Binds calcium and plays a role in osteoblast-driven collagen biomineralization activity (By similarity). Critical regulator of TGF-beta in articular cartilage and plays an essential role in cartilage homeostasis and osteoarthritis (OA) pathogenesis. Negatively regulates chondrogenesis in the articular cartilage by blocking the TGF-beta/receptor interaction on the cell surface and inhibiting the canonical TGF-beta/Smad signal. Negatively regulates periodontal ligament (PDL) differentiation and mineralization to ensure that the PDL is not ossified and to maintain homeostasis of the tooth-supporting system. Inhibits BMP2-induced cytodifferentiation of PDL cells by preventing its binding to BMPR1B/BMP type-1B receptor, resulting in inhibition of BMP-dependent activation of SMAD proteins. Inhibits the interaction between TGFB1 and TGF-beta receptor type II in the presence of heparin/heparan sulfate in vitro. Interacts with type I collagen. DCN can inhibit collagen binding (By similarity). Interacts with TGFB1, TGFB2 and TGFB3. DCN, BGN, and FMOD inhibit binding to TGFB1. Interacts with BMP2. Interacts in vitro with type II collagen. Higher expression in heart, also detected in kidney, stomach, testes, and skin but only weakly in lung, skeletal muscle, small intestine, and thymus. Expressed specifically and predominantly in the periodontal ligament (PDL). During tooth development, strong expression is seen in the dental follicle, which is the progenitor tissue that forms cementum, alveolar bone, and the PDL. Expressed in the perichondria of the maxilla, mandible, vertebrae, and long bones. Predominantly expressed in the perichondrium/periosteum of long bones (at protein level). At 12.5 dpc, it is present in the mandibular as well as maxillary components of the first branchial arch. Also detected in the thoracic body wall adjacent to the heart. At 13.5 dpc, it is detected in the mesenchyme lateral to Meckel's cartilage. Pronounced expression is observed in the perichondrium of the humerus, ribs, and scapula. At 14.5 dpc, it is detected in the mesenchymal condensations lateral to Meckel's cartilage, in the perichondrium surrounding the central cartilaginous elements of the vertebra and also in the dermal mesenchyme. At 15.5 dpc, it is expressed in the perichondrium/periosteum of the long bones (i.e. femur, tibia, and fibula), some of the flat bones at the base of the skull (i.e. sphenoid bone), ribs, clavicle, and vertebrae. Also detected in the intramembranous bones of the maxilla and mandible (alveolar bone) and a strong expression is observed in sagittal sections of the subcutaneous muscles or panniculus carnosus of the thorax, trunk, and head/ neck (platysma muscle) region. Very little expression is detected in the major parenchymal organs (with the exception of the large bronchi of the lung). Its expression is prominent in the developing mouse skeleton, particularly in the perichondrium/periosteum of cartilage/bone, and is also found in other specialized connective tissues such as tendon, sclera, the connective tissue sheath surrounding muscle and dermis. In the sclera of the eye it is first detected at 15.5 dpc and stronger expression was detected at 17.5 dpc. By TGFB1. Induction requires ALK5 kinase activity and SMAD3. The repeats LRR 9, LRR 10 and LRR 11 are involved in binding type I collagen. The poly-Asp region is involved in binding calcium (By similarity). The LRR 5 repeat can inhibit BMP2-induced cytodifferentiation and may be involved in the interaction with BMP2. Belongs to the small leucine-rich proteoglycan (SLRP) family. SLRP class I subfamily. Truncated C-terminus.