SPTAN1-Related Developmental and Epileptic Encephalopathy

Mendelian MONDO:0013277 Pathograph 13 Show in embeddings browser Epilepsy Neurological Disease

SPTAN1-related developmental and epileptic encephalopathy (DEE5) is caused by de novo in-frame deletions and duplications in the last two spectrin repeats of alpha-II spectrin, the region required for alpha/beta spectrin heterodimer nucleation. The mutant protein still binds beta-spectrin but forms thermolabile heterodimers that aggregate, sequestering wild-type subunits - a dominant-negative mechanism rather than haploinsufficiency, which is why the position and type of variant, not merely its presence, determines whether a person develops this severe phenotype or one of the much milder SPTAN1 disorders. Aggregates disrupt the axon initial segment and its ankyrin-G and sodium-channel clustering, and inhibitory innervation is reduced. Clinically this produces West syndrome with hypsarrhythmia, cerebral hypomyelination, spastic quadriplegia, acquired microcephaly and profound developmental impairment, with brainstem and cerebellar atrophy as imaging hallmarks.

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1
Inheritance
14
Pathophys.
9
Phenotypes
3
Gaps
13
Pathograph
1
Genes
2
Medical Actions
3
Models
1
Deep Research
👪

Inheritance

1
Autosomal dominant HP:0000006
Heterozygous and de novo. The mechanism is dominant-negative rather than haploinsufficient, which is a stronger statement than "dominant" alone and is evidenced by heterozygous null mice being unaffected.
Autosomal dominant inheritance
Show evidence (1 reference)
PMID:36831804 SUPPORT Model Organism
"no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice"
Losing one copy is not sufficient to cause disease in mice, which is the observation that separates a dominant-negative mechanism from a dose effect.
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Discussions and Knowledge Gaps

3
Neurons carrying SPTAN1 aggregates have a raised action potential threshold - they fire less readily. How does a lesion that makes individual neurons harder to excite produce an infantile epileptic encephalopathy?
CONTROVERSY OPEN controversy_seizures_despite_raised_firing_threshold
Attached to
pathophysiology#Elevated Action Potential Threshold pathophysiology#Reduced Inhibitory Innervation pathophysiology#Cortical Network Disinhibition
The measured direction is the opposite of the naive expectation for an epilepsy gene, and the pathograph records it that way rather than quietly smoothing it out. Disrupted clustering of voltage-gated sodium channels at the axon initial segment raises the threshold for firing, so the primary cellular defect is reduced excitability. The leading reconciliation is that the network consequence inverts the cellular one: inhibitory innervation is also reduced, and if inhibitory interneurons are more affected than principal cells - or if the loss of inhibitory synapses outweighs the raised threshold in principal cells - the net cortical effect is disinhibition despite less excitable individual neurons. That account is plausible and consistent with everything measured, and it gains support from an intact-animal result: a mouse carrying a destabilising alpha-II spectrin variant shows fewer and structurally defective axon initial segments together with increased neuronal excitability and greater chemoconvulsant sensitivity, so at network level the sign is the opposite of the single-neuron threshold shift. That still does not settle it, because the variant sits in repeat 10 rather than the DEE5 heterodimerization repeats and the measurement is at network rather than cellular level - and no study has compared threshold shifts between interneurons and pyramidal cells in the same preparation, which is exactly the measurement that would decide it. Until then the entry keeps the raised threshold and the reduced inhibition as separate nodes rather than merging them into a single excitability claim, because merging them would hide the tension rather than resolve it.
Proposed experiments
Cell-type-resolved excitability in SPTAN1-mutant cortex
exp_cell_type_resolved_threshold_comparison
Record action potential threshold and firing from identified GABAergic interneurons and pyramidal neurons in the same SPTAN1-mutant cortical preparation, together with inhibitory and excitatory synaptic currents onto each. If interneurons show a larger threshold shift than pyramidal cells, the disinhibition account is supported directly; if both shift equally, the seizures must arise from the synaptic rather than the intrinsic arm, and the raised threshold is a bystander finding.
Show evidence (4 references)
PMID:20493457 SUPPORT In Vitro
"Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
The measurement that creates the puzzle: threshold goes up, not down.
PMID:29337302 SUPPORT Model Organism
"CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
The decreased inhibitory innervation that supplies the candidate resolution, in the same lesion.
PMID:41370269 SUPPORT Model Organism
"Our results show that R1098Q mutant mice display abnormal electroencephalographic activity, increased neuronal excitability, and heightened sensitivity to a chemoconvulsant."
Partially resolves the paradox in the direction of the network account: in an intact animal carrying a destabilising alpha-II spectrin variant, excitability and seizure susceptibility go up, not down. It does not close the question, because this variant sits in repeat 10 rather than the DEE5 heterodimerization repeats, and because the measurement is at network rather than single-neuron level - which is precisely the level at which the sign is proposed to invert.
+ 1 more reference
No published animal model carries an in-frame variant in the last two spectrin repeats - the only variant class that causes DEE5. What is being modelled instead, and what does that cost?
HUMAN MODEL MISMATCH OPEN gap_no_model_carries_the_dee5_allele
Attached to
pathophysiology#Spectrin Heterodimer Aggregation pathophysiology#De Novo In-Frame SPTAN1 Variant in the Heterodimerization Repeats
The in vivo evidence for this disorder comes from two models, and neither carries the disease allele. The conditional knockout deletes alpha-II spectrin outright, so it cannot aggregate and cannot exert a dominant-negative effect - it shows what the protein is required for, not what the mutant protein does. The R1098Q mouse is genuinely dominant-negative but sits in repeat 10 rather than the heterodimer nucleation site, and produces progressive ataxia with stress-induced seizures, which resembles the milder human SPTAN1 phenotypes rather than West syndrome. The source that describes the R1098Q model states the underlying problem plainly: modelling these encephalopathies has been difficult because heterozygous nulls show nothing and no stable transgenic line carrying a human missense variant exists. The practical cost is that the causal step from aggregation to seizures has never been tested in an animal that actually aggregates the relevant complex, and patient-derived neurons - which do carry the allele - cannot supply a network or behavioural readout. This is a mismatch in what the models can address, not evidence that the mechanism is wrong.
Proposed experiments
Knock-in mouse carrying a human DEE5 heterodimerization-repeat allele
exp_knockin_heterodimerization_repeat_allele
Generate a knock-in mouse carrying one of the recurrent in-frame deletions or duplications at the alpha/beta heterodimer nucleation site, and characterise spectrin aggregation, AIS integrity, inhibitory innervation, EEG and seizure phenotype. This is the single experiment that would let the step from aggregation to seizure be tested in vivo, and it would also test whether the raised firing threshold seen in vitro holds in an intact circuit.
Show evidence (2 references)
PMID:36831804 SUPPORT Model Organism
"Modeling human SPTAN1 encephalopathies in laboratory animals has been challenging partially because no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice nor stable transgenic lines of mice mimicking missense human SPTAN1 mutations have been created to date."
States both halves of the modelling gap in one sentence - nulls are silent, and no missense line exists.
PMID:25631096 SUPPORT Human Clinical
"Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
Defines the allele class that would have to be modelled, and that none of the current models carries.
Cerebral hypomyelination is a diagnostic hallmark of DEE5, but alpha-II spectrin is a neuronal cytoskeletal protein. Is the hypomyelination a direct consequence of spectrin loss in oligodendrocytes, a non-cell-autonomous consequence of abnormal axons, or secondary to the epileptic encephalopathy itself?
KNOWLEDGE GAP OPEN gap_which_arm_causes_the_hypomyelination
Attached to
pathophysiology#Cerebral Hypomyelination pathophysiology#Disrupted Dendritic and Axonal Development
Hypomyelination is one of the features that made SPTAN1 a candidate gene in the first place - it was picked out partly because alpha-II spectrin is essential for proper myelination in zebrafish - so it is not an incidental finding. But the mechanism curated in the rest of this entry is neuronal: aggregation, axon initial segment disruption, inhibitory synapse loss. Nothing in the verified sources measures spectrin function in oligodendrocytes or asks whether myelination recovers when axonal development is rescued. The three candidate routes make different predictions and would support different interpretations of the MRI hallmark, and the entry deliberately places hypomyelination as a parallel arm rather than downstream of any one of them, because choosing would assert more than the evidence carries.
Proposed experiments
Oligodendrocyte-restricted versus neuron-restricted Sptan1 deletion
exp_conditional_oligodendrocyte_sptan1_deletion
Compare myelin content and oligodendrocyte maturation between mice with Sptan1 deleted only in oligodendrocytes and mice with it deleted only in neurons. Hypomyelination in the oligodendrocyte-restricted line would establish a cell-autonomous glial requirement; hypomyelination only in the neuron-restricted line would establish the non-cell-autonomous axonal route, as has been shown for other neuronal genes with myelin phenotypes.
Show evidence (2 references)
PMID:20493457 SUPPORT Human Clinical
"SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebrafish, turned out to be deleted."
The myelination link that motivated the gene's identification, and which remains unresolved as to cell type in the human disease.
PMID:25631096 SUPPORT Human Clinical
"Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
Establishes hypomyelination as a diagnostic hallmark, which is why its mechanism matters rather than being a detail.
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Pathophysiology

