| 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 (pqac-00000000) | 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 (pqac-00000001, pqac-00000007) | 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 (pqac-00000001, pqac-00000010) | 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 (pqac-00000001) | 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 (pqac-00000002, pqac-00000003, pqac-00000004) | 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 (pqac-00000002) | 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 (pqac-00000009, pqac-00000011) | 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 (pqac-00000021, pqac-00000025) | 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 (pqac-00000022, pqac-00000024) | 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 (pqac-00000019, pqac-00000020, pqac-00000021) | 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 (pqac-00000019, pqac-00000023) | 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 (pqac-00000013, pqac-00000014, pqac-00000016, pqac-00000017) | 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 (pqac-00000018) | 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 (pqac-00000000) | 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.*