Regulation of T-cell progenitor survival and cell-cycle entry by the pre-T-cell receptor (original) (raw)
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Immunity, 2000
stable antigen (HSA or CD24) can be separated through their expression of CD44 and the IL-2 receptor ␣ chain (CD25) into four consecutive developmental stages: DN CD44 ϩ CD25 Ϫ (stage I), DN CD44 ϩ CD25 ϩ (stage II), DN CD44 Ϫ CD25 ϩ (stage III), and DN CD44 Ϫ CD25 Ϫ (stage TCR  chain rearrangement takes place in the stage III and Biochemistry thymocytes, and, in cells that express a functional TCR 3 Department of Molecular, Cellular,  chain, the  chain associates with the pre-T␣ chain and Developmental Biology to assemble a pre-TCR complex ( ). 4 Howard Hughes Medical Institute Pre-TCR expression occurs during the transition of Yale University School of Medicine stage III to stage IV cells (Hoffman et al., 1996). The New Haven, Connecticut 06520 majority of stage III cells are small in size and either have not completed  chain rearrangement or have outof-frame rearrangements ("E" cells). Approximately 15% Summary of stage III cells, however, are large in size, are often in S phase, and show in-frame  chain rearrangements Activation of the transcription factor NF-B and pre-T ("L" cells) (Figure 1A). Therefore, the L fraction reprecell receptor (pre-TCR) expression is tightly correlated sents cells that have productively rearranged their  during thymocyte development. Inhibition of NF-B in chain and express the pre-TCR (Hoffman et al., 1996). isolated thymocytes in vitro results in spontaneous The assembly of the pre-TCR serves as the first checkapoptosis of cells expressing the pre-TCR, whereas point in T lymphocyte development and is critical for inhibition of NF-B in transgenic mice through expresfurther proliferation and differentiation (von Boehmer sion of a mutated, superrepressor form of IB␣ leads and Fehling, 1997). In mutant mice lacking the recombito a loss of -selected thymocytes. In contrast, the nase proteins RAG1 or RAG2 or in TCR or pre-T␣forced activation of NF-B through expression of a deficient mice, none of which can form a pre-TCR, ␣/ dominant-active IB kinase allows differentiation to T cell development is significantly arrested at the stage proceed to the CD4 ؉ CD8 ؉ stage in a Rag1 Ϫ/Ϫ mouse of stage III thymocytes (Mombaerts et al., 1992a, 1992b; that cannot assemble the pre-TCR. Therefore, signals Shinkai et al., 1992; Fehling et al., 1995). Therefore, sucemanating from the pre-TCR are mediated at least cessful TCR  chain rearrangement is essential for thyin part by NF-B, which provides a selective survival mocyte precursors to proceed to the next developsignal for developing thymocytes with productive  mental stage. chain rearrangements. The signals originating from the pre-TCR that influence the differentiation of developing T lymphocytes Introduction remain to be fully characterized. Recent studies have shown that the pre-TCR exits the endoplasmic reticulum Stages of thymocyte differentiation have been characand is most likely expressed on the cell surface (O'Shea terized through the expression of specific cell surface et al., 1997). Nevertheless, the functioning of the recepmarkers. The most immature thymocytes, which lack extor appears to be independent of a specific ligand, since pression of both coreceptors CD4 and CD8 (CD4 Ϫ CD8 Ϫ mutant forms of pre-T␣ lacking the extracellular domain double-negative [DN] cells), develop into an intermeare also functional in transgenic mice (Irving et al., 1998). diate CD4 ϩ CD8 ϩ double-positive (DP) stage before The requirement of CD3 components in the expression maturing into CD4 ϩ or CD8 ϩ single-positive (SP) cells and functioning of the pre-TCR suggests that signaling and exiting the thymus. It is now clear that DN thymofrom it might resemble that from the TCR (von Boehmer et al., 1998).
