TUBG1-related Tubulinopathy

Mendelian MONDO:0014171 Pathograph 15 Show in embeddings browser congenital nervous system disorder disorder of development or morphogenesis hereditary neurological disease neuronal migration disorder

TUBG1-related tubulinopathy (CDCBM4) is a malformation of cortical development caused by heterozygous, typically de novo missense variants in TUBG1, which encodes gamma-tubulin 1. It is the gamma-tubulin member of the tubulinopathy grouping, and the distinction from its alpha- and beta-tubulin siblings is mechanistic rather than nominal. Alpha- and beta-tubulin form the heterodimer that polymerizes into the microtubule lattice, so a variant in either is incorporated into the polymer itself. Gamma-tubulin is not a lattice subunit at all: it is the core component of the gamma-tubulin ring complex (gamma-TuRC), the template that nucleates microtubules from the centrosome. The consequence of losing nucleation fidelity differs from the consequence of poisoning the polymer, and it shows in the imaging phenotype. The core radiological picture is a pachygyric cortex with a posterior-to-anterior gradient, lateral ventricles enlarged most over the posterior horns, and variably reduced white matter volume - with basal ganglia, brainstem and cerebellum often normal. Corpus-callosum morphology is variable: it was often normal in a dedicated series but was thick and dysmorphic in the less severe P478 case. The relative sparing of the basal ganglia is the strongest diagnostic discriminator because their dysmorphism is a near-signature finding in the alpha- and beta-tubulinopathies. This makes TUBG1 disease resemble LIS1/PAFAH1B1 lissencephaly more closely than it resembles its own gene family. Clinically, most reported individuals have severe motor and cognitive impairment with early-life seizures, though a mild end exists - one reported individual has autism, intellectual disability, later-onset well-controlled epilepsy, a normocephalic head and no detectable structural abnormality on neuroimaging. Functionally, the best-resolved lesion is a failure of post-mitotic neuronal locomotion rather than of progenitor proliferation: pathogenic variants reduce microtubule dynamics without producing major structural or functional centrosome defects, and mutant bipolar neurons position their centrosome correctly yet fail to initiate locomotion. A zebrafish somatic model additionally reports disrupted neurogenesis and a link to canonical Wnt/beta-catenin signaling; the tension between that and the mouse finding of intact proliferation is curated as an open discussion rather than smoothed over.

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1
Inheritance
4
Pathophys.
9
Phenotypes
2
Gaps
15
Pathograph
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Genes
3
Medical Actions
2
Models
14
References
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Inheritance

1
Autosomal dominant inheritance HP:0000006
Heterozygous, typically de novo missense variants. No biallelic or loss-of-function mechanism has been reported.
Autosomal dominant inheritance
Show evidence (4 references)
PMID:31086189 SUPPORT Human Clinical
"De novo heterozygous missense variants in the γ-tubulin gene TUBG1 have been linked to human malformations of cortical development associated with intellectual disability and epilepsy."
States the de novo heterozygous missense mechanism, supporting autosomal dominant, typically sporadic inheritance.
PMID:29706637 SUPPORT Human Clinical
"We here report eight additional patients with four novel heterozygous variants in TUBG1 identified by next-generation sequencing (NGS) analysis."
Confirms heterozygous variants across an independent eight-patient series.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"Tubulinopathies caused by pathogenic variants in TUBA1A, TUBB2A, TUBB2B, TUBB3, TUBB (TUBB5), or TUBG1 are inherited in an autosomal dominant manner."
GeneReviews explicitly includes TUBG1 among the autosomal-dominant tubulinopathies.
+ 1 more reference
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Discussions and Knowledge Gaps

2
Does pathogenic TUBG1 variation impair neurogenesis, or only the locomotion of neurons that were made normally?
HUMAN MODEL MISMATCH OPEN gap_tubg1_neurogenesis_versus_locomotion
Attached to
pathophysiology#Failure of Neuronal Locomotion Initiation pathophysiology#Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
Two model systems give opposite answers, and the disagreement is not cosmetic - it decides which module this disease belongs to. In mouse, in utero electroporation of four patient variants and a Tubg1 Y92C/+ knock-in show disrupted locomotion of newborn neurons without affecting progenitor proliferation; the paper's title states the point as "not neurogenesis". In zebrafish, somatic tubg1 mutation is reported to disrupt neurogenesis and brain development, mirroring microcephaly. The most likely reconciliation is the difference in allele class: the mouse work models heterozygous patient missense variants, while the zebrafish work is a somatic loss-of-function crispant, and gamma-tubulin is essential for mitosis, so removing it should impair proliferation even if a missense allele does not. If that is right, the zebrafish neurogenesis phenotype models gamma-tubulin deficiency rather than human TUBG1 disease. But it is not settled, and the human phenotype does include microcephaly, which a pure locomotion defect does not obviously explain. Resolving it requires a zebrafish or human model carrying the heterozygous missense allele rather than a null, with progenitor proliferation measured directly.
Proposed experiments
Allele-matched comparison of progenitor proliferation under TUBG1 missense versus null
exp_tubg1_missense_vs_null_progenitor_proliferation
In a single model system, compare a heterozygous patient missense allele against a loss-of-function allele, measuring progenitor proliferation, neuronal output and migration side by side, to test whether the neurogenesis phenotype is allele-class-dependent.
Decision criterion
If progenitor proliferation is impaired by the null but not by the heterozygous missense allele, the neurogenesis arm belongs to gamma-tubulin deficiency rather than to human TUBG1 disease, and the locomotion-only model stands. If the missense allele also impairs proliferation, this entry needs a progenitor branch and a second module conformance.
Would support
pathophysiology#Failure of Neuronal Locomotion Initiation
Show evidence (2 references)
PMID:31086189 SUPPORT Model Organism
"We show that TUBG1 mutants affect neuronal positioning, disrupting the locomotion of new-born neurons but without affecting progenitors' proliferation."
The mouse position: locomotion fails, proliferation does not.
PMID:39215931 REFUTE Model Organism
"We demonstrate that γ-tubulin deficiency disrupts neurogenesis and brain development, mirroring microcephaly phenotypes."
The zebrafish position, which contradicts the mouse claim that neurogenesis is spared - recorded as REFUTE against that specific claim, with the allele-class caveat argued in the rationale.
Why does a tubulin-gene lesion produce a LIS1-like imaging phenotype with often-spared basal ganglia, brainstem and cerebellum but variable corpus-callosum morphology, when the alpha- and beta-tubulinopathies often malform those structures?
KNOWLEDGE GAP OPEN gap_tubg1_imaging_signature_divergence
Attached to
pathophysiology#Posterior-Predominant Pachygyria with Spared Deep Structures pathophysiology#Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
This is the sharpest natural experiment available in the tubulinopathy grouping, and it is unresolved. Dysmorphic basal ganglia with a fused striatum are reported as pathognomonic in roughly three quarters of tubulinopathy cases and are one of the imaging features that raises the diagnosis at all - yet in TUBG1 disease those structures are often normal. The proposed explanation is that gamma-tubulin's job is microtubule nucleation rather than lattice assembly, so its failure does not perturb the same processes. That is plausible but currently an inference from function, not a demonstration: nobody has shown which developmental process in the basal ganglia and commissures requires lattice integrity but tolerates reduced nucleation fidelity. The practical consequence is diagnostic - a tubulin-gene disorder that looks like LIS1 on MRI will be missed by an imaging-led differential that treats dysmorphic basal ganglia as required.
Show evidence (4 references)
PMID:29706637 SUPPORT Human Clinical
"Basal ganglia, corpus callosum, brainstem, and cerebellum were often normal, in contrast to patients with variants in other tubulin genes where these structures are frequently malformed."
Establishes the divergence in imaging phenotype that this gap is about.
PMID:29706637 SUPPORT Other
"This difference may, at least in part, be explained by gamma-tubulin's physiological function in microtubule nucleation, which differs from that of alpha and beta-tubulin."
The proposed explanation, stated by its authors as partial and hedged, is why this remains an open gap.
PMID:41901019 SUPPORT Other
"basal ganglia dysmorphism with a fused striatum (pathognomonic in approximately 75% of cases)"
Quantifies how central basal ganglia dysmorphism is to tubulinopathy imaging generally, which is what makes its absence in TUBG1 notable and diagnostically hazardous.
+ 1 more reference
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Pathophysiology

