Gene editing of sperm and eggs clinically irresponsible, scientists say

Scientists have reached a consensus on the boundaries of using a powerful gene editing tool, saying it would be irresponsible to clinically alter our DNA in a way that's passed on to future generations.
Part of the appeal of CRISPR as a research tool is that it's cheap and easy to do, says Tam Mairui. (CBC)

Scientists have reached a consensus on the boundaries for using a powerful gene-editing tool, saying it would be irresponsible to clinically alter our DNA in a way that's passed on to future generations.

On Wednesday, researchers concluded their three-day day meeting in Washington, D.C., on the scientific, ethical and regulatory issues surrounding a gene-editing tool known as CRISPR-Cas 9.

The tool was adapted from one bacteria used to fight off viruses. It allows researchers to manipulate DNA with unprecedented ease and precision to delete, tweak or insert genes. The technological advance opens up new frontiers in genetic medicine, such as preventing hereditary diseases.

One such disease, Duchenne muscular dystrophy, results in a mutation in the muscle protein dystrophin. It leads to muscle degeneration and eventually death.

CRISPR offers an unprecedented opportunity to try to help patients feel better rather than just providing supportive care, said Dr. Ronald Cohn, chief of clinical and metabolic genetics at the Hospital of Sick Children in Toronto.

Cohn gave an example of a child with Duchenne muscular dystrophy. 

Together CRISPR and Cas-9 act as molecular scissors and a guide to cut and paste genetic material. (CBC)

 "This is the son of my very close friends in the U.K., so it's a very personal scientific endeavour for me," Cohn said.

"When you think about the fact that we have now been able, after I've known this boy for eight years, to correct his genetic duplication, provide full length dystrophin in his muscle cells in my petri dish, then I'm now in a position to move the science forward to actually create potentially a medication that can help him one day.

"There cannot be anything more powerful to a scientist or to a physician to begin tackling these problems."

Another inherited disease hits at the other end of the lifespan.

In Niagara-on-the-Lake, Ont., Tam Mairui's family photo album documents how the curse of Huntington's disease devastated her family for generations, including her own mother, Vicki Poirier. Mairui doesn't yet know if she has the gene — or if her children do.

The Huntington gene eventually causes nerve cells in the brain to break down, resulting in mental decline, uncontrolled movements and emotional problems.  If a parent has the disease there's a 50/50 chance a child will develop it,  too.

Vicki Poirier and Tam Mairui look through a family photo album documenting Huntington's toll. (CBC)

Mairui trained as a cancer researcher. After the family discovered her mother carried the Huntington's gene, Mairui turned her attention to trying to find a treatment for Huntington's disease.

At a lab at McMaster University in Hamilton, Ont., Mairui has been impressed with the potential CRISPR holds as a research tool.

 "The thing about CRISPR is that it's cheap and it's easy to do. The buzz is basically if you want to knock out your gene or attach a tag to it, use CRISPR, because it costs in the hundreds of dollars to do, and so far has been proven to be really precise. That is a game-changer for sure."

Here's how CRISPR gene editing works in a nutshell. In the first part of a two-step process, molecular scissors cut DNA. Then RNA, which transmits biological information throughout the genome, acts as a pattern or guide for the scissors to zero in on the precise gene to cut.

"Mother Nature has found very interesting ways of getting things done, and from time to time, we tap into one of those," Mairui said.

But Mairui also sees issues in using the technology to fix genetic diseases, such as how Canada lacks laws against genetic discrimination, which is one reason she's opted against testing. In the case of Huntington's, she believes other potential therapies hold more immediate promise. 

At the conference, members of the U.S. National Academies of Medicine and Sciences, the Chinese Academy of Sciences and the Royal Society of the United Kingdom debated editing the human germline, such as human sperm, and eggs.

Safety issues

Prof. David Baltimore of the California Institute of Technology in Pasadena is chair of the summit's organizing committee. He read out the concluding statement, noting the words moratorium or ban weren't used. 

"We say it  would be irresponsible to proceed with any clinical use of germline editing unless and until the relevant safety and efficacy issues have been resolved … and 2) there is broad societal consensus about the appropriateness of the proposed application," Baltimore said.

Gene editing ushers a brave new world, says cancer researcher Jason Moffat. (CBC)

"The human genome is shared among all nations. The international community should strive to establish norms concerning acceptable uses of human germline editing and to harmonize regulations in order to discourage unacceptable activities while advancing human health and welfare."

Last month, Prof. Jason Moffat of the University of Toronto's Donnelly Centre published a study in the journal Cell on using CRISPR to map out genes that are crucial in diseases like cancer. Moffat welcomed the summit's guidance. 

"I think it's a brave new world and we have to just be cautious when we move forward with editing humans especially," Moffat said. 

Others want the medical research to move forward.

Sarah Gray of the American Association of Tissue Banks addressed delegates on Tuesday about her son, who had a fatal birth defect. The family donated his body for research.

"He was six days old, and he suffered every day. From the look on his face it was like, 'Mom what's going on?'" said Gray. "If you have the skills and the knowledge to fix these diseases, then frickin' do it!"

With files from CBC's Kelly Crowe and Marcy Cuttler