β‐Amyloid Protein Precursor and τ mRNA Levels Versus β‐Amyloid Plaque and Neurofibrillary Tangles in the Aged Human Brain

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Abstract
To learn whether or not the levels of β‐amyloid protein precursor (APP) and τ mRNAs are related to the formation of β‐amyloid and neurofibrillary tangles, we quantified these mRNA levels in three cortical regions of 38 aged human brains, which were examined immunocyto‐chemically for β‐amyloid and tangles. Marked individual variabilities were noted in APP and τ mRNA levels among elderly individuals. The mean APP mRNA level was slightly reduced in the β‐amyloid plaque (++) group, but not in the plaque (+) group, compared to the plaque (−) group. Some brains in the plaque (−) group showed increased APP expression, the extent of which was not seen in the plaque (+)or(++) group. The differences in the mean τ mRNA levels were not statistically significant among the tangle (−), (+), and (++) groups. These results show that β‐protein and τ deposition do not accompany increased expression of the APP and τ genes, respectively, and thus suggest that factors other than gene expression may be at work in the progression of β‐amyloid and/or tangle formation in the aged human brain.