Notch1 signaling promotes the maturation of CD4 and CD8 SP thymocytes

Notch proteins regulate many developmental processes. Notch1 is highly expr essed on thymocytes, but its role in regulating their development is not kn own. We show that activation of Notch1 signaling in CD4(+)CD8(+) double pos itive thymocytes promotes the maturation of both CD4(+) and CD8(+) single p ositive thymocytes and that this occurs in the absence of interactions betw een the T cell receptor and MHC molecules expressed on thymic epithelial ce lls. We have also identified several genes that are transcriptionally regul ated by Notch1 in T cells and show that they are upregulated during maturat ion into both single positive lineages. These observations suggest that Not ch1 signaling plays a role in promoting maturation into both the CD4 and CD 8 T cell lineages.