Abstract
Hematopoietic stem cells (HSCs) are defined by their functional ability to self-renew and to differentiate into all blood cell lineages. The majority of HSC reside in specific anatomical locations in the bone marrow (BM) microenvironment, in a quiescent non motile mode. Adhesion interactions between HSCs and their supporting BM microenvironment cells are critical for maintaining stem cell quiescence and protection from DNA damaging agents to prevent hematology failure and death. Multiple signaling proteins play a role in controlling retention and migration of bone marrow HSCs. Adhesion molecules are involved in both processes regulating hematopoiesis and stem- and progenitor-cell BM retention, migration and development. The mechanisms underlying the movement of stem cells from and to the marrow have not been completely elucidated and are still an object of intense study. One important aspect is the modification of expression and affinity of adhesion molecules by stem and progenitor cells which are required both for stem cell retention, migration and development. Adhesion is regulated by expression of the adhesion molecules, their affinity and avidity. Affinity regulation is related to the molecular binding recognition and bond strength. Here, we describe the in vitro FACS assay used in our research to explore the expression, affinity and function of the integrin α4β1 (also termed VLA-4) for murine bone marrow retained EPCR+ long term repopulation HSC (LT-HSC) (Gur- Cohen et al., 2015 ).