Brian D. Ackley (United States of America)
University of Kansas Department of Molecular BiosciencesAuthor Of 1 Presentation
C. ELEGANS MODELS OF FAMILIAL ALZHEIMER'S DISEASE SHOW REDUCED LIFESPAN AND AGE-DEPENDENT SYNAPTIC LOSS INDEPENDENT OF ABETA42
Abstract
Aims
Familial Alzheimer’s disease (FAD) is caused by dominant missense mutations in the substrate and enzyme that produce the amyloid β-peptide (Aβ) that pathologically deposits in the brain. Mutations in the amyloid precursor protein (APP) or in presenilin (the catalytic component of the membrane-embedded γ-secretase complex) alter proteolytic processing, generally increasing the ratio of aggregation-prone Aβ42 to the more soluble Aβ40. We aimed to develop Caenorabditis elegans models for FAD by co-expressing variants of APP substrate C99 and presenilin-1 (PSEN1).
Methods
We developed transgenic C. elegans lines that co-express C99 and PSEN1 in neurons, allowing Aβ production through γ-secretase in membranes, as it occurs naturally. Transgenes were designed to express wild-type (WT) and FAD-mutant forms of C99 (I45F) and human PSEN1 (L166P) under control of pan-neuronal promoter rgef-1.
Results
By day 4 of adulthood, FAD-mutant animals (C99 I45F/WT PSEN1 and WT C99/L166P PSEN1) had substantially fewer synaptic puncta compared to WT/WT double transgenic animals, which in turn were identical to non-transgenic control animals. This correlated with reduced lifespans in the FAD-mutant animals. Importantly, monogenic lines expressing only C99 I45F showed no premature synaptic loss and a normal life span, indicating a requirement of the WT human PSEN1 transgene for the neurodegenerative phenotype. Remarkably, while addition of designed mutation V44F into C99 I45F blocks carboxypeptidase trimming of Aβ45 to Aβ42 by γ-secretase, C99 V44F-I45F/WT PSEN1 animals displayed a more aggressive phenotype.
Conclusions
FAD mutations lead to age-dependent synaptic loss and reduce lifespan in the new C. elegans lines, and these effects do not require Aβ42 production. This system should provide a useful new tractable FAD animal model for the study of pathogenic mechanisms and in vivo drug screening.