A critical regulatory role of hematopoietic stem cell vascular niches in the bone marrow has been implicated to occur through endothelial niche cell expression of KIT Ligand. However, endothelial-derived KIT Ligand is expressed in both a soluble and membrane-bound form, and not unique to bone marrow niches and is also systemically distributed through the circulatory system. Here we confirm that upon deletion of both the soluble and membrane-bound form of endothelial-derived KIT …