The Biomedical Research Centre

Hematopoietic Cell Development

Kelly McNagny Interim Co-Director, Biomedical Research Centre Professor, Department of Medical Genetics. Michael Smith Foundation for Health Research Senior Scholar Member of the Stem Cell Network Centre of Excellence Member of the AllerGen Network Centre for Excellence Associate Member of the Stroke Network Centre of Excellence UBC Centre for Blood Research kelly@brc.ubc.ca 604-822-7824

My laboratory is interested in two aspects of hematopoietic stem cell biology: 1) the networks that regulates the commitment of multipotent progenitors to a specific lineage, and 2) the surface receptors expressed by hematopoietic precursor cells that regulate their interacts with their microenvironment and by mature cells that regulate their trafficking in disease.

Signaling networks

We are focusing on the regulatory mechanisms that govern mast cell and eosinophil production. These are relatively rare cells that are responsible for most of the pathology in chronic allergy and asthma and therefore may represent good targets for clinical intervention. We are using a number of transgenic mouse models to identify the factors that govern mast cell and eosinophil formation, homing and function and to perturb these processes during normal development.

Surface molecules expressed by hematopoietic cells

We have focused predominantly on CD34-type proteins. CD34 is a cell surface sialomucin and the most widely used marker of hematopoietic stem cells and vascular endothelia. Recently we identified two novel receptors, Podocalyxin (also called Podxl, GCTM2, MEP21, gp135, Thrombomucin and PCLP1) and Endoglycan (Podxl2) that are also expressed by hematopoietic stem/progenitor cells and vasculature. We have shown that, together with CD34, these additional molecules comprise a gene family and that all three are probably derived from a common ancestral gene. Surprisingly, despite the extensive use of CD34 as a stem cell marker, virtually nothing is known of its function and it has alternatively be touted as a(n):

1) blocker of HSC differentiation
2) enhancer of HSC proliferation
3) bone marrow homing receptor
4) pro-adhesive receptor
5) anti-adhesive receptor

Targeted deletion of the CD34 gene in mice has only fueled the debate concerning its function since these mice exhibit extremely subtle perturbations in normal hematopoietic function that could be used to support each of the above hypotheses.

The discovery of two novel members of this gene family with overlapping expression patterns, has allowed us to: (1) re-evaluate these results in light of the potential for functional compensation and, (2) to generate compound mutant mice to test the true function of these receptors. In aggregate, these studies have allowed us to prove that the CD34 family of proteins function predominantly as anti-adhesion molecules, or “molecular Teflon”. Thus, they enhance the mobility and invasiveness of hematopoietic cells and on non-hematopoietic cells they are able to disrupt cell-cell junctional complexes between neighboring adherent cells (vascular endothelia or podocytes in the kidney, for example). This is not a constitutive function, but is tightly regulated by a set of proteins that bind to the cytoplasmic tail of CD34-type proteins and regulate their subcellular localization and proximity to adhesion molecules. Preliminary data suggest that loss of CD34-type proteins leads to defects in hematopoietic function by preventing the HSC from entering the appropriate microenvironments (due to excessive adhesion). Similarly, CD34, itself, aids in the trafficking of mucosal inflammatory cells (mainly eosinophils and mast cells) and mice lacking CD34 are remarkably resistant to a variety of inflammatory diseases. On endothelial cells we find that these proteins can regulate polarity, cell-cell adhesion and vascular permeability. Finally, we have shown that these same “anti-adhesion” molecules are upregulated in an aggressive subset of epithelial tumors and lead to increased invasiveness and loss of cell polarity. They may, thus, prove to be excellent prognostic indicators of poor outcome tumors and provide a means of identifying these cancers early for aggressive therapy.

Selected Publications (See all publications)

Maltby S, Wohlfarth C, Gold M, Zybtnuik L, Hughes MR, McNagny KM. CD34 is required for infiltration of eosinophils into the colon during DSS-induced ulcerative colitis. Am. J. Path. 177:1244-54, 2010.

Naus S#, Blanchet MR#, Gossens K, Zaph C, Bartsch J, and McNagny KM*, Ziltener HJ*. The metalloprotease, ADAM8, is essential for the development of experimental asthma. Am. J. Resp. Crit. Care. Med. 181: 1318-28, 2010. Co-first authors#, Co-corresponding authors*.

Zarzeczny A, Scott C, Hyun I, Bennett J, Chandler J, Chargé S, Heine H, Isasi R, Kato K, Lovell-Badge R, McNagny K, Pei D, Rossant J, Surani A, Taylor PL, Ogbogu U and Caulfield T. iPS Cells: Mapping the Policy Issues Cell 139: 1032-7, 2009.

Strilic B, Kucera T, Eglinger J, Hughes MR, McNagny KM, Tsukita S, Dejana E, Ferrara N and Lammert E. The molecular basis of vascular lumen formation in the developing mouse aorta. Developmental Cell 17:505-15, 2009. (Faculty of 1000 – top choice).

Nielsen JS and McNagny KM. functions of the CD34 family. J Cell Science 121: 2683-2692, 2008

Haddon DJ, Antignano F, Hughes MR, Blanchet M-R, Zbytnuik L, Krystal G, and McNagny KM. SHIP1 is a repressor of mast cell hyperplasia, cytokine production, and allergic inflammation in vivo. J. Immunol. 183: 228-36, 2009

Bennett JL, Blanchet M-R, Zhou L, Kubes P, and McNagny KM. Mast cells accumulate in the CNS through both local proliferation and peripheral recruitment during EAE but are dispensable for pathogenesis. J. Immunol. 182: 5507-14, 2009

Blanchet MR, Maltby S, Haddon DJ, Merkens H, Zbytnuik L and McNagny KM. CD34 Facilitates The Development of Allergic Asthma. Blood 110:2005-2012, 2007

Gournaris E, Erdman, SE, Restaino C, Gurish MF, Friend DS, Gounari F, Lee DM, Zhang G, Glickman JN, Shin K, Rao VP, Poutahidis T, Weissleder R, McNagny KM*, Khazaie K. Mast Cells are an essential component for polyp development. Proc. Nat. Acad. Science 104: 19977-19982, 2007

Doyonnas R*, Nielsen J*, Drew E, Chelliah SJ, Hara T. Miyajima A, and McNagny, KM. Podocalyxin is a CD34-related marker of murine hematopoietic stem cells and embryonic erythroid cells. Blood. Plenary paper 105:4170-4178, 2005

Drew E, Merzaban J, Seo W, Ziltener HJ, and McNagny, KM. CD34 and CD43 inhibit mast cell adhesion and are required for optimal mast cell reconstitution. Immunity. 22: 43-57, 2005

Somasiri A, Nielsen J, Makretsov N, Gilks CB, Huntsman D, Gelmon KA, Kershaw DB, and McNagny KM*, Roskelley C.* Overexpression of the anti-adhesin Podocalyxin is an independent predictor of breast cancer progression. Cancer Research 64: 5068-5073, 2004

McNagny K and Graf T. Making eosinophils through subtle shifts in transcription factor expression. J Exp Med. 195: F43-7, 2002.

Doyonnas R, Kershaw DB, Duhme C, Merkens H, Chelliah S, Graf T and McNagny KM. Anuria, omphalocele and perinatal lethality in mice lacking the CD34-related protein, Podocalyxin. J. Exp. Med 194: 13-27, 2001

Lab Members

Research Associates
Michael Hughes PhD
Martin Lopez PhD

Students
Matthew Gold, Graduate Academic Assistant
Kimberly Snyder, Graduate Academic Assistant
Bernard Lo, Graduate Academic Assistant