Directly supports a later-onset neuropathy in a subset.
clinical_burden:
  burden_level: HIGH
  rationale: >-
    Burden ranges widely with the structural brain phenotype. Cortical forms can
    cause severe motor and intellectual disability and epilepsy, while milder
    axon-guidance forms may survive into adulthood but require ophthalmologic,
    developmental, and sometimes neuropathy care.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      While most affected individuals have severe-to-profound intellectual disability, a minority have less extensive
      cortical malformations that result in only moderate intellectual disability, and a few have limited malformations
      that allow near-normal cognitive abilities.
    explanation: GeneReviews documents the broad severity spectrum and substantial cognitive burden.
diagnosis:
- name: Brain and cranial-nerve magnetic resonance imaging
  description: >-
    MRI defines the cortical gyral pattern and evaluates the corpus callosum,
    basal ganglia, cerebellum, brainstem, and cranial nerves; the combination
    helps distinguish the cortical-malformation and CFEOM3-predominant arms.
  diagnosis_term:
    preferred_term: magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Neuroimaging reveals a spectrum of abnormalities including hypoplasia of
      oculomotor nerves and dysgenesis of the corpus callosum, anterior
      commissure, and corticospinal tracts.
    explanation: Supports MRI assessment of cranial nerves and commissural/long-tract abnormalities.
- name: Molecular confirmation of a heterozygous TUBB3 pathogenic variant
  description: >-
    Molecular testing using a tubulinopathy or cortical-malformation panel, or
    exome/genome sequencing, establishes the genetic diagnosis and informs
    parental testing and recurrence-risk counseling.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Molecular genetic testing approaches can include a combination of gene-targeted testing (multigene panel) and
      comprehensive genomic testing (exome sequencing, genome sequencing).
    explanation: GeneReviews recommends panel or genomic approaches for molecular diagnosis.
treatments:
- name: CFEOM3 ophthalmologic management
  description: >-
    Individuals with CFEOM3 may require nonsurgical or surgical ophthalmologic
    management. These approaches address ocular manifestations rather than the
    underlying neurodevelopmental mechanism.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Those with congenital fibrosis of the extraocular muscles may require nonsurgical and/or surgical treatment.
    explanation: GeneReviews supports surgical or nonsurgical management for CFEOM.
- name: Supportive and Rehabilitative Care
  description: >-
    Multidisciplinary supportive care including developmental, physical, and
    occupational therapy for individuals with cortical involvement, intellectual
    disability, or polyneuropathy, and anti-seizure medication where epilepsy is
    present.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Supportive management, including an individualized therapy plan that includes physical therapy to manage the
      complications of spasticity, occupational therapy, speech therapy, and vision therapy for oculomotor deficits
      and/or strabismus should begin at the time of diagnosis
    explanation: GeneReviews supports early individualized multidisciplinary therapies.
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Seizures are treated with anti-seizure medications based on the specific seizure type.
    explanation: Supports the conditional antiseizure-management component.
- name: Genetic Counseling
  description: >-
    Genetic counseling should address autosomal-dominant inheritance, the
    predominantly de novo occurrence of tubulinopathy variants, parental testing,
    and recurrence risk.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      More than 95% of individuals diagnosed with a tubulinopathy have a de novo pathogenic variant in
      TUBA1A, TUBB2A, TUBB2B, TUBB3, TUBB (TUBB5), or TUBG1.
    explanation: Supports counseling about the predominantly de novo autosomal-dominant occurrence.
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rarely, an individual diagnosed with a tubulinopathy has an affected parent. These individuals generally
      have either a TUBB3 or (less frequently) TUBB2B pathogenic variant.
    explanation: GeneReviews identifies TUBB3 as the principal exception to the predominantly de novo pattern.
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
    reference_title: "https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      molecular genetic testing is recommended for the parents of the proband to confirm their genetic status and to allow reliable recurrence risk counseling.
    explanation: Supports parental testing and recurrence-risk counseling.
experimental_models: []
animal_models:
- name: Tubb3 knock-in axon-guidance mouse
  species: Mouse (Mus musculus)
  genotype: Tubb3 knock-in disease model
  description: >-
    The knock-in mouse reproduces axon-guidance defects without the cortical
    cell-migration abnormalities seen in human cortical-malformation variants,
    making it informative for the CFEOM3 arm but incomplete for the full spectrum.
  modeled_mechanisms:
  - target: Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: The knock-in model reproduces the axon-guidance failure central to the CFEOM3 arm.
    limitations: >-
      The cited report establishes axon-guidance defects but does not show that
      every molecular feature or human cranial dysinnervation outcome is reproduced.
