Classification of novel conditional POSH knockout murine models

Abstract

Abstract Plenty of SH3 Domains (POSH) is a critical scaffold protein in neuronal and lymphocyte signaling involved in survival, development, and effector function. Our lab has shown a sharp decline in survival and activation in T cells and decreased survival of lymphocyte leukemias upon inhibition of POSH function in vitro. However, the in vivo function of POSH in lymphocyte survival and function has not been examined. We hypothesized that POSH deletion in vivo impacts murine lymphocyte development and effector function. We used the Cre/Lox system to conditionally knockout POSH in T cells (CD4-Cre) or B cells (CD19-Cre) in C57B6 mice. POSH deletion in lymphocytes was examined through Western Blot and RNA extraction, and the effect of the loss of POSH on development and function was assessed via flow cytometry. We found that CD4-Cre T cells showed a developmental block at the maturation stage in the thymus. Upon stimulation, CD4-Cre T cells showed reduced proliferation and cytokine production. Additionally, CD19-Cre B cells showed developmental defects, including more BP-1 expression and a higher frequency of Pre-B early cells. This study demonstrated that the in vivo deletion of POSH impacts development, proliferation, and effector function of lymphocytes. These data corroborate previous in vitro results with our inhibitor. Thus, these novel murine models will enable us to assess the role of POSH in developing a fully functional immune compartment and its role in supporting leukemia oncogenesis and survival. Supported by grants from NIH-MBARC, NIBIB (EB026560), NIGMS (GM135744), DoD (RT160149)