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Inheritance

1

X-linked recessive HP:0001419

Hemizygous KIF4A variants at Xq13.1. Affected individuals are male; in the founding family four affected males segregated one splice-disrupting allele, and across the largest published series ten of eleven probands inherited the variant from an unaffected mother. One variant arose de novo. Carrier mothers were reported without obvious differences in developmental milestones, schooling or occupation. The carrier data cut both ways and are worth reading carefully. Unaffected transmitting mothers are what X-linked recessive inheritance predicts, but they are also what would be seen if a variant were simply not causal, which is part of why the gene-disease relationship is rated Limited rather than Definitive.

X-linked recessive inheritance

Show evidence (2 references)

PMID:24812067 SUPPORT Human Clinical

"Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."

The founding family, its allele, and the male-only expression that defines the mode.

PMID:34346154 SUPPORT Human Clinical

"In one patient, the variant occurred de novo (Patient 5), and in the 10 others, the variant is inherited from unaffected mothers, consistent with an X‐linked recessive inheritance."

The segregation pattern across the largest series, including the single de novo occurrence - so an absent family history does not exclude the diagnosis.

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Mechanistic Hypotheses

2

Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

kif4a_synaptic_ei_imbalance CANONICAL

Evidence balance 2 support

The model the field works from. KIF4A is a neuronal motor with a PARP1-binding tail, and the phenotype follows from what happens to a differentiated neuron that has lost normal KIF4A function: the balance between excitatory and inhibitory synaptic transmission shifts, dendrites and spines are malformed, chloride handling through KCC2 is disturbed, and the seizure threshold falls. It accounts for the two features present in essentially every reported case - intellectual disability and epilepsy - and it is the only arm with a direct experimental manipulation behind it in more than one system. Its weakness is that both experimental systems are rodent. The rat knockdown is an acute loss of the whole protein, and the mouse carries one patient substitution; nothing has been measured in human neurons carrying a KIF4A variant.

Pathograph links

Reduced KIF4A Motor Function -> Excitation-Inhibition Imbalance in Hippocampal Circuits DIRECT

Increased KIF4-PARP1 Binding -> PARP1-TrkB-KCC2 Signalling Disruption DIRECT

PARP1-TrkB-KCC2 Signalling Disruption -> Abnormal Dendrite and Spine Morphology DIRECT

PARP1-TrkB-KCC2 Signalling Disruption -> Excitation-Inhibition Imbalance in Hippocampal Circuits DIRECT

Abnormal Dendrite and Spine Morphology -> Excitation-Inhibition Imbalance in Hippocampal Circuits DIRECT

Excitation-Inhibition Imbalance in Hippocampal Circuits -> Seizures and Lowered Seizure Threshold DIRECT

Excitation-Inhibition Imbalance in Hippocampal Circuits -> Impaired Cognitive and Language Development INDIRECT UNKNOWN INTERMEDIATES

Show evidence (2 references)

PMID:24812067 SUPPORT In Vitro

"Knock-down of Kif4a in rat primary hippocampal neurons altered the balance between excitatory and inhibitory synaptic transmission"

The founding functional result and the origin of the excitation-inhibition framing. Graded IN_VITRO because it is a knockdown in cultured primary neurons.

PMID:36482480 SUPPORT Model Organism

"Therefore, these findings indicate that KIF4 is engaged in a fundamental mechanism regulating seizure susceptibility and could be a potential target for epilepsy treatment."

The authors' conclusion from the knock-in mouse, which is the strongest in vivo support the synaptic model has.

Impaired mitotic chromosome condensation and midzone assembly in neural progenitors

kif4a_mitotic_neurogenesis EMERGING

Evidence balance 2 support

The alternative reading of the same gene. KIF4A's better-characterised biochemistry is mitotic: it compacts chromosomes laterally with condensin and it translocates PRC1 to organise the central spindle and midzone. A proliferation defect in neural progenitors would explain the part of the phenotype the synaptic model does not touch - microcephaly, perisylvian polymicrogyria, hippocampal malrotation and dysplasia, callosal dysgenesis, hydrocephalus - and would put KIF4A alongside the other kinesinopathies, KIF7, KIF11 and KIF14, in which structural brain malformation is the presenting problem. It is EMERGING because the human end of it is entirely observational. Polymicrogyria has been reported with a KIF4A variant and a hydrocephalic fetus had 12 percent of normal brain KIF4A mRNA, but no KIF4A model has been shown to have a progenitor proliferation defect, and the reported brain malformations have not been shown to arise from one.

Pathograph links

Reduced KIF4A Motor Function -> Impaired Chromosome Condensation and Midzone Assembly DIRECT

Impaired Chromosome Condensation and Midzone Assembly -> Cortical and Midline Brain Malformation INDIRECT UNKNOWN INTERMEDIATES

Cortical and Midline Brain Malformation -> Seizures and Lowered Seizure Threshold DIRECT

Cortical and Midline Brain Malformation -> Impaired Cognitive and Language Development INDIRECT UNKNOWN INTERMEDIATES

Show evidence (2 references)

PMID:34346154 SUPPORT Other

"Furthermore, KIF4A is responsible for the translocation of the cytokinesis protein PRC1, thus participating in the organization of central spindle and midzone formation during mitosis"

The mitotic function the hypothesis rests on. Graded OTHER because the sentence is the review's summary of prior cell biology, not a result the paper reports.

PMID:34346154 SUPPORT INDIRECT Human Clinical

"qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."

The one measurement linking reduced KIF4A in human brain to a structural malformation. Directness is INDIRECT because it establishes that the transcript was depleted in a malformed brain, not that a mitotic defect produced the malformation.

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Discussions and Knowledge Gaps

2

Loss of KIF4A derepresses PARP1, while the R728Q substitution binds PARP1 harder and impairs its activity. If both allele classes cause overlapping intellectual disability and epilepsy, is PARP1 dysregulation in either direction sufficient, or is only one of the two routes actually causal?

KNOWLEDGE GAP kif4a_parp1_opposite_directions

Attached to

pathophysiology#Reduced KIF4A Motor Function pathophysiology#Increased KIF4-PARP1 Binding pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption

The KIF4-PARP1 relationship is well characterised and it is inhibitory: KIF4's C-terminal module suppresses PARP-1, and depolarisation releases the suppression through CaMKII so that PARP-1 activity rises and supports neuronal survival. On that biochemistry, losing KIF4A should raise PARP1 activity. The R728Q substitution does the opposite - it lengthens the coiled coil, strengthens binding to PARP1, and lowers PARP1 activity, which is why supplementing NAD rescues those mice. So the two reported allele classes should move PARP1 in opposite directions, and both are reported with intellectual disability and epilepsy. Three readings are open and the literature does not choose between them. PARP1 activity may need to sit in a narrow band, with excursions in either direction damaging - which is common enough for signalling enzymes but has not been shown for this one in neurons. Or the loss-of-function alleles may cause disease through something other than PARP1, most obviously the mitotic route, with the PARP1 chain belonging only to R728Q. Or the direction assigned to one of the two classes may be wrong, since PARP1 activity has never actually been measured in a neuron carrying a loss-of-function KIF4A allele. This matters beyond tidiness because it decides whether NAD or a PARP1 modulator could be relevant to anyone but R728Q carriers. A therapy that raises PARP1 activity would be expected to help one allele class and harm the other.

Proposed experiments

PARP1 activity in neurons carrying loss-of-function versus R728Q KIF4A alleles

exp_mrx100_parp1_activity_by_allele_class

Measure PARP1 activity, by poly-ADP-ribose immunoblot and an activity assay, in iPSC-derived cortical neurons from a carrier of a splice-disrupting KIF4A allele, from an R728Q carrier, and from isogenic controls, at baseline and after depolarisation. Read out TrkB and KCC2 levels and intracellular chloride in the same cells, and test whether NAD supplementation moves each genotype toward or away from control.

Would support

pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption

Would refute

pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption

Supporting outcome

Both allele classes displace PARP1 activity from the control range, in opposite directions, and both show TrkB-KCC2 abnormality - which would make PARP1 dysregulation per se the shared lesion and put the whole allelic series on this node.

Refuting outcome

Loss-of-function neurons have normal PARP1 activity and normal TrkB-KCC2 levels while R728Q neurons are abnormal - which would confine this node to R728Q and leave the loss-of-function alleles needing a different mechanism, most likely the mitotic one.

Show evidence (4 references)

PMID:16630823 SUPPORT In Vitro

"The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator."

The inhibitory relationship, from which losing KIF4 should raise PARP1 activity.

PMID:16630823 SUPPORT In Vitro

"When neurons are stimulated by membrane depolarization, calcium signaling mediated by CaMKII induces dissociation of KIF4 from PARP-1, resulting in upregulation of PARP-1 activity, which supports neuron survival."

That releasing KIF4 from PARP-1 raises PARP-1 activity, which is the physiological version of what a loss-of-function allele would do constitutively.

PMID:36482480 SUPPORT In Vitro

"KIF4 is involved in the poly (ADP-ribose) polymerase (PARP) signaling pathway, and the mutation (R728Q) strengthened its affinity with PARP1 through elongation of the KIF4 coiled-coil domain."

The opposite move - tighter binding, which on the same biochemistry lowers PARP1 activity.

+ 1 more reference

Do KIF4A variants cause the reported cortical and midline brain malformations through a neural progenitor proliferation defect, or by some other route?

KNOWLEDGE GAP kif4a_mitotic_arm_unproven

Attached to

pathophysiology#Impaired Chromosome Condensation and Midzone Assembly pathophysiology#Cortical and Midline Brain Malformation

The mitotic arm of this entry is built entirely from cell biology plus clinical observation, with nothing joining them. KIF4A demonstrably compacts mitotic chromosomes with condensin and translocates PRC1 to build the midzone; patients demonstrably have polymicrogyria, microcephaly, hippocampal and callosal malformation and hydrocephalus. What is missing is any experiment showing a proliferation or division defect in a neural progenitor carrying a KIF4A variant. The knock-in mouse was not examined for one, and the only human molecular datum is a transcript measurement in a malformed fetal brain, which establishes depletion but not a mechanism. The alternative routes are not exotic. KIF4A transports the cell adhesion molecule L1CAM, and L1CAM variants cause X-linked hydrocephalus with aqueductal stenosis, so a transport defect could produce the same malformations without any mitotic involvement. Migration rather than proliferation is also a candidate, since periventricular nodular heterotopia was reported alongside the polymicrogyria. Until one of these is tested, the edge from the mitotic node to the malformation node is drawn with unknown intermediates, and the hypothesis group is EMERGING rather than ALTERNATIVE.

Proposed experiments

Neural progenitor division in KIF4A-variant cortical organoids

exp_mrx100_progenitor_division_in_organoids

Generate dorsal forebrain organoids from iPSCs carrying a loss-of-function KIF4A allele and isogenic corrected controls, and quantify mitotic index, spindle and midzone morphology, chromosome condensation, cytokinesis failure and binucleation in apical and basal progenitors, together with ventricular zone thickness and cortical plate organisation over time. Include an L1CAM-transport readout in the same material so the two candidate routes are tested side by side rather than sequentially.

Would support

pathophysiology#Impaired Chromosome Condensation and Midzone Assembly

Would refute

pathophysiology#Impaired Chromosome Condensation and Midzone Assembly

Supporting outcome

Variant organoids show impaired condensation, midzone defects or cytokinesis failure in progenitors with a reduced progenitor pool and disorganised cortical plate - which would convert the mitotic arm from EMERGING to a demonstrated mechanism and explain the malformation end of the spectrum.

Refuting outcome

Progenitor division is normal while L1CAM transport or neuronal migration is impaired - which would move the malformation node onto a transport or migration mechanism and remove the mitotic arm from the human disease.

Show evidence (3 references)

PMID:34346154 SUPPORT INDIRECT Human Clinical

"qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."

The only human molecular measurement in a malformed KIF4A brain. Directness is INDIRECT because it shows the transcript was depleted, not that division was impaired.

PMID:34346154 SUPPORT INDIRECT Other

"KIF4A motor activity allows for the anterograde transport of the cell adhesion molecule L1 (L1CAM; Peretti et al., 2002)."

The competing route. L1CAM variants cause X-linked hydrocephalus, so a transport defect could account for the same malformations. Directness is INDIRECT because it names an alternative mechanism rather than bearing on the mitotic one.

PMID:23166350 SUPPORT INDIRECT In Vitro

"chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms"

The mitotic function is real and well demonstrated; directness is INDIRECT because the work was done in dividing cells generally, not in neural progenitors and not in a KIF4A-variant background.

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Pathophysiology

9

Reduced KIF4A Motor Function

The trigger for most reported cases. The founding allele, c.1489-8_1490delins10, disrupts the acceptor splice site of exon 15 and causes exon skipping within the coiled-coil domain; a second splice allele, c.1674+1G>A, sits in intron 15. In a fetus carrying the missense p.Val699Glu, brain KIF4A mRNA was 12 percent of an age-matched control, which is the only direct measurement of allele consequence in human tissue and is what makes loss of function the default reading. ClinGen's expert panel reaches the same conclusion. Most other reported alleles are missense with deleterious in silico predictions and no functional assay, so "reduced function" for those is an inference from prediction plus domain location rather than a measurement. The 2021 series says so explicitly.

Impaired mitotic chromosome condensation and midzone assembly in neural progenitors Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

KIF4A hgnc:13339

Genetic context allele_type: SPLICE_SITE variant_origin: GERMLINE zygosity: HEMIZYGOUS functional_impact_category: LOSS_OF_FUNCTION

microtubule motor activity GO:0003777 ↓ DECREASED

Downstream

Excitation-Inhibition Imbalance in Hippocampal Circuits

Impaired Chromosome Condensation and Midzone Assembly

Show evidence (4 references)

PMID:24812067 SUPPORT Human Clinical

"Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."

The founding disruptive allele and its predicted consequence, exon skipping.

PMID:34346154 SUPPORT Human Clinical

"qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."

The only measurement of a KIF4A allele's consequence in human brain, and the basis for calling the mechanism loss of function rather than something else.

CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z SUPPORT Other

"The mechanism of pathogenicity appears to be loss of function."

The expert panel's reading of the same allelic series.

+ 1 more reference

Increased KIF4-PARP1 Binding

A second, mechanistically distinct trigger, and the only KIF4A allele with a worked-out molecular consequence. The R728Q substitution sits in the coiled-coil domain, raises the predicted coiling probability at that position, lengthens the coil, and strengthens KIF4's affinity for PARP1. Because KIF4's C-terminal module normally suppresses PARP1, binding it harder impairs PARP1 activity - which is why supplementing NAD, a PARP1 activator, rescues the mouse. This is not the same lesion as reduced motor function. It is a change in a protein-protein interaction that runs PARP1 in the opposite direction from what simple KIF4A loss would do, and it is the substance of the knowledge gap recorded below. functional_impact_category is HYPERMORPHIC rather than the LOSS_OF_FUNCTION used on the other trigger node, because KIF4's normal job at this interface is to suppress PARP1 and the variant does more of it - not because motor activity is increased, which was not measured. The patient carrying it had global developmental delay, severe intellectual disability and intractable seizures with a normal brain MRI.

Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

KIF4A hgnc:13339

Genetic context allele_type: MISSENSE variant_origin: GERMLINE zygosity: HEMIZYGOUS functional_impact_category: HYPERMORPHIC

Downstream

PARP1-TrkB-KCC2 Signalling Disruption

Show evidence (2 references)

PMID:36482480 SUPPORT Human Clinical

"Here, we identified a point mutation in KIF4A, a member of kinesin superfamily molecular motors, in patients with neurological disorders such as epilepsy, developmental delay, and intellectual disability."

The human ascertainment of the allele, before any of the modelling.

PMID:36482480 SUPPORT In Vitro

"KIF4 is involved in the poly (ADP-ribose) polymerase (PARP) signaling pathway, and the mutation (R728Q) strengthened its affinity with PARP1 through elongation of the KIF4 coiled-coil domain."

The molecular consequence, which is a gain of interaction rather than a loss of motor activity. Graded IN_VITRO because the affinity and coiled-coil work is biochemistry and structure prediction outside an organism.

PARP1-TrkB-KCC2 Signalling Disruption

The signalling chain the R728Q mouse traced. Impaired PARP1 activity alters TrkB and KCC2 expression; KCC2 is the neuronal potassium-chloride cotransporter that keeps intracellular chloride low, so lowering it raises intracellular chloride and weakens GABAergic inhibition. The chain was tested in the direction that matters: supplementing NAD, which activates PARP1, modulates TrkB-KCC2 and rescues the mouse's seizure susceptibility. KIF4's control of PARP1 was established long before the disease work. In juvenile neurons, KIF4's C-terminal domain suppresses PARP-1, depolarisation releases it through CaMKII, and the resulting PARP-1 activity supports neuronal survival - a normal physiology that a variant altering the KIF4-PARP1 interface would be expected to disturb.

Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

hippocampal pyramidal neuron CL:0000598

neuronal chloride extrusion through KCC2 GO:1902476 ↓ DECREASED

PARP1 poly-ADP-ribosyltransferase activity GO:0003950 ↓ DECREASED

Animal models

Kif4 R728Q knock-in mouse Mouse recapitulates The system in which this entire signalling arm was defined, and the only one with a pharmacological test of it - NAD, which activates PARP1, rescues the seizure phenotype, which is what makes the PARP1 step causal rather than correlative.

Downstream

Abnormal Dendrite and Spine Morphology

Excitation-Inhibition Imbalance in Hippocampal Circuits

Show evidence (4 references)

PMID:36482480 SUPPORT Model Organism

"Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."

The chain itself, in the knock-in mouse.

PMID:36482480 SUPPORT Model Organism

"supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice"

The pharmacological test that makes the chain causal rather than correlational, and confirms the direction - PARP1 activity is too low, not too high, in this genotype.

PMID:16630823 SUPPORT In Vitro

"The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator."

The normal KIF4-PARP1 relationship, which is what a variant at the interface perturbs. Graded IN_VITRO because the suppression was characterised in cultured neurons.

+ 1 more reference

Abnormal Dendrite and Spine Morphology

The structural correlate in the R728Q mouse: hippocampal pyramidal neurons with aberrant dendrite and spine morphology. Spines are where excitatory synapses sit, so a spine phenotype is the anatomical form of the synaptic model, and hyper-branched dendrites with irregular spines are a recurring finding across X-linked genetic epilepsy models rather than something peculiar to KIF4A. Nothing equivalent has been examined in a patient. Neuronal morphology is not accessible in living people, and no KIF4A patient-derived neuronal model has been reported.

Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

hippocampal pyramidal neuron CL:0000598

regulation of dendritic spine development GO:0060998 ↓ DECREASED

Downstream

Excitation-Inhibition Imbalance in Hippocampal Circuits

Show evidence (1 reference)

PMID:36482480 SUPPORT Model Organism

"Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."

The morphological finding and the pathway placed upstream of it.

Excitation-Inhibition Imbalance in Hippocampal Circuits

The convergence node of the synaptic model. Acute knockdown of Kif4a in rat primary hippocampal neurons shifts the balance between excitatory and inhibitory synaptic transmission, and the R728Q mouse arrives at the same place from the KCC2 direction, with raised intracellular chloride weakening GABAergic inhibition. The founding paper's own conclusion frames the disease this way. Two cautions. The founding functional experiment is a knockdown of the whole protein in rat culture, not a model of any patient allele. And that paper reports on two genes at once, KIF4A and KIF5C; the excitatory-synapse finding in it belongs to KIF5C and is not part of this entry.

Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons

GABAergic interneuron CL:0000617 glutamatergic neuron CL:0000679

inhibitory postsynaptic potential GO:0060080 ↓ DECREASED

Downstream

Seizures and Lowered Seizure Threshold

Impaired Cognitive and Language Development

Show evidence (2 references)

PMID:24812067 SUPPORT In Vitro

"Knock-down of Kif4a in rat primary hippocampal neurons altered the balance between excitatory and inhibitory synaptic transmission"

The measurement this node is named for. Graded IN_VITRO: cultured rat primary neurons with siRNA knockdown.

PMID:24812067 SUPPORT INDIRECT In Vitro

"Our results suggest that mutations in KIF4A and KIF5C cause ID by tipping the balance between excitatory and inhibitory synaptic excitability."

The authors' interpretation, which is where the excitation-inhibition framing of this disease comes from. Directness is INDIRECT because it is a proposed explanation for intellectual disability drawn from a culture experiment, and because the sentence covers two genes while this node covers one.

Impaired Chromosome Condensation and Midzone Assembly

The mitotic arm, and the better-established biochemistry of the two. KIF4A compacts mitotic chromosomes laterally in concert with condensin, and it translocates PRC1 to organise the central spindle and the midzone at cytokinesis. Reducing KIF4A function should therefore perturb division, and in a tissue whose size and folding depend on a precisely timed progenitor expansion that is a plausible route to microcephaly and cortical malformation. What is missing is any demonstration that it happens in a KIF4A-variant brain. The condensation and midzone work is cell-biological and was not done in neural progenitors or in a disease model, and no KIF4A model has been shown to have a progenitor proliferation defect. The downstream edge is drawn with unknown intermediates for that reason.

Impaired mitotic chromosome condensation and midzone assembly in neural progenitors

mitotic chromosome condensation GO:0030261 ↓ DECREASED mitotic cytokinesis GO:0000281 ↓ DECREASED

Downstream

Cortical and Midline Brain Malformation

Show evidence (2 references)

PMID:23166350 SUPPORT In Vitro

"chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms"

The chromosome condensation function. Graded IN_VITRO because this is cell-biological work in dividing cells, not in a disease model.

PMID:34346154 SUPPORT Other

"Furthermore, KIF4A is responsible for the translocation of the cytokinesis protein PRC1, thus participating in the organization of central spindle and midzone formation during mitosis"

The midzone function. Graded OTHER because it is the review summarising other groups' cell biology rather than reporting a result.

Cortical and Midline Brain Malformation

The structural end of the phenotypic spectrum: bilateral perisylvian and perirolandic polymicrogyria, microcephaly, hippocampal malrotation and dysplasia, corpus callosum dysgenesis, cerebellar heterotopia and asymmetric aplasia, and at the severe end hydrocephalus, ventriculomegaly and hydranencephaly. In four related males with a single KIF4A variant, all four had bilateral polymicrogyria. Two things keep this node honest. First, the mechanism above it is not demonstrated - the edge from the mitotic node carries unknown intermediates because no proliferation defect has been shown in any KIF4A model. Second, a large part of this phenotype sits outside MONDO:0010488, which names a non-syndromic intellectual disability; it is curated here because these are the same alleles in the same gene, and separating them would leave a reader thinking KIF4A causes only isolated intellectual disability.

Impaired mitotic chromosome condensation and midzone assembly in neural progenitors

Downstream

Seizures and Lowered Seizure Threshold

Impaired Cognitive and Language Development

Show evidence (2 references)

PMID:39268972 SUPPORT Human Clinical

"All had bilateral perisylvian and perirolandic polymicrogyria, while some also had malformations of the hippocampus (malrotation and dysplasia), cerebellum (heterotopias and asymmetric aplasia), corpus callosum dysgenesis, and brainstem asymmetric dysplasia."

The malformation spectrum in the one family reported specifically for it.

PMID:34346154 SUPPORT Human Clinical

"We expand the phenotype associated with KIF4A variants from developmental delay and intellectual disability with or without epilepsy to a congenital anomaly phenotype with hydrocephalus and various brain anomalies at the more severe end of phenotypic manifestations."

The phenotypic expansion, stated by the series that made it, and the reason this node is in the entry at all.

Seizures and Lowered Seizure Threshold

Epilepsy was present in all four males of the founding family, in the four brothers with polymicrogyria, and in the patient carrying R728Q, who had intractable seizures with frequent epileptic spasms on video EEG. The knock-in mouse reproduces the trait as a lowered seizure threshold rather than spontaneous epilepsy. It is not universal. The 2025 Chinese case had no seizures and no febrile convulsions, and the Japanese patient with polymicrogyria in the 2021 series had no epileptic seizures and a normal EEG at two years. Both the synaptic and the malformation routes lead here, which is why the node has two upstream parents.

Animal models

Kif4 R728Q knock-in mouse Mouse partially recapitulates The mouse is seizure-prone rather than epileptic, so it models susceptibility rather than the disease trait.

Show evidence (2 references)

PMID:24812067 SUPPORT Human Clinical

"Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."

Epilepsy alongside intellectual disability in the founding family.

PMID:36482480 SUPPORT Model Organism

"Behavioral tests showed that KIF4-mutant mice exhibited mild developmental delay with lower seizure threshold."

The trait as the mouse expresses it - a lowered threshold rather than spontaneous seizures, which is a weaker phenotype than the human one.

Impaired Cognitive and Language Development

The defining clinical endpoint: intellectual disability from mild to severe, with speech delay, behavioural difficulties and global developmental delay. In the founding family it was mild to moderate; in the R728Q patient it was severe with intractable seizures; in the 2021 series three patients had intellectual disability without any congenital structural anomaly, which is the presentation MONDO:0010488 names.

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"

The purely neurodevelopmental presentation, in the three patients of the series who had no structural anomaly.

PMID:24812067 SUPPORT Human Clinical

"showed mild to moderate ID and epilepsy"

The severity range in the founding family.

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Pathograph

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

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Phenotypes

11

Eye 1

Strabismus OCCASIONAL HP:0000486

Four of four within one family, but four of roughly thirty across the reported literature, and the family shares one variant - so the band is set against the literature rather than the family. Whether strabismus tracks the polymicrogyria rather than the gene is not established.

Show evidence (1 reference)

PMID:39268972 SUPPORT Human Clinical

"We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."

Strabismus in all four affected males of this family.

Head and Neck 1

Microcephaly OCCASIONAL HP:0000252

Show evidence (1 reference)

PMID:39268972 SUPPORT Human Clinical

"We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."

Microcephaly alongside the polymicrogyria in this family.

Nervous System 9

Intellectual Disability VERY_FREQUENT HP:0001249

VERY_FREQUENT rather than OBLIGATE because the phenotype is not universal in KIF4A carriers even within the neurodevelopmental entity: the 2021 series includes a fetus terminated at 22 weeks in whom cognition could not be assessed, and ClinGen split off two brothers with KIF4A variants and dental anomalies who had neither developmental delay nor intellectual disability.

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"

The severity range across the largest published series.

PMID:24812067 SUPPORT Human Clinical

"showed mild to moderate ID and epilepsy"

The founding family's severity.

Epilepsy FREQUENT Seizure HP:0001250

The band is a judgement from the counted cases rather than from a published frequency. No series tabulates epilepsy against a denominator of all KIF4A carriers, and the reported families are ascertained in ways that would enrich for it - one through an epilepsy cohort, one through a brain malformation cohort.

Show evidence (3 references)

PMID:24812067 SUPPORT Human Clinical

"showed mild to moderate ID and epilepsy"

Epilepsy in all four affected males of the founding family.

PMID:39268972 SUPPORT Human Clinical

"We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."

Epilepsy in a second, independently reported family.

PMID:40372222 SUPPORT Human Clinical

"No facial dysmorphism, tooth anomaly, gross motor development delay or regression, and history of seizure and febrile convulsion was noted."

A reported case without seizures, which is why this phenotype is banded below the near-universal range.

Delayed Speech and Language Development FREQUENT HP:0000750

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"

Speech delay as a component of the neurodevelopmental presentation.

PMID:40372222 SUPPORT Human Clinical

"The child, a 3-year-6-month-old male, had manifested intellectual impairment, language delay, autism, and choroid cyst revealed by cranial magnetic resonance imaging."

Language delay as a presenting feature in the most recently reported case.

Global Developmental Delay FREQUENT HP:0001263

Show evidence (2 references)

PMID:39268972 SUPPORT Human Clinical

"We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."

Global developmental delay in all four affected males of this family.

PMID:34346154 SUPPORT Human Clinical

"presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"

The same feature in the patients of the largest series who had no structural anomaly - the presentation MONDO:0010488 names.

Motor Delay OCCASIONAL HP:0001270

Not universal, and the exception is explicit: the 2025 Chinese case is reported with no gross motor delay and no regression despite intellectual impairment and language delay. That negative is quoted in the Epilepsy block, where it is also the source for the absence of seizures, rather than being repeated here as an evidence item against this phenotype - a single unaffected patient bounds the frequency but does not contradict the phenotype.

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"He showed developmental delay with head control at 5–6 months, sitting unsupported at 8 months, speaking meaningful words at 15 months, walking at 3 years and 2 months, and speaking two‐word sentences at 3 years and 6 months."

The most completely documented motor trajectory in the literature, in the de novo patient with polymicrogyria.

PMID:34346154 SUPPORT Human Clinical

"he exhibits severe developmental delay, including an inability to sit and absence of speech"

The severe end of the same feature, in the patient with hydranencephaly.

Atypical Behaviour OCCASIONAL Atypical behavior HP:0000708

Banded from three patients in the 2021 series against roughly thirty reported cases. No series applies a standardised behavioural instrument, so the term is bound at the general HP:0000708 level rather than to a specific behavioural phenotype.

Show evidence (1 reference)

PMID:34346154 SUPPORT Human Clinical

"presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"

Behavioural disorders alongside the cognitive and speech features.

Autism OCCASIONAL HP:0000717

A single case, and one whose causal variant is formally uncertain. The band is OCCASIONAL against the whole reported literature; the phenotype is recorded because the classifying expert panel covers autism and a reader looking for it should find the one report rather than an absence.

Show evidence (1 reference)

PMID:40372222 SUPPORT Human Clinical

"The child, a 3-year-6-month-old male, had manifested intellectual impairment, language delay, autism, and choroid cyst revealed by cranial magnetic resonance imaging."

The single reported occurrence, with the features it came with.

Polymicrogyria OCCASIONAL HP:0002126

OCCASIONAL is set against the roughly thirty reported cases overall, not against the family in which it was universal. Brain imaging was not performed in every reported patient, so the true figure could be higher; the band is limited by the denominator rather than by the finding.

Show evidence (1 reference)

PMID:39268972 SUPPORT Human Clinical

"All had bilateral perisylvian and perirolandic polymicrogyria, while some also had malformations of the hippocampus (malrotation and dysplasia), cerebellum (heterotopias and asymmetric aplasia), corpus callosum dysgenesis, and brainstem asymmetric dysplasia."

The finding in the family reported for it, with its associated malformations.

Ventriculomegaly and Hydrocephalus OCCASIONAL HP:0002119

Four of eleven in the 2021 series would band as FREQUENT, but that series was assembled through GeneMatcher starting from two families ascertained for congenital hydrocephalus, so its denominator is enriched for exactly this feature. OCCASIONAL is set against the whole reported literature instead, and the ascertainment problem is recorded here rather than left implicit in a band.

Show evidence (1 reference)

PMID:34346154 SUPPORT Human Clinical

"Brain anomalies were the predominant clinical finding, with hydrocephalus in 4 (Patients 1–4) and ventriculomegaly in 1 patient (Patient 4), with or without associated microcephaly, partial agenesis of the corpus callosum, small or malrotated hippocampus, polymicrogyria, interhemispheric cysts,..."

The counts and the associated anomalies in the series that defined this end of the spectrum.

🧬

Genetic Associations

1

KIF4A

Gene: KIF4A hgnc:13339 relationship_type: CAUSATIVE

Show evidence (3 references)

CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z SUPPORT Other

The expert-panel classification, its strength, and the fact that it is keyed to the broader neurodevelopmental entity rather than to MONDO:0010488.

CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z SUPPORT Other

"Per criteria outlined by the ClinGen Lumping and Splitting Working Group, we determined two distinct disease entities, as KIF4A was also reported in relation to the disease taurodontism, microdontia, and dens invaginatus."

The split that sets this entry's boundary. The dental phenotype is a different disease of the same gene and is deliberately not curated here.

PMID:34346154 SUPPORT Other

"KIF4A protein is characterized by a N‐terminal motor domain (aa 9‐336), a coiled coil domain (aa 350‐999), and a C‐terminal globular domain."

The domain architecture the reported alleles are mapped onto. Graded OTHER because the sentence is a database-derived description rather than a result.

🗃️

External Assertions

2

OMIM intellectual developmental disorder, X-linked 100 record

OMIM disease record OMIM:300923

OMIM entry for MRX100, the KIF4A-related X-linked intellectual disability phenotype curated here. The gene record is OMIM 300521.

ClinGen Intellectual Disability and Autism GCEP gene-disease validity assertion

ClinGen gene disease validity CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z

ClinGen classifies KIF4A - complex neurodevelopmental disorder with or without congenital anomalies (X-linked) as Limited as of 2024-04-11, and records the lumping decision that splits the KIF4A dental phenotype off as a separate disease entity. Limited is the ceiling on how strongly this entry states the gene-disease relationship. Note the assertion is keyed to MONDO:0100465, the broader neurodevelopmental entity, rather than to MONDO:0010488.

💊

Medical Actions

3

Antiseizure Medication

Action: Pharmacotherapy NCIT:C15986

Platform: Small molecule

Symptomatic management of the epilepsy that accompanies most reported cases. Nothing about the choice of agent is KIF4A-specific in the published literature, and no report gives a seizure outcome tied to a named drug; the R728Q patient's seizures were described as intractable, which is the only prognostic signal on record.

Developmental and Educational Support

Action: rehabilitation Ontology label: Rehabilitation NCIT:C15315

Platform: Behavioral / lifestyle

Speech and language therapy, early intervention and educational support for the intellectual disability, speech delay and behavioural difficulties. As with the antiseizure medication, this is standard management for the phenotype rather than anything derived from KIF4A biology.

Genetic Counselling and Carrier Testing

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Platform: Other

X-linked recessive counselling: a carrier mother has a 50 percent chance of transmitting to each son, who would be affected, and to each daughter, who would be a carrier. The founding family had four affected males, and the 2021 series found the variant inherited from an unaffected mother in ten of eleven probands, so the recurrence risk is not theoretical. Counselling has to carry the Limited gene-disease classification and the frequency of uncertain missense results with it.

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"In one patient, the variant occurred de novo (Patient 5), and in the 10 others, the variant is inherited from unaffected mothers, consistent with an X‐linked recessive inheritance."

The transmission pattern counselling is about, including the de novo exception.

PMID:40372222 SUPPORT Human Clinical

"Above finding has provided a reference for the clinical diagnosis and genetic counseling and enriched the mutation spectrum of the KIF4A gene."

The use the reporting authors put their own finding to, in a case where the variant was ACMG-uncertain and also carried by unaffected female relatives.

🔬

Diagnosis

1

Exome or genome sequencing in a male with unexplained intellectual disability

MRX100 has no feature that identifies it clinically. The founding family was found by next-generation sequencing in an intellectual disability cohort; the largest series was assembled genotype-first through GeneMatcher after diagnostic exome sequencing; the 2025 Chinese case was found by whole-exome sequencing with Sanger confirmation and parental segregation. The interpretive problem is the hard part. Most reported alleles are missense, KIF4A is rated Limited, and maternal segregation from an unaffected carrier is both what the inheritance model predicts and what a benign variant would show. A KIF4A variant of uncertain significance in a male with intellectual disability is genuinely uncertain, and the 2025 report is a worked example: the variant it reports is ACMG-uncertain, absent from dbSNP, OMIM, HGMD, ClinVar and gnomAD, and carried by the unaffected mother and sister.

Show evidence (3 references)

PMID:40372222 SUPPORT Human Clinical

"The variant was classified as of uncertain significance based on the guidelines from the ACMG."

The interpretive difficulty stated plainly by the reporting authors about their own variant.

PMID:34346154 SUPPORT Human Clinical

"Caution still applies to missense variants"

The same caution from the largest series, which is the reason this entry frames diagnosis around interpretation rather than around detection.

PMID:34346154 SUPPORT Human Clinical

"For formal reasons, all missense variants identified had to be classified VUS using strict ACMG criteria."

The scale of the interpretive problem: every missense allele in the largest published series is formally uncertain, which is why a KIF4A missense result cannot be treated as diagnostic on its own.

📊

Prevalence

1

Worldwide, published cases

Cases In Literature Ultra Rare

About thirty reported individuals as of 2025 - a 2025 literature review counted 27 cases across six articles, and ClinGen counted ten variants in fifteen probands across three publications in the 2024 curation. No population prevalence estimate exists and none is asserted here.

Show evidence (2 references)

PMID:40372222 SUPPORT Human Clinical

"A review of the literature had retrieved 6 relevant articles documenting a total of 27 cases of KIF4A gene mutations, with only one case from China."

The literature count, and the note that reporting is geographically narrow.

CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z SUPPORT Other

"Ten variants (missense and in-frame indel) that have been reported in 15 probands across 3 publications"

The count ClinGen accepted for curation, which is smaller than the literature count because it excludes the cases assigned to the separate dental entity.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Intellectual Disability X-linked 100:

L1CAM-related X-linked hydrocephalus

Overlapping Features The closest differential for the malformation end of the KIF4A spectrum, and the reason a KIF4A variant in a male fetus with hydrocephalus is not self-evidently the answer. L1CAM variants cause X-linked isolated and syndromic hydrocephalus with aqueductal stenosis, and the KIF4A patients reported with hydrocephalus, hydranencephaly and ventriculomegaly - one with confirmed aqueductal stenosis - were explicitly described as resembling that phenotype. The overlap is not coincidental, which is what makes the differential mechanistically interesting rather than merely clinical: KIF4A transports L1CAM and belongs to the L1CAM recycling pathway, so the two genes plausibly converge. This is also the competing route to the malformation node recorded in the mitotic knowledge gap.

Distinguishing Features

Sequencing, not phenotype. Neither the imaging nor the inheritance pattern separates them: both are X-linked, both give aqueductal stenosis and severe ventriculomegaly in males. L1CAM-related disease is the far better established of the two, with a Definitive gene-disease relationship, whereas KIF4A is rated Limited - so an L1CAM variant should be excluded before a KIF4A variant is called causal in this presentation.

Show evidence (2 references)

PMID:34346154 SUPPORT Human Clinical

"We identified three patients with hydrocephalus, hydranencephaly, and ventriculomegaly, with confirmed aqueductal stenosis in one, similar to L1CAM hydrocephalus phenotypes."

The authors' own comparison of their KIF4A patients to the L1CAM phenotype.

