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Surprising genetic connections between humans and hydras

Erin Podolak

Two teams studying the hydra genome have revealed several surprising genetic similarities between the simple freshwater organism and humans.

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The hydra genome has more similarities with the human genome than once thought, according to two research teams studying the freshwater organisms. One of the projects was an international effort to sequence the genome of hydra, led by biologists Robert Steele, associate professor and interim chair of biological chemistry and Hans Bode, professor of developmental and cell biology from University of California (UC), Irvine. The other effort, from a team from UC Santa Barbara, conducted the research on whether hydras have genes that code for sight.

Hydra vulgaris, a hydrozoan cnidarian. Light microscope, 40x. Source: Wikipedia Commons, Corvana
Since they are relatively simple organisms, hydras—a type of freshwater polyp—are a popular model for biological research. The relatively simple organism belongs to the phylum cnidarian, which emerged approximately 600 million years ago. Evolutionary biologists use modern-day hydras to study the evolution of traits from simple to more complex organisms.

The ancient sense of sight
Recent research from UC Santa Barbara has determined the genetic pathway that enables hydras to respond to light stimuli.

Although hydras do not have eyes like more complex organisms, they can still respond to light. The research team, led by Todd Oakley, an assistant professor in the department of ecology, evolution, and marine biology, sought to identify the biological mechanisms that enable hydra to “see.”

“We determined which genetic ‘gateway’—or ion channel—in the hydra is involved in light sensitivity,” said Oakley in a press release. “This is the same gateway that is used in human vision.”

According to Oakley, the gene opsin controls the entrance and exit of ions through the channel, starting the processes of igniting a neural impulse in response to visual stimuli. Previous researchers have identified the same gene in more complex visual systems.

“This work continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle,” said Oakley. “Instead, it illustrates how all organisms—humans included—are a complex mix of ancient and new characteristics.”

The paper, “The evolution of phototransduction from an ancestral cyclic nucleotide gated pathway,” was published March 10 in Proceedings of the Royal Society B.

Surprises in the sequence
The UC Irvine team sequenced the hydra genome due to the valuable insight the organism may provide into regeneration and stem cell growth. Hydras, like other cnidarians, have the ability to regenerate lost tissue, which makes them ideal for studies in these fields. Through sequencing, Steele and Bode discovered that hydras have the same number of genes as humans, and—like other previously sequenced organisms (including dogs and mice)—a large portion of these genes are similar to those of humans. The researchers were also surprised to find genes involved in Huntington’s disease and Alzheimer’s disease present in the hydra sequence.

“Having the hydra genome sequenced enhances our ability to use it to learn more about the basic biology of stem cells, which are showing great promise for new treatments for a host of injuries and diseases,” said Steele in a press release.

The hydra genome project began in 2004, and included researchers from the J. Craig Venter Institute. Funding for the project was provided by the National Human Genome Research Institute. The paper, “The dynamic genome of hydra,” was published March 14 in Nature.