Don M. Wojchowski, Ph.D.

Director, Stem and Progenitor Cell Biology Program
Center for Molecular Medicine
Maine Medical Center Research Institute
Scarborough, ME 04074
(207) 885-8258(phone)
(207) 885-8179 (fax)
WOJCHD@mmc.org

Biosketch

Don Wojchowski is a native of Maine (and greater Portland) who graduated from Colby College; acquired biomedical research training at Boston's Children's Hospital; completed doctoral studies within a cell biology training program at the University of Massachusetts, Amherst; and then pursued postdoctoral studies at Harvard Medical School. Subsequently (from 1987-2003) Dr. Wojchowski served as assistant, associate and full Professor at the Pennsylvania State University (and as Immunobiology Program Director) with a research focus on hematopoiesis. He has served on several NIH study sections and review committees, and is the recipient of several NIH career development awards. In October 2003, Dr. Wojchowski returned to Maine to join investigators at the MMCRI.

Research Interests

My laboratory's broad interests include molecular mechanisms that govern mammalian progenitor cell proliferation, survival and differentiation. Hematopoiesis (blood cell development) serves as a prime model system, and provides an exceptional example of sustained tissue regeneration from a multipotent progenitor pool. This developmental process also is frequently perturbed clinically (leukemias, blood cell disorders, cancer) and provides unique advantages for bench investigations (e.g., via transplantation, repopulation and in vitro expansion).

Erythropoiesis is one focus of our investigations. Red blood cells form continuously at remarkable rates, and defects in their formation are common (e.g., anemias associated with chemotherapy and renal or chronic disease). Key factors that regulate erythropoiesis are incompletely understood, and our investigations may reveal new targets for anti-anemia agents.

EPO-DEPENDENT ERYTHROPOIESIS

In response to hypoxia, Epo is produced and released by sub-populations of renal peritubular interstitial cells as a 30K Mr glycoprotein hormone.  Prime target populations for Epo are CFUe (colony forming units-erythroid), a lineage committed pro-erythroblast population in bone marrow with high expansion capacity.  Epo’s cell surface receptor (EpoR) is predominantly expressed by CFUe, and pre-assembles in association with JAK2 kinase.  Upon bridging EpoR dimers, Epo activates JAK2, and JAK2 then mediates EpoR phosphorylation at eight conserved tyrosine sites.  These cytoplasmic PY motifs then couple to a diverse set of signal transduction factors (STFs) and response pathways.

Functionally, one key role of Epo (and the EpoR) is to promote pro-erythroblast survival.  Previously, this has been suggested to depend upon Stat5 as an EpoR-PY343 coupled STF, and Bcl-xl as a Stat5 target gene.  Recent work, however, argues against Epo and Stat5 routes to Bcl-xl.  Alternatively, EpoR PY479 coupling to p85(p110) PI3 kinase can promote progenitor survival (e.g. via AKT and mTOR pathways).  EpoR alleles that lack PY479, however, efficiently support both steady-state and stress erythropoiesis.

To advance an understanding of Epo’s key actions, our laboratory first has developed a unique system for the ex vivo expansion and development of primary murine bone marrow derived erythroblasts.  By applying this to mice expressing knocked-in minimal EpoR alleles, new structure-function insights have been gained.  These studies (and reinforcing in vivo analyses) reveal that core JAK2-dependent EpoR PY-independent signals support steady-state but not stress erythropoiesis.  The specific restoration of an EpoR-PY343-Stat5 signaling axis, however, efficiently rescues erythropoiesis during anemia.  In part via transcriptome analyses, efforts are underway to identify and functionally characterize prime PY343/Stat5 target genes that selectively promote stress erythropoiesis –  and several candidate factors are well in-hand.