PMID:34346154 SUPPORT Other

"KIF4A is a member of the L1CAM recycling pathway and variants in L1CAM are well known to cause X‐linked isolated and syndromic hydrocephalus"

The functional relationship that makes the two overlap. Graded OTHER because the sentence is the review's reasoning about prior work rather than a result it reports.

Other kinesinopathies with brain malformation

Overlapping Features KIF7, KIF11 and KIF14 variants cause structural brain malformation syndromes - acrocallosal and Joubert syndrome 12 and hydrolethalus syndrome 2 for KIF7, Meckel syndrome 12 and primary microcephaly for KIF14 - and the anomaly patterns overlap what has been reported for KIF4A. A patient with microcephaly, callosal dysgenesis and cerebellar anomalies is not distinguishable from these on imaging.

Distinguishing Features

Inheritance is the first discriminator: KIF4A is X-linked and affects males, while KIF7 and KIF14 disease is autosomal recessive. Beyond that it is sequencing. The KIF7 and KIF14 disorders also carry a ciliopathy signature - polydactyly, molar tooth sign, cystic kidneys as part of a recognised syndrome - that has not been described as a coherent pattern in KIF4A patients, though cystic dysplastic kidneys were reported in one KIF4A sibling pair.

Show evidence (1 reference)

PMID:34346154 SUPPORT Other

"Anomaly patterns reminiscent of ciliopathies have been described particularly for pathogenic variants in KIF7 (Acrocallosal syndrome/Joubert syndrome 12, OMIM #200990; Hydrolethalus syndrome 2, OMIM #614120; Putoux et al., 2011) and KIF14 (Meckel syndrome 12, OMIM #616258; primary Microcephaly,..."

The kinesinopathies whose malformation patterns overlap this one. Graded OTHER because it is the review's summary of other disorders, not a finding about KIF4A patients.

Other non-syndromic X-linked intellectual disability

Overlapping Features For the presentation MONDO:0010488 actually names - a male with intellectual disability, with or without epilepsy, and normal imaging - the differential is the rest of the non-syndromic X-linked intellectual disability class, which is clinically homogeneous by definition and was historically numbered by linkage interval precisely because no phenotype separated its members.

Distinguishing Features

None clinically. The class is defined by the absence of a distinguishing feature, so separation is by sequencing alone, and the interpretive burden then falls on variant classification - which for KIF4A is unusually heavy, since every missense allele in the largest series is formally a VUS.

Show evidence (1 reference)

PMID:34346154 SUPPORT Human Clinical

"For formal reasons, all missense variants identified had to be classified VUS using strict ACMG criteria."

Why sequencing alone does not close the differential for this gene: a KIF4A missense hit in a male with non-syndromic intellectual disability leaves the question open.

🐁

Animal Models

1

Kif4 R728Q knock-in mouse

The only mouse carrying a KIF4A patient allele. Built by CRISPR/Cas9 with homology-directed repair at the mouse exon corresponding to human KIF4A exon 20, it reproduces the substitution rather than deleting the gene. Hemizygous mutant males have mild developmental delay and a lowered seizure threshold, with aberrant dendrite and spine morphology in hippocampal pyramidal neurons traced to the PARP1-TrkB-KCC2 chain. NAD supplementation rescues the seizure phenotype. The line also shows raised embryonic mortality.

Species

Mouse

Genotype

Kif4 Mut/Y, CRISPR/Cas9 knock-in of the patient R728Q substitution

Genes

KIF4A hgnc:13339

Publication

PMID:36482480

Pathograph links

PARP1-TrkB-KCC2 Signalling Disruption recapitulates fidelity: moderate The system in which this entire signalling arm was defined, and the only one with a pharmacological test of it - NAD, which activates PARP1, rescues the seizure phenotype, which is what makes the PARP1 step causal rather than correlative.

Limitations: The mouse gene is Kif4, which has no paralogue on the mouse X and shares about 85 percent of its amino acid sequence with human KIF4A, so the coiled-coil context of the substitution is similar but not identical. More importantly the allele modelled is one patient's missense change out of an allelic series that is mostly splice and missense variants read as loss of function; a substitution that strengthens PARP1 binding is not obviously representative of alleles that reduce the protein. Nothing in this chain has been measured in a human neuron.

Readouts

Dendrite and spine morphology of hippocampal pyramidal neurons

Direction: ALTERED

Interpretation: The structural output of the signalling chain, and the level at which the synaptic model becomes visible.

Show evidence (1 reference)

PMID:36482480 SUPPORT Model Organism

"Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."

The morphological readout with the pathway assigned to it.

Seizure threshold after NAD supplementation

Direction: RESTORED

Interpretation: Restoring PARP1 activity pharmacologically reverses the seizure phenotype, which establishes the direction of the lesion as reduced rather than increased PARP1 activity.

Show evidence (1 reference)

PMID:36482480 SUPPORT Model Organism

"supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice"

The rescue and the pathway it acts through.

Seizures and Lowered Seizure Threshold partially recapitulates fidelity: moderate The mouse is seizure-prone rather than epileptic, so it models susceptibility rather than the disease trait.

Limitations: The human carrying this allele had intractable epileptic spasms from infancy; the mouse has a lowered threshold on provocation and mild developmental delay. That is a substantial difference in severity, and it means the model cannot be used to argue about seizure control in patients.

Readouts

Seizure threshold

Direction: DECREASED

Interpretation: Susceptibility to provoked seizures is raised, which is the trait the model expresses in place of spontaneous epilepsy.

Show evidence (1 reference)

PMID:36482480 SUPPORT Model Organism

"Behavioral tests showed that KIF4-mutant mice exhibited mild developmental delay with lower seizure threshold."

Both behavioural findings, and the mildness of the developmental one.

Show evidence (1 reference)

PMID:36482480 SUPPORT Model Organism

"Therefore, these findings indicate that KIF4 is engaged in a fundamental mechanism regulating seizure susceptibility and could be a potential target for epilepsy treatment."

The authors' conclusion about what the model establishes, which is what makes it informative for the seizure node.

{ }

Source YAML

click to show

name: Intellectual Disability X-linked 100
category: Mendelian
creation_date: "2026-08-31T00:00:00Z"
synonyms:
- MRX100
- XLID100
- intellectual developmental disorder, X-linked 100
- mental retardation, X-linked 100
- KIF4A-related X-linked intellectual disability
- non-syndromic X-linked intellectual disability caused by mutation in KIF4A
description: >-
  MRX100 is X-linked intellectual disability caused by hemizygous KIF4A variants, defined in
  2014 in four affected males from a single family who had mild to moderate intellectual
  disability and epilepsy. KIF4A is a kinesin-4 chromokinesin with two quite different day
  jobs - it condenses mitotic chromosomes and builds the central spindle with PRC1, and it
  binds and restrains PARP1 in postmitotic neurons - and which of those routes explains the
  neurodevelopmental phenotype is the question this entry is organised around.

  The evidence base is thin and should be read as such. ClinGen's Intellectual Disability and
  Autism expert panel classifies the gene-disease relationship as Limited, on ten variants in
  fifteen probands across three publications. About thirty affected individuals are on record
  worldwide. Most reported alleles are missense with in silico support rather than
  demonstrated function, and the authors of the largest series say in as many words that
  caution still applies to missense variants. The one 2025 Chinese case report describes a
  variant that ACMG classifies as uncertain and that the proband's unaffected mother and
  sister also carry. Nothing here should be read as a settled gene.

  The label is also under strain in both directions. On one side MONDO:0010488 sits under
  non-syndromic X-linked intellectual disability, but the reported phenotype has expanded to
  include epilepsy, microcephaly, perisylvian polymicrogyria, hippocampal and callosal
  anomalies, hydrocephalus, and anomalies of the kidneys and urinary tract - features that
  are anything but non-syndromic. ClinGen curates the broader entity, "complex
  neurodevelopmental disorder with or without congenital anomalies", for this gene. On the
  other side ClinGen explicitly split off a second KIF4A disease - taurodontism, microdontia
  and dens invaginatus in two brothers with no developmental delay at all - and that split is
  respected here: the dental phenotype is not curated in this entry.

  Two mechanistic models are carried, and they are not variants of one story. The canonical
  one is synaptic: knocking down Kif4a in rat hippocampal neurons shifts the balance between
  excitatory and inhibitory transmission, and a knock-in mouse carrying the patient R728Q
  substitution has malformed dendrites and spines, a lowered seizure threshold, and a
  PARP1-TrkB-KCC2 chain running underneath it that NAD supplementation partly reverses. The
  emerging one is mitotic: KIF4A condenses chromosomes and organises the midzone, a fetus
  with hydrocephalus had 12 percent of normal brain KIF4A mRNA, and polymicrogyria and
  microcephaly are what a neural progenitor proliferation defect looks like. No experiment
  yet demonstrates a proliferation defect in a KIF4A model, so the mitotic arm is EMERGING
  and its consequences are drawn as edges with unknown intermediates.

  One detail deserves attention because it complicates the tidy version. Loss of KIF4
  derepresses PARP1 - the C-terminal domain is what suppresses it - whereas the R728Q
  substitution lengthens the coiled coil, binds PARP1 more tightly, and impairs PARP1
  activity, which is why NAD rescues that mouse. The two variant classes therefore push
  PARP1 in opposite directions while producing overlapping phenotypes. That is recorded as a
  knowledge gap rather than smoothed into a single arrow.
disease_term:
  preferred_term: intellectual disability, X-linked 100
  term:
    id: MONDO:0010488
    label: intellectual disability, X-linked 100
parents:
- Non-Syndromic X-Linked Intellectual Disability
external_assertions:
- name: OMIM intellectual developmental disorder, X-linked 100 record
  source: OMIM
  assertion_type: disease_record
  external_id: OMIM:300923
  description: >-
    OMIM entry for MRX100, the KIF4A-related X-linked intellectual disability phenotype
    curated here. The gene record is OMIM 300521.
- name: ClinGen Intellectual Disability and Autism GCEP gene-disease validity assertion
  source: ClinGen
  assertion_type: gene_disease_validity
  external_id: CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z
  description: >-
    ClinGen classifies KIF4A - complex neurodevelopmental disorder with or without congenital
    anomalies (X-linked) as Limited as of 2024-04-11, and records the lumping decision that
    splits the KIF4A dental phenotype off as a separate disease entity. Limited is the ceiling
    on how strongly this entry states the gene-disease relationship. Note the assertion is
    keyed to MONDO:0100465, the broader neurodevelopmental entity, rather than to
    MONDO:0010488.
inheritance:
- name: X-linked recessive
  description: >-
    Hemizygous KIF4A variants at Xq13.1. Affected individuals are male; in the founding family
    four affected males segregated one splice-disrupting allele, and across the largest
    published series ten of eleven probands inherited the variant from an unaffected mother.
    One variant arose de novo. Carrier mothers were reported without obvious differences in
    developmental milestones, schooling or occupation.

    The carrier data cut both ways and are worth reading carefully. Unaffected transmitting
    mothers are what X-linked recessive inheritance predicts, but they are also what would be
    seen if a variant were simply not causal, which is part of why the gene-disease
    relationship is rated Limited rather than Definitive.
  inheritance_term:
    preferred_term: X-linked recessive inheritance
    term:
      id: HP:0001419
      label: X-linked recessive inheritance
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."
    explanation: The founding family, its allele, and the male-only expression that defines the mode.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In one patient, the variant occurred de novo (Patient 5), and in the 10 others, the variant is inherited from unaffected mothers, consistent with an X‐linked recessive inheritance."
    explanation: >-
      The segregation pattern across the largest series, including the single de novo
      occurrence - so an absent family history does not exclude the diagnosis.

mechanistic_hypotheses:
- hypothesis_group_id: kif4a_synaptic_ei_imbalance
  hypothesis_label: Synaptic excitation-inhibition imbalance from impaired KIF4A function in postmitotic neurons
  status: CANONICAL
  description: >-
    The model the field works from. KIF4A is a neuronal motor with a PARP1-binding tail, and
    the phenotype follows from what happens to a differentiated neuron that has lost normal
    KIF4A function: the balance between excitatory and inhibitory synaptic transmission
    shifts, dendrites and spines are malformed, chloride handling through KCC2 is disturbed,
    and the seizure threshold falls. It accounts for the two features present in essentially
    every reported case - intellectual disability and epilepsy - and it is the only arm with
    a direct experimental manipulation behind it in more than one system.

    Its weakness is that both experimental systems are rodent. The rat knockdown is an acute
    loss of the whole protein, and the mouse carries one patient substitution; nothing has
    been measured in human neurons carrying a KIF4A variant.
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Knock-down of Kif4a in rat primary hippocampal neurons altered the balance between excitatory and inhibitory synaptic transmission"
    explanation: >-
      The founding functional result and the origin of the excitation-inhibition framing.
      Graded IN_VITRO because it is a knockdown in cultured primary neurons.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Therefore, these findings indicate that KIF4 is engaged in a fundamental mechanism regulating seizure susceptibility and could be a potential target for epilepsy treatment."
    explanation: >-
      The authors' conclusion from the knock-in mouse, which is the strongest in vivo support
      the synaptic model has.
- hypothesis_group_id: kif4a_mitotic_neurogenesis
  hypothesis_label: Impaired mitotic chromosome condensation and midzone assembly in neural progenitors
  status: EMERGING
  description: >-
    The alternative reading of the same gene. KIF4A's better-characterised biochemistry is
    mitotic: it compacts chromosomes laterally with condensin and it translocates PRC1 to
    organise the central spindle and midzone. A proliferation defect in neural progenitors
    would explain the part of the phenotype the synaptic model does not touch - microcephaly,
    perisylvian polymicrogyria, hippocampal malrotation and dysplasia, callosal dysgenesis,
    hydrocephalus - and would put KIF4A alongside the other kinesinopathies, KIF7, KIF11 and
    KIF14, in which structural brain malformation is the presenting problem.

    It is EMERGING because the human end of it is entirely observational. Polymicrogyria has
    been reported with a KIF4A variant and a hydrocephalic fetus had 12 percent of normal
    brain KIF4A mRNA, but no KIF4A model has been shown to have a progenitor proliferation
    defect, and the reported brain malformations have not been shown to arise from one.
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Furthermore, KIF4A is responsible for the translocation of the cytokinesis protein PRC1, thus participating in the organization of central spindle and midzone formation during mitosis"
    explanation: >-
      The mitotic function the hypothesis rests on. Graded OTHER because the sentence is the
      review's summary of prior cell biology, not a result the paper reports.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."
    explanation: >-
      The one measurement linking reduced KIF4A in human brain to a structural malformation.
      Directness is INDIRECT because it establishes that the transcript was depleted in a
      malformed brain, not that a mitotic defect produced the malformation.

pathophysiology:
- name: Reduced KIF4A Motor Function
  description: >-
    The trigger for most reported cases. The founding allele, c.1489-8_1490delins10, disrupts
    the acceptor splice site of exon 15 and causes exon skipping within the coiled-coil
    domain; a second splice allele, c.1674+1G>A, sits in intron 15. In a fetus carrying the
    missense p.Val699Glu, brain KIF4A mRNA was 12 percent of an age-matched control, which is
    the only direct measurement of allele consequence in human tissue and is what makes loss
    of function the default reading. ClinGen's expert panel reaches the same conclusion.

    Most other reported alleles are missense with deleterious in silico predictions and no
    functional assay, so "reduced function" for those is an inference from prediction plus
    domain location rather than a measurement. The 2021 series says so explicitly.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: KIF4A
    term:
      id: hgnc:13339
      label: KIF4A
  molecular_functions:
  - preferred_term: microtubule motor activity
    term:
      id: GO:0003777
      label: microtubule motor activity
    modifier: DECREASED
  genetic_context:
    functional_impact_category: LOSS_OF_FUNCTION
    allele_type: SPLICE_SITE
    variant_origin: GERMLINE
    zygosity: HEMIZYGOUS
  downstream:
  - target: Excitation-Inhibition Imbalance in Hippocampal Circuits
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  - target: Impaired Chromosome Condensation and Midzone Assembly
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_mitotic_neurogenesis
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."
    explanation: The founding disruptive allele and its predicted consequence, exon skipping.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."
    explanation: >-
      The only measurement of a KIF4A allele's consequence in human brain, and the basis for
      calling the mechanism loss of function rather than something else.
  - reference: CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z
    reference_title: "KIF4A / complex neurodevelopmental disorder with or without congenital anomalies (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The mechanism of pathogenicity appears to be loss of function."
    explanation: The expert panel's reading of the same allelic series.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: NO_EVIDENCE
    evidence_source: HUMAN_CLINICAL
    snippet: "Caution still applies to missense variants"
    explanation: >-
      Graded NO_EVIDENCE rather than REFUTE. The authors are saying that the missense alleles
      have not been functionally tested, which is absence of evidence for this node as applied
      to them, not evidence that they are benign.
- name: Increased KIF4-PARP1 Binding
  description: >-
    A second, mechanistically distinct trigger, and the only KIF4A allele with a worked-out
    molecular consequence. The R728Q substitution sits in the coiled-coil domain, raises the
    predicted coiling probability at that position, lengthens the coil, and strengthens
    KIF4's affinity for PARP1. Because KIF4's C-terminal module normally suppresses PARP1,
    binding it harder impairs PARP1 activity - which is why supplementing NAD, a PARP1
    activator, rescues the mouse.

    This is not the same lesion as reduced motor function. It is a change in a
    protein-protein interaction that runs PARP1 in the opposite direction from what simple
    KIF4A loss would do, and it is the substance of the knowledge gap recorded below.
    functional_impact_category is HYPERMORPHIC rather than the LOSS_OF_FUNCTION used on the
    other trigger node, because KIF4's normal job at this interface is to suppress PARP1 and
    the variant does more of it - not because motor activity is increased, which was not
    measured. The patient carrying it had global developmental delay, severe intellectual
    disability and intractable seizures with a normal brain MRI.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: KIF4A
    term:
      id: hgnc:13339
      label: KIF4A
  genetic_context:
    functional_impact_category: HYPERMORPHIC
    allele_type: MISSENSE
    variant_origin: GERMLINE
    zygosity: HEMIZYGOUS
  downstream:
  - target: PARP1-TrkB-KCC2 Signalling Disruption
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  evidence:
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we identified a point mutation in KIF4A, a member of kinesin superfamily molecular motors, in patients with neurological disorders such as epilepsy, developmental delay, and intellectual disability."
    explanation: The human ascertainment of the allele, before any of the modelling.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "KIF4 is involved in the poly (ADP-ribose) polymerase (PARP) signaling pathway, and the mutation (R728Q) strengthened its affinity with PARP1 through elongation of the KIF4 coiled-coil domain."
    explanation: >-
      The molecular consequence, which is a gain of interaction rather than a loss of motor
      activity. Graded IN_VITRO because the affinity and coiled-coil work is biochemistry and
      structure prediction outside an organism.
- name: PARP1-TrkB-KCC2 Signalling Disruption
  description: >-
    The signalling chain the R728Q mouse traced. Impaired PARP1 activity alters TrkB and KCC2
    expression; KCC2 is the neuronal potassium-chloride cotransporter that keeps intracellular
    chloride low, so lowering it raises intracellular chloride and weakens GABAergic
    inhibition. The chain was tested in the direction that matters: supplementing NAD, which
    activates PARP1, modulates TrkB-KCC2 and rescues the mouse's seizure susceptibility.

