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Two International Teams Link Four SNPs to Type 2 Diabetes

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A pair of international research teams have identified four SNPs that may increase the risk of developing type 2 diabetes among Ashkenazi Jewish and Finnish individuals.

The first team, led by Francis Collins, director of the National Human Genome Research Institute, examined polymorphisms on chromosome 20 in 793 Finnish adults diagnosed with typical type 2 diabetes and 413 controls, and identified four SNPs “within and near” the hepatocyte nuclear factor 4 alpha gene.

The researchers learned that the HNF4A gene regulates protein expression in organs such as the liver and pancreas — both of which are involved in type 2 diabetes. In fact, the gene in the beta cells of the pancreas influences the secretion of insulin in response to glucose, whose impairment is a hallmark of the disease.

“It’s a nice coalescence of findings,” Collins said in a statement last week. He said that the mutations found by his group will “raise your risk of type 2 diabetes about 30 percent.” He also stressed there may be other genetic factors — not to mention environmental factors such as obesity — that can increase the risk more.

The second study, led by Alan Permutt of the Washington University School of Medicine in St. Louis, studied 100 SNPs in 275 Ashkenazi Jewish adults in Israel with type 2 diabetes and 342 controls. They found similar disease links with the same four SNPs.

“We believe these four variants are marking a regulatory region that determines the level of expression of HNF4A,” Permutt said in the statement. “We’re now looking to see if this region of DNA is affecting gene expression in some way.”

Both studies, which appear in the April issue of Diabetes, take over where Richard Young of the Whitehead Institute for Biomedical Research left off. In the Feb. 27 issue of Science, researchers suggested how polymorphisms in the HNF4A promoter increase risk for type 2 diabetes. That study, led by Young, found that HNF4A is a “highly active transcription factor,” regulating a “surprising number” of beta cell and liver cell genes in humans. A “misstep” in the binding site for other transcription factors in the HNF4A promoter could result in “misregulation of HNF4A expression and thus its downstream targets, leading to beta cell malfunction and diabetes,” Young’s team concluded.

“The observations made by these groups mark a real leap forward in our understanding of the genetics of diabetes and may provide a blueprint for finding genes in other complex diseases,” said Catherine McKeon of the National Institute of Diabetes and Digestive and Kidney Diseases, which funded all three studies.

Added Collins: “We need to learn much more about this gene and how to modulate its function.”

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