Mammal Genome Project Shines Light on Human DNA
October 12, 2011

Mammal Genome Project Shines Light on Human DNA

By studying the genomes of 29 mammals, scientists have gained greater understanding of how the human genome controls when and where specific genes are activated, as well as how they form proteins and how genetic mutations can lead to diseases.

The study, which was led by Kerstin Lindblad-Toh of the US-based Broad Institute and Sweden's Uppsala University, included work from an international team of scientists, including those at the Human Genome Sequencing Center, the Baylor College of Medicine, the Massachusetts Institute of Technology, the Genome Institute at Washington University, and institutes from Denmark, Austria, and the UK.

"Comparing the genomes of 29 mammals — from humans and primates to the two-toed sloth — provides new understanding of the development of species and the importance of what has remained the same and what has changed during evolution," officials from the Baylor College of Medicine said in a Wednesday press release.

According to that university, the team of bioinformatics, laboratory and genomic experts behind the research successfully created a high-resolution genomic map of over 3.5 million constrained elements. That accounts for roughly 4% of the human genome and includes nearly 3,800 new exons, or genetic information for parts of proteins.

Furthermore, Baylor University reports that the scientists discovered "possible functions" for approximately three-fifths of the chemicals that compose DNA (known as constrained bases), but have yet to discern the functional class of the remaining 40%.

In all, the scientists spend five years sequencing the genomes of the human, chimpanzee, rhesus macaque, tarsier, mouse lemur, bush baby, tree shrew, mouse, rat, kangaroo rat, guinea pig, squirrel, thirteen-lined ground, rabbit, pika, alpaca, dolphin, bottlenosed, cow, horse, domestic cat, domestic dog, little brown bat, fruit bat, European hedgehog, common shrew, African elephant, hyrax, rock, tenrec, nine-banded armadillo, and the two-toed sloth.

"With just a few species, we didn't have the power to pinpoint individual regions of regulatory control," Manolis Kellis, one of the authors of the study and an associate professor of computer science at MIT, said in a statement. "This new map reveals almost 3 million previously undetectable elements in non-coding regions that have been carefully preserved across all mammals, and whose disruptions appear to be associated with human disease."

"By comparing a large number of mammals, scientists have now created a catalogue of millions of regulatory elements found both between and within genes," added Lindblad-Toh. "These elements are incredibly important in making us humans into the complex organisms that we are, even though our genes are rather similar to those of other vertebrates."

Their findings have been published in the latest edition of the journal Nature.

In a separate press release, the Broad Institute said that their research had "discovered the vast majority of the so-called 'dark matter' in the human genome" and that the genetic map that resulted from their work was "a critical step in interpreting the thousands of genetic changes that have been linked to human disease."

"Early comparison studies of the human and mouse genomes led to the surprising discovery that the regulatory information that controls genes dwarfs the information in the genes themselves," representatives from the Institute added. "But, these studies were indirect: they could infer the existence of these regulatory sequences, but could find only a small fraction of them. These mysterious sequences have been referred to as the dark matter of the genome, analogous to the unseen matter and energy that make up most of the universe."


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