NOVEL EPO ACTION MODES

Our use of bone marrow derived pro-erythroblasts as a primary Epo target population (together with transcriptome analyses) has led to our recent discovery of several unexpected and interesting Epo action modes.  In brief, these include (for example): i/ new evidence that Epo functions in previously unappreciated ways to regulate cell cycle progression; ii/ new insight into discrete sets of Epo-regulated ubiquitination factors; iii/ the defining of novel candidate effectors of Epo’s cytoprotective effects; and iv/ the discovery that Epo sharply modulates several cell surface adhesion and/or cell migration factors (and apparently regulates erythroblast transit from a stromal niche and reticulocyte egress from marrow).  Initial papers on these discoveries are in preparation (see below).  The abilities of minimal EpoR alleles to support these responses, and the capacities of Epo to act (in potentially unique ways) on variously staged erythroid progenitor cells, also are under active investigation.

For the above mechanistic contexts, Epo’s ability to confer cytoprotection for several additionally clinically important tissues is notable.  This includes injured cardiac, neuronal, renal and endothelial cells.

NOVEL ERYTHROBLAST-INTRINSIC REGULATORS OF ERYTHROPOIESIS (AND CANDIDATE TARGETS FOR SMALL MOLECULE ANTI-ANEMIA AGENTS)

Parallel studies focus on the discovery of distinct erythroid progenitor cell-intrinsic developmental regulators.  In particular, we have identified three S/T directed kinases that are expressed at predominant levels in erythroid progenitors: DYRK3 dual specificity kinase, the death-associated protein kinase DAPK2, and a third cytoplasmic (pseudo)kinase now under study.  For each, unique transgenic and knock-out mouse models have been developed.  Interestingly, each kinase appears to exert stage-specific inhibitory effects on erythropoiesis – especially during anemia.  This therefore makes each factor an interesting candidate target for inhibitors in the context of anemia treatment.

FUNCTIONAL COMPONENTS OF PRO-ERYTHROBLAST, HEMATOPOIETIC PROGENITOR CELL, AND STROMAL CELL NICHES

Based, in part, on our discovery that Epo modulates the pro-erythroblast cell surface and its stromal niche, our laboratory has developed active new interests in functional features of such progenitor cell microenvironments, including those for early progenitor cells.  An overall goal is to define (and reconstitute) sets of factors that regulate progenitor cell renewal and migration, and niche boundaries.

Selected Publications

Menon MP, Karur V, Bogacheva O, Bogachev O, Cuetara B, Wojchowski DM.  Signals for stress erythropoiesis are integrated via an erythropoietin receptor-phosphotyrosine-343-Stat5 axis.
Journal of Clinical Investigation.  116:683-94, 2006

Menon MP, Fang J, Wojchowski DM.  Core erythropoietin receptor signals for late erythroblast development.  Blood 107:2662-72, 2006

Karur VG, Lowell CA, Besmer P, Agosti V, Wojchowski DM.  Lyn kinase promotes erythroblast expansion and late-stage development.  Blood 108:1524-32, 2006

Wojchowski DM, Menon MP, Sathyanarayana P, Fang J, Karur V, Houde E, Kapelle W, Bogachev O.  Erythropoietin-dependent erythropoiesis: New insights and questions.  Blood Cells, Molecules and Diseases 36:232-8, 2006

Sathyanarayana P, Menon M, Bogacheva O, Bogachev O, Kapelle WS, Houde E, Niss K, Wojchowski DM. Erythropoietin modulation of podocalyxin, and an erythroblast niche. (2006 submission)

Bogacheva O, Bogachev O, Menon M, Valoret E, Karur V, Prosser H, Creasy C, Erickson-Miller C, Wojchowski DM. DYRK3 kinase is an erythroid cell-intrinsic attenuator of stress erythropoiesis. (2006 submission)

Bogacheva O, Bogachev O, Kapelle W, Sathyanarayana P, Wojchowski DM. Convergent P13-kinase and Epo receptor PY343-dependent pathways co-support erythroblast survival (2006 submission)

Fang J,  Menon M,  Bogacheva O,  Bogachev O,  Karur V,  Houde E,  Kapelle W,  Sathyanarayana P,   Wojchowski DM. Epo regulates cell cycle progression in primary erythroblasts via Stat5, cyclin D2, cyclin G2 pathways. (2006 submission)

