{"gene":"KIF5A","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2002,"finding":"A missense mutation (N256S) in the KIF5A motor domain at an invariant asparagine residue prevents stimulation of the motor ATPase by microtubule-binding, establishing KIF5A as the causal gene for hereditary spastic paraplegia SPG10 and implicating impaired anterograde axoplasmic transport in its pathogenesis.","method":"Human genetics (linkage, sequencing) combined with functional inference from orthologous kinesin mutation studies showing loss of microtubule-stimulated ATPase activity","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic linkage plus sequencing with functional inference from ortholog biochemistry; single study but consistent with prior ortholog data","pmids":["12355402"],"is_preprint":false},{"year":2003,"finding":"Neuron-specific conditional knockout of KIF5A in mice causes accumulation of neurofilament subunits (NF-H, NF-M, NF-L) in peripheral sensory neuron cell bodies with reduction in axon caliber, establishing KIF5A as required for slow axonal transport of neurofilaments while leaving fast axonal transport largely intact.","method":"Conditional knockout mouse (synapsin-Cre × floxed KIF5A), immunostaining, axon caliber morphometry","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with specific cargo accumulation phenotype, replicated across multiple age groups and neuronal populations in a single rigorous study","pmids":["12682084"],"is_preprint":false},{"year":2008,"finding":"SPG10 point mutations in the KIF5A motor/neck domain reduce microtubule affinity and/or gliding velocity; in single-molecule laser-trapping assays none of the mutants (N256S, K253N, R280C, A361V) move processively; in mixed-motor assays N256S reduces gross cargo flux by slowing transport while K253N and R280C reduce microtubule binding of cargo, revealing two distinct dominant-negative mechanisms underlying SPG10.","method":"In vitro microtubule gliding assay, laser-trapping single-molecule assay, quantum-dot cargo transport assay with heterodimeric wild-type/mutant mixtures","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with multiple mutants, single-molecule assays, and mixed-motor experiments revealing mechanistically distinct dominant-negative modes","pmids":["18203753"],"is_preprint":false},{"year":2010,"finding":"The SPG10 mutation N256S in kinesin-1A (KIF5A) decreases both anterograde and retrograde neurofilament transport flux in cultured cortical neurons by reducing the frequency of anterograde and retrograde movements; anterograde velocity is unchanged while retrograde velocity is increased, demonstrating interdependence of anterograde and retrograde neurofilament motors.","method":"Live-cell fluorescence imaging of neurofilament transport in mouse cortical neurons expressing N256S-KIF5A","journal":"Molecular neurodegeneration","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging of tagged cargo in primary neurons expressing mutant motor; single lab, single method","pmids":["21087519"],"is_preprint":false},{"year":2012,"finding":"KIF5A knockout mouse motor neurons show reduced anterograde and retrograde mitochondrial transport velocity, reduced axon/dendrite outgrowth and branching, and reduced survival; sensory neurons show reduced neurite outgrowth but no survival deficit, indicating a cell-type-specific requirement for KIF5A in mitochondrial axonal transport.","method":"Primary neuron cultures from constitutive KIF5A−/− mice, live mitochondrial transport imaging, survival assays, morphometric analysis","journal":"Neurogenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function in primary neurons with live imaging of specific cargo; single lab study","pmids":["22466687"],"is_preprint":false},{"year":2012,"finding":"KIF5A specifically interacts with GABARAP (GABA-type-A-receptor-associated protein) and is required for neuronal surface expression of GABA-A receptors; conditional Kif5a-knockout mice show impaired GABA-A receptor-mediated synaptic transmission and epileptic EEG abnormalities, demonstrating that KIF5A mediates anterograde transport of GABA-A receptors via GABARAP.","method":"Conditional Kif5a-KO mice (neuron-specific), EEG, co-immunoprecipitation of KIF5A with GABARAP, surface biotinylation of GABA-A receptors","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP identifying binding partner, KO mouse with specific electrophysiological and receptor trafficking phenotype, multiple orthogonal methods","pmids":["23217743"],"is_preprint":false},{"year":2012,"finding":"In a Drosophila SPG10 model, expression of the N256S Khc (KIF5A ortholog) mutation disrupts axonal transport and induces motoneuron disease; genetic analysis indicates SPG10 is caused by selective dominant-negative loss of endogenous kinesin-1 function rather than haploinsufficiency, and neurofilament-independent cargo deficits are sufficient to cause HSP-like pathology.","method":"Drosophila transgenic expression of N256S Khc, genetic epistasis, axonal transport assays, synaptic morphology and behavioral phenotyping","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in model organism, multiple phenotypic readouts; single lab Drosophila study","pmids":["23209432"],"is_preprint":false},{"year":2014,"finding":"Kif5Aa-specific function in mitochondrial localization in peripheral sensory axons is mediated by the KIF5A C-terminal tail domain; only Kif5Aa or chimeric motors bearing the Kif5Aa C-tail rescue the mitochondria-lacking, degenerating axon phenotype of zebrafish kif5Aa mutants, establishing cargo-specificity through the tail domain.","method":"Zebrafish kif5Aa mutant analysis, chimeric rescue constructs, cell-autonomous epistasis with kif1b and kbp, live imaging of axonal mitochondria","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain-swap rescue experiments in vivo combined with genetic epistasis and live imaging; multiple orthogonal methods in a single rigorous study","pmids":["25355224"],"is_preprint":false},{"year":2017,"finding":"KIF5A co-localizes with collagen-1-containing vesicles in human pleural mesothelial cells, and KIF5A knockdown significantly reduces collagen-1 secretion and peripheral vesicle localization; live imaging shows KIF5A and collagen-1 vesicles move together at ~0.56 µm/sec, establishing KIF5A as the motor for procollagen vesicle transport in myofibroblast-like cells.","method":"Super-resolution structured illumination microscopy, DUO-Link proximity ligation, siRNA knockdown, live-cell co-imaging of GFP-KIF5A and mCherry-Col-1, kymography","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal imaging methods with functional knockdown; single lab study in non-neuronal cell type","pmids":["28676645"],"is_preprint":false},{"year":2018,"finding":"ALS-associated KIF5A splice-site mutations in the C-terminal domain cause exon 27 skipping and haploinsufficiency of KIF5A mRNA in patient lymphoblasts, while a missense mutation (p.Arg1007Gly) upstream of the exon 27 splice donor abrogates the splice donor site and causes defective pre-mRNA splicing, establishing loss-of-function via the C-terminal domain as a mechanism in familial ALS.","method":"Whole exome sequencing, rare variant burden analysis, lymphoblast RNA/mRNA sequencing, splice-site functional analysis","journal":"Brain","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mRNA sequencing in patient cells demonstrating splice defect; multiple family/patient cohorts but single institution","pmids":["29342275"],"is_preprint":false},{"year":2021,"finding":"KIF5A selectively binds the RNA-binding protein SFPQ within a tetrameric complex also containing the adaptor KLC1, and this KIF5A/KLC1-mediated transport of SFPQ-RNA granules is required for axon survival; CMT-associated KIF5A mutations impair SFPQ-motor complex binding.","method":"Co-immunoprecipitation of SFPQ with KIF5A/KLC1 complex, KIF5A loss-of-function, axon degeneration assay, rescue with locally translated proteins in CMT models","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP identifying specific tetrameric complex, loss-of-function axon survival assay, disease mutation validation, and therapeutic rescue; multiple orthogonal methods","pmids":["33284322"],"is_preprint":false},{"year":2022,"finding":"ALS-associated KIF5A ΔExon27 (exon 27 skipping) mutant is constitutively active (relieved