CRISPR/ Gene Editing

In News

• Recently, the gene-editing technology which has led to innovations in medicine, evolution and agriculture has completed 10 years of innovation.

About Gene Editing

• Gene/genome editing refers to technology that permits to change an organism’s DNA.
  • These technologies allow genetic material to be added, removed, or altered at particular locations in the genome.
  • Its applications include correcting genetic defects, treating and preventing the spread of diseases and improving crops etc.
• Discovery :
  • A decade ago, scientists in Germany and the US discovered a technique which allowed them to ‘cut’ DNA strands and edit genes. 
    • For agriculture scientists this process allowed them to bring about desired changes in the genome by using site directed nuclease (SDN) or sequence specific nuclease (SSN). 

• Nuclease is an enzyme which cleaves through nucleic acid — the building block of genetic material.

• Advanced research has allowed scientists to develop the highly effective clustered regularly interspaced palindromic repeat (CRISPR) -associated proteins based systems. 
  • This system allows for targeted intervention at the genome sequence.
  • This tool has opened up various possibilities in plant breeding. Using this tool, agricultural scientists can now edit the genome to insert specific traits in the gene sequence. 
• Depending on the nature of the edit that is carried out, the process is divided into three categories — SDN 1, SDN 2 and SDN 3.
  • SDN1 introduces changes in the host genome’s DNA through small insertions/deletions without introduction of foreign genetic material. 
  • In the case of SDN 2, the edit involves using a small DNA template to generate specific changes. 
    • Both these processes do not involve alien genetic material and the end result is indistinguishable from conventionally bred crop varieties.
  •  The SDN3 process involves larger DNA elements or full length genes of foreign origin which makes it similar to genetically modified organisms (GMO) development.

Applications

• Animal models: CRISPR-Cas9 can be used to create animal models to mimic human diseases and to understand disease development by mutating or silencing genes.
• Genome editing in specific tissues: Researchers have been able to modify the genomes of specific tissues such as liver and brain tissues using hydrodynamic injection and adeno-associated virus (AAV).
• Multiple gene mutations: CRISPR-Cas9 can be used to generate mutants for target genes.
• Treatment of diseases: CRISPR-Cas9 can be applied to cells in vivo or ex vivo. In the in vivo approach, CRISPR-Cas9 is directly transferred to cells in the body using either viral or nonviral methods. In the ex vivo approach, first the cells are removed from the body; then CRISPR is applied to the cells and they are transferred back to the body.
• Industrial uses: CRISPR was first used for commercial purposes to make bacterial cultures used in cheese and yoghurt production resistant to viral infections.
• RNA editing: Single-stranded RNA (ssRNA) sequences can also be edited by CRISPR-Cas9.
• Military applications: These studies are commonly focused on increasing the tolerance of soldiers against biological or chemical warfare. This technology has the potential to influence human performance optimization.

Pros of Gene Editing

• Tackling and Defeating Diseases: Most deadly and severe diseases in the world have resisted destruction. A number of genetic mutations that humans suffer will end only after we actively intervene and genetically engineer the next generation.
• Extend Lifespan: Genome editing could extend the human lifespan. The human lifespan has already shot up by a number of years, and we are already living longer and longer.
• Growth in Food Production and Its Quality: Genetic engineering can design foods that can withstand harsh temperatures and are packed full of all the right nutrients.
• Pest Resilient Crops: genome editing can address pest and nutrition challenges facing agriculture. Instead of using tons of insecticides and pesticides, we can protect our plant in a healthier way.

Cons of Gene Editing

• Ethical Dilemma: modification is unnatural and amounts to playing God.
• Safety Concerns: Slight changes made at the smallest level may lead to unexpected results.
• Diversity: Diversity in all species of animals is a key to evolution on earth. Genetically engineering our species will have a detrimental effect on our genetic diversity- as in something like cloning would.
• Rich people’s tool: gene therapy is costly.

How is gene editing different from GMO development?

• Genetically modified organisms (GMO) involve modification of the genetic material of the host by introduction of a foreign genetic material.
•  In the case of agriculture, soil bacteria is the best mining source for such genes which are then inserted into the host genome using genetic engineering. 
  • For example, in case of cotton, introduction of genes cry1Ac and cry2Ab mined from the soil bacterium Bacillus Thuringiensis (BT) allow the native cotton plant to generate endotoxins to fight pink bollworm naturally.
  •  BT Cotton uses this advantage to help farmers naturally fight pink bollworm which is the most common pest for cotton farmers.
• The basic difference between genome editing and genetic engineering is that while the former does not involve the introduction of foreign genetic material, the latter does. 
• In the case of agriculture, both the techniques aim to generate variants which are better yielding and more resistant to biotic and abiotic stress. 
• Before the advent of genetic engineering, such variety improvement was done through selective breeding which involved carefully crossing plants with specific traits to produce the desired trait in the offspring. 
• Genetic engineering has not only made this work more accurate but has also allowed scientists to have greater control on trait development.

Conclusion

• Many countries and laws have already been put forward to bring the best outcome. With proper laws and control over its usage, it will definitely be a huge gift for humankind.

Source: NY