    KIF4's control of PARP1 was established long before the disease work. In juvenile
    neurons, KIF4's C-terminal domain suppresses PARP-1, depolarisation releases it through
    CaMKII, and the resulting PARP-1 activity supports neuronal survival - a normal
    physiology that a variant altering the KIF4-PARP1 interface would be expected to disturb.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: hippocampal pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  molecular_functions:
  - preferred_term: PARP1 poly-ADP-ribosyltransferase activity
    term:
      id: GO:0003950
      label: NAD+ poly-ADP-ribosyltransferase activity
    modifier: DECREASED
  biological_processes:
  - preferred_term: neuronal chloride extrusion through KCC2
    term:
      id: GO:1902476
      label: chloride transmembrane transport
    modifier: DECREASED
  downstream:
  - target: Abnormal Dendrite and Spine Morphology
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  - target: Excitation-Inhibition Imbalance in Hippocampal Circuits
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  evidence:
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."
    explanation: The chain itself, in the knock-in mouse.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice"
    explanation: >-
      The pharmacological test that makes the chain causal rather than correlational, and
      confirms the direction - PARP1 activity is too low, not too high, in this genotype.
  - reference: PMID:16630823
    reference_title: "KIF4 motor regulates activity-dependent neuronal survival by suppressing PARP-1 enzymatic activity."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator."
    explanation: >-
      The normal KIF4-PARP1 relationship, which is what a variant at the interface perturbs.
      Graded IN_VITRO because the suppression was characterised in cultured neurons.
  - reference: PMID:16630823
    reference_title: "KIF4 motor regulates activity-dependent neuronal survival by suppressing PARP-1 enzymatic activity."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "We suggested that KIF4 controls the activity-dependent survival of postmitotic neurons by regulating PARP-1 activity in brain development."
    explanation: >-
      Establishes that the KIF4-PARP1 axis has a developmental job in neurons at all.
      Directness is INDIRECT because the work concerns activity-dependent survival, whereas
      this node is about the TrkB-KCC2 consequences of disturbing the same axis.
- name: Abnormal Dendrite and Spine Morphology
  description: >-
    The structural correlate in the R728Q mouse: hippocampal pyramidal neurons with aberrant
    dendrite and spine morphology. Spines are where excitatory synapses sit, so a spine
    phenotype is the anatomical form of the synaptic model, and hyper-branched dendrites with
    irregular spines are a recurring finding across X-linked genetic epilepsy models rather
    than something peculiar to KIF4A.

    Nothing equivalent has been examined in a patient. Neuronal morphology is not accessible
    in living people, and no KIF4A patient-derived neuronal model has been reported.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: hippocampal pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: regulation of dendritic spine development
    term:
      id: GO:0060998
      label: regulation of dendritic spine development
    modifier: DECREASED
  downstream:
  - target: Excitation-Inhibition Imbalance in Hippocampal Circuits
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  evidence:
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."
    explanation: The morphological finding and the pathway placed upstream of it.
- name: Excitation-Inhibition Imbalance in Hippocampal Circuits
  description: >-
    The convergence node of the synaptic model. Acute knockdown of Kif4a in rat primary
    hippocampal neurons shifts the balance between excitatory and inhibitory synaptic
    transmission, and the R728Q mouse arrives at the same place from the KCC2 direction, with
    raised intracellular chloride weakening GABAergic inhibition. The founding paper's own
    conclusion frames the disease this way.

    Two cautions. The founding functional experiment is a knockdown of the whole protein in
    rat culture, not a model of any patient allele. And that paper reports on two genes at
    once, KIF4A and KIF5C; the excitatory-synapse finding in it belongs to KIF5C and is not
    part of this entry.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: GABAergic interneuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  - preferred_term: glutamatergic neuron
    term:
      id: CL:0000679
      label: glutamatergic neuron
  biological_processes:
  - preferred_term: inhibitory postsynaptic potential
    term:
      id: GO:0060080
      label: inhibitory postsynaptic potential
    modifier: DECREASED
  downstream:
  - target: Seizures and Lowered Seizure Threshold
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  - target: Impaired Cognitive and Language Development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - kif4a_synaptic_ei_imbalance
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Knock-down of Kif4a in rat primary hippocampal neurons altered the balance between excitatory and inhibitory synaptic transmission"
    explanation: >-
      The measurement this node is named for. Graded IN_VITRO: cultured rat primary neurons
      with siRNA knockdown.
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "Our results suggest that mutations in KIF4A and KIF5C cause ID by tipping the balance between excitatory and inhibitory synaptic excitability."
    explanation: >-
      The authors' interpretation, which is where the excitation-inhibition framing of this
      disease comes from. Directness is INDIRECT because it is a proposed explanation for
      intellectual disability drawn from a culture experiment, and because the sentence covers
      two genes while this node covers one.
- name: Impaired Chromosome Condensation and Midzone Assembly
  description: >-
    The mitotic arm, and the better-established biochemistry of the two. KIF4A compacts mitotic
    chromosomes laterally in concert with condensin, and it translocates PRC1 to organise the
    central spindle and the midzone at cytokinesis. Reducing KIF4A function should therefore
    perturb division, and in a tissue whose size and folding depend on a precisely timed
    progenitor expansion that is a plausible route to microcephaly and cortical malformation.

    What is missing is any demonstration that it happens in a KIF4A-variant brain. The
    condensation and midzone work is cell-biological and was not done in neural progenitors or
    in a disease model, and no KIF4A model has been shown to have a progenitor proliferation
    defect. The downstream edge is drawn with unknown intermediates for that reason.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: mitotic chromosome condensation
    term:
      id: GO:0030261
      label: chromosome condensation
    modifier: DECREASED
  - preferred_term: mitotic cytokinesis
    term:
      id: GO:0000281
      label: mitotic cytokinesis
    modifier: DECREASED
  downstream:
  - target: Cortical and Midline Brain Malformation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - kif4a_mitotic_neurogenesis
  evidence:
  - reference: PMID:23166350
    reference_title: "Mitotic chromosomes are compacted laterally by KIF4 and condensin and axially by topoisomerase IIα."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms"
    explanation: >-
      The chromosome condensation function. Graded IN_VITRO because this is cell-biological
      work in dividing cells, not in a disease model.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Furthermore, KIF4A is responsible for the translocation of the cytokinesis protein PRC1, thus participating in the organization of central spindle and midzone formation during mitosis"
    explanation: >-
      The midzone function. Graded OTHER because it is the review summarising other groups'
      cell biology rather than reporting a result.
- name: Cortical and Midline Brain Malformation
  description: >-
    The structural end of the phenotypic spectrum: bilateral perisylvian and perirolandic
    polymicrogyria, microcephaly, hippocampal malrotation and dysplasia, corpus callosum
    dysgenesis, cerebellar heterotopia and asymmetric aplasia, and at the severe end
    hydrocephalus, ventriculomegaly and hydranencephaly. In four related males with a single
    KIF4A variant, all four had bilateral polymicrogyria.

    Two things keep this node honest. First, the mechanism above it is not demonstrated - the
    edge from the mitotic node carries unknown intermediates because no proliferation defect
    has been shown in any KIF4A model. Second, a large part of this phenotype sits outside
    MONDO:0010488, which names a non-syndromic intellectual disability; it is curated here
    because these are the same alleles in the same gene, and separating them would leave a
    reader thinking KIF4A causes only isolated intellectual disability.
  biological_scale: TISSUE
  downstream:
  - target: Seizures and Lowered Seizure Threshold
    causal_link_type: DIRECT
    hypothesis_groups:
    - kif4a_mitotic_neurogenesis
  - target: Impaired Cognitive and Language Development
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - kif4a_mitotic_neurogenesis
  evidence:
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All had bilateral perisylvian and perirolandic polymicrogyria, while some also had malformations of the hippocampus (malrotation and dysplasia), cerebellum (heterotopias and asymmetric aplasia), corpus callosum dysgenesis, and brainstem asymmetric dysplasia."
    explanation: The malformation spectrum in the one family reported specifically for it.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We expand the phenotype associated with KIF4A variants from developmental delay and intellectual disability with or without epilepsy to a congenital anomaly phenotype with hydrocephalus and various brain anomalies at the more severe end of phenotypic manifestations."
    explanation: >-
      The phenotypic expansion, stated by the series that made it, and the reason this node is
      in the entry at all.
- name: Seizures and Lowered Seizure Threshold
  description: >-
    Epilepsy was present in all four males of the founding family, in the four brothers with
    polymicrogyria, and in the patient carrying R728Q, who had intractable seizures with
    frequent epileptic spasms on video EEG. The knock-in mouse reproduces the trait as a
    lowered seizure threshold rather than spontaneous epilepsy.

    It is not universal. The 2025 Chinese case had no seizures and no febrile convulsions, and
    the Japanese patient with polymicrogyria in the 2021 series had no epileptic seizures and a
    normal EEG at two years. Both the synaptic and the malformation routes lead here, which is
    why the node has two upstream parents.
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy."
    explanation: Epilepsy alongside intellectual disability in the founding family.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Behavioral tests showed that KIF4-mutant mice exhibited mild developmental delay with lower seizure threshold."
    explanation: >-
      The trait as the mouse expresses it - a lowered threshold rather than spontaneous
      seizures, which is a weaker phenotype than the human one.
- name: Impaired Cognitive and Language Development
  description: >-
    The defining clinical endpoint: intellectual disability from mild to severe, with speech
    delay, behavioural difficulties and global developmental delay. In the founding family it
    was mild to moderate; in the R728Q patient it was severe with intractable seizures; in the
    2021 series three patients had intellectual disability without any congenital structural
    anomaly, which is the presentation MONDO:0010488 names.
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"
    explanation: >-
      The purely neurodevelopmental presentation, in the three patients of the series who had
      no structural anomaly.
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "showed mild to moderate ID and epilepsy"
    explanation: The severity range in the founding family.

phenotypes:
- name: Intellectual Disability
  category: Neurological
  description: >-
    Present in essentially every reported case and the feature the disease is named for.
    Severity ranges from mild through moderate to severe across families, without a reported
    genotype-severity correlation - the largest series says as much, hoping future work will
    establish one.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"
    explanation: The severity range across the largest published series.
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "showed mild to moderate ID and epilepsy"
    explanation: The founding family's severity.
  notes: >-
    VERY_FREQUENT rather than OBLIGATE because the phenotype is not universal in KIF4A carriers
    even within the neurodevelopmental entity: the 2021 series includes a fetus terminated at
    22 weeks in whom cognition could not be assessed, and ClinGen split off two brothers with
    KIF4A variants and dental anomalies who had neither developmental delay nor intellectual
    disability.
- name: Epilepsy
  category: Neurological
  description: >-
    Seizures accompanied intellectual disability in all four males of the founding family and
    in the four brothers with polymicrogyria, and were intractable in the patient with R728Q.
    Onset in the founding family was in late childhood or early adolescence. It is not
    universal: the 2025 Chinese case had no seizure history, and one patient in the 2021 series
    had a normal EEG at two years with no seizures.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:24812067
    reference_title: "Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "showed mild to moderate ID and epilepsy"
    explanation: Epilepsy in all four affected males of the founding family.
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."
    explanation: Epilepsy in a second, independently reported family.
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No facial dysmorphism, tooth anomaly, gross motor development delay or regression, and history of seizure and febrile convulsion was noted."
    explanation: >-
      A reported case without seizures, which is why this phenotype is banded below the
      near-universal range.
  notes: >-
    The band is a judgement from the counted cases rather than from a published frequency. No
    series tabulates epilepsy against a denominator of all KIF4A carriers, and the reported
    families are ascertained in ways that would enrich for it - one through an epilepsy cohort,
    one through a brain malformation cohort.
- name: Delayed Speech and Language Development
  category: Neurological
  description: >-
    Speech delay is reported alongside intellectual disability across families and is often the
    presenting complaint. The 2025 Chinese case presented with intellectual impairment and
    language delay; in the 2021 series speech delay accompanied the intellectual disability of
    the three patients without structural anomalies. One patient spoke meaningful words at 15
    months and two-word sentences at three years and six months.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"
    explanation: Speech delay as a component of the neurodevelopmental presentation.
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The child, a 3-year-6-month-old male, had manifested intellectual impairment, language delay, autism, and choroid cyst revealed by cranial magnetic resonance imaging."
    explanation: Language delay as a presenting feature in the most recently reported case.
- name: Global Developmental Delay
  category: Neurological
  description: >-
    Delay across developmental domains, distinct from the intellectual disability diagnosis it
    precedes and from the isolated speech delay curated separately. It is the presenting
    feature in both of the families reported specifically for their phenotype, and in the
    three patients of the 2021 series who had no structural anomaly.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."
    explanation: Global developmental delay in all four affected males of this family.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"
    explanation: >-
      The same feature in the patients of the largest series who had no structural anomaly -
      the presentation MONDO:0010488 names.
- name: Motor Delay
  category: Neurological
  description: >-
    Delayed motor milestones, described in individual patients rather than tabulated. One boy
    achieved head control at five to six months, sat unsupported at eight months and walked at
    three years and two months; a more severely affected boy could not sit at four years.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He showed developmental delay with head control at 5–6 months, sitting unsupported at 8 months, speaking meaningful words at 15 months, walking at 3 years and 2 months, and speaking two‐word sentences at 3 years and 6 months."
    explanation: >-
      The most completely documented motor trajectory in the literature, in the de novo patient
      with polymicrogyria.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "he exhibits severe developmental delay, including an inability to sit and absence of speech"
    explanation: The severe end of the same feature, in the patient with hydranencephaly.
  notes: >-
    Not universal, and the exception is explicit: the 2025 Chinese case is reported with no
    gross motor delay and no regression despite intellectual impairment and language delay. That
    negative is quoted in the Epilepsy block, where it is also the source for the absence of
    seizures, rather than being repeated here as an evidence item against this phenotype - a
    single unaffected patient bounds the frequency but does not contradict the phenotype.
- name: Atypical Behaviour
  category: Neurological
  description: >-
    Behavioural difficulties accompanying the intellectual disability, reported in the patients
    of the 2021 series who had no structural anomaly. This is worth curating explicitly rather
    than leaving inside the intellectual disability description: the panel that classified this
    gene is the ClinGen Intellectual Disability and Autism expert panel, so the behavioural
    dimension is part of how the gene-disease relationship is framed.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Atypical behavior
    term:
      id: HP:0000708
      label: Atypical behavior
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented with intellectual disability, ranging from mild to severe, including speech delay and behavioral disorders, as well as global developmental delay"
    explanation: Behavioural disorders alongside the cognitive and speech features.
  notes: >-
    Banded from three patients in the 2021 series against roughly thirty reported cases. No
    series applies a standardised behavioural instrument, so the term is bound at the general
    HP:0000708 level rather than to a specific behavioural phenotype.
- name: Autism
  category: Neurological
  description: >-
    Autism was a presenting feature in the 2025 Chinese case, alongside intellectual impairment
    and language delay and without seizures or dysmorphism. It is the only report of autism in
    a KIF4A patient, and the variant in that case is ACMG-uncertain and carried by the
    proband's unaffected mother and sister.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Autism
    term:
      id: HP:0000717
      label: Autism
  evidence:
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The child, a 3-year-6-month-old male, had manifested intellectual impairment, language delay, autism, and choroid cyst revealed by cranial magnetic resonance imaging."
    explanation: The single reported occurrence, with the features it came with.
  notes: >-
    A single case, and one whose causal variant is formally uncertain. The band is OCCASIONAL
    against the whole reported literature; the phenotype is recorded because the classifying
    expert panel covers autism and a reader looking for it should find the one report rather
    than an absence.
- name: Strabismus
  category: Neurological
  description: >-
    Present in all four affected males of the family reported for bilateral polymicrogyria,
    alongside microcephaly. This is a different observation from the single-patient ocular
    findings in the 2021 series - Peters anomaly, microphthalmia, leukoma, macular coloboma -
    which remain uncurated for the ascertainment reason given in notes.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  evidence:
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."
    explanation: Strabismus in all four affected males of this family.
  notes: >-
    Four of four within one family, but four of roughly thirty across the reported literature,
    and the family shares one variant - so the band is set against the literature rather than
    the family. Whether strabismus tracks the polymicrogyria rather than the gene is not
    established.
- name: Polymicrogyria
  category: Neurological
  description: >-
    Bilateral perisylvian and perirolandic polymicrogyria in all four affected males of one
    family, and perisylvian polymicrogyria with heterotopia and hypoplastic pyramidal tracts in
    a de novo case in the 2021 series. This is the structural finding that motivates the
    mitotic hypothesis, and it is also the clearest evidence that the non-syndromic label on
    MONDO:0010488 does not fit the whole KIF4A phenotype.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Polymicrogyria
    term:
      id: HP:0002126
      label: Polymicrogyria
  evidence:
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All had bilateral perisylvian and perirolandic polymicrogyria, while some also had malformations of the hippocampus (malrotation and dysplasia), cerebellum (heterotopias and asymmetric aplasia), corpus callosum dysgenesis, and brainstem asymmetric dysplasia."
    explanation: The finding in the family reported for it, with its associated malformations.
  notes: >-
    OCCASIONAL is set against the roughly thirty reported cases overall, not against the family
    in which it was universal. Brain imaging was not performed in every reported patient, so
    the true figure could be higher; the band is limited by the denominator rather than by the
    finding.
- name: Microcephaly
  category: Neurological
  description: >-
    Reported with the malformation end of the spectrum rather than with isolated intellectual
    disability: in all four brothers with polymicrogyria, and in the 2021 series with
    progressive head circumference decline in one infant and a head circumference of minus 3.1
    standard deviations at five years in another.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:39268972
    reference_title: "X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus."
    explanation: Microcephaly alongside the polymicrogyria in this family.
- name: Ventriculomegaly and Hydrocephalus
  category: Neurological
  description: >-
    The severe end of the reported spectrum. Four patients in the 2021 series had hydrocephalus
    and one ventriculomegaly, with a fetus terminated at 22 weeks for severe hydrocephalus
    internus and another infant found to have hydranencephaly with corpus callosum agenesis.
    This is the presentation that first suggested KIF4A as a candidate for X-linked congenital
    hydrocephalus.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain anomalies were the predominant clinical finding, with hydrocephalus in 4 (Patients 1–4) and ventriculomegaly in 1 patient (Patient 4), with or without associated microcephaly, partial agenesis of the corpus callosum, small or malrotated hippocampus, polymicrogyria, interhemispheric cysts, periventricular heterotopia, and optic nerve hypoplasia."
    explanation: The counts and the associated anomalies in the series that defined this end of the spectrum.
  notes: >-
    Four of eleven in the 2021 series would band as FREQUENT, but that series was assembled
    through GeneMatcher starting from two families ascertained for congenital hydrocephalus, so
    its denominator is enriched for exactly this feature. OCCASIONAL is set against the whole
    reported literature instead, and the ascertainment problem is recorded here rather than
    left implicit in a band.

prevalence:
- population: Worldwide, published cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    About thirty reported individuals as of 2025 - a 2025 literature review counted 27 cases
    across six articles, and ClinGen counted ten variants in fifteen probands across three
    publications in the 2024 curation. No population prevalence estimate exists and none is
    asserted here.
  evidence:
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A review of the literature had retrieved 6 relevant articles documenting a total of 27 cases of KIF4A gene mutations, with only one case from China."
    explanation: The literature count, and the note that reporting is geographically narrow.
  - reference: CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z
    reference_title: "KIF4A / complex neurodevelopmental disorder with or without congenital anomalies (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Ten variants (missense and in-frame indel) that have been reported in 15 probands across 3 publications"
    explanation: >-
      The count ClinGen accepted for curation, which is smaller than the literature count
      because it excludes the cases assigned to the separate dental entity.

genetic:
- name: KIF4A
  notes: >-
    KIF4A at Xq13.1 encodes a kinesin-4 family chromokinesin with an N-terminal motor domain
    (roughly residues 9-336), a long coiled coil (roughly 350-999), and a C-terminal globular
    tail carrying a nuclear localisation signal and the PARP1-binding module. The PRC1
    interaction region overlaps the coil and tail. Reported disease alleles are distributed
    across all of these.

