Genes provide clue to frog’s origin

An international team of researchers, including scientists from the Harry Perkins Institute of Medical Research, have decoded the genetic sequence of the African clawed frog, an important model system for cell and developmental biology, and immunology.

Ryan Lister and Ozren BogdanovicThe study, published in the journal Nature, showed that this peculiar animal arose from an ancient combination of genes from two different frog species 18 million years.

The study revealed that the frog arose from the mating of two species, resulting in a “duplicated” genome, whereby the frog carries genetic material from two species.

Interestingly, certain portions of the “duplicated” genome appear to be evolving at different rates.

Dr Ozren Bogdanovic and Professor Ryan Lister from the Perkins Epigenetics and Genomics Laboratory collaborated on the international project.

“Genome duplication is a really important event in evolution, because it generates extra copies of all the genes and control sequences in the genome.” Professor Lister said.

“Through mutation of these extra copies, new molecular activities or patterns of gene use in the organism can arise, creating new functions that are important for evolutionary diversification”.

The two Australian researchers contributed to the project by mapping the frog’s epigenome.

“We mapped the precise genomic locations of an important biochemical signal, called DNA methylation, in the frog genome,” said Dr. Bogdanovic.

“DNA methylation can be thought of as tiny chemical signposts that cells add to their genome. It has the ability to switch genes “on” and “off” during embryo development and disease formation”

The study shows that DNA methylation played one of the most important roles in fine-tuning the levels of gene products making sure that proteins are produced at the correct levels despite the duplication of the genome sequence.

“This is a very important step towards our understanding of how genomes evolve and how genetics and epigenetics shape life on earth.” Dr. Bogdanovic said.

“The work also emphasises the importance of international collaboration and basic research on more “exotic” model organisms such as frogs or fish, as compared to mice and rats”.

The international collaboration included researchers from the United States, Japan, Korea, the Netherlands, Australia, and Switzerland, and was led by Daniel Rokhsar and Richard Harland of the University of California, Berkeley, and Masanori Taira of the University of Tokyo.

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