Animals, including humans, contain a small number of cells in their gonads called germline stem cells (GSCs). These cells are essential for making sperm or eggs throughout the lifetime of the animal. The decision for a dividing stem cell to renew as a stem cell or to differentiate—as well as the regulation of these early divisions—are some of the most critical decisions in development. It’s significant, then, that some of the key genes that regulate GSC maintenance and differentiation in two related species of fruit fly are rapidly evolving. Researchers don’t know what’s causing the changes or what the functional consequences will be.

Charles F. Aquadro, Molecular Biology and Genetics, is working to provide a framework with which to test the functional consequences and evolutionary forces driving the changes in these important genes. This work will contribute to understanding the genes and mechanisms that control stem cell fate decisions in drosophila as well as other organisms, including humans. Aquadro and his team are focusing on the key switch gene for GSC differentiation, called bag of marbles (bam). Bam has accumulated a dramatic excess of amino-acid changes between the two closely related fruit fly species, D. melanogaster and D. simulans. Aquadro is investigating the possible causes, including interactions with the bacteria Wolbachia. The evolution of these genes provides an opportunity to understand how GSCs are regulated during normal development and how their misregulation due to mutation or parasites can lead to infertility, germline cancers, and reproductive isolation. NIH Award Number: 2R01GM095793-05