Zhang D, Li K, Erickson-Miller CL, Weiss M, Wojchowski DM.  DYRK gene structure and erythroid-restricted features of DYRK3 gene expression.  Genomics 85:117-30, 2005

Karur V, Menon M, Agosti V, Besmer P, Wojchowski DM. Critical roles for c-Kit PY567-coupled signals selectively during stress erythropoiesis (2007 submission)

K Li, M Menon, V Karur, S Hegde, DM Wojchowski. Attenuated signaling by a phosphotyrosine-null Epo receptor form in primary erythroid progenitor cells. Blood 102:3147-3153, 2003

K Li, S Hedge, DM Wojchowski. Roles for an Epo Receptor Tyr-343 Stat5 pathway in proliferative co-signaling with Kit. Journal of Biological Chemistry 278:40702-40709, 2003
 
CP Miller, DW Heilman, DM Wojchowski. Erythropoietin receptor-dependent erythroid colony-forming unit development: capacities of Y343 and phosphotyrosine-null receptor forms. Blood 99:898-904, 2002

K Li, S Zhao, V Karur, DM Wojchowski. DYRK3 activation, engagement of protein kinase A/cAMP response element-binding protein, and modulation of progenitor cell survival. Journal of Biological Chemistry 277:47052-60, 2002

JN Geiger, GT Knudsen, A Pandit, L Panek, M Yoder, K Lord, CL Creasy, BM Burns, S Dillon, DM Wojchowski. mDYRK3 kinase is expressed selectively in late erythroid progenitor cells and attenuates CFUe development. Blood 97:901-910, 2001

TJ Pircher, JN Geiger, D Zhang, CP Miller, P. Gaines, DM Wojchowski. Integrative signaling by minimal erythropoietin receptor forms and c-Kit. Journal of Biological Chemistry 276:8995-9002, 2001

P Gaines, JN Geiger, G Knudsen, D Seshasayee, DM Wojchowski. GATA-l- and FOG-dependent activation of megakaryocytic alpha lIB gene expression. Journal of Biological Chemistry 275:34114-21, 2000

D Seshasayee, P Gaines, DM Wojchowski. GATA-l dominantly activates a program of erythroid gene expression in factor-dependent myeloid FDCW2 cells. Molecular and Cellular Biology, 18: 3278-3288, 1998

H Zhang, SV Patel, TC He, SK Sonsteby, Z Niu, DM Wojchowski. Inhibition of erythropoietin-induced mitogenesis by a kinase-deficient form of Jak2. Journal of Biological Chemistry 269:21411-4, 1994

DE Quelle and DM Wojchowski. Localized cytosolic domains of the erythropoietin receptor regulate growth signaling and down-modulate responsiveness to granulocyte-macrophage colony-stimulating factor. Proc Natl Acad Sci U S A. 88:4801-5, 1991

Available Positions: Scientist/Postdoctoral Position(s) - H601BL
Opportunities exist to assume a lead role in Institute-, NIH- and corporate- sponsored investigations of: 1/ erythroid progenitor cell development (including novel niche-specific Epo action modes, and response factors); 2/ newly discovered tyrosine and S/T kinases with hematopoietic suppressor activities; and 3/ the nature (and action mechanisms) of unique cell migration and adhesion factors involved in cytokine-dependent erythroid, megakaryocytic and myeloid progenitor cell development.
Approaches include new transgenic and knockout mouse models; systems for primary cell development ex vivo; transcriptome analyses and bioinformatics; and human CD34 cell & lentiviral RNAi systems. Opportunities also exist for participation in: studies of small molecule inhibitors & cytokine mimetics; & human patient samples/studies; and graduate & undergraduate teaching. Resources include subsidized cores in: Progenitor Cell Separation and Analysis; Genomics & Bioinformatics;Transgenic mouse construction; Lenti- and retro-virus production; Confocal microscopy; DNA & protein sequencing; Histopathology; and Small animal MRI.
Benefits, salary and resources are nationally competitive and positions are within the laboratory of DM Wojchowski at the Maine Medical Center Research Institute, (www.mmcri.org.) Please send CV, statement of research interests, and professional reference contact information to: resumes@mmc.org

Lab Photo