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Induction of the early growth response (Egr) family of transcription factors during thymic selection.

Shao H, Kono DH, Chen LY, Rubin EM, Kaye J - J. Exp. Med. (1997)

Bottom Line: A similar pattern of expression is found for family members Egr-2 and Egr-3.In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1.The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
There is little known about the regulation of gene expression during TCR-mediated differentiation of immature CD4+8+ (double positive) thymocytes into mature T cells. Using the DPK CD4+8+ thymocyte precursor cell line, we demonstrate that the early growth response-1 gene (Erg-1), encoding a zinc finger transcription factor, is rapidly upregulated after TCR stimulation. We also report that Egr-1 is expressed by a subset of normal double positive thymocytes in the thymic cortex, as well by a majority of medullary single positive thymocytes. Expression of Egr-1 is dramatically reduced in the thymus of major histocompatibility complex knockout mice, but can be induced by anti-CD3 antibody stimulation of isolated thymocytes from these animals. These and other data suggest that high level expression of Egr-1 in the thymus is a consequence of selection. A similar pattern of expression is found for family members Egr-2 and Egr-3. Using the DPK cell line, we also demonstrate that expression of Egr-1, 2, and 3 is dependent upon ras activation, as is the initiation of differentiation to a single positive cell. In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1. The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

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Expression of Egr-2  and Egr-3 mRNA in thymocytes  is MHC dependent. Total RNA  prepared from freshly isolated  wild-type or MHC knockout  thymocytes was subjected to  RT-PCR analysis using CD4,  Egr-2 (Krox-20), or Egr-3 primers as indicated.
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Figure 7: Expression of Egr-2 and Egr-3 mRNA in thymocytes is MHC dependent. Total RNA prepared from freshly isolated wild-type or MHC knockout thymocytes was subjected to RT-PCR analysis using CD4, Egr-2 (Krox-20), or Egr-3 primers as indicated.

Mentions: Similar to results obtained with DPK cells, both Krox-20 (Egr-2) and Egr-3 mRNA are also expressed in normal thymocytes, while there is no detectable expression of these genes in thymocytes derived from MHC-deficient animals (Fig. 7). These results are consistent with the coordinate upregulation of the Egr family of transcription factors during thymic selection.


Induction of the early growth response (Egr) family of transcription factors during thymic selection.

Shao H, Kono DH, Chen LY, Rubin EM, Kaye J - J. Exp. Med. (1997)

Expression of Egr-2  and Egr-3 mRNA in thymocytes  is MHC dependent. Total RNA  prepared from freshly isolated  wild-type or MHC knockout  thymocytes was subjected to  RT-PCR analysis using CD4,  Egr-2 (Krox-20), or Egr-3 primers as indicated.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196139&req=5

Figure 7: Expression of Egr-2 and Egr-3 mRNA in thymocytes is MHC dependent. Total RNA prepared from freshly isolated wild-type or MHC knockout thymocytes was subjected to RT-PCR analysis using CD4, Egr-2 (Krox-20), or Egr-3 primers as indicated.
Mentions: Similar to results obtained with DPK cells, both Krox-20 (Egr-2) and Egr-3 mRNA are also expressed in normal thymocytes, while there is no detectable expression of these genes in thymocytes derived from MHC-deficient animals (Fig. 7). These results are consistent with the coordinate upregulation of the Egr family of transcription factors during thymic selection.

Bottom Line: A similar pattern of expression is found for family members Egr-2 and Egr-3.In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1.The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
There is little known about the regulation of gene expression during TCR-mediated differentiation of immature CD4+8+ (double positive) thymocytes into mature T cells. Using the DPK CD4+8+ thymocyte precursor cell line, we demonstrate that the early growth response-1 gene (Erg-1), encoding a zinc finger transcription factor, is rapidly upregulated after TCR stimulation. We also report that Egr-1 is expressed by a subset of normal double positive thymocytes in the thymic cortex, as well by a majority of medullary single positive thymocytes. Expression of Egr-1 is dramatically reduced in the thymus of major histocompatibility complex knockout mice, but can be induced by anti-CD3 antibody stimulation of isolated thymocytes from these animals. These and other data suggest that high level expression of Egr-1 in the thymus is a consequence of selection. A similar pattern of expression is found for family members Egr-2 and Egr-3. Using the DPK cell line, we also demonstrate that expression of Egr-1, 2, and 3 is dependent upon ras activation, as is the initiation of differentiation to a single positive cell. In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1. The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

Show MeSH