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Pinpointing a susceptibility gene for type 2 diabetes
  
By
Edward R. Winstead


In the mid-1990s, researchers identified a region of chromosome 2 that appeared to contain a gene involved in type 2 diabetes. They made the discovery by scanning the genomes of a Mexican-American population that has a high incidence of the disease. The suspected chromosomal region contains roughly 1.7 million letters of genetic code.

A team of researchers has pinpointed the gene, calpain 10. The role of calpain 10 is unknown, although the gene may influence glucose levels. According to a paper in the October issue of Nature Genetics, the researchers progressively narrowed the target region using genetic markers, or polymorphisms. The strategy is called positional cloning.

"Our search was not systematic in that we did not use an evenly spaced set of DNA polymorphisms that span the 1.7-Mb interval in our analysis," the researchers write in their paper. "Rather, it was a directed search in that we used the results from each set of analyses to guide us as to which region we should examine next."

If calpain 10 turns out to be a susceptibility gene for type 2 diabetes, it will be one of many. The study, write the authors of a News & Views article, "is a landmark in the decade-long effort to clone genes for polygenic disorders."

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Horikawa, Y. et al. Genetic variation in the gene encoding calpain-10 is associated with type 2 diabetes mellitus. Nat Gen 26, 163-175 (October 2000).
 

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