Fine-Tuned Map of Human Genome Offers Fresh Clues about Disease

Scientists released the finest-detailed map yet of variants in the human genetic code this week, declaring it should help unlock inherited causes of disease and reveal secrets of evolution.

The “second generation” blueprint of human genetic variation, published in the British journal Nature, unveils minute differences in the genome of 270 people, from Nigeria and Utah to China and Japan.

Individuals are more than 99 percent the same at the genetic level.

Understanding the tiny fraction of material that varies can highlight vulnerability to disease, response to pharmaceutical drugs and reaction to environmental triggers such as ozone pollution and pollen.

These variants are usually inherited as small blocks of genetic code, called haplotypes.

A first version of the so-called HapMap, published in 2005, uncovered around one million single variants in the genetic code, known as single nucleotide polymorphisms (SNPs, often shorthanded to “Snips”).

The higher-resolution update boosts the tally to more than 3.1 million SNPs, according to the compilers, gathered in the International HapMap Consortium.

This will boost compare-and-contrast power to investigators seeking to understand why some individuals are prone to a specific ailment while others are immune to it, and why some respond well to a given drug while others react badly.

“Researchers around the globe have now associated more than 60 common DNA variants with risk of disease or related traits, with most of the findings coming in the past nine months,” Britain’s Oxford University, which took part in the project, said in a press release.

SNPs, or combinations of them, have already been fingered this year as increasing the risk of coronary artery disease, Crohn’s disease, rheumatoid arthritis and diabetes, it said.

In a separate study, also published in Nature, scientists at the Broad Institute in Cambridge, Massachusetts, used the new HapMap data to identify two genes in a group of people from Yoruba, Nigeria, that had been shaped by evolutionary pressure.

The two genes, called LARGE and DMD, are control cell receptors that are docking points for the Lassa virus.

Exposure to this pathogen in Nigera, where the disease is endemic, caused SNP changes in LARGE and DMD that were not seen in samples from populations elsewhere in the world.

Similar hallmarks were found in two genes involved in skin pigmentation in people of European ancestry, as were two genes involved in the development of hair follicles in Asians.

“Our analysis only scratches the surface of the recent selective history of the human genome,” the authors add.

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