Peroxisomal biogenesis disorders (PBDs) are a group of autosomal recessive neurodegenerative disorders caused by mutations in PEX genes. Our goal is to evaluate the efficacy of a set of newly developed drugs capable of selectively promoting the read-through of premature stop codons (nonsense suppressor compounds) in PEX genes as therapeutic agents for a subset of individuals with PBDs. One such nonsense suppressor drug, PTC-124 is in clinical trials for the treatment of cystic fibrosis and Duchenne's muscular dystrophy cases caused by nonsense mutations in CFTR and DMD, respectively. Another series of analogs based on the parent compound indoprofen have shown nonsense suppressor activity in cell culture assays and have favorable toxicity and bioavailability profiles in rodents. A necessary step in achieving this goal is to determine the ability of these drugs to rescue peroxisome structure and function in cultured cells derived from PBD patients with nonsense mutations in peroxisome assembly (PEX) genes. In this proposal, we will conduct mutational analyses of PEX genes in thirty PBD patients to expand upon a known subset of PBD patients with disease-causing nonsense mutations (Specific Aim 1). Fibroblasts exist from each of these patients which will be used in downstream analyses of peroxisome function. In parallel, we will conduct a series of functional assays on drug-treated cultured fibroblasts derived from eighteen PBD patients with previously identified nonsense mutations in peroxin genes (Specific Aim 2). This includes biochemical, immunolocalization, immunoblot, and reporter gene-based characterization of peroxisome protein function and assembly. Should any of these nonsense suppressor compounds prove effective in rescuing peroxisome function in cultured fibroblasts, we will analyze their off-target effects through microarray-based gene expression profiling of drug-treated cells. Overall, these studies will provide a necessary initial evaluation of the potential efficacy of nonsense mutation suppressor therapies for PBDs prior to our long-term goal of developing therapeutic agents for PBDs that are used in clinical settings.
Project Narrative We are interested in developing therapies for patients with peroxisome biogenesis disorders (PBD), which are a group of inherited, often fatal, neurological diseases in which there is no current therapy. We will evaluate a series of drugs for their ability to rescue peroxisome functions in skin cells cultured from patients. These drugs have been shown to read through nonsense mutations in two other diseases, and preliminary chemical refinement and animal toxicity studies are in progress. Cellular rescue is a necessary preliminary step for the potential future application of these drugs to treat PBD caused by nonsense mutations.
| Levesque, Sebastien; Morin, Charles; Guay, Simon-Pierre et al. (2012) A founder mutation in the PEX6 gene is responsible for increased incidence of Zellweger syndrome in a French Canadian population. BMC Med Genet 13:72 |
| Dranchak, Patricia K; Di Pietro, Erminia; Snowden, Ann et al. (2011) Nonsense suppressor therapies rescue peroxisome lipid metabolism and assembly in cells from patients with specific PEX gene mutations. J Cell Biochem 112:1250-8 |
