Sponge Genome Can Shed Light on Origin of Animals

By Aaida Samad

While household sponges are degraded to the dirty job of scrubbing grime off of kitchen counter tops, the recently sequenced genome of a marine sponge could increase the understanding of the origins of animals as well as cancer, according to a new study.

A team of scientists – led by Daniel Rokhsar, UC Berkeley professor of molecular cell biology and physics and program head for computational genomics at the U.S. Department of Energy’s Joint Genome Institute – assembled a draft genome sequence of the Amphimedon queenslandica, a sponge native to the Great Barrier Reef, which researchers said provides insight into how animals evolved to become more complex organisms.

“What is particularly interesting about the sponge is that it is the most basal of all animals,” said Kenneth Kosik, Harriman Professor of Neuroscience Research at UC Santa Barbara and co-director of its Neuroscience Research Institute, who co-wrote the study. “There was some common ancestor on this earth around 650 million years ago, and its progeny branched off to become all of the animal kingdom. The first creature that branched off from this first animal is some ancestor of the modern sponge.”

By comparing the sponge genome – which was presented in an article published Thursday in the scientific journal Nature – to that of other animals such as humans and fruit flies, scientists can work on reconstructing the genome of organisms’ common ancestor, said Mansi Srivastava, a postdoctoral associate at the Whitehead Institute for Biomedical Research in Cambridge, Mass. More specifically, the genome tells scientists about the genetic toolkit that all animals initially possessed, she said.

“Sponges are generally seen as the oldest surviving lineage coming from a common ancestor, so what this sequence gives us is a breadth of comparison across all animals that is remarkable,” she said. “For a scientist to know definitively about a common ancestor, it is crucial to have the sequence of a sponge.”

Besides advancing scientists’ understanding of the common ancestor of sponges and humans, the genome also provides some interesting insights into cancer mechanisms, she said.

“For a long time people thought of sponges as the simplest animal, but in our studies we found genes associated with complex biological processes like cell division, cell growth and cell adhesion present in sponges,” Srivastava said. “What jumped out at us when we were looking at biological processes … was that a lot of genes involved in human cancers ended up being in the sponge genome.”

In looking at more than 100 genes that can mutate and cause cancer, researchers found that 90 percent of them were in the sponge genome, according to Srivastava. This emphasized the fact that cancer is a disease of multicellularity, she said.

Multicellularity involves the evolution of mechanisms that regulate cell cooperation, according to Steven Martin, chair of UC Berkeley’s molecular and cell biology department. In cancer, those mechanisms go awry and the cell starts to proliferate as if it were a unicelluar organism, disregarding rules that are critical for proper functioning, he said.

“If we ask the question what is the function of these genes in sponges, it might tell us the original function of these genes in animals,” Srivastava said. “What we hope is that with this genome available, we can learn more about how these genes operate in humans to cause cancer.”

Read more here: http://www.dailycal.org/article/109964/sponge_genome_can_shed_light_on_origin_of_animals
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