Hematopoiesis is maintained throughout the lifetime of an organism by a specialized group of rare cells known as the hematopoietic stem cells (HSCs). These cells are defined by their ability to self-renew to give rise to similar daughter HSCs, and to differentiate into all the lineages of blood cells. The region where HSCs reside to fulfil these tasks is known as the stem cell niche. In a niche, neighboring subsets of cells and extracellular substrates house stem cells and provide specialized signals to modulate stem cell self renewal and progeny production. Many studies have identified key...