Both of these proteins have recently been proposed to contribute to TGFβ1 signaling in early cartilage development (Wilson et al., 2012) and alterations within TGFβ1 signaling have been linked to osteoarthritis (van der Kraan et al., 2010), whilst COMP itself has recently been identified as a TGFβ-responsive gene (Li et al., 2011). Here, COMP is linked to osteoarthritis.