Amyotrophic lateral sclerosis (ALS) is an aggressive neurodegenerative disease of motor neurons that results in progressive muscle weakness, paralysis, and ultimately death, usually within five years of disease onset. Late stage ALS patients require extensive supportive care, placing immense emotional and economic burdens on patients and their families. Riluzole, the only drug currently approved for the treatment of ALS, provides only a modest extension of 2 to 3 months in life expectancy for ALS patients, and hepatotoxicity is a significant side effect limiting the drug's use. Biochemical and cellular studies have suggested a wide variety of potential targets for riluzole action, but the precise molecular mechanism of action (MO A) of this drug remains poorly defined. A more complete understanding of riluzole's molecular target(s) would be of great value in guiding the discovery of safer and more effective therapies for ALS. Genetic studies in the model nematode Caenorhabditis elegans have been successfully utilized to identify the targets and mechanistic pathways of a number of human Pharmaceuticals. Preliminary studies have demonstrated a significant effect of riluzole on C. elegans, and multiple independent genetic mutants resistant to the drug have been isolated. This Phase I SBIR project will complete the genetic analysis of these riluzole-resistance alleles in C. elegans, with the goal of characterizing riluzole's MOA and identifying riluzole targets that can be exploited for therapeutic discovery efforts.
Two specific aims will be pursued: (1) Genetic mapping of the riluzole-resistance alleles will employ a combination of genetic recombination mapping and single-nucleotide polymorphism analysis. (2) Identification of the riluzole-resistance gene(s). Based on the genetic mapping results, a combination of candidate gene sequencing and, as needed, genetic transformation experiments will be used to identify the specific mutations conferring riluzole resistance. The molecular characterization of the riluzole-resistance gene(s) will identify one or more pathways for riluzole's action in a living model animal with a well-characterized nervous system. Subsequent Phase II efforts will (a) identify and evaluate the function of homologous mammalian genes, and (b) develop and implement new bioassays for the rational discovery of next-generation therapeutics for ALS and other neurodegenerative diseases. ? ? ?