We need to talk about CRISPR

By Gesa Junge, PhD

You’ve probably heard of CRISPR, the magic new gene editing technique that will either ruin the world or save it, depending on what you read and whom you talk to? Or the Three Parent Baby, which scientists in the UK have created?

CRISPR is a technology based on a bacterial immune defense system which uses Cas9, a nuclease, to cut up foreign genetic material (e.g., viral RNA). Scientists have developed a method by which they can modify the recognition part of the system, the guide RNA, and make it specific to a site in the genome that Cas9 then cuts. This is often described as “gene editing” which allows disease-causing genes to be swapped out for healthy ones.

CRISPR is now so well known that Google finally stopped suggesting I may be looking for “crisps” instead, but the real-world applications are not so well worked out yet, and there are various issues around CRISPR, including off-target effects, and also the fact that deleting genes is much easier than replacing them with something else. But, after researchers at Oregon Health and Science University managed to change the mutated version of the MYBPC3 gene to the unmutated version in a viable human embryo last month, the predictable bioethical debate was reignited, and terms such as “Designer Babies” got thrown around a lot.

A similar thing happened with the “Three Parent Baby,” an unfortunate term coined to describe mitochondrial replacement therapy (MRT). Mitochondria, the cells’ organelles for providing energy, have their own DNA (making up about 0.2% of the total genome) which is separate from the genomic DNA in the nucleus, which is the body’s blueprint. Mitochondrial DNA can mutate just like genomic DNA, potentially leading to mitochondrial disease, which affects 1 in 5000-10000 children. Mitochondrial disease can manifest in various ways, ranging from growth defects to heart or kidney to disease to neuropsychological symptoms. Symptoms can range from very mild to very severe or fatal, and the disease is incurable.

MRT replaces the mutated mitochondrial DNA in a fertilized egg or in an embryo with the healthy version provided by a third donor, which allows the mitochondria to develop normally. The UK was the first country to allow the “cautious adaption” of this technique.

While headlines need to draw attention and engage the reader for obvious reasons, oversimplifications like “gene editing” and dramatic phrases like “three parent babies” can really get in the way of broadening the understanding of science, which is difficult enough as it is. Research is a slow and inefficient process that easily gets lost in a 24-hour news cycle, and often the context is complex and not easily summed up in 140 characters. And even when the audience can be engaged and interested, the relevant papers are probably hiding behind a paywall, making fact checking difficult.

Aside from difficulties communicating the technicalities and results of studies, there is also often a lack of context in presenting scientific studies – think for example of chocolate and red wine which may or may not protect from heart attacks. What is lost in many headlines is that scientific studies usually express their results as a change in risk of developing a disease, not a direct causation, and very few diseases are caused by one chemical or one food additive. On this topic, WNYC’s “On The Media”-team have an issue of their Breaking News Consumer Handbook that is very useful to evaluate health news.

The causation vs. correlation issue is perhaps a little easier to discuss than big ethical questions that involve changing the germline DNA of human beings because ethical questions do not usually have a scientific answer, let alone a right answer. This is a problem, not just for scientists, but for everyone, because innovation often moves out of the realm of established ethics, forcing us to re-evaluate it.

Both CRISPR and MRT are very powerful techniques that can alter a person’s DNA, and potentially the DNA of their children, which makes them both promising and scary. We are not ready to use CRISPR to cure all cancers yet, and “Three Parent Babies” are not designed by anyone, but unfortunately, it can be hard to look past Designer Babies, Killer Mutations and DNA Scissors, and have a constructive discussion about the real issues, which needs to happen! These technologies exist; they will improve and eventually, and inevitably, play a role in medicine. The question is, would we rather have this development happen in reasonably well-regulated environments where authorities are at least somewhat accountable to the public, or are we happy to let countries with more questionable human rights records and even more opaque power structures take the lead?

Scientists have a responsibility to make sure their work is used for the benefit of humanity, and part of that is taking the time to talk about what we do in terms that anyone can understand, and to clarify all potential implications (both positive and negative), so that there can be an informed public discussion, and hopefully a solution everyone can live with.


Further Reading:


National Geographic

Washington Post


Mitochondrial Replacement Therapy:

A paper on clinical and ethical implications

New York Times (Op-Ed)


Engineering Babies One Crispr at a Time


By Sophie Balmer, PhD

Over the past few weeks, the scientific community has been overwhelmed with major advances in human embryonic research. Whether researchers report for the second time the use of Crispr to edit the human germline or extend the conditions of in vitro culture of human embryos (also here), these issues have been all over the news. However, as all topics can not be raised in only one post, therefore, I will focus on genome editing studies.


