CRISPR/CAS9 Technology: Meaning, Scope, Ethical and Safety Concerns

CRISPR/CAS9 is a new gene-editing technology that promises to revolutionize the genetics field. Using this technology, genes of any living organism can be edited at a faster and cheaper rate than the present technologies. By comparison, older gene-editing tools are cumbersome, inaccurate and inefficient. CRISPR as a tool has been seen as a potential solution to eradicate diseases like malaria, yellow fever, and zika virus. In addition to these, different congenital disabilities could also be avoided. The scientists from developed countries like China and USA have been permitted to try CRISPR on humans to find cure for cancer.

Discovery of the technology

In 1987 a group of scientists from Japan observed a strange pattern of DNA sequences in a gene of gut bacteria E.coli. They noticed that the gene had 5 short repeating segments of DNA separated by short non-repeating ‘spacer’ DNA sequences. The 5 repeating segments had identical sequences composed of 29 bases whereas each of the ‘spacer’ sequences had their own unique sequence, composed of 32 bases. Scientists had never seen such a pattern before. By the end of the 1990s, it was discovered that this pattern of DNA sequences were prevalent in many different bacterial species. Scientists have given the name to this pattern as ‘Clustered Regularly Inter-spaced Short Palindromic Repeats’ or CRISPR for short.

In 2002, scientists observed that another set of sequences always accompanied the CRISPR sequence. These second sets of sequences are named as ‘CRISPR-associated genes’, or CAS genes. By 2005 it was identified that the ‘spacer’ sequences between the CRISP sequences shared similarities with the DNA of viruses and they play an important role in the defence system of bacteria. On further research it was noticed that the bacteria were inserting DNA fragments from the attacking viruses into their ‘spacer’ sequences. And these ‘spacer’ sequences forms the memory of past virus invaders and also guide the CAS9 enzyme to cut the genome of invading viruses.

In 2008, for the first time how the CRISPR/Cas9 mechanism works was demonstrated. Whenever a virus attacks bacteria, the bacteria will copy and incorporate the Virus DNA segments into their genome as ‘spacers’ between the short DNA repeats in CRISPR. The ‘spacers’ provide a template for the bacteria’s RNA molecules to recognize the future invading viruses. The ‘spacers’ also guide the Cas9 enzyme to cut the genome of the invading virus and stop the process of further replication of the virus.

In 2012, a research paper was published on how to use CRISPR/Cas9 system as a precise tool to cut any DNA strand in a test tube. A year later, several papers were published demonstrating how the CRISPR/Cas9 system could be used to edit genomes in human cells.

Importance of the technology

The CRISPR/CAS9 technology is one of a number of gene-editing technologies. Compared to the other technologies, the CRISPR/CAS9 technology offers high degree of flexibility and accuracy in cutting and replacing/pasting of DNA. Other reason for its popularity is that it makes it possible to carry out genetic engineering on an unprecedented scale at a very low cost. It differs from other genetic engineering techniques is that it allows for the introduction or removal of more than one gene at a time. This makes it possible to modify many different genes very quickly and thus reduces the time taken for manipulation from number years to few weeks. This technique is not species-specific, so it can be used on organisms previously resistant to genetic engineering.

Applications of the technology

• The technology can be used in many industrial processes that use bacterial cultures. It can be used to make bacterial cultures more resistant to attacks from viruses. This will increase the productivity. It can also be used for quality and quantity improvement of foods like cheese and yoghurt.
• In agriculture it will help in design of new variety of grains, roots and fruits.
• The technology has been used to remove, insert and modify DNA in human cells and other animal cells grown in petri dishes.
• The technology is also used to create transgenic animals such as rats, mice, pigs and primates. Recently, scientists reported the successful use of the technology for prevention of muscular dystrophy and cure a rare liver disease in mice. The technology is also being used to make human cells immune to HIV. Malaria-resistant mosquitos are also being developed.
• Scientists are also working to create human organs from transgenic pigs by use of this technology in conjunction with pluripotent stem cells. This will helps us to solve some of the shortage of human organs for transplant operations and also in overcoming some of the side effects caused by organ transplantation such as graft-versus host disease.
• In context of health, the technology can help us to develop new treatments for rare metabolic disorders and genetic diseases ranging from haemophilia to Huntingdon’s disease.
• The technology is also being investigated to develop new methods in gene therapy to provide remedies for simple genetic disorders like sickle-cell anemia and eventually curing more complex diseases involving multiple genes. Existing gene therapy technologies place the new genetic material at a random location in the cell and can only add a gene whereas CRISPR technology gives us a precise way to delete and edit specific bits of DNA-even we can change a single base pair. That means we can rewrite the human genome at will.
• The technology can also be used in treatment of infectious diseases, by making more specific antibiotics that target only disease-causing bacteria while sparing beneficial bacteria. Several companies have started exploiting the technology commercially and large pharmaceutical companies are also exploring its use for drug discovery.

• The tool has already been used to alter genomes of plants thereby improving crops and providing resistance to crop diseases. Scientists claim that with this technology animal organ could be successfully transplanted into humans. DNA modification in human embryos is another possibility.

Issues

Like other gene-editing technologies, the CRISPR is also facing the issues. In April 2015, a group of Chinese Scientists had claimed the first application of the technology on human-embryos to cure a blood disorder. The technology is very inexpensive and is available to any researcher who wants to modify human-embryos. Thus, there are two major concerns with CRISPR viz. ethical and safety concerns.

Ethical Concerns

Amidst all the benefits that CRISPR has promised to bring, there are certain issues that have come under serious attacks. One of the main issues with this biotechnology tool is that the changing and editing of genes cannot be reversed, at least not till now. There could be adverse side effects, but those could be visible after decades. The “should we” and “shouldn’t we” regarding CRISPR is one of the main dilemmas. Will it be ethical to let millions of people die because there may be some side effects in future? The question remains…

Thus, there is a debate on to what extent the technology should be used to alter the ‘germ-line’ cells-eggs and sperm. Scientists including the inventor of the technology are urging for a moratorium on applying the technology to human ‘germ-line’ cells.

Safety Concerns

The other issue is related to the safety concerns. The technology is still in infancy stage and the consequences are unknown. The changes in one part of genome may cause changes elsewhere and it could result in unforeseen consequences. This is particularly important while applying the technique for human health related issues. There are also concerns that the application of the technology in agriculture may endanger biodiversity.

Conclusion

Gene modifications and editing is being speculated to go higher than just curing diseases. “Improvements” in human features could lead to discrimination and disparities. It may even be harmful for the entire human society. Continuous researches are being done to bridge the gaps between the “normal” and “modified” humans.

A lot of off-target mutations have been made on human embryos so far. As the technology is still not predictable and has a long way to go, editing human embryos is non-ethical. Safety in mutations is something that the scientists are looking for. A lot of research is going on to make CRISPR safe and as soon as it will be safe to mutate human genes, the ethical concerns will come to the forefront.  In the light of where CRISPR stands today it can be said that gene editing is not going to be limited to curing diseases. Rather, there would be many more milestones that biotechnology related to gene mutations are going to cross. Hopefully, it would be for the betterment of mankind.

GS Mains Question
What is CRISPR technology? What role can it play in medical science, industry and agriculture? Discuss while highlighting the various ethical and safety issues around this technology.