COMP and chondrodysplasia: Disorganization of growth plate chondrocytes and distended ER are characteristics of several chondrodysplasias [16–18], many of which are caused by mutations in genes encoding ECM proteins, such as collagens II, IX, XI, cartilage oligomeric matrix protein (COMP), and aggrecan (reviewed in [19]) and that result in the synthesis of abnormal proteins.