Thus, the loss of fertility in these flies is usually caused by the disruption of a gene by the P element at the insertion site rather than by the increased dosage of expression, whereas the entire Yb protein is needed for expression and SSC maintenance The Yb protein contains a 166-aa region (residues 396C562) homologous to the DEAD/DEAH box RNA helicases and a 127-aa Tudor-like domain name (residues 817C944; Fig. cells (for reviews observe Lin, 2002; Lovastatin (Mevacor) Morrison and Spradling, 2008). The concept of a stem cell niche was first proposed for the human hematopoietic system (Trentin, 1970). A major challenge in stem cell biology is usually to define the properties of niche cells and mechanisms through which they regulate the behavior of stem cells. The organization of niche cells and their essential function in regulating stem cell self-renewal were first defined in the ovary Rftn2 (Lin and Spradling, 1993, 1997; Cox et al., 1998; Xie and Spradling, 1998, 2000; King and Lin, 1999). The ovary and testis are essentially tubular structures, with the apical end consisting of somatic niche cells that are in contact with germline stem cells (GSCs; Lin, 2004; for review observe Lin, 2002). Each ovary consists of 16C18 tubular structures called ovarioles. In each ovariole, 8C10 terminal filament (TF) cells form a stack at the very anterior end (Fig. 1, ACD). Adjacent to them are five to six cap cells that cover the anterior side of two to three GSCs. Oogenesis is initiated when a GSC divides asymmetrically to produce a child GSC and a differentiating child cell termed the cystoblast. The cystoblast then undergoes four rounds of synchronous divisions with incomplete cytokinesis to produce a germline cyst that Lovastatin (Mevacor) contains 16 cells interconnected by cytoplasmic bridges called ring canals (for evaluate observe Deng and Lin, 2001). As a Lovastatin (Mevacor) 16-cell cyst techniques to the middle region of the germarium, two to three somatic stem cells (SSCs) at the periphery of this region divide to produce a Lovastatin (Mevacor) monolayer of follicle cells that encapsulate the cyst to form an egg chamber (Margolis and Spradling, 1995). The egg chamber then buds off of the germarium and continues to grow and mature. In the testis, the 10C12 anterior somatic niche cells form a group called the hub (Fig. 1 H). The hub is usually surrounded and contacted by six to nine GSCs, each of which is usually flanked by a pair of SSCs (Jones et al., 2004). A GSC and its two flanking SSCs undergo asymmetrical division in synchrony. After each division, the child GSC and SSCs remain in contact with the hub, whereas their sibling cells differentiate into a gonialblast and two somatic cyst cells, respectively. The gonialblast, sandwiched by the two somatic cyst cells, enters four rounds of mitotic divisions to form a 16-cell germline cyst. Subsequent meiotic divisions result in 64 interconnected spermatids. Open in a separate window Physique 1. Yb is usually localized in discrete spots (Yb body) in somatic cells of ovaries and testes. (ACI) Immunofluorescence images of Yb in wild-type and transgenic ovaries (A and CCG) and wild-type testes (H and I), with a null mutant ovary (B) shown as a negative control. A and B show a wild-type and a germarium, respectively, double stained with a Yb (green) antibody to detect Yb and an adducin antibody (reddish colored) to visualize spectrosomes (SP) and fusomes (germline-specific organelles) also to format somatic cells such as for example escort cells (EC). The inset inside a magnifies cover cells (CC) with this panel. D and C display germaria from flies including or missing a transgene, respectively, dual stained for Flag antibody (reddish colored) as well as the DNA dye DAPI (green). E displays a transgenic germarium dual stained for Flag (reddish colored) and Yb (green). F displays section of an egg chamber dual stained for Yb (green) and adducing (reddish colored), with concentrate on the follicle cell (FC) surface area. G displays a cross-sectioned picture of an ovariole dual stained for Yb (green) and adducing (reddish colored). H displays the apical end of the wild-type testis dual stained for Yb (green) and adducing (reddish colored). Yb physiques are enriched in the hub cells and so are within somatic cyst cells Lovastatin (Mevacor) (SC) however, not in germline.