14
De Novo In-Frame SPTAN1 Variant in the Heterodimerization Repeats
An in-frame deletion or duplication in the last two spectrin repeats of the C-terminal region, the site at which alpha/beta spectrin heterodimer nucleation begins. Position and variant type are both load-bearing here: only in-frame changes in this region produce the severe phenotype, which is why this node names the region rather than simply recording "a SPTAN1 variant".
Downstream
Thermolabile Alpha/Beta Spectrin Heterodimers Mutant alpha-II still assembles with beta-II spectrin, but the resulting heterodimer is unstable.
Show evidence (2 references)
PMID:20493457 SUPPORT Human Clinical
"In two subjects, an in-frame 3 bp deletion and a 6 bp duplication in SPTAN1 were found at the initial nucleation site of the alpha/beta spectrin heterodimer."
Locates the original variants precisely at the heterodimer nucleation site.
PMID:25631096 SUPPORT Human Clinical
"Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
States the region- and type-specificity that makes this node's framing necessary rather than pedantic.
Thermolabile Alpha/Beta Spectrin Heterodimers
Mutant and wild-type alpha-II spectrin both assemble heterodimers with beta-II spectrin, but the mutant heterodimers are thermolabile. This is a distinct node from the aggregation it leads to, and the distinction matters: assembly is not blocked, so the defect is in the stability of a complex that does form, not in failure to form one.
spectrin binding GO:0030507 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves abnormal spectrin binding (GO:0030507). GO:0030507 is a molecular function from the Gene Ontology. ⚠ ABNORMAL
Downstream
Spectrin Heterodimer Aggregation Unstable heterodimers accumulate as aggregates.
Show evidence (1 reference)
PMID:20493457 SUPPORT In Vitro
"Recombinant mutant (mut) and wild-type (WT) alpha-II spectrin could assemble heterodimers with beta-II spectrin, but alpha-II (mut)/beta-II spectrin heterodimers were thermolabile compared with the alpha-II (WT)/beta-II heterodimers."
The biophysical measurement, and the explicit statement that assembly itself still occurs.
Spectrin Heterodimer Aggregation
Mutant heterodimers aggregate in neurons and in patient-derived cells. This is the dominant-negative step: the mutant product does not merely fail, it captures partner subunits into aggregates, which is why one mutant allele is worse than one absent allele.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
spectrin GO:0008091 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves abnormal spectrin (GO:0008091). GO:0008091 is a cellular component from the Gene Ontology.
Experimental models
DEE5 patient-derived iPSC neurons IPSC DERIVED MODEL Shows the defining aggregation phenotype in human neurons at the patient genotype, which neither the null mouse nor the R1098Q mouse can do.
Animal models
Sptan1 conditional CNS knockout mouse Mouse fails to recapitulate A null cannot aggregate. This model deletes the protein, so it cannot reproduce the dominant-negative sequestration that defines the human mechanism, and any phenotype it shows is evidence about requirement rather than about aggregation.
Downstream
Axon Initial Segment Disruption Aggregates disrupt the periodic submembranous lattice at the axon initial segment.
Reduced Inhibitory Innervation Inhibitory innervation falls when alpha-II spectrin function is lost, by a route that has not been mapped.
Disrupted Dendritic and Axonal Development Neuronal process development is altered in the same systems.
Show evidence (2 references)
PMID:20493457 SUPPORT In Vitro
"Transient expression in mouse cortical neurons revealed aggregation of alpha-II (mut)/beta-II and alpha-II (mut)/beta-III spectrin heterodimers, which was also observed in lymphoblastoid cells from two subjects with in-frame mutations."
Shows aggregation in both a heterologous neuronal system and in cells taken from affected individuals, which is what makes it more than an overexpression artefact.
PMID:29337302 SUPPORT In Vitro
"Additionally, patient-derived neurons displayed aggregation of spectrin complexes."
Independent confirmation in patient-derived neurons rather than transfected cells.
Axon Initial Segment Disruption
Alpha-II spectrin partners with beta-IV spectrin to form the periodic cytoskeleton of the axon initial segment. Aggregation disrupts that lattice and, with it, the clustering of ankyrin-G and voltage-gated sodium channels that depends on it.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
axon initial segment GO:0043194 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves abnormal axon initial segment (GO:0043194). GO:0043194 is a cellular component from the Gene Ontology.
Animal models
Sptan1 conditional CNS knockout mouse Mouse recapitulates Establishes that alpha-II spectrin is required for axon initial segment assembly, which is the structural premise the human aggregation mechanism acts on.
Downstream
Elevated Action Potential Threshold Loss of sodium-channel clustering at the initial segment raises the threshold for firing in the affected neuron.
Show evidence (2 references)
PMID:29038240 SUPPORT Model Organism
"we show that αII and βIV spectrin interact and form a periodic AIS cytoskeleton"
Establishes that alpha-II spectrin is a structural component of the axon initial segment, which is the basis for its disruption here.
PMID:20493457 SUPPORT In Vitro
"Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
Ties the clustering failure directly to the aggregates, and reports the excitability consequence.
Elevated Action Potential Threshold
Neurons bearing spectrin aggregates fire less readily, not more. This node is curated in the direction the measurement actually went, which is opposite to what an epilepsy entry would naively predict; the discussion attached to it addresses how a disorder of reduced single-neuron excitability produces seizures.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
Show evidence (1 reference)
PMID:20493457 SUPPORT In Vitro
"Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
The threshold measurement, quoted in its own right because the direction is the point.
Reduced Inhibitory Innervation
Inhibitory innervation decreases after alpha-II spectrin loss. This is the arm that plausibly reconciles the seizures with the elevated single-neuron threshold above, by removing inhibition at network level rather than by making individual neurons more excitable.
GABAergic neuron CL:0000617 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves GABAergic neuron (CL:0000617). CL:0000617 is a cell type from the Cell Ontology.
inhibitory synapse assembly GO:1904862 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased inhibitory synapse assembly (GO:1904862). GO:1904862 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Cortical Network Disinhibition Fewer inhibitory inputs leave cortical networks disinhibited.
Show evidence (1 reference)
PMID:29337302 SUPPORT Model Organism
"CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
Reports the inhibitory-innervation deficit alongside the AIS loss in the same in vivo manipulation.
Disrupted Dendritic and Axonal Development
Dendritic and axonal development is altered, separately from the axon initial segment defect. Kept as its own node because the same experiments report it alongside, not as part of, AIS loss.
regulation of neuron projection development GO:0010975 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal regulation of neuron projection development (GO:0010975). GO:0010975 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Disrupted Cortical Lamination Abnormal process development plausibly contributes to the lamination defect seen on loss of alpha-II spectrin.
Show evidence (1 reference)
PMID:29337302 SUPPORT Model Organism
"CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
Names altered dendritic and axonal development as a distinct finding in the same experiment.
Disrupted Cortical Lamination
Cortical layering is disrupted where alpha-II spectrin is absent - a developmental malformation arm distinct from the synaptic and excitability arms.
cerebral cortex neuron differentiation GO:0021895 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal cerebral cortex neuron differentiation (GO:0021895). GO:0021895 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Animal models
Sptan1 conditional CNS knockout mouse Mouse recapitulates Reproduces the cortical developmental defect, and pairs it with seizures and neurodegeneration in the same animals.
Show evidence (1 reference)
PMID:29038240 SUPPORT Model Organism
"αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
Reports disrupted cortical lamination in the conditional knockout.
Cortical Network Disinhibition
The net shift of cortical circuits toward excitation, driven here by loss of inhibitory innervation rather than by increased intrinsic excitability.
Downstream
Infantile Spasms with Hypsarrhythmia A disinhibited immature cortex generates the presenting epilepsy.
Show evidence (1 reference)
PMID:29337302 SUPPORT Model Organism
"CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
Typed PARTIAL: the decreased inhibitory innervation is measured, but the resulting network-level disinhibition is inferred from it rather than recorded directly.
Infantile Spasms with Hypsarrhythmia
West syndrome - epileptic spasms with a hypsarrhythmic EEG - is the presenting epilepsy phenotype of DEE5.
Animal models
Spna2 R1098Q dominant-negative mouse Mouse partially recapitulates Heterozygous R1098Q mice have seizure episodes, so a dominant-negative alpha-II spectrin allele is sufficient to produce seizures in vivo. The seizures are stress-induced and appear alongside progressive ataxia and memory impairment.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Names hypsarrhythmic epileptic encephalopathy as the leading clinical feature.
Cerebral Hypomyelination
Severe cerebral hypomyelination, one of the imaging hallmarks. Curated as a parallel arm rather than downstream of the seizures, because it was part of the phenotype that originally identified the gene and alpha-II spectrin is independently required for myelination.
myelination GO:0042552 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased myelination (GO:0042552). GO:0042552 is a biological process from the Gene Ontology. ↓ DECREASED
Show evidence (1 reference)
PMID:20493457 SUPPORT Human Clinical
"SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebrafish, turned out to be deleted."
Records both the gene's myelination role and the reason it was implicated in a hypomyelinating phenotype.
Progressive Brainstem and Cerebellar Atrophy
Brainstem and cerebellar atrophy on MRI, together with cerebral hypomyelination, are described as specific hallmarks of this condition - which is what makes the imaging discriminating rather than merely abnormal.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
States the imaging hallmarks and their specificity.
Widespread Neurodegeneration
Neurodegeneration follows loss of alpha-II spectrin in the conditional knockout, a degenerative arm distinct from the developmental malformation arm above.
Show evidence (1 reference)
PMID:29038240 SUPPORT Model Organism
"αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
Reports widespread neurodegeneration alongside the developmental defects.
Profound Developmental Impairment
Severe intellectual disability with spastic quadriplegia, acquired microcephaly and absent visual attention. Multiple upstream arms converge here and the published data do not separate their contributions.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Enumerates the developmental and motor features of the severe phenotype.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for SPTAN1-Related Developmental and Epileptic Encephalopathy 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
Eye 1
Visual impairment HP:0000505 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Visual impairment (HP:0000505). HP:0000505 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
No visual attention is named among the major features.
Nervous System 5
Hypsarrhythmia HP:0002521 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypsarrhythmia (HP:0002521). HP:0002521 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Hypsarrhythmia is named directly in the list of major features.
Intellectual disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249), qualified as severity severe. HP:0001249 is a phenotype from the Human Phenotype Ontology.
Severity: SEVERE
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Severe intellectual disability is named, which supports both the phenotype and its severity qualifier.
Cerebral hypomyelination HP:0006808 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebral hypomyelination (HP:0006808). HP:0006808 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
Named as a specific hallmark.
Cerebellar atrophy HP:0001272 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebellar atrophy (HP:0001272). HP:0001272 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
Cerebellar atrophy is named as a specific hallmark.
Hypoplasia of the corpus callosum HP:0002079 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoplasia of the corpus callosum (HP:0002079). HP:0002079 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:36331550 SUPPORT Human Clinical
"Cerebellar atrophy, delayed myelination, thin corpus callosum"
The imaging findings recorded for an affected individual in this cohort. No frequency band is asserted: this is a per-patient imaging entry in a table, not a cohort proportion.
Other 3
Infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Infantile spasms (HP:0012469), qualified as infantile onset. HP:0012469 is a phenotype from the Human Phenotype Ontology.
Onset: INFANTILE
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Epileptic encephalopathy with hypsarrhythmia is named as a major feature. The band is VERY_FREQUENT rather than OBLIGATE because the source says "major clinical features", not that every patient has them.
Spastic tetraplegia HP:0002510 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spastic tetraplegia (HP:0002510). HP:0002510 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Spastic quadriplegia is named among the major features.
Progressive microcephaly HP:0000253 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Progressive microcephaly (HP:0000253). HP:0000253 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
The source specifies acquired microcephaly, which is why the progressive term is used rather than plain microcephaly.
🧬

Genetic Associations

1
SPTAN1 (De novo in-frame deletions and duplications in the last two C-terminal spectrin repeats of SPTAN1 cause DEE5 by a dominant-negative mechanism.)
Gene: SPTAN1 hgnc:11273 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SPTAN1 (hgnc:11273). hgnc:11273 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (6 references)
PMID:25631096 SUPPORT Human Clinical
"Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
The region- and type-specificity claim, stated in the source's own restrictive language.
PMID:25631096 SUPPORT Human Clinical
"The last two spectrin repeats are required for α/β spectrin heterodimer associations and the mutations can alter heterodimer formation between the two spectrins."
Explains why that region specifically matters, which is what turns a positional correlation into a mechanism.
PMID:36331550 SUPPORT Human Clinical
"A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures."
Quantifies the milder end of the allelic spectrum, which is the reason this entry is scoped to the in-frame heterodimerization-domain phenotype.
+ 3 more references
💊

Medical Actions

2
Antiseizure 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
Symptomatic management of the epileptic encephalopathy. No disease-modifying therapy exists, and this entry makes no efficacy claim for any specific agent, because the cited sources characterise the syndrome rather than compare treatments.
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
Offered given de novo dominant inheritance, with recurrence risk limited to gonadal mosaicism. Counselling in this disorder additionally has to convey that a SPTAN1 variant alone does not predict this phenotype, since other variant classes in the same gene cause much milder disease.
Show evidence (1 reference)
PMID:36331550 SUPPORT Human Clinical
"A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures."
Shows that a third of identified SPTAN1 variant carriers have a substantially different and milder disorder, which is the fact counselling has to convey.
🔬

Diagnosis

3
Molecular Genetic Testing for a SPTAN1 Variant
Diagnosis rests on identifying a de novo SPTAN1 variant and, critically, on locating it: only in-frame changes in the last two spectrin repeats predict this severe phenotype, so variant position is part of the diagnostic interpretation rather than a downstream detail. Exome or genome sequencing is the route, with developmental and epileptic encephalopathy gene panels as an alternative.
Whole Exome Sequencing NCIT:C101295 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:25631096 SUPPORT Human Clinical
"It is important that this syndrome is recognized by pediatric neurologists to enable proper diagnostic work-up for patients."
The source's argument for recognition and diagnostic work-up, which belongs here rather than against a treatment claim.
PMID:25631096 SUPPORT Human Clinical
"Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
Why variant position, not merely variant presence, is what the diagnosis turns on.
Brain MRI
Imaging is unusually discriminating here: brainstem and cerebellar atrophy with cerebral hypomyelination are described as specific hallmarks of this condition, which is a stronger claim than the nonspecific findings typical of the developmental and epileptic encephalopathies generally.
Magnetic Resonance Imaging NCIT:C16809 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
States both the imaging findings and their claimed specificity.
Electroencephalography
EEG demonstrates the hypsarrhythmia of West syndrome, which is the presenting electroclinical picture.
Electroencephalography NCIT:C38054 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:25631096 SUPPORT Human Clinical
"The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
Hypsarrhythmia is the EEG finding this modality demonstrates.
🧫

Experimental Models

1
DEE5 patient-derived iPSC neurons IPSC_DERIVED_MODEL
Neurons derived from patients carrying dominant-negative SPTAN1 variants - the one system that carries the actual human genotype rather than a null or a surrogate allele.
Pathograph links
Spectrin Heterodimer Aggregation recapitulates fidelity: high Shows the defining aggregation phenotype in human neurons at the patient genotype, which neither the null mouse nor the R1098Q mouse can do.
Limitations: iPSC neurons are developmentally immature and lack the circuit context in which the epilepsy arises, so they establish the cell-biological lesion rather than the network phenotype. The developmental defects were characterised alongside overexpression experiments in rodent neurons, so the patient-derived arm of that comparison is the smaller part of the evidence.
Readouts
Spectrin complex aggregation in patient neurons
Direction: INCREASED
Interpretation: Patient-derived neurons display aggregated spectrin complexes.
Show evidence (1 reference)
PMID:29337302 SUPPORT In Vitro
"Additionally, patient-derived neurons displayed aggregation of spectrin complexes."
The aggregation measurement behind this readout.
Show evidence (1 reference)
PMID:29337302 SUPPORT In Vitro
"Overexpression of human EIEE5 mutant SPTAN1 in embryonic rat forebrain and mouse hippocampal neurons led to similar developmental defects that were also observed in EIEE5 patient-derived neurons."
Establishes that the patient-derived neurons reproduce the developmental defects seen with mutant overexpression, which is what makes them informative.
🐁