4
Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
Heterozygous missense variants alter gamma-tubulin 1, the core component of the gamma-tubulin ring complex (gamma-TuRC) that templates microtubule nucleation at the centrosome. This is a categorically different lesion from the one carried by the alpha- and beta-tubulinopathies: gamma-tubulin is not a subunit of the microtubule lattice, so the defect is in how microtubules are started rather than in what they are built from. Expression of altered gamma-tubulin proteins in yeast disrupts normal microtubule behavior, and in subject-derived fibroblasts pathogenic variants reduce microtubule dynamics. The module's trigger node is nevertheless the correct conformance target: whichever way the microtubule apparatus is perturbed, the same downstream migration machinery fails.
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.
TUBG1 hgnc:12417 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves TUBG1 (hgnc:12417). hgnc:12417 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context allele_type: missense variant_origin: DE_NOVO zygosity: HETEROZYGOUS functional_impact_category: UNKNOWN
All reported alleles are heterozygous missense, with no nonsense, frameshift or deletion alleles, so haploinsufficiency is not the presumed mechanism. The mechanism class has not been resolved further, and the one experiment that would have discriminated it argues against the obvious candidate: if the variants acted by disabling the centrosome as a nucleating center, subject fibroblasts should show centrosome defects, and they do not. UNKNOWN records that the question was examined and remains open, rather than that it was never annotated.
microtubule nucleation GO:0007020 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated microtubule nucleation (GO:0007020). GO:0007020 is a biological process from the Gene Ontology. ↕ DYSREGULATED 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
gamma-tubulin ring complex GO:0000931 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves dysregulated gamma-tubulin ring complex (GO:0000931). GO:0000931 is a cellular component from the Gene Ontology.
Animal models
tubg1 somatic mutant zebrafish Zebrafish perturbs Somatic disruption of tubg1 perturbs the nucleator and produces neurodevelopmental phenotypes reported as recapitulating patient and mouse features.
Downstream
Reduced Microtubule Dynamics without Centrosome Structural Defect Altered gamma-tubulin reduces microtubule dynamics in patient cells while leaving centrosome structure and function grossly intact.
Show evidence (4 references)
PMID:23603762 SUPPORT Human Clinical
"Here we report the discovery of multiple pathogenic missense mutations in TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in KIF5C, in subjects with MCD."
The founding report establishing pathogenic TUBG1 missense mutations as a cause of malformations of cortical development.
PMID:23603762 SUPPORT In Vitro
"expression of altered γ-tubulin proteins in Saccharomyces cerevisiae disrupts normal microtubule behavior"
Shows that the disease-associated gamma-tubulin proteins perturb microtubule behavior in a simplified heterologous system.
PMID:40298439 SUPPORT Other
"The gamma-tubulin ring complex (γ-TuRC) plays a role in coordinating centrosome and spindle pole body formation during cell division. TUBG1 encodes a critical component of the γ-TuRC."
Identifies the gene product's role as a gamma-TuRC component, the basis for treating this as a nucleation lesion rather than a lattice-subunit lesion.
+ 1 more reference
Reduced Microtubule Dynamics without Centrosome Structural Defect
The cellular consequence is a quantitative slowing of microtubule dynamics, not a broken centrosome. Subject-derived fibroblasts carrying pathogenic TUBG1 variants show reduced microtubule dynamics with no major structural or functional centrosome defects, and in mutant bipolar neurons centrosomal positioning is correct. This negative finding is load-bearing for the entry: it is why TUBG1 disease is curated on the migration module rather than the neural-progenitor centrosome/spindle module that TUBB/TUBB5 conforms to, despite gamma-tubulin being a centrosomal protein and despite the obvious prior expectation that a nucleation defect would present as a spindle disorder.
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. patient-derived skin fibroblast CL:0000057 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves patient-derived skin fibroblast, annotated with fibroblast (CL:0000057). CL:0000057 is a cell type from the Cell Ontology.
microtubule polymerization or depolymerization GO:0031109 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased microtubule polymerization or depolymerization (GO:0031109). GO:0031109 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Failure of Neuronal Locomotion Initiation Slowed microtubule dynamics leave newborn neurons unable to initiate the locomotion phase of radial migration.
Show evidence (1 reference)
PMID:31086189 SUPPORT In Vitro
"We further demonstrate that pathogenic TUBG1 variants are linked to reduced microtubule dynamics but without major structural nor functional centrosome defects in subject-derived fibroblasts."
Establishes both halves of this node - reduced microtubule dynamics, and the absence of a centrosome structural or functional defect - in patient cells.
Failure of Neuronal Locomotion Initiation
The rate-limiting step. TUBG1 mutants disrupt the locomotion of newborn neurons and thereby their final positioning, while leaving progenitor proliferation unaffected - so the neurons are made, and then fail to travel. The defect is specifically in initiating locomotion: in the knock-in mouse, bipolar neurons position their centrosome correctly and still do not start moving, which separates this from a centrosome-repositioning failure. This is the node that makes TUBG1 a member of the migration module rather than of the progenitor-output modules.
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
Tubg1 Y92C/+ knock-in mouse Mouse recapitulates Directly demonstrates the failure of locomotion initiation with correct centrosomal positioning, which is what distinguishes this node from a centrosome-repositioning defect.
Downstream
Posterior-Predominant Pachygyria with Spared Deep Structures Neurons that fail to complete radial migration leave an abnormally thick, under-gyrated cortex with a posterior-to-anterior severity gradient.
Posterior-Predominant Subcortical Band Heterotopia Incomplete radial migration can leave ectopic cortical neurons as a posteriorly predominant subcortical band; the clinical occurrence is established, while the case-specific route is inferred from the shared migration mechanism.
Show evidence (3 references)
PMID:31086189 SUPPORT Model Organism
"We show that TUBG1 mutants affect neuronal positioning, disrupting the locomotion of new-born neurons but without affecting progenitors' proliferation."
The central mechanistic claim of this node: locomotion of postmitotic neurons fails while progenitor proliferation is spared.
PMID:31086189 SUPPORT Model Organism
"Although centrosomal positioning in bipolar neurons is correct, they fail to initiate locomotion."
Localizes the defect to initiation of locomotion rather than to centrosome repositioning, the finer claim this node makes.
PMID:23603762 SUPPORT Model Organism
"we show that suppression of mouse Tubg1 expression in vivo interferes with proper neuronal migration"
Independent in vivo evidence that reducing Tubg1 function impairs neuronal migration.
Posterior-Predominant Pachygyria with Spared Deep Structures
The tissue-level readout, and the entry's diagnostic signature. Failed locomotion produces a pachygyric cortex with a posterior-to-anterior gradient, lateral ventricles enlarged most over the posterior horns, and variably reduced white matter volume. What is absent matters as much as what is present: basal ganglia, brainstem and cerebellum are often normal, in contrast to the alpha- and beta-tubulinopathies where those structures are frequently malformed. Corpus-callosum morphology is variable rather than invariantly spared: it was often normal in the dedicated series but was thick and dysmorphic in P478. The resulting pattern resembles LIS1/PAFAH1B1 lissencephaly more than it resembles the rest of this gene family, which is why a tubulinopathy can be missed on imaging if dysmorphic basal ganglia are treated as a required feature.
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
Animal models
Tubg1 Y92C/+ knock-in mouse Mouse partially recapitulates Reproduces neuroanatomical and behavioral defects with increased epileptic cortical activity, matching the human epilepsy phenotype.
Downstream
Pachygyria The cortical malformation itself.
Microcephaly Reduced brain size accompanies the cortical malformation in most reported patients.
Ventriculomegaly Lateral ventricles are enlarged, most markedly over the posterior horns.
Reduced Cerebral White Matter Volume White matter volume is variably reduced alongside the cortical malformation.
Severe Intellectual Disability The malformation underlies severe cognitive impairment in most reported individuals.
Motor Delay The cortical malformation also produces delayed and variably impaired motor development.
Early-Life Seizures The dysplastic cortex is epileptogenic, with seizures usually beginning in early life.
Show evidence (4 references)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient, enlarged lateral ventricles most pronounced over the posterior horns, and variable degrees of reduced white matter volume."
Defines the positive imaging triad of TUBG1-related tubulinopathy.
PMID:29706637 SUPPORT Human Clinical
"Basal ganglia, corpus callosum, brainstem, and cerebellum were often normal, in contrast to patients with variants in other tubulin genes where these structures are frequently malformed."
The discriminating negative finding that separates TUBG1 from the rest of the grouping on imaging.
PMID:24860126 SUPPORT Human Clinical
"The core phenotype of TUBA1A and TUBG1 tubulinopathies are lissencephalies and microlissencephalies"
Places TUBG1 with TUBA1A at the lissencephaly end of the tubulinopathy malformation spectrum.
+ 1 more reference
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for TUBG1-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.
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Phenotypes

9
Head and Neck 1
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 (2 references)
PMID:29706637 SUPPORT Human Clinical
"Variants in TUBG1 have been described in three patients with posterior predominant pachygyria and microcephaly."
Microcephaly is part of the originally described TUBG1 phenotype.
PMID:38919239 SUPPORT Human Clinical
"This patient presented similarly to previous cases with features including microcephaly, epilepsy, and speech and motor delay."
Independent case confirming microcephaly as part of the typical presentation.
Nervous System 4
Ventriculomegaly HP:0002119 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ventriculomegaly (HP:0002119). HP:0002119 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29706637 SUPPORT Human Clinical
"enlarged lateral ventricles most pronounced over the posterior horns"
Documents the ventricular enlargement and its posterior predominance.
Severe Intellectual Disability HP:0010864 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Severe intellectual disability (HP:0010864). HP:0010864 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:29706637 SUPPORT Human Clinical
"All had severe motor and cognitive impairment and all except one developed seizures in early life."
The cognitive half of this cohort finding supports severe intellectual disability; motor impairment is modeled separately as Motor Delay.
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 supplies general tubulinopathy clinical context for the cognitive-severity spectrum; the TUBG1-specific cohort provides the gene-level support above.
Motor Delay HP:0001270 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Motor delay (HP:0001270). HP:0001270 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:29706637 SUPPORT Human Clinical
"All had severe motor and cognitive impairment and all except one developed seizures in early life."
The motor half of the dedicated-cohort finding supports this separately modeled phenotype.
PMID:38919239 SUPPORT Human Clinical
"This patient presented similarly to previous cases with features including microcephaly, epilepsy, and speech and motor delay."
Documents speech and motor delay as part of the recurrent phenotype.
Early-Life Seizures 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 (2 references)
PMID:29706637 SUPPORT Human Clinical
"All had severe motor and cognitive impairment and all except one developed seizures in early life."
Reports early-life seizure onset in seven of eight patients.
PMID:31086189 SUPPORT Human Clinical
"De novo heterozygous missense variants in the γ-tubulin gene TUBG1 have been linked to human malformations of cortical development associated with intellectual disability and epilepsy."
Confirms epilepsy as a defining feature of the TUBG1 phenotype.
Other 4
Pachygyria HP:0001302 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pachygyria (HP:0001302). HP:0001302 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient"
Reports pachygyria with a posterior-to-anterior gradient as the core cortical finding.
Posterior-Predominant Subcortical Band Heterotopia HP:0032411 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Posterior predominant subcortical band heterotopia (HP:0032411). HP:0032411 is a phenotype from the Human Phenotype Ontology.
GeneReviews reports this finding in 1 of 3 persons. Although that founding count is arithmetically one third, no disease-wide frequency band is asserted from three ascertained reported persons.
Show evidence (2 references)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"TUBG1 AD 2/3 persons Predominantly posterior subcortical band heterotopia (1/3 persons)"
GeneReviews explicitly identifies posterior-predominant subcortical band heterotopia in one of three reported TUBG1 persons; this founding count establishes spectrum inclusion, not population frequency.
PMID:23603762 SUPPORT Human Clinical
"The third but less severe case (P478: c.991A>C, p.T331P) showed posterior pachygyria and laminar heterotopia with a thick and dysmorphic corpus callosum (Fig. 4b and Supplementary Table 4)."
The primary report establishes laminar heterotopia in P478; GeneReviews supplies the exact posterior-predominant subcortical-band classification.
Reduced Cerebral White Matter Volume Cerebral white matter hypoplasia HP:0012430 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebral white matter hypoplasia (HP:0012430). HP:0012430 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29706637 SUPPORT Human Clinical
"variable degrees of reduced white matter volume"
Reports reduced white matter volume as a variable component of the imaging phenotype.
Trigonocephaly HP:0000243 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Trigonocephaly (HP:0000243). HP:0000243 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38919239 SUPPORT Human Clinical
"Unique characteristics were also present such as trigonocephaly, tethered frenulum, scoliosis, nystagmus, and a concurrent FBXW7 mutation."
Single-case phenotype expansion, explicitly reported with a concurrent FBXW7 variant, which is why the evidence is recorded as PARTIAL.
🧬

Genetic Associations

1
TUBG1 (Causative)
Gene: TUBG1 (gamma-tubulin 1) hgnc:12417 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TUBG1 (gamma-tubulin 1), annotated with TUBG1 (hgnc:12417). hgnc:12417 is a gene from the HUGO Gene Nomenclature Committee. variant_origin: DE_NOVO
Show evidence (2 references)
PMID:23603762 SUPPORT Human Clinical
"Here we report the discovery of multiple pathogenic missense mutations in TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in KIF5C, in subjects with MCD."
Founding evidence that TUBG1 missense mutations cause malformations of cortical development.
PMID:40298439 SUPPORT Other
"TUBG1 encodes a critical component of the γ-TuRC."
States the gene product's role in the gamma-tubulin ring complex.
💊

