Genetic study investigates how mosquitoes transmit malaria

By determining the genetic sequence of 16 types of mosquitoes (Anopheles genus), an international research team, including researchers from SFU, has contributed knowledge on how these mosquitoes adapt to humans as the primary host of malaria.

The international research team consisted of over 100 biologists, immunologists, infectious disease specialists, computational mathematicians, and geneticists, and had its findings published in Science Express.

While the presence of malaria in North America and Europe is minimal, it is endemic in several areas around the equator and has high fatality rates in sub-Saharan Africa and Southeast Asia. However, only a few dozen of the almost 500 different Anopheles species of mosquito can carry the disease.

By investigating the differences between these mosquito types and their harmless cousins, the team hoped to pinpoint what leads to the difference in transmission.

The project of sequencing genomes and transcriptomes of the Anopheles species began in September of 2008 and was funded by the National Genome Research Institute and the National Institute of Allergy and Infectious Disease of the US National Institutes of Health. Cedric Chauve, SFU professor of mathematics, and Ashok Rajaraman, SFU graduate student in mathematics, joined the project in 2012.

“The main aspect of the research by our team, whose specialty is evolutionary genomics and not health genomics, was to understand the evolution of a group of 11 Anopheles genomes, whose common ancestor lived roughly 100 million years ago,” explained Chauve. “It will be up to our biologist colleagues now to integrate our findings on genome evolution in research on disease transmission.”

“This might help to explain why Anopheles mosquitoes are so adaptable.”

Cedric Chauve,
SFU professor of mathematics

Chauve and Rajaraman used computational methods to reconstruct ancestral mosquito genomes and analyze their chromosomal evolution over the past 100 million years. Their goal is to discover potential adaptation mechanisms that may be related to malaria transmission by understanding how the chromosomes of Anopheles have evolved.

Since only the Anopheles genus can transmit human malaria, the international research team is trying to understand what makes Anopheles unique.

“[What] seems to be specific to Anopheles genomes is a very high rate of chromosome rearrangement in the sex chromosome X that might be involved in speciation (i.e. the mechanisms by which new Anopheles species appear), and thus might help to explain why Anopheles mosquitoes are so adaptable compared to other insects,” explained Chauve.

Although his and Rajarman’s research uncovers new opportunities to understand genomic and genetic factors related to malaria transmission, their work is still in a preliminary stage.

“Now that we have been involved with these data, our next goal is to refine the preliminary analysis and to understand in much greater details the evolution of Anopheles genomes, which includes reconstructing very detailed genome maps for extinct ancestral Anopheles species,” said Chauve. “The Science paper was just a first analysis and there is much to do to refine it.”