Gads is differentially required for the thymic development of conventional and innate-like T cells

Abstract

Abstract Thymocyte development is tightly regulated by TCR signaling. Gads bridges a TCR-inducible interaction between SLP-76 and LAT, two adaptors that are essential for T cell development. In contrast, Gads-deficient mice have moderately impaired thymic development and accumulate non-naive peripheral T cells of unclear origin. To illuminate the regulatory roles of Gads, we developed a model for tamoxifen-induced ablation of Gads (Gads iKO), accompanied by the expression of tdTomato. Using this model, we followed the fate of Gads iKO(Tom +) and Gads +(Tom −) thymocytes within the same mouse. Compared to Gads +(Tom −) DN thymocytes, Gads iKO(Tom +) DN thymocytes were less likely to undergo conventional β-selection; yet their ability to develop into γδ or NKT cells was not impaired. A key feature of thymocyte development is the TCR-induced upregulation of CD5, which occurs during β-selection and further increases upon positive selection. Nevertheless, most Gads iKODP thymocytes did not express CD5, nor did they increase calcium upon TCR ligation. These observations suggest that a TCR-independent, innate-like thymic developmental pathway may be unmasked in the absence of Gads. Gads iKOSP thymocytes were heterogeneous: some were CD5 −TCR lo, while others were CD5 +TCR hi. Among the CD5 +Gads iKOCD4 SP thymocytes, a large proportion exhibited innate-like characteristics such CD44 hiCD62L loand/or NK1.1 +. In contrast, peripheral Gads iKOT cells maintained a naive CD44 loCD69L hiphenotype for up to five weeks. Our results suggest that Gads is dispensable for peripheral quiescence, but regulates thymic development, by promoting conventional αβ T cell development, while suppressing innate-like developmental fates. Supported by a grant from the Israel Science Foundation, and by a short-term grant from the Rappaport Institute for Research in the Medical Sciences