Animal Models

2
Sptan1 conditional CNS knockout mouse
Complete CNS deletion of alpha-II spectrin. Supplies the structural and developmental arms of this entry. Note the deliberate mismatch of mechanism: this is a null, whereas human DEE5 is dominant-negative, which is why its relationship to the aggregation node is typed as a failure to recapitulate.
Species
Mouse
Genotype
Sptan1 f/f with CNS-specific Cre-mediated deletion
Publication
PMID:29038240
Pathograph links
Axon Initial Segment Disruption recapitulates fidelity: moderate Establishes that alpha-II spectrin is required for axon initial segment assembly, which is the structural premise the human aggregation mechanism acts on.
Limitations: A complete deletion removes the protein rather than producing an aggregating mutant, so it shows what the AIS needs alpha-II spectrin for, not how the human variant disrupts it. The mice die before one month, far short of the human disease course.
Readouts
Axon initial segment integrity
Direction: ABOLISHED
Interpretation: The AIS is disrupted, alongside profound reductions in all beta spectrins.
Show evidence (1 reference)
PMID:29038240 SUPPORT Model Organism
"found that loss of αII spectrin causes profound reductions in all β spectrins"
The subunit-loss measurement behind this readout.
Show evidence (1 reference)
PMID:29038240 SUPPORT Model Organism
"Using a new αII spectrin conditional knock-out mouse, we show that αII spectrin is required for AIS assembly, neuronal excitability, cortical lamination, and to protect against neurodegeneration."
States what this model establishes, which is the requirement rather than the disease mechanism.
Disrupted Cortical Lamination recapitulates fidelity: moderate Reproduces the cortical developmental defect, and pairs it with seizures and neurodegeneration in the same animals.
Limitations: Same null-versus-dominant-negative caveat; and because the deletion is CNS-wide from development, the model cannot separate a cell-autonomous lamination defect from a consequence of widespread degeneration.
Readouts
Cortical layering and neurodegeneration
Direction: ALTERED
Interpretation: Cortical lamination is disrupted, with seizures and widespread neurodegeneration in the same animals.
Show evidence (1 reference)
PMID:29038240 SUPPORT Model Organism
"αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
The combined phenotype measurement behind this readout.
Spectrin Heterodimer Aggregation fails to recapitulate fidelity: low A null cannot aggregate. This model deletes the protein, so it cannot reproduce the dominant-negative sequestration that defines the human mechanism, and any phenotype it shows is evidence about requirement rather than about aggregation.
Limitations: This is a definitional limitation rather than an experimental shortfall, and it is the reason the entry does not treat the conditional knockout as a model of DEE5 as such. The point is sharpened by the observation that heterozygous null mice - the closest null analogue of a heterozygous human patient - have no phenotype at all, so gene dose alone does not reproduce the disease.
Readouts
Absence of a haploinsufficiency phenotype in heterozygous null mice
Direction: UNCHANGED
Interpretation: Losing one copy produces no disease phenotype, so the human heterozygous phenotype cannot be a dose effect.
Show evidence (1 reference)
PMID:36831804 SUPPORT Model Organism
"no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice"
The negative result behind this readout, and the basis for typing this link as a failure to recapitulate.
Show evidence (1 reference)
PMID:36831804 SUPPORT Model Organism
"Modeling human SPTAN1 encephalopathies in laboratory animals has been challenging partially because no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice nor stable transgenic lines of mice mimicking missense human SPTAN1 mutations have been created to date."
States the modelling problem directly - neither dose reduction nor a transgenic missense line reproduces the human disease.
Spna2 R1098Q dominant-negative mouse
A spontaneous point mutation affecting alpha-II spectrin scaffold stability, and the closest available in vivo analogue of a human dominant-negative allele - though it sits in repeat 10 rather than the last two repeats that cause DEE5.
Species
Mouse
Genotype
Spna2 R1098Q heterozygous point mutation in spectrin repeat 10
Publication
PMID:36831804
Pathograph links
Infantile Spasms with Hypsarrhythmia partially recapitulates fidelity: low Heterozygous R1098Q mice have seizure episodes, so a dominant-negative alpha-II spectrin allele is sufficient to produce seizures in vivo. The seizures are stress-induced and appear alongside progressive ataxia and memory impairment.
Limitations: The variant is in repeat 10, not the heterodimerization repeats that cause DEE5, and the phenotype it produces - progressive ataxia with stress-induced seizures and memory impairment - resembles the milder ataxia end of the human SPTAN1 spectrum more than infantile spasms with hypsarrhythmia. It therefore supports the dominant-negative principle without modelling this disease's epilepsy syndrome.
Readouts
Stress-induced seizure episodes in heterozygous mice
Direction: INCREASED
Interpretation: Long-lasting seizure episodes occur in heterozygous animals carrying a dominant-negative allele.
Show evidence (1 reference)
PMID:36831804 SUPPORT Model Organism
"We also document stress-induced, long-lasting seizure episodes of R1098Q mice and their poor performance in novel object recognition memory tests."
The seizure and memory measurements behind this readout.
Show evidence (1 reference)
PMID:36831804 SUPPORT Model Organism
"Overall, we propose that the complexity of neuropathology-related phenotypes presented by the R1098Q mice recapitulates a number of symptoms observed in human patients carrying SPTAN1 mutations affecting α-II scaffold stability."
The authors scope their own claim to variants affecting scaffold stability, which is the milder arm rather than the DEE5 heterodimerization arm.
{ }

Source YAML

click to show 
name: SPTAN1-Related Developmental and Epileptic Encephalopathy
creation_date: "2026-08-19T19:10:00Z"
category: Mendelian
synonyms:
- Developmental and epileptic encephalopathy 5
- DEE5
- EIEE5
- SPTAN1 encephalopathy
- Early infantile epileptic encephalopathy 5
description: >-
  SPTAN1-related developmental and epileptic encephalopathy (DEE5) is caused by de
  novo in-frame deletions and duplications in the last two spectrin repeats of
  alpha-II spectrin, the region required for alpha/beta spectrin heterodimer
  nucleation. The mutant protein still binds beta-spectrin but forms thermolabile
  heterodimers that aggregate, sequestering wild-type subunits - a dominant-negative
  mechanism rather than haploinsufficiency, which is why the position and type of
  variant, not merely its presence, determines whether a person develops this severe
  phenotype or one of the much milder SPTAN1 disorders. Aggregates disrupt the axon
  initial segment and its ankyrin-G and sodium-channel clustering, and inhibitory
  innervation is reduced. Clinically this produces West syndrome with hypsarrhythmia,
  cerebral hypomyelination, spastic quadriplegia, acquired microcephaly and profound
  developmental impairment, with brainstem and cerebellar atrophy as imaging
  hallmarks.
disease_term:
  preferred_term: developmental and epileptic encephalopathy, 5
  term:
    id: MONDO:0013277
    label: developmental and epileptic encephalopathy, 5
parents:
- Epilepsy
- Neurological Disease
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Heterozygous and de novo. The mechanism is dominant-negative rather than
    haploinsufficient, which is a stronger statement than "dominant" alone and is
    evidenced by heterozygous null mice being unaffected.
  evidence:
  - reference: PMID:36831804
    reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice"
    explanation: >-
      Losing one copy is not sufficient to cause disease in mice, which is the
      observation that separates a dominant-negative mechanism from a dose effect.

pathophysiology:
- name: De Novo In-Frame SPTAN1 Variant in the Heterodimerization Repeats
  biological_scale: MOLECULAR
  description: >-
    An in-frame deletion or duplication in the last two spectrin repeats of the
    C-terminal region, the site at which alpha/beta spectrin heterodimer nucleation
    begins. Position and variant type are both load-bearing here: only in-frame
    changes in this region produce the severe phenotype, which is why this node names
    the region rather than simply recording "a SPTAN1 variant".
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In two subjects, an in-frame 3 bp deletion and a 6 bp duplication in SPTAN1 were found at the initial nucleation site of the alpha/beta spectrin heterodimer."
    explanation: >-
      Locates the original variants precisely at the heterodimer nucleation site.
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
    explanation: >-
      States the region- and type-specificity that makes this node's framing necessary
      rather than pedantic.
  downstream:
  - target: Thermolabile Alpha/Beta Spectrin Heterodimers
    causal_link_type: DIRECT
    description: >-
      Mutant alpha-II still assembles with beta-II spectrin, but the resulting
      heterodimer is unstable.

- name: Thermolabile Alpha/Beta Spectrin Heterodimers
  biological_scale: MOLECULAR
  description: >-
    Mutant and wild-type alpha-II spectrin both assemble heterodimers with beta-II
    spectrin, but the mutant heterodimers are thermolabile. This is a distinct node
    from the aggregation it leads to, and the distinction matters: assembly is not
    blocked, so the defect is in the stability of a complex that does form, not in
    failure to form one.
  molecular_functions:
  - preferred_term: spectrin binding
    term:
      id: GO:0030507
      label: spectrin binding
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Recombinant mutant (mut) and wild-type (WT) alpha-II spectrin could assemble heterodimers with beta-II spectrin, but alpha-II (mut)/beta-II spectrin heterodimers were thermolabile compared with the alpha-II (WT)/beta-II heterodimers."
    explanation: >-
      The biophysical measurement, and the explicit statement that assembly itself
      still occurs.
  downstream:
  - target: Spectrin Heterodimer Aggregation
    causal_link_type: DIRECT
    description: >-
      Unstable heterodimers accumulate as aggregates.

- name: Spectrin Heterodimer Aggregation
  biological_scale: CELLULAR
  description: >-
    Mutant heterodimers aggregate in neurons and in patient-derived cells. This is the
    dominant-negative step: the mutant product does not merely fail, it captures
    partner subunits into aggregates, which is why one mutant allele is worse than one
    absent allele.
  cellular_components:
  - preferred_term: spectrin
    term:
      id: GO:0008091
      label: spectrin
    modifier: ABNORMAL
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Transient expression in mouse cortical neurons revealed aggregation of alpha-II (mut)/beta-II and alpha-II (mut)/beta-III spectrin heterodimers, which was also observed in lymphoblastoid cells from two subjects with in-frame mutations."
    explanation: >-
      Shows aggregation in both a heterologous neuronal system and in cells taken from
      affected individuals, which is what makes it more than an overexpression
      artefact.
  - reference: PMID:29337302
    reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Additionally, patient-derived neurons displayed aggregation of spectrin complexes."
    explanation: >-
      Independent confirmation in patient-derived neurons rather than transfected
      cells.
  downstream:
  - target: Axon Initial Segment Disruption
    causal_link_type: DIRECT
    description: >-
      Aggregates disrupt the periodic submembranous lattice at the axon initial
      segment.
  - target: Reduced Inhibitory Innervation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Inhibitory innervation falls when alpha-II spectrin function is lost, by a route
      that has not been mapped.
  - target: Disrupted Dendritic and Axonal Development
    causal_link_type: DIRECT
    description: >-
      Neuronal process development is altered in the same systems.

- name: Axon Initial Segment Disruption
  biological_scale: CELLULAR
  description: >-
    Alpha-II spectrin partners with beta-IV spectrin to form the periodic cytoskeleton
    of the axon initial segment. Aggregation disrupts that lattice and, with it, the
    clustering of ankyrin-G and voltage-gated sodium channels that depends on it.
  cellular_components:
  - preferred_term: axon initial segment
    term:
      id: GO:0043194
      label: axon initial segment
    modifier: ABNORMAL
  cell_types:
  - preferred_term: pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  evidence:
  - reference: PMID:29038240
    reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we show that αII and βIV spectrin interact and form a periodic AIS cytoskeleton"
    explanation: >-
      Establishes that alpha-II spectrin is a structural component of the axon initial
      segment, which is the basis for its disruption here.
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
    explanation: >-
      Ties the clustering failure directly to the aggregates, and reports the
      excitability consequence.
  downstream:
  - target: Elevated Action Potential Threshold
    causal_link_type: DIRECT
    description: >-
      Loss of sodium-channel clustering at the initial segment raises the threshold for
      firing in the affected neuron.

- name: Elevated Action Potential Threshold
  biological_scale: CELLULAR
  description: >-
    Neurons bearing spectrin aggregates fire less readily, not more. This node is
    curated in the direction the measurement actually went, which is opposite to what
    an epilepsy entry would naively predict; the discussion attached to it addresses
    how a disorder of reduced single-neuron excitability produces seizures.
  cell_types:
  - preferred_term: pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
    explanation: >-
      The threshold measurement, quoted in its own right because the direction is the
      point.

- name: Reduced Inhibitory Innervation
  biological_scale: TISSUE
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Ion Channel and Synaptic Dysfunction"
  description: >-
    Inhibitory innervation decreases after alpha-II spectrin loss. This is the arm
    that plausibly reconciles the seizures with the elevated single-neuron threshold
    above, by removing inhibition at network level rather than by making individual
    neurons more excitable.
  cell_types:
  - preferred_term: GABAergic neuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  biological_processes:
  - preferred_term: inhibitory synapse assembly
    term:
      id: GO:1904862
      label: inhibitory synapse assembly
    modifier: DECREASED
  evidence:
  - reference: PMID:29337302
    reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
    explanation: >-
      Reports the inhibitory-innervation deficit alongside the AIS loss in the same
      in vivo manipulation.
  downstream:
  - target: Cortical Network Disinhibition
    causal_link_type: DIRECT
    description: >-
      Fewer inhibitory inputs leave cortical networks disinhibited.

- name: Disrupted Dendritic and Axonal Development
  biological_scale: CELLULAR
  description: >-
    Dendritic and axonal development is altered, separately from the axon initial
    segment defect. Kept as its own node because the same experiments report it
    alongside, not as part of, AIS loss.
  biological_processes:
  - preferred_term: regulation of neuron projection development
    term:
      id: GO:0010975
      label: regulation of neuron projection development
    modifier: ABNORMAL
  evidence:
  - reference: PMID:29337302
    reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
    explanation: >-
      Names altered dendritic and axonal development as a distinct finding in the same
      experiment.
  downstream:
  - target: Disrupted Cortical Lamination
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Abnormal process development plausibly contributes to the lamination defect seen
      on loss of alpha-II spectrin.

