A novel presenilin-1 mutation: Increased beta-amyloid and neurofibrillary changes

The prevalence of known mutations in presenilin genes (PS1 and PS2) causing early-onset familial Alzheimer's disease (FAD) was assessed in a population of 98 singleton early-onset AD cases, 29 early-onset FAD cases, and 15 late-onset FAD cases. None of the cases tested positive for the eight mutations initially reported, and none of these mutations were observed in 60 age-matched controls. A novel mutation (R269H) in PS1 was found in a single case of early-onset AD but not in any other AD or control case. Thus, the PS mutations tested are quite rare in early-onset AD. Amyloid beta protein (AP) deposition was investigated in the temporal cortex of the R269H mutation case using end-specific monoclonal antibodies to detect the presence of A beta(x-40) and A beta(x-42) subspecies. Stereologically unbiased tangle and neuropil thread counts were obtained from the same region. R269H PS1 mutation was associated with early age of dementia onset, higher amounts of total A beta and A beta(x-42), and increased neuronal cytoskeletal changes. Thus, if the changes observed on this case prove to be typical of PS1 mutations, PS1 mutations may impact both amyloid deposition and neurofibrillary pathology.