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Thymocyte maturation is regulated by the activity of the helix-loop-helix protein, E47.

Bain G, Quong MW, Soloff RS, Hedrick SM, Murre C - J. Exp. Med. (1999)

Bottom Line: Additionally, development of CD8 lineage T cells in an MHC class I-restricted TCR transgenic background is sensitive to the dosage of E47.Mice deficient for E47 display an increase in production of mature CD4 and CD8 lineage T cells.Furthermore, ectopic expression of an E2A inhibitor helix-loop-helix protein, Id3, promotes the in vitro differentiation of an immature T cell line.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093, USA.

ABSTRACT
The E2A proteins, E12 and E47, are required for progression through multiple developmental pathways, including early B and T lymphopoiesis. Here, we provide in vitro and in vivo evidence demonstrating that E47 activity regulates double-positive thymocyte maturation. In the absence of E47 activity, positive selection of both major histocompatibility complex (MHC) class I- and class II-restricted T cell receptors (TCRs) is perturbed. Additionally, development of CD8 lineage T cells in an MHC class I-restricted TCR transgenic background is sensitive to the dosage of E47. Mice deficient for E47 display an increase in production of mature CD4 and CD8 lineage T cells. Furthermore, ectopic expression of an E2A inhibitor helix-loop-helix protein, Id3, promotes the in vitro differentiation of an immature T cell line. These results demonstrate that E2A functions as a regulator of thymocyte positive selection.

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Increased rate of appearance of mature thymocytes in mice deficient for E47. Mice were continuously exposed to the thymidine analogue BrdU in their drinking water for the indicated times and then analyzed for BrdU content and TCR-α/β and CD69 surface expression. (A) Representative TCR-α/β/CD69 FACS® plots for E47-deficient and heterozygous mice. (B) Rate of appearance of BrdU-labeled TCRmed CD69+ cells (left) and TCRhiCD69− cells (right). The percent BrdU-labeled cells of total cells is plotted against the time of continuous exposure to BrdU. The gates used to define the TCRmedCD69+ cells and TCRhiCD69− cells are shown in A as R1 and R2, respectively. The numbers plotted are the averages from two mice.
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Figure 7: Increased rate of appearance of mature thymocytes in mice deficient for E47. Mice were continuously exposed to the thymidine analogue BrdU in their drinking water for the indicated times and then analyzed for BrdU content and TCR-α/β and CD69 surface expression. (A) Representative TCR-α/β/CD69 FACS® plots for E47-deficient and heterozygous mice. (B) Rate of appearance of BrdU-labeled TCRmed CD69+ cells (left) and TCRhiCD69− cells (right). The percent BrdU-labeled cells of total cells is plotted against the time of continuous exposure to BrdU. The gates used to define the TCRmedCD69+ cells and TCRhiCD69− cells are shown in A as R1 and R2, respectively. The numbers plotted are the averages from two mice.

Mentions: The steady state size of the thymic subpopulations is determined by the rate at which cells are generated, the rate at which they die, and the rate at which they emigrate from the thymus. To more directly assess the effect of an E47 deficiency on the production of mature SP T cells, we measured the kinetics of appearance of mature thymocytes using the thymidine analogue BrdU. We exposed E47-deficient mice and their heterozygous littermates to BrdU in their drinking water and then analyzed for the presence of BrdU and the expression of TCR-α/β and CD69 (Fig. 7A and Fig. B). Because cells expressing medium to high levels of TCR are not dividing, there is a lag in the appearance of BrdU in these populations. As described above, both the E47-deficient and control mice display this lag in labeling of mature thymocytes, demonstrating that the absence of E47 does not lead to the aberrant proliferation of the SP cells. Because the TCRmed-hi populations are nondividing, the rate of appearance of BrdU in these populations reflects the rate at which these cells are produced. In mice deficient for E47, the rate of appearance of BrdU-labeled TCRhiCD69− mature thymocytes is significantly enhanced, suggesting that the relative proportion of cells that develop into mature CD69− T cells is increased in the absence of E47 (Fig. 7 B). In contrast, E47-deficient mice display a decrease in the rate of appearance of BrdU in the TCRmed CD69+ population (Fig. 7 B). Taken together, these data suggest that the rate at which DP thymocytes mature into TCRhiCD69− SP T cells is enhanced in the absence of E47.


