UASt regulatory sequences are fused upstream of a 5'UTR sequence into which a 28 G[[4]]C[[2]] repeat cassette (this sequence is derived from an intron of the human C9ORF72 gene) has been inserted, followed by the EGFP coding region. The repeat cassette is in the 1+ reading frame (GP) relative to EGFP and this construct acts as a reporter for RAN translation in this frame.