Gene Elements Might Help Spread Malaria-Resistant Mosquitoes, Study Finds

Genes that cause the death of offspring that do not inherit them could contribute to the spread of genetically modified, malaria-resistant mosquitoes, according to a study published online on Thursday in Science, the Times reports (Henderson, Times, 3/30). A study published last week in the Proceedings of the National Academy of Sciences found that a new breed of genetically modified, malaria-resistant mosquitoes might be able to breed and spread in the wild, leading to fewer mosquitoes carrying malaria parasites. The study also found that the modified mosquitoes might survive better than unmodified mosquitoes in the wild (GlobalHealthReporting.org, 3/20). That strategy requires malaria-resistant mosquitoes to replace natural mosquitoes, and the Science study indicates that the process might be helped if malaria-resistance genes are linked to a class of synthetic genes, known as Medea elements, that kill offspring that do not inherit them (Times, 3/30). The synthetic gene elements, which were created by researcher Chun-Hong Chen of the California Institute of Technology and colleagues, are believed to select for their own survival, The Scientist reports. The Medea element in the mother causes toxins to be released into all of her oocytes, and only the offspring that inherit the Medea element can produce an antidote (Lee Phillips, The Scientist, 3/29). According to the study, a Medea gene spread rapidly when it was introduced into a colony of fruit flies. Chen and colleagues suggest that a similar strategy could be used to help genetically modified, malaria-resistant mosquitoes replace natural mosquitoes. If the Medea gene could be linked with the malaria-resistance gene, any eggs laid by modified mosquitoes that did not inherit malaria-resistance genes would not hatch, according to the study (Times, 3/30). The strategy "looks very convincing," Marcelo Jacobs-Lorena of the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study, said, adding that if the method works in fruit flies, the "chances that it would work in insects of medical importance is quite high." One potential barrier to the strategy is that mosquito populations can be reproductively isolated from one another, according to Frederic Tripet of the United Kingdom's Keel University, who also was not involved in the study. "It is likely that the more we study those populations, the more reproductive barriers we will find that can locally prevent or slow down the spread of introduced transgenes," Tripet said (The Scientist, 3/29).

The study is available online.