Noggin is a secreted homodimeric antagonist of bone morphogenetic proteins (BMPs). It binds BMP-4 with high affinity and BMP-7 with lower affinity. Noggin regulates BMP activity in neural tube formation, somite patterning, cardiomyocyte development, and skeletal joint formation. Mutations of human Noggin are linked to multiple types of skeletal dysplasias that result in apical joint fusions. Noggin is expressed in defined areas of the adult central nervous system and peripheral tissues such as lung, skeletal muscle and skin. Noggin may also regulate the differentiation of embryonic stem cells into dopaminergic neurons.