Scientists have shown that a controversial gene-editing tool can completely eliminate populations of mosquitoes in the laboratory.
Andrea Crisanti, from the Imperial College London, and colleagues used CRISPR to engineer a mosquito gene known as doublesex, which determines whether a mosquito develops into a male or a female.
For their study published in the Nature Biotechnology, the researchers used Anopheles gambiae, the species of mosquito that spreads malaria. The mosquito-borne disease remains as one of the deadliest diseases in the world, killing more than 400,000 per year.
Male Anopheles gambiae mosquitoes that carry the mutation can mate with normal female mosquitoes and pass along the modified gene. Male and female mosquitoes that carry one copy of the mutation behave normally and healthy, and this allows them to continue spreading the mutation.
The resulting female mosquitoes that are born with two copies of the mutation, however, have the characteristics of both the female and male mosquitoes so they do not bite and lay eggs.
The researchers then released the CRISPR-modified mosquitoes into cages filled with unmodified mosquitoes. Within seven to 11 generations, the caged populations collapsed.
Earlier studies that used a similar approach encountered problems because the mosquitoes developed resistance to the genetic modification. The researchers said that the mosquitoes in the new study did not appear to mutate in a way that can reduce the effectiveness of the engineered mutation.
The study was conducted in the hope that genetically modified mosquitoes can be used as a weapon against malaria.
“We know what the costs of malaria are — and they are horrific,” Kevin Esvelt, an evolutionary engineer at the Massachusetts Institute of Technology, who is not involved in the study, told NPR. “This could save a lot of lives.”
The researchers nonetheless said that the implications may go beyond malaria and mosquitoes.
“The role of doublesex in sex determination in all insect species so far analyzed, and the high degree of doublesex sequence conservation among members of the same species (in gene regions involved in sex-specific splicing), suggests that these sequences might be an Achilles heel present in many insect pests that could be targeted with gene editing approaches,” the researchers wrote in their study.
The researchers said that they now want to test the technique on a larger population of mosquitoes that are confined in more realistic settings, where ecological factors such as competition for food may have an effect on the outcome.