Education and Training:

B.S., Biochemistry, Illinois Benedictine College, Lisle, IL (1992)

M.S., Chemistry, Southern Illinois University, Carbondale, IL (1995)

Research Associate, Department of Pediatrics, Northwestern University Medical School, Chicago, IL (1995-97)

Ph.D., Molecular Genetics, University of Vermont, Burlington, VT (2001)

Postdoctoral Fellow, Puget Sound Blood Center/University of Washington, Seattle, WA (2001-05)

Current Research Interests
Hematopoitic stem cell biology, megakaryocyte differentiation, Mpl signaling mechanism

Research Description
My research is focused on interrelated projects pertinent to the signaling mechanisms involved in the development, proliferation, and function of bone marrow cells. The long-term objectives are to gain an understanding of the molecular events controlling cellular development by studying the genetic and signaling factors that control lineage commitment and the regulation of cell cycle during this process.

More specifically, my current laboratory interests fall into three main categories. 1) The role of Src family kinases (SFKs) in megakaryocyte differentiation and development, 2) identifying key elements of molecular regulation of cell cycle control, 3) understanding the role that thrombopoietin (TPO) and its receptor (Mpl) plays in regulation and development of hematopoietic stem cells (HSCs). Megakaryocytes (MK) arise in the bone marrow and produce platelets, the cells that mediate primary hemostasis. Precise regulation of platelet production is critical over the life of an organism and can be abnormal during disease states. The TPO/Mpl signaling pathway is essential both for optimal growth of hematopoietic progenitors and megakaryocytopoiesis. MKs undergo successive rounds of endomitosis during differentiation, resulting in polyploidy (typically, 16-64N). Previous studies have demonstrated that this occurs through an interruption of normal cell cycle progression during anaphase. However, the molecular mechanism(s) controlling this unique process is undefined. We have shown that Mpl stimulation results in the activation of SFKs, specifically Fyn and Lyn in primary MKs, and that inhibition of these kinases results in enhanced proliferation and differentiation. In vivo studies on Lyn-deficient mice revealed an increase in CD41/Mpl-positive cells, colony-forming unit-MKs, and a greater number of mature MKs with increased nuclear ploidy when compared to their wild-type littermates. TPO treatment of Lyn-deficient MKs showed a significant increase in intensity and duration of Erk1/2 and Akt activity. In contrast, there was a reduction of tyrosine phosphorylation of the inositol phosphatase, SHIP. Future directions are geared towards understanding how Fyn and Lyn mediate these phenotypic effects. The aims to be addressed include: 1) analyze the phenotype of MKs and marrow progenitors in lyn-deficient, fyn-deficient, and lyn/fyn double-knockout mice; 2) determine whether or not the effect of SFKs is primarily mediated through modifying MAPK activity and identify the mechanism(s) through which SFKs inhibit Erk1/2 activity; and 3) investigate the role of Lyn activation in regulating SHIP-1 to determine how convergent signaling pathways affect SFKs and Erk1/2 activity during normal and abnormal megakaryocytopoiesis.

A second area of active study is identifying key elements of molecular regulation of MK cell cycle regulation and terminal differentiation. We have shown that hematopoietic cell lines and primary cells become highly polyploid and undergo spontaneous fragmentation in the presence of rhTPO and the specific Src kinase inhibitor, SU6656. This was accompanied by cessation of cellular proliferation, increase in CD41 and CD61 expression, and was notable for the absence of apoptosis. The ability to induce differentiation was also seen using bone marrow from patients with myelodysplastic syndrome and thrombocytopenia, suggesting that SU6656 might be useful as a differentiation-inducing agent for MKs. To begin understanding the molecular basis for these effects we have focus on the changes in cell cycle regulatory proteins during terminal differentiation. We will examine changes in expression and activity of critical cell cycle regulators (cyclins, cyclin-dependent kinases, cyclin-dependent kinase inhibitors, and checkpoint proteins such as p53 and Rb) in response to TPO and SU6656. We propose that SU6656 may be an important tool for understanding the molecular basis of MK endomitosis and may also have therapeutic potential for individuals with MDS, thrombocytopenia, or other disorders resulting from incomplete megakaryocyte maturation.

Finally, we are also trying to understand the role that TPO and its receptor, Mpl, plays in the function of HSCs.  In addition to being the primary physiological regulator of platelet production, TPO is also an important cytokine during early hematopoiesis. TPO/Mpl supports the survival, expansion, and maintenance of HSC numbers. To further define the role of TPO/Mpl in early hematopoiesis, we are currently using mutant Mpl receptors to study the pathways by which the cytokine signals proliferation and differentiation, and confirming in vitro results using knockout and transgenic technologies (Knockin mice).

These studies will lead to a better understanding of the molecular and cellular biology of HSCs and ultimately contribute to clinical strategies for ex vivo expansion and maintenance of HSCs.

Selected Publications

Lannutti BJ. Shim MH, Blake N, Reems JA, Drachman JG.  Identification and activation of Src family kinases in primary megakaryocytes. Exp. Hematol. 31(12):1268-74, 2003.

Lannutti BJ. and Drachman JG.  Lyn tyrosine kinase regulates thrombopoietin-induced proliferation of hematopoietic cell lines and primary megakaryocytic progenitors. Blood 103(10):3736-43, 2004.

Lannutti BJ, Blake N., Gandhi MJ, Reems JA, Drachman JG.  Induction of polyploidization in leukemic cell lines and primary bone marrow by Src kinase inhibitor SU6656. Blood 105(10):3875-8, 2005.

Gandhi MJ, Drachman JG, Reems JA, Thorning D, Lannutti, BJ.  A novel strategy for generating platelet-like fragments from megakaryocytic cell lines and human progenitor cells. Blood Cells Mol. Dis. 35(1):70-3, 2005.

Lannutti BJ, Minear J, Blake N, Drachman JG.  Increased megakaryocytopoiesis in Lyn-deficient mice. Oncogene 25(23):3316-24, 2006.

Dillon M, Miner J, Johnson HJ, Lannutti B.  Expression of the GPI-anchored receptor PRV-1 enhances thrombopoietin and IL-3 induced proliferation.  Leuk. Res. In Press. 2008.