Pre-TCR signaling inactivates Notch1 transcription by antagonizing E2A

Abstract

Precise control of the timing and magnitude of Notch signaling is essential for the normal development of many tissues, but the feedback loops that regulate Notch are poorly understood. Developing T cells provide an excellent context to address this issue. Notch1 signals initiate T-cell development and increase in intensity during maturation of early T-cell progenitors (ETP) to the DN3 stage. As DN3 cells undergo β-selection, during which cells expressing functionally rearranged TCRβ proliferate and differentiate into CD4+CD8+ progeny, Notch1 signaling is abruptly down-regulated. In this report, we investigate the mechanisms that control Notch1 expression during thymopoiesis. We show that Notch1 and E2A directly regulate Notch1 transcription in pre-β-selected thymocytes. Following successful β-selection, pre-TCR signaling rapidly inhibits Notch1 transcription via signals that up-regulate Id3, an E2A inhibitor. Consistent with a regulatory role for Id3 in Notch1 down-regulation, post-β-selected Id3-deficient thymocytes maintain Notch1 transcription, whereas enforced Id3 expression decreases Notch1 expression and abrogates Notch1-dependent T-cell survival. These data provide new insights into Notch1 regulation in T-cell progenitors and reveal a direct link between pre-TCR signaling and Notch1 expression during thymocyte development. Our findings also suggest new strategies for inhibiting Notch1 signaling in pathologic conditions.

IFN-γ–Producing and IL-17–Producing γδ T Cells Differentiate at Distinct Developmental Stages in Murine Fetal Thymus

“…1D), which is essential for the development of NK1.1 2 NK cell precursors as well as NK1.1 + NK cells (27)(28)(29). The high Id2 expression in DN3 cells was also reported in adult mice (30). Taken together, there might be a possibility that NK cell precursors were present in DN cells, but we did not further analyze the subsets.…”

Specific Notch receptor–ligand interactions control human TCR-ab/gd development by inducing differential Notch signal strength

“…In humans, it is clear that the strongest Notch signals are delivered in uncommitted CD34 + CD1  thymocytes as they express the highest levels of DTX1 and NRARP, genes which are highly sensitive to changes in Notch activation . In contrast, Notch target genes peak at the DN3 stage of mouse T cell development when T cell commitment is completed (Taghon et al, 2006;Tydell et al, 2007;Yashiro-Ohtani et al, 2009), a clear difference compared with human ( Van de Walle et al, 2009). Also NOTCH3, whose expression is induced upon Notch1 signaling, is expressed earlier during human compared with during mouse T cell development.…”

Regulation of innate and adaptive immunity by Notch

“…ID3 inhibits E2A-induced transcription of Notch 1 (REF. 30). As a consequence, double-positive (CD4 + CD8 + ) thymocytes have very low levels of Notch signalling, which is presumably required to avoid interfering with positive and negative selection in double-positive thymocytes, as well as to avoid the oncogenic properties of Notch signalling and its targets 8 (FIG.…”