 A hexanucleotide repeat expansion in the C9-OF72 gene is a common genetic cause of ALS and FTD. The repeats are translated into five different dipeptide repeat proteins, DPRs. In this issue, Lemma et al. 2017, demonstrate that one of these DPRs, Poly, GP, can be measured in the CSF of individuals with C9-OF72 mutations. In conjunction with the findings from another recent study, Gendron et al. 2017, these DPR biomarkers may prove to be extremely valuable in the quest for effective therapies for C9-FTD ALS. This article was authored by Rubika Balindra, Thomas G. Moans and Adrian M. Isaacs.