MAPT and Huntington disease: All these findings regarding altered isoform ratio in HD are very relevant in view of the fact that alteration in the ratio of 4R-Tau and 3R-Tau isoforms is sufficient to cause neurodegeneration (Hutton et al., 1998; Qian and Liu, 2014), as this might contribute per se to HD neurodegeneration independently of other deleterious effects of mHtt, thus becoming a therapeutic target for HD.