Discussion around CRISPR-Cas9 genome editing has become increasingly popular in the past two years, yet it is a mechanism that is poorly understood by those who may not have the patience to dig through papers full of genetic jargon. Short for Clustered Regularly Interspaced Short Palindromic Repeats, it is a piece of technology that allows scientists to ‘cut and paste’ pieces of DNA, enabling the editing of genomes at will.
A Brief Introduction to Genetics
“Genetics is the study of how living things receive common traits from previous generations.” Your genome, as well as those of all humans, animals, and plants, is made up of DNA (deoxyribonucleic acid). DNA is located in all living cells, and contributes to the construction of genes. These genes determine your particular traits, and when all combined, make you who you are.
Half of your genetic material is transferred to you by each of your parents. Genes such as BRCA1 have been linked to a greater likelihood of developing breast cancer, but much more research needs to be done to uncover the origins of many other diseases and disorders. And this is where CRISPR comes in.
What can it do?
CRISPR may just hold the key to finding genetic causes for diseases and even treatments, but it also has the possibility to wipe out entire populations of crops or animals. It will be able to save scientists both money and time, and indeed, scientists have already been successful in partially treating some forms of muscular dystrophy in mice by using CRISPR/Cas9 to cut out a defective section of DNA that causes the disorder!
On the other hand, there are broad (and genuine) concerns that abuse of this power may lead to the creation of so-called designer babies. However, it must be noted that there is a fine line between using this technology for gene therapies in humans and intentional (malicious or otherwise) genetic manipulation. Experimentation with human DNA, no matter how well intentioned, may have wide ranging and unpredictable genetic effects on future generations. David Lemberg, the founding editor of Bioethics Today, put it quite succinctly, “just because we can do a thing doesn’t mean we should do the thing”.
What has been done?
Applications for the use of such a technique on human embryos have already been made, with the Francis Crick Institute in London being one notable example. This particular application has been accepted, to a variety of reactions around the world – though this was expected. Many scientists will no doubt have their eyes and ears peeled for any results from this lab, whether they be positive or negative.
Even though the Crick Institute may only be using such embryos for the sole purpose of research, this ignited debate through the scientific community regarding the use of CRISPR/Cas9 for clinical applications. Many scientists are also worried about private biotechnology companies using and appropriating such technologies and techniques for nefarious purposes.
A group of Chinese researchers reported the use of CRISPR/Cas9 in non-viable human embryos (human embryos that would never be able to become a physical human being) in 2015 in order to potentially treat beta thalassemia, a genetically inherited blood condition.
The use of human embryos, including human embryonic stem cells, has long been an ethical issue for scientists. Some consider the use of such cells as the equivalent of destroying a potential human being, while others argue that such research could have the potential to save many more human lives down the track.
In any case, the Chinese study was published to much controversy, even after several scientists had written editorial in Nature, calling for their colleagues to err on the side of caution when considering the use of CRISPR to modify the human genome. It is interesting to note that this study did not yield any particularly conclusive results, but did show that use of CRISPR/Cas9 still needed to be refined so it did not cause more harm than good. Interestingly, both Nature and Science refused to publish the paper on account of its controversial nature, and the repercussions of this study will probably be around for years to come.
CRISPR can also be used on animals and plants!
Even though most of the discussion around the use of CRISPR/Cas9 is centred around its application in humans, it can also have wide ranging effects on animals and plants. There have been suggestions that it can be used to eradicate diseases like malaria and possibly even the Zika virus, which is currently reaching endemic levels in the Americas. Scientists have already edited genomes of plants such as tobacco and rice without the introduction of any foreign DNA. This has put most of the concerns around genetically modified crops to rest, and may also lead to the introduction of healthier and more viable crops in countries where food is scarce.
However, it can also wipe out total populations, by cutting out genes that make one species of animal or plant different from its relations.
What are the possibilities?
Opportunities abound as a result of this technology, including the development of software to predict possible outcomes of genetic engineering (http://www.deepgenomics.com/ and https://www.23andme.com). It is both an exciting and frightening time for geneticists and the wider scientific community. There is the potential to do much good, but also much harm. There are many reasons mice are used as experimental models, but human DNA is more complex and continues to surprise scientists to this day. As a result, most scientists are cautiously optimistic about the future of CRISPR/Cas9 and its impacts on the world at large.
Kathy Niakan, a group leader at the Francis Crick Institute, is diplomatic but honest about the future of such research, telling The Guardian, “There are suggestions that the methods could be used to correct genetic defects, to provide disease resistance, or even to introduce novel traits that are not found in humans. However, it is up to society to decide what is acceptable: Science will merely inform what may be possible.”
It is a big decision for society to make – and we can only hope that in time, society manages to make the right ones.