The tetraspanin CD9 regulates migration, adhesion, and homing of human cord blood CD34+ hematopoietic stem and progenitor cells.
The stromal cell-derived factor-1 (SDF-1)/chemokine C-X-C receptor 4 (CXCR4) axis plays a critical role in homing and engraftment of hematopoietic stem/progenitor cells (HSCs) during bone marrow transplantation. To investigate the transcriptional regulation provided by this axis, we performed the first differential transcriptome profiling of human cord blood CD34(+) cells in response to short-term exposure to SDF-1 and identified a panel of genes with putative homing functions. We demonstrated that CD9, a member of the tetraspanin family of proteins, was expressed in CD34(+)CD38(-/lo) and CD34(+)CD38(+) cells. CD9 levels were enhanced by SDF-1, which simultaneously down-regulated CXCR4 membrane expression. Using specific inhibitors and activators, we demonstrated that CD9 expression was modulated via CXCR4, G-protein, protein kinase C, phospholipase C, extracellular signal-regulated kinase, and Janus kinase 2 signals. Pretreatment of CD34(+) cells with the anti-CD9 monoclonal antibody ALB6 significantly inhibited SDF-1-mediated transendothelial migration and calcium mobilization, whereas adhesion to fibronectin and endothelial cells was enhanced. Pretreatment of CD34(+) cells with ALB6 significantly impaired their homing to bone marrow and spleen of sublethally irradiated NOD/SCID (nonobese diabetic/severe combined immune-deficient) mice. Sorted CD34(+)CD9(-) cells displayed lower bone marrow homing capacity compared with that of total CD34(+) cells. CD9 expression on homed CD34(+) cells was significantly up-regulated in vivo. Our results indicate that CD9 might possess specific functions in HSC homing.
Department of Paediatrics, The Chinese University of Hong Kong, Shatin, Hong Kong.
Kam Tong
KT
Leung
Kathy Yuen Yee
KY
Chan
Pak Cheung
PC
Ng
Tze Kin
TK
Lau
Wui Man
WM
Chiu
Kam Sze
KS
Tsang
Chi Kong
CK
Li
Carrie Ka Lai
CK
Kong
Karen
K
Li
D000818:Animals; D057134:Antibodies, Neutralizing; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology*; D018952:Antigens, CD34 / Q000378:metabolism; D002448:Cell Adhesion / Q000276:immunology / Q000502:physiology; D002465:Cell Movement / Q000276:immunology / Q000502:physiology; D054377:Chemokine CXCL12 / Q000494:pharmacology; D005312:Fetal Blood / Q000166:cytology*; D020869:Gene Expression Profiling; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000276:immunology* / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D020411:Oligonucleotide Array Sequence Analysis; D019718:Receptors, CXCR4 / Q000502:physiology; D015398:Signal Transduction; D060245:Tetraspanin 29; D014183:Transplantation, Heterologous
D057134:Antibodies, Neutralizing; D015703:Antigens, CD; D018952:Antigens, CD34; C554869:CD9 protein, human; C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; C554870:Cd9 protein, mouse; D054377:Chemokine CXCL12; D008562:Membrane Glycoproteins; D019718:Receptors, CXCR4; D060245:Tetraspanin 29