Stem cell factor (SCF) is a potent hematopoietic growth factor required in regulating both embryonic and adult hematopoiesis. SCF protein promotes the survival, differentiation, and mobilization of multiple cell types including myeloid, erythroid, megakaryocytic, lymphoid, germ cell, and melanocyte progenitors [1, 7]. SCF is a primary growth and activation factor for mast cells and eosinophils [8]. And SCF assists in the recovery of cardiac function following myocardial infarction by increasing the number of cardiomyocytes and vascular channels [9]. Stem cell factor is an important cytokine for ex vivo clinical applications. Along with other cytokines, SCF is used in the culture and expansion of hematopoietic stem cells (HSCs) as well as for proliferation and differentiation of both myeloid and erythroid progenitor cells. Mature stem cell factor consists of a 189 amino acid (aa) extracellular domain (ECD), a 23 aa transmembrane domain, and a 36 aa cytoplasmic tail [10]. The ECD shows both N linked and O-linked glycosylation [11]. SCF protein exists in two forms, a membrane-bound form and a proteolytically processed soluble form that lacks the transmembrane domain and cytoplasmic tail. The soluble form is created by proteolytic cleavage at two alternate sites in the extracellular juxtamembrane region releasing a 25 kDa soluble SCF protein which is comparable to the only form produced by Steel-dickie mutant mice [12, 13]. There is also an alternately spliced isoform of human SCF that lacks 28 amino acids that encompasses the primary proteolytic recognition site [14].
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