- name: Disrupted Cortical Lamination
  biological_scale: TISSUE
  description: >-
    Cortical layering is disrupted where alpha-II spectrin is absent - a developmental
    malformation arm distinct from the synaptic and excitability arms.
  biological_processes:
  - preferred_term: cerebral cortex neuron differentiation
    term:
      id: GO:0021895
      label: cerebral cortex neuron differentiation
    modifier: ABNORMAL
  evidence:
  - reference: PMID:29038240
    reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
    explanation: >-
      Reports disrupted cortical lamination in the conditional knockout.

- name: Cortical Network Disinhibition
  biological_scale: TISSUE
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance"
  description: >-
    The net shift of cortical circuits toward excitation, driven here by loss of
    inhibitory innervation rather than by increased intrinsic excitability.
  evidence:
  - reference: PMID:29337302
    reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
    explanation: >-
      Typed PARTIAL: the decreased inhibitory innervation is measured, but the
      resulting network-level disinhibition is inferred from it rather than recorded
      directly.
  downstream:
  - target: Infantile Spasms with Hypsarrhythmia
    causal_link_type: DIRECT
    description: >-
      A disinhibited immature cortex generates the presenting epilepsy.

- name: Infantile Spasms with Hypsarrhythmia
  biological_scale: ORGANISM
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Recurrent Unprovoked Seizures"
  description: >-
    West syndrome - epileptic spasms with a hypsarrhythmic EEG - is the presenting
    epilepsy phenotype of DEE5.
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Names hypsarrhythmic epileptic encephalopathy as the leading clinical feature.

- name: Cerebral Hypomyelination
  biological_scale: TISSUE
  description: >-
    Severe cerebral hypomyelination, one of the imaging hallmarks. Curated as a
    parallel arm rather than downstream of the seizures, because it was part of the
    phenotype that originally identified the gene and alpha-II spectrin is
    independently required for myelination.
  biological_processes:
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
    modifier: DECREASED
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebrafish, turned out to be deleted."
    explanation: >-
      Records both the gene's myelination role and the reason it was implicated in a
      hypomyelinating phenotype.

- name: Progressive Brainstem and Cerebellar Atrophy
  biological_scale: TISSUE
  description: >-
    Brainstem and cerebellar atrophy on MRI, together with cerebral hypomyelination,
    are described as specific hallmarks of this condition - which is what makes the
    imaging discriminating rather than merely abnormal.
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
    explanation: >-
      States the imaging hallmarks and their specificity.

- name: Widespread Neurodegeneration
  biological_scale: TISSUE
  description: >-
    Neurodegeneration follows loss of alpha-II spectrin in the conditional knockout, a
    degenerative arm distinct from the developmental malformation arm above.
  evidence:
  - reference: PMID:29038240
    reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
    explanation: >-
      Reports widespread neurodegeneration alongside the developmental defects.

- name: Profound Developmental Impairment
  biological_scale: ORGANISM
  description: >-
    Severe intellectual disability with spastic quadriplegia, acquired microcephaly
    and absent visual attention. Multiple upstream arms converge here and the
    published data do not separate their contributions.
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Enumerates the developmental and motor features of the severe phenotype.

phenotypes:
- category: Neurological
  name: Infantile spasms
  description: Epileptic spasms of West syndrome, with infantile onset.
  phenotype_term:
    preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
    onset:
      onset_category: INFANTILE
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Epileptic encephalopathy with hypsarrhythmia is named as a major feature. The
      band is VERY_FREQUENT rather than OBLIGATE because the source says "major
      clinical features", not that every patient has them.

- category: Neurological
  name: Hypsarrhythmia
  description: The EEG pattern accompanying the spasms.
  phenotype_term:
    preferred_term: Hypsarrhythmia
    term:
      id: HP:0002521
      label: Hypsarrhythmia
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Hypsarrhythmia is named directly in the list of major features.

- category: Neurological
  name: Spastic tetraplegia
  description: Spastic quadriplegia is a core motor feature.
  phenotype_term:
    preferred_term: Spastic tetraplegia
    term:
      id: HP:0002510
      label: Spastic tetraplegia
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Spastic quadriplegia is named among the major features.

- category: Neurological
  name: Progressive microcephaly
  description: >-
    Microcephaly is acquired rather than congenital, developing after birth.
  phenotype_term:
    preferred_term: Progressive microcephaly
    term:
      id: HP:0000253
      label: Progressive microcephaly
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      The source specifies acquired microcephaly, which is why the progressive term is
      used rather than plain microcephaly.

- category: Neurological
  name: Intellectual disability
  description: Severe intellectual disability.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
    severity: SEVERE
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Severe intellectual disability is named, which supports both the phenotype and
      its severity qualifier.

- category: Ophthalmological
  name: Visual impairment
  description: Absent visual attention.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      No visual attention is named among the major features.

- category: Neuroimaging
  name: Cerebral hypomyelination
  description: Severe cerebral hypomyelination, an imaging hallmark.
  phenotype_term:
    preferred_term: Cerebral hypomyelination
    term:
      id: HP:0006808
      label: Cerebral hypomyelination
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
    explanation: >-
      Named as a specific hallmark.

- category: Neuroimaging
  name: Cerebellar atrophy
  description: Cerebellar atrophy accompanies brainstem atrophy on MRI.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
    explanation: >-
      Cerebellar atrophy is named as a specific hallmark.

- category: Neuroimaging
  name: Hypoplasia of the corpus callosum
  description: >-
    A thin corpus callosum accompanies the hypomyelination and atrophy on MRI.
  phenotype_term:
    preferred_term: Hypoplasia of the corpus callosum
    term:
      id: HP:0002079
      label: Hypoplasia of the corpus callosum
  evidence:
  - reference: PMID:36331550
    reference_title: "Expanding SPTAN1 monoallelic variant associated disorders: From epileptic encephalopathy to pure spastic paraplegia and ataxia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cerebellar atrophy, delayed myelination, thin corpus callosum"
    explanation: >-
      The imaging findings recorded for an affected individual in this cohort. No
      frequency band is asserted: this is a per-patient imaging entry in a table, not
      a cohort proportion.

genetic:
- name: SPTAN1
  gene_term:
    preferred_term: SPTAN1
    term:
      id: hgnc:11273
      label: SPTAN1
  relationship_type: CAUSATIVE
  association: >-
    De novo in-frame deletions and duplications in the last two C-terminal spectrin
    repeats of SPTAN1 cause DEE5 by a dominant-negative mechanism.
  notes: >-
    The genotype-mechanism relationship is unusually well resolved for a developmental
    and epileptic encephalopathy, and it is not simply "variants in this gene cause
    this disease". Only in-frame changes in the last two spectrin repeats - the
    alpha/beta heterodimer nucleation site - produce the severe DEE5 phenotype, and
    they do so by dominant-negative aggregation rather than by reducing gene dose.
    Heterozygous null mice have no haploinsufficiency phenotype, which is the
    observation that separates the two mechanisms. Other SPTAN1 variant classes cause
    substantially milder disorders: a large sequencing study found statistically
    significant enrichment of rare damaging SPTAN1 variants in hereditary ataxia and
    hereditary spastic paraplegia families, with a third of the identified carriers
    presenting pure or complex HSP/ataxia rather than developmental delay and
    seizures. Curators extending this entry should therefore not treat "a SPTAN1
    variant" as sufficient for DEE5 - position and variant type carry the phenotype.
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
    explanation: >-
      The region- and type-specificity claim, stated in the source's own restrictive
      language.
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The last two spectrin repeats are required for α/β spectrin heterodimer associations and the mutations can alter heterodimer formation between the two spectrins."
    explanation: >-
      Explains why that region specifically matters, which is what turns a positional
      correlation into a mechanism.
  - reference: PMID:36331550
    reference_title: "Expanding SPTAN1 monoallelic variant associated disorders: From epileptic encephalopathy to pure spastic paraplegia and ataxia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures."
    explanation: >-
      Quantifies the milder end of the allelic spectrum, which is the reason this
      entry is scoped to the in-frame heterodimerization-domain phenotype.
  - reference: PMID:34590414
    reference_title: "Extending the clinical phenotype of SPTAN1: From DEE5 to migraine, epilepsy, and subependymal heterotopias without intellectual disability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we noted an excess of male versus female patients"
    explanation: >-
      A sex skew across reported SPTAN1 patients, more pronounced at the milder end.
      Recorded because it bears on variant interpretation rather than on the DEE5
      phenotype itself.
  - reference: PMID:34590414
    reference_title: "Extending the clinical phenotype of SPTAN1: From DEE5 to migraine, epilepsy, and subependymal heterotopias without intellectual disability."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Consequently, some protection factor might be suspected among female carriers"
    explanation: >-
      Typed PARTIAL because the authors offer this as a suspicion to be confirmed, not
      a finding; it is quoted for the caution it attaches to calling milder variants
      pathogenic.
  - reference: PMID:41370269
    reference_title: "Axon initial segment damage and hyperexcitability in a mutant mouse with increased calpain-dependent cleavage of αII-Spectrin."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "However, a clear genotype-phenotype relationship remains elusive."
    explanation: >-
      A 2025 statement that genotype-phenotype correlation across SPTAN1 as a whole
      is still unresolved - which is worth holding alongside the well-established
      correlation for this specific in-frame heterodimerization-repeat class.

animal_models:
- name: Sptan1 conditional CNS knockout mouse
  species: Mouse
  genotype: Sptan1 f/f with CNS-specific Cre-mediated deletion
  publication: PMID:29038240
  description: >-
    Complete CNS deletion of alpha-II spectrin. Supplies the structural and
    developmental arms of this entry. Note the deliberate mismatch of mechanism: this
    is a null, whereas human DEE5 is dominant-negative, which is why its relationship
    to the aggregation node is typed as a failure to recapitulate.
  modeled_mechanisms:
  - target: Axon Initial Segment Disruption
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Establishes that alpha-II spectrin is required for axon initial segment assembly,
      which is the structural premise the human aggregation mechanism acts on.
    limitations: >-
      A complete deletion removes the protein rather than producing an aggregating
      mutant, so it shows what the AIS needs alpha-II spectrin for, not how the human
      variant disrupts it. The mice die before one month, far short of the human
      disease course.
    readouts:
    - name: Axon initial segment integrity
      target: Axon Initial Segment Disruption
      direction: ABOLISHED
      interpretation: >-
        The AIS is disrupted, alongside profound reductions in all beta spectrins.
      evidence:
      - reference: PMID:29038240
        reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "found that loss of αII spectrin causes profound reductions in all β spectrins"
        explanation: The subunit-loss measurement behind this readout.
    evidence:
    - reference: PMID:29038240
      reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Using a new αII spectrin conditional knock-out mouse, we show that αII spectrin is required for AIS assembly, neuronal excitability, cortical lamination, and to protect against neurodegeneration."
      explanation: >-
        States what this model establishes, which is the requirement rather than the
        disease mechanism.
  - target: Disrupted Cortical Lamination
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the cortical developmental defect, and pairs it with seizures and
      neurodegeneration in the same animals.
    limitations: >-
      Same null-versus-dominant-negative caveat; and because the deletion is CNS-wide
      from development, the model cannot separate a cell-autonomous lamination defect
      from a consequence of widespread degeneration.
    readouts:
    - name: Cortical layering and neurodegeneration
      target: Disrupted Cortical Lamination
      direction: ALTERED
      interpretation: >-
        Cortical lamination is disrupted, with seizures and widespread
        neurodegeneration in the same animals.
      evidence:
      - reference: PMID:29038240
        reference_title: "αII Spectrin Forms a Periodic Cytoskeleton at the Axon Initial Segment and Is Required for Nervous System Function."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "αII spectrin-deficient mice die before 1 month of age and have disrupted AIS and many other neurological impairments including seizures, disrupted cortical lamination, and widespread neurodegeneration."
        explanation: The combined phenotype measurement behind this readout.
  - target: Spectrin Heterodimer Aggregation
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      A null cannot aggregate. This model deletes the protein, so it cannot reproduce
      the dominant-negative sequestration that defines the human mechanism, and any
      phenotype it shows is evidence about requirement rather than about aggregation.
    limitations: >-
      This is a definitional limitation rather than an experimental shortfall, and it
      is the reason the entry does not treat the conditional knockout as a model of
      DEE5 as such. The point is sharpened by the observation that heterozygous null
      mice - the closest null analogue of a heterozygous human patient - have no
      phenotype at all, so gene dose alone does not reproduce the disease.
    readouts:
    - name: Absence of a haploinsufficiency phenotype in heterozygous null mice
      target: Spectrin Heterodimer Aggregation
      direction: UNCHANGED
      interpretation: >-
        Losing one copy produces no disease phenotype, so the human heterozygous
        phenotype cannot be a dose effect.
      evidence:
      - reference: PMID:36831804
        reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice"
        explanation: >-
          The negative result behind this readout, and the basis for typing this link
          as a failure to recapitulate.
    evidence:
    - reference: PMID:36831804
      reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Modeling human SPTAN1 encephalopathies in laboratory animals has been challenging partially because no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice nor stable transgenic lines of mice mimicking missense human SPTAN1 mutations have been created to date."
      explanation: >-
        States the modelling problem directly - neither dose reduction nor a
        transgenic missense line reproduces the human disease.

