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Two distinct steps during thymocyte maturation from CD4-CD8- to CD4+CD8+ distinguished in the early growth response (Egr)-1 transgenic mice with a recombinase-activating gene-deficient background.

Miyazaki T - J. Exp. Med. (1997)

Bottom Line: The early growth response (Egr)-1 is a zinc finger-containing transcription factor belonging to the immediate-early genes.In transgenic mice overexpressing Egr-1 in a recombinase-activating gene-deficient background, thymocytes bypassed the block at the CD25+CD44- DN stage and matured to the immature CD8 single-positive (ISP) cell stage, but not further to the CD4/CD8 double-positive (DP) cell stage.The first step, from the CD25+CD44- DN to the ISP stage, can be entirely promoted by overexpression of Egr-1.

View Article: PubMed Central - PubMed

Affiliation: Basel Institute for Immunology, Postfach CH-4005, Basel, Switzerland. miyazaki@bii.ch

ABSTRACT
The early growth response (Egr)-1 is a zinc finger-containing transcription factor belonging to the immediate-early genes. Its expression in CD4/CD8 double negative (DN) immature thymocytes suggests that Egr-1 expression may be involved in early thymocyte development. In transgenic mice overexpressing Egr-1 in a recombinase-activating gene-deficient background, thymocytes bypassed the block at the CD25+CD44- DN stage and matured to the immature CD8 single-positive (ISP) cell stage, but not further to the CD4/CD8 double-positive (DP) cell stage. When these mice were irradiated, thymocytes did develop to the DP stage, suggesting transcriptional induction of additional genes by irradiation that are required to promote thymocyte development from the ISP to the DP stage. These results provide genetic evidence for two distinct steps during early thymocyte development from the CD25+CD44- DN to the DP stage. The first step, from the CD25+CD44- DN to the ISP stage, can be entirely promoted by overexpression of Egr-1.

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Increased endogenous Egr-1 expression in  CD25−CD44− DN thymocytes  of wild-type (C57Bl/6) mice.  CD25+CD44− DN, CD25−  CD44− DN, and DP thymocytes  were sorted from C57Bl/6 (B6)  mice, total RNA was isolated,  and the expression of Egr-1 gene was assessed by semiquantitative RT-PCR. The amount of template cDNA for PCR corresponds to 5 × 104,  5 × 103, or 103 cells from the left lane to the right in each type of cell.
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Figure 1: Increased endogenous Egr-1 expression in CD25−CD44− DN thymocytes of wild-type (C57Bl/6) mice. CD25+CD44− DN, CD25− CD44− DN, and DP thymocytes were sorted from C57Bl/6 (B6) mice, total RNA was isolated, and the expression of Egr-1 gene was assessed by semiquantitative RT-PCR. The amount of template cDNA for PCR corresponds to 5 × 104, 5 × 103, or 103 cells from the left lane to the right in each type of cell.

Mentions: Shao et al. recently described Egr-1 expression in DN thymocytes of mice using intracellular fluorocytometry and suggested the possible involvement of Egr-1 expression during β selection in immature thymocytes (36). Because the pre-TCR–expressing population in DN thymocytes can be distinguished by CD25/CD44 expression, endogenous Egr-1 expression was dissected in DN thymocytes from wild-type C57Bl/6 (B6) mice by semiquantitative reverse transcriptase PCR (RT-PCR), using sorted CD25+CD44− cells that precede pre-TCR expression, and CD25−CD44− cells that express the pre-TCR complex. As shown in Fig. 1, much higher endogenous Egr-1 expression was detected in CD25−CD44− cells than in CD25+CD44− cells. Egr-1 was expressed at even higher levels in DP cells than in CD25− CD44− DN cells, consistent with the recent report (36).


Two distinct steps during thymocyte maturation from CD4-CD8- to CD4+CD8+ distinguished in the early growth response (Egr)-1 transgenic mice with a recombinase-activating gene-deficient background.

Miyazaki T - J. Exp. Med. (1997)

Increased endogenous Egr-1 expression in  CD25−CD44− DN thymocytes  of wild-type (C57Bl/6) mice.  CD25+CD44− DN, CD25−  CD44− DN, and DP thymocytes  were sorted from C57Bl/6 (B6)  mice, total RNA was isolated,  and the expression of Egr-1 gene was assessed by semiquantitative RT-PCR. The amount of template cDNA for PCR corresponds to 5 × 104,  5 × 103, or 103 cells from the left lane to the right in each type of cell.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199048&req=5

Figure 1: Increased endogenous Egr-1 expression in CD25−CD44− DN thymocytes of wild-type (C57Bl/6) mice. CD25+CD44− DN, CD25− CD44− DN, and DP thymocytes were sorted from C57Bl/6 (B6) mice, total RNA was isolated, and the expression of Egr-1 gene was assessed by semiquantitative RT-PCR. The amount of template cDNA for PCR corresponds to 5 × 104, 5 × 103, or 103 cells from the left lane to the right in each type of cell.
Mentions: Shao et al. recently described Egr-1 expression in DN thymocytes of mice using intracellular fluorocytometry and suggested the possible involvement of Egr-1 expression during β selection in immature thymocytes (36). Because the pre-TCR–expressing population in DN thymocytes can be distinguished by CD25/CD44 expression, endogenous Egr-1 expression was dissected in DN thymocytes from wild-type C57Bl/6 (B6) mice by semiquantitative reverse transcriptase PCR (RT-PCR), using sorted CD25+CD44− cells that precede pre-TCR expression, and CD25−CD44− cells that express the pre-TCR complex. As shown in Fig. 1, much higher endogenous Egr-1 expression was detected in CD25−CD44− cells than in CD25+CD44− cells. Egr-1 was expressed at even higher levels in DP cells than in CD25− CD44− DN cells, consistent with the recent report (36).

Bottom Line: The early growth response (Egr)-1 is a zinc finger-containing transcription factor belonging to the immediate-early genes.In transgenic mice overexpressing Egr-1 in a recombinase-activating gene-deficient background, thymocytes bypassed the block at the CD25+CD44- DN stage and matured to the immature CD8 single-positive (ISP) cell stage, but not further to the CD4/CD8 double-positive (DP) cell stage.The first step, from the CD25+CD44- DN to the ISP stage, can be entirely promoted by overexpression of Egr-1.

View Article: PubMed Central - PubMed

Affiliation: Basel Institute for Immunology, Postfach CH-4005, Basel, Switzerland. miyazaki@bii.ch

ABSTRACT
The early growth response (Egr)-1 is a zinc finger-containing transcription factor belonging to the immediate-early genes. Its expression in CD4/CD8 double negative (DN) immature thymocytes suggests that Egr-1 expression may be involved in early thymocyte development. In transgenic mice overexpressing Egr-1 in a recombinase-activating gene-deficient background, thymocytes bypassed the block at the CD25+CD44- DN stage and matured to the immature CD8 single-positive (ISP) cell stage, but not further to the CD4/CD8 double-positive (DP) cell stage. When these mice were irradiated, thymocytes did develop to the DP stage, suggesting transcriptional induction of additional genes by irradiation that are required to promote thymocyte development from the ISP to the DP stage. These results provide genetic evidence for two distinct steps during early thymocyte development from the CD25+CD44- DN to the DP stage. The first step, from the CD25+CD44- DN to the ISP stage, can be entirely promoted by overexpression of Egr-1.

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