of autoinhibition) at the single-molecule level, shows dysregulated motor activity, cellular mislocalization, altered axonal transport, altered protein and RNA interactions, and decreased neuronal survival, supporting a toxic gain-of-function mechanism.","method":"Single-molecule motility assay, neuronal survival assay, co-immunoprecipitation, RNA interaction profiling, gene expression/splicing analysis, cellular mislocalization imaging","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — single-molecule reconstitution demonstrating constitutively active state, combined with multiple cellular assays; replicated by independent lab (PMID 35735139)","pmids":["35385738"],"is_preprint":false},{"year":2022,"finding":"KIF5A ΔExon27 is prone to form oligomers and aggregates; purified ΔExon27 oligomers show more active movement on microtubules in vitro than wild-type KIF5A, and expression in C. elegans neurons causes morphological defects, indicating gain-of-function toxicity rather than simple loss-of-function.","method":"In vitro oligomerization assay, microtubule motility assay with purified protein, C. elegans neuron morphology assay","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein confirming hyperactivity; single lab, corroborates PMID 35385738","pmids":["35430760"],"is_preprint":false},{"year":2022,"finding":"ALS-linked KIF5A ΔExon27 mutant relieves motor autoinhibition, increases motor self-association, and produces drastically enhanced processivity on microtubules; ΔExon27 is prone to form cytoplasmic aggregates and is neurotoxic in Drosophila (wing defects, motor impairment, paralysis, premature death), establishing toxic gain-of-function as the pathogenic mechanism.","method":"Single-molecule processivity assay, electron microscopy of aggregates, Drosophila transgenic overexpression with locomotion and survival readouts, patient iPSC motor neuron analysis","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro single-molecule reconstitution plus in vivo Drosophila model; multiple orthogonal methods corroborating toxic gain-of-function; independently replicated","pmids":["35735139"],"is_preprint":false},{"year":2022,"finding":"Seizure-induced changes reduce KIF5A interactions with Gabrb2/3 (GABA-A receptor subunits) while increasing KIF5A interactions with GluR2 (AMPA receptor subunit), with decreased recycling of GABA-A receptors and increased recycling of AMPA receptors to the surface, demonstrating that KIF5A differentially regulates excitatory/inhibitory receptor surface expression.","method":"Co-immunoprecipitation of KIF5A with GluR2 and Gabrb2+3 in seizure models (in vivo PTZ-rat and in vitro Mg2+-free model), receptor recycling assay, surface expression assay","journal":"Annals of translational medicine","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP in disease model, multiple receptor assays; single lab, moderate follow-up","pmids":["36388788"],"is_preprint":false},{"year":2022,"finding":"Kif5a knockout in retinal ganglion cells (RGCs) results in progressive RGC degeneration in the absence of injury; Kif5a knockdown reduces anterograde mitochondrial trafficking in RGCs while Kif5a overexpression enhances it, identifying Kif5a-dependent mitochondrial transport failure as a cause of RGC neurodegeneration.","method":"In vivo Kif5a KO in RGCs (AAV-Cre), quantitative transportome analysis, live mitochondrial transport imaging, progressive degeneration scoring","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO with specific cargo transport assay and degeneration phenotype; single lab","pmids":["35259089"],"is_preprint":false},{"year":2023,"finding":"In Drosophila motor neurons, KIF5A ΔExon27 expression causes locomotion deficits, disturbed distribution of mitochondria and synaptic vesicles, accumulation of KIF5A Δ27-containing inclusions in soma and axons, alterations in neuromuscular junction morphology and synaptic transmission, and motor neuron death, consistent with toxic gain-of-function.","method":"Drosophila transgenic expression of KIF5A Δ27 in motor neurons, electrophysiology at NMJ, live mitochondrial/synaptic vesicle imaging, larval locomotion assay, survival assay","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo model organism with multiple readouts; single lab, corroborates PMID 35735139","pmids":["37748861"],"is_preprint":false},{"year":2023,"finding":"TLR7 activation in neurons induces autophagy and decreases KIF5A expression, which reduces KIF5A interactions with GABARAP and GABAARβ2/3, resulting in impaired GABA-A receptor transport and abnormal inhibitory postsynaptic transmission, increasing seizure susceptibility.","method":"TLR7 KO mice, co-immunoprecipitation of KIF5A with GABARAP and GABAARβ2/3, seizure susceptibility assay, autophagy induction assay","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with specific downstream receptor transport phenotype and co-IP; single lab","pmids":["37258573"],"is_preprint":false},{"year":2023,"finding":"KIF5A deficiency in human iPSC-derived motor neurons reduces neurite complexity at DIV14, impairs axonal regeneration, decreases mitochondria motility and anterograde speed at DIV42, and strongly reduces anterograde transport of SFPQ-associated RNA granules at DIV42, with no effect on neurofilament transport.","method":"KIF5A null iPSC-derived human motor neurons, live axonal transport imaging of mitochondria, SFPQ granules, and neurofilaments, axonal regeneration assay","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — isogenic human KO model with cargo-specific transport assays using live imaging; multiple orthogonal cargo analyses; independently replicated in preprint","pmids":["39644980"],"is_preprint":false},{"year":2023,"finding":"Kif5a knockdown in developing retinal ganglion cells decreases anterograde mitochondrial transport while Kif5a overexpression increases mitochondrial motility and anterograde transport, directly establishing Kif5a as a regulator of mitochondrial axonal transport in developing RGCs.","method":"shRNA knockdown and AAV overexpression in primary rat RGCs, MitoTracker live-cell imaging with kymography","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional manipulation (KD and OE) with quantitative live imaging of specific cargo; single lab","pmids":["36862119"],"is_preprint":false},{"year":2024,"finding":"Full-length autoinhibited KIF5A homodimer adopts a compact bent conformation through a bend between coiled-coils 2 and 3 around P687; crosslinking mass spectrometry reveals interactions between motor domain, coiled-coil 1, and the proximal C-terminal IAK-containing region, but not the distal C-terminal tail; the ALS exon-27-skip mutant retains autoinhibited molecules but its autoinhibited state is more labile.","method":"Negative-stain electron microscopy, crosslinking mass spectrometry (XL-MS), AlphaFold2 structure prediction of full-length KIF5A homodimer","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — structural study with XL-MS and EM; single lab, no mutagenesis validation of specific contacts","pmids":["38309508"],"is_preprint":false},{"year":2025,"finding":"ALS-related KIF5A ΔExon27 mutant protein accumulates in human iPSC-derived motor neurons, induces cytoplasmic mislocalization of TDP-43 (an ALS hallmark), and this is exacerbated by overexpression; the altered C-terminal sequence has a basic isoelectric point (unlike acidic WT), and engineering a mutant retaining the aberrant sequence but with lower pI reduces protein aggregation and TDP-43 mislocalization, demonstrating that the isoelectric shift drives KIF5A aggregation and TDP-43 pathology.","method":"iPSC-derived motor neuron overexpression, pI-modified KIF5A variants, immunofluorescence for TDP-43 localization and KIF5A aggregation, primary neuron overexpression","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — engineered pI rescue experiment with defined molecular readout; single lab, novel mechanistic claim","pmids":["40555518"],"is_preprint":false},{"year":2025,"finding":"FAK signaling promotes KIF5A expression and neuronal differentiation by downregulating epigenetic modifiers DNMT1 and KDM5A; FAK activity is phosphorylation-dependent and required for KIF5A upregulation, which in turn regulates mitochondrial dynamics during differentiation.","method":"FAK inhibition/activation, DNMT1/KDM5A knockdown, KIF5A