ISSN: 2229-6646 IJSTM, Vol. 3 Issue 2, September 2012 www.ijstm.com © International Journal of Science Technology & Management Page 42 MULTIDIMENSIONAL ROLE OF CD34 PROTEIN IN HEMATOPOIETIC STEM CELL BIOLOGY Vimal Kishor Singh 1,$ , Kohichiro Tsuji 2, PB Sharma 1, Ramesh Chandra 3 1 Department of Biotechnology, Delhi Technological University, Shahbad Daulatpur, Bawana road, Delhi-110042, India; $ Stem Cell Gene Therapy Research Group, Institute of Nuclear Medicine & Allied Sciences, Lucknow Road, Delhi-110054, India; 2 The University of Tokyo Hospital The Institute of Medical Science Research Hospital Department of Pediatric Hematology/Oncology; Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi Delhi-110 007, India Correspondence: Prof. Ramesh Chandra, Founder Director Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi Delhi -110 007, India Tel: +91-11-27666245, 27666272 Fax: +91-11- 27666248, 27667730 E-mail: acbrdu@hotmail.com ; vim_kissor@yahoo.co.in Key words: CD34, HSCs, Homing, Adhesion, Proliferation, Differentiation Abstract CD34 is a highly glycosylated surface-expressed sialomucin and, because it is present on hematopoietic stem cells (HSCs), has demonstrated immense clinical utility in their enumeration in aphaeresis products, immunoaffinity purification for transplantation, and disease monitoring. The success of CD34 based reagents in identifying hematopoietic progenitors led to the assumption that CD34 is expressed on cells with regenerative potential and is sufficient for hematopoietic reconstitution in marrow-ablated recipients. Recently, researchers have identified the existence of CD34 -neg HSCs, which have also been shown to successfully reconstitute hematopoiesis in both human and primate models. These reports stymied efforts to precisely define a critical role for CD34 in hematopoietic biology. Preliminary reports indicated its role in the early hematopoiesis, differentiation, and proliferation of HSCs. However, evidences accumulated so far suggest that CD34 is predominantly an adhesion/anti-adhesion molecule playing crucial role in HSCs trafficking. These studies are still in the early stages and a detailed analysis of the structural and functional importance of CD34 is likely to enhance our understanding of its role in hematopoiesis. This article reviews the biological significance of CD34 in hematopoiesis.