Protein degradation is required for normal proliferation of Drosophila intestinal stem cells

Adult stem cells are necessary for the maintenance of many tissues, including the skin, blood, and intestinal lining. While most adult somatic cells have exited the cell cycle, adult stem cells maintain the ability to divide throughout an organism's lifetime. A recent study suggested that protein degradation may be important for cell cycle regulation in Drosophila intestinal stem cells. We hypothesized that two specific E3 ubiquitin ligase complexes, CRL4Cdt2 and SCFSkp2, might be required in Drosophila intestinal stem cells because both have been shown to mediate the destruction of the cell cycle inhibitor Dacapo (Dap). In this preliminary study, we used RNAi to knock down either Cdt2 or Skp2 to reduce the activity of either CRL4Cdt2 or SCFSkp2, respectively, in the adult intestine. Adult intestines with knockdown of either Cdt2 or Skp2 exhibited significant decreases in mitotic activity as well as changes in intestinal morphology. Our findings suggest that protein degradation mediated by both CRL4Cdt2 and SCFSkp2 is required for intestinal stem cell function and maintenance of the adult intestinal lining. Future experiments should explore specific proteins that accumulate following knockdown of Cdt2 or Skp2 and link protein accumulation to changes in stem cell function.