overexpression/knockdown, mitochondrial morphology assay in differentiating neurons","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, signaling pathway study with limited mechanistic resolution on KIF5A's direct role","pmids":["41084333"],"is_preprint":false},{"year":2025,"finding":"SMN protein associates with KIF5A mRNA and contributes to its stability; SMN deficiency in human neurons and SMA mouse models downregulates KIF5A, and KIF5A overexpression rescues impaired axon regeneration caused by SMN loss, placing KIF5A downstream of SMN in a pathway linking SMA and ALS pathophysiology.","method":"RNA immunoprecipitation of SMN with KIF5A mRNA, SMN knockdown in human neurons and SMA mouse model, KIF5A overexpression rescue of axon regeneration","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-IP establishing direct SMN-KIF5A mRNA interaction plus epistatic rescue experiment; single lab","pmids":["41885937"],"is_preprint":false},{"year":2025,"finding":"KIF5A mutations causing ALS (exon 27 skipping) abolish KIF5A axonal interaction with SFPQ cargo and, under stress conditions, iPSC-derived motor neurons carrying an intronic KIF5A variant (c.2993-6C>A) exhibit TDP-43 proteinopathy, linking KIF5A ΔExon27-mediated cargo transport failure to TDP-43 pathology.","method":"iPSC-derived motor neurons from patients and controls, RT-PCR for exon 27 splicing, immunofluorescence for KIF5A-SFPQ axonal colocalization and TDP-43 localization under stress","journal":"Neurology. Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient iPSC model with specific cargo and pathology readouts; single lab","pmids":["41836882"],"is_preprint":false},{"year":2025,"finding":"KIF5A directly binds mRNAs encoding synaptic ribosomal proteins and is required for their synaptic localization and normal synaptic composition and function; KIF5A also binds G3BP1 and stress granule-associated proteins; ALS-linked KIF5A mutations enhance mRNA binding, increase synaptic ribosomal protein accumulation, induce neuronal hyperexcitability, and impair stress responses—a gain-of-function RNA-binding mechanism.","method":"CLIP/RNA immunoprecipitation, KIF5A loss-of-function, ALS mutant overexpression in patient iPSC motor neurons, electrophysiology, stress granule co-IP","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct RNA binding demonstrated by CLIP, functional KO plus mutant gain-of-function with electrophysiology; preprint, not yet peer-reviewed","pmids":["41279899"],"is_preprint":true},{"year":2025,"finding":"KIF5A from giraffes and pythons moves 25% faster than mouse KIF5A on neuronal microtubules due to three amino acid substitutions (R114Q, S155A, Y309F); structural analysis reveals accelerated ADP release underlies enhanced velocity; the motor generates less force but maintains cargo transport under load and exerts less drag in multi-motor environments—demonstrating that the KIF5A mechanochemical cycle is tunable and that ADP release rate is rate-limiting for velocity.","method":"In vitro single-molecule motility assay, live imaging in cultured mouse hippocampal neurons, cryo-EM/structural analysis, site-directed mutagenesis of velocity-determining residues","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and structural analysis; preprint, not peer-reviewed","pmids":["40654747"],"is_preprint":true},{"year":2025,"finding":"SPG10 mutations in KIF5A cause loss of colocalization with α-tubulin; a splice-site mutation (c.446-2A>G) destroys the donor site leading to exon 6 skipping producing truncated proteins with reduced expression that lose microtubule colocalization, while four missense mutations retain normal mRNA/protein levels but also lose α-tubulin colocalization, indicating that both haploinsufficiency and abnormal subcellular localization underlie SPG10.","method":"In vitro minigene splicing assay, protein expression analysis, immunofluorescence co-localization with α-tubulin in transfected cells, iPSC motor neuron functional validation","journal":"Parkinsonism & related disorders","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional splicing assay plus subcellular localization in multiple mutants; single lab","pmids":["40945307"],"is_preprint":false},{"year":2026,"finding":"The SPG10 variant p.R17Q in the KIF5A motor domain (predicted to affect ATP binding) causes increased KIF5A distribution in distal neurites with neurofilament-positive axonal swellings, and significantly reduces anterograde velocity and distance of mitochondria and lysosomes along neurites in isogenic iPSC-derived motor neurons, confirming pathogenicity and establishing defective axonal transport as the mechanism.","method":"CRISPR-Cas9 isogenic iPSC correction, live axonal transport imaging of mitochondria and lysosomes by kymography, immunofluorescence for KIF5A distribution and neurofilament swellings","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isogenic CRISPR-corrected human iPSC model with quantitative cargo-specific transport assays; single lab","pmids":["41836058"],"is_preprint":false}],"current_model":"KIF5A is a neuron-enriched kinesin-1 heavy chain that powers anterograde axonal transport of diverse cargoes—including neurofilaments, mitochondria, GABA-A receptors (via GABARAP adaptor), SFPQ-RNA granules (via KLC1 adaptor), synaptic ribosomal protein mRNAs, lysosomes, and collagen vesicles—adopting an autoinhibited compact bent conformation in its inactive state; disease mutations in the motor/stalk domain (SPG10/CMT2) impair microtubule-stimulated ATPase activity and cargo flux through dominant-negative or haploinsufficiency mechanisms, while ALS-linked C-terminal exon-27-skipping mutations produce a constitutively active, hyperprocessive motor with a novel basic-pI C-terminus that aggregates, acquires gain-of-function RNA-binding properties, mislocalizes TDP-43, and disrupts axonal transport homeostasis in motor neurons."},"narrative":{"mechanistic_narrative":"KIF5A is a neuron-enriched kinesin-1 heavy chain that powers anterograde axonal transport of multiple cargoes and is required for axon and neuron survival [PMID:12682084, PMID:39644980]. Loss-of-function studies establish a broad cargo repertoire: neurofilament subunits transported by slow axonal transport [PMID:12682084], mitochondria whose motility KIF5A bidirectionally controls in motor neurons and retinal ganglion cells [PMID:22466687, PMID:35259089, PMID:36862119], GABA-A receptors delivered to the neuronal surface via the GABARAP adaptor [PMID:23217743], and SFPQ-RNA granules carried within a tetrameric complex with the KLC1 adaptor [PMID:33284322]. Cargo specificity is encoded in the C-terminal tail domain, as domain-swap rescue experiments demonstrate [PMID:25355224], and KIF5A also transports collagen-1 vesicles in non-neuronal mesothelial cells [PMID:28676645]. The motor adopts an autoinhibited compact bent conformation involving contacts between the motor domain, coiled-coil 1, and the proximal IAK-containing C-terminus [PMID:38309508]. Two genetically distinct disease mechanisms emerge. SPG10/CMT2 mutations in the motor and neck domain abolish processive movement and microtubule-stimulated activity, acting through dominant-negative reduction of cargo flux and loss of microtubule colocalization [PMID:12355402, PMID:18203753, PMID:40945307], and impair SFPQ-motor complex binding [PMID:33284322]. In contrast, ALS-linked exon-27-skipping mutations relieve autoinhibition to produce a constitutively active, hyperprocessive, self-associating motor that aggregates and is neurotoxic in vivo [PMID:35385738, PMID:35735139]; the aberrant basic-pI C-terminus drives this aggregation and the cytoplasmic mislocalization of TDP-43 [PMID:40555518], while enhanced gain-of-function RNA binding mislocalizes synaptic ribosomal protein mRNAs and induces hyperexcitability [PMID:41279899]. KIF5A expression is itself regulated downstream of SMN, which stabilizes KIF5A mRNA and links it to spinal muscular atrophy pathophysiology [PMID:41885937].","teleology":[{"year":2002,"claim":"Established KIF5A as a disease gene and tied its motor function to axonal transport by showing a motor-domain mutation that blocks microtubule-stimulated ATPase activity causes SPG10.","evidence":"Human linkage/sequencing with functional inference from orthologous kinesin biochemistry","pmids":["12355402"],"confidence":"Medium","gaps":["ATPase