Genetic studies support a neuronal origin for the beta amyloid polypeptide.

Studies of Alzheimer amyloid protein precursor mRNA expression in the human brain have provided compelling evidence for a neural origin of beta amyloid. Significant alterations in levels of amyloid precursor mRNAs are observed specifically in neurons known to be risk in Alzheimer's disease and Down syndrome. These data raise the possibility that an increase in the transcripts containing the protease inhibitor domain relative to the shorter transcript may account for the accumulation of beta amyloid.