Medical Actions

3
Anti-Seizure Medication
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Seizure treatment is symptomatic and selected according to seizure type. Individual TUBG1 cases may require multiple anti-seizure medicines; the available literature does not establish comparative efficacy or a disease-modifying therapy.
Show evidence (3 references)
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."
GeneReviews directly recommends seizure-type-directed anti-seizure medication for tubulinopathies.
PMID:38912084 SUPPORT Human Clinical
"The child was treated with multiple anti-seizure medicines (ASMs)."
Directly documents multi-drug anti-seizure management in a TUBG1 case without supporting comparative efficacy.
PMID:38912084 SUPPORT Human Clinical
"Currently, only symptomatic treatment is available for this condition."
Supports the explicitly symptomatic scope of current treatment.
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. NCIT:C15747
Individualized multidisciplinary support can include physical, occupational, speech, and vision therapies according to the person's needs. Evidence supports use and care burden, not a TUBG1-specific comparative-efficacy estimate.
Show evidence (3 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 directly supports early individualized multidisciplinary rehabilitation.
PMID:38912084 SUPPORT Human Clinical
"The child is undergoing physiotherapy and occupational therapy."
Documents physical and occupational therapy in a TUBG1 case without making an efficacy claim.
PMID:42177523 SUPPORT Human Clinical
"A median of eight different supportive therapies was used per patient (range 1-17), with physiotherapy and respiratory therapy considered the most effective."
Provides mixed-lissencephaly-cohort context on supportive-care use and family perceptions; only one cohort member had TUBG1-related disease.
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
Most tubulinopathy-causing variants, including TUBG1 variants, arise de novo. Parental testing is recommended to establish genetic status and inform recurrence counseling; negative parental testing does not eliminate germline mosaicism. Once the familial pathogenic variant is known, prenatal and preimplantation genetic testing are possible.
Show evidence (4 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."
GeneReviews supports counseling that the great majority of cases arise de novo without making a TUBG1-only percentage claim.
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"If the proband appears to be the only affected family member (i.e., a simplex case), molecular genetic testing is recommended for the parents of the proband to confirm their genetic status and to allow reliable recurrence risk counseling."
Directly supports parental testing and its recurrence-counseling purpose.
PMID:38912084 SUPPORT Human Clinical
"If both parents' genetic tests are negative, germline mosaicism cannot be ruled out."
Supports the residual recurrence concern after negative parental blood testing.
+ 1 more reference
🔬

Diagnosis

2
Brain magnetic resonance imaging
MRI establishes the malformation pattern and, unusually for this grouping, recognition depends partly on absent findings. The expected pattern is posterior-predominant pachygyria with posteriorly accentuated ventriculomegaly and reduced white matter, together with often-normal basal ganglia, brainstem and cerebellum. Corpus-callosum morphology is variable: it was often normal in a dedicated series but was thick and dysmorphic in P478. Because dysmorphic basal ganglia are treated as a near-signature of tubulinopathy on imaging, their absence can push a TUBG1 patient toward a LIS1/PAFAH1B1 working diagnosis instead.
magnetic resonance imaging NCIT:C16809 NCI Thesaurus (NCIT)
Show evidence (4 references)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient, enlarged lateral ventricles most pronounced over the posterior horns, and variable degrees of reduced white matter volume."
Defines the three-part MRI pattern used to recognize TUBG1-related disease.
PMID:41070651 SUPPORT Human Clinical
"Head MRI revealed ventricular system dilatation and pachygyria."
Provides direct MRI findings from a molecularly diagnosed child.
PMID:29706637 SUPPORT Human Clinical
"The imaging phenotype associated with variants in TUBG1 is therefore more in line with the phenotype resulting from variants in LIS1 (a.k.a. PAFAH1B1)."
States the imaging differential explicitly: TUBG1 resembles LIS1 rather than the other tubulinopathies.
+ 1 more reference
Molecular genetic testing
Diagnosis is confirmed by identifying a heterozygous pathogenic TUBG1 variant using a cortical-malformation multigene panel or exome/genome sequencing. Trio-based exome sequencing can establish de novo origin when parental samples are available. Because the imaging phenotype can resemble LIS1/PAFAH1B1 disease, molecular testing resolves the gene-level diagnosis.
genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (3 references)
PMID:29706637 SUPPORT Human Clinical
"We here report eight additional patients with four novel heterozygous variants in TUBG1 identified by next-generation sequencing (NGS) analysis."
Next-generation sequencing is the modality by which the reported patient series was ascertained.
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 supports both panel-based and comprehensive genomic testing.
PMID:41070651 SUPPORT Human Clinical
"Trio-based whole-exome sequencing (WES) was performed, and candidate variants were validated by Sanger sequencing."
Directly supports trio WES with confirmatory Sanger sequencing in a TUBG1 case.
🩻

Imaging Findings

4
Posterior-Predominant Pachygyria
MRI typically shows pachygyria with a posterior-to-anterior severity gradient. This is one component of the characteristic TUBG1 imaging triad, not a gene-specific diagnosis in isolation.
Mri
Pachygyria HP:0001302 Human Phenotype Ontology (HP)
Show evidence (2 references)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient, enlarged lateral ventricles most pronounced over the posterior horns, and variable degrees of reduced white matter volume."
Defines pachygyria and its posterior predominance as part of the core MRI pattern.
PMID:41070651 SUPPORT Human Clinical
"Head MRI revealed ventricular system dilatation and pachygyria."
Independently documents pachygyria on MRI in a molecularly diagnosed child.
Posterior-Predominant Subcortical Band Heterotopia
MRI can show a posteriorly predominant subcortical band of heterotopic gray matter as a variable, milder-end feature. In P478 it accompanied posterior pachygyria and a thick, dysmorphic corpus callosum rather than the typical deep-structure-sparing pattern.
Mri
Posterior predominant subcortical band heterotopia HP:0032411 Human Phenotype Ontology (HP)
GeneReviews reports one affected person among three; no disease-wide frequency band is inferred from that denominator.
Show evidence (2 references)
url:https://www.ncbi.nlm.nih.gov/books/NBK350554/pdf/Bookshelf_NBK350554.pdf SUPPORT Other
"TUBG1 AD 2/3 persons Predominantly posterior subcortical band heterotopia (1/3 persons)"
GeneReviews explicitly identifies posterior-predominant subcortical band heterotopia in one of three reported TUBG1 persons; this founding count establishes spectrum inclusion, not population frequency.
PMID:23603762 SUPPORT Human Clinical
"The third but less severe case (P478: c.991A>C, p.T331P) showed posterior pachygyria and laminar heterotopia with a thick and dysmorphic corpus callosum (Fig. 4b and Supplementary Table 4)."
The primary report establishes laminar heterotopia in P478; GeneReviews supplies the exact posterior-predominant subcortical-band classification.
Ventriculomegaly
Lateral ventricular enlargement is usually most pronounced over the posterior horns and accompanies the posterior-predominant cortical malformation.
Mri
Ventriculomegaly HP:0002119 Human Phenotype Ontology (HP)
Show evidence (2 references)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient, enlarged lateral ventricles most pronounced over the posterior horns, and variable degrees of reduced white matter volume."
Identifies posteriorly accentuated ventricular enlargement within the core MRI pattern.
PMID:41070651 SUPPORT Human Clinical
"Head MRI revealed ventricular system dilatation and pachygyria."
Independently documents ventricular dilatation in a molecularly diagnosed child.
Reduced Cerebral White Matter Volume
Cerebral white matter volume is reduced to a variable degree as the third component of the characteristic MRI pattern.
Mri
Cerebral white matter hypoplasia HP:0012430 Human Phenotype Ontology (HP)
Show evidence (1 reference)
PMID:29706637 SUPPORT Human Clinical
"The core imaging features included a pachygyric cortex with posterior to anterior gradient, enlarged lateral ventricles most pronounced over the posterior horns, and variable degrees of reduced white matter volume."
Establishes variably reduced cerebral white matter volume within the core MRI pattern.
📈

Progression

3
Prenatal origin and possible tubulinopathy detection
Age: Prenatal period
The cortical malformation arises during prenatal neuronal migration. General tubulinopathy literature indicates that prenatal neurosonography may raise suspicion during second- or early third-trimester anomaly scanning; the cited review does not establish a TUBG1-specific prenatal case.
Show evidence (1 reference)
PMID:41901019 SUPPORT Other
"While historically diagnosed postnatally, advances in prenatal neurosonography now allow for the suspicion of this pathology in utero during routine second and early third-trimester anomaly scans."
Supports prenatal suspicion of tubulinopathy generally, not a direct TUBG1-specific prenatal observation.
Early-life seizure onset and severe developmental impairment
Age: Infancy to early childhood
Seizures begin in early life in nearly all reported individuals, and severe motor and cognitive impairment is apparent from infancy.
Show evidence (1 reference)
PMID:29706637 SUPPORT Human Clinical
"All had severe motor and cognitive impairment and all except one developed seizures in early life."
Documents the early-life onset of both the seizure and the developmental phenotype.
Milder alternative course
Age: Childhood to adulthood
A distinct milder trajectory exists and should not be treated as an outlier to be explained away: one reported individual has autism spectrum disorder, intellectual disability, later-onset well-controlled epilepsy, a normocephalic head size and no detectable structural abnormality on neuroimaging. A normal MRI therefore does not exclude a pathogenic TUBG1 variant.
Show evidence (1 reference)
PMID:40298439 SUPPORT Human Clinical
"The other individual has a likely pathogenic TUBG1 variant that explains the milder presentation of autism spectrum disorder, intellectual disability, later-onset well-controlled epilepsy, a normocephalic head size, and no detectable structural abnormalities on neuroimaging."
Documents a mild end of the TUBG1 spectrum including a normal MRI, which materially changes the differential.
🌍

Epidemiology

1
Rarity relative to other tubulinopathy genes
TUBG1 is among the rarest members of the tubulinopathy grouping. Published case counts are in the tens rather than the hundreds: three patients in the initial reports and eight more in the first dedicated series. It contributes a single patient to a 47-patient genetically confirmed lissencephaly cohort and is among seven causal genes identified in a contemporary multicenter tubulinopathy cohort. No population prevalence estimate exists for this gene specifically.
Show evidence (3 references)
PMID:29706637 SUPPORT Human Clinical
"Variants in TUBG1 have been described in three patients with posterior predominant pachygyria and microcephaly."
Establishes how small the reported TUBG1 case base was before this series.
PMID:42177523 SUPPORT Human Clinical
"47 patients with genetically and radiologically confirmed lissencephaly were included with mutation in LIS1/PAFAH1B1 (n = 38), DCX (n = 5 males), DYNC1H1 (n = 2), TUBA1A (n = 1) and TUBG1 (n = 1) genes."
Quantifies the TUBG1 share of a contemporary genetically confirmed lissencephaly cohort - one patient in 47.
PMID:42472988 SUPPORT Human Clinical
"Genetic analysis identified 12 distinct pathogenic variants across seven genes (TUBA1A, TUBB2A, TUBB2B, TUBB3, TUBB4A, TUBG1, TUBGCP2), including four novel variants."
Places TUBG1 among the genes recovered in a contemporary multicenter tubulinopathy cohort, confirming it remains a recognized but uncommon cause.
⚖️

Clinical Burden

High
High for the typical presentation: severe motor and cognitive impairment with early-life, often difficult-to-control seizures, in a non-progressive but lifelong and care-dependent condition. A mixed genetically confirmed lissencephaly cohort that included one TUBG1 participant reported low family-level quality of life and substantial supportive-care use; those cohort summaries provide context but are not TUBG1-specific estimates. The burden_level applies to the typical presentation; the reported mild end of the spectrum is materially less impaired.
Show evidence (2 references)
PMID:29706637 SUPPORT Human Clinical
"All had severe motor and cognitive impairment and all except one developed seizures in early life."
Establishes the severity of the typical presentation.
PMID:42177523 SUPPORT Human Clinical
"The scores obtained for health-related quality of life (HRQL) were low (parental HRQL mean 61.23; SD 16.79)."
Provides mixed-cohort context from a study containing only one TUBG1 participant, so it does not support a gene-specific quality-of-life estimate.
🐁

