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Reduced expression of the mitochondrial protein Frataxin (FXN) is the underlying cause of Friedreich's ataxia. We propose a model of premature termination ofFXNtranscription induced by pathogenic expanded GAA repeats that links R-loop structures, antisense transcription, and heterochromatin formation as a novel mechanism of transcriptional repression in Friedreich's ataxia. [ABSTRACT FROM PUBLISHER]

Friedreich's ataxia (FRDA) is the most common of the inherited ataxias and is associated with GAA trinucleotide repeat expansions within the first intron of the frataxin (FXN) gene. There are expanded FXN alleles from 66 to 1,700 GAA·TTC repeats in FRDA patients and correlations between number of GAA repeats and frataxin protein levels are assumed. Here, we present for the first time frataxin protein levels as well as analysis of GAA triplet repeats in the FXN gene in a population of 50 healthy Austrian people. Frataxin protein levels were measured in lymphocytes from blood samples by ELISA and GAA repeats were analyzed by capillary electrophoresis. Rather unexpectedly, we found a high variation of frataxin protein levels among the individuals. In addition, there was no correlation between frataxin levels, GAA repeats, age and sex in this group. However, these findings are of great importance for better characterization of the disease. [ABSTRACT FROM AUTHOR]