Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Rac GTPases differentially integrate signals regulating hematopoietic stem cell localization

Nature Medicine volume 11, pages 886–891 (2005)Cite this article

Abstract

The molecular events that regulate engraftment and mobilization of hematopoietic stem cells and progenitors (HSC/Ps) are still incompletely defined1,2. We have examined the role of the Rho GTPases Rac1 and Rac2 in HSC engraftment and mobilization. Rac1, but not the hematopoietic-specific Rac2, is required for the engraftment phase of hematopoietic reconstitution, because Rac1−/− HSCs did not rescue in vivo hematopoiesis after transplantation, but deletion of Rac1 after engraftment did not impair steady-state hematopoiesis. Rac1−/− HSC/Ps showed impaired spatial localization to the endosteum but near-normal homing to the medullary cavity in vivo. Interaction with the bone marrow microenvironment in vitro was markedly altered. Whereas post-engraftment deletion of Rac1 alone did not impair hematopoiesis, deficiency of both Rac1 and Rac2 led to massive mobilization of HSCs from the marrow associated with ineffective hematopoiesis and intense selection for Rac-expressing HSCs. This mobilization was reversible by re-expression of Rac1. In addition, a rationally designed, reversible small-molecule inhibitor of Rac activation led to transient mobilization of engraftable HSC/Ps. Rac proteins thus differentially regulate engraftment and mobilization phenotypes, suggesting that these biological processes and steady-state hematopoiesis are biochemically separable and that Rac proteins may be important molecular targets for stem cell modification.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Effect of Rac deficiency on steady-state hematopoiesis, homing and transendothelial migration of HSC/Ps.
Figure 2: CAFC frequency and spatial distribution of HSC/Ps of wild-type and Rac-deficient bone marrow cells.
Figure 3: Mobilization of HSC/Ps in Rac-deficient mice.
Figure 4: Effect of NSC23766 on mobilization of HSC/Ps.

Similar content being viewed by others

References

  1. Lapidot, T., Dar, A. & Kollet, O. How do stem cells find their way home? Blood published online 12 May 2005 (10.1182/blood-2005-04-1417).

  2. Papayannopoulou, T. Current mechanistic scenarios in hematopoietic stem/progenitor cell mobilization. Blood 103, 1580–1585 (2004).

    Article  CAS  Google Scholar 

  3. Zhang, J. et al. Identification of the haematopoietic stem cell niche and control of the niche size. Nature 425, 836–841 (2003).

    Article  CAS  Google Scholar 

  4. Cottler-Fox, M.H. et al. Stem cell mobilization. Hematology (Am. Soc. Hematol. Educ. Program) 419–437 (2003).

  5. Simmons, P.J., Levesque, J.P. & Zannettino, A.C. Adhesion molecules in haemopoiesis. Baillieres Clin. Haematol. 10, 485–505 (1997).

    Article  CAS  Google Scholar 

  6. Levesque, J.P. & Simmons, P.J. Cytoskeleton and integrin-mediated adhesion signaling in human CD34+ hemopoietic progenitor cells. Exp. Hematol. 27, 579–586 (1999).

    Article  CAS  Google Scholar 

  7. Lapidot, T. & Petit, I. Current understanding of stem cell mobilization: the roles of chemokines, proteolytic enzymes, adhesion molecules, cytokines, and stromal cells. Exp. Hematol. 30, 973–981 (2002).

    Article  CAS  Google Scholar 

  8. Cancelas, J.A. et al. Peripheral blood CD34+ cell immunomagnetic selection in breast cancer patients: effect on hematopoietic progenitor content and hematologic recovery after high-dose chemotherapy and autotransplantation. Transfusion 38, 1063–1070 (1998).

    Article  CAS  Google Scholar 

  9. Christopherson, K.W., Cooper, S., Hangoc, G. & Broxmeyer, H.E. CD26 is essential for normal G-CSF-induced progenitor cell mobilization as determined by CD26−/− mice. Exp. Hematol. 31, 1126–1134 (2003).