Animal Models

2
Tubg1 Y92C/+ knock-in mouse
A knock-in model of a patient variant, and the source of the entry's finest mechanistic claim - that mutant bipolar neurons position their centrosome correctly and still fail to initiate locomotion. The animals show neuroanatomical and behavioral defects and increased epileptic cortical activity, matching the human epilepsy phenotype.
Species
Mouse
Genotype
Tubg1 p.Y92C heterozygous knock-in
Publication
PMID:31086189
Pathograph links
Failure of Neuronal Locomotion Initiation recapitulates fidelity: high Directly demonstrates the failure of locomotion initiation with correct centrosomal positioning, which is what distinguishes this node from a centrosome-repositioning defect.
Limitations: The authors state the model only partially mimics the human phenotype. The mouse brain is naturally lissencephalic, so the defining human readout - posterior-predominant pachygyria with a gyral gradient - has no murine equivalent.
Readouts
Locomotion initiation in bipolar neurons
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
Direction: ABOLISHED
Interpretation: Neurons that are correctly polarized and correctly positioned nonetheless do not begin to move.
Show evidence (1 reference)
PMID:31086189 SUPPORT Model Organism
"Although centrosomal positioning in bipolar neurons is correct, they fail to initiate locomotion."
Reports the measurement behind this readout.
Show evidence (1 reference)
PMID:31086189 SUPPORT Model Organism
"We show that Tubg1Y92C/+ mice partially mimic the human phenotype and therefore represent a relevant model for further investigations of the physiopathology of cortical malformations."
The authors' own assessment of the model's fidelity - relevant but partial - which is recorded here rather than overstated.
Posterior-Predominant Pachygyria with Spared Deep Structures partially recapitulates fidelity: moderate Reproduces neuroanatomical and behavioral defects with increased epileptic cortical activity, matching the human epilepsy phenotype.
Limitations: Cannot reproduce the gyral phenotype in a lissencephalic species, so the posterior-to-anterior gradient that defines the human imaging signature is untestable in this model.
Readouts
Cortical epileptic activity
Direction: INCREASED
Interpretation: Electrophysiological correlate of the epileptogenic dysplastic cortex.
Show evidence (1 reference)
PMID:31086189 SUPPORT Model Organism
"Furthermore, Tubg1Y92C/+ animals show neuroanatomical and behavioral defects and increased epileptic cortical activity."
Reports the measurement behind this readout.
Show evidence (1 reference)
PMID:31086189 SUPPORT Model Organism
"Furthermore, Tubg1Y92C/+ animals show neuroanatomical and behavioral defects and increased epileptic cortical activity."
Supports the model as informative for the tissue-level and functional consequences, without the gyral phenotype.
tubg1 somatic mutant zebrafish
A somatic zebrafish model reported to recapitulate features of TUBG1 tubulinopathy seen in patients and mouse models. It contributes a microcephaly/neurogenesis phenotype and a proposed regulatory link between gamma-tubulin and canonical Wnt/beta-catenin signaling. Its neurogenesis finding sits in tension with the mouse result that progenitor proliferation is unaffected - see the gap_tubg1_neurogenesis_versus_locomotion discussion.
Species
Zebrafish
Genotype
tubg1 somatic (F0 crispant) mutation
Publication
PMID:39215931
Pathograph links
Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation perturbs fidelity: low Somatic disruption of tubg1 perturbs the nucleator and produces neurodevelopmental phenotypes reported as recapitulating patient and mouse features.
Limitations: A somatic loss-of-function crispant, whereas human disease alleles are heterozygous missense - a deficiency model and a missense model need not converge. Mosaic somatic targeting also gives variable per-animal gene disruption, and the Wnt link is described by the authors themselves as a novel potential regulatory link rather than an established mechanism.
Readouts
Neurogenesis and brain size
Direction: DECREASED
Interpretation: Gamma-tubulin deficiency reduces neurogenesis and brain size in this model.
Show evidence (1 reference)
PMID:39215931 SUPPORT Model Organism
"We demonstrate that γ-tubulin deficiency disrupts neurogenesis and brain development, mirroring microcephaly phenotypes."
Reports the measurement behind this readout.
Canonical Wnt/beta-catenin activity
Direction: DECREASED
Interpretation: A proposed, not established, regulatory link between gamma-tubulin and Wnt signaling.
Show evidence (1 reference)
PMID:39215931 SUPPORT Model Organism
"Furthermore, we uncover a novel potential regulatory link between γ-tubulin and canonical Wnt/β-catenin signaling, with γ-tubulin deficiency impairing Wnt activity."
The authors' own hedging - a novel potential regulatory link - is why this readout is recorded as PARTIAL.
Show evidence (1 reference)
PMID:39215931 SUPPORT Model Organism
"We investigate its role in brain development using a zebrafish model with somatic tubg1 mutation, recapitulating features of TUBG1-associated tubulinopathies in patients and mouse disease models."
The authors' claim that the model recapitulates patient and mouse features, recorded as PARTIAL given the somatic loss-of-function design.
{ }

Source YAML

click to show 
name: TUBG1-related Tubulinopathy
creation_date: "2026-08-20T09:00:00Z"
category: Mendelian
disease_term:
  preferred_term: complex cortical dysplasia with other brain malformations 4
  term:
    id: MONDO:0014171
    label: complex cortical dysplasia with other brain malformations 4
description: >-
  TUBG1-related tubulinopathy (CDCBM4) is a malformation of cortical development
  caused by heterozygous, typically de novo missense variants in TUBG1, which
  encodes gamma-tubulin 1. It is the gamma-tubulin member of the tubulinopathy
  grouping, and the distinction from its alpha- and beta-tubulin siblings is
  mechanistic rather than nominal. Alpha- and beta-tubulin form the heterodimer
  that polymerizes into the microtubule lattice, so a variant in either is
  incorporated into the polymer itself. Gamma-tubulin is not a lattice subunit at
  all: it is the core component of the gamma-tubulin ring complex (gamma-TuRC),
  the template that nucleates microtubules from the centrosome. The consequence
  of losing nucleation fidelity differs from the consequence of poisoning the
  polymer, and it shows in the imaging phenotype.

  The core radiological picture is a pachygyric cortex with a
  posterior-to-anterior gradient, lateral ventricles enlarged most over the
  posterior horns, and variably reduced white matter volume - with basal
  ganglia, brainstem and cerebellum often normal. Corpus-callosum morphology is
  variable: it was often normal in a dedicated series but was thick and
  dysmorphic in the less severe P478 case. The relative sparing of the basal
  ganglia is the strongest diagnostic discriminator because their dysmorphism
  is a near-signature finding in the alpha- and beta-tubulinopathies. This
  makes TUBG1 disease resemble LIS1/PAFAH1B1 lissencephaly more closely than it
  resembles its own gene family. Clinically, most reported individuals have
  severe motor and cognitive impairment with early-life seizures, though a mild
  end exists - one reported individual has autism, intellectual disability,
  later-onset well-controlled epilepsy, a normocephalic head and no detectable
  structural abnormality on neuroimaging.

