Genetic indicators and susceptibility to osteoarthritis.

A large number of experiments have been performed to identify genetic loci that influence osteoarthritis (OA) susceptibility, with a particular focus on the primary form of the disease. Unfortunately, the currently reported candidate-gene, genome-wide linkage scans and genome-wide association scans have tended to highlight the heterogeneous nature of OA rather than generate statistically compelling genome signals. Nevertheless, some breakthroughs have been made. For example, genetic susceptibility within genes coding for components of the transforming growth factor β pathway has emerged as a particularly interesting find, while completely novel loci are also being uncovered, such as the signal to a cluster of genes on chromosome 7q22. It also appears that quantitative effects on gene expression, rather than qualitative effects on protein function, are particularly important, and that we need to consider the effects of genetic susceptibility in joint formation as much as we do in joint maintenance. Nevertheless, we are still only at the beginning of our search, and much more sophisticated clinical and laboratory approaches will need to be applied before we get a clear understanding of the genetic indicators that influence OA susceptibility.