C9orf72-Associated FTD/ALS: When Less Is More

Hexanucleotide repeat expansions in C9ORF72 cause neurodegeneration in FTD and ALS by unknown mechanisms. A new report, by Donnelly et al. (2013), finds that these repeats trigger a pathogenic gain-of-function cascade that can be corrected by suppressing expression of the repeat transcript, paving the way for therapeutic strategies aimed at eliminating the toxic RNA