defect inferred from ortholog rather than measured on human KIF5A","no direct cargo or transport assay in this study"]},{"year":2003,"claim":"Defined the first physiological cargo by showing KIF5A is required for slow axonal transport of neurofilaments in vivo, distinguishing it from fast transport.","evidence":"Neuron-specific conditional KIF5A knockout mouse with neurofilament accumulation and axon caliber morphometry","pmids":["12682084"],"confidence":"High","gaps":["mechanism of neurofilament cargo coupling not defined","did not address other cargoes"]},{"year":2008,"claim":"Resolved how SPG10 mutations act mechanistically, revealing two distinct dominant-negative modes (slowed transport vs. reduced cargo microtubule binding) at single-molecule resolution.","evidence":"In vitro gliding, laser-trap single-molecule, and quantum-dot mixed wild-type/mutant cargo transport assays","pmids":["18203753"],"confidence":"High","gaps":["in vitro reconstitution may not capture neuronal regulatory context","did not test endogenous cargo specificity"]},{"year":2010,"claim":"Showed SPG10 N256S reduces neurofilament transport flux in both directions, demonstrating interdependence of anterograde and retrograde motors.","evidence":"Live-cell neurofilament transport imaging in mutant-expressing cortical neurons","pmids":["21087519"],"confidence":"Medium","gaps":["single method, single lab","molecular basis of bidirectional coupling unresolved"]},{"year":2012,"claim":"Expanded the cargo repertoire and disease relevance by establishing KIF5A in mitochondrial transport and in GABA-A receptor surface delivery via GABARAP, with epileptic phenotypes.","evidence":"Constitutive and conditional KIF5A knockout mice, co-IP with GABARAP, surface biotinylation, EEG, and live mitochondrial imaging; Drosophila SPG10 genetic epistasis","pmids":["22466687","23217743","23209432"],"confidence":"High","gaps":["structural basis of GABARAP binding not defined","whether SPG10 is purely dominant-negative vs. haploinsufficient debated across models"]},{"year":2014,"claim":"Localized cargo specificity to the C-terminal tail by showing only motors carrying the Kif5Aa C-tail rescue the mitochondrial transport and axon degeneration phenotype.","evidence":"Zebrafish kif5Aa mutant chimeric rescue and genetic epistasis with live mitochondrial imaging","pmids":["25355224"],"confidence":"High","gaps":["specific tail-domain adaptors for mitochondria not identified","model-organism ortholog"]},{"year":2017,"claim":"Extended KIF5A function beyond neurons by identifying it as the motor for procollagen-1 vesicle transport and secretion in mesothelial cells.","evidence":"Super-resolution and proximity-ligation imaging, siRNA knockdown, live co-imaging of GFP-KIF5A and collagen-1","pmids":["28676645"],"confidence":"Medium","gaps":["cargo adaptor for collagen vesicles unknown","single non-neuronal cell type"]},{"year":2018,"claim":"Identified C-terminal splice-site/exon-27 mutations as a familial ALS mechanism, initially framed as loss-of-function via haploinsufficiency.","evidence":"Whole exome sequencing, rare-variant burden analysis, and patient lymphoblast mRNA/splice analysis","pmids":["29342275"],"confidence":"Medium","gaps":["loss-of-function interpretation later complicated by gain-of-function findings","patient cells not motor neurons"]},{"year":2021,"claim":"Defined the SFPQ-RNA granule transport pathway by identifying a KIF5A/KLC1/SFPQ tetrameric complex required for axon survival, and showed CMT mutations disrupt it.","evidence":"Co-IP of the tetrameric complex, loss-of-function axon degeneration assay, disease-mutation validation, and local-translation rescue","pmids":["33284322"],"confidence":"High","gaps":["RNA content of granules not fully cataloged","stoichiometry within the complex not resolved"]},{"year":2022,"claim":"Reframed the ALS mechanism as toxic gain-of-function by showing exon-27-skip mutants relieve autoinhibition to become constitutively active, hyperprocessive, self-associating, aggregation-prone, and neurotoxic across systems.","evidence":"Single-molecule motility and processivity assays with purified protein, EM of aggregates, co-IP and RNA profiling, and Drosophila and C. elegans models","pmids":["35385738","35430760","35735139"],"confidence":"High","gaps":["how hyperactivity translates to cell death not fully defined","relative contribution of transport dysregulation vs. aggregation unresolved"]},{"year":2022,"claim":"Linked KIF5A to excitatory/inhibitory balance and to neurodegeneration via mitochondrial transport, showing it differentially routes GABA-A vs. AMPA receptors in seizure and is required for retinal ganglion cell survival.","evidence":"Co-IP in seizure models with receptor recycling/surface assays; in vivo RGC knockout/knockdown/overexpression with mitochondrial transport imaging","pmids":["36388788","35259089"],"confidence":"Medium","gaps":["mechanism of receptor-selectivity switching unknown","single-lab disease-model contexts"]},{"year":2023,"claim":"Established cargo-selective transport deficits in human cells and uncovered upstream regulation of KIF5A by TLR7/autophagy signaling affecting inhibitory transmission.","evidence":"KIF5A-null iPSC motor neurons with cargo-specific live imaging (mitochondria, SFPQ granules, neurofilaments); TLR7 KO mice with co-IP and seizure assays; Drosophila ΔExon27 motor-neuron model; RGC bidirectional manipulation","pmids":["39644980","37258573","37748861","36862119"],"confidence":"High","gaps":["why neurofilament transport is spared in human iPSC neurons unexplained","direct regulators of KIF5A expression beyond TLR7 incomplete"]},{"year":2024,"claim":"Provided a structural basis for autoinhibition, defining the compact bent conformation and showing the ALS exon-27-skip mutant retains but destabilizes this state.","evidence":"Negative-stain EM, crosslinking mass spectrometry, and AlphaFold2 modeling of the full-length homodimer","pmids":["38309508"],"confidence":"Medium","gaps":["specific autoinhibitory contacts not validated by mutagenesis","no high-resolution structure"]},{"year":2025,"claim":"Elucidated the molecular driver of ALS aggregation and RNA-based gain-of-function, showing the basic-pI C-terminus causes aggregation and TDP-43 mislocalization and that enhanced mRNA binding mislocalizes synaptic ribosomal transcripts.","evidence":"pI-engineered KIF5A variants in iPSC motor neurons, TDP-43 immunofluorescence, CLIP/RNA-IP, electrophysiology, and stress-granule co-IP (one preprint)","pmids":["40555518","41279899","41836882"],"confidence":"Medium","gaps":["RNA-binding mechanism of an otherwise non-RNA-binding motor not structurally defined","link between aggregation and transport failure quantitatively unresolved"]},{"year":2025,"claim":"Placed KIF5A within an SMN-dependent pathway and refined the SPG10 mechanism with tunable mechanochemistry and isogenic disease models.","evidence":"SMN RNA-IP and SMA rescue experiments; 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single study but consistent with prior ortholog data\",\n      \"pmids\": [\"12355402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Neuron-specific conditional knockout of KIF5A in mice causes accumulation of neurofilament subunits (NF-H, NF-M, NF-L) in peripheral sensory neuron cell bodies with reduction in axon caliber, establishing KIF5A as required for slow axonal transport of neurofilaments while leaving fast axonal transport largely intact.\",\n      \"method\": \"Conditional knockout mouse (synapsin-Cre × floxed KIF5A), immunostaining, axon caliber morphometry\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with specific cargo accumulation phenotype, replicated across multiple age groups and neuronal populations in a single rigorous study\",\n      \"pmids\": [\"12682084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SPG10 point mutations in the KIF5A motor/neck domain reduce microtubule affinity and/or gliding velocity; in single-molecule laser-trapping assays none of the mutants (N256S, K253N, R280C, A361V) move processively; in mixed-motor assays N256S reduces gross cargo flux by slowing transport while K253N and R280C reduce microtubule binding of cargo, revealing two distinct dominant-negative mechanisms underlying SPG10.