Microtubule-Dependent Neuronal Migration Failure Module

Neuroscience Developmental biology Module microtubule_dependent_neuronal_migration_failure 13 disorders Pathograph 8

Conserved cortical malformation mechanism in which pathogenic variants in microtubule-associated proteins, tubulin subunits, gamma-tubulin nucleation machinery, dynein, or kinesin motors perturb microtubule dynamics and microtubule-based movement in developing neurons. The shared skeleton is microtubule apparatus perturbation followed by defective neuronal nucleokinesis/radial migration and cortical dyslamination or neuronal ectopia. This module is intended for lissencephaly, subcortical band heterotopia, and selected polymicrogyria-like malformations where microtubule-dependent neuronal migration is central.

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Pathophysiology Nodes

4 shared nodes are defined in this module.

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Cell Types

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Biological Processes

microtubule cytoskeleton organization GO:0000226 ↕ DYSREGULATED microtubule-based process GO:0007017 ↕ DYSREGULATED neuron migration GO:0001764 ↓ DECREASED microtubule-based movement GO:0007018 ↕ DYSREGULATED cerebral cortex development GO:0021987 ↕ DYSREGULATED neuron projection morphogenesis GO:0048812 ↕ DYSREGULATED neuron projection guidance GO:0097485 ↕ DYSREGULATED

Notes

This is a mechanism module, not a disease or a broad "tubulinopathy" lump. Disorder entries should use conforms_to only when the core pathograph is microtubule-dependent neuronal motility or migration failure. Conforming disease entries may substitute the specific gene and mechanism, such as PAFAH1B1/LIS1 dosage-sensitive dynein regulation, DCX microtubule stabilization, TUBA1A or TUBB2B heterodimer/MAP-binding disruption, TUBG1 nucleation defects, or DYNC1H1/KIF motor dysfunction. Do not use this module as the primary skeleton when the dominant mechanism is neural progenitor depletion/spindle failure, apical neuroependyma integrity failure, pial basement-membrane/radial-glial endfoot failure, Reelin terminal-translocation signaling, ARX interneuronopathy, or PI3K-AKT-mTOR overgrowth; those should use separate modules or subtype branches. TUBB3-related disease may conform only for its microtubule/axon-guidance branch if cortical migration is not the primary demonstrated defect.

Mechanistic Hypotheses

Microtubule-Dependent Neuronal Migration Model

microtubule_migration_model CANONICAL Evidence: 1

Evidence balance 1 support

Microtubule-associated proteins, tubulin subunits, dynein, and kinesin motors form a coupled apparatus for neuronal polarization, nucleokinesis, migration, and projection outgrowth. Pathogenic variants disrupt this apparatus through altered microtubule polymerization, heterodimer formation, MAP binding, motor ATPase activity, microtubule binding, or cargo/centrosome-nucleus coupling. Developing neurons then fail to migrate to appropriate cortical positions, producing dyslamination, lissencephaly/subcortical-band-heterotopia patterns, and selected polymicrogyria-like cortical malformations.

Discussions and Knowledge Gaps

Which microtubule-dependent migration defects are conserved across mouse in utero perturbation/knockout models, biochemical or cultured-cell assays, and human iPSC-derived cortical organoids, and which require human-specific progenitors such as outer radial glia?

HUMAN MODEL MISMATCH OPEN gap_microtubule_human_model_translatability

Attached to: Microtubule Apparatus Perturbation Microtubule-Based Neuronal Motility Failure

The seed review emphasized rodent-versus-human cortical-development differences and the value of iPSC/organoid systems. For curation this should be treated as a human/model mismatch knowledge-gap category: mouse migration evidence can establish conserved mechanisms, but organoids or fetal-human data may be needed to decide whether outer-radial-glia timing, cleavage orientation, or human-specific transcript usage changes the pathograph for a specific disorder.

Proposed experiments: Isogenic cortical-organoid migration rescue panel

Why do lesions in different tubulin isotype genes, all converging on this module, produce characteristically different cortical malformation patterns - TUBA1A lissencephaly, TUBB2A/TUBB2B polymicrogyria-like dysgyria, TUBB3 axon-guidance disease, TUBB microcephaly?