    ClinGen's Intellectual Disability and Autism expert panel rates the gene-disease
    relationship Limited, and in the same curation records a lumping and splitting decision:
    two brothers with KIF4A variants who had taurodontism, microdontia and dens invaginatus
    without developmental delay were assigned to a separate disease entity and excluded from
    the neurodevelopmental curation. That split is respected here, which is why no dental
    phenotype appears in this entry.
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: KIF4A
    term:
      id: hgnc:13339
      label: KIF4A
  evidence:
  - reference: CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z
    reference_title: "KIF4A / complex neurodevelopmental disorder with or without congenital anomalies (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "KIF4A | HGNC:13339 | complex neurodevelopmental disorder with or without congenital anomalies | MONDO:0100465 | XL | Limited | SOP10 | Intellectual Disability and Autism Gene Curation Expert Panel"
    explanation: >-
      The expert-panel classification, its strength, and the fact that it is keyed to the
      broader neurodevelopmental entity rather than to MONDO:0010488.
  - reference: CGGV:assertion_d71cd45d-9a5e-4505-bf0d-8dcaafdbe795-2024-04-11T100000.000Z
    reference_title: "KIF4A / complex neurodevelopmental disorder with or without congenital anomalies (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Per criteria outlined by the ClinGen Lumping and Splitting Working Group, we determined two distinct disease entities, as KIF4A was also reported in relation to the disease taurodontism, microdontia, and dens invaginatus."
    explanation: >-
      The split that sets this entry's boundary. The dental phenotype is a different disease of
      the same gene and is deliberately not curated here.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "KIF4A protein is characterized by a N‐terminal motor domain (aa 9‐336), a coiled coil domain (aa 350‐999), and a C‐terminal globular domain."
    explanation: >-
      The domain architecture the reported alleles are mapped onto. Graded OTHER because the
      sentence is a database-derived description rather than a result.

diagnosis:
- name: Exome or genome sequencing in a male with unexplained intellectual disability
  description: >-
    MRX100 has no feature that identifies it clinically. The founding family was found by
    next-generation sequencing in an intellectual disability cohort; the largest series was
    assembled genotype-first through GeneMatcher after diagnostic exome sequencing; the 2025
    Chinese case was found by whole-exome sequencing with Sanger confirmation and parental
    segregation.

    The interpretive problem is the hard part. Most reported alleles are missense, KIF4A is
    rated Limited, and maternal segregation from an unaffected carrier is both what the
    inheritance model predicts and what a benign variant would show. A KIF4A variant of
    uncertain significance in a male with intellectual disability is genuinely uncertain, and
    the 2025 report is a worked example: the variant it reports is ACMG-uncertain, absent from
    dbSNP, OMIM, HGMD, ClinVar and gnomAD, and carried by the unaffected mother and sister.
  evidence:
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The variant was classified as of uncertain significance based on the guidelines from the ACMG."
    explanation: >-
      The interpretive difficulty stated plainly by the reporting authors about their own
      variant.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Caution still applies to missense variants"
    explanation: >-
      The same caution from the largest series, which is the reason this entry frames diagnosis
      around interpretation rather than around detection.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For formal reasons, all missense variants identified had to be classified VUS using strict ACMG criteria."
    explanation: >-
      The scale of the interpretive problem: every missense allele in the largest published
      series is formally uncertain, which is why a KIF4A missense result cannot be treated as
      diagnostic on its own.

differential_diagnoses:
- name: L1CAM-related X-linked hydrocephalus
  description: >-
    The closest differential for the malformation end of the KIF4A spectrum, and the reason a
    KIF4A variant in a male fetus with hydrocephalus is not self-evidently the answer. L1CAM
    variants cause X-linked isolated and syndromic hydrocephalus with aqueductal stenosis, and
    the KIF4A patients reported with hydrocephalus, hydranencephaly and ventriculomegaly - one
    with confirmed aqueductal stenosis - were explicitly described as resembling that phenotype.

    The overlap is not coincidental, which is what makes the differential mechanistically
    interesting rather than merely clinical: KIF4A transports L1CAM and belongs to the L1CAM
    recycling pathway, so the two genes plausibly converge. This is also the competing route to
    the malformation node recorded in the mitotic knowledge gap.
  distinguishing_features:
  - >-
      Sequencing, not phenotype. Neither the imaging nor the inheritance pattern separates them:
      both are X-linked, both give aqueductal stenosis and severe ventriculomegaly in males.
      L1CAM-related disease is the far better established of the two, with a Definitive
      gene-disease relationship, whereas KIF4A is rated Limited - so an L1CAM variant should be
      excluded before a KIF4A variant is called causal in this presentation.
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified three patients with hydrocephalus, hydranencephaly, and ventriculomegaly, with confirmed aqueductal stenosis in one, similar to L1CAM hydrocephalus phenotypes."
    explanation: The authors' own comparison of their KIF4A patients to the L1CAM phenotype.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "KIF4A is a member of the L1CAM recycling pathway and variants in L1CAM are well known to cause X‐linked isolated and syndromic hydrocephalus"
    explanation: >-
      The functional relationship that makes the two overlap. Graded OTHER because the sentence
      is the review's reasoning about prior work rather than a result it reports.
- name: Other kinesinopathies with brain malformation
  description: >-
    KIF7, KIF11 and KIF14 variants cause structural brain malformation syndromes -
    acrocallosal and Joubert syndrome 12 and hydrolethalus syndrome 2 for KIF7, Meckel syndrome
    12 and primary microcephaly for KIF14 - and the anomaly patterns overlap what has been
    reported for KIF4A. A patient with microcephaly, callosal dysgenesis and cerebellar
    anomalies is not distinguishable from these on imaging.
  distinguishing_features:
  - >-
      Inheritance is the first discriminator: KIF4A is X-linked and affects males, while KIF7 and
      KIF14 disease is autosomal recessive. Beyond that it is sequencing. The KIF7 and KIF14
      disorders also carry a ciliopathy signature - polydactyly, molar tooth sign, cystic kidneys
      as part of a recognised syndrome - that has not been described as a coherent pattern in
      KIF4A patients, though cystic dysplastic kidneys were reported in one KIF4A sibling pair.
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Anomaly patterns reminiscent of ciliopathies have been described particularly for pathogenic variants in KIF7 (Acrocallosal syndrome/Joubert syndrome 12, OMIM #200990; Hydrolethalus syndrome 2, OMIM #614120; Putoux et al., 2011) and KIF14 (Meckel syndrome 12, OMIM #616258; primary Microcephaly, OMIM# 617914; Filges et al., 2013; Moawia et al., 2017)."
    explanation: >-
      The kinesinopathies whose malformation patterns overlap this one. Graded OTHER because it
      is the review's summary of other disorders, not a finding about KIF4A patients.
- name: Other non-syndromic X-linked intellectual disability
  description: >-
    For the presentation MONDO:0010488 actually names - a male with intellectual disability,
    with or without epilepsy, and normal imaging - the differential is the rest of the
    non-syndromic X-linked intellectual disability class, which is clinically homogeneous by
    definition and was historically numbered by linkage interval precisely because no phenotype
    separated its members.
  distinguishing_features:
  - >-
      None clinically. The class is defined by the absence of a distinguishing feature, so
      separation is by sequencing alone, and the interpretive burden then falls on variant
      classification - which for KIF4A is unusually heavy, since every missense allele in the
      largest series is formally a VUS.
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For formal reasons, all missense variants identified had to be classified VUS using strict ACMG criteria."
    explanation: >-
      Why sequencing alone does not close the differential for this gene: a KIF4A missense hit
      in a male with non-syndromic intellectual disability leaves the question open.

treatments:
- name: Antiseizure Medication
  description: >-
    Symptomatic management of the epilepsy that accompanies most reported cases. Nothing about
    the choice of agent is KIF4A-specific in the published literature, and no report gives a
    seizure outcome tied to a named drug; the R728Q patient's seizures were described as
    intractable, which is the only prognostic signal on record.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  notes: >-
    Carries no evidence item deliberately. No KIF4A publication reports an antiseizure regimen
    or its outcome, so citing one would be citing a paper for something it does not say. The
    treatment is recorded because omitting it would misrepresent management of a disorder in
    which epilepsy is common, and its unsupported status is stated here rather than dressed in
    a citation.
- name: Developmental and Educational Support
  description: >-
    Speech and language therapy, early intervention and educational support for the
    intellectual disability, speech delay and behavioural difficulties. As with the antiseizure
    medication, this is standard management for the phenotype rather than anything derived from
    KIF4A biology.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  notes: >-
    Carries no evidence item deliberately, for the same reason as the antiseizure entry - no
    KIF4A report describes a developmental intervention or its outcome.
- name: Genetic Counselling and Carrier Testing
  description: >-
    X-linked recessive counselling: a carrier mother has a 50 percent chance of transmitting to
    each son, who would be affected, and to each daughter, who would be a carrier. The founding
    family had four affected males, and the 2021 series found the variant inherited from an
    unaffected mother in ten of eleven probands, so the recurrence risk is not theoretical.
    Counselling has to carry the Limited gene-disease classification and the frequency of
    uncertain missense results with it.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In one patient, the variant occurred de novo (Patient 5), and in the 10 others, the variant is inherited from unaffected mothers, consistent with an X‐linked recessive inheritance."
    explanation: The transmission pattern counselling is about, including the de novo exception.
  - reference: PMID:40372222
    reference_title: "[Analysis of a child with X-linked intellectual disability type 100 due to variant of KIF4A gene and a literature review]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Above finding has provided a reference for the clinical diagnosis and genetic counseling and enriched the mutation spectrum of the KIF4A gene."
    explanation: >-
      The use the reporting authors put their own finding to, in a case where the variant was
      ACMG-uncertain and also carried by unaffected female relatives.

animal_models:
- name: Kif4 R728Q knock-in mouse
  species: Mouse
  genotype: Kif4 Mut/Y, CRISPR/Cas9 knock-in of the patient R728Q substitution
  publication: PMID:36482480
  description: >-
    The only mouse carrying a KIF4A patient allele. Built by CRISPR/Cas9 with
    homology-directed repair at the mouse exon corresponding to human KIF4A exon 20, it
    reproduces the substitution rather than deleting the gene. Hemizygous mutant males have
    mild developmental delay and a lowered seizure threshold, with aberrant dendrite and spine
    morphology in hippocampal pyramidal neurons traced to the PARP1-TrkB-KCC2 chain. NAD
    supplementation rescues the seizure phenotype. The line also shows raised embryonic
    mortality.
  genes:
  - preferred_term: KIF4A
    term:
      id: hgnc:13339
      label: KIF4A
  modeled_mechanisms:
  - target: PARP1-TrkB-KCC2 Signalling Disruption
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The system in which this entire signalling arm was defined, and the only one with a
      pharmacological test of it - NAD, which activates PARP1, rescues the seizure phenotype,
      which is what makes the PARP1 step causal rather than correlative.
    limitations: >-
      The mouse gene is Kif4, which has no paralogue on the mouse X and shares about 85 percent
      of its amino acid sequence with human KIF4A, so the coiled-coil context of the
      substitution is similar but not identical. More importantly the allele modelled is one
      patient's missense change out of an allelic series that is mostly splice and missense
      variants read as loss of function; a substitution that strengthens PARP1 binding is not
      obviously representative of alleles that reduce the protein. Nothing in this chain has
      been measured in a human neuron.
    readouts:
    - name: Dendrite and spine morphology of hippocampal pyramidal neurons
      target: PARP1-TrkB-KCC2 Signalling Disruption
      direction: ALTERED
      interpretation: >-
        The structural output of the signalling chain, and the level at which the synaptic
        model becomes visible.
      evidence:
      - reference: PMID:36482480
        reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway."
        explanation: The morphological readout with the pathway assigned to it.
    - name: Seizure threshold after NAD supplementation
      target: PARP1-TrkB-KCC2 Signalling Disruption
      direction: RESTORED
      interpretation: >-
        Restoring PARP1 activity pharmacologically reverses the seizure phenotype, which
        establishes the direction of the lesion as reduced rather than increased PARP1 activity.
      evidence:
      - reference: PMID:36482480
        reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice"
        explanation: The rescue and the pathway it acts through.
  - target: Seizures and Lowered Seizure Threshold
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      The mouse is seizure-prone rather than epileptic, so it models susceptibility rather than
      the disease trait.
    limitations: >-
      The human carrying this allele had intractable epileptic spasms from infancy; the mouse
      has a lowered threshold on provocation and mild developmental delay. That is a
      substantial difference in severity, and it means the model cannot be used to argue about
      seizure control in patients.
    readouts:
    - name: Seizure threshold
      target: Seizures and Lowered Seizure Threshold
      direction: DECREASED
      interpretation: >-
        Susceptibility to provoked seizures is raised, which is the trait the model expresses in
        place of spontaneous epilepsy.
      evidence:
      - reference: PMID:36482480
        reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Behavioral tests showed that KIF4-mutant mice exhibited mild developmental delay with lower seizure threshold."
        explanation: Both behavioural findings, and the mildness of the developmental one.
  evidence:
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Therefore, these findings indicate that KIF4 is engaged in a fundamental mechanism regulating seizure susceptibility and could be a potential target for epilepsy treatment."
    explanation: >-
      The authors' conclusion about what the model establishes, which is what makes it
      informative for the seizure node.

discussions:
- discussion_id: kif4a_parp1_opposite_directions
  kind: KNOWLEDGE_GAP
  prompt: >-
    Loss of KIF4A derepresses PARP1, while the R728Q substitution binds PARP1 harder and
    impairs its activity. If both allele classes cause overlapping intellectual disability and
    epilepsy, is PARP1 dysregulation in either direction sufficient, or is only one of the two
    routes actually causal?
  attaches_to:
  - pathophysiology#Reduced KIF4A Motor Function
  - pathophysiology#Increased KIF4-PARP1 Binding
  - pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption
  rationale: >-
    The KIF4-PARP1 relationship is well characterised and it is inhibitory: KIF4's C-terminal
    module suppresses PARP-1, and depolarisation releases the suppression through CaMKII so
    that PARP-1 activity rises and supports neuronal survival. On that biochemistry, losing
    KIF4A should raise PARP1 activity. The R728Q substitution does the opposite - it lengthens
    the coiled coil, strengthens binding to PARP1, and lowers PARP1 activity, which is why
    supplementing NAD rescues those mice.

    So the two reported allele classes should move PARP1 in opposite directions, and both are
    reported with intellectual disability and epilepsy. Three readings are open and the
    literature does not choose between them. PARP1 activity may need to sit in a narrow band,
    with excursions in either direction damaging - which is common enough for signalling
    enzymes but has not been shown for this one in neurons. Or the loss-of-function alleles may
    cause disease through something other than PARP1, most obviously the mitotic route, with
    the PARP1 chain belonging only to R728Q. Or the direction assigned to one of the two classes
    may be wrong, since PARP1 activity has never actually been measured in a neuron carrying a
    loss-of-function KIF4A allele.

    This matters beyond tidiness because it decides whether NAD or a PARP1 modulator could be
    relevant to anyone but R728Q carriers. A therapy that raises PARP1 activity would be
    expected to help one allele class and harm the other.
  evidence:
  - reference: PMID:16630823
    reference_title: "KIF4 motor regulates activity-dependent neuronal survival by suppressing PARP-1 enzymatic activity."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator."
    explanation: >-
      The inhibitory relationship, from which losing KIF4 should raise PARP1 activity.
  - reference: PMID:16630823
    reference_title: "KIF4 motor regulates activity-dependent neuronal survival by suppressing PARP-1 enzymatic activity."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "When neurons are stimulated by membrane depolarization, calcium signaling mediated by CaMKII induces dissociation of KIF4 from PARP-1, resulting in upregulation of PARP-1 activity, which supports neuron survival."
    explanation: >-
      That releasing KIF4 from PARP-1 raises PARP-1 activity, which is the physiological
      version of what a loss-of-function allele would do constitutively.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "KIF4 is involved in the poly (ADP-ribose) polymerase (PARP) signaling pathway, and the mutation (R728Q) strengthened its affinity with PARP1 through elongation of the KIF4 coiled-coil domain."
    explanation: The opposite move - tighter binding, which on the same biochemistry lowers PARP1 activity.
  - reference: PMID:36482480
    reference_title: "KIF4 regulates neuronal morphology and seizure susceptibility via the PARP1 signaling pathway."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice"
    explanation: >-
      Confirms the direction for R728Q: the lesion is too little PARP1 activity, since raising
      it rescues.
  proposed_experiments:
  - experiment_id: exp_mrx100_parp1_activity_by_allele_class
    name: PARP1 activity in neurons carrying loss-of-function versus R728Q KIF4A alleles
    description: >-
      Measure PARP1 activity, by poly-ADP-ribose immunoblot and an activity assay, in
      iPSC-derived cortical neurons from a carrier of a splice-disrupting KIF4A allele, from an
      R728Q carrier, and from isogenic controls, at baseline and after depolarisation. Read out
      TrkB and KCC2 levels and intracellular chloride in the same cells, and test whether NAD
      supplementation moves each genotype toward or away from control.
    would_support:
    - pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption
    supporting_outcome:
    - >-
      Both allele classes displace PARP1 activity from the control range, in opposite
      directions, and both show TrkB-KCC2 abnormality - which would make PARP1 dysregulation
      per se the shared lesion and put the whole allelic series on this node.
    would_refute:
    - pathophysiology#PARP1-TrkB-KCC2 Signalling Disruption
    refuting_outcome:
    - >-
      Loss-of-function neurons have normal PARP1 activity and normal TrkB-KCC2 levels while
      R728Q neurons are abnormal - which would confine this node to R728Q and leave the
      loss-of-function alleles needing a different mechanism, most likely the mitotic one.
- discussion_id: kif4a_mitotic_arm_unproven
  kind: KNOWLEDGE_GAP
  prompt: >-
    Do KIF4A variants cause the reported cortical and midline brain malformations through a
    neural progenitor proliferation defect, or by some other route?
  attaches_to:
  - pathophysiology#Impaired Chromosome Condensation and Midzone Assembly
  - pathophysiology#Cortical and Midline Brain Malformation
  rationale: >-
    The mitotic arm of this entry is built entirely from cell biology plus clinical
    observation, with nothing joining them. KIF4A demonstrably compacts mitotic chromosomes
    with condensin and translocates PRC1 to build the midzone; patients demonstrably have
    polymicrogyria, microcephaly, hippocampal and callosal malformation and hydrocephalus. What
    is missing is any experiment showing a proliferation or division defect in a neural
    progenitor carrying a KIF4A variant. The knock-in mouse was not examined for one, and the
    only human molecular datum is a transcript measurement in a malformed fetal brain, which
    establishes depletion but not a mechanism.

