UCR researchers find genetic tool to disrupt mosquito adaptation

A UCR postdoctoral fellow in entomology, Colince Kamdem, has discovered a weakness in the genes that give mosquitos their uncanny ability to adapt to the insecticides humans use to ward them off.

Mosquitos, according to Kamdem, are highly polymorphic. Polymorphism is the presence of natural variation in a population and is driven by changes occurring in DNA sequences. “A population that can mutate easily and that contains a large number of individuals has the potential to be highly polymorphic,” says Kamdem. “Mosquitoes are often large populations with a short generation time and fall clearly in this category.”

Kamdem and his colleagues at UCR analyzed the chromosomes in the Anopheles funestus mosquito, one of the most crucial vectors in spreading malaria in sub-Saharan Africa, in order to understand its abilities to quickly adapt to new environmental situations.

What Kamdem and his team discovered was that one of five chromosome arms held the secret to these mosquitoes’ ability to outlast humanity’s attempts to eradicate them. These arms are basically a unit to represent a chromosome. These arms have a low level of genetic diversity, making them ideal for gene drive systems, which, according to Kamdem, are the insertion and propagation of a foreign gene, or genes, into a given population.

These findings are substantial considering that new gene tracks can react negatively to gene drives. The solution to this would be to target genes that are “well conserved and that are located in regions of the genome (chromosomes) that do not mutate easily.” Anopheles funestus chromosomes are stable and have low levels of genetic diversity. However, even with chromosomes with low levels of genetic diversity, Kamdem says more research is needed to “fully explore the potential” of Anopheles funestus as a candidate for gene drive systems.

Though Kamdem acknowledges there is limited ability to control mosquitos, “If the technical challenges are overcome and all the associated environmental and ethical issues addressed, gene drive systems and other population replacement/suppression approaches can provide excellent opportunities to control mosquito-borne diseases.”

Kamdem is a native of the central African country of Cameroon where malaria is endemic with a prevalence rate at 29 percent of the population. When asked how his experience growing up in Cameroon factored into his research, Kamdem replied, “I think it’s a great chance and a great opportunity for me to conduct such research. Mosquitoes that carry important human pathogens are colonizing new geographic regions, and we urgently need effective solutions to slow their proliferation.”

Research on mosquitoes in Kamdem’s lab is advancing, exploring ways to understand the uncanny adaptive potential of mosquitoes. The research has also yielded the identification of genes that are implicated in the spread of insecticide-resistant mosquitoes that followed the uptick in mosquito prevention in sub-Saharan Africa. Kamdem is optimistic about the technological advancements “enabling in the detailed studies of the genetic basis of adaptation in living organisms; so our expectations are very high.”

A project is also underway to use insecticide resistance against the mosquito population since resistant mosquitoes have lower longevity and a lesser capacity to transmit diseases, with Kamdem highlighting that “we are interested in designing insecticide applications that will further weaken the mosquito and ultimately interrupt the transmission cycle.”

According to the World Health Organization, malaria, which is caused by parasites transmitted by mosquito bites, had infected 212 million people worldwide in 2015 and resulted in 429,000 deaths. Those primarily affected by malaria are pregnant women, the young and people travelling from non-malaria infected countries. The disease has hit areas such as Southeast Asia, Central and South America, the Caribbean, the Middle East and Oceania (encompassing Australia and the South Pacific islands).

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