Correction of splicing defect in compound heterozygous FRDA patient carrying FXN 165+5G>C point mutation.

Friedreich’s ataxia is an autosomal recessive disease caused by mutations in the FXN gene. Approximately 95% of patients harbor homozygous GAA repeat expansion in the intron 1 of the FXN, while the remaining 5% are compound heterozygotes carrying GA expansion on 1 allele and point mutation on the other allele. Here, we characterized a G to C transversion in position 5 of the intron 1 of the FXN. Mutation results in profound downregulation of FXN mRNA and protein levels. Transcriptome and RT-PCR analyses demonstrated aberrant splicing of the FXN gene caused by this mutation that can be at least in part corrected with antisense oligonucleotides (ASOs) targeting intron 1. To define a splicing defect caused by FXN 165=5GtoC mutation in the intron 1 of the frataxin gene we established primary skin fibroblast from Friedreich’s ataxia patient carrying this mutation. After 3 passages total RNA was extracted using Qiagen RNeasy RNA extraction kit and subjected to deep RNA sequencing to identify splicing abnormalities in the FXN locus.