\",\n      \"method\": \"In vitro microtubule gliding assay, laser-trapping single-molecule assay, quantum-dot cargo transport assay with heterodimeric wild-type/mutant mixtures\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with multiple mutants, single-molecule assays, and mixed-motor experiments revealing mechanistically distinct dominant-negative modes\",\n      \"pmids\": [\"18203753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The SPG10 mutation N256S in kinesin-1A (KIF5A) decreases both anterograde and retrograde neurofilament transport flux in cultured cortical neurons by reducing the frequency of anterograde and retrograde movements; anterograde velocity is unchanged while retrograde velocity is increased, demonstrating interdependence of anterograde and retrograde neurofilament motors.\",\n      \"method\": \"Live-cell fluorescence imaging of neurofilament transport in mouse cortical neurons expressing N256S-KIF5A\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging of tagged cargo in primary neurons expressing mutant motor; single lab, single method\",\n      \"pmids\": [\"21087519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KIF5A knockout mouse motor neurons show reduced anterograde and retrograde mitochondrial transport velocity, reduced axon/dendrite outgrowth and branching, and reduced survival; sensory neurons show reduced neurite outgrowth but no survival deficit, indicating a cell-type-specific requirement for KIF5A in mitochondrial axonal transport.\",\n      \"method\": \"Primary neuron cultures from constitutive KIF5A−/− mice, live mitochondrial transport imaging, survival assays, morphometric analysis\",\n      \"journal\": \"Neurogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function in primary neurons with live imaging of specific cargo; single lab study\",\n      \"pmids\": [\"22466687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KIF5A specifically interacts with GABARAP (GABA-type-A-receptor-associated protein) and is required for neuronal surface expression of GABA-A receptors; conditional Kif5a-knockout mice show impaired GABA-A receptor-mediated synaptic transmission and epileptic EEG abnormalities, demonstrating that KIF5A mediates anterograde transport of GABA-A receptors via GABARAP.\",\n      \"method\": \"Conditional Kif5a-KO mice (neuron-specific), EEG, co-immunoprecipitation of KIF5A with GABARAP, surface biotinylation of GABA-A receptors\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP identifying binding partner, KO mouse with specific electrophysiological and receptor trafficking phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"23217743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In a Drosophila SPG10 model, expression of the N256S Khc (KIF5A ortholog) mutation disrupts axonal transport and induces motoneuron disease; genetic analysis indicates SPG10 is caused by selective dominant-negative loss of endogenous kinesin-1 function rather than haploinsufficiency, and neurofilament-independent cargo deficits are sufficient to cause HSP-like pathology.\",\n      \"method\": \"Drosophila transgenic expression of N256S Khc, genetic epistasis, axonal transport assays, synaptic morphology and behavioral phenotyping\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in model organism, multiple phenotypic readouts; single lab Drosophila study\",\n      \"pmids\": [\"23209432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Kif5Aa-specific function in mitochondrial localization in peripheral sensory axons is mediated by the KIF5A C-terminal tail domain; only Kif5Aa or chimeric motors bearing the Kif5Aa C-tail rescue the mitochondria-lacking, degenerating axon phenotype of zebrafish kif5Aa mutants, establishing cargo-specificity through the tail domain.\",\n      \"method\": \"Zebrafish kif5Aa mutant analysis, chimeric rescue constructs, cell-autonomous epistasis with kif1b and kbp, live imaging of axonal mitochondria\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain-swap rescue experiments in vivo combined with genetic epistasis and live imaging; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"25355224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KIF5A co-localizes with collagen-1-containing vesicles in human pleural mesothelial cells, and KIF5A knockdown significantly reduces collagen-1 secretion and peripheral vesicle localization; live imaging shows KIF5A and collagen-1 vesicles move together at ~0.56 µm/sec, establishing KIF5A as the motor for procollagen vesicle transport in myofibroblast-like cells.\",\n      \"method\": \"Super-resolution structured illumination microscopy, DUO-Link proximity ligation, siRNA knockdown, live-cell co-imaging of GFP-KIF5A and mCherry-Col-1, kymography\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal imaging methods with functional knockdown; single lab study in non-neuronal cell type\",\n      \"pmids\": [\"28676645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ALS-associated KIF5A splice-site mutations in the C-terminal domain cause exon 27 skipping and haploinsufficiency of KIF5A mRNA in patient lymphoblasts, while a missense mutation (p.Arg1007Gly) upstream of the exon 27 splice donor abrogates the splice donor site and causes defective pre-mRNA splicing, establishing loss-of-function via the C-terminal domain as a mechanism in familial ALS.\",\n      \"method\": \"Whole exome sequencing, rare variant burden analysis, lymphoblast RNA/mRNA sequencing, splice-site functional analysis\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mRNA sequencing in patient cells demonstrating splice defect; multiple family/patient cohorts but single institution\",\n      \"pmids\": [\"29342275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"KIF5A selectively binds the RNA-binding protein SFPQ within a tetrameric complex also containing the adaptor KLC1, and this KIF5A/KLC1-mediated transport of SFPQ-RNA granules is required for axon survival; CMT-associated KIF5A mutations impair SFPQ-motor complex binding.\",\n      \"method\": \"Co-immunoprecipitation of SFPQ with KIF5A/KLC1 complex, KIF5A loss-of-function, axon degeneration assay, rescue with locally translated proteins in CMT models\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP identifying specific tetrameric complex, loss-of-function axon survival assay, disease mutation validation, and therapeutic rescue; multiple orthogonal methods\",\n      \"pmids\": [\"33284322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ALS-associated KIF5A ΔExon27 (exon 27 skipping) mutant is constitutively active (relieved of autoinhibition) at the single-molecule level, shows dysregulated motor activity, cellular mislocalization, altered axonal transport, altered protein and RNA interactions, and decreased neuronal survival, supporting a toxic gain-of-function mechanism.\",\n      \"method\": \"Single-molecule motility assay, neuronal survival assay, co-immunoprecipitation, RNA interaction profiling, gene expression/splicing analysis, cellular mislocalization imaging\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — single-molecule reconstitution demonstrating constitutively active state, combined with multiple cellular assays; replicated by independent lab (PMID 35735139)\",\n      \"pmids\": [\"35385738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KIF5A ΔExon27 is prone to form oligomers and aggregates; purified ΔExon27 oligomers show more active movement on microtubules in vitro than wild-type KIF5A, and expression in C. elegans neurons causes morphological defects, indicating gain-of-function toxicity rather than simple loss-of-function.\",\n      \"method\": \"In vitro oligomerization assay, microtubule motility assay with purified protein, C. elegans neuron morphology assay\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein confirming hyperactivity; single lab, corroborates PMID 35385738\",\n      \"pmids\": [\"35430760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ALS-linked KIF5A ΔExon27 mutant relieves motor autoinhibition, increases motor self-association, and produces drastically enhanced processivity on microtubules; ΔExon27 is prone to form cytoplasmic aggregates and is neurotoxic in Drosophila (wing defects, motor impairment, paralysis, premature death), establishing toxic gain-of-function as the pathogenic mechanism.