Hematopoietic stem cells (HSC) can self-renew and give rise to all the cells of the blood and the immune system through successive stages of progenitor cells that are progressively more restricted in their lineage potential. Although a multitude of cytokines that affect HSC are known, the exact mechanisms that regulate self renewal, differentiation and quiescence as well as homeostatic responses of the hematopoietic stem and progenitor cell (HSPC) compartment are not well understood. As hematopoiesis shows extensive mouse strain-dependent, genetically determined variation, elucidation of the mechanisms underlying this variation may be powerful approach to dissect the multiple pathways involved in the regulation of self-renewal, differentiation and proliferation of HSPCs. The goal of the proposal for the first funding period of this grant was to elucidate the mechanisms underlying quantitative genetic variation in the function and size of the HSC compartment. The hypothesis was that transforming growth factor-beta2 (TGF-b2) played a critical role in this process, and that at least one quantitative trait locus (QTL) was located in the telomeric region of chr. 4 and regulated the function of HSPCs through its effect on TGF-b2 signaling. During this funding period we have shown that TGF-b2 is a positive regulator of the responsiveness of HSPCs to the cytokine, Flt3 ligand (Flt3L), an effect that is not shared by other TGF-b isoforms, which have only antiproliferative effects. TGF-b2 requires the presence of serum factors, which ultimately switches the biological effect of TGF-b2 from generic inhibition of proliferation to specific enhancement of Flt3L responsiveness. Both the activity of these serum factors, and the responsiveness of HSCPs to the combined effect of serum and TGF-b2 increase with age. Furthermore, a strong QTL in the telomeric region of chr.4, Tb2r1, regulates the activity of this regulatory mechanism. We identified a most likely candidate gene for this QTL, and, through this observation, could elucidate the nature of the serum factors involved. These findings have obvious implications for acute myeloblastic leukemia, as in up to 30 % of cases;a constitutively active Flt3 receptor plays a role in pathogenesis. Furthermore, TGF-b2 may be an important and genetically regulated determinant of the toxicity of cell cycle-specific chemotherapeutic agents in humans. The goal of this competitive renewal is one, to examine the function of the gene underlying Tb2r1, two, to define the physiological and potential biomedical significance of TGF-b2 signaling in HSPCs, and three, to elucidate the molecular mechanisms underlying the interaction between serum factors, TGF- b2, and Flt3L.

Public Health Relevance

We propose to investigate a novel mechanism that regulates hematopoietic stem and progenitor cells, and more specifically responsiveness to the cytokine Flt3 ligand. This work will have important implications for acute myeloblastic leukemia, as in up to 30 % of cases;a constitutively active Flt3 receptor plays a role in pathogenesis. Furthermore, this mechanism is subject to genetically determined variation, suggesting that this work may lead to novel and important insights into the toxicity of cell cycle-specific chemotherapeutic agents and the susceptibility to hematological disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
7R01HL073760-07
Application #
8258761
Study Section
Hematopoiesis Study Section (HP)
Program Officer
Thomas, John
Project Start
2003-07-01
Project End
2014-04-30
Budget Start
2012-05-15
Budget End
2013-04-30
Support Year
7
Fiscal Year
2012
Total Cost
$396,000
Indirect Cost
$148,500
Name
Columbia University (N.Y.)
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
Kamezaki, Kenjiro; Luchsinger, Larry L; Snoeck, Hans-Willem (2014) Differential requirement for wild-type Flt3 in leukemia initiation among mouse models of human leukemia. Exp Hematol 42:192-203.e1
Avagyan, Serine; Aguilo, Francesca; Kamezaki, Kenjiro et al. (2011) Quantitative trait mapping reveals a regulatory axis involving peroxisome proliferator-activated receptors, PRDM16, transforming growth factor-*2 and FLT3 in hematopoiesis. Blood 118:6078-86
Aguilo, Francesca; Avagyan, Serine; Labar, Amy et al. (2011) Prdm16 is a physiologic regulator of hematopoietic stem cells. Blood 117:5057-66
Kumar, Ritu; Avagyan, Serine; Snoeck, Hans-Willem (2010) A quantitative trait locus on chr.4 regulates thymic involution. J Gerontol A Biol Sci Med Sci 65:620-5
Avagyan, Serine; Glouchkova, Ludmila; Choi, Juhyun et al. (2008) A quantitative trait locus on chromosome 4 affects cycling of hematopoietic stem and progenitor cells through regulation of TGF-beta 2 responsiveness. J Immunol 181:5904-11
Langer, Jessica C; Kumar, Ritu; Snoeck, Hans-Willem (2006) Age-related accumulation of a novel CD44 + CD25lowgammadelta T-cell population in hematopoietic organs of the mouse. J Gerontol A Biol Sci Med Sci 61:568-71
Kumar, Ritu; Langer, Jessica C; Snoeck, Hans-Willem (2006) Transforming growth factor-beta2 is involved in quantitative genetic variation in thymic involution. Blood 107:1974-9
Henckaerts, Els; Langer, Jessica C; Orenstein, Jonathan et al. (2004) The positive regulatory effect of TGF-beta2 on primitive murine hemopoietic stem and progenitor cells is dependent on age, genetic background, and serum factors. J Immunol 173:2486-93