UCLA and Finnish scientists identify genetic mutation that causes lactose intolerance

January 14, 2002

UCLA and Finnish researchers have identified a genetic mutation for lactose intolerance, a painful digestive condition that afflicts some 30 million to 50 million North Americans, 75 percent of African Americans and 90 percent of Asian Americans. The findings are reported in the Jan. 14 issue of Nature Genetics.

Dr. Leena Peltonen, UCLA's Gordon and Virginia MacDonald Distinguished Chair in Human Genetics, and her associates at the UCLA School of Medicine, collaborated with colleagues at Finland's National Public Health Institute to identify a DNA variant outside of the gene associated with lactose intolerance.

Lactose intolerance occurs in children after weaning, when the cells that line the small intestine decrease their production of an enzyme called lactase-phlorizin. For years, scientists' analyses of the human gene that encodes this enzyme revealed no mutation associated with the disorder. As a result, Peltonen's team looked for a DNA variant outside of the encoding gene.

The researchers drew blood samples in order to study the DNA of a Finnish group of 196 lactose-intolerant adults of African, Asian and European descent. Each of them showed the genetic mutation for lactose intolerance in their DNA.

"That we found the same DNA variant in all lactose-intolerant people across distant ethnic groups indicates to us that it is very old," Peltonen said. "We believe that the variant we identified in patients is the original form of the gene -- which mutated to tolerate milk products when early humans adopted dairy farming.

"This suggests that everyone was originally lactose intolerant," she added. "It's an excellent example of a useful mutation in human history."

Lactose intolerance is the inability to digest large amounts of lactose -- the main sugar found in dairy products. Symptoms include nausea, cramps, bloating, gas and diarrhea, which begin about 30 minutes to 2 hours after consuming foods containing lactose.

Current tests for lactose intolerance are unreliable or tedious. Peltonen and her colleagues' findings will help speed the development of non-invasive, reliable diagnostic tests and better treatment for this common problem.

University of California - Los Angeles

Related DNA Articles from Brightsurf:

A new twist on DNA origami
A team* of scientists from ASU and Shanghai Jiao Tong University (SJTU) led by Hao Yan, ASU's Milton Glick Professor in the School of Molecular Sciences, and director of the ASU Biodesign Institute's Center for Molecular Design and Biomimetics, has just announced the creation of a new type of meta-DNA structures that will open up the fields of optoelectronics (including information storage and encryption) as well as synthetic biology.

Solving a DNA mystery
''A watched pot never boils,'' as the saying goes, but that was not the case for UC Santa Barbara researchers watching a ''pot'' of liquids formed from DNA.

Junk DNA might be really, really useful for biocomputing
When you don't understand how things work, it's not unusual to think of them as just plain old junk.

Designing DNA from scratch: Engineering the functions of micrometer-sized DNA droplets
Scientists at Tokyo Institute of Technology (Tokyo Tech) have constructed ''DNA droplets'' comprising designed DNA nanostructures.

Does DNA in the water tell us how many fish are there?
Researchers have developed a new non-invasive method to count individual fish by measuring the concentration of environmental DNA in the water, which could be applied for quantitative monitoring of aquatic ecosystems.

Zigzag DNA
How the cell organizes DNA into tightly packed chromosomes. Nature publication by Delft University of Technology and EMBL Heidelberg.

Scientists now know what DNA's chaperone looks like
Researchers have discovered the structure of the FACT protein -- a mysterious protein central to the functioning of DNA.

DNA is like everything else: it's not what you have, but how you use it
A new paradigm for reading out genetic information in DNA is described by Dr.

A new spin on DNA
For decades, researchers have chased ways to study biological machines.

From face to DNA: New method aims to improve match between DNA sample and face database
Predicting what someone's face looks like based on a DNA sample remains a hard nut to crack for science.

Read More: DNA News and DNA Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.