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        A knock-in disease mouse model reveals axon guidance defects without
        evidence of cortical cell migration abnormalities.
      explanation: Directly supports partial recapitulation of the axon-guidance mechanism.
  - target: Impaired Microtubule-Dependent Neuronal Migration
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: The model does not reproduce the cortical neuronal-migration arm of human TUBB3 disease.
    limitations: >-
      Absence of cortical cell-migration abnormalities makes this model
      unsuitable for validating the cortical-malformation arm.
    evidence:
    - reference: PMID:20074521
      reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
      supports: NO_EVIDENCE
      evidence_source: MODEL_ORGANISM
      snippet: >-
        A knock-in disease mouse model reveals axon guidance defects without
        evidence of cortical cell migration abnormalities.
      explanation: The reported negative finding directly substantiates failure to recapitulate neuronal migration abnormalities.
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      A knock-in disease mouse model reveals axon guidance defects without
      evidence of cortical cell migration abnormalities.
    explanation: Defines both the model's mechanistic fidelity and its cortical-migration limitation.
discussions:
- discussion_id: gap_tubb3_arm_genotype_phenotype_divergence
  prompt: >-
    Why do different TUBB3 missense mutations preferentially produce the
    kinesin-dependent axon guidance / CFEOM3 arm versus the microtubule-dynamics
    cortical migration arm, and what is the structural basis for this phenotypic
    divergence from a shared tubulin lesion?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
  - pathophysiology#Impaired Microtubule-Dependent Neuronal Migration
  rationale: >-
    CFEOM3-associated mutations increase microtubule stability and disrupt
    kinesin interaction, whereas malformation-of-cortical-development mutations
    alter microtubule resistance to depolymerization, and the two phenotypic
    profiles are largely non-overlapping. The residue-to-mechanism map is only
    partially resolved, so it is not yet possible to predict from genotype which
    arm will dominate, or whether some variants engage both arms simultaneously.
  evidence:
  - reference: PMID:20829227
    reference_title: "Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      MCD mutations can alter the resistance of MTs to depolymerization.
      Interestingly, this finding contrasts with the increased MT stability
      observed in the case of CFEOM3-related mutations.
    explanation: Directly supports distinct biophysical effects in the two clinical arms.
- discussion_id: gap_tubb3_kinesin_causality_for_cfeom
  prompt: >-
    Is disruption of the kinesin-microtubule interaction sufficient and necessary
    to cause CFEOM3, or is altered microtubule dynamic instability alone able to
    produce the axon guidance defect?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure
  rationale: >-
    Engineering a compensatory mutation in the kinesin L12 loop restores motility
    on R262 mutant microtubules and rescues axonal growth in a CFEOM3 mouse
    model, strongly supporting kinesin-microtubule disruption as causal for the
    axon-guidance arm. However, because all TUBB3 mutations also alter dynamic
    instability, the independent contribution of microtubule dynamics to the
    cranial dysinnervation phenotype is not fully excluded.
  evidence:
  - reference: PMID:26775887
    reference_title: "Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      in a CFEOM3 mouse model expressing the same mutation, overexpressing the
      suppressor mutant kinesin restores axonal growth in vivo.
    explanation: Rescue supports kinesin-interface causality while not excluding a parallel contribution from altered dynamics.
