MAPT and Alzheimer disease: In search for a cellular model of this relationship, we noted that Tau expressed in Sf9 cells occurs in a reproducibly high state of phosphorylation, at a level that makes it comparable with AD-Tau as follows: about 12 phosphates per Tau molecule (2N4R isoform) in normal growth conditions and about 20 phosphates upon addition of the phosphatase inhibitor okadaic acid.