    The alternative routes are not exotic. KIF4A transports the cell adhesion molecule L1CAM,
    and L1CAM variants cause X-linked hydrocephalus with aqueductal stenosis, so a transport
    defect could produce the same malformations without any mitotic involvement. Migration
    rather than proliferation is also a candidate, since periventricular nodular heterotopia
    was reported alongside the polymicrogyria.

    Until one of these is tested, the edge from the mitotic node to the malformation node is
    drawn with unknown intermediates, and the hypothesis group is EMERGING rather than
    ALTERNATIVE.
  evidence:
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "qPCR confirmed a significant reduction of KIF4A mRNA in brain tissue of the affected fetus (12%) compared to FFPE brain tissue of an age‐matched control."
    explanation: >-
      The only human molecular measurement in a malformed KIF4A brain. Directness is INDIRECT
      because it shows the transcript was depleted, not that division was impaired.
  - reference: PMID:34346154
    reference_title: "Expanding the KIF4A-associated phenotype."
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: "KIF4A motor activity allows for the anterograde transport of the cell adhesion molecule L1 (L1CAM; Peretti et al., 2002)."
    explanation: >-
      The competing route. L1CAM variants cause X-linked hydrocephalus, so a transport defect
      could account for the same malformations. Directness is INDIRECT because it names an
      alternative mechanism rather than bearing on the mitotic one.
  - reference: PMID:23166350
    reference_title: "Mitotic chromosomes are compacted laterally by KIF4 and condensin and axially by topoisomerase IIα."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms"
    explanation: >-
      The mitotic function is real and well demonstrated; directness is INDIRECT because the
      work was done in dividing cells generally, not in neural progenitors and not in a
      KIF4A-variant background.
  proposed_experiments:
  - experiment_id: exp_mrx100_progenitor_division_in_organoids
    name: Neural progenitor division in KIF4A-variant cortical organoids
    description: >-
      Generate dorsal forebrain organoids from iPSCs carrying a loss-of-function KIF4A allele
      and isogenic corrected controls, and quantify mitotic index, spindle and midzone
      morphology, chromosome condensation, cytokinesis failure and binucleation in apical and
      basal progenitors, together with ventricular zone thickness and cortical plate
      organisation over time. Include an L1CAM-transport readout in the same material so the
      two candidate routes are tested side by side rather than sequentially.
    would_support:
    - pathophysiology#Impaired Chromosome Condensation and Midzone Assembly
    supporting_outcome:
    - >-
      Variant organoids show impaired condensation, midzone defects or cytokinesis failure in
      progenitors with a reduced progenitor pool and disorganised cortical plate - which would
      convert the mitotic arm from EMERGING to a demonstrated mechanism and explain the
      malformation end of the spectrum.
    would_refute:
    - pathophysiology#Impaired Chromosome Condensation and Midzone Assembly
    refuting_outcome:
    - >-
      Progenitor division is normal while L1CAM transport or neuronal migration is impaired -
      which would move the malformation node onto a transport or migration mechanism and remove
      the mitotic arm from the human disease.

notes: >-
  Scope decisions worth stating explicitly.

  The dental phenotype is not curated here. Two brothers with KIF4A variants had taurodontism,
  microdontia and dens invaginatus with no developmental delay or intellectual disability, and
  ClinGen's expert panel assigned them to a separate disease entity under its lumping and
  splitting criteria. This entry follows that split.

  The brain malformation phenotype is curated here even though MONDO:0010488 sits under
  non-syndromic X-linked intellectual disability. The alleles are the same gene and, in some
  cases, the same class, and a reader who found only isolated intellectual disability in this
  entry would be misled about what a KIF4A variant can mean. The tension between the term and
  the phenotype is recorded rather than resolved, and ClinGen's own choice of a broader entity
  name - complex neurodevelopmental disorder with or without congenital anomalies - is the same
  observation from the other direction.

  The founding paper reports two genes, KIF4A and KIF5C, and only the KIF4A results are used
  here. The KIF5C finding in that paper concerns excitatory synapses in a patient with severe
  intellectual disability, microcephaly and cortical malformation, and attributing it to KIF4A
  would be a straightforward misreading of a multi-gene report.

  Renal and urinary tract anomalies, congenital lymphedema, structural eye anomalies and
  hearing loss were each reported in single patients or one sibling pair at the severe end of
  the 2021 series. They are not curated as phenotypes because each rests on one or two patients
  within a cohort assembled genotype-first from congenital anomaly presentations, which is the
  ascertainment most likely to overstate them. Strabismus is curated, and the distinction is
  deliberate: it was present in all four affected males of a separate family reported for its
  phenotype, whereas Peters anomaly, microphthalmia, leukoma and macular coloboma are
  single-patient findings inside the genotype-first cohort. The exclusion rationale is about
  ascertainment, not about the organ system.

📚

References & Deep Research

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Create: Intellectual Disability X-linked 100 (MRX100, KIF4A) · 2026-09-01T01:09:13Z · View source

De novo curation of MRX100 (MONDO:0010488, KIF4A) as a kb/disorders Disease entry. entry_type decision: DISEASE rather than a has_subtypes entry on Non-Syndromic_X-Linked_Intellectual_Disability. Two reasons. KIF4A carries a gene-specific published molecular chain (KIF4-PARP1-TrkB-KCC2 to chloride homeostasis and seizure threshold, plus dendrite and spine morphology) that is more mechanism than any of the eight MRX subtype blocks in the parent entry hold, and it has a knock-in mouse of its own; and the reported phenotype now includes epilepsy, polymicrogyria, microcephaly and hydrocephalus, so filing it under a parent whose defining feature is the absence of such features would record something the literature no longer supports. The parent entry is named in parents:. Two mechanistic_hypotheses: kif4a_synaptic_ei_imbalance (CANONICAL) and kif4a_mitotic_neurogenesis (EMERGING, because no KIF4A model has been shown to have a progenitor proliferation defect, so its edge to the malformation node carries unknown intermediates). The entry is calibrated to ClinGen's Limited classification throughout, and cites the ClinGen record for two things: the classification itself and the lumping-and-splitting decision that assigns the KIF4A dental phenotype (taurodontism, microdontia, dens invaginatus, no developmental delay) to a separate disease entity, which is respected here. One curatorial finding recorded as a KNOWLEDGE_GAP discussion: loss of KIF4 derepresses PARP1 (its C-terminal module suppresses PARP-1), while the R728Q substitution binds PARP1 harder and impairs its activity, which is why NAD rescues those mice. The two reported allele classes therefore push PARP1 in opposite directions while producing overlapping phenotypes, and the literature does not reconcile them. A second KNOWLEDGE_GAP covers the unproven mitotic arm, including the competing L1CAM-transport route. Named Entity Confusion controls: the founding paper reports KIF4A and KIF5C together and only KIF4A results are used, which is stated in notes; the dental phenotype is excluded per ClinGen; single-patient renal, lymphatic, ocular and hearing findings from the genotype-first 2021 series are not curated as phenotypes because that cohort's ascertainment would overstate them, and the same reasoning sets the Ventriculomegaly band at OCCASIONAL rather than the FREQUENT its within-series 4/11 would give. Antiseizure medication and developmental support are curated with no evidence item and an explicit notes line saying why, since no KIF4A report describes a regimen or an outcome. Gates: just validate exit 0 (58/58 snippets verified), validate-terms exit 0, check-duplicate-keys, check-entity-refs, check-snippet-length, check-title-snippets, check-snippet-grading, check-environmental-evidence, check-folded-hyphens all exit 0. Deep research: falcon report, just preflight-dr PASS (KIF4A mentioned 61 times); the report's own reference validation flagged DOI:10.1083/jcb.202208108 as unresolved, so that paper is cited here by its PMID (36482480) with snippets verified against the cached full text.

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 17 citations 2026-08-31T17:40:28.855259

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Intellectual disability, X-linked 100 (KIF4A-related non-syndromic X-linked intellectual disability, MRX100)
MONDO ID: MONDO:0010488 (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Intellectual disability, X-linked 100 (KIF4A-related non-syndromic X-linked intellectual disability, MRX100) covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Present this section as an ordered causal chain first, then the detail below. Open with a numbered sequence of mechanistic steps running from the initiating lesion (mutation, exposure, infection) to the clinical manifestation, one step per line, each naming what it causes next. State the causal verb explicitly ("leads to", "results in") and say where a step is inferred rather than demonstrated. Where the mechanism branches, show the branch. The categories below are a checklist of what to cover within those steps, not the organizing structure — a step may draw on several of them, and a category may contribute to several steps.

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

KIF4A-related X-linked intellectual disability (MRX100): disease-characteristics report

Executive summary and evidence limits

Intellectual disability, X-linked 100 (MRX100) is an ultra-rare, predominantly male neurodevelopmental disorder caused by hemizygous variants in KIF4A, an X-chromosomal kinesin/chromokinesin gene. The core phenotype is childhood-onset developmental delay or intellectual disability, variably accompanied by epilepsy, speech and motor delay, microcephaly, behavioral abnormalities, and structural brain malformations. More severe alleles/cases expand the phenotype to hydrocephalus, polymicrogyria, heterotopia, hydranencephaly, and congenital eye, dental, renal/urinary, lymphatic, or limb anomalies. The label “non-syndromic” therefore describes the founding family better than the full contemporary phenotypic spectrum. Open Targets links MONDO:0010488 to KIF4A with five evidence records and an association score of 0.6245. (OpenTargets Search: intellectual disability, X-linked 100-KIF4A, willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 7-10)

The evidence base remains small: a disease-defining family reported in 2014, a heterogeneous 11-male series in 2021, and a subsequent R728Q case studied mechanistically in mice. Consequently, prevalence, penetrance in females, survival, robust phenotype frequencies, and genotype–phenotype correlations cannot yet be estimated reliably. The 2021 authors explicitly cautioned that their reported variants remained VUS under strict ACMG criteria, notwithstanding phenotype and segregation evidence. (kalantari2021expandingthekif4a pages 7-10)

Evidence domain	Finding	Evidence type/model	Quantitative detail	Source date/PMID/DOI	Confidence/caveat
Disease-gene association	KIF4A is the principal gene associated with MONDO:0010488, intellectual disability, X-linked 100	Aggregated disease-target resource integrating literature/clinical variant evidence	Open Targets association score 0.6245; 5 evidence items linked to KIF4A	Open Targets, accessed via context for MONDO_0010488 (OpenTargets Search: intellectual disability, X-linked 100-KIF4A)	High for disease-gene linkage; resource-level aggregation, not a primary clinical description
Founding human clinical report	Original MRX100/XLID family showed X-linked recessive neurodevelopmental disease with mild-moderate intellectual disability and epilepsy in multiple males	Human clinical genetics; multigenerational family	5 affected males across 3 generations; 4/5 had epilepsy with onset in late childhood/adolescence; 3 carrier females identified; 2 unaffected males lacked the variant	2014; J Med Genet; DOI: 10.1136/jmedgenet-2013-102182 (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 2-3)	High; founding disease-defining family
Founding causal variant	The founding family carried a splice-disrupting in-frame indel causing exon 15 skipping and reduced KIF4A expression	Human molecular genetics + patient RNA/protein studies	NM_012310.4:c.1489-8_1490delins10; ~50% reduced KIF4A expression in patient cell lines; truncated/lower-molecular-weight product reported	2014; J Med Genet; DOI: 10.1136/jmedgenet-2013-102182 (willemsen2014involvementofthe pages 3-4)	High for variant effect in that family; exact ACMG terminology not provided in the 2014 paper
Severe sporadic case in 2014 study	A separate female case broadened severity toward cortical malformation, severe developmental delay, and early-onset seizures	Human sporadic case from ID cohort	1 female from series of 100 ID patients; seizures from 6 months; walked independently at 9-10 years; secondary microcephaly; absent speech; frontal cortical malformation	2014; J Med Genet; DOI: 10.1136/jmedgenet-2013-102182 (willemsen2014involvementofthe pages 3-4)	Moderate; single case and causal attribution is less canonical than the family report
Expanded phenotype cohort	KIF4A-associated phenotype expanded beyond non-syndromic ID to epilepsy, hydrocephalus, polymicrogyria, heterotopia, eye/dental/renal anomalies, and severe brain malformations	Human multicenter case series	11 male patients total; 10 missense variants and 1 splice variant; included sibling sets; epilepsy reported in 4 patients; imaging included ventricular dilatation, polymicrogyria, heterotopia, hydranencephaly	2021; Am J Med Genet A; DOI: 10.1002/ajmg.a.62443 (kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-6, kalantari2021expandingthekif4a pages 6-7)	Moderate-high for phenotypic expansion; heterogeneous ascertainment
Variant interpretation caveat	Despite compelling phenotype overlap, all 2021 variants were considered VUS under strict ACMG criteria	Human clinical variant interpretation	11 male patients; all reported variants classified as VUS by strict ACMG framework in that paper	2021; Am J Med Genet A; DOI: 10.1002/ajmg.a.62443 (kalantari2021expandingthekif4a pages 7-10)	High for the caveat itself; important limitation when populating knowledge bases
Synaptic mechanism linked to ID	KIF4A loss/downregulation disrupts excitatory/inhibitory synaptic balance, a plausible proximal mechanism for cognitive/epileptic phenotypes	Experimental neurobiology in primary rat hippocampal neurons	Kif4a knockdown decreased mIPSC frequency and altered mEPSCs (decreased amplitude, increased frequency)	2014; J Med Genet; DOI: 10.1136/jmedgenet-2013-102182 (willemsen2014involvementofthe pages 6-7, willemsen2014involvementofthe pages 4-6)	Moderate-high; strong cellular mechanism but not yet direct proof for every human variant
Human 2022 mechanistic extension	A patient KIF4A missense variant R728Q was linked to global developmental delay, severe intellectual disability, and intractable seizures	Human case plus mechanistic follow-up	Variant: R728Q in exon 20/coiled-coil region; patient pedigree included carrier females; patient MRI described as unremarkable in supplementary material excerpt	2022; J Cell Biol; DOI: 10.1083/jcb.202208108 (wan2022kif4regulatesneuronal pages 1-2, wan2022kif4regulatesneuronal pages 24-28)	Moderate; single-family/case evidence but followed by detailed modeling
Knock-in mouse disease model	The R728Q-equivalent Kif4 mutant mouse recapitulated developmental delay, smaller brain/hippocampus, cognitive deficits, anxiety-like behavior, and marked seizure susceptibility	Knock-in/engineered mouse model	Male offspring underrepresented (~31% observed vs 50% expected); increased fetal demise (~26% vs 7% WT); lower weights P3-P14; after PTZ 11/15 mutants reached stage 5 seizures and 3 died; ~10-fold EEG power increase post-PTZ	2022; J Cell Biol; DOI: 10.1083/jcb.202208108 (wan2022kif4regulatesneuronal pages 4-5, wan2022kif4regulatesneuronal pages 2-4)	High for model phenotype; animal model may not capture full human allelic spectrum
PARP1-TrkB-KCC2 pathway	The 2022 study supports a mechanistic chain in which mutant KIF4 alters PARP1 signaling, increases TrkB, lowers KCC2, perturbs chloride homeostasis, and increases seizure susceptibility	Mouse + cultured neuron mechanistic studies	Mutant KIF4 showed stronger PARP1 binding; KCC2 significantly reduced in motor cortex/hippocampus; intracellular chloride increased; CA3 pyramidal neurons showed hyper-branching/spine abnormalities	2022; J Cell Biol; DOI: 10.1083/jcb.202208108 (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 13-15, wan2022kif4regulatesneuronal pages 1-2)	Moderate-high; some links are mechanistically strong, but pathway ordering remains partly model-based
Preclinical rescue	Enhancing PARP1-related signaling rescued key mutant phenotypes, suggesting therapeutic tractability but not a clinical therapy	Preclinical intervention in cultured neurons/mice	NAD supplementation rescued seizure susceptibility; neuronal survival rescued by NAD or high KCl under stress conditions; statistical significance often P < 0.0001 in cited experiments	2022; J Cell Biol; DOI: 10.1083/jcb.202208108 (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 28-31)	Moderate; preclinical only, not disease-specific standard of care
2023 neural biology update	KIF4A is expressed in adult neurons and Schwann cells and is induced after peripheral nerve injury, extending biology beyond development	Rat/human tissue study, preprint	Schwann-cell KIF4A mRNA ~6-fold higher in proliferating vs quiescent cultures; DRG neuron Kif4a up ~2-fold to ~2.7-fold after injury; distal stump up ~12-13-fold at 7 dpi	2023; bioRxiv preprint; DOI: 10.1101/2023.05.21.541636 (correia2023unexpectedkif4afunctions pages 2-5, correia2023unexpectedkif4afunctions pages 10-13, correia2023unexpectedkif4afunctions pages 5-7, correia2023unexpectedkif4afunctions pages 1-2)	Moderate; biologically relevant but preprint and not disease-specific to MRX100
2024 neural injury relevance	Post-stroke rat brain re-expresses KIF4 in peri-infarct tissue, consistent with broader roles in adult neural plasticity/repair	Peer-reviewed rat stroke model	kif4 mRNA in juvenile brain ~2.47-3.30; selective re-expression in penumbra at day 3 post-stroke; KIF4 localized in neuronal precursor cells, glia, and NeuN+ neurons	2024; Brain Pathology; DOI: 10.1111/bpa.13232 (ruscu2024thepost‐strokeyoung pages 7-8)	Moderate; not an MRX100 study, but relevant for KIF4A functional interpretation
Clinical implementation / trials	No disease-specific interventional clinical trial for KIF4A-related MRX100 was identified in the trial searches performed	Trial registry search + literature review	0 relevant registered interventional trials retrieved for KIF4A/MRX100	Trial search status in current evidence synthesis (OpenTargets Search: intellectual disability, X-linked 100-KIF4A)	High for current search result; always subject to registry update and search-scope limitations

Table: This table summarizes the highest-confidence disease, mechanism, model, and translational evidence for KIF4A-related X-linked intellectual disability (MRX100). It is useful for quickly separating well-supported findings from important caveats such as ACMG VUS classification and preclinical-only therapeutic signals.

1. Disease information

Definition and identifiers

Preferred name: intellectual disability, X-linked 100.
Synonyms: MRX100; XLID100; KIF4A-related intellectual disability; KIF4A-related neurodevelopmental disorder; KIF4A-associated disorder. “KIF4A-related non-syndromic XLID” is narrower and potentially misleading for patients with malformations.
MONDO: MONDO:0010488.
Causal gene: KIF4A, kinesin family member 4A; OMIM gene 300521; Ensembl ENSG00000090889. (OpenTargets Search: intellectual disability, X-linked 100-KIF4A, willemsen2014involvementofthe pages 1-2)
Disease OMIM: commonly catalogued as MRX100 / intellectual disability, X-linked 100; the exact disease-number field should be verified directly against the current licensed OMIM record before database ingestion.
Orphanet: no disorder-specific Orpha number was established from the retrieved evidence.
ICD-10/ICD-11/MeSH: no KIF4A-specific code. Coding is phenotype-based—for example, intellectual developmental disorder and, when applicable, epilepsy, microcephaly, or congenital brain malformation. A generic code must not be treated as a molecular diagnosis.

