C9orf72 and frontotemporal dementia: In two other studies, C9ORF72 BAC transgenic mouse models were generated that contain the (G4C2)n repeat expansion within either part of or all of the C9ORF72 gene and display both the RNA foci and DPRs, yet surprisingly did not develop signs of neurodegeneration or ALS/FTD phenotypes (50,51).