Accumulation of amyloid beta protein in transgenic mice

Carboxyl-terminal fragments of beta amyloid precursor protein (betaAPP) were expressed in mice under the transcriptional control of an ubiquitous promoter system, based upon a chicken beta-actin (betaA) promoter combined with cytomegalovirus (CMV) enhancer to obtain a systemic overproduction of amyloid beta protein (Abeta). Three transgene constructs were designed to encode signal peptide and carboxyl-terminal 99 amino acid residues to betaAPP (NOR-beta), methionine and C-terminal 103 amino acid residues of betaAPP (deltaNOR-beta), and methionine and C-terminal 103 amino acid residues with KM-NL substitution of betaAPP (deltaNL-beta). Although the transcriptional mRNA level and post-translational protein level from transgenes showed the same expression pattern, both the expression of Abeta and distribution of Abeta deposits were completely different among these strains. In NOR-beta mice, considerable amounts of Abeta were detected in plasma and Abeta deposits were observed in the pancreas. Brain Abeta deposits and small amounts of plasma Abeta were recognized in deltaNL-beta. These findings indicate that tissue specific processing and transgene constructs are major factors to determine the distribution of Abeta deposits.