The results of a study conducted by Dr Shoukhrat Mitalipov, a reproductive biologist at Oregon Health and Science University, have now been released and are unexpected. The study was conducted to find out if a human embryo would accept a synthetic gene, following removal of a mutated gene already present within the genome of the embryo, using CRISPR technology.

Whilst partial results of the study were leaked last week suggesting that ‘designer babies’ may one day be possible, the paper published in Nature on the 2 August shows that the scientists were in fact unable to insert laboratory-made genes.

Mitalipov said that the “external DNA” that was provided to the embryos was “never used” and that he found this both “very surprising” and “dramatic”. The experiment was performed at the same time the egg was fertilised and the mutated gene, MYBPC3, came from sperm that was provided by a man with hypertrophic cardiomyopathy.

What the researchers found however was that rather than accept the gene supplied by them, the embryo simply copied the mother’s healthy gene and incorporated that into its genome to replace the father’s.

This was done by every single one of the 112 embryos they tested on. “This is the main finding from our study,” Mitalipov said. An embryos’ natural preference for a parent’s gene “is very strong, and they won’t use anything else”, he explained.

Scientists are already looking at ways to work around this

Although the study suggests that disease prevention is harder than previously thought, it does highlight that a “bad” gene from a parent can be eliminated and replaced with a “good” gene from the other parent, efficiently and with apparently very little effect on the rest of the genome.

However, this should be enough to eliminate a disease-causing mutation from an embryo and therefore future generations. Additionally, as Mitalipov explains, “the vast majority of patients” with a disease-causing mutation “have a partner with the healthy gene.”

Dana Carroll of the University of Utah who developed one of the first gene-editing technologies, zinc fingers, said, “I think that was a disappointing finding in the study. Unless there is some way to encourage use of the user-supplied repair template, the ability to introduce specific, desired sequence changes will be limited.”

However, he did say “it’s possible that introducing a double-stranded DNA template, rather than a short single-stranded oligo, would be effective because it more closely resembles the matching, homologous gene.”

Despite, the study’s apparent failure, its critics are not satisfied

The knowledge delivered by this study, that creating ‘designer babies’ will much harder than believed, has done little to quell critics. “We have to weigh the medical benefit to a few” from correcting an embryo’s mutation “against the social risks for all of us,” Marcy Darnovsky, executive director of the Centre for Genetics and Society said.

She believes that with the existence of technology such as screening of IVF embryos through pre-implantation genetic diagnosis, parents with genetic disorders can still have healthy children and therefore there is no need for CRISPR gene editing.

Though she says, “I don’t see any reason to doubt that Mitalipov or others will pursue other new wrinkles in these procedures, to enable more extensive genetic alterations.” Many religious groups were also vehemently opposed to the creation of human embryos for research and the fact that the scientists destroyed the embryos after their research, which they deemed as murder.

While most states in America ban this type of research and federal law prohibits implanting genetically altered embryos into a uterus, Mitalipov says, “unfortunately, this technology will just be shifted to unregulated countries.”

It may be a while before the technology reaches that stage

A poll conducted by STAT and Harvard T.H. Chan School of Public Health suggests that most people are only comfortable with the technology being used to prevent disease and not in creating humans with special genetic prowess.

Additionally, although some studies have identified some genes associated with traits such as enhanced intelligence or athletic ability, they are extremely rare. Therefore to provide such traits to embryos would mean the genes would mostly likely need to be made in a lab and then injected which, in this study, failed.

According to Neville Sanjana, a bioengineer at the New York Genome Center, the outcome of the experiment was to be expected because “this is likely how DNA repair evolved in the first place — to repair a damaged chromosome by using the other, intact one.”

Therefore, “to introduce a novel gene,” Fredrik Lanner, of Karolinska University Hospital in Sweden says, “you would have to target both DNA copies” with CRISPR. MIMS

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