Repulsive Guidance Molecule B (RGMB) is primarily expressed in the central nervous system. RGM A and B both appear at every level of the developing neural axis, where they colocalize to a large extent in the mantle layer, although only RGMA appears in the neuroepithelium, and only RGMB in the peripheral nervous system. During development, both RGMA and B appear also in lung and in limb cartilage, while RGMB has additional expression domains in pancreas.