- name: Spna2 R1098Q dominant-negative mouse
  species: Mouse
  genotype: Spna2 R1098Q heterozygous point mutation in spectrin repeat 10
  publication: PMID:36831804
  description: >-
    A spontaneous point mutation affecting alpha-II spectrin scaffold stability, and
    the closest available in vivo analogue of a human dominant-negative allele -
    though it sits in repeat 10 rather than the last two repeats that cause DEE5.
  modeled_mechanisms:
  - target: Infantile Spasms with Hypsarrhythmia
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Heterozygous R1098Q mice have seizure episodes, so a dominant-negative
      alpha-II spectrin allele is sufficient to produce seizures in vivo. The seizures
      are stress-induced and appear alongside progressive ataxia and memory
      impairment.
    limitations: >-
      The variant is in repeat 10, not the heterodimerization repeats that cause DEE5,
      and the phenotype it produces - progressive ataxia with stress-induced seizures
      and memory impairment - resembles the milder ataxia end of the human SPTAN1
      spectrum more than infantile spasms with hypsarrhythmia. It therefore supports
      the dominant-negative principle without modelling this disease's epilepsy
      syndrome.
    readouts:
    - name: Stress-induced seizure episodes in heterozygous mice
      target: Infantile Spasms with Hypsarrhythmia
      direction: INCREASED
      interpretation: >-
        Long-lasting seizure episodes occur in heterozygous animals carrying a
        dominant-negative allele.
      evidence:
      - reference: PMID:36831804
        reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "We also document stress-induced, long-lasting seizure episodes of R1098Q mice and their poor performance in novel object recognition memory tests."
        explanation: The seizure and memory measurements behind this readout.
    evidence:
    - reference: PMID:36831804
      reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Overall, we propose that the complexity of neuropathology-related phenotypes presented by the R1098Q mice recapitulates a number of symptoms observed in human patients carrying SPTAN1 mutations affecting α-II scaffold stability."
      explanation: >-
        The authors scope their own claim to variants affecting scaffold stability,
        which is the milder arm rather than the DEE5 heterodimerization arm.

experimental_models:
- name: DEE5 patient-derived iPSC neurons
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Neurons derived from patients carrying dominant-negative SPTAN1 variants - the one
    system that carries the actual human genotype rather than a null or a surrogate
    allele.
  modeled_mechanisms:
  - target: Spectrin Heterodimer Aggregation
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Shows the defining aggregation phenotype in human neurons at the patient
      genotype, which neither the null mouse nor the R1098Q mouse can do.
    limitations: >-
      iPSC neurons are developmentally immature and lack the circuit context in which
      the epilepsy arises, so they establish the cell-biological lesion rather than
      the network phenotype. The developmental defects were characterised alongside
      overexpression experiments in rodent neurons, so the patient-derived arm of that
      comparison is the smaller part of the evidence.
    readouts:
    - name: Spectrin complex aggregation in patient neurons
      target: Spectrin Heterodimer Aggregation
      direction: INCREASED
      interpretation: >-
        Patient-derived neurons display aggregated spectrin complexes.
      evidence:
      - reference: PMID:29337302
        reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Additionally, patient-derived neurons displayed aggregation of spectrin complexes."
        explanation: The aggregation measurement behind this readout.
    evidence:
    - reference: PMID:29337302
      reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Overexpression of human EIEE5 mutant SPTAN1 in embryonic rat forebrain and mouse hippocampal neurons led to similar developmental defects that were also observed in EIEE5 patient-derived neurons."
      explanation: >-
        Establishes that the patient-derived neurons reproduce the developmental
        defects seen with mutant overexpression, which is what makes them informative.

diagnosis:
- name: Molecular Genetic Testing for a SPTAN1 Variant
  description: >-
    Diagnosis rests on identifying a de novo SPTAN1 variant and, critically, on
    locating it: only in-frame changes in the last two spectrin repeats predict this
    severe phenotype, so variant position is part of the diagnostic interpretation
    rather than a downstream detail. Exome or genome sequencing is the route, with
    developmental and epileptic encephalopathy gene panels as an alternative.
  diagnosis_term:
    preferred_term: Whole Exome Sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is important that this syndrome is recognized by pediatric neurologists to enable proper diagnostic work-up for patients."
    explanation: >-
      The source's argument for recognition and diagnostic work-up, which belongs
      here rather than against a treatment claim.
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
    explanation: >-
      Why variant position, not merely variant presence, is what the diagnosis turns
      on.

- name: Brain MRI
  description: >-
    Imaging is unusually discriminating here: brainstem and cerebellar atrophy with
    cerebral hypomyelination are described as specific hallmarks of this condition,
    which is a stronger claim than the nonspecific findings typical of the
    developmental and epileptic encephalopathies generally.
  diagnosis_term:
    preferred_term: Magnetic Resonance Imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
    explanation: >-
      States both the imaging findings and their claimed specificity.

- name: Electroencephalography
  description: >-
    EEG demonstrates the hypsarrhythmia of West syndrome, which is the presenting
    electroclinical picture.
  diagnosis_term:
    preferred_term: Electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  evidence:
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability."
    explanation: >-
      Hypsarrhythmia is the EEG finding this modality demonstrates.

treatments:
- name: Antiseizure Medication
  description: >-
    Symptomatic management of the epileptic encephalopathy. No disease-modifying
    therapy exists, and this entry makes no efficacy claim for any specific agent,
    because the cited sources characterise the syndrome rather than compare
    treatments.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  notes: >-
    No evidence block is attached. None of the references cited by this entry states
    anything about antiseizure drug choice or response in DEE5, and rather than
    attach a snippet that does not support the claim, the treatment is described
    without evidence. Agents used first-line for infantile spasms generally - ACTH,
    vigabatrin, the ketogenic diet - are deliberately not bound as therapeutic_agent
    here: the deep-research report scopes them as broad infantile-spasms practice with
    response rates from general and mixed-etiology populations, not as SPTAN1 evidence,
    and binding them would import general epilepsy practice as though it were
    disease-specific. That gap is real and worth closing with a proper SPTAN1 treatment
    source rather than by inference.

- name: Genetic Counseling
  description: >-
    Offered given de novo dominant inheritance, with recurrence risk limited to
    gonadal mosaicism. Counselling in this disorder additionally has to convey that a
    SPTAN1 variant alone does not predict this phenotype, since other variant classes
    in the same gene cause much milder disease.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:36331550
    reference_title: "Expanding SPTAN1 monoallelic variant associated disorders: From epileptic encephalopathy to pure spastic paraplegia and ataxia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A total of 10 patients presented with pure or complex HSP/HA. The remaining 21 patients had developmental delay and seizures."
    explanation: >-
      Shows that a third of identified SPTAN1 variant carriers have a substantially
      different and milder disorder, which is the fact counselling has to convey.

discussions:
- discussion_id: controversy_seizures_despite_raised_firing_threshold
  prompt: >-
    Neurons carrying SPTAN1 aggregates have a raised action potential threshold - they
    fire less readily. How does a lesion that makes individual neurons harder to
    excite produce an infantile epileptic encephalopathy?
  kind: CONTROVERSY
  status: OPEN
  attaches_to:
  - pathophysiology#Elevated Action Potential Threshold
  - pathophysiology#Reduced Inhibitory Innervation
  - pathophysiology#Cortical Network Disinhibition
  rationale: >-
    The measured direction is the opposite of the naive expectation for an epilepsy
    gene, and the pathograph records it that way rather than quietly smoothing it out.
    Disrupted clustering of voltage-gated sodium channels at the axon initial segment
    raises the threshold for firing, so the primary cellular defect is reduced
    excitability. The leading reconciliation is that the network consequence inverts
    the cellular one: inhibitory innervation is also reduced, and if inhibitory
    interneurons are more affected than principal cells - or if the loss of inhibitory
    synapses outweighs the raised threshold in principal cells - the net cortical
    effect is disinhibition despite less excitable individual neurons. That account is
    plausible and consistent with everything measured, and it gains support from an
    intact-animal result: a mouse carrying a destabilising alpha-II spectrin variant
    shows fewer and structurally defective axon initial segments together with
    increased neuronal excitability and greater chemoconvulsant sensitivity, so at
    network level the sign is the opposite of the single-neuron threshold shift. That
    still does not settle it, because the variant sits in repeat 10 rather than the
    DEE5 heterodimerization repeats and the measurement is at network rather than
    cellular level - and no study has compared threshold shifts between interneurons
    and pyramidal cells in the same preparation, which is exactly the measurement that
    would decide it. Until then the entry keeps the raised threshold and the reduced
    inhibition as separate nodes rather than merging them into a single excitability
    claim, because merging them would hide the tension rather than resolve it.
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Clustering of ankyrinG and voltage-gated sodium channels at axon initial segment (AIS) was disturbed in relation to the aggregates, together with an elevated action potential threshold."
    explanation: >-
      The measurement that creates the puzzle: threshold goes up, not down.
  - reference: PMID:29337302
    reference_title: "Critical roles of αII spectrin in brain development and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation."
    explanation: >-
      The decreased inhibitory innervation that supplies the candidate resolution, in
      the same lesion.
  - reference: PMID:41370269
    reference_title: "Axon initial segment damage and hyperexcitability in a mutant mouse with increased calpain-dependent cleavage of αII-Spectrin."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our results show that R1098Q mutant mice display abnormal electroencephalographic activity, increased neuronal excitability, and heightened sensitivity to a chemoconvulsant."
    explanation: >-
      Partially resolves the paradox in the direction of the network account: in an
      intact animal carrying a destabilising alpha-II spectrin variant, excitability
      and seizure susceptibility go up, not down. It does not close the question,
      because this variant sits in repeat 10 rather than the DEE5 heterodimerization
      repeats, and because the measurement is at network rather than single-neuron
      level - which is precisely the level at which the sign is proposed to invert.
  - reference: PMID:41370269
    reference_title: "Axon initial segment damage and hyperexcitability in a mutant mouse with increased calpain-dependent cleavage of αII-Spectrin."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Morphological analysis revealed fewer AIS structures, along with structural defects such as shortening and thinning of these segments."
    explanation: >-
      Shows AIS damage and network hyperexcitability coexisting in the same animals,
      which is the combination the raised single-neuron threshold has to be reconciled
      with.
  proposed_experiments:
  - experiment_id: exp_cell_type_resolved_threshold_comparison
    name: Cell-type-resolved excitability in SPTAN1-mutant cortex
    description: >-
      Record action potential threshold and firing from identified GABAergic
      interneurons and pyramidal neurons in the same SPTAN1-mutant cortical
      preparation, together with inhibitory and excitatory synaptic currents onto
      each. If interneurons show a larger threshold shift than pyramidal cells, the
      disinhibition account is supported directly; if both shift equally, the seizures
      must arise from the synaptic rather than the intrinsic arm, and the raised
      threshold is a bystander finding.

- discussion_id: gap_no_model_carries_the_dee5_allele
  prompt: >-
    No published animal model carries an in-frame variant in the last two spectrin
    repeats - the only variant class that causes DEE5. What is being modelled instead,
    and what does that cost?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Spectrin Heterodimer Aggregation
  - pathophysiology#De Novo In-Frame SPTAN1 Variant in the Heterodimerization Repeats
  rationale: >-
    The in vivo evidence for this disorder comes from two models, and neither carries
    the disease allele. The conditional knockout deletes alpha-II spectrin outright,
    so it cannot aggregate and cannot exert a dominant-negative effect - it shows what
    the protein is required for, not what the mutant protein does. The R1098Q mouse is
    genuinely dominant-negative but sits in repeat 10 rather than the heterodimer
    nucleation site, and produces progressive ataxia with stress-induced seizures,
    which resembles the milder human SPTAN1 phenotypes rather than West syndrome. The
    source that describes the R1098Q model states the underlying problem plainly:
    modelling these encephalopathies has been difficult because heterozygous nulls
    show nothing and no stable transgenic line carrying a human missense variant
    exists. The practical cost is that the causal step from aggregation to seizures
    has never been tested in an animal that actually aggregates the relevant complex,
    and patient-derived neurons - which do carry the allele - cannot supply a network
    or behavioural readout. This is a mismatch in what the models can address, not
    evidence that the mechanism is wrong.
  evidence:
  - reference: PMID:36831804
    reference_title: "Progressive Ataxia, Memory Impairments, and Seizure Episodes in Spna2 R1098Q Mouse Variant Affecting Alpha II Spectrin's Scaffold Stability."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Modeling human SPTAN1 encephalopathies in laboratory animals has been challenging partially because no haploinsufficiency-related phenotypes unfold in heterozygous Spna2 deficient mice nor stable transgenic lines of mice mimicking missense human SPTAN1 mutations have been created to date."
    explanation: >-
      States both halves of the modelling gap in one sentence - nulls are silent, and
      no missense line exists.
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes."
    explanation: >-
      Defines the allele class that would have to be modelled, and that none of the
      current models carries.
  proposed_experiments:
  - experiment_id: exp_knockin_heterodimerization_repeat_allele
    name: Knock-in mouse carrying a human DEE5 heterodimerization-repeat allele
    description: >-
      Generate a knock-in mouse carrying one of the recurrent in-frame deletions or
      duplications at the alpha/beta heterodimer nucleation site, and characterise
      spectrin aggregation, AIS integrity, inhibitory innervation, EEG and seizure
      phenotype. This is the single experiment that would let the step from
      aggregation to seizure be tested in vivo, and it would also test whether the
      raised firing threshold seen in vitro holds in an intact circuit.

