Developmental progression of fetal HEB(-/-) precursors to the pre-T-cell stage is restored by HEBAlt.
Gene knockout studies have shown that the E-protein transcription factor HEB is required for normal thymocyte development. We have identified a unique form of HEB, called HEBAlt, which is expressed only during the early stages of T-cell development, whereas HEBCan is expressed throughout T-cell development. Here, we show that HEB(-/-) precursors are inhibited at the β-selection checkpoint of T-cell development due to impaired expression of pTα and function of CD3ε, both of which are necessary for pre-TCR signaling. Transgenic expression of HEBAlt in HEB(-/-) precursors, however, upregulated pTα and allowed development to CD4(+) CD8(+) stage in fetal thymocytes. Moreover, HEBAlt did overcome the CD3ε signaling defect in HEB(-/-) Rag-1(-/-) thymocytes. The HEBAlt transgene did not permit Rag-1(-/-) precursors to bypass β-selection, indicating that it was not acting as a dominant negative inhibitor of other E-proteins. Therefore, our results provide the first mechanistic evidence that HEBAlt plays a critical role in early T-cell development and show that it can collaborate with fetal thymic stromal elements to create a regulatory environment that supports T-cell development past the β-selection checkpoint.
Sunnybrook Health Sciences Centre and Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
Marsela
M
Braunstein
Michele K
MK
Anderson
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D017252:CD3 Complex / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005333:Fetus / Q000276:immunology / Q000378:metabolism; D055785:Gene Knockdown Techniques; D018398:Homeodomain Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D054504:Precursor Cells, T-Lymphoid / Q000166:cytology / Q000276:immunology*; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*
D051792:Basic Helix-Loop-Helix Proteins; D017252:CD3 Complex; D018398:Homeodomain Proteins; D020033:Protein Isoforms; D011948:Receptors, Antigen, T-Cell; C485468:Cd3e protein, mouse; C489532:Tcf12 protein, mouse; C064658:RAG-1 protein