Gene expression analysis of intestinal stem cells (ISCs) from polyI:C treated WT mice or Ifnar1-/- mice.

To explore the influence of IFNR-mediated singnaling in ISCs, we performed microarray analysis of the ISCs from control Lgr5ki mice versus Ifnar1-/-Lgr5ki mice after treating for 1 weeks with low doses of poly(I:C), which potentially induce type I and -III IFNs. The Gene Ontology (GO) analysis indicated that the GO terms overrepresented among the genes upregulated in ISCs from poly(I:C)-treated WT mice compared with those from poly(I:C)-treated Ifnar1−/− mice included “defense response to virus”, “immune system process”, “response to virus”, and “innate immune response”, all from the GOTERM_Biological Processes (BP) category. We compared these results against the Interferome database, which contains genes regulated by type I, II, or III IFN, compiled by analyzing the expression data of IFN-treated cells (http://www.interferome.org), and found that most of the genes found for the GO term “defense response to virus” were IFN-inducible genes, indicating that IFNs act directly on ISCs. The GO analysis also showed an enrichment of defense response to bacteria. In the GOTERM_Cellular Component (CC) category, “extracellular space” and “extracellular region” ranked at the top, indicating a dramatic change in the expression pattern of secretory molecules. Notably, these GO terms included genes encoding antibacterial proteins and endocrine hormones such as angiogenin, defensin, lysozyme, chromogranin, and glucagon, all of which are produced by secretory IECs. Thus, we hypothesized that excess IFN signals force ISCs to lose stemness and differentiate into secretory progenitors. Control Lgr5ki mice or Ifnar1-/-:Lgr5ki mice were injected intraperitoneally with 2 mg/kg BW of poly(I:C) (Sigma) every day for 1 week, then ISCs were isolated by FCM.