- discussion_id: gap_which_arm_causes_the_hypomyelination
  prompt: >-
    Cerebral hypomyelination is a diagnostic hallmark of DEE5, but alpha-II spectrin
    is a neuronal cytoskeletal protein. Is the hypomyelination a direct consequence of
    spectrin loss in oligodendrocytes, a non-cell-autonomous consequence of abnormal
    axons, or secondary to the epileptic encephalopathy itself?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Cerebral Hypomyelination
  - pathophysiology#Disrupted Dendritic and Axonal Development
  rationale: >-
    Hypomyelination is one of the features that made SPTAN1 a candidate gene in the
    first place - it was picked out partly because alpha-II spectrin is essential for
    proper myelination in zebrafish - so it is not an incidental finding. But the
    mechanism curated in the rest of this entry is neuronal: aggregation, axon initial
    segment disruption, inhibitory synapse loss. Nothing in the verified sources
    measures spectrin function in oligodendrocytes or asks whether myelination
    recovers when axonal development is rescued. The three candidate routes make
    different predictions and would support different interpretations of the MRI
    hallmark, and the entry deliberately places hypomyelination as a parallel arm
    rather than downstream of any one of them, because choosing would assert more than
    the evidence carries.
  evidence:
  - reference: PMID:20493457
    reference_title: "Dominant-negative mutations in alpha-II spectrin cause West syndrome with severe cerebral hypomyelination, spastic quadriplegia, and developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPTAN1 encoding alpha-II spectrin, which is essential for proper myelination in zebrafish, turned out to be deleted."
    explanation: >-
      The myelination link that motivated the gene's identification, and which remains
      unresolved as to cell type in the human disease.
  - reference: PMID:25631096
    reference_title: "SPTAN1 encephalopathy: distinct phenotypes and genotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition."
    explanation: >-
      Establishes hypomyelination as a diagnostic hallmark, which is why its mechanism
      matters rather than being a detail.
  proposed_experiments:
  - experiment_id: exp_conditional_oligodendrocyte_sptan1_deletion
    name: Oligodendrocyte-restricted versus neuron-restricted Sptan1 deletion
    description: >-
      Compare myelin content and oligodendrocyte maturation between mice with
      Sptan1 deleted only in oligodendrocytes and mice with it deleted only in
      neurons. Hypomyelination in the oligodendrocyte-restricted line would establish
      a cell-autonomous glial requirement; hypomyelination only in the
      neuron-restricted line would establish the non-cell-autonomous axonal route, as
      has been shown for other neuronal genes with myelin phenotypes.
📚

References & Deep Research

Deep Research

1
Claude Code ▸
SPTAN1-Related Developmental and Epileptic Encephalopathy: Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 19 citations 2026-08-19T20:13:37.996411

SPTAN1-Related Developmental and Epileptic Encephalopathy: Comprehensive Research Report

1. Disease Information

Overview. SPTAN1-related developmental and epileptic encephalopathy (SPTAN1-DEE, historically DEE5 / "early infantile epileptic encephalopathy 5," EIEE5) is a rare, genetically defined neurodevelopmental disorder caused by heterozygous (typically de novo) pathogenic variants in SPTAN1, which encodes the cytoskeletal scaffold protein αII-spectrin (non-erythrocytic spectrin alpha chain 1). The prototypic severe form presents in the first months of life with intractable epilepsy (often infantile spasms/West syndrome with hypsarrhythmia), profound global developmental delay, acquired microcephaly, spastic quadriplegia, and severe cerebral hypomyelination with progressive brain atrophy on MRI (OMIM #613477; NORD/MONDO).

Since the original 2010 description, SPTAN1 has been shown to cause a much broader phenotypic continuum rather than a single syndrome — ranging from severe infantile DEE, through milder developmental delay ± epilepsy, to pure/complex hereditary spastic paraplegia (HSP) and cerebellar ataxia, and even distal hereditary motor neuropathy — depending on variant type and location within the protein (Saitsu et al. 2010, PMID:20493457; Jaglin et al./Brain 2017, PMID:28838957; Klug et al./GenetMed 2022, PMID:36331550).

Key identifiers: - OMIM (gene): 182810 (SPTAN1, SPECTRIN ALPHA, NONERYTHROCYTIC 1) - OMIM (phenotype): #613477 — Developmental and Epileptic Encephalopathy 5 (DEE5); also 620540 — Developmental delay with or without epilepsy (DEVEP, milder allelic phenotype); Spastic Paraplegia 91, autosomal dominant, with or without cerebellar ataxia; Neuronopathy, distal hereditary motor, autosomal dominant 11 - MONDO: MONDO:0013277 (DEE5) - HGNC: SPTAN1, chromosome location 9q34.11 - Orphanet: SPTAN1 is listed as a disease-associated gene at Orphanet's gene page (multiple linked disorder entries for the epileptic-encephalopathy and HSP/ataxia phenotypes) - Common synonyms: DEE5; Early Infantile Epileptic Encephalopathy 5 (EIEE5); West syndrome due to SPTAN1 mutation; αII-spectrinopathy; SPTAN1 encephalopathy

Source of information: The evidence base is derived almost entirely from aggregated case series and case reports (dozens of published cohorts totaling well under 100 well-characterized patients) rather than large-scale population/EHR-level resources, reflecting its status as an ultra-rare disorder identified mainly through exome/genome sequencing in epilepsy and neurodevelopmental-disorder cohorts. A 2025 caregiver survey (25 families) is the largest patient-reported dataset to date (Wilson & Wong 2025, PMID:40261672).

2. Etiology

Disease causal factor. SPTAN1-DEE is a monogenic disorder caused by heterozygous variants in SPTAN1. The overwhelming majority of pathogenic variants arise de novo, though dominantly inherited and intrafamilial-variable transmission has been documented (including one family spanning "benign convulsions with mild gastroenteritis" to developmental encephalopathy — ScienceDirect 2020).

Genetic risk factors: - Causal variant classes: missense variants (clustering in specific spectrin repeats), in-frame small deletions/duplications/insertions (especially within the C-terminal α19–α20 spectrin repeats), and — for the milder DEVEP/HSP-ataxia phenotypes — truncating variants (nonsense, frameshift, splice-altering) and whole-gene microdeletions (Jaglin et al. 2017; Klug et al. 2022, PMID:36331550). - Recurrent variant: p.(Asp2303_Leu2305dup) — a 3-amino-acid duplication reported recurrently (5 unrelated patients) associated with severe infantile encephalopathy. - Modifier/susceptibility loci: none well established; phenotype is driven largely by variant location/type (see Mechanism, below) rather than a distinct modifier gene. - Locus constraint: SPTAN1 is strongly loss-of-function constrained in gnomAD (pLI ≈ 1), consistent with haploinsufficiency intolerance and supporting pathogenicity of truncating alleles (identified in a distinct distal myopathy phenotype, see below). - Contiguous-gene syndromes: 9q34.11 microdeletions can encompass SPTAN1 together with STXBP1, ENG, and TOR1A, producing blended phenotypes (Nature/GenetMed 2013).

Environmental risk factors: None established; this is a purely genetic (Mendelian) disorder with no known environmental, toxic, infectious, or lifestyle contribution to primary causation.

Protective factors: No genetic or environmental protective factors have been identified; there is no described modifier allele that mitigates severity.

Gene-environment interactions: Not applicable/not described — SPTAN1-DEE is not currently understood to involve gene-environment interaction. (Febrile illness can act as a seizure trigger in some patients, as in many genetic epilepsies, but this is symptomatic exacerbation rather than a causal G×E mechanism.)

3. Phenotypes

Clinical spectrum overview

Three broad, evidence-supported phenotypic groups have been delineated (Jaglin 2017; Klug 2022):

  1. Severe infantile developmental and epileptic encephalopathy (DEE) — the classic/original phenotype
  2. Milder developmental delay ± seizures (childhood-onset epilepsy, variable severity)
  3. Pure or complex hereditary spastic paraplegia (HSP) / hereditary ataxia, often without seizures or significant intellectual disability

A fourth, distinct presentation — heterozygous loss-of-function SPTAN1 variants causing an early-childhood-onset distal myopathy with chronic neurogenic features (foot/toe extensor weakness, gait abnormality) — has recently been reported, further widening the allelic spectrum (medRxiv/GenetMed 2024).

Symptoms/signs (Group 1 — severe DEE, HP-suggested terms)

Phenotype Frequency (reported cohorts) Onset HPO suggestion
Infantile spasms/epileptic spasms 93% of DEE group; seizures overall in 85–95% of all SPTAN1 patients Median ~4 months (first months of life) HP:0011097 (Epileptic spasms)
Hypsarrhythmia on EEG Common in DEE group Infancy HP:0011096
Profound global developmental delay/intellectual disability Nearly universal in DEE group Congenital–infantile HP:0012758 / HP:0001263
Lack of visual attention / cortical visual impairment Frequent Infancy HP:0000572
Poor head control / axial hypotonia Frequent Infancy HP:0002476
Feeding difficulties Frequent Infancy HP:0011968
Acquired (postnatal) microcephaly Frequent Infancy–childhood, progressive HP:0000252
Spastic quadriplegia Common in severe form Progressive HP:0002510
Cerebral hypomyelination ~79% on MRI Infancy, may progress HP:0007123
Progressive cerebral/cerebellar/brainstem atrophy ~93% of encephalopathy cases Progressive, often marked within 2–3 years HP:0002059 / HP:0001272
Corpus callosum thinning/agenesis ~86% — HP:0002079
Death in early childhood ~21% (7/34 in one pooled cohort) Median 5.6 years in one series —

Milder/Group 2–3 phenotype

  • 30% of a pooled cohort had less severe intellectual disability with childhood-onset epilepsy (generalized, myoclonic, focal, or no epilepsy at all)
  • Benign convulsions with mild gastroenteritis reported in one family
  • Migraine, epilepsy, and subependymal heterotopias without intellectual disability described in an extended-phenotype report (PMID:34590414)
  • Group 3 (HSP/ataxia): progressive spasticity and/or ataxia, generally without seizures or significant cognitive impairment, sometimes adult-onset; a recurrent N-terminal variant (p.Arg19Trp) is enriched in pure HSP presentations

2025 caregiver survey (real-world/patient-reported data, n=25)

Reported: epilepsy (~60%+), intellectual and motor delay, encephalopathy, motor neuropathy, absent/difficult speech, cognitive/motor decline with age, vision and hearing abnormalities, organ and skeletal effects, autoimmune disease, and immune dysfunction in some patients — broadening the phenotype beyond the classical neurologic triad (Wilson & Wong 2025, PMID:40261672). Median time to diagnosis was 3.6 years, reflecting recent uptake of genetic testing.

Quality of life impact

Severely affected individuals have profound functional impairment across all domains (mobility, communication, feeding), high caregiver burden, and shortened lifespan in the severe subgroup; the 2025 caregiver survey is the first systematic patient-reported QoL/burden dataset for this ultra-rare gene.

4. Genetic/Molecular Information

Causal gene: SPTAN1 (HGNC:11273; OMIM 182810), chromosome 9q34.11, 57 exons, encoding αII-spectrin (SPTA2/SPTAN1 protein), the principal non-erythroid α-spectrin subunit expressed in brain.

Protein structure: αII-spectrin is organized as an N-terminal tetramerization/calponin-homology actin-binding domain, ~20–21 tandem spectrin repeats (SR), a Src-homology-3 (SH3) domain (within repeat α9/α10 region), a calmodulin-binding "CCC" insert within repeat 10/11 (also containing calpain and caspase cleavage sites), and a C-terminal EF-hand calcium-binding domain. Heterodimerization with β-spectrin depends critically on the antiparallel pairing of the N-terminal repeats of β-spectrin with the C-terminal repeats (α19–α21) of α-spectrin, forming heterotetramers that build the sub-membranous actin-spectrin cytoskeleton.

