Identification of an Il9 gene locus regulatory element in mast cells and basophils

Abstract

Abstract Interleukin 9 (IL-9) is a pleiotropic cytokine that plays a central role in immunological disorders. Extensive work has been done to describe the Il9 gene locus and its transcriptional regulation in Th9 and other T cell subsets. Some innate immune cells, such as mast cells and basophils, can also produce a substantial amount of IL-9 in an inflammatory milieu. However, very little is known about how the Il9 gene is regulated in these cells. In this study, we show for the first time that IL-33, and not IgE cross linking, induces IL-9 production in mast cells and basophils and that this is an IL-3 dependent effect. Using the CRISPR-Cas9-mediated deletion approach, we show that IL-9 production in mast cells and basophils is dependent on a conserved non-coding sequence -25 kb (CNS-25) upstream of the IL-9 promoter. Our results show that the CNS-25 region is important for mast cell and basophil IL-9 production in vitro and in vivo. ChIP assays show that the CNS-25 can bind multiple transcription factors at a higher magnitude than the Il9 promoter. Additionally, this region has high chromatin remodeling and p300, an acetyl transferase, binding in mast cells. We show that p300 is essential for IL-33 induced IL-9 production in mast cells and basophils. Taken together, our data define a mechanism for Il9 gene regulation orchestrated by IL-33 and IL-3 signaling in mast cells and basophils.