Technology & Science

1st frog genome could help humans

An international team of researchers has sequenced the genome of the western clawed frog, an important model animal in research on embryos and human genetic diseases.

An international team of researchers has sequenced the genome of the western clawed frog, an important model animal in research on embryos and human genetic diseases.

Although biologists have uncovered the DNA sequences of more than 175 organisms so far — from corn to the spotted green puffer fish — this is the first genome of an amphibian to be sequenced.

"A lot of furry animals have been sequenced, but far fewer other vertebrates," said co-author Richard Harland of the University of California, Berkeley, in a statement.

The researchers found that nearly 80 per cent of all human genes associated with genetic diseases have counterparts in the western clawed frog, Xenopus tropicalis.

This discovery could lead to a better understanding of the genetic and chemical basis for many of these human diseases.

The research, published this week in the journal Science, was led by Uffe Hellsten of the U.S. Department of Energy Joint Genome Institute in Walnut Creek, Calif.

Most-studied frog

The western clawed frog, a native of sub-Saharan Africa that lives its entire life in water, is one of the most studied species of frog, used as a model organism in the study of embryo development and cell biology.

The frog genome could also lead to better understand of the evolution of animals.

"When you look at segments of the Xenopus genome, you literally are looking at structures that are 360 million years old and were part of the genome of the last common ancestor of all birds, frogs, dinosaurs and mammals that ever roamed the earth," said Hellsten.

The research could also help the frogs themselves, aiding biologists in their study of the rapidly declining populations of amphibians seen around the world.

The genome of Xenopus tropicalis is composed of more than 1.7 billion chemical base pairs, or "letters," that make up between 20,000 and 21,000 genes.

More than 1,700 of these genes are similar to those in humans that are associated with diseases like cancer, asthma and heart disease.

While Xenopus laevis, a larger evolutionary cousin of X. tropicalis, is arguably a more important animal model for researchers, the Joint Genome Institute focused on X. tropicalis because its genome is simply smaller.

X. tropicalis has two copies of each gene, spread across 10 pairs of chromosomes, while X. laevis has four copies on 18 pairs of chromosomes.

Sequencing the genome of the larger frog could have been more complicated and costlier than doing the project on X. tropicalis.

Harland and his colleagues have applied for a grant to sequence the genome of the larger frog, calling the research published this week a "scaffold upon which to assemble the X. laevis genome."