Reversing Insecticide Resistance Using CRISPR

 

Researchers have tested using CRISPR to reduce insecticide resistance in pests. In simple form, this was done by editing the gene which controls insecticide resistance by returning it to a wild type allele, making it susceptible to insecticides. This obviously came with ethical concern so the researchers only made it a temporary solution. Hence, why they returned the gene to wildtype rather than removing the insecticide-resistant variant genes entirely by replacing them with susceptibility to pesticide genes. They term for this is a e-Drive cassette which spreads through CRISPR gene editing which binds to Cas9 DNA and cuts out voltage gated sodium ion channel (vgsc) insecticide resistant gene site. This solution is not permanent since removing insecticide resistance lowers fitness of pests.

What the e-Drive essentially does is disable the insecticide resistance gene by using CRISPR to ensure that the wild-type gene has a 100% frequency of being passed to offspring. Since the non-resistance gene is being spread rapidly, it can spread faster than the resistance gene within just a few generations, 8 to 10 to be specific. Although the cassette was also inserted with a fitness check which limits viability or fertility. So the wild type gene spreads, increasing susceptibility and reducing pests (for example on crops), then over time the added fitness check along with the natural lower fitness takes over and the non-resistant pests eventually die out. The population returns to a normal resistant one. The beauty of this e-Drive cassette is that it can be reintroduced whenever needed, for example, if the pest problems become large again, then the e-Drive can easily be added back. It is a short term, effective, easily implemented, and easily removed strategy that the researchers hope could also work on mosquitos for malaria.

This is a great development because insecticide-resistance is rapidly spreading throughout populations of pests. While we need to control pests from destroying things like crops, it is becoming increasingly difficult to use pesticides to kill them. We also do not want the e-Drive to become out of control which could seriously harm pest populations. As the researcher says, this strategy will work without creating any other perturbation to the environment. If we can successfully increase pesticide effectiveness without entirely harming a pest population, I am all for it.

Links

https://www.sciencedaily.com/releases/2024/11/241122172740.htm

https://www.epa.gov/pesticide-registration/slowing-and-combating-pest-resistance-pesticides

A Mutation in Anopheles funestus Leads to Pyrethroid Resistance

An article published by The Scientist shares a recent discovery about the spread of resistance in African mosquitos. Mosquitos have developed a number of genetic tricks to bypass the effects of pyrethroids. One mutation found in mosquitos prevents insecticides from binding to their target. Over the years, scientists have struggled to determine precisely which markers give mosquitos metabolic resistance. Researchers have recently discovered a single mutation linked to pyrethroid detoxification in populations of southern Africa’s Anopheles funestus. The allele in Anopheles funestusinvolves genes encoding cytochrome P450. Scientists used RNA sequences to capture the genes’ expression. This gene expression was then compared to several mosquito populations in different areas of Africa. Through this research, scientists were able to identify a section of DNA that has accumulated mutations and a large insertion of genetic material. PCR then was used to pinpoint the resistant allele. This discovery is a breakthrough in understanding insecticide resistance in mosquitos. While this mutation is not present in all mosquito species, this method could be used to identify other resistance mutations. 

 Anopheles funestus Mosquito

The transmission of malaria in Africa is a public health issue. Pyrethroids are a large component of malaria prevention. Through the use of pyrethroids, 663 million cases of malaria have been prevented from 2000 to 2015. 

I found this article to be quite interesting. Mosquitos cause a lot of trouble in Africa with the spread of malaria, so it is important researchers learn more about insecticides and insecticide resistance. I find it intriguing that several mutations have led to this resistance and that the resistant allele has quickly become prevalent in the Anopheles funestus population in southern Africa. Ideally researchers will use this information to create different insecticides prevent the Anopheles funestus population from growing out of control.