Scientists have cured human embryos of a blood disorder in a first-ever technique that could one day stamp out inherited diseases.

Researchers with Sun Yat-sen University in China performed “chemical surgery” on the lab-made embryos to remove the disease called beta thalassemia, which reduces the production of hemoglobin, according to the BBC.

“We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system,” said researcher Junjiu Huang.

Huang said the study creates the possibility of treating patients and preventing babies being born with beta thalassemia — “and even other inherited diseases.”

The experiment was conducted on tissue taken from a patient with the blood disorder and human embryos made through cloning.

Researchers used a technique called “base editing,” which alters the fundamental building blocks of DNA — adenine, cytosine, guanine and thymine, commonly known by their respective first letters, A, C, G and T.

Beta thalassemia is caused by a fault called a point mutation — a change to a single base in the genetic code.

Researchers used base editing to change a G base to an A — successfully curing the DNA of the blood disorder.

Base editing is an advanced form of gene editing called Crispr, which breaks DNA.

David Liu, who pioneered the technique at Harvard University, said the method is preferred because it creates fewer side effects than Crispr.

“About two-thirds of known human genetic variants associated with disease are point mutations,” said Liu. “So base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations].” </s> Image copyright Getty Images

Precise "chemical surgery" has been performed on human embryos to remove disease in a world first, Chinese researchers have told the BBC.

The team at Sun Yat-sen University used a technique called base editing to correct a single typo out of the three billion "letters" of our genetic code.

They altered lab-made embryos to remove the disease beta-thalassemia. The embryos were not implanted.

The team says the approach may one day treat a range of inherited diseases.

Base editing alters the fundamental building blocks of DNA: the four bases adenine, cytosine, guanine and thymine.

They are commonly known by their respective letters, A, C, G and T.

All the instructions for building and running the human body are encoded in combinations of those four bases.

Image copyright Getty Images

The potentially life-threatening blood disorder beta-thalassemia is caused by a change to a single base in the genetic code - known as a point mutation.

The team in China edited it back.

They scanned DNA for the error then converted a G to an A, correcting the fault.

Junjiu Huang, one of the researchers, told the BBC News website: "We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system."

He said their study opens new avenues for treating patients and preventing babies being born with beta-thalassemia, "and even other inherited diseases".

The experiments were performed in tissues taken from a patient with the blood disorder and in human embryos made through cloning.

Genetics revolution

Base editing is an advance on a form of gene-editing known as Crispr, that is already revolutionising science.

Crispr breaks DNA. When the body tries to repair the break, it deactivates a set of instructions called a gene. It is also an opportunity to insert new genetic information.

Base editing works on the DNA bases themselves to convert one into another.

Prof David Liu, who pioneered base editing at Harvard University, describes the approach as "chemical surgery".

He says the technique is more efficient and has fewer unwanted side-effects than Crispr.

He told the BBC: "About two-thirds of known human genetic variants associated with disease are point mutations.

"So base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations]."

Image copyright Getty Images

The research group at Sun Yat-sen University in Guangzhou hit the headlines before when they were the first to use Crispr on human embryos.

Prof Robin Lovell-Badge, from the Francis Crick Institute in London, described parts of their latest study as "ingenious".

But he also questioned why they did not do more animal research before jumping to human embryos and said the rules on embryo research in other countries would have been "more exacting".

The study, published in Protein and Cell, is the latest example of the rapidly growing ability of scientists to manipulate human DNA.

It is provoking deep ethical and societal debate about what is and is not acceptable in efforts to prevent disease.

Prof Lovell-Badge said these approaches are unlikely to be used clinically anytime soon.

"There would need to be far more debate, covering the ethics, and how these approaches should be regulated.

"And in many countries, including China, there needs to be more robust mechanisms established for regulation, oversight, and long-term follow-up."

Follow James on Twitter. </s> In the wake of the first gene-edited embryos in the US being created earlier this year, Chinese researchers have employed a different technique to swap a single base in a human embryo's genome.

The precise edit was designed to return functionality to a gene responsible for a component of haemoglobin, which in its mutated form results in an often fatal blood condition called beta-thalassaemia.

