PROJECT SUMMARY: The relationship between psoriatic skin and joint disease remains enigmatic. A subset of patients with psoriasis develop arthritis, early diagnosis of which is challenging. Additionally, therapies for skin disease are less successful at treating arthritis. A20 (Tnfaip3) is a broadly-expressed protein that restricts multiple inflammatory signaling pathways and is genetically associated with both psoriasis and psoriatic arthritis in humans. However, the molecular and tissue-specific mechanisms by which A20 restricts psoriatic disease are unknown. Our preliminary data shows that A20's capacity for binding linear ubiquitin is critical for preventing distal digit psoriatic skin and joint disease in mice, with pathology requiring TNF, IL17A, and T-cells. Early disease surrounded the epidermis; therefore, we generated mice allowing inducible deletion of A20 only in keratinocytes in adulthood (A20iEKO mice). Remarkably, these mice also develop similar psoriatic skin and joint disease that requires TNF, IL17A, and T-cells. I aim to determine the immune mechanisms by which A20 dysregulation in keratinocytes orchestrates skin and joint disease. Aim 1 centers around understanding the cytokine requirements for coordinating the pathogenic immune infiltrate. In Aim 2 I will dissect the role of T- cells by determining which subsets or antigen-specific cells are critical for pathogenic cytokine secretion as well as their anatomical sites of action. Aim 3 focuses on the cell-intrinsic role of A20 in keratinocytes, where I plan to understand the mechanisms by which A20 restricts inflammatory pathways in vivo, during keratinocyte differentiation, and downstream TNFR and IL17R. Together, these studies will reveal how keratinocytes can orchestrate an inflammatory process that results in psoriatic skin and joint disease. This is relevant to NIAMS because these studies may help explain how human psoriasis is connected to psoriatic arthritis and may reveal novel therapeutic targets or biomarkers for early or potential arthritic disease. My long-term goal is to establish an independent research program studying how inflammation remains localized within epithelial tissues such as the skin. The studies described above will provide an outstanding starting point as they aim to understand how skin dysregulation can cause joint inflammation. My research background is primarily in cellular signaling and protein biochemistry. My career development aims are to build my intellectual and scientific foundation in cellular immunology and develop professional relationships with rheumatology-focused researchers. I also plan on developing key research skills in epithelial biology as well as transcriptomic and statistical analysis. These development goals will be pursued with didactic courses along with participation in seminar series, workshops, and conferences. Together with mentorship from Dr. Averil Ma, a leading molecular immunologist, and guidance from a multidisci...