\",\n      \"method\": \"Single-molecule processivity assay, electron microscopy of aggregates, Drosophila transgenic overexpression with locomotion and survival readouts, patient iPSC motor neuron analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro single-molecule reconstitution plus in vivo Drosophila model; multiple orthogonal methods corroborating toxic gain-of-function; independently replicated\",\n      \"pmids\": [\"35735139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Seizure-induced changes reduce KIF5A interactions with Gabrb2/3 (GABA-A receptor subunits) while increasing KIF5A interactions with GluR2 (AMPA receptor subunit), with decreased recycling of GABA-A receptors and increased recycling of AMPA receptors to the surface, demonstrating that KIF5A differentially regulates excitatory/inhibitory receptor surface expression.\",\n      \"method\": \"Co-immunoprecipitation of KIF5A with GluR2 and Gabrb2+3 in seizure models (in vivo PTZ-rat and in vitro Mg2+-free model), receptor recycling assay, surface expression assay\",\n      \"journal\": \"Annals of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP in disease model, multiple receptor assays; single lab, moderate follow-up\",\n      \"pmids\": [\"36388788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Kif5a knockout in retinal ganglion cells (RGCs) results in progressive RGC degeneration in the absence of injury; Kif5a knockdown reduces anterograde mitochondrial trafficking in RGCs while Kif5a overexpression enhances it, identifying Kif5a-dependent mitochondrial transport failure as a cause of RGC neurodegeneration.\",\n      \"method\": \"In vivo Kif5a KO in RGCs (AAV-Cre), quantitative transportome analysis, live mitochondrial transport imaging, progressive degeneration scoring\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with specific cargo transport assay and degeneration phenotype; single lab\",\n      \"pmids\": [\"35259089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In Drosophila motor neurons, KIF5A ΔExon27 expression causes locomotion deficits, disturbed distribution of mitochondria and synaptic vesicles, accumulation of KIF5A Δ27-containing inclusions in soma and axons, alterations in neuromuscular junction morphology and synaptic transmission, and motor neuron death, consistent with toxic gain-of-function.\",\n      \"method\": \"Drosophila transgenic expression of KIF5A Δ27 in motor neurons, electrophysiology at NMJ, live mitochondrial/synaptic vesicle imaging, larval locomotion assay, survival assay\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo model organism with multiple readouts; single lab, corroborates PMID 35735139\",\n      \"pmids\": [\"37748861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TLR7 activation in neurons induces autophagy and decreases KIF5A expression, which reduces KIF5A interactions with GABARAP and GABAARβ2/3, resulting in impaired GABA-A receptor transport and abnormal inhibitory postsynaptic transmission, increasing seizure susceptibility.\",\n      \"method\": \"TLR7 KO mice, co-immunoprecipitation of KIF5A with GABARAP and GABAARβ2/3, seizure susceptibility assay, autophagy induction assay\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with specific downstream receptor transport phenotype and co-IP; single lab\",\n      \"pmids\": [\"37258573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KIF5A deficiency in human iPSC-derived motor neurons reduces neurite complexity at DIV14, impairs axonal regeneration, decreases mitochondria motility and anterograde speed at DIV42, and strongly reduces anterograde transport of SFPQ-associated RNA granules at DIV42, with no effect on neurofilament transport.\",\n      \"method\": \"KIF5A null iPSC-derived human motor neurons, live axonal transport imaging of mitochondria, SFPQ granules, and neurofilaments, axonal regeneration assay\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — isogenic human KO model with cargo-specific transport assays using live imaging; multiple orthogonal cargo analyses; independently replicated in preprint\",\n      \"pmids\": [\"39644980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Kif5a knockdown in developing retinal ganglion cells decreases anterograde mitochondrial transport while Kif5a overexpression increases mitochondrial motility and anterograde transport, directly establishing Kif5a as a regulator of mitochondrial axonal transport in developing RGCs.\",\n      \"method\": \"shRNA knockdown and AAV overexpression in primary rat RGCs, MitoTracker live-cell imaging with kymography\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional manipulation (KD and OE) with quantitative live imaging of specific cargo; single lab\",\n      \"pmids\": [\"36862119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Full-length autoinhibited KIF5A homodimer adopts a compact bent conformation through a bend between coiled-coils 2 and 3 around P687; crosslinking mass spectrometry reveals interactions between motor domain, coiled-coil 1, and the proximal C-terminal IAK-containing region, but not the distal C-terminal tail; the ALS exon-27-skip mutant retains autoinhibited molecules but its autoinhibited state is more labile.\",\n      \"method\": \"Negative-stain electron microscopy, crosslinking mass spectrometry (XL-MS), AlphaFold2 structure prediction of full-length KIF5A homodimer\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural study with XL-MS and EM; single lab, no mutagenesis validation of specific contacts\",\n      \"pmids\": [\"38309508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ALS-related KIF5A ΔExon27 mutant protein accumulates in human iPSC-derived motor neurons, induces cytoplasmic mislocalization of TDP-43 (an ALS hallmark), and this is exacerbated by overexpression; the altered C-terminal sequence has a basic isoelectric point (unlike acidic WT), and engineering a mutant retaining the aberrant sequence but with lower pI reduces protein aggregation and TDP-43 mislocalization, demonstrating that the isoelectric shift drives KIF5A aggregation and TDP-43 pathology.\",\n      \"method\": \"iPSC-derived motor neuron overexpression, pI-modified KIF5A variants, immunofluorescence for TDP-43 localization and KIF5A aggregation, primary neuron overexpression\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — engineered pI rescue experiment with defined molecular readout; single lab, novel mechanistic claim\",\n      \"pmids\": [\"40555518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FAK signaling promotes KIF5A expression and neuronal differentiation by downregulating epigenetic modifiers DNMT1 and KDM5A; FAK activity is phosphorylation-dependent and required for KIF5A upregulation, which in turn regulates mitochondrial dynamics during differentiation.\",\n      \"method\": \"FAK inhibition/activation, DNMT1/KDM5A knockdown, KIF5A overexpression/knockdown, mitochondrial morphology assay in differentiating neurons\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, signaling pathway study with limited mechanistic resolution on KIF5A's direct role\",\n      \"pmids\": [\"41084333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMN protein associates with KIF5A mRNA and contributes to its stability; SMN deficiency in human neurons and SMA mouse models downregulates KIF5A, and KIF5A overexpression rescues impaired axon regeneration caused by SMN loss, placing KIF5A downstream of SMN in a pathway linking SMA and ALS pathophysiology.\",\n      \"method\": \"RNA immunoprecipitation of SMN with KIF5A mRNA, SMN knockdown in human neurons and SMA mouse model, KIF5A overexpression rescue of axon regeneration\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-IP establishing direct SMN-KIF5A mRNA interaction plus epistatic rescue experiment; single lab\",\n      \"pmids\": [\"41885937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KIF5A mutations causing ALS (exon 27 skipping) abolish KIF5A axonal interaction with SFPQ cargo and, under stress conditions, iPSC-derived motor neurons carrying an intronic KIF5A variant (c.2993-6C>A) exhibit TDP-43 proteinopathy, linking KIF5A ΔExon27-mediated cargo transport failure to TDP-43 pathology.\",\n      \"method\": \"iPSC-derived motor neurons from patients and controls, RT-PCR for exon 27 splicing, immunofluorescence for KIF5A-SFPQ axonal colocalization and TDP-43 localization under stress\",\n      \"journal\": \"Neurology. Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient iPSC model with specific cargo and pathology readouts; single lab\",\n      \"pmids\": [\"41836882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KIF5A directly binds mRNAs encoding synaptic ribosomal proteins and is required for their synaptic localization and normal synaptic composition and function; KIF5A also binds G3BP1 and stress granule-associated proteins; ALS-linked KIF5A mutations enhance mRNA binding, increase synaptic ribosomal protein accumulation, induce neuronal hyperexcitability, and impair stress responses—a gain-of-function RNA-binding mechanism.\",\n      \"method\": \"CLIP/RNA immunoprecipitation, KIF5A loss-of-function, ALS mutant overexpression in patient iPSC motor neurons, electrophysiology, stress granule co-IP\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RNA binding demonstrated by CLIP, functional KO plus mutant gain-of-function with electrophysiology; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"41279899\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KIF5A from giraffes and pythons moves 25% faster than mouse KIF5A on neuronal microtubules due to three amino acid substitutions (R114Q, S155A, Y309F); structural analysis reveals accelerated ADP release underlies enhanced velocity; the motor generates less force but maintains cargo transport under load and exerts less drag in multi-motor environments—demonstrating that the KIF5A mechanochemical cycle is tunable and that ADP release rate is rate-limiting for velocity.\",\n      \"method\": \"In vitro single-molecule motility assay, live imaging in cultured mouse hippocampal neurons, cryo-EM/structural analysis, site-directed mutagenesis of velocity-determining residues\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and structural analysis; preprint, not peer-reviewed\",\n      \"pmids\": [\"40654747\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPG10 mutations in KIF5A cause loss of colocalization with α-tubulin; a splice-site mutation (c.446-2A>G) destroys the donor site leading to exon 6 skipping producing truncated proteins with reduced expression that lose microtubule colocalization, while four missense mutations retain normal mRNA/protein levels but also lose α-tubulin colocalization, indicating that both haploinsufficiency and abnormal subcellular localization underlie SPG10.\",\n      \"method\": \"In vitro minigene splicing assay, protein expression analysis, immunofluorescence co-localization with α-tubulin in transfected cells, iPSC motor neuron functional validation\",\n      \"journal\": \"Parkinsonism & related disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional splicing assay plus subcellular localization in multiple mutants; single lab\",\n      \"pmids\": [\"40945307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The SPG10 variant p.R17Q in the KIF5A motor domain (predicted to affect ATP binding) causes increased KIF5A distribution in distal neurites with neurofilament-positive axonal swellings, and significantly reduces anterograde velocity and distance of mitochondria and lysosomes along neurites in isogenic iPSC-derived motor neurons, confirming pathogenicity and establishing defective axonal transport as the mechanism.\",\n      \"method\": \"CRISPR-Cas9 isogenic iPSC correction, live axonal transport imaging of mitochondria and lysosomes by kymography, immunofluorescence for KIF5A distribution and neurofilament swellings\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isogenic CRISPR-corrected human iPSC model with quantitative cargo-specific transport assays; single lab\",\n      \"pmids\": [\"41836058\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KIF5A is a neuron-enriched kinesin-1 heavy chain that powers anterograde axonal transport of diverse cargoes—including neurofilaments, mitochondria, GABA-A receptors (via GABARAP adaptor), SFPQ-RNA granules (via KLC1 adaptor), synaptic ribosomal protein mRNAs, lysosomes, and collagen vesicles—adopting an autoinhibited compact bent conformation in its inactive state; disease mutations in the motor/stalk domain (SPG10/CMT2) impair microtubule-stimulated ATPase activity and cargo flux through dominant-negative or haploinsufficiency mechanisms, while ALS-linked C-terminal exon-27-skipping mutations produce a constitutively active, hyperprocessive motor with a novel basic-pI C-terminus that aggregates, acquires gain-of-function RNA-binding properties, mislocalizes TDP-43, and disrupts axonal transport homeostasis in motor neurons.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KIF5A is a neuron-enriched kinesin-1 heavy chain that powers anterograde axonal transport of multiple cargoes and is required for axon and neuron survival [#1, #18]. Loss-of-function studies establish a broad cargo repertoire: neurofilament subunits transported by slow axonal transport [#1], mitochondria whose motility KIF5A bidirectionally controls in motor neurons and retinal ganglion cells [#4, #15, #19], GABA-A receptors delivered to the neuronal surface via the GABARAP adaptor [#5], and SFPQ-RNA granules carried within a tetrameric complex with the KLC1 adaptor [#10]. Cargo specificity is encoded in the C-terminal tail domain, as domain-swap rescue experiments demonstrate [#7], and KIF5A also transports collagen-1 vesicles in non-neuronal mesothelial cells [#8]. The motor adopts an autoinhibited compact bent conformation involving contacts between the motor domain, coiled-coil 1, and the proximal IAK-containing C-terminus [#20]. Two genetically distinct disease mechanisms emerge. SPG10/CMT2 mutations in the motor and neck domain abolish processive movement and microtubule-stimulated activity, acting through dominant-negative reduction of cargo flux and loss of microtubule colocalization [#0, #2, #27], and impair SFPQ-motor complex binding [#10]. In contrast, ALS-linked exon-27-skipping mutations relieve autoinhibition to produce a constitutively active, hyperprocessive, self-associating motor that aggregates and is neurotoxic in vivo [#11, #13]; the aberrant basic-pI C-terminus drives this aggregation and the cytoplasmic mislocalization of TDP-43 [#21], while enhanced gain-of-function RNA binding mislocalizes synaptic ribosomal protein mRNAs and induces hyperexcitability [#25]. KIF5A expression is itself regulated downstream of SMN, which stabilizes KIF5A mRNA and links it to spinal muscular atrophy pathophysiology [#23].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established KIF5A as a disease gene and tied its motor function to axonal transport by showing a motor-domain mutation that blocks microtubule-stimulated ATPase activity causes SPG10.\",\n      \"evidence\": \"Human linkage/sequencing with functional inference from orthologous kinesin biochemistry\",\n      \"pmids\": [\"12355402\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ATPase defect inferred from ortholog rather than measured on human KIF5A\", \"no direct cargo or transport assay in this study\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined the first physiological cargo by showing KIF5A is required for slow axonal transport of neurofilaments in vivo, distinguishing it from fast transport.\",\n      \"evidence\": \"Neuron-specific conditional KIF5A knockout mouse with neurofilament accumulation and axon caliber morphometry\",\n      \"pmids\": [\"12682084\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"mechanism of neurofilament cargo coupling not defined\", \"did not address other cargoes\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Resolved how SPG10 mutations act mechanistically, revealing two distinct dominant-negative modes (slowed transport vs. reduced cargo microtubule binding) at single-molecule resolution.\",\n      \"evidence\": \"In vitro gliding, laser-trap single-molecule, and quantum-dot mixed wild-type/mutant cargo transport assays\",\n      \"pmids\": [\"18203753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"in vitro reconstitution may not capture neuronal regulatory context\", \"did not test endogenous cargo specificity\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed SPG10 N256S reduces neurofilament transport flux in both directions, demonstrating interdependence of anterograde and retrograde motors.