A team of researchers from Sun Yat-sen University in Guangzhou, China, used what's called a base editor technique to change a single G back to an A in the DNA code of an embryonic cell's HBB gene.

The change might have been tiny, but in its mutated form HBB can't produce the protein beta-globin needed to build the oxygen-carrying haemoglobin for our red blood cells.

A shortage of haemoglobin means a shortage of oxygen, impeding growth and development and leading to a lifetime of blood transfusions to treat anaemia – if the embryo survives at all.

Beta-thalassaemia is usually a recessive condition, meaning both parents need to contribute a copy of the mutated gene for anaemia to develop in their child.

Correcting the mutations in this gene could help parents carry an embryo to term, or remove the trait from family lines.

About 400 different kinds of code-corruptions can affect HBB.

In this case, the researchers focussed on a single point-mutation that targets a base called cytosine (C) and exchanges it for one called thymine (T).

Each of these letters complements the other two kinds of base – thymine is a jigsaw-puzzle piece that matches adenine (A), while cytosine matches guanine (G).

By swapping a C for a T, the mutation should revert back to the proper 'A' code.

If this base editing technology seems unnecessarily complicated, there's a good reason for doing a genetic do-si-do – it means the strand of DNA isn't being snipped all the way through.

To test if the procedure was feasible, the team created a cell line with pieces of the gene embedded inside and then used two different base editing techniques to change the code.

Satisfied the editing could be done, they took the process to the next level and edited the gene in skin cells from a beta-thalassemia patient.

Researchers transferred the nucleus of the patient's skin cells into 30 mature oocytes – or human egg cells.

One of the techniques was then applied to the 26 cells that survived the cloning procedure, which successfully turned the G to an A in 9 of the embryos, and a G to a C (cytosine) in one.

None of the embryos were developed further or implanted.

Gene editing has been big news in recent years with advances in the application of a technology called CRISPR, which uses enzymes found in bacteria to chew up DNA at a specific location.

Applying this kind of corrective genetic surgery to human embryos could spell an end to a variety of inherited conditions, but so far efforts have been controversial, to say the least.

Questions have developed recently on whether or not the technology produces unwanted mutations, indicating that for all of its promise, it's still early days for this revolutionary engineering tool.

Base editing won't replace CRISPR, but could be a more delicate solution for those solitary mutations.

"We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system," researcher Junjiu Huang told the BBC.

Feasibility is the word here. We're nowhere near a safe operating procedure for repairing genes we consider broken in embryos.

But each careful step, coupled with healthy public debate, brings us a bit closer to an age when debilitating conditions like beta-thalassemia will be notes in a medical history book.

This research was published in Protein & Cell. </s> Chinese scientists used an adapted version of a controversial gene-editing technique to correct a disease-causing mutation in human embryos, a medical first cautiously hailed by other experts Thursday.

The team used a so-called "base editor" -- an adaptation of the CRISPR-Cas9 DNA snipping tool -- to correct a single, mutated "letter" among about three billion in the intricate coding of the human genome.

The targeted mutation can cause humans to be born with beta-Thalassaemia, a potentially fatal genetic blood disorder.

"This study demonstrated the feasibility of curing genetic diseases in human... embryos by base editor system," the team wrote in the specialist journal Protein & Cell.

The journal sparked controversy when it published a paper in 2015 in which the same authors reported on experiments with CRISPR-Cas9 to modify the thalassaemia gene.

That paper led to calls for a halt to experiments involving the genetic editing of human embryos.

Many fear such technology could lead to so-called "designer babies" with desired features such as intelligence engineered into their genes.

For the new study, Puping Liang of the Sun Yat-sen University in China, and a team used a technique based on CRISPR-Cas9, which allows scientists to remove and replace a faulty strand of DNA with pinpoint precision.

Instead of using the Cas9 protein as "scissors" to eliminate the mutated "letter", they used an enzyme to change it.

- Can it be improved? -

DNA is the instruction booklet for cells to make and sustain life.

It resembles a zipper-like spiral -- the teeth on each strand are "base pairs" of encoding "letters" that chemically match with each other.

