Can Mitochondrial Genome Variations Contribute To Friedreich Ataxia Onset?

Friedreich ataxia is an inherited neurodegenerative disease characterized by a progressive impairment of gait movements and sensory functions and an early age onset (< 25 years). This disease is caused by a mutation on the FXN gene (hyper-expansion of GAA trinucleotide repeats) leading to the lack of frataxin, a mitochondrial protein involved in the biogenesis of Fe-S clusters, vital components of the cellular respiratory system. Friedreich ataxia affects 1:40,000 individuals in the Caucasian population. Even though disease onset is intimately related with frataxin deficiency, accumulating evidences suggest that alteration in the patients’ mitochondrial genome might impact the age of disease onset.

To clarify this relation, researchers from New Delhi, India investigated the mitochondrial genome variability of Indian Friedreich ataxia patients. The work, entitled “Investigation of mitochondrial DNA variations among Indian Friedreich’s ataxia (FRDA) patients” was published in the Mitochondrion journal.

The study included a total of 30 clinically and genetically unconfirmed Friedreich ataxia patients and 62 unrelated healthy individuals. Researchers focused on the genetic differences of certain regions of the mitochondrial DNA, namely the ND, ATP-gene and the D-loop regions, which have been identified as hotspots for mitochondrial genetic mutations.

Overall, Friedreich ataxia patients’ mitochondrial genome presented significantly higher alterations compared to that of healthy participants. The authors further found that a majority of Friedreich ataxia patients showed a variation in a mitochondrial DNA region associated with longevity and myocardial infraction. Nonetheless, the team could not establish a relation between the high mutation degree of Friedreich ataxia patients’ mitochondrial genome and the age at onset of the disease. Most likely, mitochondrial DNA alterations in Friedreich’s ataxia are associated to a higher cellular oxidative stress. However, further studies are required to fully understand the causes leading to mitochondrial genome variations in Friedreich ataxia and its implications for disease pathogenesis.