\",\n      \"evidence\": \"Live-cell neurofilament transport imaging in mutant-expressing cortical neurons\",\n      \"pmids\": [\"21087519\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single method, single lab\", \"molecular basis of bidirectional coupling unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Expanded the cargo repertoire and disease relevance by establishing KIF5A in mitochondrial transport and in GABA-A receptor surface delivery via GABARAP, with epileptic phenotypes.\",\n      \"evidence\": \"Constitutive and conditional KIF5A knockout mice, co-IP with GABARAP, surface biotinylation, EEG, and live mitochondrial imaging; Drosophila SPG10 genetic epistasis\",\n      \"pmids\": [\"22466687\", \"23217743\", \"23209432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"structural basis of GABARAP binding not defined\", \"whether SPG10 is purely dominant-negative vs. haploinsufficient debated across models\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Localized cargo specificity to the C-terminal tail by showing only motors carrying the Kif5Aa C-tail rescue the mitochondrial transport and axon degeneration phenotype.\",\n      \"evidence\": \"Zebrafish kif5Aa mutant chimeric rescue and genetic epistasis with live mitochondrial imaging\",\n      \"pmids\": [\"25355224\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"specific tail-domain adaptors for mitochondria not identified\", \"model-organism ortholog\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended KIF5A function beyond neurons by identifying it as the motor for procollagen-1 vesicle transport and secretion in mesothelial cells.\",\n      \"evidence\": \"Super-resolution and proximity-ligation imaging, siRNA knockdown, live co-imaging of GFP-KIF5A and collagen-1\",\n      \"pmids\": [\"28676645\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"cargo adaptor for collagen vesicles unknown\", \"single non-neuronal cell type\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified C-terminal splice-site/exon-27 mutations as a familial ALS mechanism, initially framed as loss-of-function via haploinsufficiency.\",\n      \"evidence\": \"Whole exome sequencing, rare-variant burden analysis, and patient lymphoblast mRNA/splice analysis\",\n      \"pmids\": [\"29342275\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"loss-of-function interpretation later complicated by gain-of-function findings\", \"patient cells not motor neurons\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the SFPQ-RNA granule transport pathway by identifying a KIF5A/KLC1/SFPQ tetrameric complex required for axon survival, and showed CMT mutations disrupt it.\",\n      \"evidence\": \"Co-IP of the tetrameric complex, loss-of-function axon degeneration assay, disease-mutation validation, and local-translation rescue\",\n      \"pmids\": [\"33284322\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RNA content of granules not fully cataloged\", \"stoichiometry within the complex not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Reframed the ALS mechanism as toxic gain-of-function by showing exon-27-skip mutants relieve autoinhibition to become constitutively active, hyperprocessive, self-associating, aggregation-prone, and neurotoxic across systems.\",\n      \"evidence\": \"Single-molecule motility and processivity assays with purified protein, EM of aggregates, co-IP and RNA profiling, and Drosophila and C. elegans models\",\n      \"pmids\": [\"35385738\", \"35430760\", \"35735139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"how hyperactivity translates to cell death not fully defined\", \"relative contribution of transport dysregulation vs. aggregation unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked KIF5A to excitatory/inhibitory balance and to neurodegeneration via mitochondrial transport, showing it differentially routes GABA-A vs. AMPA receptors in seizure and is required for retinal ganglion cell survival.\",\n      \"evidence\": \"Co-IP in seizure models with receptor recycling/surface assays; in vivo RGC knockout/knockdown/overexpression with mitochondrial transport imaging\",\n      \"pmids\": [\"36388788\", \"35259089\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"mechanism of receptor-selectivity switching unknown\", \"single-lab disease-model contexts\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established cargo-selective transport deficits in human cells and uncovered upstream regulation of KIF5A by TLR7/autophagy signaling affecting inhibitory transmission.\",\n      \"evidence\": \"KIF5A-null iPSC motor neurons with cargo-specific live imaging (mitochondria, SFPQ granules, neurofilaments); TLR7 KO mice with co-IP and seizure assays; Drosophila ΔExon27 motor-neuron model; RGC bidirectional manipulation\",\n      \"pmids\": [\"39644980\", \"37258573\", \"37748861\", \"36862119\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"why neurofilament transport is spared in human iPSC neurons unexplained\", \"direct regulators of KIF5A expression beyond TLR7 incomplete\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided a structural basis for autoinhibition, defining the compact bent conformation and showing the ALS exon-27-skip mutant retains but destabilizes this state.\",\n      \"evidence\": \"Negative-stain EM, crosslinking mass spectrometry, and AlphaFold2 modeling of the full-length homodimer\",\n      \"pmids\": [\"38309508\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"specific autoinhibitory contacts not validated by mutagenesis\", \"no high-resolution structure\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Elucidated the molecular driver of ALS aggregation and RNA-based gain-of-function, showing the basic-pI C-terminus causes aggregation and TDP-43 mislocalization and that enhanced mRNA binding mislocalizes synaptic ribosomal transcripts.\",\n      \"evidence\": \"pI-engineered KIF5A variants in iPSC motor neurons, TDP-43 immunofluorescence, CLIP/RNA-IP, electrophysiology, and stress-granule co-IP (one preprint)\",\n      \"pmids\": [\"40555518\", \"41279899\", \"41836882\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RNA-binding mechanism of an otherwise non-RNA-binding motor not structurally defined\", \"link between aggregation and transport failure quantitatively unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed KIF5A within an SMN-dependent pathway and refined the SPG10 mechanism with tunable mechanochemistry and isogenic disease models.\",\n      \"evidence\": \"SMN RNA-IP and SMA rescue experiments; isogenic CRISPR SPG10 iPSC motor neurons with cargo transport imaging; cross-species single-molecule and structural ADP-release analysis (one preprint)\",\n      \"pmids\": [\"41885937\", \"40945307\", \"41836058\", \"40654747\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"how SMN-dependent KIF5A regulation intersects ALS gain-of-function unclear\", \"ADP-release tuning not tested in disease context\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How autoinhibition is physiologically relieved at cargo-loading sites, and how a hyperactive aggregating motor causes selective motor-neuron death, remain the central open mechanistic questions.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no high-resolution structure of the activated cargo-bound motor\", \"causal chain from ΔExon27 hyperactivity/aggregation to neurodegeneration unresolved\", \"adaptors linking the tail to most cargoes incompletely defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003774\", \"supporting_discovery_ids\": [2, 11, 13, 26]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 26]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 7, 27]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [10, 25]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2, 27]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11, 13, 21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1, 5, 7, 10]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [4, 8, 15]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 9, 11, 13]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [5, 14, 17]}\n    ],\n    \"complexes\": [\"KIF5A/KLC1/SFPQ transport complex\"],\n    \"partners\": [\"GABARAP\", \"KLC1\", \"SFPQ\", \"G3BP1\", \"SMN\", \"GluR2\", \"GABRB2\", \"TDP-43\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}