Adenine teams up with thymine to create the A-T base pair, while cytosine pairs with guanine for the C-G pair.

Thalassaemia can be caused by an "A" base letter converted to a "G" in a specific location of the gene.

For the latest study, the team sought to chemically change the "C" partner of the mutant "G", to a "T".

This would cause the errant "G" to automatically convert to an "A", expert Robin Lovell-Badge of the Francis Crick Institute, who was not involved in the study, explained via the Science Media Centre.

The method eliminated the need to cut DNA, and the team were successful about one in five times.

They worked with cloned embryos that were kept alive for just a few days for the purposes of lab experimentation

Observers said the technique appeared to be an improvement on standard CRISPR-Cas9.

"This powerful study sheds new light on precise gene correction for single gene disorders," commented Helen Claire O'Neill of University College London.

"It remains to be seen whether the efficiency... can be improved upon."

For Darren Griffin, a genetics professor at the University of Kent, the paper showed that "the ethical implications of gene manipulation in embryos need a thorough examination where safety is of paramount concern."

US-based scientists in August reported using CRISPR-Cas9 to repair a disease-causing mutation in the DNA of early-stage human embryos.

Last week, British scientists said they had used CRISPR-Cas9 to reveal the role of a key gene in the early development of human embryos. </s> Chinese scientists have successfully altered the genetic code of a human embryo, an “ingenious” breakthrough that experts believe could be key to eradicating hereditary diseases.

Using a technique known as ‘base editing’, researchers from Sun Yat-sen University in Guangzhou filtered through three-billion ‘letters’ of our genetic code to remove a single error responsible for a potentially deadly blood disorder.

"We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system,”Junjiu Huang, one of the scientists involved in the research, told BBC.

During the experiments, which were carried out on tissues taken from a patient with the blood disorder beta-thalassemia and inserted into cloned human embryos, a strand of DNA was examined to pinpoint the offending base. The team then used base editing, a more advanced form of the Crispr gene-editing technique to repair the faulty gene.

Such is the level of precision involved in base editing that Professor David Liu of Harvard University, a pioneer of the technique, dubbed it “chemical surgery.”

“Base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations]," Liu said, adding that it is more efficient than Crispr as it has fewer unexpected side-effects.

The study, which has been published in the journal Protein and Cell, presents serious ethical questions for scientists.

While describing parts of the study as “ingenious,” Professor Robin Lovell-Badge of the Crick Institute in London called for robust regulation the techniques employed in gene editing.

"There would need to be far more debate, covering the ethics, and how these approaches should be regulated,” Lovell-Badge said. "And in many countries, including China, there needs to be more robust mechanisms established for regulation, oversight, and long-term follow-up."

The debate is also raging in the US, where the National Academy of Science and the National Academy of Medicine recommended easing the blanket ban on modifying DNA in February this year.

“We’ve always said in the past gene editing shouldn’t be done, mostly because it couldn’t be done safely. That’s still true, but now it looks like it’s going to be done safely soon,” Richard Hynes, a cancer researcher at the Massachusetts Institute of Technology who co-led the committee, told the New York Times. </s> (CNN) Scientists are getting one step closer to snipping inherited genetic diseases out of human offspring using a gene-editing technique called CRISPR.

For the first time, scientists said, they corrected a gene mutation linked to inherited heart conditions in human embryos using the approach. A study demonstrating the technique was published in the journal Nature on Wednesday (PDF).

Last week, the MIT Technology Review released the first news of this scientific feat, describing the research as the first-known attempt at creating genetically modified human embryos in the United States.

However, Juan Carlos Izpisua Belmonte, a co-author of the study, described it as the first in the world to demonstrate gene-editing to be safe, accurate and efficient in correcting a pathogenic gene mutation in human embryos. Previous attempts by Chinese researchers were unsuccessful at achieving this without safety concerns.

"This is the first that has been demonstrated as safe and working," said Belmonte, a professor at the Salk Institute for Biological Studies' gene expression laboratory in La Jolla, California.

