Transcriptional profiling analysis of pre-selected DP thymocytes in response to positive and negative selection signals

Sustained Ca2+ entry into CD4+CD8+ double-positive thymocytes is required for positive selection. We identified a voltage-gated Na+ channel (VGSC), essential for positive selection of CD4+ T cells. Pharmacological inhibition of VGSC activity inhibited sustained Ca2+ influx induced by positive-selecting ligands and in vitro positive selection of CD4+ but not CD8+ T cells. In vivo shRNA knockdown of Scn5a specifically inhibited positive selection of CD4+ T cells. Ectopic expression of VGSC in peripheral AND CD4+ T cells bestowed the ability to respond to a positively selecting ligand, directly demonstrating VGSC expression was responsible for increased sensitivity. Thus active VGSCs in thymocytes provides a mechanism by which a weak positive selecting signal can induce sustained Ca2+ signals required for CD4+ T cell development. Pre-selected AND DP thymocytes were stimulated with plate bound peptide-loaded I-Ek Ig dimers. Genes were differentially regulated by positive and negative selection signals. The goal of this study is to identify ion-channel related genes critical for thymic positive selection, given the sustained Ca2+ entry into double positive thymocytes is required for positive selection. Total RNA of pre-selected AND thymocytes stimulated with I-Ek Ig dimers loaded with the positively-selecting peptide gp250, the negatively-selecting agonist peptide MCC, or the non-selecting control peptide Hb were used for the transcriptional profiling analysis. We found 28 genes were differentially down-regulated by MCC stimulation but upregulated by gp250 stimulation. One of them, scn4b, was ion-channel related.