Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal dementia (FTD) are common neurodegenerative disorders that are progressive, fatal, and without effective treatment. Recently, the most common known cause of ALS and FTD was identified as an intronic GGGGCC hexanucleotide repeat expansion in the gene C9orf72 (C9FTD/ALS). This repeat triggers synthesis of toxic proteins via a process known as Repeat Associated Non-AUG (RAN) Translation. These RAN peptides kill neurons and are sufficient to cause neurodegeneration in model systems. We know very little about how RAN translation at C9 repeats (C9 RANT) actually occurs. The objective of this proposal is to determine the mechanisms underlying C9 RAN and to identify methods of blocking it as a first step towards novel therapeutic development. Our central hypothesis is that C9 RAN utilizes a non-canonical translational initiation pathway that can be selectively blocked. Moreover, we predict that preventing C9 RAN will stop neurodegeneration elicited by GGGGCC repeats. To test these hypotheses, we developed robust and quantitative in vitro and cell based assays of C9 RANT, as well as a collection of models derived from patient induced pluripotent stem cells, rodent neurons, and Drosophila. Using these tools, we will define the mRNA species that undergo C9 RANT, identify the critical RNA and protein based factors that allow for C9 RANT and test whether suppressing C9 RANT by modulating the surrounding sequence or protein factors can block toxicity in model systems. Together, these studies should provide us with a working map of how C9 RAN occurs and what steps can be taken to prevent it. This project has broad reaching implications both for our understanding of how RAN translation contributes to disease as well as providing a logical path towards therapeutic development in C9FTD/ALS and other neurodegenerative nucleotide repeat disorders.

Public Health Relevance

ALS and Frontotemporal Dementia are neurodegenerative disorders that lead to significant death and disability. Recently, a novel repeat mutation was identified as the most common cause of ALS and Frontotemporal Dementia. This repeat causes ALS at least in part by producing toxic proteins through an unusual process known as RAN translation. This proposal will use biochemical techniques, neurons and patient derived induced pluripotent stem cell models of to understand how RAN translation occurs and how it can be selectively blocked in ALS patients. These approaches will lay the groundwork for developing small molecule therapeutics for this currently untreatable disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS099280-05
Application #
9920791
Study Section
Cellular and Molecular Biology of Neurodegeneration Study Section (CMND)
Program Officer
Gubitz, Amelie
Project Start
2016-09-01
Project End
2021-05-31
Budget Start
2020-06-01
Budget End
2021-05-31
Support Year
5
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Neurology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Green, Katelyn M; Glineburg, M Rebecca; Kearse, Michael G et al. (2017) RAN translation at C9orf72-associated repeat expansions is selectively enhanced by the integrated stress response. Nat Commun 8:2005
Green, Katelyn M; Linsalata, Alexander E; Todd, Peter K (2016) RAN translation-What makes it run? Brain Res 1647:30-42
Yang, Wang-Yong; He, Fang; Strack, Rita L et al. (2016) Small Molecule Recognition and Tools to Study Modulation of r(CGG)(exp) in Fragile X-Associated Tremor Ataxia Syndrome. ACS Chem Biol 11:2456-65
Flores, Brittany N; Dulchavsky, Mark E; Krans, Amy et al. (2016) Distinct C9orf72-Associated Dipeptide Repeat Structures Correlate with Neuronal Toxicity. PLoS One 11:e0165084
He, Fang; Jones, Julie M; Figueroa-Romero, Claudia et al. (2016) Screening for novel hexanucleotide repeat expansions at ALS- and FTD-associated loci. Neurol Genet 2:e71