Genome of ancient sponge reveals origins of first animals, cancer

The sponge, which was not recognised as an animal until the 19th century, is now the simplest and most ancient group of animals to have their genome sequenced.

 
An adult sponge of the species Amphimedon queenslandica living with an octocoral off Australia's Great Barrier Reef.
CREDIT: (Maely Gauthier photo)

In a paper appearing in the August 5 issue of the journal Nature, a team of researchers led by Daniel Rokhsar of the University of California, Berkeley, and the Department of Energy's Joint Genome Institute (JGI), report the draft genome sequence of the sea sponge Amphimedon queenslandica and several insights the genome gives into the origins of both the first animals and cancer.

All living animals are descended from the common ancestor of sponges and humans, which lived more than 600 million years ago. A sponge-like creature may have been the first organism with more than one cell type and the ability to develop from a fertilised egg produced by the merger of sperm and egg cells – that is, an animal.

"Our hypothesis is that multicellularity and cancer are two sides of the same coin," said Rokhsar, programme head for computational genomics at JGI and a professor of molecular and cell biology and of physics at UC Berkeley.

"If you are a cell in a multicellular organism, you have to cooperate with other cells in your body, making sure that you divide when you are supposed to as part of the team. The genes that regulate this cooperation are also the ones whose disruption can cause cells to behave selfishly and grow in uncontrolled ways to the detriment of the organism."

As part of the new analysis, the team looked in the sponge genome for more than 100 genes that have been implicated in human cancers and found about 90 percent of them. Future research will show what roles these genes play in endowing sponge cells with team spirit.