MAPT and Alzheimer disease: In summary, we confirmed the powerful ApoE4 dosage-dependent effect on CSF Aβ42 levels reported previously, add data on a positive association between ApoE4 allele number and both, CSF t-tau and p-tau levels, with an effect independent of  CSF Aβ42 in amyloid-negative subjects, and show that ApoE genotype affects speed of clinical progression in AD.