Gene editing is a technology through which a scientist can add, remove or alter genetic material at a particular location in the genome of a living organism affecting its behaviour at genetic level.
Genetically modified microorganisms, plants and animals have been developed with desirable traits using various technologies.
Some of the products have been accepted for public use after thorough scrutiny at technical level and controlled field tests. The methods used earlier for gene editing to develop genetically modified organisms were imprecise, cumbersome and time consuming.
A new gene editing technology known as Clustered Regularly Interspersed Short Palindromic Repeats (CRISPR) is now available and offers a targeted, cheap, accurate and faster technology for gene editing as compared to others.
This technology has been borrowed from bacteria, who use CRISPR/Cas9 mechanism to protect themselves from attack by harmful viruses. When bacteria are attacked by a virus they cut a piece of viral DNA and incorporate it in their own DNA as CRISPR arrays.
During the next attack they recognise the virus and as a defence mechanism use an enzyme known as Cas9, which acts as a molecular scissor. It is guided by a small piece of guide RNA to a desired location where it cuts the two strands of viral DNA and disables it.
This technique used by bacteria has been thoroughly studied and is now used to cut the DNA of an organism at a desired location. The natural DNA repair mechanism of the cell is then utilised to insert another piece of DNA with known sequence in the gap. This alters the function of the DNA as desired by the scientists. There are rapid developments on improving CRISPR/Cas9 technology. Gaudelli and co-researchers reported in the journal, Nature (November, 2017), that they could change the bases AT to GC in the genomic DNA without DNA cleavage using a catalytically impaired CRISPR/Cas9.
Extensive uses of the technology have been made in plants. Genes of several plants have been modified to improve their nutritive value, make them more palatable, augment their resistance to pest attacks, increase their yields and fertiliser use efficiency (Aurora and Narula, 2017).
Specific genes of several crops such as rice, wheat, cotton, tobacco etc. have been modified with CRISPR technique to make them resistant against some of their common diseases.
Recently (March 2018), a group of Chinese scientists modified the tillering genes of rice with CRISPR/Cas9, which resulted in higher grain yield and increased nitrogen use efficiency of the crop. Climate change has made it imperative to grow corn under long -day conditions at higher latitudes. Under these conditions flowering of corn gets delayed. The flowering gene of corn has now been suitably modified by CRISPR/Cas9 technology to make it flower earlier (Cheng Huang, 2018).
The CRISPR technology has been used successfully on animals such as, rabbit, swine, cattle, sheep and goat to edit their genomes to produce animal products of better quality. Governments around the world are hesitant to permit public use of these products afraid of unpredictable consequences.
Genetically modified animals can be used as bio-models to study human physiology and disease, as bioreactors to produce complex proteins and as organ donors for transplant (lamas-Toranzo and coresearchers, 2017).
The CRISPR could be used in human reproductive cells called embryos (germline cells), to incorporate certain desirable traits, which can be passed on to future generations. This has triggered ethical concerns. Would it be permissible to change current human traits and produce ‘Designer Babies’IJ Based on such concerns, germline editing has been banned and declared as illegal in more than 40 countries in Europe by a binding international treaty.
Human embryos, which would not develop into babies are only allowed to be edited. However, lichun Tang and co-researchers of Beijing Proteome Research Centre (March, 2017), corrected disease-causing mutations in a small number of viable human embryos using CRISPR/Cas9 technology. Kathy Niakan of the Francis Crick Institute in london used CRISPR/Cas9 to intentionally snip DNA to create mutation in human embryos.
It is now possible to change the human genome not only for a life time but stretch it into future generations to create a new class of genetically enhanced people. If allowed, it may create a new market-based industry in eugenics (improved population by controlled breeding).
The US National Academy of Sciences, Engineering and Medicine has warned against use of CRISPR to enhance health or other human traits.
No babies have been born so far with desirable changes made by CRISPR/Cas9 technology of gene editing. CRISPR pioneer, Jennifer Doudna of the University of California, Berkley, while addressing the World Conference of Science Journalists on October 26, 2017 said that “I would not be surprised if there were a CRISPR modified baby somewhere in the world in the next couple of years”.
Mildred Solomon, a bio-ethicist and president of Hastings Centre of Bioethics Research Institute of Garrison, NY says, “We can now literally change our own species (2017).”
A panel of ethicists on human gene editing opined that under certain circumstances such as to correct genetic diseases, human gene editing should be permissible. There are a number of genetic diseases caused by single gene mutation such as cystic fibrosis, haemophilia and sickle cell anaemia, where gene editing could be done by CRISPR/Cas9 technology.
This technology could also be used for treatment and prevention of more complex diseases, such as cancer, heart diseases, mental illness and HIV (Human immune deficiency virus). However, one needs to be cautious. Chinese Scientists, who altered the gene, which cause the blood disorder called beta thalassemia found that other genes, which they did not intend to touch were also affected (April, 2015).
There are beneficial uses of CRISPR technology as well. Recently, a CRISPR technology has been developed for diagnosis of diseases (April, 2017). It is a rapid, inexpensive, highly sensitive diagnostic tool with the potential to transform research and management of global public health.
A group of scientists from the Broad Institute of MIT and Harvard, the McGovern Institute for Brain Research at MIT, the Institute for Medical Engineering and Science at MIT, and the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a CRISPR/Cas13a based test named as SHERlOCK(Specific High-sensitivity Enzymatic Reporter unlOCKing).
The test is paper-based, does not require refrigeration and suitable for use in field hospitals. The test is reported to be million-fold more sensitive.
This test has a wide range of applications such as, detecting presence of Zika virus in patient’s blood or urine samples within hours, discriminating specific type of bacteria such as E Coli, detecting antibiotic resistant genes, identifying cancerous mutations in simulated cell-free DNA fragments, and rapidly reading human genetic information to detect possible risk of heart disease from a saliva sample.
The CRISPR technology can be used for welfare of human beings but has the potential to create a new human race with enhanced traits.
There can be negative uses of this technology by rogue States as has happened with many of the modern scientific discoveries. A firm and binding international decision has to be taken, since scientists in countries with lax laws have already started experimenting with viable human embryos.
(Prof Mitra has a PhD in Biochemistry and taught the subject for 25 years. email:gnmitra@gmail.com)