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GDAP1
ganglioside induced differentiation associated protein 1
GDAP1 is located on the long (q) arm of chromosome 8, at band 8q21.11. Arm ratio per GRCh38 - banding schematic.
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Overview
GDAP1 (ganglioside induced differentiation associated protein 1) encodes a protein integral to mitochondrial function in peripheral nerve cells. The encoded protein belongs to a family of enzymes and participates in regulating mitochondrial shape, distribution, and overall health within neurons. These functions are particularly important in long nerve fibres that extend from the spinal cord to muscles and sensory organs.
Pathogenic changes in GDAP1 disrupt normal mitochondrial dynamics, leading to impaired energy production and eventual nerve degeneration. The gene's name reflects its initial discovery in studies of cell differentiation induced by gangliosides, which are lipid molecules abundant in nerve tissue. Research into GDAP1 has enhanced understanding of how mitochondrial defects contribute to inherited nerve disorders.
What the gene does
The GDAP1 protein resides on the outer membrane of mitochondria, where it influences the balance between mitochondrial fusion and fission. These dynamic processes determine mitochondrial shape, size, and distribution throughout the cell. In peripheral nerve cells, proper mitochondrial distribution ensures adequate energy supply along the entire length of nerve fibres, which can extend up to a metre in humans.
Evidence suggests the protein also participates in mitochondrial transport and quality control mechanisms. When mitochondria become damaged or dysfunctional, cellular systems must identify and remove them to prevent accumulation of defective organelles. The GDAP1 protein appears to coordinate aspects of this quality control process, though the precise molecular mechanisms remain under investigation.
Additionally, the protein may interact with other mitochondrial proteins to regulate calcium signalling and oxidative stress responses within nerve cells. These functions are critical for maintaining neuronal excitability and protecting cells from damage during periods of high metabolic demand.
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Chromosome location
GDAP1 is located on the long arm of chromosome 8 at position 21.11 (8q21.11). The gene spans approximately 18 kilobases of genomic DNA and contains six exons that encode the protein-coding sequence. This chromosomal region contains several other genes involved in diverse cellular functions, but GDAP1 operates independently in its role supporting mitochondrial health in nerve tissue.
Protein structure
The GDAP1 protein comprises 358 amino acids organised into distinct functional regions. The GST N-terminal domain extends from amino acids 24 to 105, whilst the GST C-terminal domain spans amino acids 153 to 309. These domains resemble structures found in glutathione S-transferase enzymes, though GDAP1 does not appear to function primarily as a transferase.
The carboxy-terminal region from amino acids 320 to 358 is required for mitochondrial localisation, ensuring the protein reaches its proper destination on the outer mitochondrial membrane. This targeting sequence directs newly synthesised GDAP1 protein from the cytoplasm to mitochondria, where it can perform its regulatory functions. The overall architecture supports the protein's role in coordinating mitochondrial dynamics and maintaining organelle integrity.
Key variants
Pathogenic variants in GDAP1 follow various inheritance patterns, with both autosomal recessive and autosomal dominant forms documented in medical literature. Recessive variants typically cause more severe disease, whilst dominant variants often result in milder presentations. Most pathogenic changes are missense variants that alter single amino acids, though deletions and frameshift variants also occur. The location of a variant within the protein structure influences disease severity and age of onset.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.311-1G>A | - | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease, axonal, with vocal cord paresis, autosomal recessive |
c.355C>A | p.Pro119Thr | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
c.536del | p.Pro179fs | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
c.571C>T | p.Arg191Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
c.694+1G>A | - | Pathogenic/Likely pathogenic | ★★☆☆ | Inborn genetic diseases |
c.767A>G | p.His256Arg | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease, axonal, with vocal cord paresis, autosomal recessive |
c.786del | p.Phe263fs | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease recessive intermediate A |
c.840del | p.Tyr279_Tyr280insTer | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
c.845G>A | p.Arg282His | Pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
c.929G>A | p.Arg310Gln | Pathogenic/Likely pathogenic | ★★☆☆ | Charcot-Marie-Tooth disease type 4A |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
GDAP1 variants cause hereditary motor and sensory neuropathies, conditions characterised by progressive weakness and sensory loss in the limbs. These neuropathies typically begin in childhood or adolescence, though onset age varies considerably. Affected individuals may experience difficulty walking, foot deformities, and loss of sensation in the hands and feet. The spectrum of GDAP1-related neuropathies ranges from severe early-onset forms causing significant disability to milder presentations with later onset and slower progression. Some affected individuals also develop vocal cord paralysis or involvement of cranial nerves.
No disease links recorded for this gene in our reference set.
UK clinical status
GDAP1 appears on multiple NHS Genomic Medicine Service gene panels with green ratings, indicating strong evidence for clinical use. The gene is included in the Hereditary neuropathy panel and the Hereditary neuropathy or pain disorder panel (R78), reflecting its established role in inherited nerve conditions. It also features on the Mitochondrial disorders panel and Possible mitochondrial disorder - nuclear genes panel (R63), recognising the protein's mitochondrial function. Additionally, GDAP1 is listed on panels for Likely inborn error of metabolism (R98) and Undiagnosed metabolic disorders, supporting comprehensive investigation of patients with unexplained neurological or metabolic presentations.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What inheritance patterns are seen with GDAP1 variants?
GDAP1-related conditions can follow either autosomal recessive or autosomal dominant inheritance patterns. Recessive inheritance, where two variant copies are required, typically causes more severe disease, whilst dominant inheritance, where one variant copy is sufficient, often results in milder symptoms with later onset.
Why does GDAP1 primarily affect nerves rather than other tissues?
Peripheral nerve cells have exceptionally long fibres requiring extensive mitochondrial networks to supply energy throughout their length. These cells appear particularly vulnerable to disruptions in mitochondrial distribution and quality control, making them sensitive to GDAP1 dysfunction even though the protein is present in other tissues.
Is GDAP1 tested on the NHS?
Yes, GDAP1 testing is available through NHS Genomic Medicine Service pathways for patients with hereditary neuropathy, mitochondrial disorders, or unexplained metabolic conditions. Testing typically occurs as part of multi-gene panels rather than single-gene analysis, and requires referral from an appropriate specialist.