Due to the position of the P301L mutation in exon 10 encoding microtubule binding repeat 2, it only affects the 4R form of tau (Figure 1A); in this respect, it is notable that P301L pathologies in astrocytes and oligodendrocytes resemble other 4R-tauopathies such as CBD (11). The gene discussed is MAPT; the disease is tauopathy.