Chinese scientists say they’ve genetically modified human embryos for the very first time. The team attempted to modify the gene responsible for β-thalassaemia, a potentially fatal blood disorder, using a gene-editing technique known as CRISPR/Cas9. Gene editing is a recently developed type of genetic engineering in which DNA is inserted, replaced, or removed.
The team injected 86 embryos and 71 survived, of which 54 were genetically tested. This revealed that just 28 were successfully spliced, and that only a fraction of those contained the replacement genetic material. Analysis also revealed a number of ‘off-target’ mutations assumed to be caused by the technique acting in other areas of the genome. The results reveal serious obstacles to using the method in medical applications.
The scientists have tried to head off ethical concerns by using 'non-viable' embryos, which cannot result in a live birth, that were obtained from local fertility clinics. However, the work is very controversial, with some warning it could be the start of a slippery slope towards designer babies.
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EXPERT COMMENTS
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Prof Robin Lovell Badge, Crick Institute, on the science:
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“The experiments reported by Junjiu Huang and colleagues (Liang et al) in the journal Protein Cell on gene editing in abnormally fertilised human embryos are, I expect, the first of several that we will see this year. There has been much excitement among scientists about the power of these new gene editing methods, and particularly about the CRISPR/Cas9 system, which is relatively simple to use and generally very efficient. The possibility of using such methods to genetically modify human embryos, and therefore humans, has been on the cards since these methods were first described, and recently these prospects have been brought to the attention of the public through several commentaries made by senior scientists and commentators, some of whom have called for a moratorium to halt any attempts.
I disagree with a moratorium, which is in any case unlikely to work well, indeed I am fully supportive of research being carried out on early human embryos in vitro [in culture/in the lab], especially on embryos that are not required for reproduction and would otherwise be discarded. If the techniques work, there are many interesting questions that could be asked about the role of specific genes in early human embryo development, especially as there is accumulating evidence that equivalent stages of embryos from other mammals, notably the mouse from which most of our understanding has come, may rely on the activity of different genes.
The paper from this Chinese group is the first to ask if the methods work, and the answer provided is very equivocal. Yes, they do, but inefficiently and with several problems. The most critical of the latter are "off target" effects, where genes distinct from that being targeted (which in this case is the gene encoding betaglobin, a red blood cell protein), have ended up being mutated. This has occurred at a much higher frequency than has been found in other cases where the techniques have been applied to human cells in culture or to mouse embryos. Moreover, even within the betaglobin gene, there was a high frequency of incorrect editing (as if an autocorrect spell check function had been turned off), resulting in yet more errors in the DNA sequence. This leads the authors to suggest that a lot more work will be required to alter the techniques for use in human embryos. However, there are a few issues with the design of the experiments. First, specific DNA repair mechanisms are required for precise (homology driven) gene editing, whereas others lead to the sorts of errors reported in the paper. The authors used abnormally fertilised embryos, presumably because they did not want to be accused of using embryos that could undergo development to term if implanted. However, it is possible that the DNA repair mechanisms that are more likely to lead to errors have been activated in such abnormal embryos, as these struggle to cope with an abnormal genetic complement (they are triploid rather than diploid), and are destined to block early in development. Secondly, it would have made sense to test out the techniques and reagents (notably the "guide RNA") using human embryonic stem cells, which would be more similar to human embryos than the somatic cell line they used. They also chose a gene target that might itself be problematic, given that it is part of a closely linked family of globin genes with highly related sequences, making it hard to target one without affecting the others.
The Nature commentary on this research suggests that previous attempts by the authors to publish their work had failed at least in part due to ethical issues. I do not know what these are. However, it is clear that if the work had been done in the UK, with the excellent regulatory system we have provided by the HFEA, any ethical concerns would have had to have been solved before the work could have been started, as it would require a licence from the HFEA. Indeed, with a licence, research of this sort could be conducted in the UK, and, with justification, it would be possible to use normally fertilised embryos. Of course, it would be illegal to implant any such manipulated embryo into a woman for further development. Indeed, a lot of the fuss about the possibility of germline gene editing is misplaced, because there are very few instances where it would be necessary to correct a gene defect (which was the ultimate aim of the work reported here), because alternative techniques, notably pre-implantation genetic diagnosis (PGD), can be used to choose embryos for implantation that would not develop diseases such as beta-thalassaemia.”
