The GAA repeats over 66 in number in intron 1 of the frataxin gene are considered as pathogenic, and commonly occurring pathogenic repeats are within a range of 600-1200. Clinically, the spectrum of features is confined mainly to neurological tissues; however, cardiomyopathy and diabetes mellitus have been reported in 60 and 30% of the subjects, respectively. The accurate detection of GAA repeat count is of utmost importance for clinical genetic correlation, and no study so far has attempted an approach that is of high-throughput nature and defines the exact sequence of GAA repeats. Largely, the method for detection of GAA repeats so far is either through the conventional polymerase chain reaction-based screening or Southern blot, which remains the gold standard method. The authors utilized an approach of long-range targeted amplification of FXN-GAA repeats using Oxford Nanopore Technologies MinION platform for accurate estimation of repeat length. Successful amplification of GAA repeats ranging from ∼120 to 1100 at ∼2600× mean coverage was achieved. The total throughput achievable through this protocol can allow for screening of up to 96 samples per flow cell in less than 24 h. The proposed method is clinically scalable and deployable for day-to-day diagnostics.

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