Though both genotypes of this mouse were genetically identical with respect to the P301L mutation of tau and murine tau, we surprisingly detected that the total protein amount of transgenic human P301L tau as well as endogenous murine tau was significantly increased in the heterozygous aggrecan genotype compared to the wildtype aggrecan genotype in this mouse model, confirming a regulatory effect of aggrecan on tau expression and indicating a more severe tauopathy when aggrecan is reduced [40]. Here, MAPT is linked to tauopathy.