When the sterile males try to mate with females, they would produce no progeny, and the population would dwindle. To control insect populations, one could deploy the progeny into the environment to hatch. We want to kill the females because they bite and transmit disease. CRISPR then targets those genes, and all of the females die and all of the males are sterilized. When we cross lines with cas9 and these different guide RNAs together, all of the progeny receive the cas9 gene and the guide RNAs through Mendelian segregation. We design the guide RNAs to target genes important for female development and male fertility. We make different insect lines homozygous for cas9 and a guide RNA. By using CRISPR, we are not affecting the chromosomes, so the animal is more fit, which results in longer viability in the wild and a higher rate of population suppression. This could be one way of combating mosquitoes that does not rely on insecticides. We developed a precision-guided sterile insect technique (pgSIT), which also uses CRISPR. ![]() The sterile insect technique is the most effective way of controlling insects in the wild, but it traditionally uses radiation for sterilization, which reduces insects’ fitness due to chromosomal damage. What do you see as the most promising technology for insect control? This is complete postzygotic isolation, which is the definition of speciation. ![]() When we cross these mosquitos with wild type insects that have the targets present, CRISPRa becomes active and causes lethality. We used a creative genetic crossing scheme where we could maintain the engineered mosquito line in the laboratory by keeping CRISPRa inactive. To rescue this overexpression, we mutated the promoters to prevent CRISPRa machinery from binding. It cannot cut DNA, but it progressively binds to targets using guide RNA, which recruits transcriptional machinery to the target promoter region and promotes gene expression. CRISPRa uses a version of Cas9 that is inactive (dCas9). We first did this as a proof of concept in flies, and we showed that this works in mosquitoes. Ideally, we want to multiplex the CRISPR machinery to target all mosquito-transmitted viruses that affect humans.Īdditionally, we used CRISPRa to overexpress insect developmental genes, which results in complete lethality. When the mosquito gets infected with a virus, the CRISPR machinery cuts the viral RNA sequences, resulting in collateral activity that reduces the mosquito’s fitness and ultimately kills the mosquito. We encoded the machinery in the mosquito so that they expressed CRISPR ribonucleases and designed guides that target different viruses. ![]() ![]() There are CRISPR ribonucleases that can degrade RNA instead of DNA, and we engineered these to target viruses. We recently developed a new technology that uses CRISPR to block viral transmission. What CRISPR-based strategies for insect control have you developed? We have devised many strategies for using CRISPR to control insect populations in a way that is safe enough to enable public acceptance and regulatory authorization in the near term. When I targeted a gene for eye pigmentation or body pigmentation, close to 100 percent of the progeny had some type of mutation in those genes, and I could see the result. One of the first experiments I did with it was to genetically encode its components in flies and cross those flies together. It works really efficiently we can program it and it is easy to use. What makes CRISPR a useful tool for your research?ĬRISPR is incredibly robust in terms of cutting DNA and targeting nucleic acids.
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