- discussion_id: gap_tubb3_cell_type_primacy_human_model_translatability
  prompt: >-
    For the TUBB3 cortical neuronal-migration arm, is the primary defect in
    post-mitotic migrating neurons or in apical/outer radial glial progenitors,
    and which features require human iPSC-derived cortical organoids or fetal
    tissue to resolve, given that the available knock-in disease mouse does not
    reproduce the human cortical malformation?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Altered Beta-III Tubulin (TUBB3) Function
  - pathophysiology#Impaired Microtubule-Dependent Neuronal Migration
  - pathophysiology#Cortical Dyslamination
  rationale: >-
    Human TUBB3 patients show cortical malformations (dyslamination,
    polymicrogyria-like cortex, callosal and pontocerebellar anomalies), yet the
    TUBB3 knock-in disease mouse reproduces the axon-guidance arm without
    cortical cell-migration abnormalities, so the cell population primarily
    responsible for the human cortical-migration arm — post-mitotic migrating
    neurons versus apical or outer radial glial progenitors — cannot be assigned
    from the available rodent model. As for the other tubulinopathies (TUBA1A,
    TUBB2A/TUBB2B, TUBB5), human cortical expansion depends on outer radial glia
    and fetal cortical organization that lissencephalic rodents do not fully
    represent, so resolving progenitor-primary versus migration-primary
    contributions requires human iPSC-derived cortical organoid or fetal-tissue
    benchmarks. Captured per the cortical-malformation epic (#4098/#4101)
    cell-type-ambiguity and human/model-mismatch curation guidance.
  evidence:
  - reference: PMID:20074521
    reference_title: "Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      A knock-in disease mouse model reveals axon guidance defects without
      evidence of cortical cell migration abnormalities.
    explanation: >-
      The TUBB3 knock-in mouse recapitulates the axon-guidance arm but not the
      cortical-migration malformation seen in human patients, making the human
      cortical-migration mechanism and its primary cell type a model-to-human
      translatability gap.
  - reference: PMID:28111201
    reference_title: Human iPSC-Derived Cerebral Organoids Model Cellular Features of Lissencephaly and Reveal Prolonged Mitosis of Outer Radial Glia.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      However, the mouse brain is naturally lissencephalic, suggesting that
      certain aspects of cortical development may not be adequately assessed in
      mice.
    explanation: >-
      Supports treating rodent-to-human translation as an explicit knowledge gap
      for the cortical-migration arm of tubulin-related malformations, including
      the contribution of human outer radial glia.
  proposed_experiments:
  - experiment_id: exp_tubb3_isogenic_cortical_organoid_celltype
    name: TUBB3 isogenic cortical-organoid cell-type-of-origin experiment
    description: >-
      Engineer recurrent cortical-malformation-associated TUBB3 missense
      variants into human iPSCs, correct patient-derived variants isogenically
      where available, and compare cortical organoid neuronal migration,
      radial-glial organization, microtubule dynamics, and outer-radial-glia
      mitosis to test whether the cortical-migration arm is primarily
      post-mitotic neuronal or also reflects apical/outer radial glial
      progenitor vulnerability not captured by the knock-in mouse.
    experiment_type:
      preferred_term: patient-derived cortical organoid perturbation experiment
    model_systems:
    - name: TUBB3 human iPSC-derived cortical organoid
      description: >-
        Three-dimensional human cortical organoid carrying a
        cortical-malformation-associated TUBB3 variant, with isogenic corrected
        and knock-in controls.
      experimental_model_type: ORGANOID
      namo_type: namo:Organoid
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      tissue_term:
        preferred_term: cerebral cortex
        term:
          id: UBERON:0000956
          label: cerebral cortex
      cell_types:
      - preferred_term: radial glial cell
        term:
          id: CL:0000681
          label: radial glial cell
      - preferred_term: migrating cortical neuron
        term:
          id: CL:0000540
          label: neuron
      conditions:
      - TUBB3-related tubulinopathy
      - malformation of cortical development
      - microtubule-dependent neuronal migration failure
      cell_source: Patient-derived or CRISPR-engineered human induced pluripotent stem cells
      culture_system: Three-dimensional cortical organoid with live-imaging migration assays
    perturbations:
    - name: TUBB3 variant correction or knock-in
      target: pathophysiology#Altered Beta-III Tubulin (TUBB3) Function
      genes:
      - preferred_term: TUBB3 (beta-III tubulin)
        term:
          id: hgnc:20772
          label: TUBB3
      description: >-
        Correct a patient TUBB3 variant or introduce a recurrent
        cortical-malformation-associated missense variant into an isogenic human
        iPSC background.
