| Topic | Key evidence-based findings | Identifiers / exact numbers | Evidence type | Source |
|---|---|---|---|---|
| Disease identity / inheritance | Giant axonal neuropathy (GAN; GAN1) is a rare pediatric neurodegenerative disorder affecting central and peripheral nervous systems; inheritance is autosomal recessive and due to biallelic loss-of-function variants in **GAN** encoding gigaxonin. Distinct early-onset severe and milder later-onset CMT-like phenotypes are described. | OMIM/MIM **#256850**; **GAN** at **16q23.2** (also reported as 16q24.1 in older literature); MeSH **D056768**; >75 families known to investigators. | Human clinical / disease resource / review | DOI: 10.3390/jpm13010091; DOI: 10.1056/NEJMoa2307952; ClinicalTrials.gov **NCT02362438** (pqac-00000000, pqac-00000001, pqac-00000015, pqac-00000017, pqac-00000021) |
| Core phenotype & natural history | Typical onset at **3–5 years** with clumsy or unsteady gait/sensory ataxia, progressive distal>proximal weakness, areflexia, hypotonia, gait disturbance, and characteristic tightly curled/frizzy hair; later features include cerebellar dysfunction, vision loss, contractures, respiratory complications, and loss of ambulation. Most patients become wheelchair dependent by the second decade and often die from pulmonary/respiratory complications by the second to third decade. | German cohort (n=15): gait disturbance **100%**, muscle weakness **100%**, hypotonia **93.3%**, curly/frizzy hair **93.3%**, distal weakness **80%**, abnormal reflexes **80%**, areflexia **73.3%**, frequent falls **66.7%**, joint contractures **53.3%**, respiratory abnormality **53.3%**, intellectual disability **26.7%**. | Human cohort / review / natural history | DOI: 10.1007/s00415-024-12744-z; DOI: 10.3390/jpm13010091; ClinicalTrials.gov **NCT01503125** (pqac-00000002, pqac-00000003, pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000020, pqac-00000023) |
| Diagnosis | Diagnosis integrates clinical phenotype plus molecular confirmation. Electrophysiology shows length-dependent sensorimotor neuropathy with markedly reduced or absent CMAP/SNAP amplitudes; EMG shows chronic denervation/neuropathic changes. MRI often shows cerebellar and periventricular white-matter hyperintensities/leukoencephalopathy. Nerve/skin/sural biopsy or EM shows enlarged axons packed with neurofilaments and thin/decreased myelin sheaths. | Trial/natural-history assessments included **NCS, MUNE, SSEP, BAER, PFT**, MRI, nerve biopsy, skin biopsy. Inclusion in interventional trial required pathogenic variants on both GAN alleles. | Human clinical / diagnostic / trial protocol | DOI: 10.3390/jpm13010091; ClinicalTrials.gov **NCT01503125**, **NCT02362438** (pqac-00000004, pqac-00000005, pqac-00000015, pqac-00000016) |
| Molecular mechanism | Gigaxonin is a low-abundance **BTB/BACK/Kelch** adaptor for a **CUL3-RBX1 E3 ubiquitin ligase** complex. Loss of gigaxonin impairs ubiquitination/degradation of intermediate filament proteins, causing IF/neurofilament accumulation, giant axons, axonal dysfunction, and multisystem cytoskeletal pathology. Gigaxonin also regulates autophagosome production via **ATG16L1** turnover and broader proteostasis. | Gigaxonin protein ~**65 kDa**; GAN gene has **11 exons**; variant counts reported as **89** (2022 database summary) and ~**100–150** across broader literature. | Mechanistic review / in vitro / animal | DOI: 10.3390/jpm13010091; DOI: 10.1172/jci.insight.127751 (pqac-00000007, pqac-00000012, pqac-00000013) |
