The long-hypothesized male determining gene in the mosquito species that carries malaria has been discovered. It has laid the groundwork for the development of strategies that could help control the disease.
In many species, including mosquitoes, Y chromosomes control essential male functions, including sex determination and fertility. However, knowledge of Y chromosome genetic sequences is limited to a few organisms.
‘The most efficient means for genetic modification of mosquitoes is engineering a driving Y chromosome which controls essential male functions, including sex determination and fertility.’
This is significant because male mosquitoes offer the potential to develop novel vector control strategies to combat diseases, such as malaria and the zika and dengue viruses, because males do not feed on blood or transmit diseases.
One vector control method under development involves genetic modification of the mosquito to bias the population sex ratio toward males, which do not bite, with the goal of reducing or eliminating the population. This and other control methods have received a lot of attention recently because of the spread of zika virus.
Modeling has shown that the most efficient means for genetic modification of mosquitoes is engineering a driving Y chromosome. A molecular-level understanding of the Y-chromosome of the malaria mosquito, as described in the just-published paper, is important to inform and optimize such a strategy.
While the genome of Anopheles gambiae
was sequenced 13 years ago, the Y chromosome portion of it was never successfully assembled.
The researchers who published the paper in the Proceedings of the National Academies of Sciences
used multiple genome sequencing techniques, including single-molecule sequencing and Illumina-based sex-specific transcriptional profiling, as well as whole-genome sequencing, to identify an extensive dataset of Y chromosome sequences and explore their organization and evolution in Anopheles gambiae
complex, a group of at least seven morphologically indistinguishable species of mosquitoes in the genus Anopheles
which contain some of the most important vectors of human malaria.
They found only one gene, known as YG2, which is exclusive to the Y chromosome across the species complex, and thus is a possible male-determining gene.