Frontotemporal dementia (FTD) is the second most common presenile dementia after Alzheimer’s disease and
shares many pathological and genetic overlaps with ALS. The most common genetic cause of FTD and ALS is
a GGGGCC hexanucleotide repeat expansion in the first intron of the C9ORF72 gene. Although RNA toxicity
and C9ORF72 haploinsufficiency may also contribute to disease pathogenesis in C9ORF72-related FTD/ALS,
much efforts has focused on investigating the toxicity of dipeptide repeat (DPR) proteins that can be translated
from both sense and antisense repeat RNAs. How these DPR proteins, especially poly(GR), cause
neurodegeneration at the molecular mechanistic level remains largely unknown. In this exploratory R21 grant
application, based on our recent findings that several antimicrobial peptide genes, such as metchnikowin (Mtk),
are upregulated with poly(GR) toxicity in Drosophila and that Mtk knockdown in the eye or in all neurons
suppresses poly(GR) neurotoxicity, we propose to further investigate this understudied pathway in
neurodegeneration. In particular, we will investigate the molecular mechanisms underlying the effects of Mtk on
poly(GR) toxicity, explore the non-cell autonomous neurodegenerative activity of Mtk, and finally attempt to
identify mammalian AMP(s) that may function in a similar fashion as Drosophila Mtk in the molecular
pathogenesis of FTD/ALS. These studiers will shed new light on pathogenic mechanisms of FTD/ALS and may
help identify novel therapeutic targets for these disorders.