MAPT and Mental deterioration: Two independent reports followed demonstrating cortical Tau hyperphosphorylation in the R6/2 transgenic (TG) mouse model of HD.20, 21 Furthermore, we showed that the rate of cognitive decline in a large cohort of HD patients was greater in those possessing the H2 haplotype of the Tau gene (microtubule-associated protein Tau (MAPT)) compared with those with the H1 haplotype.22