An adult stem cell is an undifferentiated cell, found among differentiated cells in a tissue or organ. The specific microenvironment of each tissue that adult stem cells reside in is called the stem cell niche. In a living organism, adult stem cells maintain and repair the tissue in which they reside. In the Drosophila testis niche, there are two different stem cell populations including the germline stem cells (GSCs) and the cyst stem cells (CySCs). These stem cells cluster around the hub, a group of non-dividing cells that constitute the niche. Previous research has indicated that proper communication between and within the hub cells, CySCs, and GSCs is important in maintaining stem cell self-renewal, and allowing proper cellular differentiation to achieve tissue homeostasis. We are investigating the function of a receptor tyrosine kinase (RTK) called PVR (PDGF-VEGF-related receptor) in this niche. We found that the ligand Pvf1 is secreted from hub cells, and its receptor PVR is expressed in both the hub and the cyst stem cells. We hypothesize that PVR signaling may be one mechanism by which the hub maintains expression of proper self-renewal signals during spermatogenesis. In this study we inhibited PVR in the hub cells by hub-restricted expression of either a PVR RNA interference (RNAi) transgene, or a dominant negative transgene. By comparing the experimental group with the control group, we found defects in the germline. Some testes had GSC-like individual germ cells distant from the hub where differentiation is expected. Other testes had transit-amplifying spermatogonia next to the hub. We also noticed that there was a reduction in the number of cyst stem cells surrounding the hub. Our conclusion is that inhibition of PVR in the hub leads to the improper maintenance of both stem cell populations in the testis, thus disrupting the regulation of spermatogenesis.