A genome-wide analysis identifies a notch-RBP-Jκ-IL-7Rα axis that controls IL-17-producing γδ T cell homeostasis in mice

Notch signaling is an important regulator for the development and function of both αβ and γδ T cells, whereas roles of Notch signaling in T cell maintenance remain unclear. We reported previously that the Notch–Hes1 pathway was involved in the intrathymic development of naturally occurring IL-17–producing (IL-17+) γδ T cells. To gain insight into additional roles for the Notch axis in the homeostasis of γδ T cells, we performed a genome-wide analysis of Notch target genes and identified the novel promoter site of IL-7Rα driven by the Notch–RBP-Jκ pathway. Constitutive Notch signaling had the potential to induce IL-7Rα expression on γδ T cells in vivo, as well as in vitro, whereas conditional deletion of RBP-Jκ abrogated IL-7Rα expression, but not Hes1 expression, by γδ T cells and selectively reduced the pool size of IL-7Rαhigh IL-17+ γδ T cells in the periphery. In the absence of IL-7Rα–mediated signaling, IL-17+ γδ T cells were barely maintained in adult mice. Addition of exogenous IL-7 in vitro selectively expanded IL-17+ γδ T cells. Thus, our results revealed a novel role for the Notch–RBP-Jκ–IL-7Rα axis that is independent of Hes1 for homeostasis of IL-17+ γδ T cells.