The RGM/DRAGON family of BMP co-receptors

The BMP signaling pathway controls a number of cell processes during development and in adult tissues. At the cellular level, ligands of the BMP family act by binding a hetero-tetrameric signaling complex, composed of two type I and two type II receptors. BMP ligands make use of a limited number of receptors, which in turn activate a common signal transduction cascade at the intracellular level. A complex regulatory network is required in order to activate the signaling cascade at proper times and locations, and to generate specific downstream effects in the appropriate cellular context.One such regulatory mechanism is the repulsive guidance molecule (RGM) family of BMP co-receptors. This article reviews the current knowledge regarding the structure, regulation, and function of RGMs, focusing on known and potential roles of RGMs in physiology and pathophysiology.