Dwayne L. Barber
PhD, University of Alberta
Ontario Cancer Institute / Princess Margaret Hospital
610 University Avenue, Room 9-329
Toronto, ON M5G 2M9 CANADA
Phone: (416) 946-4455
Lab Phone: (416) 581-7869
Email Dr. Dwayne Barder
Signalling Mechanisms in Hematopoietic Cells
Cells within the bone marrow respond to a host of growth factors that promote their growth, survival and differentiation. Our laboratory studies signal transduction in normal and leukemogenic hematopoiesis. Current studies are focussed in three specific areas: understanding the role of Erythropoietin (EPO) in red blood cell production, characterization of the signal transduction pathways activated downstream of BCR-ABL and delineation of the molecular mechanism underlying the poor prognosis of Chronic Myeloid Leukemia patients harbouring deletions at Chromosome 9q34.
EPO is the major cytokine regulator of red blood cell production. This cytokine binds to its cognate receptor (EPO-R) and initiates signal transduction through activation of the JAK2 cytoplasmic tyrosine kinase. JAK2 subsequently phosphorylates the EPO-R on several cytoplasmic tyrosine residues, which facilitates recruitment of several SH2 domain-containing proteins. Genetic evidence suggests that deletion of EPO, EPO-R or JAK2 in mice results in embryonic lethality due to a fatal anemia that develops during embryogenesis. This implies that critical signals emanate downstream of the EPO-R and/or JAK2.
Our approaches to dissect EPO-mediated signalling are to utilize knockout mice devoid of expression of critical downstream players. In addition, we have used microarray to examine gene regulation mediated by EPO. We are most interested in characterizing the transcriptome in primary cells under conditions that support normal and stress erythropoiesis.
Approximately one-half of leukemias arise from chromosomal translocations. Novel fusion proteins are generated which deliver a growth advantage to the stem cell in which they reside in the bone marrow. We are interested in the tyrosine kinase subclass of chromosomal translocations including TEL-JAK2 and BCR-ABL. Our goal is to identify the critical downstream signalling pathways that contribute to leukemogenesis mediated by BCR-ABL. We are utilizing retroviral transduction/bone marrow transplantation technology to approach this problem.
The causative agent of Chronic Myeloid Leukemia (CML) is the BCR-ABL chromosomal translocation. Dr. Jeremy Squire has demonstrated that a subset of CML patients with poor prognosis harbour deletions centromeric to the ABL gene at Chromosome 9q34. His laboratory has mapped a minimal deleted region of 120 MB that contains several genes. Our current studies are to identify and characterize the expression pattern of these genes in CML cell lines and primary CML cells. Our long-term goal is to develop mice devoid of expression of the genes located in the deleted region to determine whether BCR-ABL causes a more aggressive disease in a bone marrow transplant model.
Selected References:Link to Pubmed Publications
Richmond TD, Chohan M, and Barber, D.L. 2005. Turning Cells Red: Signal Transduction Mediated by Erythropoietin. Trends Cell Biol. 15:146-55.
Halupa A, Bailey M, Huang K, Iscove NN, Levy DE, Barber DL. A Novel Role for STAT1 in Regulating Murine Erythropoiesis: Deletion of STAT1 Results in Overall Reduction of Erythroid Progenitors and Alters Their Distribution. Blood. 105: 552-61, 2005.
Chu X, Tong Q, Cheung JY, Wozney J, Conrad K, Mazack V, Zhang W, Stahl R, Barber DL, Miller BA. Interaction of TRPC2 and TRPC6 in erythropoietin modulation of calcium influx. J Biol Chem. 279:10514-22, 2004.
Haq R, Halupa A, Beattie BK, Mason JM, Zanke BW, Barber DL. Regulation of erythropoietin-induced STAT serine phosphorylation by distinct mitogen-activated protein kinases. J Biol Chem . 277 :17359-66, 2002.
Chu X, Cheung JY, Barber DL, Birnbaumer L, Rothblum LI, Conrad K, Abrasonis V, Chan YM, Stahl R, Carey DJ, Miller BA. Erythropoietin modulates calcium influx through TRPC2. J Biol Chem. 277:34375-82, 2002.
Barber DL, Beattie BK, Mason JM, Nguyen MH, Yoakim M, Neel BG, D'Andrea AD, Frank DA. A common epitope is shared by activated signal transducer and activator of transcription-5 (STAT5) and the phosphorylated erythropoietin receptor: implications for the docking model of STAT activation. Blood. 97 : 2230-7, 2001.
Mason JM, Beattie BK, Liu Q, Dumont DJ, Barber DL. The SH2 inositol 5-phosphatase Ship1 is recruited in an SH2-dependent manner to the erythropoietin receptor. J Biol Chem. 275 : 4398-406, 2000.
Miller BA, Barber DL, Bell LL, Beattie BK, Zhang MY, Neel BG, Yoakim M, Rothblum LI, Cheung JY. Identification of the erythropoietin receptor domain required for calcium channel activation. J Biol Chem. 274 : 20465-72, 1999.
Barber DL, Mason JM, Fukazawa T, Reedquist KA, Druker BJ, Band H, D'Andrea AD. Erythropoietin and interleukin-3 activate tyrosine phosphorylation of CBL and association with CRK adaptor proteins. Blood. 89 : 3166-74, 1997.
Barber DL, Corless CN, Xia K, Roberts TM, D'Andrea AD. Erythropoietin activates Raf1 by an Shc-independent pathway in CTLL-EPO-R cells. Blood. 89 : 55-64, 1997.
Luo H, Rose P, Barber D, Hanratty WP, Lee S, Roberts TM, D'Andrea AD, Dearolf CR. Mutation in the Jak kinase JH2 domain hyperactivates Drosophila and mammalian Jak-Stat pathways. Mol Cell Biol. 17 : 1562-71, 1997.
Ho JM, Nguyen MH, Dierov JK, Badger KM, Beattie BK, Tartaro P, Haq R, Zanke BW, Carroll MP, Barber DL. TEL-JAK2 constitutively activates the extracellular signal regulated kinase (ERK), stress-activated protein/Jun kinase (SAPK/JNK), and p38 signaling pathways. Blood . 100 :1438-48, 2002.
Nguyen MH, Ho JM, Beattie BK, Barber DL. TEL-JAK2 Mediates Constitutive Activation of the Phosphatidylinositol 3'-Kinase/Protein Kinase B Signaling Pathway. J Biol Chem. 276 : 32704-32713, 2001.
Ho JM, Beattie BK, Squire JA, Frank DA, Barber DL. Fusion of the ets transcription factor TEL to Jak2 results in constitutive Jak-Stat signaling. Blood. 93 : 4354-64, 1999.
Kolomietz E, Marrano P, Yee K, Thai B, Braude I, Kolomietz A, Chun K, Minkin S, Kamel-Reid S, Minden M, Squire JA. Quantitative PCR identifies a minimal deleted region of 120 kb extending from the Philadelphia chromosome ABL translocation breakpoint in chronic myeloid leukemia with poor outcome. Leukemia. 17: 1313-23, 2003.