It's not just our DNA that makes us susceptible to disease and influences its impact and outcome. Scientists are beginning to realize more and more that important changes in genes that are unrelated to changes in the DNA sequence itself – a field of study known as epigenetics – are equally influential. A research team at the University of California (UC), San Diego – led by Dr. Gary S. Firestein, professor in the Division of Rheumatology, Allergy, and Immunology at UC San Diego School of Medicine – investigated a mechanism usually implicated in cancer and in fetal development, called DNA methylation, in the progression of rheumatoid arthritis (RA). The researchers found that epigenetic changes due to methylation play a key role in altering genes that could potentially contribute to inflammation and joint damage. Their study was published online on June 26, 2012 in the Annals of the Rheumatic Diseases. "Genomics has rapidly advanced our understanding of susceptibility and severity of rheumatoid arthritis," said Dr. Firestein. "While many genetic associations have been described in this disease, we also know that if one identical twin develops RA that the other twin only has a 12 to 15 percent chance of also getting the disease. This suggests that other factors are at play – epigenetic influences." DNA methylation is one example of epigenetic change, in which a strand of DNA is modified after it is duplicated by adding a methyl group to any cytosine molecule (C) – one of the 4 main bases of DNA. This is one of the methods used to regulate gene expression, and is often abnormal in cancers and plays a role in organ development.
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