  Functionally, the best-resolved lesion is a failure of post-mitotic neuronal
  locomotion rather than of progenitor proliferation: pathogenic variants reduce
  microtubule dynamics without producing major structural or functional
  centrosome defects, and mutant bipolar neurons position their centrosome
  correctly yet fail to initiate locomotion. A zebrafish somatic model
  additionally reports disrupted neurogenesis and a link to canonical
  Wnt/beta-catenin signaling; the tension between that and the mouse finding of
  intact proliferation is curated as an open discussion rather than smoothed
  over.
parents:
- congenital nervous system disorder
- disorder of development or morphogenesis
- hereditary neurological disease
- neuronal migration disorder
references:
- reference: PMID:23603762
  title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
- reference: PMID:31086189
  title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
- reference: PMID:29706637
  title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
- reference: PMID:39215931
  title: "tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model."
- reference: PMID:40298439
  title: Two New Cases Expand the Phenotypic Spectrum of TUBG1 Missense Variants.
- reference: PMID:38919239
  title: "Craniosynostosis Associated With Novel TUBG1 Mutation (NM_001070.4:c.821C>T) (p.Thr274Ile)."
- reference: PMID:24860126
  title: "The wide spectrum of tubulinopathies: what are the key features for the diagnosis?"
- reference: PMID:42177523
  title: "Gene-specific long-term course, neurodevelopmental outcome and quality of life in patients with LIS1/PAFAH1B1-, DCX-, DYNC1H1-, TUBA1A- and TUBG1-related lissencephaly."
- reference: PMID:42472988
  title: "Genotypic and phenotypic heterogeneity in tubulinopathies: insights from a Turkish multicenter cohort."
- reference: PMID:41901019
  title: The Role of Prenatal Neurosonography in Identification of Tubulinopathy-Narrative Review.
- 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
- reference: PMID:38912084
  title: "Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case."
- reference: PMID:41070651
  title: "[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant]."
inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Heterozygous, typically de novo missense variants. No biallelic or
    loss-of-function mechanism has been reported.
  evidence:
  - reference: PMID:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      De novo heterozygous missense variants in the γ-tubulin gene TUBG1 have
      been linked to human malformations of cortical development associated with
      intellectual disability and epilepsy.
    explanation: >-
      States the de novo heterozygous missense mechanism, supporting autosomal
      dominant, typically sporadic inheritance.
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We here report eight additional patients with four novel heterozygous
      variants in TUBG1 identified by next-generation sequencing (NGS) analysis.
    explanation: >-
      Confirms heterozygous variants across an independent eight-patient series.
  - 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: >-
      Tubulinopathies caused by pathogenic variants in TUBA1A, TUBB2A, TUBB2B,
      TUBB3, TUBB (TUBB5), or TUBG1 are inherited in an autosomal dominant manner.
    explanation: >-
      GeneReviews explicitly includes TUBG1 among the autosomal-dominant
      tubulinopathies.
  - 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 the typically de novo occurrence without implying that every
      TUBG1 case is de novo.
epidemiology:
- name: Rarity relative to other tubulinopathy genes
  description: >-
    TUBG1 is among the rarest members of the tubulinopathy grouping. Published
    case counts are in the tens rather than the hundreds: three patients in the
    initial reports and eight more in the first dedicated series. It contributes
    a single patient to a 47-patient genetically confirmed lissencephaly cohort
    and is among seven causal genes identified in a contemporary multicenter
    tubulinopathy cohort. No population prevalence estimate exists for this gene
    specifically.
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Variants in TUBG1 have been described in three patients with posterior
      predominant pachygyria and microcephaly.
    explanation: >-
      Establishes how small the reported TUBG1 case base was before this series.
  - reference: PMID:42177523
    reference_title: "Gene-specific long-term course, neurodevelopmental outcome and quality of life in patients with LIS1/PAFAH1B1-, DCX-, DYNC1H1-, TUBA1A- and TUBG1-related lissencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      47 patients with genetically and radiologically confirmed lissencephaly
      were included with mutation in LIS1/PAFAH1B1 (n = 38), DCX (n = 5 males),
      DYNC1H1 (n = 2), TUBA1A (n = 1) and TUBG1 (n = 1) genes.
    explanation: >-
      Quantifies the TUBG1 share of a contemporary genetically confirmed
      lissencephaly cohort - one patient in 47.
  - reference: PMID:42472988
    reference_title: "Genotypic and phenotypic heterogeneity in tubulinopathies: insights from a Turkish multicenter cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Genetic analysis identified 12 distinct pathogenic variants across seven
      genes (TUBA1A, TUBB2A, TUBB2B, TUBB3, TUBB4A, TUBG1, TUBGCP2), including
      four novel variants.
    explanation: >-
      Places TUBG1 among the genes recovered in a contemporary multicenter
      tubulinopathy cohort, confirming it remains a recognized but uncommon
      cause.
pathophysiology:
- name: Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
  role: TRIGGER
  biological_scale: MOLECULAR
  conforms_to: microtubule_dependent_neuronal_migration_failure#Microtubule Apparatus Perturbation
  description: >-
    Heterozygous missense variants alter gamma-tubulin 1, the core component of
    the gamma-tubulin ring complex (gamma-TuRC) that templates microtubule
    nucleation at the centrosome. This is a categorically different lesion from
    the one carried by the alpha- and beta-tubulinopathies: gamma-tubulin is not
    a subunit of the microtubule lattice, so the defect is in how microtubules
    are started rather than in what they are built from. Expression of altered
    gamma-tubulin proteins in yeast disrupts normal microtubule behavior, and in
    subject-derived fibroblasts pathogenic variants reduce microtubule dynamics.
    The module's trigger node is nevertheless the correct conformance target:
    whichever way the microtubule apparatus is perturbed, the same downstream
    migration machinery fails.
  genetic_context:
    functional_impact_category: UNKNOWN
    variant_origin: DE_NOVO
    zygosity: HETEROZYGOUS
    allele_type: missense
    description: >-
      All reported alleles are heterozygous missense, with no nonsense,
      frameshift or deletion alleles, so haploinsufficiency is not the presumed
      mechanism. The mechanism class has not been resolved further, and the one
      experiment that would have discriminated it argues against the obvious
      candidate: if the variants acted by disabling the centrosome as a
      nucleating center, subject fibroblasts should show centrosome defects, and
      they do not. UNKNOWN records that the question was examined and remains
      open, rather than that it was never annotated.
  genes:
  - preferred_term: TUBG1
    term:
      id: hgnc:12417
      label: TUBG1
  cell_types:
  - preferred_term: migrating cortical neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: microtubule nucleation
    term:
      id: GO:0007020
      label: microtubule nucleation
    modifier: DYSREGULATED
  - preferred_term: microtubule cytoskeleton organization
    term:
      id: GO:0000226
      label: microtubule cytoskeleton organization
    modifier: DYSREGULATED
  cellular_components:
  - preferred_term: gamma-tubulin ring complex
    term:
      id: GO:0000931
      label: gamma-tubulin ring complex
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we report the discovery of multiple pathogenic missense mutations in
      TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in
      KIF5C, in subjects with MCD.
    explanation: >-
      The founding report establishing pathogenic TUBG1 missense mutations as a
      cause of malformations of cortical development.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      expression of altered γ-tubulin proteins in Saccharomyces cerevisiae
      disrupts normal microtubule behavior
    explanation: >-
      Shows that the disease-associated gamma-tubulin proteins perturb
      microtubule behavior in a simplified heterologous system.
  - reference: PMID:40298439
    reference_title: Two New Cases Expand the Phenotypic Spectrum of TUBG1 Missense Variants.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The gamma-tubulin ring complex (γ-TuRC) plays a role in coordinating
      centrosome and spindle pole body formation during cell division. TUBG1
      encodes a critical component of the γ-TuRC.
    explanation: >-
      Identifies the gene product's role as a gamma-TuRC component, the basis
      for treating this as a nucleation lesion rather than a lattice-subunit
      lesion.
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      This difference may, at least in part, be explained by gamma-tubulin's
      physiological function in microtubule nucleation, which differs from that
      of alpha and beta-tubulin.
    explanation: >-
      Explicitly attributes the distinct TUBG1 imaging phenotype to the
      nucleation function of gamma-tubulin, the mechanistic claim this node
      makes.
  downstream:
  - target: Reduced Microtubule Dynamics without Centrosome Structural Defect
    description: >-
      Altered gamma-tubulin reduces microtubule dynamics in patient cells while
      leaving centrosome structure and function grossly intact.
- name: Reduced Microtubule Dynamics without Centrosome Structural Defect
  biological_scale: CELLULAR
  description: >-
    The cellular consequence is a quantitative slowing of microtubule dynamics,
    not a broken centrosome. Subject-derived fibroblasts carrying pathogenic
    TUBG1 variants show reduced microtubule dynamics with no major structural or
    functional centrosome defects, and in mutant bipolar neurons centrosomal
    positioning is correct. This negative finding is load-bearing for the entry:
    it is why TUBG1 disease is curated on the migration module rather than the
    neural-progenitor centrosome/spindle module that TUBB/TUBB5 conforms to,
    despite gamma-tubulin being a centrosomal protein and despite the obvious
    prior expectation that a nucleation defect would present as a spindle
    disorder.
  cell_types:
  - preferred_term: migrating cortical neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: patient-derived skin fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: microtubule polymerization or depolymerization
    term:
      id: GO:0031109
      label: microtubule polymerization or depolymerization
    modifier: DECREASED
  evidence:
  - reference: PMID:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We further demonstrate that pathogenic TUBG1 variants are linked to reduced
      microtubule dynamics but without major structural nor functional
      centrosome defects in subject-derived fibroblasts.
    explanation: >-
      Establishes both halves of this node - reduced microtubule dynamics, and
      the absence of a centrosome structural or functional defect - in patient
      cells.
  downstream:
  - target: Failure of Neuronal Locomotion Initiation
    description: >-
      Slowed microtubule dynamics leave newborn neurons unable to initiate the
      locomotion phase of radial migration.
- name: Failure of Neuronal Locomotion Initiation
  biological_scale: CELLULAR
  conforms_to: microtubule_dependent_neuronal_migration_failure#Microtubule-Based Neuronal Motility Failure
  description: >-
    The rate-limiting step. TUBG1 mutants disrupt the locomotion of newborn
    neurons and thereby their final positioning, while leaving progenitor
    proliferation unaffected - so the neurons are made, and then fail to travel.
    The defect is specifically in initiating locomotion: in the knock-in mouse,
    bipolar neurons position their centrosome correctly and still do not start
    moving, which separates this from a centrosome-repositioning failure. This is
    the node that makes TUBG1 a member of the migration module rather than of the
    progenitor-output modules.
  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:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We show that TUBG1 mutants affect neuronal positioning, disrupting the
      locomotion of new-born neurons but without affecting progenitors'
      proliferation.
    explanation: >-
      The central mechanistic claim of this node: locomotion of postmitotic
      neurons fails while progenitor proliferation is spared.
  - reference: PMID:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Although centrosomal positioning in bipolar neurons is correct, they fail
      to initiate locomotion.
    explanation: >-
      Localizes the defect to initiation of locomotion rather than to centrosome
      repositioning, the finer claim this node makes.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we show that suppression of mouse Tubg1 expression in vivo interferes with
      proper neuronal migration
    explanation: >-
      Independent in vivo evidence that reducing Tubg1 function impairs neuronal
      migration.
  downstream:
  - target: Posterior-Predominant Pachygyria with Spared Deep Structures
    description: >-
      Neurons that fail to complete radial migration leave an abnormally thick,
      under-gyrated cortex with a posterior-to-anterior severity gradient.
  - target: Posterior-Predominant Subcortical Band Heterotopia
    description: >-
      Incomplete radial migration can leave ectopic cortical neurons as a
      posteriorly predominant subcortical band; the clinical occurrence is
      established, while the case-specific route is inferred from the shared
      migration mechanism.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - incomplete radial migration and ectopic subcortical neuronal positioning
- name: Posterior-Predominant Pachygyria with Spared Deep Structures
  biological_scale: TISSUE
  conforms_to: microtubule_dependent_neuronal_migration_failure#Cortical Dyslamination and Neuronal Ectopia
  description: >-
    The tissue-level readout, and the entry's diagnostic signature. Failed
    locomotion produces a pachygyric cortex with a posterior-to-anterior
    gradient, lateral ventricles enlarged most over the posterior horns, and
    variably reduced white matter volume. What is absent matters as much as what
    is present: basal ganglia, brainstem and cerebellum are often normal, in
    contrast to the alpha- and beta-tubulinopathies where those structures are
    frequently malformed. Corpus-callosum morphology is variable rather than
    invariantly spared: it was often normal in the dedicated series but was
    thick and dysmorphic in P478. The resulting pattern resembles
    LIS1/PAFAH1B1 lissencephaly more than it resembles the rest of this gene
    family, which is why a tubulinopathy can be missed on imaging if dysmorphic
    basal ganglia are treated as a required feature.
  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
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient, enlarged lateral ventricles most pronounced over the
      posterior horns, and variable degrees of reduced white matter volume.
    explanation: >-
      Defines the positive imaging triad of TUBG1-related tubulinopathy.
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Basal ganglia, corpus callosum, brainstem, and cerebellum were often
      normal, in contrast to patients with variants in other tubulin genes where
      these structures are frequently malformed.
    explanation: >-
      The discriminating negative finding that separates TUBG1 from the rest of
      the grouping on imaging.
  - 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: >-
      The core phenotype of TUBA1A and TUBG1 tubulinopathies are lissencephalies
      and microlissencephalies
    explanation: >-
      Places TUBG1 with TUBA1A at the lissencephaly end of the tubulinopathy
      malformation spectrum.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third but less severe case (P478: c.991A>C, p.T331P) showed posterior
      pachygyria and laminar heterotopia with a thick and dysmorphic corpus
      callosum (Fig. 4b and Supplementary Table 4).
    explanation: >-
      Shows that corpus-callosum morphology is variable rather than invariantly
      spared; the specific P478 finding does not negate the cohort-level
      observation that the corpus callosum was often normal.
  downstream:
  - target: Pachygyria
    description: The cortical malformation itself.
  - target: Microcephaly
    description: Reduced brain size accompanies the cortical malformation in most reported patients.
  - target: Ventriculomegaly
    description: Lateral ventricles are enlarged, most markedly over the posterior horns.
  - target: Reduced Cerebral White Matter Volume
    description: White matter volume is variably reduced alongside the cortical malformation.
  - target: Severe Intellectual Disability
    description: The malformation underlies severe cognitive impairment in most reported individuals.
  - target: Motor Delay
    description: The cortical malformation also produces delayed and variably impaired motor development.
  - target: Early-Life Seizures
    description: The dysplastic cortex is epileptogenic, with seizures usually beginning in early life.
phenotypes:
- name: Pachygyria
  description: >-
    A thick, under-gyrated cortex with a characteristic posterior-to-anterior
    severity gradient. This gradient is itself informative - it is the pattern
    reported across the dedicated TUBG1 series.
  phenotype_term:
    preferred_term: Pachygyria
    term:
      id: HP:0001302
      label: Pachygyria
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient
    explanation: >-
      Reports pachygyria with a posterior-to-anterior gradient as the core
      cortical finding.
- name: Posterior-Predominant Subcortical Band Heterotopia
  description: >-
    A posteriorly accentuated band of heterotopic gray matter beneath the cortex
    was documented in the less severe P478 case together with posterior
    pachygyria and a thick, dysmorphic corpus callosum.
  phenotype_term:
    preferred_term: Posterior predominant subcortical band heterotopia
    term:
      id: HP:0032411
