Familial Alzheimer's disease with the amyloid precursor protein position 717 mutation and sporadic Alzheimer's disease have the same cytoskeletal pathology

Abstract

The cytoskeletal pathology of a patient with familial Alzheimer's disease (AD) associated with the probably causal amyloid precursor protein (APP) codon 717 Val→Ile mutation is described. In addition to moderately extensive βA4 protein deposition within the substance of the brain and in blood vessel walls (congophilic angiopathy), there was abundant cytoskeletal pathology in the form of neurofibrillary tangles, plaque neurites and neuropil threads. Interestingly, plentiful cortical and subcortical Lewy bodies were also seen. In order to compare the cytoskeletal pathology in this case with that seen in sporadic cases of AD we (1) studied the immunohistochemical profile of the amyloid and cytoskeletal pathology with antibodies to βA4 protein, tau, phosphorylated neurofilament epitopes and ubiquitin and (2) performed a biochemical fractionation and Western blot analysis for the abnormally phosphorylated form of tau (A68) characteristically seen in AD. No substantial difference between the familial case and sporadic cases could be found. We conclude that it is now reasonable to hypothesise that an abnormality in APP metabolism is responsible not only for the deposition of βA4 protein, but also for the range of cytoskeletal pathology, typical of AD.