KNOWLEDGE GAP OPEN gap_tubulin_isotype_specificity_of_migration_lesions

Attached to: Microtubule Apparatus Perturbation Microtubule-Based Neuronal Motility Failure

The Tubulinopathies grouping keeps its members as separate Disease entries on the premise that tubulin isotypes differ in expression timing and binding partners, so an equivalent lesion in a different isotype yields a different malformation. That premise is the load-bearing justification for the split, and until recently it was asserted rather than evidenced. Two independent lines of 2026 work now supply the two halves of a mechanism. First, composition: spatially resolved atlases show tubulin isotype transcripts are not interchangeable across cell states, ranging from broadly expressed (TUBA1A, TUBA1B) to cell-type-restricted, with TUBB3 and TUBG1 enriched in particular lineages. Second, consequence: the isotype-specific C-terminal tails differentially engage motor proteins, with TUBB2A, TUBB2B and TUBB2C altering the conformational motions of the dynein microtubule-binding and stalk domains. Together these predict that which isotype is mutated determines both WHERE and WHEN the lesion is felt and WHICH motor-dependent step degrades. What is still missing is the direct test: no study has taken one substitution to an equivalent structural position across several isotypes in a common cellular background and measured the divergence. Until that exists, isotype specificity remains a well-motivated model rather than a demonstrated explanation, and curators should not attribute a member's distinctive malformation pattern to its isotype as though the causal chain were established.

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Experimental Models

Human iPSC-derived cerebral organoid migration model ORGANOID namo:Organoid

Human pluripotent-stem-cell-derived three-dimensional cerebral or cortical organoids used to model lissencephaly and microcephaly mechanisms, including live assays of neuronal migration, neuroepithelial apoptosis, cleavage orientation, and outer-radial-glial mitotic behavior.

Organism

human NCBITaxon:9606

Tissue

cerebral cortex UBERON:0000956

Cell source

Human embryonic stem cells, patient-derived iPSCs, or isogenic engineered iPSCs

Culture

Three-dimensional cerebral/cortical organoid culture with live imaging and single-cell profiling

Publication

PMID:28111201

Pathograph links

Microtubule Apparatus Perturbation Assays whether variant effects on microtubule-linked mitotic behavior, radial-glial organization, or organoid growth are conserved in a human cortical model. Evidence: 1

Microtubule-Based Neuronal Motility Failure Supports live or endpoint assays of cortical neuron migration from organoids and rescue by isogenic correction.

Readouts

Average migration speed of organoid-derived neurons on radial processes

Live imaging over 48 hours from one day after organoid attachment, tracking DCX-positive neurons migrating out along neurite and radial-glial fibre bundles. Wild type 20 micrometres per hour against 13 in Miller-Dieker syndrome organoids.

Direction: DECREASED

Interpretation: The quantity a per-step nucleokinesis rate stands for in a migration model, measured in a human cortical system rather than inferred. The authors note the wild-type value matches ferret cortical explants.

Evidence: 2

Track straightness of migrating organoid-derived neurons

Total migratory track length divided by net displacement, close to 1 in wild type and reduced in Miller-Dieker neurons, which initiate but do not maintain saltatory migration and spend much of the time tumbling in place.

Direction: DECREASED

Interpretation: Separates a neuron that moves slowly along its fibre from one that moves without net progress. A one-dimensional migration model collapses the two, so this measures a failure mode such a model cannot express.

Evidence: 1

Fraction of organoid-derived neurons reaching the pial surface in cortical-explant co-culture

Position relative to the ventricular and pial surfaces after four days of co-culture of labelled organoids with human cortical tissue slices: 50 percent of wild-type migrating neurons reached the pial surface against about 10 percent of Miller-Dieker neurons.

Direction: DECREASED

Interpretation: An endpoint distribution across the radial axis in a human substrate, and so the closest measured counterpart to the fraction of neurons a migration model scores as having reached the cortical plate when its developmental window closes.

Evidence: 2

Migration speed and track straightness after isogenic rescue of the 17p13.3 deletion

Organoids from an iPSC line in which the Miller-Dieker ring chromosome was lost and replaced by a wild-type chromosome 17 through compensatory uniparental isodisomy.

Direction: RESTORED

Interpretation: An isogenic rescue arm: the deficit tracks the deletion rather than the line, which is what makes the speed and straightness values usable as calibration targets rather than line-specific observations.

Evidence: 1

Findings

Patient-derived MDS cerebral organoids show a migration defect that can be rescued by correction of the causal chromosomal deletion.

Evidence: 1

Human cerebral organoid cortical cells can recapitulate fetal-neocortex gene-expression programs relevant to cortical development.

Evidence: 1

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Animal Models

Pafah1b1 (Lis1) allelic-series mouse

A dosage series rather than a single genotype. Three mutant Pafah1b1 alleles were combined so activity could be lowered in steps, and the severity of the cortical, hippocampal and olfactory-bulb disorganization tracks the step: heterozygotes show delayed migration, further reduction gives more severe disorganization with cerebellar involvement, and homozygous nulls die soon after implantation. The migration delay is cell-autonomous to the neuron.

