I’m sure many of you have heard about the CRISPR story in the news. A Chinese scientist, He Jiankui of the Southern University of Science and Technology, claims to have created the first gene-edited babies. It was recently disclosed that genomes of two twin girls, conceived using IVF, had been modified to make them resistant to HIV. However, there is no official proof yet and the case is being investigated. I want to use this space to share what I’ve learned about CRISPR in general and the ethical implications related to human genome editing.
What is CRISPR?
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) are a bacterial defense system that forms the basis for CRISPR-Cas9 genome editing technology. This system can be programmed to target specific stretches of genetic code, edit DNA at precise locations, and can also be used for new diagnostic tools. With these systems, genes in living cells and organisms can be permanently modified. In the future, it may even be possible to correct mutations at precise locations in the human genome in order to treat genetic causes of diseases.
CRISPRs were first discovered in archaea and were thought to serve as part of the bacterial immune system, defending against invading viruses, They consist of repeating sequences of genetic code, interrupted by “spacer” sequences (remnants of genetic code from past invaders – the system serves as a genetic memory). This helps the cell detect and destroy the bacteriophage when it returns.
In the video below, Feng Zhang, pioneer of development of genome editing tools from natural microbial CRISPR-Cas9 systems, provides a simple explanation of CRISPR:
In January 2013, the Zhang lab published the first method to engineer CRISPR to edit the genome in mouse and human cells. At the International Summit on Human Gene Editing in 2015, there was a consensus for holding off human genome editing until the implications were fully considered. So given the recent news, I looked into some of the ethical issues related to genome editing and came across a paper by Rodriguez 2016 which will be briefly presented here.
- Balance of risks and benefits
- Application of CRISPR/Cas9 technique involves risk of off targe mutations which can be harmful. Additionally, large genomes may contain multiple DNA sequences identical to intended target DNA sequence. These unintended sequences could be split causing cell death or tranformation.
- Ecological disequilibrium
- The possibility of off target mutations may increase each generation. If there is a risk of transferring genes to other species, then there is a risk of transferring modified sequences (passing the negative trait) to related organisms which could lead to the disappearance of a whole population. This would have drastic consequences on the ecosystem equilibrium, e.g., other plagues may be developed.
- Informed consent
- For human germline therapy, it would impossible to obtain informed consent because the patients affected by the edits are the embryo and future generations.
- Justice and equity
- There is concern that genome editing might only be accessible to the wealthy which would increase the existing gap in access to health care. Furthermore, this could create classess on individuals defined by the quality of their engineered genome.
- Genome editing for enhancement
- Even though the goal is to use genome editing for improving health of patients, there is a possibility of non-therapeutic interventions. For example, it could be used to enhance performance of athletes or to prevent violent behaviour or diminish addictions. Socially, there will be a problem if some individuals may be enhanced genetically giving them an upper hand over others, for example in intellectual capacity. The latter ties in with the justice and equity part.
There needs to be a discussion about the social, ethical, and legal implications of using genome-editing techniques in human germline and other organisms. There are many factors and risks associated with it which will spiral out of control without definitive boundaries and regulations.