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Prof Robin Lovell Badge, Crick Institute, said on the legal issues:
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“It is legal to do this for research purposes on early human embryos in the UK with a licence from the HFEA, but the 14 day limit applies and it would be illegal to implant the embryos into a woman for further development.
In the USA, it is not possible to do such research with Federal funding (e.g. NIH), and although some States have rules that would forbid it irrespective of funding source, it would be legal with non-federal funds (charities, foundations, companies, private, etc). Indeed, in addition to research in vitro, it would in theory be possible in some States to implant the embryos in an attempt to obtain children. There is no equivalent to the HFE Act or HFE Authority in the USA and therefore no federal rules governing assisted conception (IVF, etc). Clinics are supposed to follow guidelines issued by professional organisations, such as the ASRM (American Society for Reproductive Medicine), but many do not, or they are selective about which part of the guidelines to follow. There may be local ethical review committees that clinics need to consult, but these are variable in quality and in the decisions they make.
As far as I understand it, China has guidelines issued by the central government, rather than laws governing both research and clinical applications using human embryos. These guidelines tend to be followed because it is not a good idea to fall on the wrong side of Government. But perhaps if a lab is a long way from Beijing, who knows ...
It would be impossible to do these types of experiment in some European countries, notably Germany and Italy, but other countries have rather liberal laws, such as Spain and Sweden, and they may well permit research in vitro. In Germany and I believe Italy, it is only possible to carry out a procedure on an early human embryo that would not cause it harm. (I think that spare embryos left over from IVF have to be stored frozen, perhaps forever as they can't be killed.) For example, PGD is illegal in Germany because embryos that are found to have a genetic defect have to be discarded and therefore "harmed". It might be interesting to ask if the gene editing would be of benefit to the embryo, would it be legal to transfer it into a woman to obtain a child? I suspect the answer would come back "no" as this might constitute an affront to "human dignity" - but it has never been clear (at least to me) how "human dignity" can apply to a pre-implantation embryo, and if the gene editing had corrected a gene defect, in what way would it be harmed ?
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Dr Dusko Ilic,, Reader in Stem Cell Science , King's College London Faculty of Life Sciences and Medicine
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“Recent call for moratorium on genome editing research on human embryos, gametes and germ cells is just a call, not a law that can be imposed to any country. If the technology exists, scientists will continue doing such experiments and eventually one day repair of mutation causing genetic diseases can become a reality. Today, with a standard preimplantation genetic diagnosis (PGD) technology, we can pretty accurately determine for several hundred monogenetic inheritable diseases, which embryos carry the mutation and which do not, allowing us to select healthy ones and discard those with mutations. If and when one day genome editing in embryos becomes a successful and safe technology the couples who were so unlucky as to not have even a single healthy embryos will have an opportunity to have a healthy child.
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Dr Anna Smajdor , a medical ethics expert from the University of East Anglia’s Norwich Medical School, said:
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“There is a whiff of hypocrisy about the moral outrage over reports that Chinese scientists have been modifying the DNA of embryos. Here in the UK we have given the go ahead to modifying the DNA of babies who will transmit these changes indefinitely to their offspring. The Chinese have tweaked DNA in embryos never destined to be born.”
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Sarah Norcross, Director of the Progress Educational Trust, said:
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"The UK has pioneered embryo research and while UK-based scientists need to keep a close watch on developments in China and elsewhere, public discussion of the ethics and implications for society of editing genes in human embryos needs to be stepped up so that policymakers can make informed decisions about whether the law should be changed in the UK to permit this type of research."
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Dr Ewan Birney, Associate Director, European Bioinformatics Institute, said:
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“I am concerned by this paper. Using the gene editing technology (CRISPR/Cas9) in human embryos is unacceptable in the UK ethical framework, and I notice that in the Nature report, this paper was suggested to be rejected by journals potentially on ethical grounds. There is a striking contrast to the careful discussion and ultimate consensus approach on mitochondrial donation in the UK context.
“At a broader level, it is important to stress that scientists work under ethical rules, and the ethical rules are fundamentally societal, not scientific (though scientific advances often pose the question). This consensus position does change (for example, human transplants in the 1950s were viewed far less positively than now) but it is important this conversation happens in a consensus, societal way. In many ways, the UK framework is very responsible here.”
