Bone morphogenetic proteins (BMPs) are expressed broadly and regulate a diverse array of
developmental events in vivo. Essential to many of these functions is the establishment of
activity gradients of BMP, which provide positional information that influences cell fates.
Secreted polypeptides, such as Noggin, bind BMPs and inhibit their function by preventing
interaction with receptors on the cell surface. These BMP antagonists are assumed to be
diffusible and therefore potentially important in the establishment of BMP activity gradients in …