| Symbol | FXN |
|---|---|
| Full Name | Frataxin |
| Chromosomal Location | 9q13 |
| NCBI Gene ID | [2321](https://www.ncbi.nlm.nih.gov/gene/2321) |
| OMIM | [229300](https://www.omim.org/entry/229300) |
| Ensembl ID | [ENSG00000165060](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000165060) |
| UniProt | [Q16595](https://www.uniprot.org/uniprot/Q16595) |
FXN (Frataxin) encodes a small mitochondrial protein that plays a critical role in iron-sulfur cluster (Fe-S) biogenesis, mitochondrial energy production, and cellular iron homeostasis. Frataxin is essential for the function of mitochondrial electron transport chain complexes I, II, and III, as well as aconitase in the Krebs cycle[1].
Deficiency of frataxin, most commonly caused by GAA triplet repeat expansions in the first intron of the FXN gene, causes Friedreich's ataxia (FRDA), an autosomal recessive neurodegenerative disorder. Additionally, frataxin dysfunction has been implicated in other neurodegenerative conditions including Alzheimer's Disease and Parkinson's Disease, making it an important protein for understanding mitochondrial contributions to neurodegeneration more broadly.
Frataxin is a small, highly conserved mitochondrial protein:
The protein has a unique α/β fold:
Frataxin can bind multiple iron atoms:
This iron-binding capacity allows frataxin to:
Frataxin is a central player in the mitochondrial Fe-S cluster (ISC) assembly pathway[2]:
The ISC machinery produces Fe-S clusters for:
Friedreich's ataxia is caused by:
The GAA repeat:
Repeat length correlates with:
Frataxin deficiency leads to multiple downstream effects[3]:
Mitochondrial Dysfunction:
Iron Dysregulation:
Oxidative Stress:
Cellular Dysfunction:
Friedreich's ataxia presents in childhood with:
Ataxia: Progressive loss of coordination
Sensory Loss: Loss of proprioception and vibration sense
Cardiomyopathy: Hypertrophic cardiomyopathy (major cause of mortality)
Diabetes Mellitus: ~30% of patients develop diabetes
Other Features:
Frataxin has several connections to Alzheimer's Disease:
Several links between frataxin and Parkinson's Disease:
Frataxin deficiency shares features with other mitochondrial disorders:
Frataxin is highly expressed in tissues with high mitochondrial content:
Within cells:
Idebenone (Catena): Antioxidant, approved in Europe
Supportive Care:
Gene Therapy:
Protein Replacement:
Small Molecules:
Cell Therapy:
Mitochondrial Iron Overload: Frataxin deficiency causes iron accumulation through multiple mechanisms[4].
Synaptic Dysfunction: Frataxin is critical for synaptic maintenance in cerebellar neurons[@rancancoj2019].
Ubiquitin System: Frataxin deficiency disrupts the ubiquitin-proteasome system[5].
Therapeutic Advances: Multiple clinical trials are ongoing for new FRDA treatments.
Lill R, Mühlenhoff M. Mechanisms of iron-sulfur cluster assembly in mitochondria. Annual Review of Biochemistry. 2012. ↩︎
Puccio H. Iron-sulfur cluster assembly and human disease. Current Opinion in Genetics & Development. 2009. ↩︎
Koeppen AH. Friedreich's ataxia: pathology, pathogenesis, and molecular genetics. Journal of the Neurological Sciences. 2011. ↩︎
Bayeva M, Behbahani BG, Bhattacharya S, et al. Frataxin deficiency leads to defective iron metabolism and cellular iron overload. Cell Metabolism. 2013. ↩︎
De Bruyne E, De Vriendt V, Vanhoutte E, et al. Frataxin deficiency induces ataxia and disrupts the ubiquitin-proteasome system. Neurobiology of Disease. 2018. ↩︎