C9orf72 and frontotemporal dementia: Although these proposed pathomechanisms are not mutually exclusive, these DPRs, namely glycine–alanine (GA), glycine–arginine (GR), glycine–proline (GP), proline–alanine (PA), and proline–arginine (PR) have been, respectively, identified in ALS or FTD patients with C9orf72 repeat expansions and thus drawn enormous attention18,19.