Expression data from Tcf1-expressing Thy1+CD25+ T lineage cells

We used microarrays to perform a global gene expression analysis in Tcf1-expressing Thy1+CD25+ T lineage cells that develop on OP9 stroma in the absence of Notch1 signals. We compare this to the starting population, LMPP progenitors, and to control expressing T lineage cells that developed on OP9 stroma expressing Notch ligand DL4. The overall goal of this study was to determine if Tcf1 initiates T lineage specification in lymphoid progenitors. We found that Tcf1 was sufficient to upregulate many T lineage genes as compared to control expressing progenitors on OP9-DL4. Abstract of manuscript: The thymus imposes the T cell fate on incoming multipotent progenitors, but the molecular mechanisms are poorly understood. We show that transcription factor Tcf1 initiates T-lineage-specific gene expression. Tcf1 is downstream of Notch1 signaling and expressed in early T-cell progenitors. Progenitors deficient for Tcf1 are unable to initiate normal T-lineage specification. Conversely, ectopic expression of Tcf1 in hematopoietic progenitors is sufficient to induce expression of T-lineage specific genes in vitro. Thus, our study identifies Tcf1 as critically involved in the establishment T cell identity. Wiltype LMPPs were isolated by a FACSAria cell sorter and retrovirally transduced with a Tcf1-containing (Tcf1-VEX) or control vector (VEX) retrovirus. Tcf1-expressing cells and control-vector expressing cells were then seeded on OP9 stroma or OP9 stroma expressing Notch ligand DL4, respectively. On day 10, Thy1+CD25+ T lineage cells were sorted from Tcf1-expressing cells on OP9 stroma and compared to sorted LMPPs and Thy1+CD25+ T lineage cells that developed from control-vector expressing cells on OP9-DL4.