Stem cell factor (SCF) is a hematopoietic growth factor that exerts its activity by signaling through the c-Kit receptor. SCF and c-kit are essential for survival, proliferation and differentiation of hematopoietic cells committed to the melanocyte and germ cell lineages. Human SCF manifests low activity on murine cells, while murine and rat SCF are fully active on human cells. Recombinant murine SCF is an 18.3kDa polypeptide containing 164 amino acid residues, which corresponds to the sequence of the secreted soluble form of SCF.