The disease description is an aggregated disease-level synthesis of pedigrees, case reports/series, patient-derived molecular studies, and experimental models—not an EHR-derived population estimate. The founding study sequenced X-chromosome exons in more than 200 XLID families; the severe female was drawn from a separate series of 100 individuals with ID. (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 2-3)

Key primary sources

Willemsen et al., Journal of Medical Genetics, May 2014; PMID 24812067; DOI/URL: https://doi.org/10.1136/jmedgenet-2013-102182. The paper’s central conclusion was that KIF4A/KIF5C variants implicate kinesin-dependent synaptic function in ID. (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 1-2)
Kalantari et al., American Journal of Medical Genetics A, online August 2021; PMID 34346154; DOI/URL: https://doi.org/10.1002/ajmg.a.62443. Abstract quote: “We expand the phenotype associated with KIF4A variants from developmental delay and intellectual disability with or without epilepsy to a congenital anomaly phenotype with hydrocephalus and various brain anomalies.” (kalantari2021expandingthekif4a pages 7-10)
Wan et al., Journal of Cell Biology, December 2022/2023 volume; DOI/URL: https://doi.org/10.1083/jcb.202208108. Abstract wording states that the study revealed a mechanism connecting KIF4-regulated chloride homeostasis and neuronal morphology to epilepsy susceptibility. (wan2022kif4regulatesneuronal pages 1-2)

2. Etiology, risk, protection, and gene–environment interaction

Causal factor

The primary cause is a germline KIF4A sequence variant affecting KIF4A dosage, splicing, motor-domain function, or protein regulation. The founding NM_012310.4:c.1489-8_1490delins10 allele disrupts the exon-15 acceptor, produces exon skipping and a shortened protein, and reduced KIF4A abundance by approximately 50% in patient cells. (willemsen2014involvementofthe pages 3-4)

Genetic risk

Hemizygous males carrying a functionally damaging X-linked allele have the greatest established risk. Reported examples include c.763G>A (p.Asp255Asn), c.794G>T (p.Arg265Leu), c.1616T>C (p.Leu539Pro), c.1745T>A (p.Leu582His), c.2266A>C (p.Ser756Arg), c.2558G>T (p.Arg853Leu), c.3299G>A (p.Arg1100Lys), c.1674+1G>A, the founding complex splice indel, and p.Arg728Gln (R728Q). Several were maternally inherited; p.Leu539Pro was reported de novo. Transcript/version normalization is essential before clinical reuse. (kalantari2021expandingthekif4a pages 6-6, kalantari2021expandingthekif4a pages 6-7, wan2022kif4regulatesneuronal pages 1-2)

Family history consistent with X-linked transmission increases prior probability. The founding pedigree contained five affected males over three generations, three carrier females, and two unaffected males without the variant. Linkage was interpreted as X-linked recessive with complete penetrance among the informative males, but this single pedigree cannot establish universal penetrance. (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 2-3)

Environmental, infectious, and lifestyle risk

No toxin, infection, diet, occupation, smoking, alcohol exposure, or other environmental factor has been shown to cause MRX100. Maternal age, paternal age, consanguinity, and lifestyle are not established disease-specific risk factors. Consanguinity is not mechanistically required for an X-linked disorder.

Protective factors and gene–environment interaction

No validated protective human allele or environmental exposure is known. NAD supplementation rescued seizure susceptibility in an R728Q-equivalent mouse, but this is preclinical pathway rescue, not evidence that dietary NAD or supplements protect humans. Seizure-provoking exposures may modify manifestations as in other epilepsies, but no KIF4A-specific gene–environment interaction has been demonstrated. (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 28-31)

3. Phenotypes

The frequencies below are study-specific rather than population estimates.

Developmental delay / intellectual disability — core feature; HP:0012758 / HP:0001249. Onset is developmental/childhood; severity ranges from mild–moderate in the founding males to severe. The founding males could use simple sentences, whereas a severe female had absent speech and walked only at 9–10 years. Functional effect includes impaired learning, communication, independence, education, and adaptive behavior. (willemsen2014involvementofthe pages 3-4)
Speech/language delay or absent speech — HP:0000750 / HP:0001344. Childhood onset; variable and generally persistent. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 6-7)
Delayed motor milestones — HP:0001270, with delayed walking HP:0002060. Examples include head control at 5–6 months and walking after age 3 years; the severe female walked at 9–10 years. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 6-6)
Epilepsy/seizures — HP:0001250. Four of five founding males had complex-partial/generalized seizures beginning in late childhood or adolescence; the severe female developed seizures at 6 months. The 2021 series included epilepsy in four patients, including a drug-refractory case with multifocal discharges. Frequency and onset are therefore allele-dependent and variable. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-6)
Microcephaly/secondary microcephaly — HP:0000252. Head size ranged from small/low-normal in the founding family to below −2.5 SD in the severe female. (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 2-3)
Brain malformations — polymicrogyria HP:0002126, perisylvian polymicrogyria HP:0006821, heterotopia HP:0002282, ventriculomegaly HP:0002119, hydrocephalus HP:0000238, cerebral atrophy HP:0002059, and hydranencephaly HP:0002324. Imaging can also be normal, indicating marked variable expressivity. (kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-6, kalantari2021expandingthekif4a pages 6-7, wan2022kif4regulatesneuronal pages 24-28)
Behavioral abnormalities — autism spectrum features HP:0000729, self-injurious behavior HP:0100716, and possible anxiety HP:0000739. Severe self-injury was described in one patient; autism occurred in part of the expanded series. Anxiety is supported principally by the mouse model and should not be treated as an established common human feature. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 6-7, wan2022kif4regulatesneuronal pages 4-5)
Congenital anomalies, variable — Peters anomaly/anterior-segment eye anomaly, small hands/feet, dental anomalies, renal/urinary-tract anomalies, congenital lymphedema, and other skeletal or limb findings. Suggested terms include HP:0000659 (Peters anomaly), HP:0001156 (brachydactyly), HP:0000691 (abnormality of dental morphology), HP:0012210 (abnormal renal morphology), and HP:0001004 (lymphedema). These are not obligatory features. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-7)

No disease-specific EQ-5D, SF-36, PROMIS, or caregiver-burden study was identified. Quality-of-life impact must therefore be inferred from developmental dependence, communication limitations, epilepsy, behavioral dysregulation, and congenital complications rather than quantified with MRX100-specific instruments.

4. Genetic and molecular information

KIF4A encodes an N-kinesin with an N-terminal ATP-dependent microtubule motor domain, central α-helical/coiled-coil stalk, and C-terminal cargo/regulatory tail. It functions in intracellular transport, chromosome condensation, spindle/midzone organization, cytokinesis, neuronal survival, morphology, and synaptic physiology. (willemsen2014involvementofthe pages 6-7, kalantari2021expandingthekif4a pages 1-2)

Variant classes and interpretation

Reported classes include missense, essential splice-site, and complex splice-region indels. The founding allele has direct RNA/protein functional support. R728Q increases predicted coiled-coil probability from 0.45 to 0.92 and strengthens PARP1 binding in experimental assays. By contrast, the 10 missense and one splice variant in the 2021 series were all classified as VUS under strict ACMG criteria; individual ClinVar assertions may evolve and must be checked by variant, transcript, genome build, and review status. (kalantari2021expandingthekif4a pages 7-10, willemsen2014involvementofthe pages 3-4, wan2022kif4regulatesneuronal pages 2-4)

The variants are presumed or demonstrated germline, not somatic. No MRX100-specific somatic mosaic series, modifier gene, protective allele, reproducible epigenetic signature, repeat expansion, aneuploidy, or recurrent pathogenic translocation is established. Xq13.1 duplications involving KIF4A have been associated with a broader “floppy infant” phenotype, but dosage CNVs should not automatically be equated with sequence-variant MRX100. (liu2025kif4aindisease pages 9-10)

Population allele frequencies were not provided in the retrieved primary excerpts. A candidate disease allele should be absent or exceptionally rare in an ancestry-matched resource such as gnomAD, but database absence alone is not proof of pathogenicity.

5. Environmental information

MRX100 is a Mendelian neurodevelopmental disorder; no causal toxicant, radiation exposure, pollutant, occupational exposure, lifestyle behavior, or infectious agent has been identified. Environmental measures cannot prevent the inherited molecular lesion. General avoidance of seizure triggers and good prenatal/child health remain supportive practices, not disease-specific etiologic interventions.

6. Mechanism and pathophysiology

Ordered causal chain

A hemizygous damaging KIF4A variant leads to altered splicing/protein abundance or abnormal motor/regulatory protein behavior. The founding allele’s exon skipping and approximately 50% reduction are demonstrated; effects of many missense VUS remain inferred. (willemsen2014involvementofthe pages 3-4)
Altered KIF4A leads to disturbed microtubule-dependent cargo handling and/or nuclear chromokinesin regulation, including abnormal interaction with PARP1; this is demonstrated for R728Q and inferred for some other alleles. (willemsen2014involvementofthe pages 6-7, wan2022kif4regulatesneuronal pages 1-2)
Branch A—developmental transport/cytoskeleton: KIF4A dysfunction is inferred to disturb neuronal polarization, axon/dendrite formation, adhesion-cargo trafficking such as L1CAM, and synapse development, resulting in aberrant cortical organization and connectivity. (willemsen2014involvementofthe pages 6-7, kalantari2021expandingthekif4a pages 1-2)
Branch B—PARP1 signaling: R728Q strengthens KIF4–PARP1 binding and suppresses appropriate PARP1/PAR signaling, leading to increased TrkB, reduced KCC2, and abnormal neuronal chloride homeostasis. (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 1-2)
Reduced KCC2 and elevated intracellular chloride lead to impaired maturation of inhibitory GABAergic signaling, while KIF4A depletion independently alters miniature excitatory and inhibitory currents, resulting in excitation/inhibition imbalance. (willemsen2014involvementofthe pages 6-7, willemsen2014involvementofthe pages 4-6, wan2022kif4regulatesneuronal pages 13-15)
Circuit imbalance plus aberrant dendritic branching/spines leads to learning impairment, intellectual disability, anxiety-like behavior, and lower seizure threshold; this is demonstrated in mice and biologically consistent with human ID/epilepsy. (wan2022kif4regulatesneuronal pages 1-2, wan2022kif4regulatesneuronal pages 4-5)
Branch C—cell division: disruption of KIF4A–PRC1 spindle-midzone/cytokinesis functions may contribute to congenital brain and multi-organ anomalies, but normal mitosis in founding-family lymphocytes means this disease link remains incompletely demonstrated. (willemsen2014involvementofthe pages 6-7, kalantari2021expandingthekif4a pages 1-2)

Molecular and cellular detail

In rat hippocampal neurons, Kif4a knockdown decreased mEPSC amplitude, increased mEPSC frequency, and decreased mIPSC frequency without changing mIPSC amplitude or current kinetics. This supports altered synapse number/release rather than a generalized postsynaptic receptor-composition defect. (willemsen2014involvementofthe pages 4-6)

R728Q mice had hyperbranched CA3 pyramidal neurons, abnormal dendritic spines, reduced KCC2 in hippocampus and motor cortex, and elevated intracellular chloride. NAD restored pathway activity and seizure susceptibility, supplying experimental—not clinical—causal support for the PARP1–TrkB–KCC2 branch. (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 1-2, wan2022kif4regulatesneuronal pages 28-31)

Suggested GO biological processes: microtubule-based movement GO:0007018; microtubule-based transport GO:0099111; chromosome segregation GO:0007059; cytokinesis GO:0000910; axon development GO:0061564; dendrite development GO:0016358; synapse organization GO:0050808; regulation of membrane potential GO:0042391; neuronal action-potential regulation and chloride transport. Suggested cellular components include microtubule cytoskeleton GO:0015630, spindle midzone GO:0051233, nucleus GO:0005634, axon GO:0030424, dendrite GO:0030425, and synapse GO:0045202.

Suggested Cell Ontology terms: neuron CL:0000540; pyramidal neuron CL:0000598; hippocampal neuron; cortical neuron CL:0002609; GABAergic neuron CL:0000617; glutamatergic neuron CL:0000679; neural progenitor cell CL:0011020; Schwann cell CL:0002573. Cell-type specificity in human MRX100 tissue has not been established by single-cell or spatial profiling.

No disease-specific human transcriptomic, proteomic, metabolomic, lipidomic, epigenomic, single-cell, spatial-transcriptomic, organoid, or CRISPR-screen signature was identified. The mechanistic omics gap is substantial.

7. Anatomical structures affected

The central nervous system, especially cerebral cortex and hippocampal circuits, is primary. Suggested anatomy terms include brain UBERON:0000955, cerebral cortex UBERON:0000956, frontal cortex, hippocampal formation UBERON:0002421, lateral ventricle UBERON:0002285, and corticospinal/pyramidal tracts. Findings include cortical atrophy, shallow sulci/reduced gyri, polymicrogyria, heterotopia, ventriculomegaly/hydrocephalus, and hypoplastic pyramidal tracts. Disease lateralization is not established; bilateral polymicrogyria can occur. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-6)

Secondary variable involvement includes eye/anterior segment, teeth, kidney/urinary tract, lymphatic system, hands/feet, and skeleton. Subcellular sites are nucleus/chromatin and spindle during division, plus neuronal microtubules, axons, dendrites, and synapses. (kalantari2021expandingthekif4a pages 7-10, willemsen2014involvementofthe pages 6-7, kalantari2021expandingthekif4a pages 1-2)

8. Temporal development and natural history

Onset is congenital/developmental but may first be recognized when milestones are delayed. Epilepsy ranges from infancy (6 months in a severe case) to late childhood/adolescence in the founding family. Intellectual and adaptive impairment appears chronic and lifelong. There is no validated staging system, remission pattern, or longitudinal natural-history curve. (willemsen2014involvementofthe pages 3-4)

Structural malformations arise prenatally, making corticogenesis a likely critical window. Synaptic maturation and childhood learning remain potential intervention windows, but this is biologically inferred rather than proven in patients. Available reports do not establish a progressive neurodegenerative course; “stable neurodevelopmental disability with variable epilepsy” is more defensible, while acknowledging inadequate longitudinal data.

9. Inheritance and population

Inheritance is principally X-linked recessive: hemizygous males are predominantly affected, while heterozygous females may be unaffected carriers or variably affected owing to X-inactivation or allele-specific effects. Maternal inheritance and at least one de novo event have been documented. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 6-6)

For a carrier mother, each pregnancy has a 50% probability of transmitting the allele; conventionally, each son has a 50% risk of being affected and each daughter a 50% risk of being a carrier, although female manifestations remain possible. Germline mosaicism cannot be excluded after an apparently de novo result. No anticipation, founder effect, population enrichment, carrier frequency, ethnic predisposition, or geographic concentration is established.

No prevalence or incidence estimate exists. Reported numbers are far too small and ascertainment-biased to calculate cases per 100,000. The observed male predominance follows X-linked biology, not a registry-derived sex ratio.

10. Diagnostics

Clinical evaluation

Evaluate developmental history, adaptive and cognitive function, speech/language, neurologic examination, growth and head circumference, behavior/autism, dysmorphology, vision, hearing, dentition, limbs, and renal/urinary findings. EEG is indicated for seizures or suspicious episodes. Brain MRI is appropriate with epilepsy, microcephaly, abnormal examination, regression, or severe delay; imaging may be normal and therefore cannot exclude MRX100. (kalantari2021expandingthekif4a pages 6-6, kalantari2021expandingthekif4a pages 6-7, wan2022kif4regulatesneuronal pages 24-28)

There is no diagnostic blood metabolite, enzyme assay, pathology specimen, proteomic marker, or KIF4A-specific clinical criterion. Diagnosis requires compatible phenotype plus molecular evidence interpreted under ACMG/AMP rules.

Genetic-testing strategy

First-line: trio exome or genome sequencing, or a comprehensive neurodevelopmental/XLID panel that includes KIF4A, with CNV calling.
Confirmatory: Sanger/orthogonal confirmation, maternal testing, segregation in informative relatives, and precise HGVS transcript/build annotation.
Splice variants: patient RNA analysis can demonstrate exon skipping; the founding allele shows the value of this approach. Protein studies or research functional assays may help reclassify VUS. (willemsen2014involvementofthe pages 2-3, willemsen2014involvementofthe pages 3-4)
CMA: useful for genome-wide CNVs and differential diagnosis, but does not reliably detect small KIF4A sequence variants.
WGS: useful for noncoding splice variants, structural variants, and exome-negative disease. Karyotype/FISH are not routine for a suspected small sequence variant unless a chromosomal rearrangement is suspected.
Mitochondrial DNA and repeat-expansion tests are not KIF4A-specific; use only when the broader phenotype warrants them.

Differential diagnosis

Differentials include other XLID genes (ARX, SLC9A6, CASK, MECP2, IQSEC2, HUWE1), fragile X syndrome (FMR1), and kinesin/microtubule disorders such as KIF1A, KIF2A, KIF5C, KIF11, KIF14, KIF21B, DYNC1H1, TUBA1A, particularly when epilepsy or cortical malformation is prominent. The founding family had unrevealing karyotype, array, FMR1, ARX, and metabolic testing before KIF4A was identified. (willemsen2014involvementofthe pages 2-3)

Cascade testing is appropriate after a familial pathogenic/likely pathogenic variant is established. Population or newborn screening is not available.

11. Outcome and prognosis

There are no disease-specific survival curves, mortality rates, life-expectancy estimates, validated prognostic biomarkers, or quality-of-life scores. Adult affected males aged up to 53 years in the founding family show that survival into later adulthood is possible, but this does not define average life expectancy. (willemsen2014involvementofthe pages 2-3)

Long-term morbidity is driven by cognitive/adaptive disability, language impairment, dependence in daily living, epilepsy—including refractory epilepsy in some cases—and complications of major brain or congenital anomalies. Recovery to typical neurodevelopment is not reported. Prognosis likely correlates with developmental severity, seizure control, and burden of structural malformations, but sample sizes preclude validated prediction. (willemsen2014involvementofthe pages 3-4, kalantari2021expandingthekif4a pages 7-10, kalantari2021expandingthekif4a pages 6-6)

12. Treatment and current implementation

No KIF4A-directed treatment is approved, and no disease-specific interventional trial was identified. Current real-world care is multidisciplinary and phenotype-directed:

early developmental and educational intervention;
speech/language therapy, augmentative communication, occupational therapy, and physical therapy;
standard antiseizure medication selected by seizure type, EEG, comorbidity, and adverse-effect profile; drug resistance warrants specialist epilepsy evaluation;
behavioral/psychiatric and autism supports;
treatment of hydrocephalus or other structural complications by relevant specialists;
ophthalmologic, renal, dental, feeding/nutrition, and orthopedic care when indicated.

Suggested NCIt concepts include Developmental Therapy, Speech and Language Therapy, Occupational Therapy, Physical Therapy, Anticonvulsant Therapy, Genetic Counseling, and Ventriculoperitoneal Shunt Procedure where clinically indicated. Exact NCIt codes should be mapped against the current NCIt release.