Species

Mouse

Genotype

Pafah1b1 (Lis1) allelic series - three mutant alleles combined to give graded reductions of activity, from heterozygous null through lower-activity compound genotypes to homozygous null

Genes

PAFAH1B1 hgnc:8574

Publication

PMID:9697693

Pathograph links

Microtubule Apparatus Perturbation perturbs fidelity: moderate observes: organism Lowers the dose of a dynein regulator in graded steps, the closest available experimental counterpart to a graded perturbation of the microtubule apparatus.

Limitations: Mouse, and one locus of the nine genes this node covers: a LIS1 dose series says nothing about how a tubulin heterodimer-formation defect or a kinesin ATPase defect scales. The allele combinations are steps of gene dosage, not a measured scale of microtubule dysfunction.

Divergences from the human mechanism

proxy quantity qualifying

Pafah1b1 gene dosage stands in for the state of the microtubule apparatus. The node's quantity is the apparatus itself, which this model perturbs through one of its regulators rather than measuring.

species mismatch qualifying

The mouse cortex is lissencephalic, so gyral outcome cannot be read from it, and the human-specific outer radial glia the organoid model reports on are absent. The series speaks to migration timing, not cortical form.

Readouts

Severity of brain disorganization across the Pafah1b1 activity series

Ordinal severity across the allelic series: heterozygous null, then genotypes with further reduced activity, then homozygous null.

Direction: INCREASED

Interpretation: The empirical basis for treating a perturbation of this node as graded and monotone rather than binary. It is an ordinal series, so it constrains the direction of a dose-response relation without giving its shape.

Evidence: 3

Microtubule-Based Neuronal Motility Failure recapitulates fidelity: moderate observes: organism Delayed neuronal migration producing cortical, hippocampal and olfactory bulb disorganization, by a cell-autonomous neuronal pathway.

Limitations: Reported as delayed migration and disorganization rather than as a zone distribution or a migration rate, so the series constrains ordering and cell autonomy but carries no number a model could be fitted to.

Readouts

Cell autonomy of the migration delay

neuron migration GO:0001764 ↓ DECREASED

Direction: DECREASED

Interpretation: A neuron's migration depends on its own Pafah1b1 dose. This is what licenses a cell-autonomous treatment of the perturbation, and so what makes a mosaic regime - affected and unaffected neurons migrating differently side by side - a representable state rather than an assumption.

Evidence: 1

Curated on the module rather than on a disorder entry because the series is used here as the dose-response evidence behind treating this module's trigger node as graded. PAFAH1B1-related disorder entries may cite it independently.

Evidence: 1

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Computational Models

Microtubule-Dependent Radial Neuronal Migration Agent-Based Model Agent-based rule specification (YAML) Python (standard library and PyYAML) AGENT_BASED

A one-dimensional, stochastic agent-based model of radial migration along a cortical column, in which six birth cohorts of neurons move from the ventricular zone through the intermediate zone to a cortical plate that grows inside-out as they settle. Authored in this repository rather than curated from a publication: each of its five rules transcribes a node or causal edge of this module (an apparatus perturbation that is cell-autonomous, slows nucleokinesis and can arrest a neuron in the intermediate zone, scored as dyslamination and ectopia when the developmental window closes), and the spec records per rule which curated edge it encodes and which choices the edge did not itself make. The one rule with no curated source, inside-out settling, is the null model of normal lamination the module's failure claims presuppose, and is labelled as a background assumption. The curated intervention is encoded as a swept fraction of the perturbation removed. The model asserts no biology of its own and nothing in it is fitted to data: every rate is a placeholder chosen so that the wild-type scenario completes migration inside the window, so the results are orderings of regimes, never quantities.

Model page: rules, runs, run it in the browser →

Variable	Unit	Phenotype Thresholds
perturbation Degree of microtubule-apparatus disruption in an affected neuron, 0 to 1. The scalar input the module's trigger node becomes; it is not a measured quantity of any gene.	dimensionless
affected_fraction Fraction of neurons carrying the perturbation. 1 for a constitutional variant; below 1 for a defect present in only some neurons, representable because the curated evidence states the defect is cell-autonomous.	dimensionless
cortical_plate_fraction Fraction of neurons settled in the cortical plate when the developmental window closes.	dimensionless	Abnormality of neuronal migration below 0.95
arrested_fraction Fraction of neurons permanently arrested in the intermediate zone when the window closes. Only the arrest rule can raise it; slowing alone leaves it at zero.	dimensionless	Gray matter heterotopia above 0.1
lamination_fidelity Fraction of settled neuron pairs from different birth cohorts whose depth order matches birth order. 1 is perfect inside-out lamination, 0.5 is no relation between birth order and depth. Deliberately unmapped: an OLS search of HPO for "cortical lamination" (2026-09-27) returned no term, and lissencephaly would over-claim, since the model cannot produce the thick plate that term implies.	dimensionless
band_score Among arrested affected neurons, the fraction lying within five depth units of their median depth; high when they form a band rather than a diffuse scatter.	dimensionless	Subcortical band heterotopia above 0.6

Pathograph links

Microtubule Apparatus Perturbation perturbs fidelity: low observes: cellular The node is the model's input: a scalar in 0 to 1 that every rule reads through the effective perturbation of each affected neuron. The model does not represent the apparatus itself.

