Resistance complicates use of gene drive to control dangerous pests

The use of gene drive technology to control wild populations of insect pests could be foiled by development of genetic resistance, according to a study in Science Advances published Friday.

Genetic variability and the tendency of many insects to inbreed could encourage resistance, the study found. This would be worsened if the genetically engineered trait caused a decrease in fitness.

Meanwhile, a gene drive approach developed by UC San Diego and UC Irvine scientists that might circumvent resistance has received a $2 million shot in the arm from the Bill & Melinda Gates Foundation.

The Science Advances study was conducted in flour beetles. It can be found at Michael J. Wade was the senior author. Douglas W. Drury was first author. Both are of Indiana University.

The British biotech Oxitec has developed genetically engineered male mosquitoes that pass along a trait that causes all their offspring to die.

Oxitec’s mosquitoes have been tested in field trials Panama and Brazil. A trial in Florida is planned to fight the Zika virus. Meanwhile, another trial has been launched using male mosquitoes infected with a sterility-causing bacterium.

However, Oxitec’s approach requires continued releases of new genetically modified mosquitoes. Gene drive could in theory introduce a trait that stays lodged in the population, or at least doesn’t have to be replenished as often.

The gene drive variant would self-propagate, performing a copy-and paste into any unmodified genes present in embryos. So one gene variant inherited from one parent could spread the change to the corresponding gene from the other parent.

UC San Diego researchers Ethan Bier and Valentino Gantz were the first to demonstrate gene drives in insects, using CRISPR/Cas9 technology. They did this first in fruit flies, and then, in a study led by Gantz and UC Irvine’s Anthony James, in mosquitoes.

Their approach is make mosquitoes resistant to malaria parasites. So while the mosquitoes would still bite, they wouldn’t transmit malaria.The researchers have said they expect this approach would minimize resistance.

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