Journal of Experimental Medicine, 1998
During thymocyte development, progression from T cell receptor (TCR)  to TCR ␣ rearrangement is mediated by a CD3-associated pre-TCR composed of the TCR  chain paired with pre-TCR ␣ (pT ␣ ). A major issue is how surface expression of the pre-TCR is regulated during normal thymocyte development to control transition through this checkpoint. Here, we show that developmental expression of pT ␣ is time-and stage-specific, and is confined in vivo to a limited subset of large cycling human pre-T cells that coexpress low density CD3. This restricted expression pattern allowed the identification of a novel subset of small CD3 Ϫ thymocytes lacking surface pT ␣ , but expressing cytoplasmic TCR  , that represent late noncycling pre-T cells in which recombination activating gene reexpression and downregulation of T early ␣ transcription are coincident events associated with cell cycle arrest, and immediately preceding TCR ␣ gene expression. Importantly, thymocytes at this late pre-T cell stage are shown to be functional intermediates between large pT ␣ ϩ pre-T cells and TCR ␣ /  ϩ thymocytes. The results support a developmental model in which pre-TCR-expressing pre-T cells are brought into cycle, rapidly downregulate surface pre-TCR, and finally become small resting pre-T cells, before the onset of TCR ␣ gene expression.
Journal of Experimental Medicine, 2013
Expression of the pre-T cell receptor (pT) gene has been exploited in previous studies as a molecular marker to identify tiny cell populations in bone marrow (BM) and blood that were suggested to contain physiologically relevant thymus settling progenitors (TSPs). But to what extent these cells genuinely contribute to thymopoiesis has remained obscure. We have generated a novel pT iCre knockin mouse line and performed lineagetracing experiments to precisely quantitate the contribution of pT-expressing progenitors to distinct differentiation pathways and to the genealogy of mature hematopoietic cells under physiological in vivo conditions. Using these mice in combination with fluorescent reporter strains, we observe highly consistent labeling patterns that identify pT expression as a faithful molecular marker of T lineage commitment. Specifically, the fate of pT-expressing progenitors was found to include all and most T cells but, in contrast to previous assumptions, to exclude B, NK, and thymic dendritic cells. Although we could detect small numbers of T cell progenitors with a history of pT expression in BM and blood, our data clearly exclude these populations as physiologically important precursors of thymopoiesis and indicate that they instead belong to a pathway of T cell maturation previously defined as extrathymic.
Constitutive expression of the pre-TCR enables development of mature T cells
International Immunology, 2006
Expression and signalling through the pre-TCR and the TCRab resemble two critical checkpoints during T cell development. We investigated to which extent a pre-TCR can functionally replace mature TCRa chains during T cell development. For this purpose, transgenic mice were generated expressing the pre-TCRa (pTa) under the transcriptional control of TCRb regulatory elements. We report here on the interesting finding that constitutive pTa expression allows complete T cell maturation. The pre-TCR complex permits a subset of b-selected thymocytes to mature in the absence of TCRa into peripheral T cells (bT cells) comprising up to 10% of all lymphocytes. Lymphopenia-driven proliferation of these bT cells is similar to that of conventional abT cells. Furthermore, bT cells proliferated and acquired effector function upon stimulation with allogeneic MHC.
The BCL2A1 gene as a preT cell receptor- induced regulator of thymocyte survival
2000
The pre-T cell receptor (TCR) is expressed early during T cell development and imposes a tight selection for differentiating T cell progenitors. Pre-TCR-expressing cells are selected to survive and differentiate further, whereas pre-TCR Ϫ cells are "negatively" selected to die. The mechanisms of pre-TCR-mediated survival are poorly understood. Here, we describe the induction of the antiapoptotic gene BCL2A1 (A1) as a potential mechanism regulating inhibition of pre-T cell death. We characterize in detail the signaling pathway involved in A1 induction and show that A1 expression can induce pre-T cell survival by inhibiting activation of caspase-3. Moreover, we show that in vitro "knockdown" of A1 expression can compromise survival even in the presence of a functional pre-TCR. Finally, we suggest that pre-TCRinduced A1 overexpression can contribute to T cell leukemia in both mice and humans.
