Born, Bred, Dead.


Chikungunya mosquito

Does the new CRISPR/Cas9 gene modifying technology hold the secret to wiping out mosquitos and the deadly diseases they transmit? Seán Kilgarrif investigates.

What if I told you there was new technology that could completely wipe out mosquitoes? What if I told you mosquitoes are also pollinators and some believe that their extinction could have extreme consequences on our ecosystem? This is the moral dilemma playing on the minds of many scientists in this field.

CRISPR technology presents us with the opportunity to modify genomes with exceptional efficiency and precision with a wide range of applications. CRISPR stands for “clustered regularly interspaced short palindromic repeats.” If you’re like me and are still a little puzzled, what that means is that the name CRISPR arises from one repeated sequence of DNA with unique sequences in between the repeated sequence.

This seemed intriguing to scientists and, sure enough, they discovered that the unique sequences were actually the DNA of viruses that target bacteria. The viruses were present in the DNA so that the viruses could be effectively fought if the body encountered them again. On top of that Cas (CRISPR-associated proteins), an enzyme located near the CRISPR, can snip DNA and slice the harmful viruses. This double level defense mechanism is extremely useful when it comes to combatting viruses.

The CRISPR/Cas9 technology was discovered as early as the 1980s but it’s only in recent years that steps have been made to unlock its true potential. Previously it could take up to a year and several generations of mice to create a genetically altered mouse. With this new technology that time can be reduced to only a few months and far fewer mice are required.

Another bonus is that multiple genes can be altered simultaneously — a real game changer. The Cas9 gene makes this whole idea even more powerful. They essentially let us exploit evolution to insert a desired gene into an organism. The special thing about a gene drive is that it always ends up in the offspring, even if only one parent has it. Eventually more and more generations will possess this gene drive and the induced gene will be present in the entire population.

This technology can be used to modify the genomes of any organism. The possibilities this creates are endless. Endangered species may be saved, genes could be modified to stall the spread of weeds, and harmful species such as mosquitoes could be genetically modified to eventually die off. This would leave the world free of the fear and suffering which malaria and so many other mosquito transmitted diseases cause.

With the outbreak of the Zika Virus during the Rio 2016 Olympic Games and its spread throughout the US, the virus has gained increased media attention.  Since 2015, sixty-two countries and territories reported mosquito transmitted Zika virus.  Zika in pregnant women can lead to microcephaly, unusually small heads in babies, among other abnormalities.

In 2010, malaria killed 554,000 people.  In 2015 there were 214 million malaria cases resulting in 438,000 deaths.  This decrease is positive but the number is still far too high. The World Health Organisation recommends “personal protection with repellents, clothing that covers exposed skin and use of nets when resting during the day”. When there is a more proficient solution it seems a shame not to use it when it could save so many lives each year.

However, opinion is divided as to whether wiping out an entire spieces is wise. What would happen to the plants they pollinate and the predators that prey on them? Lives may be saved but would the world around us be left to perish? Is it right for scientists to decide if a species lives or dies?

We must contemplate these questions as we approach this important crossroads in our future. As George Church, a professor at Harvard University says “if we’re going to talk about it at all in advance, rather than in the past tense, now is the time.”

Kevin Esvelt, a postdoc from Harvard University, and his colleagues are proposing a number of safeguards, including reversal drives that can undo earlier engineered genes. “We need to really make sure those work if we’re proposing to build a drive that is intended to modify a wild population,” Esvelt says.

However Church is optimistic about the potential for Cas9-based gene drives. “I think we need to be cautious with all new technologies, especially all new technologies that are messing with nature in some way or another. But there’s also a risk of doing nothing.”


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