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 and has 30bp of flanking sequence on both sides of the repeats) has been inserted, followed by the EGFP coding region. The repeat cassette is in the 1+ reading frame (GP) relative to EGFP.