Misregulation of transcription of theB-amyloid precursor protein (APP) gene is implicated in the Pathogenesis of Alzheimer's disease (AD). Several early studies indicated that the APP gene expression might be increased in AD brains. That increases in the APP expression can lead to AD is strongly suggested by its high incidence in Down's syndrome patients with three copies of the gene. AD is a complex disorder with potentially multiple triggers. It is quite possible that disturbance in the transcriptional regulation of APP affects a subset of AD patients. Alternatively, failure to observe consistently a detectable increase in APP mRNA in post-mortem brains may be due to a transient over expression of APP, which may lead to nucleation of amyloid plaques. Our hypothesis is that the APP regulatory pathways play a critical role in AD pathogenesis. Our long-term goal is to study the transcriptional control of the APP gene. We have recently cloned and characterized a 7.9 kb APP promoter region. Here we will examine the role of the upstream regulatory elements (URE) on APP promoter activity and in late-onset AD. This proposal is based on our novel finding that a -75 to +104 bp region regulates APP promoter activity in a cell-type specific manner.
The specific aims are: 1) To determine the coredomain of APP promoter that is essential for its activity and indelibility. Certain upstream regulatory regions that confer basic promoter activity in neurons and astrocytes may respond to activation by growth factors and cytokines, which are produced by activated macrophages during the inflammatory response in AD. Functional characterization of the regulatory regions will be done by a serial deletion strategy and DNA transfection in cell lines and primary cultures. 2) To identify whether URE interacts with a cell type specific nuclear protein. We will study how the specific upstream region interacts with a cell type-specific factor in neurons and astrocytes and how this interaction will be affected in the presence of cytokines and growth factors. 3) To determine the role of URE in the developmental and disease state. Differential effects of the promoter region in cell types might suggest a role for URE during development and differentiation. We plan to examine the levels of URE-binding factor in developmental rat brains, normal and AD brains. 4) To determine the genetic variability of the regulatory region in AD. The genetic variability of the regulatory region may be important for late-onset AD sporadic subjects. We propose to screen genomic DNA for 'promoter elements' and to compare the 'promoter binding factors' in control and AD subjects. 5) To manipulate promoter activity in cell culture. We plan to modify the specific regulatory effect of the APP promoter by in vivo competition experiment and using the antisense oligodeoxynucleotide strategy. Finally, we will correlate promoter studies with levels of APP and AB in control and AD subjects. Understanding the complex interplay between the promoter domains and the transcription factors may suggest novel methods for therapeutic intervention.
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