Frog genome mapping sheds new light on environmental contaminants

A UVic molecular biologist has gained new insights into how environmental contaminants may disrupt thyroid systems. The discovery was made while assembling the genome of the North American bullfrog.

Caren Helbing’s findings could help explain the mechanisms of early development, as well as how environmental contaminants cause thyroidrelated diseases and malfunctions.

While bullfrogs might be best known as an invasive species in much of Canada, they are also vital animal models for scientific research.

“Understanding the mechanisms of gene expression in bullfrogs provides valuable insights, with applications in human health, conservation and developmental biology,” says Helbing.

For a tadpole to turn into a frog, a genetic process is set in motion by thyroid hormones. Helbing’s research found that this metamorphosis involves thousands of non-coding genes.

Unlike genes that code for proteins, which are the building blocks of life, noncoding genes are still a puzzle to researchers.

“The takeaway for human health is that non-coding genes may also be at play during early development,” says Helbing. “Understanding the mechanism of non-coding genes will help us understand how the thyroid system is affected during gestation, and how environmental contaminants can disrupt this process.”

Helbing’s lab is the first to map the full genome of any “true frog”—the family of frog species with the largest global distribution. True frogs are sentinel species, signalling by population distress or absence that there is environmental degradation.

“Two-thirds of amphibians are either threatened or declining. Some populations are being wiped out by diseases like chytrid fungus and ranavirus,” says Helbing. “Genomic information can help us determine what’s happening, and how to stop the decimation of these species.”

Helbing’s results were published in Nature Communications in November. The work was funded by Genome BC and the Natural Sciences and Engineering Research Council, with additional support provided by the National Human Genome Research Institute of the US National Institutes of Health.