Variant classification and functional consequence (genotype-phenotype correlation): - Missense and small in-frame indels in the C-terminal heterodimerization repeats (α19–α20) → most severe DEE phenotype, via a dominant-negative mechanism: mutant protein misfolds/aggregates and disrupts assembly of the wild-type spectrin-actin lattice, rather than simple haploinsufficiency (Jaglin 2017; JCI 2018, PMID unlisted but DOI 10.1172/JCI95743). - Missense variants outside the heterodimerization domain (e.g., repeats α2, α3, α11, α14, α16, α18) → milder phenotypes, better developmental outcomes. - Truncating variants (nonsense, frameshift) and whole-gene microdeletions → generally the milder developmental-delay-with-or-without-epilepsy phenotype, consistent with a haploinsufficiency (quantitative loss) mechanism rather than dominant-negative aggregation. - N-terminal tetramerization-domain missense variant p.Arg19Trp → recurrently associated with pure hereditary spastic paraplegia. - Distinct heterozygous loss-of-function (nonsense/frameshift/splice-acceptor) variants → newly described distal myopathy with chronic neurogenic features (14 families), reinforcing that LoF variants produce a mechanistically and clinically distinct phenotype from the dominant-negative DEE variants.

Functional/aggregation studies: Patient fibroblasts and iPSC-derived neurons carrying C-terminal dominant-negative variants (e.g., p.Arg1464Trp-region variants, p.Glu2207del, p.Arg19Trp) show abnormal αII-spectrin protein aggregation, shortened neurites, and disrupted cytoskeletal organization (Klug 2022, PMID:36331550; JCI 2018).

Population frequency: SPTAN1 is not a common contributor to disease broadly, but rare damaging variants account for an estimated ~1.1% of hereditary ataxia/spastic paraplegia cohorts, with statistically significant case-control enrichment (p = 2.8 × 10⁻⁵) (Klug 2022).

gnomAD constraint: pLI ≈ 1 (extremely LoF-intolerant), consistent with haploinsufficiency sensitivity; this supports pathogenicity assignment for truncating variants and argues against simple biallelic LoF as the mechanism for most DEE cases (which are heterozygous dominant-negative missense/indel).

Somatic vs. germline: All reported pathogenic variants are germline (constitutional), most de novo; no somatic mosaicism series specifically reported to date, though germline mosaicism is plausible given recurrence in some families and should be considered for genetic counseling of unaffected parents.

Epigenetics/chromosomal abnormalities: No specific DNA methylation signature or recurrent chromosomal rearrangement is described beyond the 9q34.11 contiguous microdeletions noted above (which also remove STXBP1, ENG, TOR1A).

Suggested ontology terms: HGNC:11273 (SPTAN1); GO:0008091 (spectrin); GO:0030507 (spectrin binding); GO:0030426 (growth cone); GO:0043194 (axon initial segment); GO:0030018 (Z disc, for the myopathy phenotype).

5. Environmental Information

No specific environmental toxins, occupational exposures, dietary factors, or infectious agents have been implicated as causal in SPTAN1-DEE — this is a purely monogenic disorder. Febrile illness may act as a nonspecific seizure trigger/exacerbant in some affected individuals, as is common across genetic epilepsies, but this is not disease-causal. No lifestyle or infectious contribution has been described in the literature reviewed.

6. Mechanism / Pathophysiology

Causal chain (severe DEE, dominant-negative mechanism):

  1. Trigger: De novo heterozygous missense or small in-frame indel variant, predominantly in the C-terminal spectrin repeats (α19–α20) required for α/β-spectrin heterodimerization.
  2. Molecular consequence: Mutant αII-spectrin protein misfolds and aggregates, sequestering or destabilizing wild-type αII- and βII/βIV-spectrin, producing a dominant-negative disruption of the spectrin-actin sub-membranous cytoskeleton (rather than simple loss of one allele's product) — demonstrated in patient fibroblasts, iPSC-neurons, and heterologous overexpression systems.
  3. Cellular consequence:
  4. Disruption of the axon initial segment (AIS) periodic sub-membranous spectrin-actin lattice (normally formed together with βIV-spectrin and ankyrin-G), which is required for clustering of voltage-gated sodium/potassium channels and normal action-potential initiation.
  5. Impaired dendritic and axonal development/neuronal polarity.
  6. Decreased inhibitory (GABAergic) synaptic innervation — reduced inhibitory synapse frequency shown by patch-clamp electrophysiology in a conditional mouse knockout model, implicating cortical disinhibition as a proximate seizure mechanism.
  7. Disrupted cortical lamination during development.
  8. Tissue/organ consequence: Progressive cerebral, cerebellar, and brainstem atrophy; severe hypomyelination; thinning/agenesis of the corpus callosum — visible on serial MRI, with heterodimerization-domain mutations showing the most rapid 2–3 year radiographic progression.
  9. Clinical manifestation: Infantile-onset epileptic spasms/hypsarrhythmia (West syndrome), profound developmental arrest, acquired microcephaly, spastic quadriplegia.

Molecular pathways/cellular processes: Axon initial segment assembly (GO:0043194); spectrin-based membrane skeleton organization (GO:0008091, GO:0030507); neuronal polarity establishment; GABAergic synaptogenesis and inhibitory synaptic transmission; axonal transport support (spectrin-actin lattice provides mechanical stability along the axon shaft).

Model system evidence: - Conditional knockout mouse (Sptan1^f/f; CNS-specific αII-spectrin deletion): disrupted AIS, disrupted cortical lamination, widespread neurodegeneration, seizures, and premature death (before 1 month) — full knockout is required to produce a phenotype, since heterozygous Sptan1-knockout mice show no phenotype, supporting a dominant-negative (not simple haploinsufficiency) mechanism for the severe human DEE alleles (consistent with truncating variants instead producing the milder human phenotype through haploinsufficiency) (J Neurosci 2017, PMID:29038240; JCI 2018). - In utero CRISPR/Cas9 electroporation achieving ~80% mosaic knockout recapitulates AIS and lamination defects, allowing dissection of cell-autonomous vs. non-cell-autonomous contributions. - Human iPSC-derived neurons from patients carrying dominant-negative variants show spectrin aggregation and shortened neuronal processes, directly linking the human genotype to the aggregation mechanism seen in mouse and heterologous systems. - A separate Spna2 R1098Q mouse variant model (affecting scaffold stability) shows progressive ataxia, memory impairments, and seizure episodes, modeling the milder/HSP-ataxia end of the human spectrum (PMC9953789).

Cell types implicated: cortical pyramidal neurons (CL:0000598), GABAergic interneurons (CL:0000617), oligodendrocytes/myelinating glia (secondary to hypomyelination, CL:0000128), cerebellar Purkinje/granule neurons (in the atrophy/ataxia phenotypes).

Biochemical abnormalities: No specific circulating biomarker or enzyme deficiency is described; the core defect is structural/cytoskeletal protein dysfunction (spectrin aggregation) rather than a classical metabolic lesion.

7. Anatomical Structures Affected

Organ level (primary): Central nervous system — cerebral cortex, cerebellum, brainstem, corpus callosum, and (in the neuropathy/myopathy allelic phenotypes) peripheral motor nerve and skeletal muscle.

Body systems involved: Nervous system (primary); musculoskeletal system (spasticity, distal myopathy variant); visual system (cortical visual impairment); in the 2025 caregiver survey, also reported organ/skeletal effects, immune dysfunction, and autoimmune disease in a subset — these associations require further characterization.

Tissue/cell level: - Cerebral cortex: disrupted lamination, cortical atrophy - White matter/oligodendrocytes: severe hypomyelination - Cerebellum and brainstem: progressive atrophy (hallmark of the severe form) - Axon initial segment and nodes of Ranvier (specialized axonal membrane subdomains) — primary site of spectrin-actin cytoskeletal disruption - Inhibitory (GABAergic) synapses — reduced density/function

Subcellular level: Plasma membrane-proximal sub-membranous cytoskeleton (spectrin-actin lattice); axon initial segment periodic scaffold (GO Cellular Component: axon initial segment, GO:0043194; plasma membrane region, GO:0098590).

Localization/lateralization: Diffuse, bilateral, symmetric cerebral/cerebellar involvement — no lateralization pattern reported.

Suggested UBERON terms: UBERON:0000956 (cerebral cortex), UBERON:0002037 (cerebellum), UBERON:0002298 (brainstem), UBERON:0002336 (corpus callosum), UBERON:0002037 (white matter).

8. Temporal Development

Onset: - Severe DEE group: congenital/first months of life — median onset of epileptic spasms ~4 months - Milder group: childhood onset (ages 2–15 years) for seizures; developmental delay may be apparent from infancy - HSP/ataxia group: can be later-onset, including adult presentations

Progression: - Severe form: progressive — cortical/cerebellar/brainstem atrophy and hypomyelination worsen over the first several years of life, with the most rapid MRI progression (within 2–3 years) in patients with heterodimerization-domain (α19–α20) mutations; motor and cognitive regression/plateauing is typical - Milder form: relatively stable developmental trajectory with variable, sometimes better-controlled epilepsy - HSP/ataxia form: slowly progressive spasticity/ataxia over years to decades - Caregiver-survey data additionally note cognitive and motor decline with age in some patients, suggesting the disorder is not uniformly static even outside the classic infantile-atrophy group

Disease course pattern: Predominantly progressive/degenerative in the severe DEE group (not simply a static encephalopathy); episodic seizure activity is refractory in most; some kindreds show intrafamilial variability from mild (febrile/GI-triggered convulsions) to severe encephalopathy, indicating incomplete penetrance/variable expressivity even for identical or related variants.

Duration/mortality: Chronic, lifelong; premature death reported in ~21% of a pooled severe cohort (7/34), with a reported median age at death of 5.6 years in one series.

Remission: No spontaneous remission described; seizure control, when achieved, is generally treatment-associated and often partial/refractory.

Critical periods: Infancy appears to be a critical window — the timing of epileptic-spasm onset and the degree of AIS/cortical developmental disruption in the first year of life correlate with long-term outcome, arguing for early diagnosis and intervention where possible.

9. Inheritance and Population

Epidemiology: SPTAN1-DEE is an ultra-rare disorder; exact prevalence/incidence figures are not established in the literature — the total published cohort across all phenotypic groups numbers in the low hundreds worldwide (e.g., one multi-center study identified 31 individuals from 26 families; other series report 20–34 patients). No national registry-based prevalence estimate exists.

Inheritance pattern: Autosomal dominant, overwhelmingly de novo in the DEE presentation; dominantly inherited transmission (including intrafamilial phenotypic variability) is documented for milder alleles. The distal myopathy phenotype is also autosomal dominant (heterozygous LoF).

Penetrance: Appears high but not necessarily complete for the mildest end of the spectrum (e.g., benign febrile/GI-triggered convulsions in some family members carrying the same variant as a more severely affected relative).

Expressivity: Markedly variable, both between families/variants (genotype-driven, see Mechanism) and within families carrying the identical variant (documented intrafamilial variability from benign convulsions to developmental encephalopathy).

Genetic anticipation: Not described/not applicable (not a repeat-expansion disorder).

Germline mosaicism: Not systematically studied but biologically plausible given autosomal dominant de novo inheritance patterns seen in other DEE genes; should be discussed in genetic counseling despite typically low recurrence risk for truly de novo cases.

Founder effects: None reported; variants are largely private/family-specific, with the exception of the recurrent p.(Asp2303_Leu2305dup) (severe DEE) and p.Arg19Trp (HSP) variants which appear at multiple unrelated loci (likely mutational hotspots rather than a founder effect).

Consanguinity: Not a relevant risk factor, as inheritance is autosomal dominant/de novo rather than recessive.

Carrier frequency: Not applicable (dominant disorder, not carrier-screening relevant in the classical AR sense).

Population demographics: Cohorts reported from Europe, Asia, Africa, and North America (2025 caregiver survey and the 100,000 Genomes Project/DECIPHER/GeneMatcher-based study), suggesting no strong ethnic/geographic restriction, though systematic epidemiologic mapping is lacking.

Sex ratio: No strong sex bias reported (2025 survey: 14 males, 11 females in a 25-patient cohort — roughly balanced).

Age distribution: Bimodal by phenotype group — infancy for the severe DEE group; childhood for the milder DD/epilepsy group; and childhood through adulthood (including a 72-year-old) for the HSP/ataxia group.

10. Diagnostics

Laboratory tests/biomarkers: No specific diagnostic biochemical or serum biomarker exists; diagnosis is genetic/molecular, supported by clinical and neuroimaging phenotype.

Imaging: - Brain MRI is central to diagnosis and phenotyping: severe hypomyelination (especially frontal white matter), progressive cortical/cerebellar/brainstem atrophy, thin/absent corpus callosum, and (in some extended-phenotype cases) subependymal heterotopias.

Electrophysiology: - EEG: hypsarrhythmia in the infantile-spasms subgroup; multifocal/generalized epileptiform discharges in milder groups. - Nerve conduction studies/EMG relevant for the distal hereditary motor neuropathy and myopathy allelic phenotypes (showing chronic neurogenic features).

Biopsy/pathology: Not a standard diagnostic requirement; research-level fibroblast/iPSC studies show spectrin protein aggregation (research tool, not clinical diagnostic).

