Expanded GAA repeat sequence in the frataxin gene

The **expanded GAA repeat sequence in the frataxin gene** refers to the abnormal increase in the number of GAA trinucleotide repeats located within the first intron of the FXN gene, which encodes frataxin[4][6][7]. In most people, this GAA segment is repeated fewer than 33 times, but in individuals with Friedreich ataxia, the GAA segment is repeated 66 to more than 1,000 times[4][7]. This expansion causes transcriptional repression of the FXN gene, reducing frataxin production. The pathogenic mechanism involves abnormal chromatin condensation (heterochromatinization), epigenetic silencing, impaired transcriptional elongation, and sometimes repositioning of the gene to the nuclear periphery[1][2][3]. The resulting frataxin deficiency leads to mitochondrial dysfunction, oxidative stress, and cell death—especially in neurons and cardiac cells—causing the progressive neurodegenerative disease Friedreich ataxia[3][4][5]. The expanded GAA repeat is not a protein or conventional drug target but is a highly significant pathogenic sequence and a molecular biomarker central to disease diagnosis, prognosis, and potential future targeted therapies for Friedreich ataxia[4][7].

Other names

GAA trinucleotide repeat expansion in FXNGAA repeat expansion in the frataxin geneFriedreich ataxia GAA expansionGAA repeat in intron 1 of frataxin

In experimental and preclinical approaches: inhibition of repeat-induced heterochromatin silencing, restoration of histone acetylation, stabilization/prevention of secondary DNA structures (triplexes), transcriptional reactivation of the FXN gene[1][2][3]. Epigenetic drugs (e.g., histone deacetylase inhibitors) aim to counteract gene silencing caused by the repeat expansion.