Once organisms are fully developed, stem cells are the basis for replenishing cells that wear out or are otherwise destroyed in the normal course of living. Researchers are now looking for ways of identifying and manipulating stem cells to regenerate organs or tissues such as heart muscle, liver, brain or the surface of the lung and digestive tract that have degenerated due to disease. The most well studied stem cells to date, are hematopoietic stem cells, which are produced in the bone marrow and are the precursors from which all blood cells develop. Dr. Kelly McNagny’s laboratory discovered MEP21, a molecule that appears to have a close connection to stem cells since its activation correlates closely with the appearance of stem cells in tissues. This suggests that the molecule may be involved in stem cell production and the processes by which stem cells grow differentially to become a specific type of tissue. Dr. McNagny’s research has shown that MEP21 is required for survival – i.e., mice lacking the molecule die shortly after birth. He is now studying its role in activating adult stem cells, with the goal of finding new ways of purifying and using stem cells to regenerate tissues.