Expression of Notch target genes and T-lineage markers in extrathymic T-lineage progenitors. Real-time quantitative RT-PCR was performed on RNA from sorted spleen T-lineage progenitors at 2 weeks after BMT (spleen Thy1.2^–CD44⁺ and SpT cells as defined in Figure 2). BM LSK, thymic ETP, and DN2 and DN3 and CD4⁺CD8⁺ DP cells from B6 mice were analyzed for comparison. Numbers on the y-axis are arbitrary units with the amount of mRNA found in ETPs set to 1. Data are shown as mean ± SD of 3 to 4 independent samples assessed in duplicate (except for Thy1.2^–CD44⁺ cells, 1 sample). (A) Expression of the Notch target genes Dtx1 and Hes1, as well as the Notch receptors Notch1, Notch2, and Notch3, after normalization for Hprt1. (B) Expression of the T-lineage differentiation markers CD3ϵ and Ptcra, of the transcription factor Gata3, and of the Wnt target gene Tcf1.