"All cells of the embryo were corrected," he said. "It seems to be working from these samples that we have chosen, but we need to do much more basic research with many other genes."

The study was a collaboration between the Salk Institute, the Oregon Health & Science University in Portland and Korea's Institute for Basic Science.

Scientists estimate that more than 10,000 human diseases may result from mutations to a single gene occurring in all cells of the body, according to the World Health Organization

Cutting and correcting gene mutations

The study used 75 human zygotes in which the father carried a mutation on the MYBPC3 gene, Belmonte said. The eggs used to produce the zygotes did not carry that gene mutation. The researchers noted that they received informed consent from the donors of the eggs, sperm and embryos used in the study.

Hypertrophic cardiomyopathy also is thought to be the most common inherited or genetic heart disease in the US, according to the Centers for Disease Control and Prevention

Newly fertilized eggs before gene editing, left, and embryos after gene editing and a few rounds of cell division.

In a lab dish, the researchers used CRISPR, a gene-editing technique, to remove the harmful MYBPC3 mutation from the human zygotes. Then, the zygotes' own DNA-repair mechanism replaced what was cut out with a copy of a MYBPC3 gene from the mother, which did not carry a mutation, Belmonte said.

"A male research subject known to be heterozygous for this gene mutation was recruited for the study, as were several healthy young egg donors," Dr. Paula Amato, an obstetrician-gynecologist at Oregon Health & Science University, said Tuesday. She was a co-author of the study.

"CRISPR was introduced at the time of sperm injection," she said. "Then, DNA repair of the embryos was assessed."

The researchers found that about 72% of zygotes were properly and safely corrected on the MYBPC3 gene, Belmonte said.

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This method significantly differed from studies in which scientists used the CRISPR tool to replace what was cut out with whatever the scientists desired.

"The previous human studies done in China had very small numbers, and one of them used abnormal embryos," Amato said. "So we think this is the first, largest study from which you could draw some reasonable conclusions."

Some gene-editing attempts in human embryos have been problematic, resulting in an issue called mosaicism , in which the corrections made in one gene failed to replicate once that cell divided into two cells, those two cells divided into four cells and so on.

"So when the baby is born, all the cells do not have the mutation anymore. ... This study, it shows that we can correct the embryo and then, after the division, all the cells are corrected, so there's not what we call mosaicism," said Belmonte, who is also a member of the National Academies of Sciences, Engineering and Medicine's committee on human gene editing.

This year, the academies published a report on human genome editing that addressed potential applications of the technology, including the possible prevention or treatment of inherited diseases or conditions.

The future of gene editing

Though the researchers have expressed enthusiasm around their new study, they also noted that the findings must be replicated in followup research before this gene-editing approach can move forward to clinical trials.

"The fact that it is, apparently, a new and poorly understood mechanism and it is not the now standard CRISPR 'cut and replace' method adds to the time needed for research into its safety and effectiveness," said Hank Greely, professor of law and genetics at Stanford University, who was not involved in the new study.

Yet future research can come with some political challenges, Amato said.

"First of all, there are regulations regarding use of federal funds for embryo research, so the (US National Institutes of Health) does not currently support embryo research, so that's one barrier. The other barrier is, the (US Food and Drug Administration) is prohibited from considering any clinical trials related to germline genetic modification," she said.

In this new study the embryos were only allowed to mature to day three after fertilization before they were disaggregated, or isolated into various components, for further analysis.

In the far-off future, a clinical trial could include transplanting corrected embryos into a uterus with the goal of establishing pregnancy and then monitoring the embryos as they develop into children.

Still, "it is way too early to contemplate implanting the edited embryos for the purpose of actually establishing a pregnancy," said Dana Carroll, a professor of biochemistry at the University of Utah who was not involved in the new study but has used CRISPR in his own research.

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"The genome editing tools are currently not sufficiently efficient and specific to be reliable, and regulatory and oversight processes have not been established," Carroll said, adding that the work on the new study was "well-done" and "well-presented."

"The authors have made an important discovery regarding the repair of CRISPR-induced DNA breaks in human eggs just at the time of fertilization," he said.

