Expression of the Alzheimer amyloid precursor gene transcripts in the human brain.

An alternate form of the Alzheimer amyloid protein precursor mRNA that encodes a protease inhibitor domain has recently been reported. Oligonucleotide probes that differentiate between the two mRNAs are used to describe the expression of each amyloid precursor transcript in the human brain. RNA blot analyses show that one of the mRNAs is expressed selectively in the nervous system, that the two messages display different regional distributions in the adult human brain, and that the expression of the two mRNAs is differentially affected in Down's syndrome brain and in Alzheimer's disease frontal cortex. In situ hybridization shows that the two transcripts display the same laminar distribution in the adult cortex but that the transcripts differ significantly in their levels of expression in pyramidal cells of the hippocampus.