title: Constitutive Notch signalling promotes CD4 CD8 thymocyte differentiation in the absence of the pre-TCR complex, by mimicking pre-TCR signals.
abstract: Notch1 signalling is essential for the commitment of multipotent lymphocyte precursors towards the alphabeta T-cell lineage and plays an important role in regulating beta-selection in CD4(-)CD8(-) double-negative (DN) thymocytes. However, the role played by Notch in promoting the development of CD4(+)CD8(+) double-positive (DP) thymocytes is poorly characterized. Here, we demonstrate that the introduction of a constitutively active Notch1 (ICN1) construct into RAG(-/-) lymphocyte precursors resulted in the generation of DP thymocytes in in vitro T-cell culture systems. Notably, developmental rescue was dependent not only on the presence of an intact Notch1 RAM domain but also on Delta-like signals, as ICN1-induced DP development in RAG(-/-) thymocytes occurred within an intact thymus or in OP9-DL1 co-cultures, but not in OP9-control co-cultures. Interestingly, ICN1 expression in SLP-76(-/-) precursors resulted in only a minimal developmental rescue to the immature CD8(+) single-positive stage, suggesting that Notch is utilizing the same signalling pathway as the pre-TCR complex. In support of this, ICN1 introduction resulted in the activation of the ERK-MAPK-signalling cascade in RAG(-/-) thymocytes. Taken together, these studies demonstrate that constitutive Notch signalling can bypass beta-selection during early T-cell development by inducing pre-TCR-like signals within a T-cell-promoting environment.
authors.affiliation: Division of Cancer Sciences and Molecular Pathology, Section of Experimental Haematology, Royal Infirmary, University of Glasgow, Glasgow, UK.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Michie
authors.forename: Angela C
authors.initials: AC
authors.lastname: Chan
authors.forename: Maria
authors.initials: M
authors.lastname: Ciofani
authors.forename: Michael
authors.initials: M
authors.lastname: Carleton
authors.forename: Juliette M
authors.initials: JM
authors.lastname: Lefebvre
authors.forename: Yiping
authors.initials: Y
authors.lastname: He
authors.forename: David M
authors.initials: DM
authors.lastname: Allman
authors.forename: David L
authors.initials: DL
authors.lastname: Wiest
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Zúñiga-Pflücker
authors.forename: David J
authors.initials: DJ
authors.lastname: Izon
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation; D008213:Lymphocyte Activation; D054503:Lymphoid Progenitor Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D051881:Receptor, Notch1 / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology* / Q000378:metabolism
chemical_list: C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D011948:Receptors, Antigen, T-Cell