Tau aggregates assembled from 3R or 4R isoforms have structurally distinct conformations and are related to the development of different types of tauopathies (Scheres et al., 2020; Vaquer-Alicea et al., 2021); however, many common tauopathies including AD and FTD have tau aggregates composed of both 3R and 4R isoforms (Iqbal et al., 2016; Zhang et al., 2022). The gene discussed is MAPT; the disease is Alzheimer disease.