Developmental Analysis of Fertilization Pathways in Drosophila

University Of Washington, Seattle WA

Investigators

Abstract

Studies of fertilization have a long and rich history in the field of developmental biology. Their importance from historical and scientific perspectives lies in the desire to understand mechanisms that ensure the successful interaction between the sperm and egg and the initiation of embryogenesis. The vast majority of studies of fertilization use selected marine invertebrate or mammalians species as model organisms. The proposed studies exploit genetic and molecular tools available for the insect Drosophila melanogaster to discover new cellular and molecular components required for sperm activation. Primary tools for this investigation Drosophila strains that are male sterile due to defects in sperm activation. The mutants define a genetic pathway of five genes whose functions are required after sperm entry into the egg but prior to sperm nuclear decondensation and aster formation. The protein products of two genes, called sneaky (snky) and misfire (mfr), will be studied to understand their function in the dynamic changes that occur in the sperm plasma membrane, nucleus and acrosome. Both the Snky and Mfr proteins are predicted transmembrane proteins. Their localization in normal and mutant genetic backgrounds will be studied using antibody and protein fusion probes. Functional domains will be identified through directed mutagenesis and protein interaction studies. Effects on localization of other membrane proteins will be monitored to gain a better understanding of the overall distribution of proteins in the highly polarized sperm. This project also includes studies to identify the products of three other genes in the snky-class that have proposed roles in acrosome biogenesis and function. (1) The intellectual merit of the proposed studies lies in its goal to understand the molecular mechanisms of fertilization. Previous work in this lab led to discovery of a large number of genes required for male fertility. This project focuses on a small subset required in a narrow window of time for the sperm to respond to the egg cytoplasm and undergo the changes essential to complete fertilization. The results obtained will be compared with the lessons learned from studies of extensively studied organisms such as marine invertebrates and mammals. This comparison should be informative since molecular studies indicate that the Snky and Mfr proteins are found in many animal species. As interesting, will be the discovery of species-specific molecular mechanisms that may provide insight into the diversity of reproductive strategies used by different organisms. (2) The broader impacts include its training value for young scientists. Portions of this project will constitute the dissertation research of two graduate students. In addition, this project relies heavily on the contributions of undergraduates. At least four undergraduates will gain their first experiences in research by participation in this work; the majority of which will be intentionally selected to enhance the diversity of students engaged in research at the University of Washington. Beginning students apply principles learned in their university coursework to genetic, molecular and cytological investigations of newly discovered mutations and contribute to an original scientific project. In addition, this work will generate valuable tools that can be used for the larger community of scientists who study Drosophila spermatogenesis and fertilization.