FEATURE ARTICLE
Genetic Strategies for Controlling Mosquito-Borne Diseases
Engineered genes that block the transmission of malaria and dengue can hitch a ride on selfish DNA and spread into wild populations
Fred Gould, Krisztian Magori, Yunxin Huang
Wolbachia
All these types of selfish DNA involve genes on chromosomes in the nuclei of each cell in a genetically altered pest. An alternative approach uses a selfish genetic element carried in the cytoplasm of the cell. The tool that allows this unorthodox inheritance is a kind of intracellular bacteria called Wolbachia, which is passed through the female line only (similar to mitochondria) and can manipulate the reproductive success of its insect hosts. One type of Wolbachia causes cytoplasmic incompatibility, in which the progeny of Wolbachia-infected males and uninfected females are nonviable. However, infected males breed normally with infected females. This situation provides a reproductive advantage to infected females, which can mate successfully with either infected or uninfected males. And because infected females pass on the Wolbachia infection to male and female offspring (regardless of the infection status of their mate), the frequency of Wolbachia in the population increases over time.
A group led by Stephen L. Dobson at the University of Kentucky transferred this type of Wolbachia into Aedes aegypti mosquitoes and found that the parasite spread from 20 percent to 100 percent of a laboratory population within eight generations. A strain of Wolbachia carrying an anti-pathogen gene is tantalizing to consider. But as with the other approaches, several challenges must be met before this system could be deployed. Most fundamentally, molecular biologists need to learn how to genetically manipulate Wolbachia, a process that is more difficult because the bacteria live within the cells of another organism.
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