... University of Toronto, Toronto, Ontario, CanadaSenile plaques, the invariable hallmark and likely proximalcause of Alzheimer’s disease (AD), are structured deposi-tions of the 40- and 42-residue ... and dying neurons [12–14].Correspondence to A. Chakrabartty, Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, ... Also,mutations of the presenilin genes have been linked to familial AD, and appear to lead to an increase in theratio of Ab42 to Ab40 [11]. Transgenic mice overexpressing a mutant form of APP develop...