MOLECULAR AND GENETIC CHARACTERIZATION OF EMS-INDUCED LETHAL MUTATIONS IN DROSOPHILA ENRICHED FOR ORTHOLOGS OF HUMAN DISEASE-CAUSING GENES - PROJECT SUMMARY/ABSRACT Forward genetic screens through chemical mutagenesis in Drosophila have made significant contributions to fundamental discoveries that span multiple biological disciplines and provided novel biological insights that are directly relevant to diverse human diseases. However, due to the difficulty to map causative mutations and its labor-intensiveness, many researchers cannot take advantage of this approach. A collection of fly strains that are obtained from a well-designed chemical mutagenesis screen that simultaneously explores numerous phenotypes can serve as excellent resource for the broader research community since a number of secondary screens could be conducted on the same collection and individual mutant lines can be used to probe diverse biological processes that are evolutionarily conserved. However, such resource does not exist in the Drosophila community and most fly strains isolated from previously conducted chemical mutagenesis screens were left unmapped and subsequently discarded. We performed a large scale F3 clonal EMS-mutagenesis screen on the Drosophila X-chromosome and have been maintaining 1,385 recessive lethal mutant strains. So far, we have molecularly mapped the lethality-causing mutations of 614 lines to 165 genes. This collection was built on a healthy isogenic y w FRT19A X-chromosome using low concentration of EMS and have been selected for mutants that show interesting morphological and/or neurophysiological phenotypes in mosaic animals. Importantly, the careful design of the screen allowed us to enrich for essential genes that are evolutionarily conserved (~90% of mapped genes are conserved in human) and have direct relevance to human diseases (~70% of mapped genes have human homologs that cause genetic diseases in human). Mapped mutations from this collection have been used in >80 manuscripts by many laboratories that study a variety of biological contexts and have also led to discovery of novel human disease genes and mechanisms. Here, we will sequence and attempt to demonstrate the causality of the remaining 771 unmapped lines that have been maintained using a new streamlined sequencing and bioinformatic analysis pipeline followed by rigorous genetic analysis. Upon completion, this project will provide Drosophila researchers with a collection of >1,000 fly strains which are carefully phenotyped that have been generated on a well-defined genetic background and mapped to >300 conserved genes. This resource can be used to perform numerous secondary screens and subsequent deep investigations by numerous laboratories in the US and around the world. Missense mutations identified from this effort can further provide novel structure-function information on conserved proteins. The rich phenotypic information of clonal phenotypes will allow us to establish a comprehensive database that could be mined by Drosophila biologists as well as experts in other disciplines such as clinical geneticists interested in novel disease gene discovery in humans.