Limitations: No microtubule, motor, MAP or tubulin isotype is represented; the node's DYSREGULATED microtubule cytoskeleton organization is a single number whose only meaning is how much it slows and arrests an agent. The module's list of nine genes has no counterpart, so the model cannot distinguish one tubulinopathy from another.

Divergences from the human mechanism

proxy quantity qualifying

A scalar perturbation strength stands in for the state of the microtubule apparatus. The curated node describes qualitatively different lesions (nucleation defects, heterodimer formation, MAP binding, dynein binding, kinesin ATPase) that the model collapses into one degree of slowing.

calibration provenance qualifying

Nothing is calibrated. No rate, threshold or window length is fitted to any dataset; the scenario values are placeholders chosen around a wild-type run that completes migration. The Pafah1b1 allelic-series animal model curated on this module is dose-response evidence that a graded, monotone perturbation is the right shape, but it is an ordinal series of three steps and fixes no scale, so it cannot set this scalar's units.

Microtubule-Based Neuronal Motility Failure partially recapitulates fidelity: low observes: cellular Reproduced as two per-agent rules read off the node: a per-step probability of nucleokinesis that falls linearly with the effective perturbation (the node's DECREASED neuron migration), and a per-step hazard of permanent arrest inside the intermediate zone (the node's "arrested cells in intermediate/subventricular regions"). The two are swept separately so delayed and arrested migration can be told apart.

Limitations: One-dimensional and cell-autonomous. Radial glia are the axis rather than agents; leading-process stabilization, centrosome-nucleus coupling and the multipolar, locomotion and terminal-translocation phases the node names are collapsed into a single step probability. Linear dependence on the perturbation is the least-committed monotone choice, not a curated one.

Divergences from the human mechanism

structural idealization qualifying

Migration is a biased random walk along one axis with a constant step. Nucleokinesis in the cited sources is a saltatory, phase-dependent movement with a leading process, and the node's several failure modes (delay, arrest, abnormal positioning) are two parameters. The organoid track-straightness readout measures a third that neither parameter expresses: a neuron that moves without net progress, tumbling in place rather than advancing slowly.

boundary omission qualifying

The radial-glial scaffold the curated node names as the substrate of locomotion is not in the model, so neither is any defect of the scaffold itself; the module's own notes route pial and radial-glial endfoot failure to other modules, and the model inherits that boundary.

calibration provenance qualifying

The base motility, arrest hazard and cohort timing are placeholders. Measured counterparts for two of them are now curated on this module and the model is fitted to neither: the organoid link's migration-speed readout (20 against 13 micrometres per hour) is what the per-step nucleokinesis rate stands for, and its pial-surface readout (50 against about 10 percent) is the measured counterpart of the plate fraction. Nothing in the model reads them, so the perturbation at which a regime changes remains a property of the placeholders.

Readouts

Mean arrival delay from birth to settling

radial neuron migration GO:0021799 ↓ DECREASED

Direction: INCREASED

Interpretation: Rises monotonically with the perturbation in both sweeps, from 76 steps at wild type to over 200 where any neuron still settles.

Fraction of neurons arrested in the intermediate zone

Gray matter heterotopia HP:0002282

Direction: INCREASED

Interpretation: Zero without the arrest rule at any perturbation; with it, rises with the perturbation and is the only route by which neurons end in the intermediate zone rather than merely late.

Cortical Dyslamination and Neuronal Ectopia partially recapitulates fidelity: low observes: cellular Scored rather than simulated: when the developmental window closes, the settled neurons' depth order is compared with their birth order and the unsettled neurons are counted as ectopic by zone. The band score asks whether arrested affected neurons cluster in depth.

Limitations: The tissue-level outcome is inferred from cell positions on one axis, so no gyral pattern, plate thickness beyond a count, or cortical layering beyond rank order is represented. The window length is unfitted and decides how much delay counts as ectopia. The model cannot produce a thickened, poorly laminated plate, because the module curates no interaction between a delayed neuron and neurons already settled.

