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Identification of essential genes in human lymphopoieis

Inge Hoebeke (UGent)
(2006)
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Abstract
Hematopoiesis is the highly orchestrated process of blood cell formation from a small pool of multipotent hematopoietic stem cells in the bone marrow. The defining properties of hematopoietic stem cells, their self-renewal capacity and multilineage differentiation potential, form the basis for the successful restoration of the hematopoietic system by bone marrow transplantation or hematopoietic stem cell transplantation after chemotherapy or radiation therapy used to treat cancer. However, due to the slow kinetics of the restoration of the T-cell compartment, patients are temporally vulnerable to infection. Therefore, strategies to enhance T-cell development from HSCs could be of great therapeutic value. Signalling through the Notch-1 transmembrane receptor has been identified as a critical determinant for the lineage choice between B- and T-cell development. Overexpression of the active form of Notch-1 (ICN) in human CD34+ hematopoietic stem cells blocks B-cell development and drives them into T-lymphoid differentiation. In this work we show that physiological stimulation of the Notch pathway by coculturing human CD34+ progenitor cells on a stromal cell layer ectopically expressing the Notch ligand Delta-like-1 also induces T-cell differentiation of human cells. Inversely, by inhibiting physiological Notch signalling during in vitro T-cell differentiation in fetal thymus organ culture using γ- secretase inhibitors we show that Notch signalling is essential for human T-cell development. Because constitutive Notch-1 expression ultimately leads to the development of T-cell leukemias, manipulation of stem cells with ICN cannot be applied clinically. Therefore we investigated whether the Notch-1 target gene HES-1 is able to substitute for Notch-1 signalling in inducing T-cell differentiation of human CD34+ hematopoietic stem cells. Our results demonstrate that overexpression of HES-1 alone is not sufficient to impose T-cell differentiation on human hematopoietic stem cells. The identification of a small lymphoid-committed cell fraction in human umbilical cord blood may also lead to therapeutic applications. We show that CD34+CD38-CD7+ cells have strong T-cell differentiation potential. To identify genes that regulate the lymphoid commitment step we compared the gene expression between CD34+CD38-CD7+ lymphoidcommitted progenitors and CD34+CD38-CD7- multipotent stem cells using Affymetrix oligonucleotide microarrays. Overexpression and silencing studies of selected differentially expressed genes will have to be performed to determine their role in lymphoid development and whether they can be used to instruct lymphoid development.

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Citation

Please use this url to cite or link to this publication:

Chicago
Hoebeke, Inge. 2006. “Identification of Essential Genes in Human Lymphopoieis”. Ghent, Belgium: Ghent University. Faculty of Medicine and Health Sciences.
APA
Hoebeke, I. (2006). Identification of essential genes in human lymphopoieis. Ghent University. Faculty of Medicine and Health Sciences, Ghent, Belgium.
Vancouver
1.
Hoebeke I. Identification of essential genes in human lymphopoieis. [Ghent, Belgium]: Ghent University. Faculty of Medicine and Health Sciences; 2006.
MLA
Hoebeke, Inge. “Identification of Essential Genes in Human Lymphopoieis.” 2006 : n. pag. Print.
@phdthesis{3127826,
  abstract     = {Hematopoiesis is the highly orchestrated process of blood cell formation from a small pool of multipotent hematopoietic stem cells in the bone marrow. The defining properties of hematopoietic stem cells, their self-renewal capacity and multilineage differentiation potential, form the basis for the successful restoration of the hematopoietic system by bone marrow transplantation or hematopoietic stem cell transplantation after chemotherapy or radiation therapy used to treat cancer. However, due to the slow kinetics of the restoration of the T-cell compartment, patients are temporally vulnerable to infection. Therefore, strategies to enhance T-cell development from HSCs could be of great therapeutic value. Signalling through the Notch-1 transmembrane receptor has been identified as a critical determinant for the lineage choice between B- and T-cell development. Overexpression of the active form of Notch-1 (ICN) in human CD34+ hematopoietic stem cells blocks B-cell development and drives them into T-lymphoid differentiation. In this work we show that physiological stimulation of the Notch pathway by coculturing human CD34+ progenitor cells on a stromal cell layer ectopically expressing the Notch ligand Delta-like-1 also induces T-cell differentiation of human cells. Inversely, by inhibiting physiological Notch signalling during in vitro T-cell differentiation in fetal thymus organ culture using \ensuremath{\gamma}-
secretase inhibitors we show that Notch signalling is essential for human T-cell development. Because constitutive Notch-1 expression ultimately leads to the development of T-cell leukemias, manipulation of stem cells with ICN cannot be applied clinically. Therefore we investigated whether the Notch-1 target gene HES-1 is able to substitute for Notch-1 signalling in inducing T-cell differentiation of human CD34+ hematopoietic stem cells. Our results demonstrate that overexpression of HES-1 alone is not sufficient to impose T-cell differentiation on human hematopoietic stem cells. The identification of a small lymphoid-committed cell fraction in human umbilical cord blood may also lead to therapeutic applications. We show that CD34+CD38-CD7+ cells have strong T-cell differentiation potential. To identify genes that regulate the lymphoid commitment step we compared the gene expression between CD34+CD38-CD7+ lymphoidcommitted progenitors and CD34+CD38-CD7- multipotent stem cells using Affymetrix oligonucleotide microarrays. Overexpression and silencing studies of selected differentially expressed genes will have to be performed to determine their role in lymphoid development and whether they can be used to instruct lymphoid development.},
  author       = {Hoebeke, Inge},
  language     = {eng},
  pages        = {144},
  publisher    = {Ghent University. Faculty of Medicine and Health Sciences},
  school       = {Ghent University},
  title        = {Identification of essential genes in human lymphopoieis},
  year         = {2006},
}