For example, COMP, a marker for healthy and young discs is prominently localized in the AF compartment (Molinos et al., 2015) and shown to be an inhibitor of vascular calcification (Du et al., 2011), and the proteoglycan aggrecan inhibits apatite growth through Ca2+ binding (Eanes et al., 1992). The gene discussed is ACAN; the disease is atrial fibrillation.