To accurately model DM1 and DM2 in flies, we generated UAS-CTG and UAS-CCTG transgenic fly lines carrying either 250 CTG (CTG (250)×) or 1100 CCTG (CCTG (1100)×) pure repeats, which are within the pathological range of repeat lengths and mimic the, at least 4 times longer, expansion size in DM2 patients compared with DM125, 31. This evidence concerns the gene CCT3 and myotonic dystrophy type 2.