Stem cell growth factor: isolation of the cDNA, analysis on the gene expression, molecular characterization and in vitro proliferative activity of a recombmant preparation on primitive hematopoietic progenitor cells

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On an attempt to realize diagnostic and therapeutic application of stem cell growth factor (SCGF) in hematology we studied molecular characterization, the gene expression and hematopoietic activities of a recombmant human (rh) SCGF. A full-length cDNA for human, mouse and rat SCGF was cloned using bone marrow cells, MC3T3-G2/PA6 preadipocytes and ROS-17/2.8-5 osteosarcoma cells, respectively, SCGF was a new member of a C-type lectin superfamily and most homologous with tetranectin. A 21aa signal peptide was removed to give rise to mature SCGF with MW 40 kDa. SCGF was not N-glycosylated, but O-glycosylated with sialic acid. Leucine zipper-like sequence could induce SCGF to form a ternary α-helical coiled-coil structure. Northern and in situ hybridization analysis showed specific expression of SCGF mRNA in the spleen, fetal liver and skeletal tissues, particularly in bone marrow cells, periosteum and proliferating chondrocytes, but little expression in resting or hypertrophic chondrocyte … More s, indicating that SCGF affected osteogenesis. Fluorescent in situ hybridization mapped human and mouse SCGF genes to chromosome 19q13.3 and 7B3-B5, respectively, where flt3 ligand and IL-11 genes were clustered. CHO cells were stably transformed with an expression vector PAGE-SCGF, and an endotoxin-free rhSCGF was purified from the culture supernatant. Anti-SCGF monoclonal antibodies were obtained by immunizing rats with a synthetic oligopeptide. For human bone marrow CD34+Lin- cells rhSCGF promoted growth of erythroid and granulocyte/macrophage colonies in the culture with erythropoietin and GM-CSF or G-CSF, respectively, and was synergistic with IL-3 and flt3 ligand to enhance GM colony-growth.SCGF is selectively produced by osseous and hematopoietic stromal cells and can mediate their proliferative activity on hematopoietic stem cells. For further characterization of SCGF, activities on other cells, receptor, knockout mice and clinical aspects should be studied, and SCGF is surely expected to build a new stem cell biology paradigm. Less