      label: Posterior predominant subcortical band heterotopia
  notes: >-
    GeneReviews reports this finding in 1 of 3 persons. Although that founding
    count is arithmetically one third, no disease-wide frequency band is
    asserted from three ascertained reported persons.
  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: >-
      TUBG1 AD 2/3 persons Predominantly posterior subcortical
      band heterotopia (1/3 persons)
    explanation: >-
      GeneReviews explicitly identifies posterior-predominant subcortical band
      heterotopia in one of three reported TUBG1 persons; this founding count
      establishes spectrum inclusion, not population frequency.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third but less severe case (P478: c.991A>C, p.T331P) showed posterior
      pachygyria and laminar heterotopia with a thick and dysmorphic corpus
      callosum (Fig. 4b and Supplementary Table 4).
    explanation: >-
      The primary report establishes laminar heterotopia in P478; GeneReviews
      supplies the exact posterior-predominant subcortical-band classification.
- name: Microcephaly
  description: >-
    Microcephaly accompanies the cortical malformation in most reported
    individuals, and was present in the earliest described patients. It is not
    universal - the mild end of the spectrum includes a normocephalic individual.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Variants in TUBG1 have been described in three patients with posterior
      predominant pachygyria and microcephaly.
    explanation: >-
      Microcephaly is part of the originally described TUBG1 phenotype.
  - reference: PMID:38919239
    reference_title: "Craniosynostosis Associated With Novel TUBG1 Mutation (NM_001070.4:c.821C>T) (p.Thr274Ile)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This patient presented similarly to previous cases with features including
      microcephaly, epilepsy, and speech and motor delay.
    explanation: >-
      Independent case confirming microcephaly as part of the typical
      presentation.
- name: Ventriculomegaly
  description: >-
    Lateral ventricles are enlarged, most markedly over the posterior horns -
    matching the posterior predominance of the cortical malformation.
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      enlarged lateral ventricles most pronounced over the posterior horns
    explanation: >-
      Documents the ventricular enlargement and its posterior predominance.
- name: Reduced Cerebral White Matter Volume
  description: >-
    White matter volume is reduced to a variable degree, consistent with fewer
    neurons completing radial migration and establishing cortical connectivity.
  phenotype_term:
    preferred_term: Cerebral white matter hypoplasia
    term:
      id: HP:0012430
      label: Cerebral white matter hypoplasia
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      variable degrees of reduced white matter volume
    explanation: >-
      Reports reduced white matter volume as a variable component of the imaging
      phenotype.
- name: Severe Intellectual Disability
  description: >-
    Severe intellectual disability is typical in the dedicated TUBG1 series,
    though milder cognitive presentations occur across the broader spectrum.
  phenotype_term:
    preferred_term: Severe intellectual disability
    term:
      id: HP:0010864
      label: Severe intellectual disability
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All had severe motor and cognitive impairment and all except one developed
      seizures in early life.
    explanation: >-
      The cognitive half of this cohort finding supports severe intellectual
      disability; motor impairment is modeled separately as Motor Delay.
  - 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 supplies general tubulinopathy clinical context for the
      cognitive-severity spectrum; the TUBG1-specific cohort provides the
      gene-level support above.
- name: Motor Delay
  description: >-
    Motor and speech delay are consistently reported alongside the cognitive
    impairment.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All had severe motor and cognitive impairment and all except one developed
      seizures in early life.
    explanation: >-
      The motor half of the dedicated-cohort finding supports this separately
      modeled phenotype.
  - reference: PMID:38919239
    reference_title: "Craniosynostosis Associated With Novel TUBG1 Mutation (NM_001070.4:c.821C>T) (p.Thr274Ile)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This patient presented similarly to previous cases with features including
      microcephaly, epilepsy, and speech and motor delay.
    explanation: >-
      Documents speech and motor delay as part of the recurrent phenotype.
- name: Early-Life Seizures
  description: >-
    Seizures begin in early life in nearly all reported individuals. Severity
    varies with the rest of the phenotype: at the mild end, epilepsy is
    later-onset and well controlled.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All had severe motor and cognitive impairment and all except one developed
      seizures in early life.
    explanation: >-
      Reports early-life seizure onset in seven of eight patients.
  - reference: PMID:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      De novo heterozygous missense variants in the γ-tubulin gene TUBG1 have
      been linked to human malformations of cortical development associated with
      intellectual disability and epilepsy.
    explanation: >-
      Confirms epilepsy as a defining feature of the TUBG1 phenotype.
- name: Trigonocephaly
  description: >-
    Reported in a single individual alongside tethered frenulum, scoliosis and
    nystagmus. Curated as a documented phenotype expansion rather than a
    characteristic feature, and the same report notes a concurrent FBXW7
    variant, so attribution to TUBG1 alone is not established.
  phenotype_term:
    preferred_term: Trigonocephaly
    term:
      id: HP:0000243
      label: Trigonocephaly
  evidence:
  - reference: PMID:38919239
    reference_title: "Craniosynostosis Associated With Novel TUBG1 Mutation (NM_001070.4:c.821C>T) (p.Thr274Ile)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Unique characteristics were also present such as trigonocephaly, tethered
      frenulum, scoliosis, nystagmus, and a concurrent FBXW7 mutation.
    explanation: >-
      Single-case phenotype expansion, explicitly reported with a concurrent
      FBXW7 variant, which is why the evidence is recorded as PARTIAL.
imaging_findings:
- name: Posterior-Predominant Pachygyria
  modality: MRI
  description: >-
    MRI typically shows pachygyria with a posterior-to-anterior severity
    gradient. This is one component of the characteristic TUBG1 imaging triad,
    not a gene-specific diagnosis in isolation.
  imaging_finding_term:
    preferred_term: Pachygyria
    term:
      id: HP:0001302
      label: Pachygyria
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient, enlarged lateral ventricles most pronounced over the
      posterior horns, and variable degrees of reduced white matter volume.
    explanation: >-
      Defines pachygyria and its posterior predominance as part of the core MRI
      pattern.
  - reference: PMID:41070651
    reference_title: "[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Head MRI revealed ventricular system dilatation and pachygyria.
    explanation: >-
      Independently documents pachygyria on MRI in a molecularly diagnosed child.
- name: Posterior-Predominant Subcortical Band Heterotopia
  modality: MRI
  description: >-
    MRI can show a posteriorly predominant subcortical band of heterotopic gray
    matter as a variable, milder-end feature. In P478 it accompanied posterior
    pachygyria and a thick, dysmorphic corpus callosum rather than the typical
    deep-structure-sparing pattern.
  imaging_finding_term:
    preferred_term: Posterior predominant subcortical band heterotopia
    term:
      id: HP:0032411
      label: Posterior predominant subcortical band heterotopia
  notes: >-
    GeneReviews reports one affected person among three; no disease-wide
    frequency band is inferred from that denominator.
  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: >-
      TUBG1 AD 2/3 persons Predominantly posterior subcortical
      band heterotopia (1/3 persons)
    explanation: >-
      GeneReviews explicitly identifies posterior-predominant subcortical band
      heterotopia in one of three reported TUBG1 persons; this founding count
      establishes spectrum inclusion, not population frequency.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third but less severe case (P478: c.991A>C, p.T331P) showed posterior
      pachygyria and laminar heterotopia with a thick and dysmorphic corpus
      callosum (Fig. 4b and Supplementary Table 4).
    explanation: >-
      The primary report establishes laminar heterotopia in P478; GeneReviews
      supplies the exact posterior-predominant subcortical-band classification.
- name: Ventriculomegaly
  modality: MRI
  description: >-
    Lateral ventricular enlargement is usually most pronounced over the
    posterior horns and accompanies the posterior-predominant cortical
    malformation.
  imaging_finding_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient, enlarged lateral ventricles most pronounced over the
      posterior horns, and variable degrees of reduced white matter volume.
    explanation: >-
      Identifies posteriorly accentuated ventricular enlargement within the core
      MRI pattern.
  - reference: PMID:41070651
    reference_title: "[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Head MRI revealed ventricular system dilatation and pachygyria.
    explanation: >-
      Independently documents ventricular dilatation in a molecularly diagnosed
      child.
- name: Reduced Cerebral White Matter Volume
  modality: MRI
  description: >-
    Cerebral white matter volume is reduced to a variable degree as the third
    component of the characteristic MRI pattern.
  imaging_finding_term:
    preferred_term: Cerebral white matter hypoplasia
    term:
      id: HP:0012430
      label: Cerebral white matter hypoplasia
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient, enlarged lateral ventricles most pronounced over the
      posterior horns, and variable degrees of reduced white matter volume.
    explanation: >-
      Establishes variably reduced cerebral white matter volume within the core
      MRI pattern.
genetic:
- name: TUBG1
  association: Causative
  variant_origin: DE_NOVO
  gene_term:
    preferred_term: TUBG1 (gamma-tubulin 1)
    term:
      id: hgnc:12417
      label: TUBG1
  notes: >-
    TUBG1 encodes gamma-tubulin 1, a core component of the gamma-tubulin ring
    complex. It shares very high sequence identity with its paralog TUBG2 but the
    two are not functionally interchangeable, and TUBG1 is the more abundantly
    expressed of the pair in the developing brain.
  evidence:
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we report the discovery of multiple pathogenic missense mutations in
      TUBG1, DYNC1H1 and KIF2A, as well as a single germline mosaic mutation in
      KIF5C, in subjects with MCD.
    explanation: >-
      Founding evidence that TUBG1 missense mutations cause malformations of
      cortical development.
  - reference: PMID:40298439
    reference_title: Two New Cases Expand the Phenotypic Spectrum of TUBG1 Missense Variants.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      TUBG1 encodes a critical component of the γ-TuRC.
    explanation: >-
      States the gene product's role in the gamma-tubulin ring complex.
diagnosis:
- name: Brain magnetic resonance imaging
  description: >-
    MRI establishes the malformation pattern and, unusually for this grouping,
    recognition depends partly on absent findings. The expected pattern is
    posterior-predominant pachygyria with posteriorly accentuated
    ventriculomegaly and reduced white matter, together with often-normal basal
    ganglia, brainstem and cerebellum. Corpus-callosum morphology is variable:
    it was often normal in a dedicated series but was thick and dysmorphic in
    P478. Because dysmorphic basal ganglia are treated as a near-signature of
    tubulinopathy on imaging, their absence can push a TUBG1 patient toward a
    LIS1/PAFAH1B1 working diagnosis instead.
  diagnosis_term:
    preferred_term: magnetic resonance imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The core imaging features included a pachygyric cortex with posterior to
      anterior gradient, enlarged lateral ventricles most pronounced over the
      posterior horns, and variable degrees of reduced white matter volume.
    explanation: >-
      Defines the three-part MRI pattern used to recognize TUBG1-related disease.
  - reference: PMID:41070651
    reference_title: "[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Head MRI revealed ventricular system dilatation and pachygyria.
    explanation: >-
      Provides direct MRI findings from a molecularly diagnosed child.
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The imaging phenotype associated with variants in TUBG1 is therefore more
      in line with the phenotype resulting from variants in LIS1 (a.k.a.
      PAFAH1B1).
    explanation: >-
      States the imaging differential explicitly: TUBG1 resembles LIS1 rather
      than the other tubulinopathies.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third but less severe case (P478: c.991A>C, p.T331P) showed posterior
      pachygyria and laminar heterotopia with a thick and dysmorphic corpus
      callosum (Fig. 4b and Supplementary Table 4).
    explanation: >-
      Establishes that corpus-callosum morphology can be abnormal in a
      molecularly diagnosed TUBG1 case, qualifying the cohort-level observation
      that it was often normal.
- name: Molecular genetic testing
  description: >-
    Diagnosis is confirmed by identifying a heterozygous pathogenic TUBG1
    variant using a cortical-malformation multigene panel or exome/genome
    sequencing. Trio-based exome sequencing can establish de novo origin when
    parental samples are available. Because the imaging phenotype can resemble
    LIS1/PAFAH1B1 disease, molecular testing resolves the gene-level diagnosis.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We here report eight additional patients with four novel heterozygous
      variants in TUBG1 identified by next-generation sequencing (NGS) analysis.
    explanation: >-
      Next-generation sequencing is the modality by which the reported patient
      series was ascertained.
  - 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 supports both panel-based and comprehensive genomic testing.
  - reference: PMID:41070651
    reference_title: "[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Trio-based whole-exome sequencing (WES) was performed, and candidate
      variants were validated by Sanger sequencing.
    explanation: >-
      Directly supports trio WES with confirmatory Sanger sequencing in a TUBG1
      case.
progression:
- phase: Prenatal origin and possible tubulinopathy detection
  age_range: Prenatal period
  notes: >-
    The cortical malformation arises during prenatal neuronal migration. General
    tubulinopathy literature indicates that prenatal neurosonography may raise
    suspicion during second- or early third-trimester anomaly scanning; the cited
    review does not establish a TUBG1-specific prenatal case.
  evidence:
  - reference: PMID:41901019
    reference_title: The Role of Prenatal Neurosonography in Identification of Tubulinopathy-Narrative Review.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      While historically diagnosed postnatally, advances in prenatal
      neurosonography now allow for the suspicion of this pathology in utero
      during routine second and early third-trimester anomaly scans.
    explanation: >-
      Supports prenatal suspicion of tubulinopathy generally, not a direct
      TUBG1-specific prenatal observation.
- phase: Early-life seizure onset and severe developmental impairment
  age_range: Infancy to early childhood
  notes: >-
    Seizures begin in early life in nearly all reported individuals, and severe
    motor and cognitive impairment is apparent from infancy.
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All had severe motor and cognitive impairment and all except one developed
      seizures in early life.
    explanation: >-
      Documents the early-life onset of both the seizure and the developmental
      phenotype.
- phase: Milder alternative course
  age_range: Childhood to adulthood
  notes: >-
    A distinct milder trajectory exists and should not be treated as an outlier
    to be explained away: one reported individual has autism spectrum disorder,
    intellectual disability, later-onset well-controlled epilepsy, a
    normocephalic head size and no detectable structural abnormality on
    neuroimaging. A normal MRI therefore does not exclude a pathogenic TUBG1
    variant.
  evidence:
  - reference: PMID:40298439
    reference_title: Two New Cases Expand the Phenotypic Spectrum of TUBG1 Missense Variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The other individual has a likely pathogenic TUBG1 variant that explains
      the milder presentation of autism spectrum disorder, intellectual
      disability, later-onset well-controlled epilepsy, a normocephalic head
      size, and no detectable structural abnormalities on neuroimaging.
    explanation: >-
      Documents a mild end of the TUBG1 spectrum including a normal MRI, which
      materially changes the differential.
clinical_burden:
  burden_level: HIGH
  rationale: >-
    High for the typical presentation: severe motor and cognitive impairment with
    early-life, often difficult-to-control seizures, in a non-progressive but
    lifelong and care-dependent condition. A mixed genetically confirmed
    lissencephaly cohort that included one TUBG1 participant reported low
    family-level quality of life and substantial supportive-care use; those
    cohort summaries provide context but are not TUBG1-specific estimates. The
    burden_level applies to the typical presentation; the reported mild end of
    the spectrum is materially less impaired.
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All had severe motor and cognitive impairment and all except one developed
      seizures in early life.
    explanation: >-
      Establishes the severity of the typical presentation.
  - reference: PMID:42177523
    reference_title: "Gene-specific long-term course, neurodevelopmental outcome and quality of life in patients with LIS1/PAFAH1B1-, DCX-, DYNC1H1-, TUBA1A- and TUBG1-related lissencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The scores obtained for health-related quality of life (HRQL) were low
