Representative electrophoregrams of PCR fragments from the amplification of GAA repeats in intron 1 of the frataxin gene in patients with FRDA and in healthy individuals are shown in Figure 1A and 1B, respectively. Polymerase chain reaction analyses of heterozygotes for expanded GAA alleles are shown in Figure 2. Of the 15 patients diagnosed with spinal cerebellar ataxia before 25 years of age, 14 (93.3%) were homozygous for the GAA expansion and all had two expanded alleles of same size and no detectable somatic instability. Only one patient with early onset of spinal cerebellar atax ia had two normal alleles, and this result excluded the diagnosis of FRDA. The 25 patients with late onset spinal cerebellar ataxia had two alleles in the normal size range (5-50 GAA repeats). Ten of these were heterozygotes and 15 were homozygous for normal alleles which excluded the diagnosis of FRDA.Molecular analysis of intron 1 of the frataxin gene in healthy individuals showed a range of GAA repeats from 5 to 50. Our results are concordant with already published data [1-4]. This long-range PCR protocol can be used as a diagnostic tool for FRDA and carrier detection.

Figure 1. Agarose gel electrophoresis of PCR products of intron 1 of the frataxin gene in healthy individuals (lanes 1-7) with different numbers of GAA repeats (A), and of seven patients with FRDA (lanes 1-7) (B); M: molecular weight marker.