Adding a temporal dimension to the study of Friedreich's ataxia: the effect of frataxin overexpression in a human cell model

Abstract

The neurodegenerative disease Friedreich's ataxia is caused by lower than normal levels of frataxin, an important protein involved in iron sulphur cluster biogenesis. An important step in designing strategies to treat this disease is to understand whether increasing the frataxin levels by gene therapy would be tout-court beneficial or detrimental since previous studies, mostly based on animal models, have reported conflicting results. Here, we have exploited an inducible model, which we developed using the CRISPR/Cas9 methodology, to study the effects of frataxin overexpression in human cells and follow how the system recovers after overexpression. Using novel tools which range from high throughput microscopy to in cell infrared, we prove that overexpression of the frataxin gene affects the cellular metabolism. It also lead to a significant increase of oxidative stress and labile iron pool levels. These cellular alterations are similar to those observed when the gene is partially silenced, as it occurs in Friedreich's ataxia's patients. Our data suggest that the levels of frataxin must be tightly regulated and fine-tuned, any imbalance leading to oxidative stress and toxicity.