Implicated in tumor angiogenesis (By similarity). May inhibits BMPs activity by blocking their interaction with their receptors. Has a negative regulator effect on the cartilage formation/regeneration from immature mesenchymal cells, by preventing or reducing the rate of matrix accumulation. May play a role during myoblast and osteoblast differentiation, and maturation. Interacts with GDF5. May interact with INHBA, BMP2, BMP4, BMP5, BMP6, and BMP7. Additional isoforms seem to exist. Differential expression of isoforms was observed during myoblast and osteoblast differentiation and maturation. Weakly expressed in the liver and kidney. In reproductive organs expressed in connective tissues such as ligaments of the ovary and oviduct in females, and of testis, epididymis and certain male accessory sex glands in males. Expression was high in uterine myometrium. Weakly expressed in cartilage of the femoral head, patella, articular facets of vertebrae, in the annulus fibrosus of intervertebral disks. In normal cartilage, expression was confined to articular chondrocytes especially in the superficial zone. In embryo expressed to the surface chondrocytes of developing joint cartilage and to the connective tissue of reproductive organs. According to PubMed:14660436 interacts with human BMP2, BMP4, BMP5, BMP6, BMP7 but not human INHBA. According to PubMed:15094188 interacts with human INHBA but not human BMP2, BMP4 and BMP6.