MTA2 and Alzheimer disease: Tauopathies are further defined by the isoform abundance in their inclusions; specifically, AD aggregates contain both 3R and 4R tau (Goedert et al., 1989a; Jakes et al., 1991), PiD is mostly 3R tau (De Silva et al., 2003), and tau inclusions in CBD are mostly 4R tau (Sergeant et al., 1999).