Yellow Fever, Dengue Fever Responsible Mosquito Genome Sequence Punlished
The fight against yellow fever and dengue fever was advanced by an international team of researchers led by J. Craig Venter Institute that sequenced the Aedes aegypti genome, the mosquito that carries these deadly diseases.
This research is the first characterization of the approximately 1.38 billion base pairs of DNA of the Ae. aegypti genome. From this sequence, the team showed that this mosquito species has an estimated 15, 419 protein encoding genes.
Since both the sequence of the fruit fly, Drosophila melanogaster (sequenced in 1999 and published in 2000) and another mosquito species, Anopheles gambiae, (sequenced and published in 2002) were available, researchers were able to compare these insects to Ae. aegypti to ascertain biological differences between the species.
An. gambiae diverged on the evolutionary tree from the fruit fly about 250 million years ago, and the two mosquito species diverged from one another approximately 150 million years ago. Genomic comparisons revealed greater differences between the fruit fly and the mosquito species, than between the two mosquito species.
An important finding from this analysis is the discovery of certain proteins and genes unique to the Ae. aegypti. These proteins and genes, among many things, infer robustness to the insect. A more thorough analysis of these genes and proteins may lead to improved means to eradicate the mosquito and thereby stop the spread of yellow and dengue fevers.
Another key discovery was that almost 50 percent of the genome consisted of transposable elements. These are movable pieces of DNA that cause mutations and can affect genome size. The researchers showed that likely due to these elements the gene length and the intergenic regions of Ae. aegypti are 4-6 times larger than those of An. gambiae and the fruit fly.
"With more than half a million cases of dengue fever which is endemic in at least 100 countries and more than 30,000 deaths from yellow fever each year, clearly understanding the biology of the vector for these two worldwide killers is essential to eradicating these diseases," said Dr. Nene, principal investigator. "By having the genomic code of this species of mosquito we now have a key tool that will aid in the study of aspects of biology specific to Aedes aegypti. This will to help identify pathways which permit these mosquitoes to transmit viruses. Interfering with the function of critical mosquito molecules could lead to effective control of this prolific pest and the devastating diseases associated with it."
The scientists concluded that this draft genome will enable continued and more refined genomic maps of this disease vector. And, with other ongoing genome sequencing and analysis projects of related mosquito species, the spectrum of knowledge about these disease carriers grows, as does the potential to eliminate the associated diseases that kill millions each year.
This work was mainly funded by contracts from the United States National Institutes of Health's National Institute of Allergy and Infectious Diseases (NIAID). This research was first undertaken at The Institute for Genomic Research (TIGR), a legacy organization of the J. Craig Venter Institute, and in collaboration with The Broad Institute and VectorBase, a NIAID bioinformatics resource center. TIGR became part of the JCVI in October 2006.