Researchers master gene editing technique in mosquito that transmits deadly diseases

Traditionally, to understand how a gene functions, a scientist would breed an organism that lacks that gene -- "knocking it out" -- then ask how the organism has changed. Are its senses affected? Its behavior? Can it even survive? Thanks to the recent advance of gene editing technology, this gold standard genetic experiment has become much more accessible in a wide variety of organisms. Now, researchers at Rockefeller University have harnessed a technique known as CRISPR-Cas9 editing in an important and understudied species: the mosquito, Aedes aegypti, which infects hundreds of millions of people annually with the deadly diseases chikungunya, yellow fever, and dengue fever.

 

Image : Mosquito larvae from two different lines fluoresce in different colors thanks to genetic tags that were inserted using the CRISPR-Cas9 gene editing system.

Researchers led by postdoctoral fellow Benjamin J. Matthews adapted the CRISPR-Cas9 system to Ae. aegypti and were able to efficiently generate targeted mutations and insertions in a number of genes. The immediate goal of this project, says Matthews, is to learn more about how different genes help the species operate so efficiently as a disease vector, and create new ways to control it. "To understand how the female mosquito actually transmits disease," says Matthews, "you have to learn how she finds humans to bite, and how she chooses a source of water to lay her eggs. Once you have that information, techniques for intervention will come."

Malaria: A vector infecting both apes and humans

In 2010, a study revealed that the main agent of malaria in humans, called Plasmodium falciparum, arose from the gorilla. Today, the vector which transmitted the parasite from apes to humans has just been identified. A Franco-Gabonese research consortium has determined which species of anopheles mosquitoes transfer the disease to apes. Among them is Anopheles moucheti, known for biting humans. Therefore, it appears to be the species which originally infected us through our cousins. And it could do it again today.
The same vector.
IRD and CNRS researchers, in addition to their Gabonese partners based in the CIRMF in Franceville, wanted to determine the identity of the mosquitoes which transmit malaria to apes. To this end, they caught a thousand mosquitoes of the Anopheles genus, in close proximity to groups of wild or semi-wild primates. They then conducted analyses on the insects collected, belonging to fifteen different species, in order to detect which ones were infected by the Plasmodium malaria parasites. Two species of mosquitoes were thus revealed to be contaminated by these pathogenic agents. Anopheles moucheti was one of them -- a major vector for humans in Central Africa. This species is therefore both primatophilic and anthropophilic. Since gorillas are the origin of the disease in humans, this species would have enabled the transmission of the infection from apes to humans thousands of years ago.

Discovery of what attracts pregnant mosquitoes is used to fight malaria

The battle against malaria is also a battle against its natural host, the mosquito, which means disrupting the insect's lifecycle is every bit as important as putting nets over beds. Now, an international research team has discovered what attracts mosquitoes to lay their eggs in specific places.

 

 

 

 

Some of the traps being tested with a substance that attracts female mosquitos looking for nesting spots to lay their eggs.

Credit: OviART

 

 

"We have been able to show that it is no coincidence where mosquitoes lay their eggs," says Jenny Lindh, a researcher from KTH Royal Institute of Technology. "They use both vision and their sense of smell."

With this finding, the research group OviART is designing mosquito traps that could help cut down the population of the genus, Anopheles, which is the primary vector of malaria.

Experimenting with different soil and water mixtures, the research team concluded that a constituent of earth found in breeding sites near Kenya's Lake Victoria -- a substance called cedrol -- is particularly attractive to the malarial mosquito, precisely at the time when the female is ready to ovulate.