CRTAC1 is a 661 amino acid secreted protein. CRTAC1 is O-glycosylated and contains one EGF-like domain and four FG-GAP repeats. Up-regulated in mesenchymal stem cells undergoing chondrogenic differentiation and also by growth factor BMP-4, CRTAC1 is found in the interterritorial matrix of articular deep zone cartilage. CRTAC1 is expressed as three isoforms produced by alternative splicing events. All isoforms are expressed in bone, cartilage and lung, while isoforms 1 and 2 are expressed in the brain. The gene that encodes CRTAC1 maps to human chromosome 10, which contains over 800 genes and 135 million nucleotides, making up nearly 4.5% of the human genome.