Objective: An agarose-based long-range polymerase chain reaction (PCR) assay was performed on patients with a preliminarydiagnosis of Friedreich’s ataxia (FA). It aimed to determine the repeat number in intron 1 of the FXN gene and to investigate thegenotype-phenotype correlation.Patients and Methods: Nineteen cases participated in the study.
Long-range PCR was performed under appropriate conditions usingtwo custom-designed primer pairs (F1-R1 and F2-R2). The PCR products were run on an agarose gel, and guanine-adenine-adenine(GAA) repeat numbers were determined.Results: Biallelic GAA repeat expansions were detected in 6 patients. Four patients had typical FA.
One had late-onset FA (LOFA).Another had very late-onset FA (VLOFA). All patients diagnosed with FA had ataxia and areflexia. The detected repeat numbers wereapproximately 190-1120 for F1-R1 and 170-1100 for F2-R2. The patient with LOFA had 190/1000 GAA repeats. The VLOFA patienthad 290/290 GAA repeats.Conclusion: An earlier clinical onset correlated with higher GAA repeats.
An agarose-based long-range PCR assay is a quick, low-cost,and effective way to determine GAA repeats. This study shows it can diagnose the disease and identify carriers.