      (parental HRQL mean 61.23; SD 16.79).
    explanation: >-
      Provides mixed-cohort context from a study containing only one TUBG1
      participant, so it does not support a gene-specific quality-of-life estimate.
treatments:
- name: Anti-Seizure Medication
  description: >-
    Seizure treatment is symptomatic and selected according to seizure type.
    Individual TUBG1 cases may require multiple anti-seizure medicines; the
    available literature does not establish comparative efficacy or a
    disease-modifying therapy.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  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: >-
      Seizures are treated with anti-seizure medications based on the specific
      seizure type.
    explanation: >-
      GeneReviews directly recommends seizure-type-directed anti-seizure
      medication for tubulinopathies.
  - reference: PMID:38912084
    reference_title: "Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The child was treated with multiple anti-seizure medicines (ASMs).
    explanation: >-
      Directly documents multi-drug anti-seizure management in a TUBG1 case
      without supporting comparative efficacy.
  - reference: PMID:38912084
    reference_title: "Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Currently, only symptomatic treatment is available for this condition.
    explanation: >-
      Supports the explicitly symptomatic scope of current treatment.
- name: Supportive and Rehabilitative Care
  description: >-
    Individualized multidisciplinary support can include physical,
    occupational, speech, and vision therapies according to the person's needs.
    Evidence supports use and care burden, not a TUBG1-specific
    comparative-efficacy estimate.
  therapeutic_modality: BEHAVIORAL
  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 directly supports early individualized multidisciplinary
      rehabilitation.
  - reference: PMID:38912084
    reference_title: "Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The child is undergoing physiotherapy and occupational therapy.
    explanation: >-
      Documents physical and occupational therapy in a TUBG1 case without making
      an efficacy claim.
  - reference: PMID:42177523
    reference_title: "Gene-specific long-term course, neurodevelopmental outcome and quality of life in patients with LIS1/PAFAH1B1-, DCX-, DYNC1H1-, TUBA1A- and TUBG1-related lissencephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A median of eight different supportive therapies was used per patient
      (range 1-17), with physiotherapy and respiratory therapy considered the
      most effective.
    explanation: >-
      Provides mixed-lissencephaly-cohort context on supportive-care use and
      family perceptions; only one cohort member had TUBG1-related disease.
- name: Genetic Counseling
  description: >-
    Most tubulinopathy-causing variants, including TUBG1 variants, arise de novo.
    Parental testing is recommended to establish genetic status and inform
    recurrence counseling; negative parental testing does not eliminate germline
    mosaicism. Once the familial pathogenic variant is known, prenatal and
    preimplantation genetic testing are possible.
  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: >-
      GeneReviews supports counseling that the great majority of cases arise de
      novo without making a TUBG1-only percentage claim.
  - 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: >-
      If the proband appears to be the only affected family member (i.e., a
      simplex case), molecular genetic testing is recommended for the parents of
      the proband to confirm their genetic status and to allow reliable recurrence
      risk counseling.
    explanation: >-
      Directly supports parental testing and its recurrence-counseling purpose.
  - reference: PMID:38912084
    reference_title: "Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If both parents' genetic tests are negative, germline mosaicism cannot be
      ruled out.
    explanation: >-
      Supports the residual recurrence concern after negative parental blood
      testing.
  - 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: >-
      Once the tubulinopathy-related pathogenic variant has been identified in an
      affected family member, prenatal and preimplantation genetic testing are
      possible.
    explanation: >-
      Directly supports discussing prenatal and preimplantation testing after the
      familial variant is known.
animal_models:
- name: Tubg1 Y92C/+ knock-in mouse
  species: Mouse
  genotype: Tubg1 p.Y92C heterozygous knock-in
  publication: PMID:31086189
  description: >-
    A knock-in model of a patient variant, and the source of the entry's finest
    mechanistic claim - that mutant bipolar neurons position their centrosome
    correctly and still fail to initiate locomotion. The animals show
    neuroanatomical and behavioral defects and increased epileptic cortical
    activity, matching the human epilepsy phenotype.
  modeled_mechanisms:
  - target: Failure of Neuronal Locomotion Initiation
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Directly demonstrates the failure of locomotion initiation with correct
      centrosomal positioning, which is what distinguishes this node from a
      centrosome-repositioning defect.
    limitations: >-
      The authors state the model only partially mimics the human phenotype. The
      mouse brain is naturally lissencephalic, so the defining human readout -
      posterior-predominant pachygyria with a gyral gradient - has no murine
      equivalent.
    readouts:
    - name: Locomotion initiation in bipolar neurons
      target: Failure of Neuronal Locomotion Initiation
      direction: ABOLISHED
      interpretation: >-
        Neurons that are correctly polarized and correctly positioned
        nonetheless do not begin to move.
      biological_processes:
      - preferred_term: neuron migration
        term:
          id: GO:0001764
          label: neuron migration
        modifier: DECREASED
      evidence:
      - reference: PMID:31086189
        reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Although centrosomal positioning in bipolar neurons is correct, they
          fail to initiate locomotion.
        explanation: Reports the measurement behind this readout.
    evidence:
    - reference: PMID:31086189
      reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We show that Tubg1Y92C/+ mice partially mimic the human phenotype and
        therefore represent a relevant model for further investigations of the
        physiopathology of cortical malformations.
      explanation: >-
        The authors' own assessment of the model's fidelity - relevant but
        partial - which is recorded here rather than overstated.
  - target: Posterior-Predominant Pachygyria with Spared Deep Structures
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces neuroanatomical and behavioral defects with increased epileptic
      cortical activity, matching the human epilepsy phenotype.
    limitations: >-
      Cannot reproduce the gyral phenotype in a lissencephalic species, so the
      posterior-to-anterior gradient that defines the human imaging signature is
      untestable in this model.
    readouts:
    - name: Cortical epileptic activity
      target: Posterior-Predominant Pachygyria with Spared Deep Structures
      direction: INCREASED
      interpretation: >-
        Electrophysiological correlate of the epileptogenic dysplastic cortex.
      evidence:
      - reference: PMID:31086189
        reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Furthermore, Tubg1Y92C/+ animals show neuroanatomical and behavioral
          defects and increased epileptic cortical activity.
        explanation: Reports the measurement behind this readout.
    evidence:
    - reference: PMID:31086189
      reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Furthermore, Tubg1Y92C/+ animals show neuroanatomical and behavioral
        defects and increased epileptic cortical activity.
      explanation: >-
        Supports the model as informative for the tissue-level and functional
        consequences, without the gyral phenotype.
- name: tubg1 somatic mutant zebrafish
  species: Zebrafish
  genotype: tubg1 somatic (F0 crispant) mutation
  publication: PMID:39215931
  description: >-
    A somatic zebrafish model reported to recapitulate features of TUBG1
    tubulinopathy seen in patients and mouse models. It contributes a
    microcephaly/neurogenesis phenotype and a proposed regulatory link between
    gamma-tubulin and canonical Wnt/beta-catenin signaling. Its neurogenesis
    finding sits in tension with the mouse result that progenitor proliferation
    is unaffected - see the gap_tubg1_neurogenesis_versus_locomotion discussion.
  modeled_mechanisms:
  - target: Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
    relationship: PERTURBS
    fidelity: LOW
    description: >-
      Somatic disruption of tubg1 perturbs the nucleator and produces
      neurodevelopmental phenotypes reported as recapitulating patient and mouse
      features.
    limitations: >-
      A somatic loss-of-function crispant, whereas human disease alleles are
      heterozygous missense - a deficiency model and a missense model need not
      converge. Mosaic somatic targeting also gives variable per-animal gene
      disruption, and the Wnt link is described by the authors themselves as a
      novel potential regulatory link rather than an established mechanism.
    readouts:
    - name: Neurogenesis and brain size
      target: Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
      direction: DECREASED
      interpretation: >-
        Gamma-tubulin deficiency reduces neurogenesis and brain size in this
        model.
      evidence:
      - reference: PMID:39215931
        reference_title: "tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          We demonstrate that γ-tubulin deficiency disrupts neurogenesis and
          brain development, mirroring microcephaly phenotypes.
        explanation: Reports the measurement behind this readout.
    - name: Canonical Wnt/beta-catenin activity
      target: Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
      direction: DECREASED
      interpretation: >-
        A proposed, not established, regulatory link between gamma-tubulin and
        Wnt signaling.
      evidence:
      - reference: PMID:39215931
        reference_title: "tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Furthermore, we uncover a novel potential regulatory link between
          γ-tubulin and canonical Wnt/β-catenin signaling, with γ-tubulin
          deficiency impairing Wnt activity.
        explanation: >-
          The authors' own hedging - a novel potential regulatory link - is why
          this readout is recorded as PARTIAL.
    evidence:
    - reference: PMID:39215931
      reference_title: "tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We investigate its role in brain development using a zebrafish model
        with somatic tubg1 mutation, recapitulating features of
        TUBG1-associated tubulinopathies in patients and mouse disease models.
      explanation: >-
        The authors' claim that the model recapitulates patient and mouse
        features, recorded as PARTIAL given the somatic loss-of-function design.
discussions:
- discussion_id: gap_tubg1_neurogenesis_versus_locomotion
  prompt: >-
    Does pathogenic TUBG1 variation impair neurogenesis, or only the locomotion
    of neurons that were made normally?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Failure of Neuronal Locomotion Initiation
  - pathophysiology#Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
  rationale: >-
    Two model systems give opposite answers, and the disagreement is not cosmetic
    - it decides which module this disease belongs to. In mouse, in utero
    electroporation of four patient variants and a Tubg1 Y92C/+ knock-in show
    disrupted locomotion of newborn neurons without affecting progenitor
    proliferation; the paper's title states the point as "not neurogenesis". In
    zebrafish, somatic tubg1 mutation is reported to disrupt neurogenesis and
    brain development, mirroring microcephaly. The most likely reconciliation is
    the difference in allele class: the mouse work models heterozygous patient
    missense variants, while the zebrafish work is a somatic loss-of-function
    crispant, and gamma-tubulin is essential for mitosis, so removing it should
    impair proliferation even if a missense allele does not. If that is right,
    the zebrafish neurogenesis phenotype models gamma-tubulin deficiency rather
    than human TUBG1 disease. But it is not settled, and the human phenotype does
    include microcephaly, which a pure locomotion defect does not obviously
    explain. Resolving it requires a zebrafish or human model carrying the
    heterozygous missense allele rather than a null, with progenitor
    proliferation measured directly.
  proposed_experiments:
  - experiment_id: exp_tubg1_missense_vs_null_progenitor_proliferation
    name: Allele-matched comparison of progenitor proliferation under TUBG1 missense versus null
    description: >-
      In a single model system, compare a heterozygous patient missense allele
      against a loss-of-function allele, measuring progenitor proliferation,
      neuronal output and migration side by side, to test whether the
      neurogenesis phenotype is allele-class-dependent.
    decision_criterion: >-
      If progenitor proliferation is impaired by the null but not by the
      heterozygous missense allele, the neurogenesis arm belongs to gamma-tubulin
      deficiency rather than to human TUBG1 disease, and the locomotion-only
      model stands. If the missense allele also impairs proliferation, this entry
      needs a progenitor branch and a second module conformance.
    would_support:
    - pathophysiology#Failure of Neuronal Locomotion Initiation
  evidence:
  - reference: PMID:31086189
    reference_title: "TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We show that TUBG1 mutants affect neuronal positioning, disrupting the
      locomotion of new-born neurons but without affecting progenitors'
      proliferation.
    explanation: >-
      The mouse position: locomotion fails, proliferation does not.
  - reference: PMID:39215931
    reference_title: "tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model."
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We demonstrate that γ-tubulin deficiency disrupts neurogenesis and brain
      development, mirroring microcephaly phenotypes.
    explanation: >-
      The zebrafish position, which contradicts the mouse claim that neurogenesis
      is spared - recorded as REFUTE against that specific claim, with the
      allele-class caveat argued in the rationale.
- discussion_id: gap_tubg1_imaging_signature_divergence
  prompt: >-
    Why does a tubulin-gene lesion produce a LIS1-like imaging phenotype with
    often-spared basal ganglia, brainstem and cerebellum but variable
    corpus-callosum morphology, when the alpha- and beta-tubulinopathies often
    malform those structures?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Posterior-Predominant Pachygyria with Spared Deep Structures
  - pathophysiology#Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation
  rationale: >-
    This is the sharpest natural experiment available in the tubulinopathy
    grouping, and it is unresolved. Dysmorphic basal ganglia with a fused
    striatum are reported as pathognomonic in roughly three quarters of
    tubulinopathy cases and are one of the imaging features that raises the
    diagnosis at all - yet in TUBG1 disease those structures are often normal.
    The proposed explanation is that gamma-tubulin's job is microtubule
    nucleation rather than lattice assembly, so its failure does not perturb the
    same processes. That is plausible but currently an inference from function,
    not a demonstration: nobody has shown which developmental process in the
    basal ganglia and commissures requires lattice integrity but tolerates
    reduced nucleation fidelity. The practical consequence is diagnostic - a
    tubulin-gene disorder that looks like LIS1 on MRI will be missed by an
    imaging-led differential that treats dysmorphic basal ganglia as required.
  evidence:
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Basal ganglia, corpus callosum, brainstem, and cerebellum were often
      normal, in contrast to patients with variants in other tubulin genes where
      these structures are frequently malformed.
    explanation: >-
      Establishes the divergence in imaging phenotype that this gap is about.
  - reference: PMID:29706637
    reference_title: "Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      This difference may, at least in part, be explained by gamma-tubulin's
      physiological function in microtubule nucleation, which differs from that
      of alpha and beta-tubulin.
    explanation: >-
      The proposed explanation, stated by its authors as partial and hedged, is
      why this remains an open gap.
  - reference: PMID:41901019
    reference_title: The Role of Prenatal Neurosonography in Identification of Tubulinopathy-Narrative Review.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      basal ganglia dysmorphism with a fused striatum (pathognomonic in
      approximately 75% of cases)
    explanation: >-
      Quantifies how central basal ganglia dysmorphism is to tubulinopathy
      imaging generally, which is what makes its absence in TUBG1 notable and
      diagnostically hazardous.
  - reference: PMID:23603762
    reference_title: "Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third but less severe case (P478: c.991A>C, p.T331P) showed posterior
      pachygyria and laminar heterotopia with a thick and dysmorphic corpus
      callosum (Fig. 4b and Supplementary Table 4).
    explanation: >-
      Qualifies the question's imaging contrast: basal-ganglia sparing remains
      the stronger discriminator, while corpus-callosum morphology varies.
notes: >-
  Created 2026-08-20 from recommendation 1 of
  docs/reports/tubulinopathies-grouping-review-2026-08-20.md, which identified
  TUBG1 as the one clear membership gap in the Tubulinopathies grouping. The gene
  was already named as a tubulinopathy gene inside the KB - in the evidence
  quoted by the TUBA1A entry, in the notes of that same entry, and as a
  lissencephaly gene in Lissencephaly_Spectrum_Disorders - without having an
  entry of its own.

