Scientists have discovered which gene determines whether or not a certain species of mosquito is male. Significantly, this is one of the species that transmits malaria, a life-threatening disease that 3.2 billion people – around half the world’s population – are at risk from contracting.
By carefully sequencing the genetic transcripts, or “genetic messages”, produced in the male and female embryos of the Anopheles gambiae mosquito, the team of researchers were able to identify a gene exclusive to the male embryos. This gene, which the team from The Pirbright Institute and the Liverpool School of Tropical Medicine have dubbed “Yob”, turned out to be the master regulator of the sex determination process in this particular species.
The gene is only the second-known identification of such a determination mechanism in insects. In these African mosquitos, it’s encoded onto the male Y chromosome, and it initially appeared to have no presence or application in their female counterparts. However, when the researchers injected Yob into mixed-sex early embryos of the mosquito – before the sex of each of them had been determined – they found that it killed all the females before they had a chance to hatch.
Remarkably, this form of genetic femicide didn’t just apply to A. gambiae embryos – it also seemed to work on A. arabiensis too, another African mosquito species that also transmit malaria. If the Yob gene is silenced, however, it proves to be lethal to males.
“Our research may have far-reaching implications for the control of malaria,” Dr Jaroslaw Krzywinski, head of the Vector Molecular Biology group at The Pirbright Institute, and coordinating research of the study, said in a statement. “This preventable disease is the major cause of human suffering and an immense barrier to socioeconomic development, mainly in poor countries of sub-Saharan Africa.”
Anopheles mosquito larvae. The newly discovered gene determines whether they are male or female. DeAgostini/Getty Images
Malaria is spread by the bites of infected female Anopheles mosquitoes in around 95 countries, and in 2015 alone, 438,000 deaths were reported out of 214 million cases. As the World Health Organization notes, there are more than 400 species of Anopheles mosquito, with around 30 of them transmitters or “vectors” of major importance.
Vector control – eliminating these mosquito populations, or killing off the females – is the primary method of population control, and this Science study has stumbled across a new way to enact this. If a way can be found to insert Yob into the nests of these mosquitos, the disease-spreading females will die out, and eventually, so will the males.
The African Anopheles mosquitos have long lifespans, and they actually prefer biting humans over other animals for the most part. This explains why nearly 90 percent of the world’s malaria cases are in Africa. Work is currently underway to eliminate them, but not all conventional methods are as effective as they once were.
“Currently, application of insecticides to control mosquitoes remains the most efficient way of combating the disease,” Krzywinski adds, “but with a rampant spread of resistance to chemicals in mosquito populations, the insecticides may soon become ineffective.”
These mosquito nets save hundreds of thousands of lives, but not everyone has access to them. Teekevphotography/Shutterstock
Mosquito nets and anti-malarial drugs are still proving to be reliable preventative measures, but scientists generally agree that the best way to prevent malaria is to attack the root cause of it in the first place. Genetic modification is currently being trialed in some areas, and in one instance, a mosquito was given a genetic trait that prevented the malaria parasite from developing within the insect, meaning it could not pass it onto humans.
Is Yob the future of gene-based malarial prevention? Watch this space.