Limits...
Delta-like 4 is the essential, nonredundant ligand for Notch1 during thymic T cell lineage commitment.

Koch U, Fiorini E, Benedito R, Besseyrias V, Schuster-Gossler K, Pierres M, Manley NR, Duarte A, Macdonald HR, Radtke F - J. Exp. Med. (2008)

Bottom Line: Although the physiological ligands that interact with N1 expressed on thymic precursors are currently unknown, in vitro culture systems point to Delta-like 1 (DL1) and DL4 as prime candidates.Although loss of DL4 in hematopoietic progenitors did not perturb thymus development, inactivation of DL4 in TECs led to a complete block in T cell development coupled with the ectopic appearance of immature B cells in the thymus.Collectively, our results demonstrate that DL4 is the essential and nonredundant N1 ligand responsible for T cell lineage commitment.

View Article: PubMed Central - PubMed

Affiliation: Ecole Polytechnique Fédérale de Lausanne, Swiss Institute for Experimental Cancer Research, 1066 Epalinges, Switzerland.

ABSTRACT
Thymic T cell lineage commitment is dependent on Notch1 (N1) receptor-mediated signaling. Although the physiological ligands that interact with N1 expressed on thymic precursors are currently unknown, in vitro culture systems point to Delta-like 1 (DL1) and DL4 as prime candidates. Using DL1- and DL4-lacZ reporter knock-in mice and novel monoclonal antibodies to DL1 and DL4, we show that DL4 is expressed on thymic epithelial cells (TECs), whereas DL1 is not detected. The function of DL4 was further explored in vivo by generating mice in which DL4 could be specifically inactivated in TECs or in hematopoietic progenitors. Although loss of DL4 in hematopoietic progenitors did not perturb thymus development, inactivation of DL4 in TECs led to a complete block in T cell development coupled with the ectopic appearance of immature B cells in the thymus. These immature B cells were phenotypically indistinguishable from those developing in the thymus of conditional N1 mutant mice. Collectively, our results demonstrate that DL4 is the essential and nonredundant N1 ligand responsible for T cell lineage commitment. Moreover, they strongly suggest that N1-expressing thymic progenitors interact with DL4-expressing TECs to suppress B lineage potential and to induce the first steps of intrathymic T cell development.

Show MeSH

Related in: MedlinePlus

Comparative phenotypic analysis of B cells within thymi of DL4ΔFoxn1 and N1ΔMx mice. (A) Representative flow cytometric analysis of B cells in the DN thymus compartment from Ctrl, N1ΔMx, and DL4ΔFoxn1 mice stained for B220 and IgM (top) or BP1 and CD93 (bottom). B220/IgM staining is electronically gated on lineage-negative CD44+CD25− cells, whereas BP1/CD93 staining is gated on lineage-negative B220+ cells. (left) A comparative analysis of normal BM B cells to highlight the phenotypic similarity. Percentages of populations staining positively for the indicated markers are shown in the contour plots. (B) Bar graphs show the absolute numbers ± SD of immature (B220+IgM−) B cells per thymus derived from Ctrl, Notch1ΔMx, and DL4ΔFoxn1 mice (n = 6 mice per sample group). Note the logarithmic scale. All mice used were between 2–3 wk old, and data are representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2571927&req=5

fig4: Comparative phenotypic analysis of B cells within thymi of DL4ΔFoxn1 and N1ΔMx mice. (A) Representative flow cytometric analysis of B cells in the DN thymus compartment from Ctrl, N1ΔMx, and DL4ΔFoxn1 mice stained for B220 and IgM (top) or BP1 and CD93 (bottom). B220/IgM staining is electronically gated on lineage-negative CD44+CD25− cells, whereas BP1/CD93 staining is gated on lineage-negative B220+ cells. (left) A comparative analysis of normal BM B cells to highlight the phenotypic similarity. Percentages of populations staining positively for the indicated markers are shown in the contour plots. (B) Bar graphs show the absolute numbers ± SD of immature (B220+IgM−) B cells per thymus derived from Ctrl, Notch1ΔMx, and DL4ΔFoxn1 mice (n = 6 mice per sample group). Note the logarithmic scale. All mice used were between 2–3 wk old, and data are representative of three independent experiments.

Mentions: A small number of thymic B cells are present in Ctrl mice, and the majority have a mature IgM+B220+ phenotype. In contrast, a much larger population of B cells was found in DL4ΔFoxn1 and N1ΔMx mice, and these B cells express heterogeneous levels of IgM and B220. Moreover, DL4ΔFoxn1 and N1ΔMx B cells also express CD93 and BP1, which are typical markers for immature B cells, normally only present in the BM (Fig. 4 A). All B220+IgM− cells within the thymi of DL4ΔFoxn1 and N1ΔMx mice were CD19+, confirming that these are indeed immature B cells (unpublished data). In absolute numbers, immature thymic B cells were increased 340- and 30-fold over Ctrl values in DL4ΔFoxn1 and N1ΔMx mice, respectively (Fig. 4 B). In conclusion, the immature B cell phenotype observed in the thymi of N1ΔMx mice is largely recapitulated in DL4ΔFoxn1 mice, strongly suggesting that DL4 is the natural ligand for N1 during thymic T cell lineage commitment.