  Modeled as a distinct Disease rather than folded into
  Lissencephaly_Spectrum_Disorders or into a generic tubulinopathy lump, for two
  reasons that are mechanistic rather than administrative. First, the molecular
  lesion is in microtubule nucleation (gamma-TuRC) rather than in the heterodimer
  that forms the lattice, which is a different failure mode from every other
  member of the grouping. Second, the imaging phenotype diverges sharply from its
  own gene family - basal ganglia, brainstem and cerebellum are often spared,
  while corpus-callosum morphology is variable - and resembles LIS1/PAFAH1B1
  instead.

  Deliberately NOT conformed to
  neural_progenitor_centrosome_spindle_dysfunction, despite gamma-tubulin being a
  centrosomal protein: the mouse work reports intact progenitor proliferation and
  no major centrosome structural or functional defect in patient fibroblasts. The
  conflicting zebrafish neurogenesis result is curated as an open discussion
  rather than as a second conformance, because the allele classes differ
  (heterozygous missense versus somatic null). If an allele-matched experiment
  shows the missense allele also impairs proliferation, that conformance should
  be added.

  functional_impact_category is UNKNOWN by deliberate choice, not omission - see
  the genetic_context description on the trigger node. All evidence snippets are
  quoted from cached reference text.
📚

References & Deep Research

References

14
PMID:23603762
Mutations in TUBG1, DYNC1H1, KIF5C and KIF2A cause malformations of cortical development and microcephaly.
No top-level findings curated for this source.
PMID:31086189
TUBG1 missense variants underlying cortical malformations disrupt neuronal locomotion and microtubule dynamics but not neurogenesis.
No top-level findings curated for this source.
PMID:29706637
Tubulinopathies continued: refining the phenotypic spectrum associated with variants in TUBG1.
No top-level findings curated for this source.
PMID:39215931
tubg1 Somatic Mutants Show Tubulinopathy-Associated Neurodevelopmental Phenotypes in a Zebrafish Model.
No top-level findings curated for this source.
PMID:40298439
Two New Cases Expand the Phenotypic Spectrum of TUBG1 Missense Variants.
No top-level findings curated for this source.
PMID:38919239
Craniosynostosis Associated With Novel TUBG1 Mutation (NM_001070.4:c.821C>T) (p.Thr274Ile).
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:42177523
Gene-specific long-term course, neurodevelopmental outcome and quality of life in patients with LIS1/PAFAH1B1-, DCX-, DYNC1H1-, TUBA1A- and TUBG1-related lissencephaly.
No top-level findings curated for this source.
PMID:42472988
Genotypic and phenotypic heterogeneity in tubulinopathies: insights from a Turkish multicenter cohort.
No top-level findings curated for this source.
PMID:41901019
The Role of Prenatal Neurosonography in Identification of Tubulinopathy-Narrative Review.
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.
PMID:38912084
Gamma-Tubulin 1 (TUBG1) Mutation-Associated Lissencephaly and Microcephaly in an Indian Child: A Rare Case.
No top-level findings curated for this source.
PMID:41070651
[Clinical phenotype and genetic analysis of a child with Cortical dysplasia, complex, with other brain malformations 4 and epilepsy due to a TUBG1 gene variant].
No top-level findings curated for this source.