Thymocyte maturation is regulated by the activity of the helix-loop-helix protein

Abstract

pathways, including early B and T lymphopoiesis. Here, we provide in vitro and in vivo evidence demonstrating that E47 activity regulates double-positive thymocyte maturation. In the absence of E47 activity, positive selection of both major histocompatibility complex (MHC) class I – and class II–restricted T cell receptors (TCRs) is perturbed. Additionally, development of CD8 lineage T cells in an MHC class I–restricted TCR transgenic background is sensitive to the dosage of E47. Mice deficient for E47 display an increase in production of mature CD4 and CD8 lineage T cells. Furthermore, ectopic expression of an E2A inhibitor helix-loop-helix protein, Id3, promotes the in vitro differentiation of an immature T cell line. These results demonstrate that E2A functions as a regulator of thymocyte positive selection. Key words: E2A • positive selection • thymocyte development • helix-loop-helix 1 Abbreviations used in this paper: �2M, �2-microglobulin; BrdU, bromodeoxyuridine; DP, double-positive; EGFP, enhanced green fluorescent protein; HEB, HeLa E-box binding protein; HLH, helix-loop-helix; HSA, heat stable antigen; PDP, peripheral DP; RAG, recombination activatin