Gene Drives Offer New Hope Against Diseases and Crop Pests
Biologists in the United States and Europe are developing a revolutionary genetic technique that promises to provide an unprecedented degree of control over insect-borne diseases and crop pests.
The technique involves a mechanism called a gene drive system, which propels a gene of choice throughout a population. No gene drives have yet been tested in the wild, but in laboratory organisms like the fruit fly, they have converted almost the entire population to carry the favored version of a gene.
Gene drives “could potentially prevent the spread of disease, support agriculture by reversing pesticide and herbicide resistance in insects and weeds, and control damaging invasive species,” a group of Harvard biologists wrote last year in the journal eLIFE.
A gene drive designed to render a population extinct is known as a crash drive. A crash drive being developed for mosquitoes consists of a gene engineered into the Y chromosome that shreds the X chromosome in the cells that make the mosquito’s sperm, thus ensuring that all progeny are male. Unless the drive itself is damaged through mutation, the number of females would be expected to dwindle each generation until the population collapses.
Biologists led by Andrea Crisanti and Tony Nolan at Imperial College London reported this month in the journal Nature Biotechnology their development of mosquitoes with gene drives that disrupt three genes for female fertility, each of which acts at a different stage of egg formation. Because the female mosquitoes are infertile only when a copy is inherited from both parents, the gene drives would be thoroughly disseminated through a population before taking their toll. They could “suppress mosquito populations to levels that do not support malaria transmission,” the authors wrote.
The mosquitoes are not yet ready for release. Because natural selection will heavily favor any wild mosquitoes that acquire resistance to the gene drives, the researchers need to prevent such resistance from arising. One approach would be to target two or three sites in the same fertility gene, giving natural selection a much higher barrier to overcome.
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