Friedreich’s ataxia (FRDA) is caused by biallelic expansion of GAA repeats leading to the transcriptional silencing of the frataxin (FXN) gene. The exact molecular mechanism of inhibition of FXN expression is unclear. Herein, we analyze the effects of hyperexpanded GAA repeats on transcription status and chromatin modifications proximal and distal to the GAA repeats. Using chromatin immunoprecipitation and quantitative PCR we detected significant changes in the chromatin landscape in FRDA cells relative to control cells downstream of the promoter, especially in the vicinity of the GAA tract. In this region, hyperexpanded GAAs induced a particular constellation of histone modifications typically associated with heterochromatin-like structures.
Hyperexpansion of GAA repeats affects post-initiation steps of FXN transcription in Friedreich's ataxia