Abstract
Emerging evidence supports that stem cells are regulated by both intrinsic and extrinsic mechanisms. However, factors that determine the fate of stem cells remain incompletely understood. The Drosophila testis provides an exclusive powerful model in searching for potential important regulatory factors and their underlying mechanisms for controlling the fate of germline stem cells (GSCs). In this study, we have found that Drosophila gilgamesh (gish), which encodes a homologue of human CK1-γ (casein kinase 1-gamma), is required intrinsically for GSC maintenance. Our genetic analyses indicate gish is not required for Dpp/Gbb signaling silencing of bam and is dispensable for Dpp/Gbb signaling-dependent Dad expression. Finally, we show that overexpression of gish fail to dramatically increase the number of GSCs. These findings demonstrate that gish controls the fate of GSCs in Drosophila testis by a novel Dpp/Gbb signaling-independent pathway.
Highlights
Adult stem cells (ASCs) are essential for tissue homeostasis by constantly providing new cells to replenish many tissues, including blood, skin, germ-line, and the intestinal epithelium
To identify novel genes that regulate the self-renewal or differentiation of germline stem cells (GSCs) in Drosophila testis, we conducted a screen for male sterile mutants with P-element insertion, available from the Bloomington Stock Center
Under the same experimental conditions, the initial marked gish04895 and gishMI08417 mutant GSCs clones were 66.6% (n = 213) and 66.4% (n = 188) respectively at day 2 after heat-shock treatments (AHST), whereas they reduced to the rates of 21.2% (n = 189) and 24.4% (n = 279) respectively at day 20 AHST (Fig. 2d–f and k). These results revealed that 68.2% and 63.3% of marked gish04895 and gishMI08417 mutant GSCs clones were lost during the 20-day AHST
Summary
Adult stem cells (ASCs) are essential for tissue homeostasis by constantly providing new cells to replenish many tissues, including blood, skin, germ-line, and the intestinal epithelium. In adult Drosophila males, two stem cell populations are located at the apical tip of the testis: germline stem cells (GSCs) and somatic stem cells (SSCs) (Fig. 1a). Both GSCs and SSCs contact with a cluster of non-dividing somatic cells known as the hub. SSCs serve both as another component of GSCs niche and as stem cells to generate cyst cells (CCs) which encapsulates the differentiating GBs9.
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