This proteoglycan is a major component of extracellular matrix of cartilagenous tissues. A major function of this protein is to resist compression in cartilage. It binds avidly to hyaluronic acid via an N-terminal globular region. May play a regulatory role in the matrix assembly of the cartilage. Interacts with COMP (By similarity). Interacts with FBLN1. Specifically expressed in cartilage tissues. Expressed in chondrocytes throughout the developing skeleton in a pattern very similar but not identical to those of type II and IX collagen. In the newborn mouse skeleton it is expressed essentially in a mutually exclusive manner with tenascin, which is expressed osteoblasts, periosteal and perichondrial cells, and in cells at articular surfaces. Two globular domains, G1 and G2, comprise the N-terminus of the proteoglycan, while another globular region, G3, makes up the C-terminus. G1 contains Link domains and thus consists of three disulfide-bonded loop structures designated as the A, B, B' motifs. G2 is similar to G1. The keratan sulfate (KS) and the chondroitin sulfate (CS) attachment domains lie between G2 and G3. Contains mostly chondroitin sulfate, but also keratan sulfate chains, N-linked and O-linked oligosaccharides. Defects in Acan are the cause of cartilage matrix deficiency (CMD). CMD is an autosomal recessive syndrome characterized by cleft palate, short limbs, tail and snout. Mutation in strain CMD causes absence of aggrecan by truncation of the protein (mutation in the G1 domain). Belongs to the aggrecan/versican proteoglycan family. Aggrecan