EACR25-0445

Friedreich’s Ataxia and DNA repair: frataxin deficiency can impair DNA damage mechanisms

R. Challita¹, D. Tohme¹, C. Feghaly², H. Bou Hadir², W. Chebli², R. El-Hassan¹, W. Abou Kheir¹, L. Bodgi²

¹American University of Beirut, Department of Anatomy, Cell Biology, and Physiological Sciences, Beirut, Lebanon
²American University of Beirut, Department of Radiation Oncology, Beirut, Lebanon

Introduction:

Many genetic diseases are associated with increased radiosensitivity due to impaired DNA repair mechanisms. One such disease is Friedreich’s Ataxia (FA), a neurodegenerative disorder affecting over 15,000 individuals worldwide. FA is an autosomal recessive disease caused by a GAA triplet expansion in the FXN gene, which encodes the frataxin protein. Symptoms typically appear in childhood or early adolescence, leading to damage in the spinal cord, peripheral nerves, and cerebellum. Some studies suggest that FA cells may exhibit deficiencies in DNA damage repair. Radiation and genotoxic agents induce various types of DNA damage, with DNA double-strand breaks (DSB) being the most lethal. This damage activates DNA repair mechanisms, primarily through two key repair proteins, pATM and γH2AX. This study aims to evaluate the in vitro radiosensitivity of FA skin fibroblast cell lines.

Material and method:

Five human skin fibroblast cell lines (three FA and two normal) were included in this study. Cells were irradiated with a 2 Gy dose, and the kinetics of radiation-induced DNA double-strand break repair were evaluated using anti-pATM and anti-γH2AX immunofluorescence. Cellular radiosensitivity was assessed using a clonogenic assay. MTT and trypan blue assays were performed to evaluate cellular metabolic activity and viability.

Result and discussion:

Without irradiation, the basal number of γH2AX foci was significantly higher in FA cell lines compared to normal cell lines (p < 0.001). However, 24 hours post-irradiation, the number of residual foci remained significantly higher in FA cell lines (p < 0.001). FA cells also exhibited a lower number of pATM foci at 10 minutes and 1 hour post-irradiation (p < 0.001). Additionally, all three FA cell lines showed a lower surviving fraction than the two normal cell lines (p < 0.05).

Conclusion:

Our findings indicate that FA cell lines exhibit increased sensitivity to genotoxic agents due to deficiencies in their DNA DSB repair mechanisms. These results could help guide the development of treatment strategies for FA by considering their impaired DNA repair capacity.