Beaver’s genome mapped out to help celebrate Canada’s 150th birthday

A team of molecular geneticists at Toronto’s Hospital for Sick Children has sequenced the genome of the Canadian beaver - Castor canadensis - to mark the country’s sesquicentennial.

Thestar.com
Jan. 14, 2017
By Sheryl Ubelacker

Scientists have a gift for Canada as the country celebrates its 150th - and as a birthday present, it’s certainly unique.

A team of molecular geneticists at Toronto’s Hospital for Sick Children has sequenced the genome of the Canadian beaver - Castor canadensis - to mark the country’s sesquicentennial.

“The Canadian beaver had not been done, and we figured if anyone’s going to do the Canadian beaver, it should be Canadian scientists, so we exert our dominion over the animal that is out national icon,” said Stephen Scherer, director of the hospital’s Centre for Applied Genomics, who led the six-month pet project to map out the genes that make up the furry rodent.

The genome was sequenced using DNA from Ward, a 10-year-old male beaver that lives at the Toronto Zoo with its mate June - a nod to the Cleaver parents in the 1950s TV show “Leave it to Beaver.”

The researchers believe they are the first in the world to map and publish the Canadian beaver’s genome. Their results were reported Friday in the journal G3: Genes/Genomes/Genetics, which carries on its cover a photo of the first Canadian stamp to feature the enduring national symbol.

The toothy, semi-aquatic animal is intimately entwined with the history of Canada, which was founded on the fur trade - primarily involving the beaver, whose pelts were prized for their thickness and warmth.

“The Canadian settlers at the time, the Hudson’s Bay Company, their decisions of how they migrated across the country and why they stayed in Canada was driven by the fact that the beaver pelt trade was so lucrative,” Scherer said.

To his knowledge, the industrious and determined beaver - the largest indigenous rodent in North America - is the only mammal other than the human with the capability to alter the environment for its own benefit.

“To do that you have to be smart, right?” he said, referring to the beaver’s propensity to gnaw down trees and make dams in streams and rivers so it can construct an underwater lodge for habitation.

“It’s probably a mix of how the genes in the brain work, but also how that experience is taught from parents to offspring. To have the hard-wiring in place to make that leap from a species that cannot do that to one that can is really the overwhelming question in most evolutionary biology.

“What makes this really unique? Is it the number of genes? Probably not,” added Scherer, noting that the beaver has about 20,000 genes, the same as humans, other primates and many other mammals. “It’s probably some specific mutation that altered the hard-wiring that allowed the species to be able to process information . . . to redesign its environment to benefit survival.”

While sequencing the beaver genome was meant to be a birthday present for Canada, it was also done with a more serious goal in mind: the scientists had developed a new technological approach to mapping genetic blueprints and decided to test it on the beaver before applying it to improve sequencing of human genomes for the study of disease.

Si Lok, senior project manager at the centre and a co-author of the beaver genome paper, said the Sick Kids team maps about 10,000 human genomes a year, comparing them to reference examples that already exist.

“But in the case of Ward, this is completely different,” he said. “This is what we call ‘de novo’ sequencing, which literally means ‘from scratch.’

“We actually don’t know what the beaver genome looks like, so we had to assemble it without knowing what the final picture of the jigsaw puzzle is. If we can do this, we can use the same technology and the same approach to identify new mutations in a human genome that we currently are missing.”

Scherer said the new approach will be used to better map genomes of families affected by autism to determine which, if any, mutated genes are behind the neurological condition in their children. In previous studies of other family groups, his lab has found that about 20 per cent of autism cases are caused by genetic mutations.

“There’s a lot of genetic variants that are missed (with the standard technology) because we’re comparing to what we already know about the human genome,” he said.

“We could have done this first on a human genome, but we thought we would check two boxes and as good Canadians sequence something new and give it as a gift for the Canadian sesquicentennial.”