Spatial and temporal control of age-related APP processing in genomic-based β-secretase transgenic mice

Genetic mutations associated with Alzheimer's disease (AD) in the Amyloid Precursor Protein (APP) gene specifically alter the production of the APP processing product, amyloid-β (Aβ) peptide, generated by β- and γ-secretases. The accumulation and deposition of Aβ is hypothesized to cause AD pathogenesis, leading to the debilitating neurological deficits observed in AD patients. However, it is unclear how processing of APP to generate Aβ corresponds with the age-dependent pattern of brain-regional neurodegeneration common in AD. We have previously shown that overexpression of BACE1, the primary β-secretase gene, in mice expressing an AD mutant form of APP leads to significantly elevated regional Aβ levels, which coincide with the regional pattern of Aβ deposition. In the current study, we have used our genomic-based β-secretase transgenic mice to determine how BACE1 regulates the spatial and temporal pattern of Aβ production throughout post-natal development. Specifically, we observed unique differences in the brain-regional expression pattern between neonatal and adult BACE1 transgenic mice. These alterations in the BACE1 expression profile directly corresponds with age-related differences in regional Aβ production and deposition. These studies indicate that modulation of BACE1 expression leads to dramatic alterations in APP processing and AD-like neuropathology. Furthermore, our studies provide further evidence that BACE1 plays a major role in the regulation of the APP processing pathway, influencing the age-dependent onset of AD pathogenesis.