Regular readers may remember a post back in March of this year where I wrote about a genetically modified mosquito. The aim of the GM mosquito was to decrease populations of the species Aedes aegypti, an all but domesticated variety of mosquito perfectly adapted to live in human-inhabited areas and carrier of several significant human pathogens including dengue fever, yellow fever and zika virus. The FDA had approved a small, two day field trial release of the mosquito to study its impact on the local environment.
The trial must have gone well as, last week, the FDA gave its full approval to the GM organism being deployed on a large scale in the Florida everglades. This doesn’t mean, however, that the critters will be out any time soon. There are still state level requirements that need to be fulfilled, but with the first cases of locally transmitted zika virus being reported recently local officials won’t want to be seen to be dragging their feet.
The mosquitos have had a completely artificial construct called tetracycline repressible Trans-Activating factor Variant (tTAV) inserted into them 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.
In the wild, non-biting males only will be released. These will breed with females resulting in offspring that are not viable without the tetracycline supplement. The idea is to release enough of the GM males to out compete the wildtype ones in a given area resulting in a collapse in the mosquito population.
There is no great concern about what a lack of A. aegypti will do to the local ecosystem as it is an invasive species and is only there because of accidental human transport. The only significant sticking point may be that of a large anti-GMO backlash. Even though several other genetically modified insects have been released in the US with almost zero notice from the public, for some reason the anti-GMO crowd have got themselves organised against this particular example.
Thousands of negative comments have been received during a public consultation on the project with all manner of weird and wonderful and totally irrelevant points made. For example, some raised concerns that, if swallowed by a human, the GM mosquito could provoke an allergic reaction. Why having slightly more DNA inside them would cause allergies in humans I couldn’t begin to guess.
The state has decided to add a non-binding referendum question alongside the Presidential election in November. I have no idea how the local populous feels towards the project but hopefully a strong positive showing will free up officials to push forward with a full scale release that could literally save lives. Oxitec, the UK based company that developed the organism over more than a decade will no doubt want the last remaining hurdles removed as soon as possible. I wish them luck.