Precision-Guided Sterile Insect Technique (pgSIT)

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    • Recently, researchers have created a system that restrains populations of mosquitoes that infect millions each year with debilitating diseases. 

    Precision-guided sterile insect technique (pgSIT)

    • It alters genes linked to male fertility—creating sterile offspring—and female flight in Aedes aegypti, the mosquito species responsible for spreading diseases including dengue fever, chikungunya and Zika. 
    • It uses CRISPR to sterilise male mosquitoes and render female mosquitoes (which spread disease) flightless. 
    • Males don’t transmit diseases so the idea is to release more and more sterile males, so that the population can be suppressed without relying on harmful chemicals and insecticides.
    • The system is self-limiting and is not predicted to persist or spread in the environment, two safety features that should enable acceptance for this technology.
    • pgSIT eggs can be shipped to a location threatened by mosquito-borne disease or developed at an on-site facility that could produce the eggs for nearby deployment. 
    • Once the eggs are released in the wild, sterile pgSIT males will emerge and eventually mate with females, driving down the wild population as needed.

     

    (Image courtesy: Cambridge )

     

    CRISPR

    • CRISPR is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. 
    • These sequences are derived from DNA fragments of bacteriophages that had previously infected the prokaryote. 
    • They are used to detect and destroy DNA from similar bacteriophages during subsequent infections.
    • It’s a way of finding a specific bit of DNA inside a cell. After that, the next step in CRISPR gene editing is usually to alter that piece of DNA.
    • CRISPR-Cas9 technology behaves like a cut-and-paste mechanism on DNA strands that contain genetic information. The specific location of the genetic codes that need to be changed, or edited, is identified on the DNA strand, and then, using the Cas9 protein, which acts like a pair of scissors, that location is cut off from the strand.
    • Emmanuelle Charpentier of France and Jennifer A Doudna of the USA were awarded the 2020 Nobel Prize in Chemistry for developing CRISPR/Cas9 genetic scissors.

    Significance

    • pgSIT eggs can be shipped to a location threatened by mosquito-borne disease or developed at an on-site facility that could produce the eggs for nearby deployment. 
    • Once the pgSIT eggs are released in the wild, sterile pgSIT males will emerge and eventually mate with females, driving down the wild population as needed.
    • CRISPR technology is a simple and powerful tool for genome editing. It easily alters DNA sequences and modifies gene function. 
    • Its many potential applications include correcting genetic defects, treating and preventing the spread of diseases and improving crops. 

    Challenges

    • CRISPR: 
      • Problematic when used in humans:  
        • Leading scientists in the field have for long been calling for a “global pause” on clinical applications of the technology in human beings, until internationally accepted protocols are developed.
        • Studies highlighted that these cells might trigger cancer.
      • It may increase the risk of mutations elsewhere in the genome in those cells.
      • Total clarity on its cause, effect and usage is still not clear.
      • Ethical concerns: 
        • In addition, there are concerns with manipulating human embryos for their own interest. 
    • pgSIT:
      • The system is self-limiting and is not predicted to persist or spread in the environment, two safety features that should enable acceptance for this technology.

    Conclusion

    • This study suggests pgSIT may be an efficient technology for mosquito population control and the first example of one suited for real-world release. 
    • In the future, pgSIT may provide an efficient, safe, scalable, and environmentally friendly alternative next-generation technology for wild population control of disease-spreading mosquitoes resulting in wide-scale prevention of human disease transmission.

    Source: IE