MAPT and Alzheimer disease: Following fractionation of tau protein into sarkosyl-soluble or insoluble fractions from either the cortical or subcortical white matter of the anterior cingulate gyrus of ALSci patients, we observed that in contrast to tau protein isolated from Alzheimer's disease in which the insoluble fraction contained the triplet tau isoforms characteristic of paired helical filaments (PHFs), all six isoforms of tau protein were expressed in both the soluble and insoluble fractions (Strong et al., 2006).