948B Poster - 15. Models of human disease
Friday April 08, 2:00 PM - 4:00 PM

Authors:
Ruby Guevara; Kenneth Owyang; Jennifer Tan; Marissa Joe; Taylor Jones; Duyen Nguyen; Emmanuella Tetteh; Shannon Twardy; Celine Neudorf; Shelly Huynh; Jeremy Lee

Affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, CA

Keywords:
a. neural degeneration; i. lifespan

The hallmark of Alzheimer’s disease (AD) is the presence of amyloid plaques in affected areas of the brain, which are aggregates of the amyloid-beta (Aβ) peptide. Aβ, especially Aβ₄₂, is known to be neurotoxic and crucial in AD pathology. While the function of Aβ is not well understood, recent studies have shown it to have antimicrobial effects (Kumar et al., 2016). It has also been shown to interact with the human antimicrobial peptide LL-37 in binding assays in vitro (De Lorenzi, et al., 2017). If LL-37 and Aβ interact in vivo, it may affect the neurotoxicity of Aβ.
In order to determine whether LL-37 affects Aβ neurotoxicity, we generated four transgenic flies pan-neuronally expressing human Aβ₄₂ and/or LL-37: LL37-expressing, Aβ₄₂-expressing, Aβ₄₂/LL-37 co-expressing, and non-expressing controls. Longevity assays and RING climbing assays were conducted to determine whether LL-37 has an effect on Aβ₄₂’s neurotoxicity in vivo. The results showed that co-expression of LL-37 and Aβ₄₂ led to longer lifespans than expression of only Aβ₄₂, but shorter lifespans than non-expressing controls. In developmental assays, these co-expressing flies had higher survivorship to eclosion than Aβ₄₂-expressing flies. In addition, RING assays showed that dual-expressing flies had a significant improvement in locomotive functions compared to LL37-expressing and Aβ₄₂-expressing flies. These results indicate that LL-37 might attenuate the deleterious effects of Aβ₄₂ in Alzheimer’s disease.
We are assessing LL-37 and Aβ₄₂ expression levels in our transgenic flies by qRT-PCR and Western blot to determine whether co-expression of LL-37 has an effect on Aβ₄₂ transcript or protein levels. We also intend to assess whether the expression of LL-37 modulates Aβ’s known effects on the expression of a variety of genes involved in synaptic plasticity and neuronal function. To do this, we are performing RNA sequencing analysis to obtain a quantitative snapshot of RNA transcripts present within our four genotypes. Using a baseline comparison of Aβ₄₂-expressing flies versus wild type, we will focus on key genes of interest previously shown to be affected by Aβ₄₂. This will allow us to compare any modulating effect LL-37 has on Aβ₄₂’s effects on gene expression, by assessing co-expressing flies and noting any key differences in their RNA expression profiles. This will help provide insight into the mechanism by which LL-37 attenuates Aβ’s neurotoxic effects.