Scientists have introduced into the genome of mosquitoes, one male gene and genetic females grown males for all phenotypic traits. However, transgender mosquitoes are unable to fly and mate, because they have no other male gene. But genetic males with extra male gene in autosome and the successfully bred, and their offspring, the majority of females become males. The authors of an article published in the journal Proceedings of the National Academy of Sciences, believe that with the help of transgenic males can reduce the proportion of biting females in the population and slow the spread of mosquito-borne diseases.
Mosquitoes acquire the male sex if in the course of their development included male factor in a special locus. A number of types of such factors are found (for example, the vectors of dengue fever Aedes aegypti is a factor Nix) — these primary signals through a cascade of events trigger the expression of conservative transcription factors that regulate the sexual differentiation.
Scientists from the Polytechnic University of Virginia tried to manipulate male factor Aedes aegypti — they turned off the gene Nix in male embryos, and resulted in adults began to develop in the ovaries. After the reverse procedure, making plasmid with Nix in female embryos, there were mosquitoes with male genitals. However, in both cases, the change was not all phenotypic manifestations of sex. This may be due to somatic mosaicism (different genotypes of germ and somatic cells), using the “wrong” promoter or participation in sex determination of other genes of the same locus.
The same group of scientists headed by Jessani Tu (Zhijian Tu) that changed the gender of mosquitoes the last time, took up this task again. Biologists have created two transgenic lines aegypti mosquito (Aedes aegypti) in which the expression of Nix obeyed the same promoter as in insect wild type.
Nix is integrated into the chromosomes of mosquitoes was expressed in them the same way as the endogenous factor, and completely changed the phenotype of the genetic females on the male. Insects, which replaced the floor, was larger than genetic males, but could not fly. Because mosquitoes mate in flight, transgenic males could not impregnate the active females. Then the scientists placed the insect in anesthetized females they can mate and the result is viable offspring, half — female wild-type, half — transgenic males. Hence, researchers actually managed to have a sex change and mosquitoes to grow in fertile males.
Scientists have suggested that the inability of transgenic mosquitoes to fly is associated with the gene myo-sex, which is in the same “male” locus, and Nix. In mosquitoes, wild-type CRISPR/Cas9 deleted myo-sex — indeed, some of these insects are unable to fly. Flying mosquitoes were mated, and their offspring also showed a non-flying insects — they all had mutations in the myo-sex. The authors concluded that this gene is required for the flight of the males.
Finally, the researchers tested how flying transgenic males (carrying the male endogenous locus, and inserted artificially Nix) successfully mate with females. For this purpose, the cells were placed for 20 transgenic males and wild type males and ten females. As a result, the offspring half of the females appeared transgenic individuals, and therefore insects can effectively extend gene “gender change”, at least in laboratory conditions.
In the future, transgenic males can be used to reduce the number of females in the population because they drink blood and transmit various diseases. However, first we need to conduct additional research and create a complete (ie flying) mosquitoes transgender — for this you need to implement in their genotype at the same time Nix and myo-sex.
And while scientists using more primitive instruments to reduce the number of mosquitoes — release nature of the sterile males that compete with childbearing for females. Recently even tested a drone throwing a sterile mosquitoes and evenly distributes them over a large area.