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Identification of a variant associated with adult type hypolactasia
What this study accomplished

Researchers identified a genetic variant linked to lactose intolerance.

Why it's important

In the hunt for genetic explanations for lactose intolerance, also known as lactase non-persistence or adult-type hypolactasia, Finnish researchers may have found an intriguing quirk of human history imprinted in our genes. To find the genetic basis for lactose intolerance, the inability to digest milk protein, researchers looked at nine Finnish families who had this condition. The researchers focused on an area on chromosome 2 near the LCT gene, which encodes the protein responsible for digesting lactose. Previous sequence analysis revealed no variants in the coding or promoter regions of the LCT gene that correlate with lactose intolerance.

The researchers compared the DNA sequence of the 2q21 region in seven of the extended Finnish family members; three were lactose intolerant and four were lactose tolerant. They identified 52 variants in the region, which were typed in 196 members of the Finnish extended families, as well as in 236 lactose tolerant and intolerant individuals from four other populations. Researchers measured lactase activity in intestinal biopsy samples to verify the diagnosis of lactose intolerance. They found that the C/T-13910 variant was strongly associated with lactose intolerance in both sets of individuals. This variant is located in the MCM6 gene but does not encode a change in the resulting protein; researchers hypothesize that this variant may have a long-range regulation effect on the LCT gene.

By the genetic evidence, researchers surmised that this trait was very old, dating from the introduction of dairy culture about 10,000 to 8,000 B.C. The percentage of the population that has the genetic variant associated with lactose intolerance varies tremendously by geographic distribution, from less than 5 percent in northern Europe to almost 100 percent in Southeast Asia.

More: To read an abstract of this paper on PubMed, a medical database, click here.