Andreas Späth

Genetically engineered mossies

2014-07-07 12:35

Andreas Wilson Späth

When it comes to genetically modified organisms (GMOs), most of us think of plants, like herbicide resistant mielies and soy, but the world’s gene splicing and dicing scientists are a busy lot who have long started to experiment with modifying the genetic material of animal species as well.

It shouldn’t come as too much of a surprise then that some of their creations are already buzzing about in the wild.

At the beginning of June, a group of researchers published a paper describing a new genetically modified Anopheles gambiae mosquito which they believe may become instrumental in fighting malaria in humans, the disease of which this species is the main carrier.

Their technique involves injecting male mosquito embryos with a “homing” gene extracted from slime mould (a group of spore-producing organisms previously classified as fungi). Once the mossies have grown to adulthood and start producing sperm cells, this gene attaches itself to a bit of DNA in the X chromosome and “shreds” it.

As a result, almost none of the sperm of these modified male mosquitoes carries the X chromosome required to produce females and more than 95% of their offspring are male.

The idea is that male mosquitoes genetically manipulated in this way and released into the wild would act as a form of rapidly spreading genetic population control resulting in precipitous collapses in mosquito populations due to an increasing scarcity of females.

The researchers found that their altered males readily mated with wild females in cages, passing on their X chromosome-damaging gene to the next generation. In these controlled experiments, entire populations tended to be wiped out within six generations as fewer and fewer females were available for reproduction.

While the authors of the paper believe that it is highly unlikely that wild mosquitoes could ever develop resistance to the introduced genetic material, their modified minions have yet to prove themselves under natural conditions and it is unclear how well they would fare in the mating game when competing with wild male mosquitoes.

Developments are much further advanced in another mosquito species – Aedes aegypti – the main culprit in spreading dengue fever. Genetically modified variants of this creature pass an introduced “suicide gene” on to their offspring, killing them before they reach maturity.

In 2009 and 2010 a British biotech company called Oxitec released 3.3 million of these mossies in the Cayman Islands and reported a mosquito mortality rate of over 80%.

In 2010 and 2011, release experiments were conducted in Malaysia, Brazil started ongoing trials in 2011 and Panama announced plans for a release this year.

So, like their counterparts in the plant world, genetically modified insects are truly among us. The latest development is the first genetically modified honeybee which it is hoped will aid scientists in studying honeybee genetics and behavior.

The fact that critics of GMOs have called for caution seems to have had little effect on the development and deployment of transgenic insects. Of course eradicating the impact of malaria and dengue fever, which kill hundreds of thousands of people, especially children, every year, is a high priority, but is driving entire animal species to extinction via genetic manipulation really the answer to the problem?

The ultimate consequences of releasing genetically modified insects into the wild are unknown and unpredictable. If something were to go seriously wrong, how would we put that genetic genie back into its bottle? And who would be responsible for the fallout?

- Andreas is a freelance writer with a PhD in geochemistry. Follow him on Twitter: @Andreas_Spath
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