HAPLN4 is a 360 amino acid protein encoded by the human gene HAPLN4. HAPLN4 belongs to the HAPLN family and contains 1 Ig-like C2-type (immunoglobulin-like) domain and two Link domains. HAPLN4 mediates the binding of complexes containing hyaluronic acid. HAPLN2 mediates a firm binding of versican V2 to hyaluronic acid. HAPLN4 is believed to play a pivotal role in the formation of the hyaluronan-associated matrix in the central nervous system (CNS), which facilitates neuronal conduction and general structural stabilization. HAPLN4 may also be involved in the formation of extracellular matrices contributing to perineuronal nets and facilitate the understanding of a functional role of these extracellular matrices. HAPLN4 is widely expressed with highest levels in spleen and placenta.