"This information will help to guide ongoing research, and it demonstrates that research on early-stage human embryos will be necessary to establish safe and effective procedures in the long run," he said. "There is still a lot of work to do to understand repair processes in very early embryos and to optimize the use of the CRISPR reagents, but this study makes a valuable contribution."

Some CRISPR critics have argued that gene editing may give way to eugenics and to allowing embryos to be edited with certain features in order to develop so-called designer babies

However, the researchers wrote in their study that they hope CRISPR could be considered as an alternative option to preimplantation genetic diagnosis, also known as PGD, for couples at risk of passing on an inherited disease.

'This opens up the possibility for those embryos'

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When only one parent carries a heterozygous mutation on a gene, about half of the embryos from that parent should be mutation-free while the others would have the mutation. Selectively, the parents' doctor would chose the healthy embryos to be implanted and discard the embryos with the mutations, Belmonte said.

Sometimes, "a couple that wants to have a baby and they have a mutation, they may not have enough embryos to choose from," he said. This is when CRISPR can come in.

"This technology, independent of the embryos that are there, it would go on and correct all of them. ... This opens up the possibility for those embryos," he said. "That's important because after the first implantation, if it doesn't work, you can do it again."

The researchers wrote in their study, "PGD may be a viable option for heterozygous couples at risk of producing affected offspring. In cases when only one parent carries a heterozygous mutation, 50% of embryos should be mutant. In contrast, targeted gene correction can potentially rescue a substantial portion of mutant human embryos, thus increasing the number of embryos available for transfer."

Nonetheless, using CRISPR in that way remains a long way off.

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Shoukhrat Mitalipov, director of the Oregon Health & Science University's Center for Embryonic Cell and Gene Therapy, helped lead the new study. In 2013, Mitalipov and his colleagues reported the first success in cloning human stem cells , reprogramming human skin cells back to their embryonic state. In 2007, a research team led by Mitalipov announced that they created the first cloned monkey embryo and extracted stem cells from it.

Now, when it comes to using CRISPR to correct gene mutations in embryos, Mitalipov said Tuesday, "We've done some ground work. ... There is still a long road ahead, and it's unclear at this point when we will be allowed to move on." </s> He Jiankui, a Chinese researcher, is claiming to have successfully used the genetic editing tool CRISPR-Cas9 to alter the DNA of two twin baby girls. A researcher at the Southern University of Science and Technology of China in Shenzhen, He claims that he has given the girls an ability to resist possible future HIV infection.

Declining to name the parents of the children or offer any independent verification of the work, there is still skepticism that He, who has degrees from Stanford and Rice, has actually done it. Cases of scientific fraud in high-stakes breakthroughs, like South Korean researcher Woo Suk Hwang's cloning claims, still loom large. But if He has genetically altered the two children, it is a monumental step forward for CRISPR technology.

“I feel a strong responsibility that it’s not just to make a first, but also make it an example,” He told the Associated Press. As for laws governing genetic engineering, He says, “society will decide what to do next.”

CRISPR's potential to treat serious diseases has been known for years, although scientists are unsure how many people are actually immune to the procedure.

He claims that he chose the HIV virus, the infection that can lead to AIDS, because the disease is a growing problem in China. In September, the Chinese government announced a 14 percent rise in the number of citizens living with HIV or AIDS, with 40,000 new cases reported in the second quarter of 2018. He has also put out a series of YouTube videos describing his reasoning for choosing to focus on HIV as well as the ethics of his actions.

He claims to have edited the embryos of seven couples during in vitro fertilization (IVF), in which an egg and sperm are combined outside the body. In all seven cases, the men had HIV and the women did not. The couples were recruited through an AIDS advocacy group called Baihualin, which works against societal discrimination of those infected with the disease.

He focused on disabling a gene well-known to HIV researchers: CCR5, a protein on the surface of white blood cells. HIV commonly uses the CCR5 protein to enter cells. By disabling the CCR5 doorway, He's work would block off one of the HIV virus's most common routes of infection.

Genetic alternations made during the IVF stage can be inherited by future children, the prospect of which has made such testing illegal in the United States. While China has laws outlawing cloning, no such regulations prevent gene editing.

