The Erika Matunis Laboratory studies the stem cells that sustain spermatogenesis in the fruit fly Drosophila melanogaster to understand how signals from neighboring cells control stem cell renewal or differentiation. In the fruit fly testes, germ line stem cells attach to a cluster of non-dividing somatic cells called the hub. When a germ line stem cell divides, its daughter is pushed away from the hub and differentiates into a gonialblast. The germ line stem cells receive a signal from the hub that allows it to remain a stem cell, while the daughter displaced away from the hub loses the signal and differentiates. We have found key regulatory signals involved in this process. We use genetic and genomic approaches to identify more genes that define the germ line stem cells' fate. We are also investigating how spermatogonia reverse differentiation to become germ line stem cells again.