MAPT and Alzheimer disease: In addition to its buildup within neurons, more recent studies demonstrated that tau is also released in the extracellular space (Gómez-Ramos et al., 2006; Avila, 2010); and that increased levels of tau (total and phosphorylated) in the human's cerebrospinal fluid (CSF) are associated with an increased risk of developing AD (Blennow et al., 2010).