About a year ago, one research group in China reported the first genome editing of human embryos using Crispr technology. Although these embryos were not viable due to one additional copy of each chromosome, this study quickly became highly controversial and raised strong concerns. The public and scientific communities questioned whether editing the human germline for therapeutic benefits was legitimate, leading to numerous ethical discussions. A few of weeks ago, a second study reported genome editing of embryos reinforcing the debate around this issue. Additionally, several research proposal involving genomic modification of healthy human embryos’ DNA have been validated recently in other countries. In this post, I want to address several questions. What are the possible advances or consequences of such work? What is the current legislation on human genome editing worldwide? Are these studies as alarming as what is written in some newspaper articles?


The emergence of the Crispr technology a few years ago has revolutionized the way scientists work since this method greatly improves the efficiency of DNA alteration of model organisms. However, this powerful tool has also raised many concerns, notably on the possibility to easily tweak the human genome and generate modified embryos.

In the eyes of the general public, this kind of experiment resonates with science fiction books or movies. Because of the high potential of this technique, it is crucial to inform everyone correctly to avoid clichés. Recently, one of my favorite comedian and television host John Oliver depicted in a very bright and amusing way how small scientific advances are sometimes presented in the media. Although the examples he uses are dramatic, every scientific breakthrough gets its share of overselling to the public. In the case of gene-editing of human embryos, pretending we are about to use eugenics principles to engineer babies and their descendants with beneficial genes is pure fiction. However, to prevent any potential malpractice from happening, clear ethical discussions and regulations need to be established and then explained to the public to prevent misunderstanding of these issues.

Within the scientific community, last year’s results triggered the need for new discussions and regulations on human cloning. Modifying the genome of human embryos involves modifying the germline as well, leading eventually to the transmission of the genetic alteration to future generations. However, the consequences of such transmission are unknown. Potentially, this could resolve a number of congenital genetic diseases for the individual him/herself and be used for gene therapy but would result in generations of genetically modified humans.


Because of cultural and ethical differences between countries, the legislation (if there is any) around working with human embryos or cells derived from human embryos (hESC for human embryonic stem cells) is variable. International ethical committees have only been able to establish guidelines as instituting international laws on human cloning is impossible. Ultimately, each country is responsible for enforcing these rules. Most countries and international ethics committees agree on a ban on reproductive and therapeutic human cloning. Moreover, following last year published experiments, a summit held in December 2015 gathered experts from all around the world. The consortium concluded that gene-editing of embryos used to establish pregnancy should not be performed (for now) and to follow up on all-related issues, new sets of guidelines are coming out imminently.


Still, it seems difficult to get an idea of the consensus depending on the countries in which scientists perform experiments. There is range of possibilities when working with human samples: some countries completely prohibit any manipulation of human embryos or hESC while others authorize genetic modification of the embryo for research purposes only under specific conditions. In between several nations authorize research exclusively on already derived lines of hESC and others authorize derivation of hESC but no manipulation of the embryos themselves.

Besides these general rules and as of today, three countries have approved proposals for gene-editing of human embryos: China, the UK and Sweden. Research proposals in both European countries have authorized Crispr targeting of specific genes in healthy human embryos to assess the function of these genes during early human development. However, these embryos can not be used for in vitro fertilization (IVF) and have to be destroyed at the end of the study. The purpose of these studies would be to confirm what has been described in hESC and in mammalian model systems and contribute to our knowledge of human development.


On the other hand, both published studies from China focused on Crispr targeting towards clinical therapies of an incurable blood disease or HIV. The overall purpose of such projects is to test the use of the Crispr technology for gene therapy. Although rendering embryos immune to several diseases using Crispr is an attractive possibility, it seems more urgent to probe the validity of the technique in humans and assess whether the mechanisms of human embryonic development are similar to what has been hypothesized. Gene therapies have already been successfully attempted in humans using other techniques to modify the genome. Yet, the modifications were targeted towards specific cells in already-born individuals. Again, modifying the genome of embryos implies that the mutation will be inherited in future generations and is in a large part the reason of this debate. Moreover, Crispr targeting still leads to unspecific modification of the genome, although very promising results show that newly engineered cas9 could lead to very specific targeting. The consequences of such off-target modification are unknown and could be disastrous for the following generations.


Overall, no research proposal dares to consider genetically modified embryos to establish pregnancy but as research moves faster, increasing demand for ethical discussion and regulations are brought forward. As more studies come out, it will be interesting to follow the evolution of this debate. Additionally, informing clearly the population of the possibilities and outcomes of ongoing projects should be a priority so that they can give an informed consent towards such research. In any case, a clear boundary needs to be established between selecting the fittest embryo by pre-implantation genetic diagnosis, which is routinely performed for IVF and playing the sorcerer’s apprentice with human embryo’s