Frataxin gene GAA repeat expansion (GAA repeat expansion)

The expanded GAA repeat sequence in the first intron of the frataxin (FXN) gene is the primary molecular cause of Friedreich's ataxia (FRDA), a progressive neurodegenerative disorder (Campuzano et al., 1996, Science). In healthy individuals, this region typically contains 5 to 33 GAA repeats, whereas affected individuals possess hundreds to over a thousand repeats, leading to the formation of non-canonical DNA structures like triplexes or R-loops (Groh et al., 2014, PLoS Genetics). These structures, along with the recruitment of histone deacetylases, induce heterochromatin formation and epigenetically silence the FXN gene, resulting in a severe deficiency of the frataxin protein (Saveliev et al., 2003, Nature). Frataxin is essential for mitochondrial iron-sulfur cluster biogenesis, and its loss leads to mitochondrial dysfunction, iron accumulation, and oxidative stress (Rotig et al., 1997, Nature Genetics). Therapeutic strategies targeting this sequence aim to restore frataxin levels through small molecules that recruit transcription factors to the repeat (e.g., GeneTACs), HDAC inhibitors to open the chromatin structure, or gene-editing tools like CRISPR/Cas9 to excise the expansion (Libri et al., 2014, Human Molecular Genetics). Successful modulation of this target is critical for addressing the underlying genetic defect and halting the progression of ataxia and cardiomyopathy in FRDA patients.

Other names

FXN GAA repeatFriedreich's ataxia repeat expansionGAA triplet repeat in FXN intron 1Frataxin (FXN) gene expanded GAA repeat

Transcriptional reactivation of the FXN gene by reversing epigenetic silencing, inhibiting histone deacetylases (HDACs), or using small molecules (GeneTACs) to bypass the transcriptional block caused by the GAA expansion.