Genetics of osteoarthritis
In this chapter we outline the approaches which have been adopted to identify genetic variants predisposing to osteoarthritis (OA), a condition long recognized as having a heritable component. Such routes to their identification include examining mendelian traits in which OA is a feature, candidate gene studies based on knowledge of OA pathobiology, linkage analysis in related individuals, and, more recently, genome-wide association studies in large samples of unrelated individuals. It is increasingly evident that the main symptom deriving from OA—notably joint pain—also has a genetic basis but this is differs from that underlying OA. Variants convincingly shown to predispose to OA lie in the GDF5 and MCF2L genes and in the chr7 cluster mapping to the COG5 gene, in addition to the ASPN gene in Asian populations. Those associated with pain in OA include TRPV1 and PACE4. Epigenetic influences are also being explored in both the pathogenesis of OA and the variation of pain processing.