| 2023 mechanistic advances | 1) **CRL3^gigaxonin–USP15** pathway shown to govern destruction of **NEFL** and **INA**; Kelch-domain variants **L309R, R545C, C570Y** disrupted substrate binding and caused NF accumulation. 2) Loss of gigaxonin was shown to dramatically inhibit **intermediate-filament transport** along microtubules by **kinesin-1**, with **>20-fold** increase in soluble vimentin oligomers in KO cells. 3) New overt mouse model (**Gan−/−;TgPer**) linked NF disorganization to sensory-motor deficits, cognitive deficits, neuroinflammation, and neuron loss. | PNAS 2023; FASEB J 2023; J Neurosci 2023. Gan−/−;TgPer mice had giant axons **≥160 μm²**. | Mechanistic human-cell / mouse model | DOI: 10.1073/pnas.2306395120; DOI: 10.1096/fj.202202119R; DOI: 10.1523/JNEUROSCI.1959-22.2023 (pqac-00000018, pqac-00000019, pqac-00000023) |
| 2024 scAAV9/JeT-GAN gene-therapy trial | First-in-human open-label intrathecal dose-escalation study of **scAAV9/JeT-GAN** in children with genetically confirmed GAN. A single dose was given to **14 participants** across four dose levels. Primary endpoint: safety. Key secondary endpoint: ≥95% posterior probability of slowing decline in **MFM-32 total percent score** at 1 year versus pretreatment slope. | Doses: **3.5×10^13 vg (n=2)**, **1.2×10^14 vg (n=4)**, **1.8×10^14 vg (n=5)**, **3.5×10^14 vg (n=3)**. Median observation **68.7 months** (range **8.6–90.5**). Serious AEs **48**, with **1** possibly treatment-related (fever). Total AEs **682**, with **129** possibly treatment-related. Mean pretreatment MFM-32 slope **−7.17 percentage points/year** (95% credible interval **−8.36 to −5.97**). Posterior mean slope changes at 1 year: **−0.54**, **3.23**, **5.32**, **3.43** percentage points by ascending dose. Posterior probabilities for slowing slope: **44%**, **92%**, **99%**, **90%**; efficacy threshold met at **1.8×10^14 vg**. Sensory-nerve action potentials increased/stabilized/became recordable in **6** participants and remained absent in **8**. | Interventional phase 1 human trial | DOI: 10.1056/NEJMoa2307952; ClinicalTrials.gov **NCT02362438**; PMID **38507752** (pqac-00000015, pqac-00000016, pqac-00000020, pqac-00000021, pqac-00000022, pqac-00000026) |
| Current standard care | No approved curative therapy; management is supportive and multidisciplinary. Reported measures include physical therapy, occupational therapy, speech therapy, aquatic therapy, bracing/orthotics, pain control, respiratory monitoring/support, feeding support, and orthopedic management as needed. | Reviews note need for ventilation/tracheostomy and feeding tube in advanced disease; trial exclusion criteria used **FVC ≤50% predicted** or daytime ventilator dependence, reflecting major respiratory involvement in advanced GAN. | Review / supportive care / trial protocol | DOI: 10.3390/jpm13010091; ClinicalTrials.gov **NCT02362438** (pqac-00000000, pqac-00000015, pqac-00000016, pqac-00000024) |
| Main model systems | Multiple disease models are in use: **Gan knockout mice**, **Gan−/−;TgPer** mice, disease-mutation **GANA49E/A49E** mice, **patient-derived fibroblasts**, **CRISPR GAN−/− SH-SY5Y** cells, **iPSC-derived motor neurons**, and **DRG neuron** models. Preclinical intrathecal AAV9 studies in Gan-knockout rodents supported translation to human trials; rat studies also showed retinal degeneration relevant to disease breadth. | Gan−/−;TgPer model shows early sensory-motor deficits and later cognitive deficits; GANA49E/A49E mouse reportedly recapitulates ataxia, giant axons, demyelination, NF disorganization. iPSC motor-neuron studies showed IF accumulation rescued by gigaxonin restoration. | Mouse / rat / human cell / iPSC / preclinical gene therapy | DOI: 10.1523/JNEUROSCI.1959-22.2023; DOI: 10.1186/s40478-025-02138-1; DOI: 10.1172/jci.insight.127751; ClinicalTrials.gov **NCT02362438** references preclinical AAV work (pqac-00000008, pqac-00000018, pqac-00000025) |


*Table: This table condenses high-value evidence for Giant Axonal Neuropathy across disease definition, phenotype, diagnosis, mechanism, recent research, clinical trial results, standard care, and model systems. It is designed as a compact reference for building a disease knowledge-base entry with source-linked quantitative details.*