A protein used by blood stem cells to adhere to bone marrow could offer a way to improve the success of blood stem-cell transplants.

Certain illnesses, such as some blood cancers, have long been treated with blood — or haematopoietic — stem-cell transplants, but the procedure is risky. To learn more about how to manipulate these cells, Camilla Forsberg at the University of California, Santa Cruz, and her colleagues studied the Robo4 protein.

They found that, in mice, haematopoietic stem cells lacking Robo4 were fewer in number, and less able to anchor themselves in the bone marrow after transplantation. The authors also revealed that Robo4 works with another protein, Cxcr4, to localize transplanted stem cells to the bone marrow.

Cell Stem Cell 8, 72–83 (2011)