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Dr Yalda Jamshidi, Senior Lecturer in Human Genetics, St George’s University Hospital Foundation Trust, said:
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“Inherited genetic conditions often result because the function of a gene is disrupted. In theory replacing the defective gene with a healthy one would be the ideal solution. This type of treatment is what we call gene therapy and researchers have been working on developing techniques to accomplish this for many years.
Techniques to correct defective genes in 'non-reproductive' cells are already at various stages of clinical development and promise to be a powerful approach for many human diseases which don't yet have an effective treatment. However, altering genes in human embryos can have unpredictable effects on future generations. Furthermore the study by Huang et al showed that the although the CRISPR/Cas9 technique they used can work in the embryo, it can miss the target in the gene and is too inefficient.
Future research on the technique may improve the accuracy and efficiency, however scientists still don't fully understand the role of the DNA, and all of its genes. Therefore it is impossible to assess the risks from mis-targeted changes in the DNA sequence, which would affect both the treated embryo and any future generations.”
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Prof Shirley Hodgson, Professor of Cancer Genetics, St George’s University of London, said:
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“I think that this is a significant departure from currently accepted research practice. This is because any manipulation of the germline of human embryos is potentially heritable. Can we be certain that the embryos that the researchers were working on were indeed non-viable? In the past all the gene therapy research that has been approved by regulatory bodies has been somatic, not germline, because of the potentially unpredictable and heritable effects of germline research. The fact that these researchers found that there were a number of "off target" mutations resulting from the technique they used is clearly a worry in this context. Any proposal to do germline genetic manipulation should be very carefully considered by international regulatory bodies before it should be considered as a serious research prospect. This is because of the obvious concerns about the heritability of the genetic alterations induced, and the way in which such research could spread from work on "non-viable" embryos, to work on viable ones once this type of research had been accepted in principle by international regulatory bodies.”
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Prof Darren Griffin, Professor of Genetics, University of Kent, said:
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“Given the widespread use of the CRISPR/Cas9 system, such announcement was inevitable, sooner rather than later. We clearly have a lot of thinking to do. Germline manipulation is currently illegal in the UK but the question is bound to be asked whether this should change, especially if the safety concerns are allayed.
“If the technology is proved to be safe, then the question moves to whether it crosses a moral boundary to apply this technology in the clinic. Equally, some will ask if the procedure is safe, do we have a moral imperative to make sure that we do it.”
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Mr Alastair Kent OBE, Director of Genetic Alliance UK, said:
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“Families with a life-limiting genetic disease reading of this research will be interested to learn that it has been done, but will be only too aware of the scientific difficulties that will need to be overcome, and the ethical challenges that will need to be resolved, before it could be postulated as a potential therapeutic intervention for use in embryos destined for implantation in a woman through IVF. If there is to be further development of this work it will be essential that the experimental data is fully accessible so the methodology can be scrutinized carefully before further work that moves this closer to patients is contemplated. Failure to do this will render patients and families vulnerable, and risk bringing the wider field of gene transfer for serious diseases into disrepute.”
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Prof Bruce Whitelaw, Professor of Animal Biotechnology at the Roslin Institute, University of Edinburgh, said:
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“The story reported in Nature News yesterday adds to the expanding uses of the genome editor technology while emphasising that for many applications technical improvements are needed. Genome editing is an exciting technical tool but it is still in the development phase. Those working with these tools need to strive to improve efficiency, investigate specificity and appropriately demonstrate the range of applications possible which must come through transparent research activity. For genome editing to deliver the many benefits it offers, we need multi-stakeholder governance of how we want to use it.”
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Dr Philippa Brice, PHG Foundation, said:
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“This story underlines the urgent necessity for international dialogue over the ethics of germline gene editing in human embryos, well in advance of any progression towards theoretical clinical application. Recent calls for a moratorium on any such research to allow time for expert and public consideration of what is and is not ethically, socially and indeed legally acceptable with respect to human germline genetic modification should definitely be heeded.”
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Dr Hannah Brown is a researcher at the Robinson Research Institute, the School of Paediatrics and Reproductive Health at the University of Adelaide and the ARC Centre of Excellence for Nanoscale BioPhotonics. Her research focuses on the earliest stages of embryo development, and more specifically, how the first 5 days of life establish the trajectory for that embryo through into adulthood.
