Human Genome Yields Up More Secrets
Wednesday, June 13, 2007; 12:00 AM
WEDNESDAY, June 13 (HealthDay News) -- In what's being hailed as a milestone in human genetics research, an international consortium of scientists announced Wednesday new data that could revolutionize how scientists study health and disease.
An exhaustive look at only 1 percent of the human genome produced two major findings: a vast amount of seemingly useless genes formerly called "junk DNA" may, in fact, be crucial to regulatory processes governing cells; and "epigenetic" factors outside of genes are probably big players behind many diseases.
The results of the Encyclopedia of DNA Elements (ENCODE) Project, published in the June 14 issue ofNature, are "moving us into a deeper understanding of how life works and how, sometimes, things go wrong and disease occurs," Dr. Francis Collins, director of the U.S. National Human Genome Research Institute, told reporters at a morning news conference.
The completion of the Human Genome Project in April 2003 was an historic achievement, resulting in a catalog of more than 30,000 genes that make up the species' genetic blueprint. Those genes are comprised of 3 billion individual nucleotides -- labeled A, C, G, or T -- which combine to form genetic code. All of this is packed and bound into chromosomes as material collectively called chromatin.
"This script is written in this apparently simple alphabet with just four letters, but somehow carries within it all of the instructions necessary to take a single-cell embryo and turn it into a very complex biological entity called a human being," said Collins, whose institute is the major source of funding for the $41 million project.
It is one thing to map the whole genome on the "macro" level, the experts noted. But what the ENCODE team -- 35 groups from 80 organizations worldwide -- is seeking to do is examine, in much more detail, just 1 percent of the genome.
About half of this 1 percent involves areas that were known by scientists to influence gene replication and protein coding to make the building blocks of life. The other half was a random sample meant to include other aspects of the genome, including so-called "junk DNA."
"When they first sequenced the genome, [scientists] were surprised at how little DNA was involved in protein coding regions," explained Ewan Birney of the European Bioinformatics Institute in Hinxton, England.
Birney, who headed up the two-and-a-half year analysis of the ENCODE data, noted that just 1.5 percent of the "letters" in the genome actually make cellular proteins. So, his team wondered, what was the other 98.5 percent doing?
"People rather dismissively called the rest of it 'junk DNA,' " he said. But the ENCODE data suggest that this genetic material is, in fact, very active.
"One of the big surprises is that the regions between genes seem to be alive, not only with regulatory regions -- which we suspected -- but also there's a lot of [gene] transcription," Birney said. Transcription is the process whereby DNA transcribes its information into usable proteins.
The researchers also discovered another, less obvious purpose to a lot of genetic material. They noticed that up to 70 percent of "functional regions" in the genomes of both humans and other mammals were what Birney called "neutral." These neutral genetic blips popped up frequently and didn't help or hinder the organism, in terms of activities needed to sustain life.