Water flea offers key scientific info.
By Grace Afsari Mamagani, The Dartmouth Staff
Published on Monday, February 21, 2011
Despite its size, Daphnia pulex — a crustacean less than a few millimeters in length — may revolutionize scientists’ understanding of the relationship between genes and the environment, according to a paper written by members of the Daphnia Genomics Consortium, an international group that includes Dartmouth researchers. “The Ecoresponsive Genome of Daphnia pulex,” published in the Feb. 4 issue of Science, was written by researchers from the Consortium, led by John Colbourne, associate director of the Center for Genomics and Bioinformatics at Indiana University.
Daphnia pulex, or the water flea, became the first crustacean to have its genome sequenced in July 2007 following efforts by the Consortium. The water flea’s reproductive patterns and ability to respond to environmental stressors first sparked researchers’ interest in the organism, according to Thomas Hampton, a bioinformatics specialist at Dartmouth Medical School.
“If you’re looking at the effects of pollution in the water, you can’t beat [studying] Daphnia,” Hampton said. “You give them some scary signal and see if they run away — they’re kind of like little mice.”
The water flea genome, which includes approximately 31,000 genes — about 8,000 more than the human genome — is closer to that of humans than other invertebrate models, according to Joseph Shaw, a professor at the Indiana University School of Public and Environmental Affairs and a former DMS research associate.
Knowledge obtained from the sequencing “has a huge ability” to impact scientists’ understanding of toxicity testing and other environmental processes, Shaw said.
Understanding the water flea genome will enable researchers to examine processes like “physiological acclimation to changing environments” on a genetic scale, which will provide insight into the relationship between environmental stressors and human health, according to the Consortium’s website.
Consortium researchers have begun to appreciate the role played by the environment in the expression of organisms’ genes, according to Shaw.
“It’s not just your genes, it’s your genes in the context of the environments you’re in, and your past environments as well,” Shaw said.
Organizations like the Environmental Protection Agency can use this knowledge to promote policy changes such as lowering acceptable levels of certain toxins in drinking water, Hampton said.
Using information provided by the water flea genome, researchers can monitor which genes turn on or off when faced with various environmental pollutants, he said.
“With these much more sensitive tools, they can make a case much earlier, before bad things happen,” he said.
Since water fleas reproduce by parthenogenesis — a form of asexual reproduction that does not require male genetic material — researchers can experiment on groups of organisms that are genetically identical, according to Hampton.
Under certain environmental conditions, water fleas also lay eggs that do not undergo direct development, allowing them to remain hidden in sediment for hundreds of years, according to Shaw. “We’re able to look at how that population has changed and how that variation has partitioned,” Shaw said. “We can look at evolution happening directly.”
The Consortium currently consists of 475 scientists who have conducted a series of studies on the water flea’s genetic responses to environmental changes, according to its website.
Early experiments on the organism’s physiological reactions to environmental stressors were conducted by Shaw, biological sciences professor Celia Chen, biological sciences professor and Provost Carol Folt and chief academic and scientific officer of the Marine Biological Laboratory and former DMS toxicology professor Joshua Hamilton, according to the College’s website. The “greatest outcome” of the Daphnia project has been the creation of the Consortium, which brings together “the appropriate minds” to apply new knowledge and collaborate on the “big questions” of science, Shaw said.
“It’s one thing to get a genome sequence,” Shaw said. “This would happen — sequencing’s getting cheaper, functional tools would develop. What’s making this unique is this Consortium.”
The collaboration between scientists in different fields enables members to share their knowledge and expand the project’s usefulness, according to Hampton.
“Suppose you give Daphnia some toxin and the gene changes, but you don’t know what the gene is,” Hampton said. “When [researchers] get together in a consortium they can share information about what the genes do.”
Including a variety of scientists and institutions in the effort also allows Consortium members to “pool financial resources” and increases the project’s legitimacy in the view of large companies that design databases and provide equipment, he said.