The most specific experimental signal is NAD supplementation/PARP1-pathway restoration in R728Q mice, which rescued seizure susceptibility and aspects of neuronal morphology. It must not be extrapolated to human supplementation: optimal compound, dose, CNS exposure, developmental timing, long-term safety, and applicability across loss-of-function versus altered-binding alleles are unknown. (wan2022kif4regulatesneuronal pages 5-7, wan2022kif4regulatesneuronal pages 1-2, wan2022kif4regulatesneuronal pages 28-31)

Conversely, KIF4A inhibitors under oncology development are biologically inappropriate as presumptive MRX100 therapy and could worsen neuronal or mitotic function. A 2024 glioma study of WZ-3146 concerns tumor inhibition, not replacement of deficient KIF4A in neurodevelopmental disease. (liu2025researchprogressof pages 14-14)

13. Prevention

The condition cannot be prevented through vaccination, diet, lifestyle, or environmental remediation.

Primary prevention/family planning: genetic counseling; carrier testing; preimplantation genetic testing for a known familial variant; prenatal diagnosis by chorionic-villus sampling or amniocentesis after informed consent.
Secondary prevention: cascade testing and early molecular diagnosis can avoid a diagnostic odyssey and enable early developmental and epilepsy surveillance, but do not reverse prenatal malformation.
Tertiary prevention: optimize seizure control, communication, mobility, nutrition, safety, education, and management of hydrocephalus or organ-specific anomalies.

Prenatal or preimplantation interpretation should be based on a pathogenic/likely pathogenic familial variant, not an unresolved VUS without careful counseling.

14. Other species and natural disease

KIF4A/Kif4a is evolutionarily conserved in vertebrates. Relevant laboratory taxa are Homo sapiens (NCBI Taxon 9606), Mus musculus (10090), and Rattus norvegicus (10116). No well-established, naturally occurring KIF4A-associated veterinary syndrome, breed predisposition, zoonotic transmission, or cross-species infectious susceptibility was identified. This is a genetic intracellular-motor disorder and has no zoonotic potential.

Recent comparative work extends KIF4A biology beyond development. A 2023 rat/human-tissue preprint found adult neuronal and Schwann-cell expression; after peripheral nerve injury, DRG Kif4a rose approximately 2–2.7-fold and distal-stump expression approximately 12–13-fold at day 7, while proliferating Schwann cells expressed about sixfold more Kif4a mRNA than quiescent cells. This informs regeneration biology but does not establish an MRX100 treatment. (correia2023unexpectedkif4afunctions pages 2-5, correia2023unexpectedkif4afunctions pages 10-13)

A January 2024 rat stroke study found selective KIF4 re-expression in peri-infarct cortex at day 3, including NeuN-positive neurons, precursor cells, and glia. This supports an adult plasticity role but is not evidence about human MRX100 natural history. DOI: https://doi.org/10.1111/bpa.13232. (ruscu2024thepost‐strokeyoung pages 7-8)

15. Model organisms and experimental systems

R728Q knock-in mouse

The principal disease-oriented model is a male Kif4Mut/Y mouse engineered for the human R728Q coiled-coil variant. It showed increased fetal demise (approximately 26% versus 7% in wild type), male underrepresentation (31% rather than the expected 50%), prenatal/postnatal growth restriction, smaller brain and hippocampus, delayed developmental milestones, impaired spatial/object memory and fear conditioning, anxiety-like behavior, abnormal CA3 dendrites/spines, altered chloride homeostasis, and enhanced PTZ seizure susceptibility. After PTZ, 11/15 mutants reached stage-5 seizures and three died; EEG power increased approximately tenfold. (wan2022kif4regulatesneuronal pages 4-5, wan2022kif4regulatesneuronal pages 2-4)

Applications: allele mechanism, PARP1–TrkB–KCC2 biology, chloride homeostasis, synaptic development, cognition, seizure threshold, and preclinical rescue. Limitations: it models one altered-binding missense allele, not the founding exon-skipping allele or all motor-domain VUS; PTZ-provoked seizures are not identical to spontaneous human epilepsy; murine developmental and X-inactivation biology differ from humans.

Primary neuronal systems

Kif4a siRNA knockdown in primary rat hippocampal neurons provides a reduction-of-function model and demonstrates altered mEPSC/mIPSC properties. It is valuable for synaptic physiology but lacks human genetic background, cortical morphogenesis, systemic congenital phenotypes, and long-term behavior. (willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 4-6)

Injury/regeneration models

Rat sciatic-nerve crush/transection, cultured Schwann cells, and rat stroke models establish injury-induced KIF4A expression and glial/neuronal roles. They are relevant to general KIF4A biology but are not validated MRX100 phenocopies. (correia2023unexpectedkif4afunctions pages 2-5, correia2023unexpectedkif4afunctions pages 10-13, ruscu2024thepost‐strokeyoung pages 7-8)

No disease-specific zebrafish, Drosophila, C. elegans, human iPSC-neuron, cerebral-organoid, or humanized replacement model was identified in the retrieved literature. High-priority research needs are patient-derived iPSC cortical neurons/organoids, isogenic correction, quantitative motor/cargo assays, female X-inactivation studies, and direct comparison of truncating, splice, motor-domain, and coiled-coil alleles.

Overall expert assessment

The KIF4A–MRX100 relationship is credible, supported by X-linked segregation, a functionally validated splice defect, recurrent rare variants in similarly affected males, neuronal electrophysiology, and an allele-specific mouse model. However, the disorder should currently be represented as a KIF4A-related neurodevelopmental spectrum, not a uniformly non-syndromic ID entity. The strongest clinical facts are developmental impairment, variable epilepsy, and variably abnormal brain structure; the strongest mechanistic evidence concerns synaptic excitation/inhibition and the allele-specific PARP1–TrkB–KCC2/chloride pathway. Variant-level assertions require caution because much of the expanded allelic series remained VUS, and no epidemiologic, natural-history, or therapeutic trial infrastructure yet exists. (kalantari2021expandingthekif4a pages 7-10, willemsen2014involvementofthe pages 3-4, willemsen2014involvementofthe pages 4-6, wan2022kif4regulatesneuronal pages 1-2)

References

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(willemsen2014involvementofthe pages 3-4): Marjolein H Willemsen, Wei Ba, Willemijn M Wissink-Lindhout, Arjan P M de Brouwer, Stefan A Haas, Melanie Bienek, Hao Hu, Lisenka E L M Vissers, Hans van Bokhoven, Vera Kalscheuer, Nael Nadif Kasri, and Tjitske Kleefstra. Involvement of the kinesin family members kif4a and kif5c in intellectual disability and synaptic function. Journal of Medical Genetics, 51:487-494, May 2014. URL: https://doi.org/10.1136/jmedgenet-2013-102182, doi:10.1136/jmedgenet-2013-102182. This article has 118 citations and is from a domain leading peer-reviewed journal.
(kalantari2021expandingthekif4a pages 7-10): Silvia Kalantari, Colleen Carlston, Norah Alsaleh, Ghada M. H. Abdel‐Salam, Fowzan Alkuraya, Mitsuhiro Kato, Naomichi Matsumoto, Satoko Miyatake, Tatsuya Yamamoto, Lucas Fares‐Taie, Jean‐Michel Rozet, Nicolas Chassaing, Catherine Vincent‐Delorme, Anjeung Kang‐Bellin, Kirsty McWalter, Caleb Bupp, Emily Palen, Monisa D. Wagner, Marcello Niceta, Claudia Cesario, Roberta Milone, Julie Kaplan, Erin Wadman, William B. Dobyns, and Isabel Filges. Expanding the kif4a ‐associated phenotype. American Journal of Medical Genetics. Part a, 185:3728-3739, Aug 2021. URL: https://doi.org/10.1002/ajmg.a.62443, doi:10.1002/ajmg.a.62443. This article has 20 citations and is from a peer-reviewed journal.
(willemsen2014involvementofthe pages 2-3): Marjolein H Willemsen, Wei Ba, Willemijn M Wissink-Lindhout, Arjan P M de Brouwer, Stefan A Haas, Melanie Bienek, Hao Hu, Lisenka E L M Vissers, Hans van Bokhoven, Vera Kalscheuer, Nael Nadif Kasri, and Tjitske Kleefstra. Involvement of the kinesin family members kif4a and kif5c in intellectual disability and synaptic function. Journal of Medical Genetics, 51:487-494, May 2014. URL: https://doi.org/10.1136/jmedgenet-2013-102182, doi:10.1136/jmedgenet-2013-102182. This article has 118 citations and is from a domain leading peer-reviewed journal.
(kalantari2021expandingthekif4a pages 6-6): Silvia Kalantari, Colleen Carlston, Norah Alsaleh, Ghada M. H. Abdel‐Salam, Fowzan Alkuraya, Mitsuhiro Kato, Naomichi Matsumoto, Satoko Miyatake, Tatsuya Yamamoto, Lucas Fares‐Taie, Jean‐Michel Rozet, Nicolas Chassaing, Catherine Vincent‐Delorme, Anjeung Kang‐Bellin, Kirsty McWalter, Caleb Bupp, Emily Palen, Monisa D. Wagner, Marcello Niceta, Claudia Cesario, Roberta Milone, Julie Kaplan, Erin Wadman, William B. Dobyns, and Isabel Filges. Expanding the kif4a ‐associated phenotype. American Journal of Medical Genetics. Part a, 185:3728-3739, Aug 2021. URL: https://doi.org/10.1002/ajmg.a.62443, doi:10.1002/ajmg.a.62443. This article has 20 citations and is from a peer-reviewed journal.
(kalantari2021expandingthekif4a pages 6-7): Silvia Kalantari, Colleen Carlston, Norah Alsaleh, Ghada M. H. Abdel‐Salam, Fowzan Alkuraya, Mitsuhiro Kato, Naomichi Matsumoto, Satoko Miyatake, Tatsuya Yamamoto, Lucas Fares‐Taie, Jean‐Michel Rozet, Nicolas Chassaing, Catherine Vincent‐Delorme, Anjeung Kang‐Bellin, Kirsty McWalter, Caleb Bupp, Emily Palen, Monisa D. Wagner, Marcello Niceta, Claudia Cesario, Roberta Milone, Julie Kaplan, Erin Wadman, William B. Dobyns, and Isabel Filges. Expanding the kif4a ‐associated phenotype. American Journal of Medical Genetics. Part a, 185:3728-3739, Aug 2021. URL: https://doi.org/10.1002/ajmg.a.62443, doi:10.1002/ajmg.a.62443. This article has 20 citations and is from a peer-reviewed journal.
(willemsen2014involvementofthe pages 6-7): Marjolein H Willemsen, Wei Ba, Willemijn M Wissink-Lindhout, Arjan P M de Brouwer, Stefan A Haas, Melanie Bienek, Hao Hu, Lisenka E L M Vissers, Hans van Bokhoven, Vera Kalscheuer, Nael Nadif Kasri, and Tjitske Kleefstra. Involvement of the kinesin family members kif4a and kif5c in intellectual disability and synaptic function. Journal of Medical Genetics, 51:487-494, May 2014. URL: https://doi.org/10.1136/jmedgenet-2013-102182, doi:10.1136/jmedgenet-2013-102182. This article has 118 citations and is from a domain leading peer-reviewed journal.
(willemsen2014involvementofthe pages 4-6): Marjolein H Willemsen, Wei Ba, Willemijn M Wissink-Lindhout, Arjan P M de Brouwer, Stefan A Haas, Melanie Bienek, Hao Hu, Lisenka E L M Vissers, Hans van Bokhoven, Vera Kalscheuer, Nael Nadif Kasri, and Tjitske Kleefstra. Involvement of the kinesin family members kif4a and kif5c in intellectual disability and synaptic function. Journal of Medical Genetics, 51:487-494, May 2014. URL: https://doi.org/10.1136/jmedgenet-2013-102182, doi:10.1136/jmedgenet-2013-102182. This article has 118 citations and is from a domain leading peer-reviewed journal.
(wan2022kif4regulatesneuronal pages 1-2): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 24-28): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 4-5): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 2-4): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 5-7): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 13-15): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(wan2022kif4regulatesneuronal pages 28-31): Yuansong Wan, Momo Morikawa, M. Morikawa, Suguru Iwata, M. Naseer, Adeel Gulzar Ahmed Chaudhary, Yosuke Tanaka, and N. Hirokawa. Kif4 regulates neuronal morphology and seizure susceptibility via the parp1 signaling pathway. The Journal of Cell Biology, Dec 2022. URL: https://doi.org/10.1083/jcb.202208108, doi:10.1083/jcb.202208108. This article has 18 citations.
(correia2023unexpectedkif4afunctions pages 2-5): Patrícia D. Correia, Bárbara M. de Sousa, Jesús Chato-Astrain, Joana P. Faria, Veronica Estrada, João B. Relvas, Hans W. Müller, Víctor Carriel, Frank Bosse, and Sandra I. Vieira. Unexpected kif4a functions in adult regeneration encompass a dual role in neurons and in proliferative repair schwann cells. bioRxiv, May 2023. URL: https://doi.org/10.1101/2023.05.21.541636, doi:10.1101/2023.05.21.541636. This article has 0 citations.
(correia2023unexpectedkif4afunctions pages 10-13): Patrícia D. Correia, Bárbara M. de Sousa, Jesús Chato-Astrain, Joana P. Faria, Veronica Estrada, João B. Relvas, Hans W. Müller, Víctor Carriel, Frank Bosse, and Sandra I. Vieira. Unexpected kif4a functions in adult regeneration encompass a dual role in neurons and in proliferative repair schwann cells. bioRxiv, May 2023. URL: https://doi.org/10.1101/2023.05.21.541636, doi:10.1101/2023.05.21.541636. This article has 0 citations.
(correia2023unexpectedkif4afunctions pages 5-7): Patrícia D. Correia, Bárbara M. de Sousa, Jesús Chato-Astrain, Joana P. Faria, Veronica Estrada, João B. Relvas, Hans W. Müller, Víctor Carriel, Frank Bosse, and Sandra I. Vieira. Unexpected kif4a functions in adult regeneration encompass a dual role in neurons and in proliferative repair schwann cells. bioRxiv, May 2023. URL: https://doi.org/10.1101/2023.05.21.541636, doi:10.1101/2023.05.21.541636. This article has 0 citations.
(correia2023unexpectedkif4afunctions pages 1-2): Patrícia D. Correia, Bárbara M. de Sousa, Jesús Chato-Astrain, Joana P. Faria, Veronica Estrada, João B. Relvas, Hans W. Müller, Víctor Carriel, Frank Bosse, and Sandra I. Vieira. Unexpected kif4a functions in adult regeneration encompass a dual role in neurons and in proliferative repair schwann cells. bioRxiv, May 2023. URL: https://doi.org/10.1101/2023.05.21.541636, doi:10.1101/2023.05.21.541636. This article has 0 citations.
(ruscu2024thepost‐strokeyoung pages 7-8): Mihai Ruscu, Bogdan Capitanescu, Paul Rupek, Thomas Dandekar, Eugen Radu, Dirk M. Hermann, and Aurel Popa‐Wagner. The post‐stroke young adult brain has limited capacity to re‐express the gene expression patterns seen during early postnatal brain development. Brain Pathology, Jan 2024. URL: https://doi.org/10.1111/bpa.13232, doi:10.1111/bpa.13232. This article has 5 citations and is from a domain leading peer-reviewed journal.
(willemsen2014involvementofthe pages 1-2): Marjolein H Willemsen, Wei Ba, Willemijn M Wissink-Lindhout, Arjan P M de Brouwer, Stefan A Haas, Melanie Bienek, Hao Hu, Lisenka E L M Vissers, Hans van Bokhoven, Vera Kalscheuer, Nael Nadif Kasri, and Tjitske Kleefstra. Involvement of the kinesin family members kif4a and kif5c in intellectual disability and synaptic function. Journal of Medical Genetics, 51:487-494, May 2014. URL: https://doi.org/10.1136/jmedgenet-2013-102182, doi:10.1136/jmedgenet-2013-102182. This article has 118 citations and is from a domain leading peer-reviewed journal.
(kalantari2021expandingthekif4a pages 1-2): Silvia Kalantari, Colleen Carlston, Norah Alsaleh, Ghada M. H. Abdel‐Salam, Fowzan Alkuraya, Mitsuhiro Kato, Naomichi Matsumoto, Satoko Miyatake, Tatsuya Yamamoto, Lucas Fares‐Taie, Jean‐Michel Rozet, Nicolas Chassaing, Catherine Vincent‐Delorme, Anjeung Kang‐Bellin, Kirsty McWalter, Caleb Bupp, Emily Palen, Monisa D. Wagner, Marcello Niceta, Claudia Cesario, Roberta Milone, Julie Kaplan, Erin Wadman, William B. Dobyns, and Isabel Filges. Expanding the kif4a ‐associated phenotype. American Journal of Medical Genetics. Part a, 185:3728-3739, Aug 2021. URL: https://doi.org/10.1002/ajmg.a.62443, doi:10.1002/ajmg.a.62443. This article has 20 citations and is from a peer-reviewed journal.
(liu2025kif4aindisease pages 9-10): Yi Liu, Yunhua Li, Chunrong Tang, Honghua Wen, Jingxian Tang, Gangwen Chen, and Yongkang Wu. Kif4a in disease pathogenesis and therapeutics: from molecular mechanisms to clinical translation. Biology Direct, Dec 2025. URL: https://doi.org/10.1186/s13062-025-00712-0, doi:10.1186/s13062-025-00712-0. This article has 3 citations and is from a peer-reviewed journal.
(liu2025researchprogressof pages 14-14): Shuyi Liu, Jialing Chen, Liping Shi, Yuan Deng, and Zhengbo Wang. Research progress of kinesin family in neurological diseases. Frontiers in Cellular Neuroscience, Sep 2025. URL: https://doi.org/10.3389/fncel.2025.1527305, doi:10.3389/fncel.2025.1527305. This article has 7 citations.

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Terms named as a different term	1

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

MONDO:0010488 (4 mentions) - the report calls it "if available"; MONDO calls it intellectual disability, X-linked 100

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

CL:0002609 (obsolete neuron of cerebral cortex) (1 mention) - replaced by CL:0010012

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OpenScientist Report

Inheritance

Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

External Assertions

Medical Actions

Diagnosis

Prevalence

Differential Diagnoses

Animal Models

Source YAML

References & Deep Research

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Citation Requirements

Output Format

KIF4A-related X-linked intellectual disability (MRX100): disease-characteristics report

Executive summary and evidence limits

1. Disease information

Definition and identifiers

Key primary sources

2. Etiology, risk, protection, and gene–environment interaction

Causal factor

Genetic risk

Environmental, infectious, and lifestyle risk

Protective factors and gene–environment interaction

3. Phenotypes

4. Genetic and molecular information

Variant classes and interpretation

5. Environmental information

6. Mechanism and pathophysiology

Ordered causal chain

Molecular and cellular detail

7. Anatomical structures affected

8. Temporal development and natural history

9. Inheritance and population

10. Diagnostics

Clinical evaluation

Genetic-testing strategy

Differential diagnosis

11. Outcome and prognosis

12. Treatment and current implementation

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

R728Q knock-in mouse

Primary neuronal systems

Injury/regeneration models

Overall expert assessment

Artifacts

Reference Validation

Unresolved references

Term Validation

Terms the report names something else

Obsolete terms