Recombinant Human SCGF-alpha/CLEC11a Protein

Stem Cell Growth Factor (SCGF), also known as LSLCL, P47, and CLEC11A, is a secreted glycoprotein that acts on primitive hematopoietic stem/progenitor cells to support their proliferation and differentiation. Mature human SCGF contains an N‑terminal Glu‑rich region with an RGD motif, a leucine zipper region, and a C‑terminal lectin‑like domain (1, 2). The RGD motif is absent in mouse and rat SCGF (1). Full length human SCGF (the alpha isoform) shares approximately 83% amino acid (aa) sequence identity with mouse and rat SCGF. A shorter SCGF beta isoform lacks 78 aa of the lectin domain (1‑3). This recombinant protein corresponds to the SCGF alpha isoform. SCGF is produced by various hematopoietic cell lines and by CD34⁺ and CD34‑CD33⁺ bone marrow cells as a 47 kDa sulfated and O‑glycosylated sialoprotein (2‑6). It is also expressed by infiltrating macrophages in some gastrointestinal tract tumors (7). Mouse SCGF mRNA has been detected in proliferating chondrocytes, the primary ossification center, perichondrium, and periosteum (6). SCGF should not be confused with the similarly named SCF (stem cell factor)/c‑Kit Ligand which exerts distinct activities during hematopoietic differentiation. SCGF exhibits erythroid burst (BFU‑E) promoting activity in the absence of SCF/c‑kit Ligand but suppresses the formation of erythroid bursts induced by SCF (4, 6). SCGF cooperates with IL‑3, Flt‑3 Ligand, GM‑CSF, or G‑CSF to enhance the growth of granulocyte‑macrophage colonies (CFU‑GM) (4, 6). It also promotes (with Flt‑3 Ligand and VEGF) the maintenance and expansion of CD34⁺CD133⁺ progenitor cells as well as their differentiation into the endothelial lineage (8, 9). Serum levels of SCGF increase during stem cell transplantation and correlate with the recovery of hematopoiesis (5). Circulating SCGF levels are decreased in severe malarial anemia, and an SCGF promoter polymorphism (-539C/T) is associated with resistance to malarial anemia (10, 11).