Another week another interesting genetics story. This Friday the US Food and Drug Administration (FDA) released a preliminary report for public comment on whether or not genetically modified mosquitos should be released into the wilds of Florida. Significantly, their preliminary conclusion is that the field trial would not pose a significant environmental or health risk.
The plan is to conduct a small trial by releasing male mosquitos of the Aedes aegypti species. The mosquitos have been genetically modified so that they contain two extra genes than normal. One of these is the gene DsRed2 which is a reporter gene. A reporter gene is one that we use to tell if our desired trait has been successfully inserted into the organism or not. In this case, DsRed2 makes a fluorescent red protein which would make the larvae of the GM mosquitos glow in the dark thereby making them easier to spot and filter out from the non-GM individuals.
The second gene is a completely artificial construct called tetracycline repressible Trans-Activating factor Variant (tTAV) which, I must say, is really quite elegant. The gene that is, not the name. The name sucks. When the mosquitos are grown in the lab the antibiotic tetracycline is added to the water they live in. In the presence of tetracycline the tTAV protein binds to the antibiotic and nothing really happens. In the absence of tetracycline the tTAV protein binds to its own promoter, tetO, which upregulates expression of the gene in an exponential feedback loop. This is bad news for the cell in which this is happening as tTAV also binds to the machinery of transcription when tetracycline isn’t around, as is the case in the wild. Eventually so much of the transcriptional apparatus has been taken up that the rest of the genes in the genome can no longer be expressed. The cell, and ultimately the organism, dies as a result.
This self-limiting gene construct has been designed by UK company Oxitec who are marketing their GM mosquitos as a way of bringing mosquito borne diseases under control. The males would be released into the wild where they would be free to mate with females. The offspring would inherit the tTAV gene and be killed within a few days of birth at the late larval or early pupal stage.
The potential benefits are enormous; not only could it lower the prevalence and range of mosquito borne diseases such as malaria and dengue fever but it would also bring a huge reduction in the quantity of pesticides that would otherwise have been sprayed to keep the population in check.
The artificial gene poses no threat to either humans or other animals but, I suspect, to try to head off criticism before it starts, they are only using males as these do not bite and so will not come into contact with other species. Also, as all offspring are killed, the gene does not persist in the environment.
The FDA, having assessed the ecological niche in which A. aegypti sits, has decided to give the go ahead for a 2 day field trial as any impact on the local environment is deemed negligible. After a 30 day consultation they will make a final decision for the trial to begin or not. I’m hoping they proceed. Whilst I know I have readers who take issue with our ability to ‘play God’ and mess with other species I, for one, am very much in favour.
It really is imperative that the world gets onboard with the genetic modification of our food, pests such the mosquito and any other use we can see to put it to. We’re simply not going to be able to feed ourselves and stay healthy without it. We have the technology to solve a problem, I fear that a century from now our grandchildren will look back at us aghast that for so long we had the option to save millions of people from starving to death, or going blind, or catching preventable diseases and but we let them catch that disease, we let them go blind and we let them starve to death rather than give an inch on our ideological hang ups. Enough is enough.