Promotes matrix assembly (PubMed:18757743). Involved in the organization of skeletal muscles and in the formation of neuromuscular junctions (By similarity). Homodimer or homomultimer; disulfide-linked. Interacts with HSPG2. Expressed at high levels in the chondrocytes. Detected in the vasculature of neural tissues, in basement membrane structures of the peripheral nervous system, in the apical ectodermal ridge of developing limb buds, and in skeletal and cardiac muscle (at protein level). Restricted to the presumptive articular cartilage zone prior to joint cavitation and to the articular cartilage and fibrocartilaginous elements in the joint, spine and sternum during embryonic development. Detected from 9.5 dpc in the vasculature of the central nervous system. At 16.5 dpc, present in intervertebral disks of the spinal cord, lip epithelium and developing oral and tooth germ epithelia (at protein level). N-glycosylated.