Divergences from the human mechanism

scale extrapolation qualifying

The model observes cell positions and settle order; dyslamination, heterotopia and lissencephaly are tissue-scale outcomes it reaches by scoring those positions against fixed thresholds stated in the results file, not by simulating tissue.

boundary omission invalidating

The lissencephalic plate the node describes is thick and poorly laminated. The model has no rule by which a delayed neuron fails to pass earlier-born neurons or by which the plate thickens, so for that specific histology the model is a placeholder: its only dyslamination is cohort interleaving from arrival-time spread, plus stranded late cohorts. Ectopia and a mosaic band are the outcomes it can represent.

temporal scope qualifying

Scoring at one fixed window end; the module says the outcome depends on the developmental window, and a longer window would reclassify delayed neurons as settled.

Readouts

Lamination fidelity across the perturbation sweep

Direction: DECREASED

Interpretation: Falls from 1.0 at wild type as slowed cohorts interleave, and is undefined once no neuron settles.

Band score in the mosaic scenarios

Subcortical band heterotopia HP:0032409

Direction: INCREASED

Interpretation: Between 0.63 and 0.73 across the affected-fraction sweep (fractions 0.1 to 0.9) and 0.75 in the mosaic_severe scenario, whenever a fraction of neurons carries a severe perturbation and the rest build a normal plate above them, against 0.19 to 0.31 when every neuron is affected at perturbations up to 0.7.

Findings

Uniform slowing of every neuron, the reading of the module's central edge with no arrest, preserves inside-out lamination until the perturbation is strong enough to strand the latest-born cohorts outside the window.

"In the perturbation sweep without arrest, every neuron still settles and the lamination fidelity stays above 0.97 up to a perturbation of 0.3; beyond that the plate fraction falls cohort by cohort from the latest-born down (in the delayed_migration scenario, at 0.5, the first two cohorts settle..."

Arrest, not slowing, is what puts neurons in the intermediate zone, and with every neuron affected the arrested cells scatter rather than band.

"With arrest switched on, the arrested fraction rises with the perturbation up to 0.8 while the in-transit fraction stays small until the perturbation is severe, so ectopia in the intermediate zone is the arrest rule's signature. The band score of those arrested cells stays between 0.19 and 0.31..."

A heterotopic band beneath a normally laminated cortex emerges only when the perturbation is present in a fraction of neurons, and then at every fraction from 0.1 to 0.9.

"In the affected-fraction sweep at a severe perturbation, the unaffected neurons build a plate with lamination fidelity above 0.999 at every fraction, the affected neurons arrest in a band with a band score of 0.63 to 0.73, and the pattern classifies as band heterotopia from 0.1 to 0.9. This..."

The curated intervention rescues migration monotonically in the model, but that is an implication of the RESTORES edge, not a reported result.

"Removing 60% of a severe perturbation moves the outcome from complete migration failure to a 71% plate with fidelity 0.98, and full removal restores the wild-type pattern. The cited work (PMID:42589608) measures restoration of the microtubule network and primary cilia in cells and reports..."

Notes

Scope is the radial-migration branch; the axon-guidance branch of this module is deliberately outside the model. Not runnable through dismech-perturb, which executes SBML and cannot run an agent-based simulation, so the models browser reports it as reference-only. Run it with `uv run python models/neuronal_migration_abm/run.py`, where `--check` verifies the committed results and `--print` summarises them. The rules are written in the shape of a PhysiCell cell-behaviour rule (cell type, signal, direction, behaviour) so they could be ported to that engine; no PhysiCell rules file is committed, because the half-max and Hill parameters such a file needs would have to be invented.

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Used By Disorder Entries

KATNB1-related Cortical Malformation via Microtubule-Dependent Neurogenesis and Neuronal Migration Failure → Microtubule-Based Neuronal Motility Failure , Reduced Cortical Output and Microlissencephaly → Cortical Dyslamination and Neuronal Ectopia

KIF2A-related Complex Cortical Dysplasia via KIF2A Motor-Domain Nucleotide-Pocket Disruption → Microtubule Apparatus Perturbation , Defective Neuronal Migration and Positioning → Microtubule-Based Neuronal Motility Failure , Posterior-Predominant Classic Lissencephaly → Cortical Dyslamination and Neuronal Ectopia

Lissencephaly Spectrum Disorders via Cytoskeletal and Microtubule Dysfunction → Microtubule Apparatus Perturbation , LIS1-NUDEL-Dynein Nucleokinesis Failure → Microtubule-Based Neuronal Motility Failure , DCX Microtubule Stabilization Failure → Microtubule Apparatus Perturbation

Miller-Dieker Lissencephaly Syndrome via LIS1 Haploinsufficiency and Dynein/Microtubule Motor Dysfunction → Microtubule-Based Neuronal Motility Failure