“New genome editing tools including the CRISPR/Cas9 have created great excitement for biological scientists in many fields. This technology allows researchers to use these molecular scissors (originally derived from bacteria) to remove and replace information in the DNA, not unlike cutting and pasting information from a word document. This technology provides the possibility to replace faulty genes (or the DNA sequence that give us a particular characteristic) to “erase and repair” the faulty information causing disease. Researchers have been using these molecular scissors routinely in human cells in a dish and in animal models, and even in animal embryos, but the research published in Protein Cell by the Chinese researchers is the first describing the technology in human embryos.
The research is highly controversial for a number of reasons. Firstly, research on human embryos is heavily restricted in Australia, and in other countries some level of regulation occurs. Secondly, the ethical justification that the Chinese group used for performing this research in human embryos was that they used embryos that would not be able to yield a viable pregnancy. In this case, they used donor embryos from a fertility clinic which has been fertilised by multiple sperm (the egg is very effective at stopping the penetration of more than one sperm at fertilisation, but occasionally this mechanism fails, and a “2-sperm fertilised” embryo with too much DNA is formed – these are not viable).
Finally, and perhaps the most concerning part of the research is the report of a large number of “off target” effects, meaning that their cut and paste editing occurred in the wrong place in the DNA, which was completely out of their control. It is my current opinion that this type of research in human embryos must advance with extreme caution and that the statement in the abstract that this technology “holds tremendous promise for…clinical research”, at least in reference to human embryos, is misleading and irresponsible at this point in time.”
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Associate Professor Peter Illingworth is Medical Director at IVFAustralia
“This is a fascinating piece of experimental science. Using abnormally-fertilised human embryos (I.e. With three sets of DNA instead of two), they have studied whether the a human gene can be modified. They have demonstrated that, in some embryos, but not all, they can change the abnormal human gene. They also find that other genes are affected which may be a serious concern. What they have shown is that it is technically possible, not that it is practically feasible or safe.
Currently, in Australia, it is a normal practice to test embryos from people who carry genes for serious disorders such as b-thalassaemia. This can identify which embryos are affected by the disorder and which are not. However, the capacity to actually change the embryos to get rid of the disorder would be an enormous step forward. However, as illustrated by this paper, the safety of such technologies is a major question mark and, interesting as this research is, much more research is needed to assess the feasibility and the safety of this technology
There is also the serious ethical issue of whether this is genetic engineering. However, provided the use of such technology is limited to serious genetic conditions such as beta thalassaemia, if the technology can be shown to be safe and effective, this should not prohibit the future use of the technology.”
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Dr Mel McDowall is an ARC Senior Research Associate at the ARC Centre of Excellence for Nanoscale BioPhotonics and the Robinson Research Institute and School of Paediatrics and Reproductive Health at the University of Adelaide
“CRISPR technology involves using modified viral DNA that contains the gene of interest (in this case beta-thalassaemia). This is called “transfection”. As indicated within the article, the technology in its infancy and targeting a single gene without introducing the viral genes into the human genome is very very risky. While the concept is very attractive, the risk at this stage is too high. I can see some major flaws in the study, a major being that “non-viable” embryos were used. These would be deemed “unhealthy” or compromised by an embryologist, hence the starting material is not optimal. Secondly, there are very robust and widely available genetic tests for genetic disorders (Preimplantation genetic diagnoses, PGD), where a cell biopsy or part of the embryo is tested and this is commonly used in clinical embryology. In regards to Australia, the federal government has very tight regulations on research involving human embryos, hence it is very unlikely that this kind of research and clinical application would occur in the short and even long term.
My general feeling about the article is that it is a bit of a sensational piece.”
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Dr Kuldip Sidhu is a stem cells expert at the Centre for Healthy Brain Ageing at UNSW
“CRISPR/Cas9-mediated gene editing is an important emerging technology that Liang group in this paper has used in human tripronuclear zygotes (3PN) to correct β-globin gene mutation that causes β-thalassemia. They used discarded human zygotes that were resulted from eggs fertilized by two sperm and hence 3PN zygotes. These 3PN zygotes though abnormal can produce blastocysts. They have demonstrated that in addition to gene correction at the relevant site in few zygotes, it also caused insertion at the non-site targets of the genome hence raised alarmed about CRISPR/Cas9 technology. Though they had limitation in using 3PN abnormal zygotes in this study, it would have been worth awhile to extend this study by producing blastocysts from these zygote and derive embryonic stem cells thus trace the outcome of this technology at the relevant cellular level.”
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