First human gene editing performed on human embryo

The resulting embryos would then carry the new mutation-free copies of this gene. USA teams at Oregon Health and Science University and the Salk Institute along with the Institute for Basic Science in South Korea focused on hypertrophic cardiomyopathy (HCM).

"This is not a straightforward question... equally, the debate on how morally acceptable it is not to act when we have the technology to prevent these life-threatening diseases must also come into play".

The experiments on the embryos were conducted in the U.S. following all ethical guidelines.

However, the new research, reported in the journal Nature, goes much further by modifying the nuclear DNA at the heart of the cell that influences personal characteristics such as height, facial appearance, eye colour and intelligence.

This study was a pre-clinical test created to examine the technique's safety and effectiveness, and while further optimization is needed before clinical trials can be considered, the results are promising. Unlike other approaches to treating or preventing disease, CRISPR involves permanent changes to cells that will eventually turn into people and produce their own sperm, eggs, and, possibly, children. Embryos can be genetically screened before they are implanted during in vitro fertilization. It is well known by sports doctors because training worsens the condition in athletes who suffer from this disease.

Not only would that patient be free of the faulty gene, but all of their offspring would be too, effectively stopping this hereditary disease in its tracks. Current treatments rely mainly on symptomatic relief. In this study, the researchers dealt with a mutation characterized by four missing base pairs in the MYBPC3 gene. Not only did the researchers fix the mutation but they are also capable of preventing it from being inherited down the generation line.

But while the procedure is considered to be the first of its kind, human trials are not now allowed in the United States.

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The researchers said they chose hypertrophic cardiomyopathy for their study because they expected its removal to cause fewer off-target changes and mosaics.

"It feels a bit like a "one small step for [hu] mans, one giant leap for [hu] mankind" moment", Jennifer Doudna, a biochemist who helped discover the gene-editing method used, called CRISPR-Cas9, said in an e-mail.

The new procedure tackled a genetic mutation in human embryos that causes hypertrophic cardiomyopathy, an inherited condition in which the heart muscle becomes abnormally thick.

Scientists invented a tool CRISPR-Cas9 works as a type of molecular scissors that can be selectively cut away unwanted portions of the genome and replace them with new DNA.

The process, named as CRISPR, was completed without introducing any harmful mutations, which was a problem in previous attempts. Mosaicism would lead to organisms with some tissues or organs that bear the mutations and some that do not.

Around the time the sperm was injected into the eggs, researchers snipped out the gene that causes the disease.

"We have demonstrated the possibility to correct mutations in a human embryo in a safe way and with a certain degree of efficiency", said Juan Carlos Izpisua Belmonte, a professor in Salk's Gene Expression Laboratory and a co-author of the study. In other words, this technique increased the probability of inheriting the healthy gene from 50% to 72.4%. "Moreover, if such embryos were to grow up, as will doubtless occur in the future, there are likely to be unintended effects from modifying their genes", Fr. Pacholczyk continued. "Editing human embryos with CRISPR should be a long way off", as J. Craig Venter, co-founder of Human Longevity, Inc and a genome expert, put it during Fortune's second annual Brainstorm Health conference in May. According to the scientists, their technique could potentially be applied to "thousands of inherited genetic disorders affecting millions of people worldwide". The National Academies of Sciences, Engineering and Medicine had allowed the research to continue, and had sent recommendations that were followed, the researchers said.

  • Marjorie Miles