Generation of an ILC3-specific Cre driver in mice

SUMMARY This proposal aims to generate a Cre driver in mice that can be used to investigate the distinct functions and contributions of type 3 innate lymphoid cells (ILC3s) in immune responses and diseases. ILC3s, similar to CD4+ helper T lymphocytes (Th), play crucial roles in host defense and in maintaining tissue homeostasis. However, the functional overlap between ILC3s and Th17 cells has made it challenging to study their specific contributions in these and other contexts. Our research team identified an ILC3-specific enhancer (E22-2) associated with the Il22 gene, which encodes a type 3 signature cytokine. We now propose to generate a mouse strain with ILC3- specific expression of GFP-IRES-Cre using CRISPR-mediated targeting of a single-copy BAC-Il22 reporter (22- GFP) containing E22-2 and exhibiting GFP expression that is exquisitely restricted to mature ILC3s. The specificity and extent of Cre-mediated deletion will be determined by crossing the ILC3-specific Cre mice (22- GFPCre) with a flox-STOP-TdTomato reporter strain. Successful completion of this project will facilitate genetic engineering and targeted manipulation to study the ILC3-specific functions of specific factors without confounding effects on Th17 or iNKT17 cells. Examples of such future studies include establishing the roles of type 3 cytokines (IL-22 and IL-17A/F) in controlling infections, inflammatory bowel diseases, oncogenesis, and innate immune responses to cancer. Additionally, deployment of the new Cre driver will shed light on factors that govern the functional plasticity of ILC3s in inflammatory settings.