Amyotrophic lateral sclerosis is an adult onset motoneuron degenerative disease with a lifetime risk of ~1/1000 that affects an estimated 30, 000 adults in the US at any one time with ~5000 new cases/year. Approximately 80% of the cases are fatal 5 yrs after diagnosis. There is no cure and only one FDA approved therapy that has a minor effect on the progression of the disease. Identifying drug targets for ALS will advance both our understanding of this disease and will reveal relevant targets for drug development. The most well characterized genetic form of ALS is caused by mutations in the SOD1 gene. Because SOD1 based ALS and sporadic ALS both cause the same disease, it is believed that drug targets will be shared. Mutations in SOD1 produce a dominant gain of function protein with unknown activity. Since SOD1 mutants do not cause ALS-like phenotypes in invertebrates, only rodent models of this disease exist thus limiting the type of experiments that can be performed. For example it is not possible to do genetic modifier screens, which are an excellent way to identify protein targets for drug intervention, in ALS mice. In addition, drug screens in mice are very expensive and require large numbers of animals. To generate another vertebrate model of ALS that can be used for genetic and drug screens, we generated transgenic zebrafish over expressing the well-characterized SODG93A and G85R mutations. When we generated the transgenic zebrafish, we incorporated a heat shock promoter (hsp70) driving the fluorescent protein, DsRed, to track our transgene. Upon identifying the transgenic lines, we found that the fish carrying the sod1 mutations turned on the heat shock response, as revealed by DsRed expression, independent of heat shock (referred to as sodmut hsp70 induction). This suggests that fish containing mutant Sod1 exhibit cellular stress starting at early larval stages. We propose to use this response as a read-out of mutant Sod1 gain-of-function toxicity. In this proposal we present preliminary data linking the sodmut hsp70 induction to ALS phenotypes. We then present Aims to develop and validate this read-out as an assay for screening. Lastly, we will use this in vivo assay to perform a pilot genetic modifier screen to identify novel targets for intervention. Development and validation of this unique in vivo, vertebrate assay of Sod1 mutant toxicity will allow future development of high-throughput screens and rational drug design for ALS.
Amyotrophic lateral sclerosis (ALS) is a fatal, neurodegenerative disease that has no cure. We have generated a zebrafish model of SOD1 ALS and find that it has a very early, easily scored, phenotype. In this proposal we will develop this phenotype into an assay for drug target identification and drug testing. This is a unique approach as it is a rapid, in vivo screen in a vertebrate and will serve as a basis for both genetic and drug screens to identify therapeutics for ALS.
