Integrin α(IIb) (CD41) plays a role in the maintenance of hematopoietic stem cell activity in the mouse embryonic aorta

Integrins are transmembrane receptors that play important roles as modulators of cell behaviour through their adhesion properties and the initiation of signaling cascades. The α(IIb) integrin subunit (CD41) is one of the first cell surface markers indicative of hematopoietic commitment. α(IIb) pairs exclusively with β(3) to form the α(IIb)β(3) integrin. β(3) (CD61) also pairs with α(v) (CD51) to form the α(v)β(3) integrin. The expression and putative role of these integrins during mouse hematopoietic development is as yet unknown. We show here that hematopoietic stem cells (HSCs) differentially express α(IIb)β(3) and α(v)β(3) integrins throughout development. Whereas the first HSCs generated in the aorta at mid-gestation express both integrins, HSCs from the placenta only express α(v)β(3), and most fetal liver HSCs do not express either integrin. By using α(IIb) deficient embryos, we show that α(IIb) is not only a reliable HSC marker but it also plays an important and specific function in maintaining the HSC activity in the mouse embryonic aorta.