May inhibit 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 (By similarity). Implicated in tumor angiogenesis. May play a role during myoblast and osteoblast differentiation, and maturation. Interacts with GDF5 (By similarity). May interact with BMP2, BMP4, BMP5, BMP6, BMP7 and INHBA. Five additional mRNAs also exist. Differential expression of isoforms was observed during myoblast and osteoblast differentiation and maturation. Highly expressed in uterus. Moderately expressed in heart, liver, prostate, testis and ovary. Weakly expressed in skeletal muscle, kidney, spleen, small intestine and colon. Expressed in the secretory epithelial cells of uterine endometrium, fallopian tubes, endocervical glands, bladder and prostate, as well as the transitional epithelium of the urinary bladder, and in bone osteoblasts (at protein level). In normal cartilage, expression was confined in a few chondrocytes in the superficial zone as well as in the middle zone. In diseased cartilage coming from osteoarthritic patients, expression was limited to the middle zone of chondrocytes. Isoform 1 and isoform 2 are expressed in fetal cerebellum and heart, while only isoform 2 is detected in fetal spleen. Isoform 2 present in plasma. Up-regulated in breast tumors but also in lung and colon tumors. Phosphorylated by FAM20C in the extracellular medium. According to PubMed:14660436, interacts with BMP2, BMP4, BMP5, BMP6, BMP7 but not INHBA. According to PubMed:15094188, interacts with INHBA but not BMP2, BMP4 and BMP6.