NDE1-related Microcephaly-Lissencephaly via Dynein-Dependent Neuronal Migration Failure → Microtubule-Based Neuronal Motility Failure , Cortical Dyslamination and Lissencephaly → Cortical Dyslamination and Neuronal Ectopia

Periventricular Nodular Heterotopia 9 via Impaired Microtubule Stabilization in Developing Neurons → Microtubule Apparatus Perturbation , Failure of Radial Neuronal Migration → Microtubule-Based Neuronal Motility Failure , Disrupted Axon Guidance and Cortical Circuit Formation → Axon Guidance and Projection Wiring Defects

SRPX2-related Speech-Epilepsy-Polymicrogyria via Tubulin Acetylation and Neuronal Migration Defect → Microtubule-Based Neuronal Motility Failure , Perisylvian Cortical Organization Failure → Cortical Dyslamination and Neuronal Ectopia

TUBA1A-related Tubulinopathy via Altered Alpha-Tubulin (TUBA1A) Function → Microtubule Apparatus Perturbation , Impaired Microtubule-Dependent Neuronal Migration → Microtubule-Based Neuronal Motility Failure , Cortical Dyslamination and Lissencephaly Spectrum → Cortical Dyslamination and Neuronal Ectopia

TUBB/TUBB5-related Microcephaly via Altered TUBB/TUBB5 Beta-Tubulin Function → Microtubule Apparatus Perturbation , Impaired Neurogenic Division and Migration → Microtubule-Based Neuronal Motility Failure

TUBB2A/TUBB2B-related Cortical Malformation via Altered Beta-Tubulin (TUBB2A/TUBB2B) Function → Microtubule Apparatus Perturbation , Impaired Microtubule-Dependent Neuronal Migration and Organization → Microtubule-Based Neuronal Motility Failure , Tubulinopathy-Associated Dysgyria and Extracortical Malformation Pattern → Cortical Dyslamination and Neuronal Ectopia

TUBB3-related Tubulinopathy via Altered Beta-III Tubulin (TUBB3) Function → Microtubule Apparatus Perturbation , Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure → Axon Guidance and Projection Wiring Defects , Impaired Microtubule-Dependent Neuronal Migration → Microtubule-Based Neuronal Motility Failure , Cortical Dyslamination → Cortical Dyslamination and Neuronal Ectopia

TUBG1-related Tubulinopathy via Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation → Microtubule Apparatus Perturbation , Failure of Neuronal Locomotion Initiation → Microtubule-Based Neuronal Motility Failure , Posterior-Predominant Pachygyria with Spared Deep Structures → Cortical Dyslamination and Neuronal Ectopia

TUBGCP2-related Lissencephaly Spectrum Disorder via Neuronal Migration Failure → Microtubule-Based Neuronal Motility Failure , Lissencephaly Spectrum Cortical Malformation → Cortical Dyslamination and Neuronal Ectopia

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence-backed metadata.

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Pathophysiology

Microtubule Apparatus Perturbation

trigger

Pathogenic variation perturbs the microtubule apparatus used by developing neurons and neural progenitors. Representative mechanisms include defective DCX-mediated microtubule stabilization, impaired alpha/beta-tubulin heterodimer formation or MAP binding, gamma-tubulin nucleation defects, altered dynein microtubule binding, and kinesin ATPase/folding defects.

migrating cortical neuron CL:0000540 radial glial cell CL:0000681

microtubule cytoskeleton organization GO:0000226 ↕ DYSREGULATED microtubule-based process GO:0007017 ↕ DYSREGULATED

Used by disorders

KIF2A-related Complex Cortical Dysplasia as KIF2A Motor-Domain Nucleotide-Pocket Disruption

Lissencephaly Spectrum Disorders as Cytoskeletal and Microtubule Dysfunction

Lissencephaly Spectrum Disorders as DCX Microtubule Stabilization Failure

Periventricular Nodular Heterotopia 9 as Impaired Microtubule Stabilization in Developing Neurons

TUBA1A-related Tubulinopathy as Altered Alpha-Tubulin (TUBA1A) Function

TUBB/TUBB5-related Microcephaly as Altered TUBB/TUBB5 Beta-Tubulin Function

TUBB2A/TUBB2B-related Cortical Malformation as Altered Beta-Tubulin (TUBB2A/TUBB2B) Function

TUBB3-related Tubulinopathy as Altered Beta-III Tubulin (TUBB3) Function

TUBG1-related Tubulinopathy as Altered Gamma-Tubulin (TUBG1) Function in Microtubule Nucleation

Downstream

Microtubule-Based Neuronal Motility Failure Defective microtubule dynamics, MAP binding, and motor function impair the centrosome-nucleus coupling and cytoskeletal remodeling required for radial neuronal migration.
Axon Guidance and Projection Wiring Defects Some tubulin variants, especially TUBB3 variants, primarily alter axon guidance or projection maintenance rather than cortical cell migration. This is an optional branch for conforming entries, not the core skeleton.

