RAN Translation as a Therapeutic in ALS
Abstract
The discovery of genetic causes for amyotrophic lateral sclerosis (ALS) and frontotemporal dimentia (FTD) has invigorated the search for novel therapies for these diseases. The most common genetic cause of these diseases are mutations in the C9orf72 gene, in which a 6 nucleotide repeat sequence (GGGGCC) that normally occurs in 5-10 repeat copies in the gene is expanded to hundreds to thousands of repeats in affected individuals. Although these repeats are located in an intron, recent data have shown that transcribed RNAs containing the mutant repeats are translated, leading to repeating polypeptides that are prone to aggregation and toxic to neurons. The central hypothesis of this proposal is that inhibition of repeat associated translation (repeat associated, non-ATG [RAN] translation) would be a successful therapeutic approach to ALS. Before we can inhibit RAN translation therapeutically, we will first need to figure out how it works. In the first part of our proposed research, we will define the mechanism by which this unusual translation occurs. Since the repeat expansions do not have normal start codons, the major question is how can such translation get started? Our hypothesis is that the RNA structures formed by the guanosine-rich repeats can act to guide ribosomal components to assemble on the RNA and begin translation. To define the mechanism, we will apply biochemical, structural, and dynamic approaches developed over the past decades. These experiments will determine the RNA folds formed by disease-causing RNAs and how these structures can be translated by ribosomes. Using single-molecule methods, we can watch ribosomes translating directly in real time, allowing us to observe translation with unprecedented clarity. By defining the mechanism, we will we better understand how to target this process specifically for therapy. In the second part of our proposed research, we will harness the mechanistic knowledge around RAN translation and design high-throughput screens to identify small molecule inhibitors or modulators of the process. We will confirm all potential small molecule inhibitors using both in vitro and in vivo systems. Our Therapeutic Idea Award proposal is ambitious but with potentially high clinical impact for patients with genetic basis for ALS. Our combined mechanistic and screening approach will identify potential lead compounds, which will require further medicinal chemistry optimization, preclinical, and clinical investigation that are outside the scope of the current award (timeline to clinical impact likely 5-8 years, based on normal pharmaceutical development). The results of this study will also provide a deeper mechanistic knowledge of how repeat expansions lead to disease in ALS, which is a broad foundation for future therapies.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 31, 2017
- Source ID
- W81XWH1610095
Entities
People
- Joseph Puglisi
Organizations
- Stanford University
- United States Army