    readouts:
    - name: Cortical neuronal migration and progenitor organization
      target: pathophysiology#Impaired Microtubule-Dependent Neuronal Migration
      biological_processes:
      - preferred_term: neuron migration
        term:
          id: GO:0001764
          label: neuron migration
        modifier: DECREASED
      - preferred_term: microtubule cytoskeleton organization
        term:
          id: GO:0000226
          label: microtubule cytoskeleton organization
        modifier: DYSREGULATED
datasets: []
review_notes: >-
  Full REVIEW reconciled the entry with the TUBB3 primary cohorts and the
  Tubulinopathies Overview GeneReview. The umbrella disorder contains two
  allele-dependent presentations: CFEOM3/axon-guidance disease and cortical
  dysgyria, the latter sometimes lacking ocular motility abnormalities. The
  prior redundant generic ocular-motility phenotype was removed, corpus-callosum
  dysgenesis was mapped to the broader HPO parent rather than agenesis, and the
  older “polymicrogyria-like” label was normalized to abnormal cortical gyration
  in keeping with GeneReviews terminology. Causal edges are evidence-bearing;
  phenotype routes supported only at genotype/association level use
  INDIRECT_UNKNOWN_INTERMEDIATES and PARTIAL support. No disease-relevant public
  dataset or established human experimental model was identified; the knock-in
  mouse is retained with its explicit failure to reproduce human cortical
  migration abnormalities.
notes: >-
  Entry created from cortical-malformation epic 4098 (issue 4085), seeded from
  Romero, Bahi-Buisson & Francis 2018 (Sem Cell Dev Biol 76:33-75). Modeled as a
  coherent beta-III-tubulin (TUBB3) pathomechanism with two mutation-class
  dependent arms — a kinesin-dependent axon guidance / cranial dysinnervation
  (CFEOM3) arm and a microtubule-dynamics cortical neuronal migration arm — that
  share the upstream tubulin-heterodimer lesion. TUBB3 is deliberately split from
  the alpha-tubulin (TUBA1A) and other beta-tubulin (TUBB2B/TUBB5) tubulinopathies
  because its central skeleton uniquely couples a kinesin/axon-guidance arm to the
  shared microtubule apparatus; all conform to the
  microtubule_dependent_neuronal_migration_failure module, with the axon-guidance
  node conforming to that module's optional "Axon Guidance and Projection Wiring
  Defects" branch. The disease_term uses MONDO:0100154 "TUBB3-related
  tubulinopathy" (the issue's suggested MONDO:0008001 was verified with OAK to be
  "milia, multiple eruptive" and was not used). CFEOM3 is a congenital cranial
  dysinnervation disorder (CCDD); see also the Duane retraction syndrome issue
  (#2706) for the broader CCDD family. The Tubulinopathy/TUBA1A subtype in
  kb/disorders/Lissencephaly_Spectrum_Disorders.yaml mentions TUBB3 in passing;
  with this dedicated entry, that subtype should be annotated to point here in a
  follow-up. Well-established clinical features without an exact quotable abstract
  snippet in the cited papers (e.g. ptosis specifics) are
  summarized in node descriptions rather than asserted as separately evidenced
  phenotypes, pending sources with quotable text.
📚

References & Deep Research

References

12
PMID:20074521
Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance.
No top-level findings curated for this source.
PMID:20829227
Mutations in the neuronal ß-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects.
No top-level findings curated for this source.
PMID:26775887
Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface.
No top-level findings curated for this source.
PMID:30016746
Tubulin genes and malformations of cortical development.
No top-level findings curated for this source.
PMID:35915025
Tubulin mutations in human neurodevelopmental disorders.
No top-level findings curated for this source.
PMID:41152456
Expanding genetic and clinical spectra of β-tubulinopathies: A Korean study.
No top-level findings curated for this source.
PMID:41153399
The p.Ile202Thr Substitution in TUBB2B Can Be Associated with Syndromic Presentation of Congenital Fibrosis of the Extraocular Muscles.
No top-level findings curated for this source.
PMID:42593952
Developmental Profiles Associated with TUBA1A, TUBB2A, TUBB2B, and TUBB3 Tubulinopathy Conditions.
No top-level findings curated for this source.
PMID:42310787
Identification of tubulin gene variants in patients with dandy-walker malformation: expanding the spectrum of tubulinopathies.
No top-level findings curated for this source.
PMID:24860126
The wide spectrum of tubulinopathies: what are the key features for the diagnosis?
No top-level findings curated for this source.
PMID:27010057
Tubulinopathies Overview.
No top-level findings curated for this source.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf
No top-level findings curated for this source.