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Blood, 1 December 2006, Vol. 108, No. 12, pp. 3637-3645. Prepublished online as a Blood First Edition Paper on August 1, 2006; DOI 10.1182/blood-2006-03-005942. This Article Full Text (PDF) All Versions of this Article: blood-2006-03-005942v1 108/12/3637    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Kalfa, T. A. Articles by Zheng, Y. Search for Related Content PubMed PubMed Citation Articles by Kalfa, T. A. Articles by Zheng, Y. Related Collections Related Article in Blood Online Social Bookmarking                   What's this?  Previous Article  |  Next Article  Submitted March 2, 2006 Accepted July 12, 2006 Rac GTPases regulate the morphology and deformability of the erythrocyte cytoskeleton Theodosia A. Kalfa*, Suvarnamala Pushkaran, Narla Mohandas, John H. Hartwig, Velia M. Fowler, James F. Johnson, Clinton H. Joiner, David A Williams, and Yi Zheng Cincinnati Children's Hospital Medical Center and University of Cinicinnati Cincinnati Children's Hospital Medical Center New York Blood Center, New York, NY Brigham and Women's Hospital The Scripps Research Institute * Corresponding author; email: theodosia.kalfa{at}cchmc.org. Actin oligomers are a significant structural component of the erythrocyte cytoskeleton. Rac1 and Rac2 GTPases regulate actin structures and have multiple overlapping as well as distinct roles in hematopoietic cells; therefore, we studied their role in red blood cells (RBCs). Conditional gene targeting with a loxP-flanked Rac1 gene allowed Cre-recombinase-induced deletion of Rac1 on a Rac2 null genetic background. The Rac1-/-;Rac2-/- mice developed microcytic anemia with a hemoglobin drop of ~20% and significant anisocytosis and poikilocytosis. Reticulocytes increased >2-fold. Rac1-/-;Rac2-/- RBCs stained with rhodamine-phalloidin demonstrated F-actin meshwork gaps and aggregates under confocal microscopy. Transmission electron microscopy of the cytoskeleton demonstrated junctional aggregates and pronounced irregularity of the hexagonal spectrin scaffold. Ektacytometry confirmed that these cytoskeletal changes in Rac1-/-;Rac2-/- erythrocytes were associated with significantly decreased cellular deformability. The composition of the cytoskeletal proteins was altered with increased actin to spectrin ratio and increased phosphorylation (serine-724) of adducin, an F-actin capping protein. Actin and phosphorylated adducin of Rac1-/-;Rac2-/- erythrocytes were more easily extractable by Triton-X-100, indicating weaker association to the cytoskeleton. Thus, deficiency of Rac1 and Rac2 GTPases in mice alters actin assembly in RBCs and causes microcytic anemia with reticulocytosis, implicating Rac GTPases as dynamic regulators of the erythrocyte cytoskeleton organization. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? Related Article in Blood Online: A new Rac-ket in red cells Velia M. Fowler and Robert S. Fischer Blood 2006 108: 3633-3634. [Full Text] [PDF] This article has been cited by other articles: J.-A. Kang, Y. Zhou, T. L. Weis, H. Liu, J. Ulaszek, N. Satgurunathan, L. Zhou, K. van Besien, J. Crispino, A. Verma, et al. Osteopontin Regulates Actin Cytoskeleton and Contributes to Cell Proliferation in Primary Erythroblasts J. Biol. Chem., March 14, 2008; 283(11): 6997 - 7006. [Abstract] [Full Text] [PDF]

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