Delta-like 4 is the essential, nonredundant ligand for Notch1 during thymic T cell lineage commitment.

Koch U, Fiorini E, Benedito R, Besseyrias V, Schuster-Gossler K, Pierres M, Manley NR, Duarte A, Macdonald HR, Radtke F - J. Exp. Med. (2008)

Comparative phenotypic analysis of B cells within thymi of DL4ΔFoxn1 and N1ΔMx mice. (A) Representative flow cytometric analysis of B cells in the DN thymus compartment from Ctrl, N1ΔMx, and DL4ΔFoxn1 mice stained for B220 and IgM (top) or BP1 and CD93 (bottom). B220/IgM staining is electronically gated on lineage-negative CD44+CD25− cells, whereas BP1/CD93 staining is gated on lineage-negative B220+ cells. (left) A comparative analysis of normal BM B cells to highlight the phenotypic similarity. Percentages of populations staining positively for the indicated markers are shown in the contour plots. (B) Bar graphs show the absolute numbers ± SD of immature (B220+IgM−) B cells per thymus derived from Ctrl, Notch1ΔMx, and DL4ΔFoxn1 mice (n = 6 mice per sample group). Note the logarithmic scale. All mice used were between 2–3 wk old, and data are representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2571927&req=5

fig4: Comparative phenotypic analysis of B cells within thymi of DL4ΔFoxn1 and N1ΔMx mice. (A) Representative flow cytometric analysis of B cells in the DN thymus compartment from Ctrl, N1ΔMx, and DL4ΔFoxn1 mice stained for B220 and IgM (top) or BP1 and CD93 (bottom). B220/IgM staining is electronically gated on lineage-negative CD44+CD25− cells, whereas BP1/CD93 staining is gated on lineage-negative B220+ cells. (left) A comparative analysis of normal BM B cells to highlight the phenotypic similarity. Percentages of populations staining positively for the indicated markers are shown in the contour plots. (B) Bar graphs show the absolute numbers ± SD of immature (B220+IgM−) B cells per thymus derived from Ctrl, Notch1ΔMx, and DL4ΔFoxn1 mice (n = 6 mice per sample group). Note the logarithmic scale. All mice used were between 2–3 wk old, and data are representative of three independent experiments.
Mentions: A small number of thymic B cells are present in Ctrl mice, and the majority have a mature IgM+B220+ phenotype. In contrast, a much larger population of B cells was found in DL4ΔFoxn1 and N1ΔMx mice, and these B cells express heterogeneous levels of IgM and B220. Moreover, DL4ΔFoxn1 and N1ΔMx B cells also express CD93 and BP1, which are typical markers for immature B cells, normally only present in the BM (Fig. 4 A). All B220+IgM− cells within the thymi of DL4ΔFoxn1 and N1ΔMx mice were CD19+, confirming that these are indeed immature B cells (unpublished data). In absolute numbers, immature thymic B cells were increased 340- and 30-fold over Ctrl values in DL4ΔFoxn1 and N1ΔMx mice, respectively (Fig. 4 B). In conclusion, the immature B cell phenotype observed in the thymi of N1ΔMx mice is largely recapitulated in DL4ΔFoxn1 mice, strongly suggesting that DL4 is the natural ligand for N1 during thymic T cell lineage commitment.

Bottom Line: Although the physiological ligands that interact with N1 expressed on thymic precursors are currently unknown, in vitro culture systems point to Delta-like 1 (DL1) and DL4 as prime candidates.Although loss of DL4 in hematopoietic progenitors did not perturb thymus development, inactivation of DL4 in TECs led to a complete block in T cell development coupled with the ectopic appearance of immature B cells in the thymus.Collectively, our results demonstrate that DL4 is the essential and nonredundant N1 ligand responsible for T cell lineage commitment.

View Article: PubMed Central - PubMed

Affiliation: Ecole Polytechnique Fédérale de Lausanne, Swiss Institute for Experimental Cancer Research, 1066 Epalinges, Switzerland.

ABSTRACT
Thymic T cell lineage commitment is dependent on Notch1 (N1) receptor-mediated signaling. Although the physiological ligands that interact with N1 expressed on thymic precursors are currently unknown, in vitro culture systems point to Delta-like 1 (DL1) and DL4 as prime candidates. Using DL1- and DL4-lacZ reporter knock-in mice and novel monoclonal antibodies to DL1 and DL4, we show that DL4 is expressed on thymic epithelial cells (TECs), whereas DL1 is not detected. The function of DL4 was further explored in vivo by generating mice in which DL4 could be specifically inactivated in TECs or in hematopoietic progenitors. Although loss of DL4 in hematopoietic progenitors did not perturb thymus development, inactivation of DL4 in TECs led to a complete block in T cell development coupled with the ectopic appearance of immature B cells in the thymus. These immature B cells were phenotypically indistinguishable from those developing in the thymus of conditional N1 mutant mice. Collectively, our results demonstrate that DL4 is the essential and nonredundant N1 ligand responsible for T cell lineage commitment. Moreover, they strongly suggest that N1-expressing thymic progenitors interact with DL4-expressing TECs to suppress B lineage potential and to induce the first steps of intrathymic T cell development.

Show MeSH
Related in: MedlinePlus