    Article  CAS  Google Scholar 

  10. Gu, Y. et al. Hematopoietic cell regulation by Rac1 and Rac2 guanosine triphosphatases. Science 302, 445–449 (2003).

    Article  CAS  Google Scholar 

  11. Yang, F.C. et al. Rac and Cdc42 GTPases control hematopoietic stem cell shape, adhesion, migration, and mobilization. Proc. Natl Acad. Sci. USA 98, 5614–5618 (2001).

    Article  CAS  Google Scholar 

  12. Didsbury, J., Weber, R.F., Bokoch, G.M., Evans, T. & Snyderman, R. rac, a novel ras-related family of proteins that are botulinum toxin substrates. J. Biol. Chem. 264, 16378–16382 (1989).

    CAS  PubMed  Google Scholar 

  13. Haataja, L., Groffen, J. & Heisterkamp, N. Characterization of RAC3, a novel member of the Rho family. J. Biol. Chem. 272, 20384–20388 (1997).

    Article  CAS  Google Scholar 

  14. Johnson, D.I. Cdc42: An essential Rho-type GTPase controlling eukaryotic cell polarity. Microbiol. Mol. Biol. Rev. 63, 54–105 (1999).

    CAS  PubMed  PubMed Central  Google Scholar 

  15. Yang, F.C. et al. Rac2 stimulates Akt activation affecting BAD/Bcl-XL expression while mediating survival and actin function in primary mast cells. Immunity 12, 557–568 (2000).

    Article  CAS  Google Scholar 

  16. Gu, Y. et al. Biochemical and biological characterization of a human Rac2 GTPase mutant associated with phagocytic immunodeficiency. J. Biol. Chem. 276, 15929–15938 (2001).

    Article  CAS  Google Scholar 

  17. Roberts, A.W. et al. Deficiency of the hematopoietic cell-specific Rho family GTPase Rac2 is characterized by abnormalities in neutrophil function and host defense. Immunity 10, 183–196 (1999).

    Article  CAS  Google Scholar 

  18. Filippi, M.D. et al. Localization of Rac2 via the C terminus and aspartic acid 150 specifies superoxide generation, actin polarity and chemotaxis in neutrophils. Nat. Immunol. 5, 744–751 (2004).

    Article  CAS  Google Scholar 

  19. Papayannopoulou, T., Brice, M. & Stamatoyannopoulos, G. Hemoglobin F synthesis in vitro: evidence for control at the level of primitive erythroid stem cells. Proc. Natl Acad. Sci. USA 74, 2923–2927 (1977).

    Article  CAS  Google Scholar 

  20. Peled, A. et al. Dependence of human stem cell engraftment and repopulation of NOD/SCID mice on CXCR4. Science 283, 845–848 (1999).

    Article  CAS  Google Scholar 

  21. Driessen, R.L., Johnston, H.M. & Nilsson, S.K. Membrane-bound stem cell factor is a key regulator in the initial lodgment of stem cells within the endosteal marrow region. Exp. Hematol. 31, 1284–1291 (2003).

    Article  CAS  Google Scholar 

  22. Jansen, M., Yang, F.C., Cancelas, J.A., Bailey, J.R. & Williams, D.A. Rac2-deficient hematopoietic stem cells show defective interaction with the hematopoietic microenvironment and long-term engraftment failure. Stem Cells 23, 335–346 (2005).

    Article  CAS  Google Scholar 

  23. Scott, L.M., Priestley, G.V. & Papayannopoulou, T. Deletion of alpha4 integrins from adult hematopoietic cells reveals roles in homeostasis, regeneration, and homing. Mol. Cell. Biol. 23, 9349–9360 (2003).

    Article  CAS  Google Scholar 

  24. Gao, Y., Dickerson, J.B., Guo, F., Zheng, J. & Zheng, Y. Rational design and characterization of a Rac GTPase-specific small molecule inhibitor. Proc. Natl Acad. Sci. USA 101, 7618–7623 (2004).

    Article  CAS  Google Scholar 

  25. Roberts, A.W. et al. Genetic influences determining progenitor cell mobilization and leukocytosis induced by granulocyte colony-stimulating factor. Blood 89, 2736–2744 (1997).

