RUI: Analyzing the interactions and functional conservation of orphan genes required for mature sperm function in Drosophila

College Of The Holy Cross, Worcester MA

Investigators

Abstract

In many insects, fertilization requires thin, needle-shaped sperm to locate and enter a narrow channel on the surface of an egg. Understanding the molecular interactions required for insect fertilization could enable scientists to manipulate the reproduction of species of agricultural or biomedical relevance. To date, however, little is known about how insect sperm take on their needle-like shape and recognize eggs to facilitate entry. This project uses the tractable fruit fly model system to investigate these questions. One objective will investigate sperm composition and function in flies lacking a gene required for efficient sperm entry into eggs. Another objective will evaluate the extent to which this gene, and two others required for sperm head shaping, share conserved functions across different fly species. This project will expand the research capacity of an exclusively undergraduate institution, preparing more students to join the nation’s scientific workforce. The principal investigator’s lab will provide immersive, paid summer research opportunities for students and participate in a mentoring program that allows new college students to immediately join research labs. In parallel, students in an intermediate-level Genetics lab course will conduct original research to identify an additional gene required for fly sperm to enter eggs. This project will investigate how lineage-specific “orphan” genes contribute to the maturation and function of sperm in male Drosophila melanogaster and evaluate the extent to which these genes’ functions are conserved in divergent fly species. First, orthologs of these genes will be tested for their ability to function in D. melanogaster, allowing changes in protein sequence and structure to be correlated with functionality and subcellular localization. Second, CRISPR-mediated genome editing, fertility assays and cytological analyses of spermatogenesis will be used to test these genes’ functions in two divergent fly species, Drosophila ananassae and Drosophila virilis, allowing direct assessment of their functional conservation. Third, targeted genetic analyses and quantitative proteomics will be used to identify defects in sperm produced by males that lack the gene required for sperm entry into eggs, which holds promise to identify potentially more conserved proteins that act at fertilization. This project will advance knowledge of the functions and evolution of lineage-specific genes while providing much-needed molecular genetic detail about sperm-egg interactions, a process about which surprisingly little is known in Drosophila. This project was co-funded by the Evolutionary Processes Program in the Division of Environmental Biology and the Developmental Systems Program in the Division of Integrative Organismal Systems This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.