Show evidence (4 references)

PMID:10399933 SUPPORT In Vitro

"DCX coassembles with brain microtubules, and recombinant DCX stimulates the polymerization of purified tubulin."

Demonstrates that a classical neuronal-migration protein directly regulates microtubules.

PMID:19465910 SUPPORT In Vitro

"We also show that two disease-associated mutations lead to impaired formation of tubulin heterodimers."

Supports a beta-tubulin mechanism in which disease variants perturb tubulin heterodimer formation.

PMID:20466733 SUPPORT Other

"We also provide cellular and structural data suggesting that LIS-associated mutations of TUBA1A operate via diverse mechanisms that include disruption of binding sites for microtubule-associated proteins (MAPs)."

Supports alpha-tubulin disease variants acting through multiple microtubule-associated mechanisms.

+ 1 more reference

Microtubule-Based Neuronal Motility Failure

central effector

Migrating neurons fail to execute normal microtubule-dependent movement, including leading-process stabilization, nucleokinesis, centrosome-nucleus coupling, and radial migration along radial-glial scaffolds. Depending on the gene and developmental window, the defect can appear as delayed migration, arrested cells in intermediate/subventricular regions, or abnormal neuronal positioning.

migrating cortical neuron CL:0000540 pyramidal neuron CL:0000598

neuron migration GO:0001764 ↓ DECREASED microtubule-based movement GO:0007018 ↕ DYSREGULATED

Used by disorders

KATNB1-related Cortical Malformation as Microtubule-Dependent Neurogenesis and Neuronal Migration Failure

KIF2A-related Complex Cortical Dysplasia as Defective Neuronal Migration and Positioning

Lissencephaly Spectrum Disorders as LIS1-NUDEL-Dynein Nucleokinesis Failure

Miller-Dieker Lissencephaly Syndrome as LIS1 Haploinsufficiency and Dynein/Microtubule Motor Dysfunction

NDE1-related Microcephaly-Lissencephaly as Dynein-Dependent Neuronal Migration Failure

Periventricular Nodular Heterotopia 9 as Failure of Radial Neuronal Migration

SRPX2-related Speech-Epilepsy-Polymicrogyria as Tubulin Acetylation and Neuronal Migration Defect

TUBA1A-related Tubulinopathy as Impaired Microtubule-Dependent Neuronal Migration

TUBB/TUBB5-related Microcephaly as Impaired Neurogenic Division and Migration

TUBB2A/TUBB2B-related Cortical Malformation as Impaired Microtubule-Dependent Neuronal Migration and Organization

TUBB3-related Tubulinopathy as Impaired Microtubule-Dependent Neuronal Migration

TUBG1-related Tubulinopathy as Failure of Neuronal Locomotion Initiation

TUBGCP2-related Lissencephaly Spectrum Disorder as Neuronal Migration Failure

Downstream

Cortical Dyslamination and Neuronal Ectopia Failed or delayed neuronal migration prevents appropriate placement of cortical neurons, producing abnormal lamination, heterotopia, or lissencephaly/pachygyria-like cortical organization.

Show evidence (4 references)

PMID:9697693 SUPPORT Model Organism

"Mice with one inactive allele display cortical, hippocampal and olfactory bulb disorganization resulting from delayed neuronal migration by a cell-autonomous neuronal pathway."

Supports dosage-sensitive PAFAH1B1/Lis1 migration failure in a mouse model.

PMID:10399933 SUPPORT Human Clinical

"Doublecortin (DCX) is required for normal migration of neurons into the cerebral cortex, since mutations in the human gene cause a disruption of cortical neuronal migration."

Connects human DCX mutations to disrupted cortical neuronal migration.

PMID:19465910 SUPPORT Model Organism

"In utero RNAi-based inactivation demonstrates that TUBB2B is required for neuronal migration."

Supports a beta-tubulin requirement for neuronal migration in an in vivo perturbation model.

+ 1 more reference

Cortical Dyslamination and Neuronal Ectopia

effector

The tissue-level effect is abnormal cortical architecture: neurons remain ectopic, the cortical plate is thickened or poorly laminated, and gyral patterning may show lissencephaly, pachygyria, subcortical band heterotopia, or selected polymicrogyria-like malformations. Disorder-specific entries should state the relevant anatomic gradient and whether pial basement membrane failure, progenitor depletion, or another module is also needed.

cortical neuron CL:0000540

cerebral cortex development GO:0021987 ↕ DYSREGULATED neuron migration GO:0001764 ↓ DECREASED

Used by disorders

KATNB1-related Cortical Malformation as Reduced Cortical Output and Microlissencephaly

KIF2A-related Complex Cortical Dysplasia as Posterior-Predominant Classic Lissencephaly

NDE1-related Microcephaly-Lissencephaly as Cortical Dyslamination and Lissencephaly

SRPX2-related Speech-Epilepsy-Polymicrogyria as Perisylvian Cortical Organization Failure

TUBA1A-related Tubulinopathy as Cortical Dyslamination and Lissencephaly Spectrum

TUBB2A/TUBB2B-related Cortical Malformation as Tubulinopathy-Associated Dysgyria and Extracortical Malformation Pattern

TUBB3-related Tubulinopathy as Cortical Dyslamination

TUBG1-related Tubulinopathy as Posterior-Predominant Pachygyria with Spared Deep Structures

TUBGCP2-related Lissencephaly Spectrum Disorder as Lissencephaly Spectrum Cortical Malformation

Show evidence (3 references)

PMID:19465910 SUPPORT Human Clinical

"Polymicrogyria is a relatively common but poorly understood defect of cortical development characterized by numerous small gyri and a thick disorganized cortical plate lacking normal lamination."

Establishes dyslaminated cortical architecture as a human cortical malformation endpoint in a TUBB2B-associated study.

PMID:20466733 SUPPORT Human Clinical

"We identified novel and recurrent TUBA1A mutations in approximately 1% of children with classic LIS and in approximately 30% of children with LCH"

Supports TUBA1A-associated lissencephaly/cerebellar-hypoplasia phenotypes as human endpoints of tubulin-related microtubule dysfunction.

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."

Supports human cortical malformation association for gamma-tubulin and microtubule motor genes in the module scope.

Axon Guidance and Projection Wiring Defects

amplifier

Optional side branch in which the same microtubule/tubulin apparatus disrupts axon guidance, commissural tract development, or long-range projection maintenance. This branch is important for TUBB3-related phenotypes and some broader tubulin/motor disorders, but its presence should not be assumed for all conforming microtubule-migration entries.

neuron CL:0000540

neuron projection morphogenesis GO:0048812 ↕ DYSREGULATED neuron projection guidance GO:0097485 ↕ DYSREGULATED

Used by disorders

Periventricular Nodular Heterotopia 9 as Disrupted Axon Guidance and Cortical Circuit Formation

TUBB3-related Tubulinopathy as Impaired Kinesin-Microtubule Interaction and Axon Guidance Failure

Show evidence (2 references)

PMID:20074521 SUPPORT Model Organism

"A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities."

Supports axon guidance as a distinct TUBB3-related branch and explains why TUBB3 should not be lumped uncritically with core cortical migration failure.

PMID:20074521 SUPPORT Other

"These findings demonstrate that normal TUBB3 is required for axon guidance and maintenance in mammals."

Supports the optional projection-wiring branch of the microtubule module.

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Treatments

CRISPRa beta-tubulin isotype compensation

gene therapy NCIT:C15238

Platform: Gene therapy

CRISPRa-mediated noncutting transcriptional activation of alternative β-tubulin isotypes partially rescued microtubule abnormalities and primary cilium formation in a TUBB G308S hTERT-RPE1 cell model. Targeted genes included TUBB2A, TUBB4A, and TUBB6. Readouts included microtubule fluorescence intensity, curvature, and primary cilium formation. Rescue of neuronal migration or cortical development, efficacy across other variants or module-associated disorders, and clinical benefit remain unestablished. The intervention is mutation-independent by design and targets the shared downstream microtubule-apparatus state rather than correcting the causal allele. This is PRECLINICAL cell-based work - no animal efficacy, no tolerability data, and no clinical trial - and must not be curated on a disorder entry as an available therapy.

Mechanism target:

RESTORES Microtubule Apparatus Perturbation — CRISPRa-mediated upregulation of wild-type beta-tubulin isotypes (TUBB2A, TUBB4A, TUBB6) partially rescued cellular phenotypes in a TUBB G308S hTERT-RPE1 cell model. Measured effects included increased microtubule fluorescence intensity and decreased curvature, plus restoration of primary cilium formation. These findings are specific to the tested cell model and do not establish neuronal migration rescue, cortical development rescue, efficacy across other tubulinopathy variants, or clinical translatability. Evidence: 2

Evidence: 1

Preclinical cell-based only (demonstrated in TUBB G308S hTERT-RPE1 cells) as of 2026-08. Efficacy in neuronal migration, cortical development, animal models, or clinical settings remains unestablished. Curated on the module because the intervention is mutation-independent by design; a conforming disorder entry should reference this module entry rather than duplicating it as an available treatment, and should explicitly note that neuronal migration rescue is not yet established.