Dose-Dependent and Region-Specific Impacts of siRNA mediated APP Knockdown on DNA Damage and Alzheimer's Disease Pathology - PROJECT SUMMARY/ ABSTRACT Amyloid precursor protein (APP) represents a complex therapeutic target in Alzheimer's disease (AD), as its processing generates both toxic amyloid-beta (Aβ) peptides and neuroprotective fragments like soluble APP-α (sAPPα)1. While reducing APP through RNA interference shows preclinical and clinical promise for decreasing Aβ burden2,3, the broader impacts of APP knockdown on essential cellular functions, particularly DNA repair, remain unclear. In this proposal, I aim to investigate the dose dependent and region specific effects of APP reduction on AD pathology and DNA damage in the AppSAA mouse model. My study will utilize chemically modified APP-targeting siRNA administered via intracerebroventricular injection at a low and high dose to examine how varying levels of APP knockdown affect AD pathology and DNA damage in different brain regions. Through innovative techniques including Single-Strand Break mapping using Next-Generation Sequencing (SSiNGLe) and MERSCOPE FISH spatial transcriptomics, I will map DNA damage patterns and gene expression changes across different brain regions. This comprehensive approach will be complemented by behavioral testing and molecular analyses to assess cognitive outcomes and inflammatory responses. I hypothesize that the effects of APP knockdown on DNA damage and AD pathology are dose dependent and region specific, mediated by a balance between Aβ, APP, and sAPPα reduction. While reducing Aβ through APP knockdown may decrease some aspects of AD pathology, the concurrent loss of APP and sAPPα will worsen DNA damage and exacerbate AD pathology, particularly in vulnerable brain regions. The findings from this study will advance our understanding of APP's role in AD pathology and normal brain function, potentially leading to more nuanced therapeutic approaches that consider regional brain vulnerability and the importance of maintaining essential APP functions while reducing toxic Aβ accumulation.
