In the next step, Kramer et al. (2016) [90] treated cultured fibroblasts from three C9orf72 ALS patients with siRNAs against Supt4h1 or Supt5h (siSupt4h1, siSupt5h, respectively), decreasing both Supt4h1 and Supt5h mRNA and protein levels, which led to a significantly reduced levels of C9orf72 variant 3 mRNA, poly-glycine-proline DPRs, as well as both sense and antisense repeat RNA foci in C9orf72 fibroblasts, without evidence of toxicity. Here, C9orf72 is linked to amyotrophic lateral sclerosis.