The function of ENSG00000116690 (PRG4, proteoglycan 4) is as follows. Plays a role in boundary lubrication within articulating joints. Prevents protein deposition onto cartilage from synovial fluid by controlling adhesion-dependent synovial growth and inhibiting the adhesion of synovial cells to the cartilage surface. Isoform F plays a role as a growth factor acting on the primitive cells of both hematopoietic and endothelial cell lineages.