Lumican (LUM) is the major leucine-rich keratan sulfate proteoglycan of the corneal stroma, also found in the extracellular matrices of skin, muscle and cartilage. Lum null mice have corneal opacity as well as skin and tendon fragility associated with disorganized and loosely packed collagen fibers (Jepsen et al. 2002, Chakravarti et al. 2003). LUM binds integrin alpha2beta1 (Zeltz et al. 2010), downregulating MMP-14 expression (Niewiarowska et al. 2011).