August 31, 2011
Researchers Produce First Lizard Genome Sequence
Researchers have produced the first genome sequence of a lizard.The green anole lizard is the first non-bird species of reptile to have its genome sequenced and assembled.
Researchers have assembled and analyzed over 20 mammalian genomes, but the genetic landscape of reptiles remains relatively unexplored.
"Sometimes you need to be at a certain distance in order to learn about how the human genome evolved," Jessica AlfÃ¶ldi, co-first author of the paper and a research scientist in the vertebrate genome biology group at the Broad Institute, said in a press release. "You have to look out further than you were looking previously."
Lizards are more closely related to birds than to any of the other organisms whose genomes have been sequenced in full.
"People have been sequencing animals from different parts of the vertebrate tree, but lizards had not been previously sampled," Kerstin Lindblad-Toh, scientific director of vertebrate genome biology at the Broad and senior author of the paper, said in a statement. "This was an important branch to look at."
Four hundred species of anole lizards have fanned out throughout the islands of the Caribbean, North America, Central America, and South America.
"Anoles are rich in ecology and morphology and have just the right amount of diversity to make them interesting yet tractable to study," Jonathan Losos, an author of the paper, professor at Harvard University, said in a statement.
"But a big stumbling block in studying them has been that they have not been great organisms for classical genetic study. The genome is going to revolutionize our ability to study that aspect of their evolutionary diversification."
The newly sequenced genome may help resolve where the origin of conserved, non-coding elements in the human genome lie.
Scientists have wondered where these elements came from and believe they may be the relics of transposons.
"Anoles have a living library of transposable elements," AlfÃ¶ldi said in a statement.
The lizard's genome also offers up clues about how lizard species evolved to populate islands in the Greater Antilles.
Anoles adapted to fill all of the geological niches the islands have to offer, and some lizards have short legs and can walk along narrow twigs. Other lizards are green in color with big toe pads suited for living in trees, and some are yellow and brown and live in the grass.
"These lizards have been compared to Darwin's finches and in many respects they are similar," Losos said in a press release. "They show the workings of natural selection as species adapted to different habitats. But the difference is in the case of the lizards, this evolution has happened four times, once on each of the different islands."
The researchers were able to make a preliminary map of how these species evolved to colonize the islands by sampling the genomes of over 90 species.
"This is setting the stage for the research community to be able to look for signatures of adaptation in a very informative and well thought through way," Lindblad-Toh said in a statement.
The researchers also performed the first analysis of several other features in the anole genome, including micro chromosomes, which are tiny chromosomes sometimes found in reptiles, amphibians, and fish.
The team also found a lack of isochores, which are regions of the genomes with high or low concentrations of the nucleotides "G" and "C".
The research was reported in the journal Nature on August 31.
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