Human WARP shares 79% amino acid identity with mouse Warp. RT-PCR of mRNA from various mouse tissues and cell lines detected Warp expression only in chondrocytes. Northern blot analysis confirmed expression of Warp in chondrocytes isolated from newborn mouse rib cartilage.

Western blot analysis of transfected human embryonic kidney cells detected a 48-kD protein in both cell layer and media fractions. The majority of the protein was detected in the medium, indicating that WARP is efficiently secreted. Under nonreducing conditions, a 102-kD form was detected, suggesting that WARP forms a disulfide-bonded homodimer. N-glycosidase digestion led to a mobility shift from 48 to 45 kD, indicating that WARP has 1 or more N-linked oligosaccharide chains.