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저자： 업로드：2017-06-02 조회수：
If gene-editing technology is used to suppress insect populations, it may give rise to resistance, mainly through naturally occurring genetic variation and inbreeding among targeted insects. These findings, from a study conducted at Indiana University, suggest that artificially induced genetic modifications are unlikely to spread between regions or species. Such genetic modifications, however, could have more staying power if they occur in portions of the genome where mutations are less likely to occur.
At Indiana University, a team of scientists led by biology professor Michael J. Wade, Ph.D., evaluated the degree to which synthetic gene drives based on CRISPR/Cas9 technology have the potential to control, alter, or suppress populations of crop pests and disease vectors. Gene drives refer to genes that spread at a rate of nearly 90%—significantly higher than the normal 50% chance of inheritance that occurs in sexually reproducing organisms. With natural gene drives, studies have suggested that any gene that can suppress the spread of gene-favoring infertility tends to be favored by natural selection.
Whether such an effect could limit the effectiveness of artificial gene drives, such as those based on CRISPR/Cas9 and other site-specific nuclease technologies, was the question addressed the Indiana University researchers.
"We found that small genetic variation within species—as well as many insects' tendency to inbreed—can seriously impact the effectiveness of attempts to reduce their numbers using CRISPR technology," said Dr. Wade. "Although rare, these naturally occurring genetic variants resistant to CRISPR are enough to halt attempts at population control using genetic technology, quickly returning wild populations to their earlier, 'pre-CRISPR' numbers."
Additional details from the study appeared May 19 in the journal Science Advances, in an article entitled “CRISPR/Cas9 Gene Drives in Genetically Variable and Nonrandomly Mating Wild Populations.” This article describes how the scientists used genetic data from four populations of the flour beetle Tribolium castaneum to show that most populations harbor genetic variants in Cas9 target sites, some of which would render them immune to drive (ITD). (This species of flour beetle is estimated to destroy 20% of the world's grain after harvest.)
“We show that even a rare ITD allele can reduce or eliminate the efficacy of a CRISPR/Cas9-based synthetic gene drive,” wrote the article’s authors. “This effect is equivalent to and accentuated by mild inbreeding, which is a characteristic of many disease-vectoring arthropods.”
