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One man’s junk may be a genomic treasure

Scientists have only recently begun to speculate that what’s referred to as “junk” DNA – the 96 percent of the human genome that doesn’t encode for proteins and previously seemed to have no useful purpose – is present in the genome for an important reason. But it wasn’t clear what the reason was. Now, researchers at the University of California, San Diego (UCSD) School of Medicine have discovered one important function of so-called junk DNA.

Genes, which make up about four percent of the genome, encode for proteins, “the building blocks of life.” An international collaboration of scientists led by Michael G. Rosenfeld, M.D., Howard Hughes Medical Investigator and UCSD professor of medicine, found that some of the remaining 96 percent of genomic material might be important in the formation of boundaries that help properly organize these building blocks. Their work will be published in the July 13 issue of the journal Science.

“Some of the ‘junk’ DNA might be considered ‘punctuation marks’ – commas and periods that help make sense of the coding portion of the genome,” said first author Victoria Lunyak, Ph.D., assistant research scientist at UCSD.

In mice, as in humans, only about 4 percent of the genome encodes for protein function; the remainder, or “junk” DNA, represents repetitive and non-coding sequences. The research team studied a repeated genomic sequence called SINE B2, which is located on the growth hormone gene locus, the gene related to the aging process and longevity. The scientists were surprised to find that SINE B2 sequence is critical to formation of the functional domain boundaries for this locus.

Functional domains are stretches of DNA within the genome that contain all the regulatory signals and other information necessary to activate or repress a particular gene. Each domain is an entity unto itself that is defined, or bracketed, by a boundary, much as words in a sentence are bracketed by punctuation marks. The researchers’ data suggest that repeated genomic sequences might be a widely used strategy used in mammals to organize functional domains.

“Without boundary elements, the coding portion of the genome is like a long, run-on sequence of words without punctuation,” said Rosenfeld.

Decoding the information written in “junk” DNA could open new areas of medical research, particularly in the area of gene therapy. Scientists may find that transferring encoding genes into a patient, without also transferring the surrounding genomic sequences which give structure or meaning to these genes, would render gene therapy ineffective.

Contributors to the paper include Lluis Montoliu, Rosa Roy and Angel Garcia-Díaz of the Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología in Madrid, Spain; Christopher K. Glass, M.D., Ph.D., UCSD Department of Cellular and Molecular Medicine; Esperanza Núñez, Gratien G. Prefontaine, Bong-Gun Ju, Kenneth A. Ohgi, Kasey Hutt, Xiaoyan Zhu and Yun Yung, Howard Hughes Medical Institute, Department of Molecular Medicine, UCSD School of Medicine; and Thorsten Cramer, Division of Endocrinology, UCSD Department of Medicine.

The research was funded in part by the Howard Hughes Medical Institute and the National Institutes of Health.

Contact: Debra Kain
ddkain@ucsd.edu
619-543-6163
University of California – San Diego

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Adding folic acid to flour significantly reduces congenital malformations

This release is also available in French.

Quebec City, July 12, 2007 – Dr. Philippe De Wals of Université Laval’s Department of Social and Preventive Medicine today publishes a study clearly indicating that the addition of folic acid to flours has led to a 46% drop in the incidence of congenital neural tube deformation (mainly anencephaly and spina bifida) in Canada. Such deformations either result in the child’s death or in major health problems, including physical and learning disabilities. Dr. De Wals’s work as head of a team of a dozen Canadian researchers appears today in the New England Journal of Medicine.

The neural tube is the basis of the embryo’s nervous system. Poor development of the neural tube, which is sometimes due to a lack of folic acid, can result in major health problems. Folic acid is found in green vegetables, fruit, whole grains, and meat. However, even a balanced diet won’t supply enough folic acid for a pregnant mother and the child she is carrying. Before1998, Canadian medical authorities were already recommending that women in their child-bearing years consume vitamin supplements containing folic acid. “Canada decided to add folic acid to all flour produced in the country because formation of the neural tube in embryos is particularly intense during the first four weeks of pregnancy, which is before a lot of women even know they’re pregnant. Since half of Canadian pregnancies are unplanned and the human body can’t store folic acid, it is better to integrate folic acid into the food chain than to focus exclusively on taking vitamin supplements,” stated Dr. De Wals. Health Canada still recommends taking folic acid supplements to women in their child-bearing years.

Researchers Dr. Philippe De Wals and Fassiatou Tairou of Université Laval’s Faculty of Medicine compared the incidence of neural tube deformations before and after the introduction of folic acid–enriched flours for over 2 million births in Canada. Between 1993 and 1997, the incidence was 1.58 per 1,000 births. Between 2000 and 2002, the rate dropped 46% to 0.86. The biggest improvement occurred in the parts of Canada that had the highest rates of neural tube deformation before 1998—Newfoundland, Prince Edward Island, and Nova Scotia. In Québec, the drop was also pronounced, but closer to the Canadian average.

Currently, only Canada, the United States, and Chile require that folic acid be added to flour. The effectiveness of this practice, as demonstrated by Dr. De Wals’s team, could encourage other countries to follow suit. Every year, approximately 200,000 cases of spina bifida and anencephaly occur worldwide. Adding folic acid to food could reduce that number by half.

Contact: Martin Guay
martin.guay@dap.ulaval.ca
418-656-3952
Université Laval

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July 12, 2007 Posted by | Alberta, Baltimore, Barcelona, Bethesda, Bone Diseases, Calgary, Chile, Folic Acid, Global, Global Health Vision, Global News, Health Canada, Irvine, Italy, Japan, Medical Journals, Neurology, New England Journal of Medicine, Newfoundland, News, News Australia, News Canada, News Israel, News Italy, News Jerusalem, News Switzerland, News UK, News US, News USA, Nova Scotia, Nutritional Anthropology, Osaka, Ottawa, Pennsylvania, Prince Edward Island, Quebec, Research, Research Australia, RSS, RSS Feed, Slovakia, Spain, Spina Bifida, Toronto, Université Laval, Virginia, WASHINGTON, Washington DC, Washington DC City Feed, World News | 1 Comment