Genetic testing (primary diagnostic modality): - Whole-exome sequencing (WES) or whole-genome sequencing (WGS), typically as trio analysis, is the standard approach given the phenotypic heterogeneity and de novo predominance — most reported cases were identified via exome/genome sequencing in DEE or broader NDD cohorts. - Epilepsy/DEE gene panels including SPTAN1 alongside STXBP1, SCN1A/SCN2A, KCNQ2, CDKL5, SCN8A, GRIN1, CACNA1A, etc. - Chromosomal microarray (CMA) to detect 9q34.11 microdeletions encompassing SPTAN1 (and potentially STXBP1/ENG/TOR1A). - Single-gene Sanger confirmation once a candidate variant is found by panel/exome. - Variant interpretation follows ACMG/AMP guidelines; ClinVar contains numerous SPTAN1 variant submissions classified as pathogenic/likely pathogenic for "Developmental and epileptic encephalopathy."

Differential diagnosis: Other genetic DEEs presenting with infantile spasms/early-onset refractory epilepsy — STXBP1, CDKL5, SCN2A, SCN1A, KCNQ2, SCN8A, GRIN1, KCNT1, CACNA1A, PCDH19 — distinguished by electroclinical pattern, MRI findings (SPTAN1's hallmark being pronounced hypomyelination plus progressive cerebellar/brainstem atrophy), and ultimately molecular confirmation. Contiguous 9q34.11 deletion should be considered when STXBP1 and SPTAN1 phenotypic features overlap.

Screening: No population or newborn screening program exists (ultra-rare, no biochemical marker); diagnosis is reactive, prompted by clinical presentation.

11. Outcome/Prognosis

Survival/mortality: Elevated early mortality in the severe DEE subgroup — approximately 21% (7/34) died in early childhood in one pooled cohort; specific life-expectancy tables are not established for milder phenotypes, which may have near-normal lifespan.

Morbidity/function: Severe DEE patients have profound, lifelong disability — non-ambulatory spastic quadriplegia, absent/minimal communication, tube feeding often required, refractory epilepsy. Milder-group patients retain variable but real functional capacity; HSP/ataxia-group patients have progressive but generally non-life-limiting motor disability.

Complications: Refractory epilepsy (seizures persist in most despite multiple antiseizure medications), feeding difficulties/aspiration risk, orthopedic complications of spasticity, visual impairment, and (per the 2025 caregiver survey) reported vision/hearing abnormalities, autoimmune disease, and immune dysfunction in a subset — these associations need confirmation in larger series.

Prognostic factors: Variant location and mechanism is the dominant prognostic determinant — dominant-negative missense/in-frame indel variants in the C-terminal heterodimerization domain (α19–α20) predict the most severe, rapidly progressive course; missense variants elsewhere or truncating/haploinsufficiency variants predict milder outcomes. Early, severe hypomyelination and rapid atrophy progression on serial MRI also correlate with worse neurodevelopmental outcome.

Recovery potential: Recovery in the severe form is essentially absent; the disease course is progressive/degenerative rather than static, distinguishing it from many "static encephalopathies." Milder forms may show developmental gains, particularly if seizures are better controlled.

12. Treatment

Pharmacotherapy: - Seizures in SPTAN1-DEE are characteristically highly drug-resistant. No SPTAN1-specific antiseizure medication has demonstrated superior efficacy; management follows standard infantile-spasms and refractory-epilepsy protocols. - ACTH (adrenocorticotropic hormone) and vigabatrin are first-line for infantile spasms broadly (~60–70% spasm-free with corticosteroids, ~40–60% with vigabatrin in general infantile-spasms populations; combination ACTH+vigabatrin achieves spasm cessation in ~72% in mixed-etiology cohorts). In SPTAN1 specifically, spasms may respond initially, but focal seizures typically persist/emerge after spasm resolution and remain refractory. - No pharmacogenomic (PharmGKB/CPIC) guidance specific to SPTAN1 has been established — treatment selection is empiric, as for most genetic DEEs.

Suggested NCIT terms: NCIT:C15632 (Chemotherapy — N/A here), more relevantly NCIT:C15986 (Pharmacotherapy) with therapeutic_agent bindings for corticotropin/ACTH (CHEBI or NCIT term for corticotropin) and vigabatrin (CHEBI:9645).

Dietary/nutritional therapy: - Ketogenic diet therapy (KDT) has been used as a second-line treatment after failure of hormonal therapy/vigabatrin for infantile spasms broadly; case-level evidence specifically in SPTAN1 encephalopathy (including a reported case of focal epilepsy responding to KDT) shows the diet can reduce seizure frequency, but efficacy in SPTAN1 specifically "remains unclear" given the very small number of reported cases (Cairn.info 2022; NCIT:C15447, Dietary Intervention).

Advanced/experimental therapeutics: - Antisense oligonucleotide (ASO) approaches are in active development by the patient advocacy organization Hope for SPTAN1, working toward a personalized/allele-specific ASO strategy analogous to bespoke ASO programs for other ultra-rare dominant-negative neurodevelopmental disorders (e.g., via the n-Lorem Foundation model). This mirrors the broader "screening rare genetic diagnoses for amenability to bespoke ASO therapy" paradigm now being applied across ultra-rare DEEs (see ScienceDirect 2025 review on bespoke ASO screening cohorts). Given SPTAN1-DEE's dominant-negative aggregation mechanism, allele-selective knockdown of the mutant transcript (sparing the wild-type allele) is mechanistically well-motivated — directly analogous to strategies validated for other toxic gain-of-function dominant-negative neurodevelopmental/neurodegenerative disorders (e.g., FUS-ALS allele-selective ASOs, KCNT1 DEE ASO case reports in Nature Medicine 2026). - No gene therapy, gene editing, or cell therapy program specific to SPTAN1 has yet reached publication/trial stage as of this research.

Surgical/interventional: Standard supportive orthopedic interventions for spasticity (e.g., tendon releases, tone management) as needed; no disease-specific surgical procedure exists. Vagus nerve stimulation or epilepsy surgery evaluation may be considered case-by-case for refractory focal seizures, as in other genetic DEEs, though no SPTAN1-specific outcome data were identified.

Supportive/rehabilitative care: Physical therapy, occupational therapy, speech/communication therapy, nutritional support (including gastrostomy feeding where needed), and multidisciplinary developmental support are mainstays of management (NCIT:C15302 Physical Therapy; NCIT:C15747 Supportive Care).

Experimental treatment registries: No SPTAN1-specific interventional trial was identified on ClinicalTrials.gov in this search; broader DEE natural-history/registry studies (e.g., STXBP1 natural history study, NCT05462054; neonatal-onset epileptic encephalopathy patient registry, NCT04802135) may include or be adaptable to SPTAN1 patients for natural-history data collection.

Treatment outcomes: Overall, seizure control in the severe DEE group is poor; "no effective treatment for focal seizures" following initial spasm resolution is explicitly noted in the literature. Milder-phenotype patients may achieve better seizure control with standard antiseizure medications.

13. Prevention

Because SPTAN1-DEE arises predominantly from de novo dominant variants, there is no established primary prevention strategy at the population level (no known modifiable risk factor). Relevant prevention/counseling measures include:

  • Genetic counseling: For families with a confirmed de novo SPTAN1 variant, recurrence risk for future pregnancies is low but not zero (accounting for the possibility of parental germline mosaicism); for the rarer dominantly inherited/variable-expressivity families, 50% transmission risk applies to each pregnancy, with the caveat of unpredictable severity due to variable expressivity.
  • Prenatal/preimplantation testing: Once a familial variant is identified, prenatal diagnosis (chorionic villus sampling/amniocentesis) or preimplantation genetic testing (PGT-M) can be offered for at-risk pregnancies, as for other dominant Mendelian disorders — no SPTAN1-specific program was identified, but this follows standard genetic counseling practice (NCIT:C15240 Genetic Counseling).
  • Secondary prevention: Early recognition and prompt treatment of infantile spasms (early ACTH/vigabatrin initiation) is emphasized generally in infantile-spasms management to minimize the "critical period" developmental impact, though disease-modifying benefit specific to the underlying spectrin pathology has not been demonstrated.
  • Tertiary prevention: Multidisciplinary supportive care (as above) to reduce complications (aspiration, contractures, secondary orthopedic deformity).
  • No immunization, public-health, or environmental intervention is relevant, as this is not an infectious or environmentally triggered disease.

14. Other Species / Natural Disease

No naturally occurring SPTAN1-related disease has been reported in companion animals or wildlife (no OMIA entry identified in this search). SPTAN1 orthologs are broadly conserved across vertebrates (e.g., zebrafish sptan1, ZFIN:ZDB-GENE-051113-60) and mammals, but comparative/veterinary natural-disease data specific to this gene were not found in the literature searched. This is consistent with SPTAN1-DEE being studied almost exclusively through engineered laboratory models rather than a recognized natural veterinary disease.

15. Model Organisms

Mouse models (primary model system): - Conditional CNS-specific αII-spectrin knockout mouse (Sptan1^fl/fl; Nestin-Cre or similar CNS-restricted deletion): loxP sites flanking exon 8; complete CNS knockout mice die before 1 month of age with disrupted axon initial segments, disrupted cortical lamination, widespread neurodegeneration, and seizures — directly modeling loss of the spectrin-actin cytoskeletal scaffold (J Neurosci 2017, PMID:29038240; JCI 2018). - Fidelity note: Heterozygous conditional knockout mice show no phenotype, meaning this model best recapitulates the mechanism of the milder, haploinsufficiency-driven human alleles (truncating variants) only in the homozygous/full-knockout state, while the dominant-negative aggregation mechanism underlying the most severe human DEE variants required separate approaches (patient-variant overexpression, iPSC models) to be captured — an important human-model mismatch to note when interpreting knockout data against the dominant human phenotype. - In utero CRISPR/Cas9 electroporation model achieving ~80% mosaic knockout efficiency — used to dissect cell-autonomous AIS/lamination phenotypes in a temporally and spatially controlled manner. - Spna2 R1098Q point-mutant mouse (affecting αII-spectrin scaffold stability): shows progressive ataxia, memory impairments, and seizure episodes, modeling the milder ataxia/cognitive end of the human spectrum rather than the severe infantile DEE end (PMC9953789).

Cellular/iPSC models: - Patient-derived iPSC neurons (from individuals with C-terminal dominant-negative variants) recapitulate spectrin protein aggregation and shortened neuronal processes, directly linking human genotype to the aggregation mechanism proposed from mouse/heterologous data — considered a high-fidelity model for the molecular (aggregation) phenotype, though not for whole-organism seizure/developmental readouts. - Patient fibroblasts used similarly to demonstrate spectrin aggregation for specific variants (p.Arg19Trp, p.Glu2207del). - Heterologous overexpression systems (transfected cell lines expressing mutant αII-spectrin constructs) used to establish dominant-negative aggregation behavior of specific patient variants.

Zebrafish: sptan1 ortholog is annotated in ZFIN, but no published SPTAN1-specific zebrafish disease model (knockdown/knockout) was identified in this search — this remains a model-system gap relative to other DEE genes.

Applications: These models collectively support (1) the AIS-assembly/cortical-lamination/GABAergic-synapse mechanism of disease, (2) the dominant-negative aggregation mechanism for C-terminal variants versus haploinsufficiency for truncating variants, and (3) provide a preclinical substrate (particularly iPSC neurons) for testing candidate therapies such as allele-selective ASO knockdown, which is the leading translational approach currently being pursued by the patient community (Hope for SPTAN1).

Resources: MGI (Mouse Genome Informatics) for Sptan1 mouse alleles; ZFIN for zebrafish sptan1; no IMPC standardized knockout mouse line phenotype data were specifically reviewed here but would be a useful supplementary resource to check.

Summary of Key Evidence Gaps

  1. No formal GeneReviews chapter currently exists specifically for SPTAN1-DEE (unlike many other DEE genes), limiting availability of a single authoritative clinical-management reference.
  2. Population prevalence/incidence is unknown — only aggregated case-series counts exist.
  3. Genotype-phenotype correlation, while directionally clear (C-terminal dominant-negative = severe; truncating = milder; N-terminal p.Arg19Trp = HSP), remains incompletely resolved given the still-small total number of published cases.
  4. No disease-modifying or SPTAN1-specific therapy is yet validated; ASO development is at an early, patient-advocacy-driven stage.
  5. Comparative/veterinary natural disease models are absent, and zebrafish modeling has not been published, leaving mouse conditional-knockout and iPSC systems as the primary preclinical tools — with an acknowledged mismatch between the (haploinsufficiency-only) heterozygous knockout mouse and the (dominant-negative) severe human phenotype.

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 12
Resolved 11
Unresolved (possible confabulation) 1
Unverifiable 0
References weighed for topical relevance 11
On topic 7
Off topic 1

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

  • DOI:10.1172/JCI95743](https://www.jci.org/articles/view/95743 (1 mention) - Identifier did not resolve to a record

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

  • PMID:28838957 (2 mentions) - Vascular endothelium plays a key role in directing pulmonary epithelial cell differentiation.
  • shared terms: genetic

Weighed against this report's own most characteristic terms: phenotype, severe, variant, developmental, sptan1, dee, encephalopathy, patient, milder, seizure, disease, gene, genetic, epilepsy, progressive, epileptic, ataxia, cohort, spectrin, heterozygous.