    CAS  PubMed  Google Scholar 

  26. Ploemacher, R.E., van der Sluijs, J.P., van Beurden, C.A., Baert, M.R. & Chan, P.L. Use of limiting-dilution type long-term marrow cultures in frequency analysis of marrow-repopulating and spleen colony-forming hematopoietic stem cells in the mouse. Blood 78, 2527–2533 (1991).

    CAS  PubMed  Google Scholar 

  27. Gazitt, Y. Homing and mobilization of hematopoietic stem cells and hematopoietic cancer cells are mirror image processes, utilizing similar signaling pathways and occurring concurrently: circulating cancer cells constitute an ideal target for concurrent treatment with chemotherapy and antilineage-specific antibodies. Leukemia 18, 1–10 (2004).

    Article  CAS  Google Scholar 

  28. Levesque, J.P., Hendy, J., Winkler, I.G., Takamatsu, Y. & Simmons, P.J. Granulocyte colony-stimulating factor induces the release in the bone marrow of proteases that cleave c-KIT receptor (CD117) from the surface of hematopoietic progenitor cells. Exp. Hematol. 31, 109–117 (2003).

    Article  CAS  Google Scholar 

  29. Boggs, D.R. The total marrow mass of the mouse: a simplified method of measurement. Am. J. Hematol. 16, 277–286 (1984).

    Article  CAS  Google Scholar 

  30. Nilsson, S.K., Johnston, H.M. & Coverdale, J.A. Spatial localization of transplanted hemopoietic stem cells: inferences for the localization of stem cell niches. Blood 97, 2293–2299 (2001).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by US National Institutes of Health grant numbers R01 DK62752 (to D.A.W.) and R01 GM60523 (to Y.Z.). J.A.C. is a recipient of an award from the National Blood Foundation (United States). The authors want to thank M.-D. Filippi, H. Geiger and J. Mulloy for critical review of the manuscript; D. Witte for assistance in histologic analysis of organs; N. Krishnan, Y. Yamada, J. Bailey, V. Summey-Harner, C. Harris, F. Sadique, S. Homan and L. McMillan for technical assistance, and M. O'Leary, J. Hayden and E. Meunier for providing assistance in manuscript editing. We thank the Experimental Hematology Division Mouse and Flow Cores for services and Amgen, Inc. and Takara Bio for reagents.

Author information

Authors and Affiliations

  1. Hoxworth Blood Center, University of Cincinnati Medical Center, 3130 Highland Avenue, Cincinnati, 45267, Ohio, USA

    Jose A Cancelas

  2. Division of Experimental Hematology, Cincinnati Children's Research Foundation, 3333 Burnet Avenue, Cincinnati, 45229, Ohio, USA

    Jose A Cancelas, Andrew W Lee, Rethinasamy Prabhakar, Yi Zheng & David A Williams

  3. Division of Pathology, Cincinnati Children's Research Foundation, 3333 Burnet Avenue, Cincinnati, 45229, Ohio, USA

    Keith F Stringer

Authors
  1. Jose A Cancelas
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Andrew W Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Rethinasamy Prabhakar
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Keith F Stringer
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Yi Zheng
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. David A Williams
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to David A Williams.

Ethics declarations

Competing interests

The authors have a pending patent on Rac inhibitors.

Supplementary information

Supplementary Fig. 1

Lineage reconstitution in peripheral blood of polyI:C treated mice (Rac-deficient) cells. (PDF 173 kb)

Supplementary Fig. 2

Content of HSC/P in BM and spleen of Rac-deficient mice. (PDF 267 kb)

Supplementary Fig. 3

Mobilization of HSC/P in Rac-deficient mice. (PDF 325 kb)

Supplementary Methods (PDF 43 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Cancelas, J., Lee, A., Prabhakar, R. et al. Rac GTPases differentially integrate signals regulating hematopoietic stem cell localization. Nat Med 11, 886–891 (2005). https://doi.org/10.1038/nm1274

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nm1274

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing