Role of WDFY4 in Treg development

Project Summary/Abstract Regulatory T cells (Tregs) are essential for maintaining immune tolerance, but the mechanisms governing their activation are not fully understood. Our preliminary data reveals a novel role for cDC1, a type of dendritic cell previously thought to primarily activate CD8 T cells, in Treg activation. We have found that cDC1s uniquely present self-antigens on MHCII molecules, a process crucial for Treg development and maintenance. Additionally, our CRISPR/Cas9 screen identified WDFY4, a BEACH domain protein, as essential for antigen presentation by cDC1s. This project will investigate the hypothesis that cDC1s utilize a WDFY4-dependent pathway to coordinate both MHC class I and II antigen processing from specific sources, particularly cell- associated antigens. This pathway is hypothesized to be critical for both effective immune responses against viruses and tumors, as well as for Treg selection and survival, thereby preventing autoimmunity. The proposed research aims to: 1) Determine the impact of WDFY4 on the T cell receptor (TCR) repertoire, particularly in Tregs, to identify self-reactive TCRs dependent on WDFY4 and assess their function in vivo; 2) Compare the MHC class I and II immunopeptidomes of cDC1s and cDC2s in the presence and absence of WDFY4 to identify the cellular source of self-peptides dependent on WDFY4 for presentation.; and 3) Identify and validate WDFY4 interacting proteins to elucidate the molecular mechanism by which WDFY4 controls MHCII antigen processing for self-antigens. This research has the potential to redefine our understanding of the immune mechanisms underlying coordinated antigen presentation and revolutionize current paradigms of immune response orchestration by cDC1s. Understanding these mechanisms could lead to novel therapeutic approaches for autoimmune diseases, cancer, and infectious diseases.