Lower expression of 3′ tRFs (except 3′ tRF SerCGA in the SOD1 ALS model and 3′ tRF Gly in the FTD model), formed by cleavage in the T loop of the tRNA, in the ALS and FTD animal models suggests lower activity of DICER or other RNases in the mutant than in WT. Here, DICER1 is linked to frontotemporal dementia.