Pilot Project Grant Program Awardees

2007-2008 Pilot and Feasibility Grant Winners

• Richard Flavell, Ph.D.
  Professor and Chairman of Immunobiology
  HHMI Investigator
  Role of c-Cbl in the regulation of hematopoietic stem cell self renewal and function
• Zhong Yun, Ph.D.
  Assistant Professor of Therapeutic Radiology
  Hypoxia and Hematopoietic Stem Cells
• Michael Hodsdon, M.D., Ph.D.
  Associate Professor of Laboratory Medicine and Pharmacology
  Cytokine-Glycosaminoglycan Interactions in Hematopoiesis

2007-2008 WINNERS' ABSTRACTS

Richard Flavell, Ph.D.
Professor and Chairman of Immunobiology
HHMI Investigator

Role of c-Cbl in the regulation of hematopoietic stem cell self renewal and function
Hematopietic stem cells (HSCs) are multipotent progenitors that give rise to all types of blood cells. HSCs have the ability to strike a balance between self-renewal and lineage commitment. Even though the phenotypic and functional properties of HSCs have been extensively characterized, molecular machinery that governs self-renewal of HSCs remains largely unknown. In the proposed project, we aim to dissect the role of an E3 ubiquitin ligase- c-Cbl in controlling the self renewal of HSCs.

Our initial studies will be focused on characterizing the HSC compartment in the bone marrow of c-Cbl deficient mice. Next, we will assessth e function of c-Cbl deficient HSCs through competitive repopulation and serial transplantation experiments. In addltiono the capacity of c-Cbl deficient HSCs to differentiate into various hematopoietic lineages will be evaluated through in vitro and in vivo differentiation experiments. Finally, we would focus on understanding the molecular mechanisms through which c-Cbl might regulate the development and function of HSCs.

In summary the proposed project might provide valuable insights into the ubiquitin mediated control of HSC self renewal. A better understanding on the roles played by c-Cbl in cytokine signaling might be useful for manipulating stem cells for tissue engineering and cell based therapies.

Zhong Yun, Ph.D.
Assistant Professor of Therapeutic Radiology

Hypoxia and Hematopoietic Stem Cells
Recent studies have shown that bone marrow contains areas of low pO2 and hematopoietic stem cells (HSCs) appear to be hypoxic. However, it is not clear how O2 regulates the maintenance and differentiation of HSCs. We hypothesize that hypoxia provides an optimal microenvironment for the maintenance of HSCs by stromal cells and the hypoxia-inductible factor-1 (HIF-1) constitutes an important mechanism. In this proposal, we will test the following two working hypotheses: 1) hypoxia facilitates HSC maintenance by regulating both stromal cells and HSCs and 2) the hypoxia-sensing pathway plays a critical role in HSC homing to the bone marrow. Our proposal represents a new direction in HSC research with the potential to provide novel mechanistic insight into the role of niche microenvironment in the regulation of HSC functions. This interdisciplinary research will be conducted in collaboration with Dr. Diane Krause, an expert of molecular hematology at Yale University School of Medicine. Findings of our research could lead to significant improvement for long term ex vivo growth and maintenance of HSCs, and thus could facilitate the use of HSCs in stem cell therapies for cancers and other genetic diseases.

Michael Hodsdon, M.D., Ph.D.
Associate Professor of Laboratory Medicine and Pharmacology

Cytokine-Glycosaminoglycan Interactions in Hematopoiesis
The overall goal of this long term project is to describe the molecular mechanisms by which glycosaminoglycans (GAGs) both support and modulate the biologic function of the hematopoietic cytokines. GAGs are known to play an important functional role in maintenance of the hematopoietic stem cell niche and also in the support and regulation of hematopoiesis. In two other classes of cytoknes, chemokines and the fibroblast growth factors, direct interactions with GAGs contribute critically to their function. Our primary hypothesis is that GAGs bind directly to specific cytokines involved in hematopoiesis in a selective and structurally-specific manner. Initially, we will screen twelve hematopoietic cytokines for direct and selective binding to heparin, a soluble GAG. Subsequently, using recombinantly expressed protein and purified heparin oligosaccharides, we will both confirm and further characterize site-specific binding interactions identified in the screening experiment. Identification of hematopoietic cytokines that bind directly and selectively to GAGs will allow the generation of hypotheses on the role of GAG-cytokine interactions in hematopoiesis and will guide future studies on the structural basis of GAG recognition and its biological role.