The Journal of Immunology, 2000
In-frame rearrangement of the TCR-beta locus and expression of the pre-TCR are compulsory for the production of CD4+8+ thymocytes from CD4-8- precursors. Signals delivered via the pre-TCR are thought to induce the differentiation process as well as the extensive proliferation that accompanies this transition. However, it is equally possible that pre-TCR expression is required for the success of this transition, but does not play a direct role in the inductive process. In the present manuscript we examine this possibility using a variety of normal and genetically modified mouse models. Our evidence shows that differentiation and mitogenesis can both occur independently of pre-TCR expression. However, these processes are absolutely dependent on the presence of normal thymic architecture and cellular composition. These findings are consistent with a checkpoint role for the pre-TCR in regulating the divergence of survival and cell death fates at the CD4-8- to CD4+8+ transition. Further, our data suggest that precursor thymocyte differentiation is induced by other, probably ubiquitous, mechanisms that require the presence of normal thymic cellularity, composition, and architecture.
Journal of Experimental Medicine, 2013
Expression of the pre–T cell receptor α (pTα) gene has been exploited in previous studies as a molecular marker to identify tiny cell populations in bone marrow (BM) and blood that were suggested to contain physiologically relevant thymus settling progenitors (TSPs). But to what extent these cells genuinely contribute to thymopoiesis has remained obscure. We have generated a novel pTαiCre knockin mouse line and performed lineage-tracing experiments to precisely quantitate the contribution of pTα-expressing progenitors to distinct differentiation pathways and to the genealogy of mature hematopoietic cells under physiological in vivo conditions. Using these mice in combination with fluorescent reporter strains, we observe highly consistent labeling patterns that identify pTα expression as a faithful molecular marker of T lineage commitment. Specifically, the fate of pTα-expressing progenitors was found to include all αβ and most γδ T cells but, in contrast to previous assumptions, to ...
Regulation of pre-T cell receptor (pTα-TCRβ) gene expression during human thymic development
Journal of Experimental Medicine
In murine T cell development, early thymocytes that productively rearrange the T cell receptor (TCR) beta locus are selected to continue maturation, before TCR alpha expression, by means of a pre-TCR alpha- (pT alpha-) TCR beta heterodimer (pre-TCR). The aim of this study was to identify equivalent stages in human thymocyte development. We show here that variable-diversity-joining region TCR beta rearrangement and the expression of full-length TCR beta transcripts have been initiated in some immature thymocytes at the TCR alpha/beta- CD4+CD8- stage, and become common in a downstream subset of TCR alpha/beta- CD4+CD8+ thymocytes that is highly enriched in large cycling cells. TCR beta chain expression was hardly detected in TCR alpha/beta- CD4+CD8- thymocytes, whereas cytoplasmic TCR beta chain was found in virtually all TCR alpha/beta- CD4+CD8+ blasts. In addition, a TCR beta complex distinct from the mature TCR alpha/beta heterodimer was immunoprecipitated only from the latter subs...
The Journal of Immunology, 2007
The factors that regulate the rate of production of T cells by the thymus remain incompletely defined. To test whether generation of functional T cell receptors limits the rate of thymic T cell export, we made use of a line of mice, LN3␣, that have endogenously prerearranged TCR genes. The prerearranged TCR genes were expressed abnormally early in hemopoietic development, indicating that RAG-mediated recombination, rather than transcription factor expression, is the key determinant of the initiation of robust TCR transcription. Thymic T cell export rates were similar between wild-type (wt) and LN3␣ mice, indicating that T cell maturation rates in these mice are determined by factors other than TCR gene rearrangement. In competitive bone marrow chimeras, however, LN3␣ thymocytes were out-competed by wt cells and failed to develop beyond the double-negative 4 stage. Furthermore, wt progenitors transplanted intrathymically into LN3␣ mice proliferated excessively, suggesting that increased proliferative signals in the LN3␣ thymus compensate for faulty T cell development driven by early TCR expression.