Integrins are ?/? heterodimeric cell surface receptors that play a pivotal role in cell adhesion and migration, as well as in growth and survival. The integrin family contains at least 18 ? and 8 ? subunits that form 24 known integrins with distinct tissue distribution and overlapping ligand specificities . Integrins not only transmit signals to cells in response to the extracellular environment , but also sense intracellular cues to alter their interaction with the extracellular environment .
Integrin ?6 is a 120 kDa protein with two splice variants, integrin ?6, 6A and 6B , which function as receptors for laminins on the basal membrane to mediate cellular adhesion events . ?6 integrins have been shown to play an important role in hematopoietic stem and progenitor cell homing to the bone marrow.