Rockel JS et al. - Sox9 and p300 co-operate to induce expression of cartilage-specific matrix proteins, including type II collagen, aggrecan and link protein. Tumor necrosis factor-a (TNF-a), found in arthritic joints, activates NF-kB, whereas retinoic acid receptors (RARs) are activated by retinoid agonists including all-trans retinoic acid (atRA)