Genetically accurate models of SOD1-based ALS in drosophila: Validation and characterization

SOD1 has been a unique target of ALS research as the first identified gene of the disease; since 20 years, SOD1 has not been related to any other disease unlike other ALS-causing genes. There are more than 160 mutations seen in ALS patients scattered all around the small protein that cause the mutant protein to gain a toxic function. Up to date, more than 20 SOD1-based animal models have been developed that helped us gain insights to the mechanisms in which mutant SOD1 is involved, e.g. oxidative stress, misfolded protein aggregation, endoplasmic reticulum stress and glutamate excitotoxicity. Even so, all these models had their own drawbacks as being either knock-out or over-expression studies. In this respect we aimed to develop an accurate model of SOD1-based ALS using ends-out homologous recombination (HR) in Drosophila. In this study, four previously defined SOD1 missense mutations (G37R, H48R, H71Y and G85R) were introduced into the endogenous locus of Drosophila SOD1 (dSOD). For the characterization of mutants, life span and larval motility assays were used. In addition, genotypic ratios of the mutants were observed for genotype-phenotype correlations and expression levels of several candidate genes, possibly involved in ALS pathogenesis, were compared among mutants using quantitative RT-PCR. This is the first study, which successfully implements homologous recombination, a new and powerful approach to ALS. We hope that, genetically accurate models of SOD1-based ALS, generated via homologous recombination, will further help us gain insights into the complex mechanisms involved in neurodegenerative processes.