Laws aside, the announcement has been met with severe backlash across the scientific community. Focus has been not just on general morality but also on He's choice of target. While CCR5 is a gateway for HIV, it also works to prevent mosquito-associated diseases like West Nile virus.

In a strenuous statement, one of the inventors of CRISPR technology, Feng Zhang of MIT and Harvard, said that, "Although I appreciate the global threat posed by HIV, at this stage, the risks of editing embryos to knock out CCR5 seem to outweigh the potential benefits, not to mention that knocking out of CCR5 will likely render a person much more susceptible for West Nile Virus. Just as important, there are already common and highly-effective methods to prevent transmission of HIV from a parent to an unborn child."

"Given the current state of the technology, Feng continues, "I'm in favor of a moratorium on implantation of edited embryos, which seems to be the intention of the CCR5 trial, until we have come up with a thoughtful set of safety requirements first." </s> (CNN) In the future, it might be possible to prevent inherited illnesses by making a change to a single faulty gene. That was recently demonstrated in a new study.

For the first time, scientists used a controversial gene-editing technique called base editing to correct a gene mutation in human embryos linked to the hereditary blood disorder beta thalassemia , according to the study published in the journal Protein & Cell in September.

A change to a single base pair in your genetic code, known as a point mutation , can cause beta thalassemia

The scientists noted that the efficiency of repairing mutations in the study was only about 20% -- so they were not 100% successful in effectively editing all of the embryos all of the time. Yet the study findings and the base editing technique are now gaining international attention.

The base editor technique is similar to the powerful gene-editing tool called CRISPR, but there is a major difference.

Base editing uses some of the components of CRISPR, but directly makes changes to a targeted site in DNA without cutting the DNA, said David Liu, core institute member of the Broad Institute and professor of chemistry and chemical biology at Harvard University, who was not involved in the study.

When a cut is made in genomic DNA using the traditional CRISPR approach -- for instance, to disrupt a mutation -- the primary response of a cell is to repair the cut and, in the process, disrupt the DNA at the cut site, Liu said.

"But many human genetic diseases are caused by single point mutations that need to be precisely corrected, rather than disrupted, in order to treat or study the corresponding disease," Liu said. That's where base editing comes in.

"Base editing, in contrast, does not make a double-stranded cut in the target DNA. Instead, base editors directly perform 'chemical surgery' on the target DNA base to convert one base pair to a different base pair, that is, to make a point mutation," said Liu, whose research group at Harvard developed base editing.

"It's important to note that compared to traditional nuclease-mediated genome editing methods such as the use of CRISPR-Cas9, base editing is a complementary -- not necessarily better -- approach, and each approach has its strengths and preferred applications," he said.

About two-thirds of known human genetic variants associated with diseases are point mutations, so base editing has the potential to correct or reproduce such mutations for research purposes, Liu said.

'The future is here'

"The paper itself represents a significant technical advance because, rather than using the classic CRISPR-Cas9 technology previously reported, the current 'base editor' technology is an adaptation that chemically alters the DNA bases themselves," Griffin said about the new study, of which he was not involved.

"While this is undoubtedly a highly significant advance, it is important not to get carried away about its widespread utility if put into clinical practice," Griffin said.

"An embryo would still need to be diagnosed as abnormal (if there were other embryos in the cohort that were normal they would presumably be used instead), then the base editor applied, then re-diagnosed to make sure that it had worked," he said. "In the meantime, the ethical implications of gene manipulation in embryos need a thorough examination where safety is of paramount concern."

The new study involved base editing experiments in cells from beta-thalassemia patients and human embryos. Cloned human embryos were generated in a lab using a technique called nuclear transfer. A total of about 20 embryos were harvested.

"It's interesting work that shows that base editing can directly correct a pathogenic beta-thalassemia mutation in the promoter of the beta-thalassemia gene in cells from beta-thalassemia patients, and in cloned human embryos," Liu said.

Without treatment, patients with the more severe type, known as beta thalassemia major, usually die before age 5, the scientists wrote in the study.

