View Program - 63rd Annual Drosophila Research Conference

Adult stem cells reside in dynamic, supportive microenvironments termed niches, which are generated by specialized niche cells. Niches are often complex and composed of functionally cooperative subpopulations of cells rather than uniform populations, and gaining insight into niche composition underpins our understanding of tissue homeostasis. Therefore, our ultimate goal is to further our understanding of stem cell niches by investigating their cellular composition and gene expression programs, using the Drosophila testis stem cell niche as a model. This niche contains three cell populations: post-mitotic somatic hub cells (or niche cells), which are surrounded by two types of stem cells, germline stem cells (GSCs) that differentiate into sperm and cyst stem cells (CySCs) that give rise to somatic support cells. Previous in situ hybridization (ISH) and immunostaining experiments have suggested that hub cells may not uniformly express the same transcriptional program, raising the possibility that they are a heterogeneous population of cells. Intriguingly, hub cells descend from somatic gonadal precursors (SGPs), which arise from three distinct parasegments (PS) in embryogenesis, suggesting that developmental origin could underly previously observed heterogeneity. Here we use the HACK and Split-Gal4 ternary systems to genetically control individual populations of SGPs. Preliminary results suggest that combinatorial patterns of homeobox gene expression allow genetic dissection of SGPs arising from differing PS. These tools will allow lineage tracing and manipulation of the distinct populations of SGPs according to their origin to begin to determine if hub cell origin correlates with function, localization within the niche, and transcriptional program.

Assessment of cellular and functional heterogeneity within the Drosophila testis stem cell niche

**Assessment of cellular and functional heterogeneity within the Drosophila testis stem cell niche**