Three types of amyloid protein precursor mRNA in human brain: Their differential expression in Alzheimer's disease

Three types of amyloid protein precursor (APP) mRNA, produced by alternative splicing, were detected by Northern blotting in human brains, both control and Alzheimer's disease. These mRNAs encode APP695 consisting of 695 amino acids, APP751 harboring a 56 amino acid insert homologous to a Kunitz-type trypsin inhibitor inside APP695, and APP770 containing an additional 19 amino acid insert. Another possible APP mRNA which encodes "APP714" containing a 19 amino acid insert was not found in brain samples tested. Quantitative analysis revealed that, although the relative expression levels of the three mRNAs were variable among individuals, there was no remarkable change in expression of APP695 and APP751 mRNAs in Alzheimer's disease compared with control, but that APP770 mRNA level was elevated significantly in Alzheimer's disease.