The use of hematopoietic stem cells (HSC) in transplant biology and the potential use of these cells, which in the future may be derived by reprogramming methods, in regenerative medicine can be enhanced significantly by improving their engraftment and collection by mobilization. Maintenance of these functions critically depends on the interaction of HSC with one or several specialized microenvironments (so-called niches) in the bone marrow (BM). The crucial intracellular pathways triggered by these interactions are less well characterized, and how they are coordinated to regulate HSC localization relative to different components of the niche and subsequent survival and proliferation is not known. However, dissecting this complexity and defining the functional interactions between GTPases, the guanine exchange factors (GEFs) that activate them and effectors that subserve specific functions in HSC remains a major challenge because GEFs are promiscuous in vitro and effectors are cell and agonist-specific. We have identified the Rac GTPase signaling pathway as a critical integrating component of HSC engraftment and retention. This pathway determines both interaction with the HSC niche via regulation of the cytoskeleton and modulation of proliferation and survival of these cells via kinase pathway activation, potentially providing novel insights into the integration of these broad HSC functions. The long term goal of this work is to further identify a biochemical footprint of HSC marrow homing, retention and engraftment by taking advantage of the genetic models we have developed and validated in the previous funding period. Our central hypothesis is that Rac-dependent HSC regulation of homing/retention in the marrow and reconstitution of hematopoiesis is accomplished by specific functional modules of Vav and Pak proteins that distinctly regulate kinase activation, cell shape changes, and gene expression. This work is based on our latest understanding the role of the Rac signaling axis and development of reagents including mice that has been supported by this grant in the past decade. Our studies will define integral components of the Rac signaling axis that regulate HSC function, providing new knowledge of HSC homing, retention and engraftment as well as identifying new targets for potential therapeutic intervention in these processes. Since modulation of this pathway could improve engraftment of HSCs, lead to more effective mobilization of these cells and to the development of novel therapies in a variety of leukemias these studies are both innovative and translational in nature.

Public Health Relevance

Our studies will define integral components of the Rac signaling axis that regulate hematopoietic stem cell (HSC) function, providing new knowledge of HSC trafficking to the bone marrow space, retention in the marrow and reconstitution of all blood lineages as well as identifying new targets for development of new drugs to enhance these processes. In addition, since abnormal activation of Rac signaling has been demonstrated in several leukemias our studies could define new approaches to the development of novel therapies in a variety of leukemias.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK062757-14
Application #
8885801
Study Section
Molecular and Cellular Hematology Study Section (MCH)
Program Officer
Bishop, Terry Rogers
Project Start
2002-04-01
Project End
2016-06-30
Budget Start
2015-07-01
Budget End
2016-06-30
Support Year
14
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Children's Hospital Boston
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
Alonso-Ferrero, Maria E; van Til, Niek P; Bartolovic, Kerol et al. (2018) Enhancement of mouse hematopoietic stem/progenitor cell function via transient gene delivery using integration-deficient lentiviral vectors. Exp Hematol 57:21-29
De Vita, Serena; Li, Yanhua; Harris, Chad E et al. (2018) The gp130 Cytokine Interleukin-11 Regulates Engraftment of Vav1-/- Hematopoietic Stem and Progenitor Cells in Lethally Irradiated Recipients. Stem Cells 36:446-457
Gavillet, Mathilde; Martinod, Kimberly; Renella, Raffaele et al. (2018) A key role for Rac and Pak signaling in neutrophil extracellular traps (NETs) formation defines a new potential therapeutic target. Am J Hematol 93:269-276
Reddy, Pavankumar N G; Radu, Maria; Xu, Ke et al. (2016) p21-activated kinase 2 regulates HSPC cytoskeleton, migration, and homing via CDC42 activation and interaction with ?-Pix. Blood 127:1967-75
Ciuculescu, Marioara F; Park, Shin-Young; Canty, Kimberly et al. (2015) Perivascular deletion of murine Rac reverses the ratio of marrow arterioles and sinusoid vessels and alters hematopoiesis in vivo. Blood 125:3105-13
Gavillet, Mathilde; Martinod, Kimberly; Renella, Raffaele et al. (2015) Flow cytometric assay for direct quantification of neutrophil extracellular traps in blood samples. Am J Hematol 90:1155-8
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Gordon, P M; Dias, Stuart; Williams, D A (2014) Cytokines secreted by bone marrow stromal cells protect c-KIT mutant AML cells from c-KIT inhibitor-induced apoptosis. Leukemia 28:2257-60
De Vita, Serena; Schneider, Rebekka K; Garcia, Michael et al. (2014) Loss of function of TET2 cooperates with constitutively active KIT in murine and human models of mastocytosis. PLoS One 9:e96209
Keerthivasan, Ganesan; Mei, Yang; Zhao, Baobing et al. (2014) Aberrant overexpression of CD14 on granulocytes sensitizes the innate immune response in mDia1 heterozygous del(5q) MDS. Blood 124:780-90

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