PSEN1 and Alzheimer disease: The mutations in presenilin-1 (PSEN-1) and presenilin-2 (PSEN-2) genes [6], or crosstalk between apolipoprotein E (apoE) isoforms and the encoding genes (ApoE4) mutation and Aβ levels [7], are further good examples of the close association between Aβ and AD; and/or the rational for Aβ targeting by therapeutic agents.