"Our data highlight the tremendous potential of correcting homozygous disease and compound heterozygous mutations by base editing in human somatic cells and embryos," the scientists wrote. "Although we did not achieve 100% repair in human embryos, we and other groups have reported 100% base editing in mouse embryos."

The scientists noted that the base editing wasn't uniform across all cells in the embryos, resulting in mosaic embryos. They also noted in the study that more research is needed to improve the safety of this base editing approach, especially before base editing is ready to use in humans.

"The efficiency of editing was quite low, and the embryo was mosaic as it developed, meaning that only some cells had the hoped-for base change. Both of these inefficiencies have to be overcome for the approach to be useful," said Dana Carroll, a professor of biochemistry at the University of Utah, who was not involved in the study but has used CRISPR in his own research.

"As far as I know, this is the first published study that uses base editing in human embryos, but the embryos are very unusual," he said, referring to how they were made in a lab. "It seems unlikely that the response to the base editor, and other cellular events, are an accurate reflection of what would happen in a natural embryo."

A request for comment from some of the scientists was unsuccessful.

All in all, the scientists noted in the new study that technical, ethic, and societal issues still need to be investigated and discussed thoroughly before base editing could be considered for clinical application.

Meanwhile, Liu said that his own research group has generated additional base editors that could expand the capabilities of the gene-editing technique.

"We will be reporting these developments in due course," he said. "We are hopeful that base editing might advance the study and treatment of genetic diseases, and our laboratory is working hard towards this goal." </s> In the landmark trials, the US and South Korean team demonstrated how they can use CRISPR technology (a revolutionary tool used to edit DNA) to successfully free the embryo from a faulty piece of DNA introduced by one of the parents at conception.

This opens the door to potentially tackle thousands of inherited diseases, but this study focused specifically on hypertrophic cardiomyopathy, a condition that causes the heart’s muscular wall to thicken and affects one in every 500 people worldwide.

Caused by an error in a single gene, anyone carrying it has a 50% chance of passing it on to their future children, but editing the DNA removes this risk.

Dr Shoukhrat Mitalipov, who worked on the study, wrote in the ‘Nature’ journal: “Every generation on would carry this repair because we’ve removed the disease-causing gene variant from that family’s lineage.

“By using this technique, it’s possible to reduce the burden of this heritable disease on the family and eventually the human population.”

Taking sperm from a male donor who has hypertrophic cardiomyopathy, and an egg from a healthy woman, the team injected the CRISPR technology at the point of fertilisation to carry out the genetic repairs.

Although it was not 100% successful, the attempt worked in 72% of the 58 embryos - the biggest success rate anywhere in the world so far.

The embryos were then allowed to develop for five days, before the experiment was stopped; as no work of this kind with modified embryos is actually permitted to carry children to term, it is only for purposes of “better understanding” human development.

This includes in the UK where, according to the UK Human Fertilisation and Embryology Authority (HFEA) 2016 licensing, embryos must be destroyed within 14 days and cannot be implanted into a woman after being altered.

A spokesperson for HFEA said: “UK researchers can apply for a license to edit human embryos in research, but offering it as a treatment is currently illegal.”

This is the first time such a trial has taken place outside of China, where laws are more relaxed.

But all previous Chinese trials (the most recent was in 2015) have not been this successful, and have resulted in “mosaic” cells that are a tapestry of healthy and unhealthy cells, as well as parts of the genetic code being mutated.

More work is needed to prove that gene editing would be safe to do in people, but even if it seems safe, scientists face major regulatory hurdles before clinical trials could start.

Today, people who carry certain genetic diseases can opt for IVF and have their embryos screened for harmful mutations but there are many ethical questions about the potential for creating “designer” babies that could be “edited” to have a specific intelligence, height, facial appearance or hair colour.
The journal Protein & Cell publishes Sun Yat-sen University research describing the use of gene therapy in the removal of a version of the inherited blood disorder beta-thalassemia from an artificially-created nuclear transfer-type of cloning-model system of human oocytes. Collectively, this study demonstrated the feasibility of curing this and a range of other inherited diseases using the same genome editing technology of CRISPR.