04/10/10

Three major mosquito genomes now cracked

Culex quinquefasciatus mosquitoes transmit roundworms that cause lymphatic filariasis Copyright: Courtesy of Jim Gathany/CDC

By: Christine Ottery

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<h1>Three major mosquito genomes now cracked</h1>
<h4>By: Christine Ottery</h4>
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Scientists have now sequenced the genomes of species from all three major groups of mosquitoes and hope that comparing them will lead to common strategies to cut diseases transmitted by the insects.
The final genome to be cracked, Culex quinquefasciatus, was published in Science last week (1 October). This species transmits roundworms that cause lymphatic filariasis in tropical and subtropical regions, as well as West Nile virus and St Louis encephalitis in North America. 
The sequence can now be compared with malaria vector Anopheles gambiae, whose genome was sequenced in 2002, and Aedes aegypti, which spreads dengue fever, yellow fever and chikungunya and <a href="http://www.scidev.net/en/news/scientists-crack-mosquito-code.html">was sequenced in 2007</a>.
"Now we can start to triangulate this data," Peter Arensburger, lead author of the Culex study and an assistant researcher at the University of California, Riverside, told SciDev.Net. "We can see what genes these major disease-carrying groups have in common and how they are different."
The Culex group of mosquitoes is the most geographically widespread of the three groups, with more than 1,200 species. 
One difference is that Culex‘s genome has almost 19,000 genes, one fifth more than A. aegypti and half as many again as A. gambiae, some of which may help the mosquito to feed on a variety of animals, transmit a range of infections and spread widely. 
"We also speculate that because Culex has this larger number of genes it is better able to come up with ways to circumvent the pesticides that we throw at it [by developing pesticide resistance]," Arensburger told SciDev.Net.
"I think the most immediate applications are in the development of more effective pesticides and <a href="http://www.scidev.net/en/features/will-gm-mosquitoes-end-dengue-and-malaria--1.html">genetically transforming the mosquitoes so they are unable to carry diseases,</a>" he said, adding that "eventually, this might inform vaccine development as well".
"The sequencing of Culex provides the infrastructure for a lot of future work," said Luke Alphey, research director of biotech company Oxitec, a spin-off from the University of Oxford, which is researching genetic modification methods to engineer disease-resistant mosquitoes. 
"If we understand how the pathogens, viruses or even protozoan parasites develop in the mosquito then we may be able to come up with new strategies to stop their transmission," said Marcelo Jacobs-Lorena, a molecular microbiologist at John Hopkins University, United States. 
However, it could be 20 years before new solutions are fully tested and implemented, he added. "In the ten-year term we could come up with concrete ideas, but implementation in the long term could take another ten years or so." 
<a href="http://www.sciencemag.org/cgi/content/full/330/6000/86?ijkey=t9pggXefvhRHM&keytype=ref&siteid=sci" target="_blank" rel="noopener noreferrer">Link to full study in Science</a>

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Scientists have now sequenced the genomes of species from all three major groups of mosquitoes and hope that comparing them will lead to common strategies to cut diseases transmitted by the insects.

The final genome to be cracked, Culex quinquefasciatus, was published in Science last week (1 October). This species transmits roundworms that cause lymphatic filariasis in tropical and subtropical regions, as well as West Nile virus and St Louis encephalitis in North America.

The sequence can now be compared with malaria vector Anopheles gambiae, whose genome was sequenced in 2002, and Aedes aegypti, which spreads dengue fever, yellow fever and chikungunya and was sequenced in 2007.

"Now we can start to triangulate this data," Peter Arensburger, lead author of the Culex study and an assistant researcher at the University of California, Riverside, told SciDev.Net. "We can see what genes these major disease-carrying groups have in common and how they are different."

The Culex group of mosquitoes is the most geographically widespread of the three groups, with more than 1,200 species.

One difference is that Culex‘s genome has almost 19,000 genes, one fifth more than A. aegypti and half as many again as A. gambiae, some of which may help the mosquito to feed on a variety of animals, transmit a range of infections and spread widely.

"We also speculate that because Culex has this larger number of genes it is better able to come up with ways to circumvent the pesticides that we throw at it [by developing pesticide resistance]," Arensburger told SciDev.Net.

"I think the most immediate applications are in the development of more effective pesticides and genetically transforming the mosquitoes so they are unable to carry diseases," he said, adding that "eventually, this might inform vaccine development as well".

"The sequencing of Culex provides the infrastructure for a lot of future work," said Luke Alphey, research director of biotech company Oxitec, a spin-off from the University of Oxford, which is researching genetic modification methods to engineer disease-resistant mosquitoes.

"If we understand how the pathogens, viruses or even protozoan parasites develop in the mosquito then we may be able to come up with new strategies to stop their transmission," said Marcelo Jacobs-Lorena, a molecular microbiologist at John Hopkins University, United States.

However, it could be 20 years before new solutions are fully tested and implemented, he added. "In the ten-year term we could come up with concrete ideas, but implementation in the long term could take another ten years or so."

Link to full study in Science