Scientists from an international consortium have identified a large number of new genetic markers that predispose individuals to lupus.
The study is published in the July 17 issue of the journal Nature Communications and was led by researchers at Wake Forest Baptist Medical Center, Oklahoma Medical Research Foundation, King's College of London and Genentech Inc.
Autoimmune diseases strike one in 15 Americans, are among the top 10 causes of death in women and cost an estimated $100 billion a year in medical care. In autoimmune diseases, the body attacks itself. Systemic lupus erythematosus, the form of lupus studied here, is the most common type of lupus and is a prototypical autoimmune disease.
Lupus strikes women nine times more often than men and its onset is most common during childbearing age. Also, African-American and Hispanic women are two to three times more likely to develop lupus and tend to have more severe cases than Caucasian women. At present, there is no cure for lupus, which can affect many parts of the body, including joints, skin, kidney, heart, lungs, blood vessels and brain, according to the Lupus Research Alliance.
"This study is the largest multi-ethnic lupus genetics study to date and allowed us to identify many new genetic markers, some of which are specific to individual ethnic groups and others that are shared across ethnicities," said Carl Langefeld, Ph.D., lead author of the study and professor of biostatistical sciences at Wake Forest School of Medicine, a part of Wake Forest Baptist. "With this information, we can begin to better understand the differences in the rates and severity of disease across ethnic groups.
"In addition, we observed that many of the genetic markers associated with lupus are shared across numerous autoimmune diseases, and those that are not shared may allow us to understand why a person develops lupus instead of another autoimmune disease. These results will help us identify the biological pathways that pharmaceutical companies may target, and ultimately, develop personalized medicine for the treatment of lupus."
This study analyzed genetic data from 27,574 individuals of European, African American and Hispanic ancestry using the Immunochip, a genotyping technology designed specifically for autoimmune diseases. The researchers identified 58 regions of the genome in Caucasians, nine in African Americans and 16 in Hispanics. These regions appear independent of the well-known Human Leukocyte Antigen (HLA) associations, also studied in depth here. An important observation was that nearly 50 percent of these regions had multiple genetic variants that predispose someone to lupus, Langefeld said.
Another key finding was that as the number of genetic risk variants (alleles) a person has increases, the risk for lupus increases more than expected if the variants were working independently. These observations led the authors to propose a "cumulative hits hypothesis for autoimmune disease".
In future research, the team hopes to better understand how these genetic variants influence the risk of lupus, identify any possible drug targets and determine if any environmental factors, such as infections, can trigger the development of the disease in someone who has a genetic susceptibility. They emphasize that it is important to increase the number of understudied populations, such as African-American and Hispanic, to better understand the genetic causes of health disparities in lupus and the unique risks in all ethnic groups.
"We are delighted to see the work we funded on the ImmunoChip come to fruition and congratulate Dr. Langefeld along with his colleagues on this tremendous success," said Kenneth M. Farber, CEO and President, Lupus Research Alliance. "This study is among the few to concentrate heavily on non-Caucasian populations for a significantly broader evaluation, while utilizing the most current and comprehensive information about human DNA."
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