Every organism begins as a single cell. Many organisms ultimately consist of many cells organized into complex systems of tissues and organs that perform an array of functions necessary for its survival. But how does a single cell give rise to trillions of cells specified for explicit functions? The answer to this question is stem cells. In the developing organism, the cells that ultimately compose organs develop from unspecialized stem cells able to both differentiate into functional cell types and reproduce themselves. These stem cells divide asymmetrically to provide the cells necessary for organogenesis while maintaining the stem cell population that replaces dying and damaged cells continuously throughout the organism’s life. Despite their fundamental importance to living systems and tremendous regenerative capacity, we still know very little about the processes by which these stem cell populations are initially formed and regulated. My project this summer will attempt to elucidate the mechanisms by which stem cells are established and maintained during the process of organogenesis.
Specifically, I will examine the role of Bone Morphogenic Protein (BMP) signaling in stem cell establishment and maintenance in the developing testis of the common fruit fly, Drosophila melanogaster. The Drosophila testis contains two stem cell populations: the germline stem cells (GSCs), which divide to produce sperm, and the cyst progenitor stem cells (CySCs) that divide to produce the cyst cells that surround the spermatogonia and promote their differentiation. In the adult organism, the neighboring CySCs promote GSC maintenance through BMP signaling. However, because stem cell development is still poorly understood, the role of BMP signaling in the developing testis remains unknown. In previous research, I have characterized the expression of a downstream target of BMP signaling, SMAD, throughout development. This summer, I will assess whether BMP signaling is responsible for GSC maintenance during development as it is in the adult and determine if BMP signaling plays a role during the process of GSC establishment. By probing the role of BMP signaling in stem cell establishment and maintenance, we have a more complete understanding of the mechanisms used to regulate organogenesis in live organisms. This information can be utilized to better understand organ systems and to develop more effective therapies for those suffering from defects in these crucial systems.