Presenilin Knock-in Rat Model of Neurodegeneration

PROJECT SUMMARY/ABSTRACT Alzheimer's disease (AD) is the most common form of dementia in the elderly, and currently there exists no disease modifying therapy. Familial forms of AD (FAD) are caused by mutations in Amyloid Precursor Protein (APP), whose processing can result in the formation of amyloid beta (Aβ), or by mutations in Presenilin 1/2 (PSEN1/2), which comprise in part the γ-secretase complex that cleaves Aβ from fragments of APP. My long- term career goal is to study the mechanism of neurodegeneration in Alzheimer disease. The more proximate goal, as put forward in this proposal, is to characterize the neurodegeneration in a new rat knock-in model of Presenilin1 dysfunction. Psen1-knockout (Psen1-KO) mice and knock-in (KI) mice with homozygous FAD- associated L435F mutations (Psen1LF/LF) are embryonic and perinatally lethal, precluding a more rigorous examination of the effect of AD-causing Psen1 mutations on neurodegeneration. Given the better suitability of rats as a model organism, with regards to surgical interventions and behavior testing, we generated a rat KI model of the Psen1LF mutation. We find that, unexpectedly and in contrast to Psen1LF/LF, Psen1LF/LF rats survive into adulthood despite a loss of γ-secretase activity. The survival of these rats affords the opportunity to examine the effect of homozygous Psen1 AD mutations on neurodegeneration.