Thymocyte maturation is regulated by the activity of the helix-loop-helix protein, E47.

Bain G, Quong MW, Soloff RS, Hedrick SM, Murre C - J. Exp. Med. (1999)

Increased rate of appearance of mature thymocytes in mice deficient for E47. Mice were continuously exposed to the thymidine analogue BrdU in their drinking water for the indicated times and then analyzed for BrdU content and TCR-α/β and CD69 surface expression. (A) Representative TCR-α/β/CD69 FACS® plots for E47-deficient and heterozygous mice. (B) Rate of appearance of BrdU-labeled TCRmed CD69+ cells (left) and TCRhiCD69− cells (right). The percent BrdU-labeled cells of total cells is plotted against the time of continuous exposure to BrdU. The gates used to define the TCRmedCD69+ cells and TCRhiCD69− cells are shown in A as R1 and R2, respectively. The numbers plotted are the averages from two mice.
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Related In: Results  -  Collection

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Figure 7: Increased rate of appearance of mature thymocytes in mice deficient for E47. Mice were continuously exposed to the thymidine analogue BrdU in their drinking water for the indicated times and then analyzed for BrdU content and TCR-α/β and CD69 surface expression. (A) Representative TCR-α/β/CD69 FACS® plots for E47-deficient and heterozygous mice. (B) Rate of appearance of BrdU-labeled TCRmed CD69+ cells (left) and TCRhiCD69− cells (right). The percent BrdU-labeled cells of total cells is plotted against the time of continuous exposure to BrdU. The gates used to define the TCRmedCD69+ cells and TCRhiCD69− cells are shown in A as R1 and R2, respectively. The numbers plotted are the averages from two mice.
Mentions: The steady state size of the thymic subpopulations is determined by the rate at which cells are generated, the rate at which they die, and the rate at which they emigrate from the thymus. To more directly assess the effect of an E47 deficiency on the production of mature SP T cells, we measured the kinetics of appearance of mature thymocytes using the thymidine analogue BrdU. We exposed E47-deficient mice and their heterozygous littermates to BrdU in their drinking water and then analyzed for the presence of BrdU and the expression of TCR-α/β and CD69 (Fig. 7A and Fig. B). Because cells expressing medium to high levels of TCR are not dividing, there is a lag in the appearance of BrdU in these populations. As described above, both the E47-deficient and control mice display this lag in labeling of mature thymocytes, demonstrating that the absence of E47 does not lead to the aberrant proliferation of the SP cells. Because the TCRmed-hi populations are nondividing, the rate of appearance of BrdU in these populations reflects the rate at which these cells are produced. In mice deficient for E47, the rate of appearance of BrdU-labeled TCRhiCD69− mature thymocytes is significantly enhanced, suggesting that the relative proportion of cells that develop into mature CD69− T cells is increased in the absence of E47 (Fig. 7 B). In contrast, E47-deficient mice display a decrease in the rate of appearance of BrdU in the TCRmed CD69+ population (Fig. 7 B). Taken together, these data suggest that the rate at which DP thymocytes mature into TCRhiCD69− SP T cells is enhanced in the absence of E47.

Bottom Line: Additionally, development of CD8 lineage T cells in an MHC class I-restricted TCR transgenic background is sensitive to the dosage of E47.Mice deficient for E47 display an increase in production of mature CD4 and CD8 lineage T cells.Furthermore, ectopic expression of an E2A inhibitor helix-loop-helix protein, Id3, promotes the in vitro differentiation of an immature T cell line.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093, USA.

ABSTRACT
The E2A proteins, E12 and E47, are required for progression through multiple developmental pathways, including early B and T lymphopoiesis. Here, we provide in vitro and in vivo evidence demonstrating that E47 activity regulates double-positive thymocyte maturation. In the absence of E47 activity, positive selection of both major histocompatibility complex (MHC) class I- and class II-restricted T cell receptors (TCRs) is perturbed. Additionally, development of CD8 lineage T cells in an MHC class I-restricted TCR transgenic background is sensitive to the dosage of E47. Mice deficient for E47 display an increase in production of mature CD4 and CD8 lineage T cells. Furthermore, ectopic expression of an E2A inhibitor helix-loop-helix protein, Id3, promotes the in vitro differentiation of an immature T cell line. These results demonstrate that E2A functions as a regulator of thymocyte positive selection.

Show MeSH
Related in: MedlinePlus