[blogs.scientificamerican.com]

"“Gene Drives” and CRISPR Could Revolutionize Ecosystem Management

Genome engineering technologies have revolutionized genetics, biotechnology, and medical research. We may soon be able to alter not just domesticated species, but entire wild populations and ecosystems. Why, when and how might we use these novel methods to reshape our environment?

The story begins with a new technology that has made the precise editing of genes in many different organisms much easier than ever before. The so-called “CRISPR” system naturally protects bacteria from viruses by storing fragments of viral DNA sequence and cutting any sequences that exactly match the fragment. By changing the fragments and delivering the altered system into other organisms, we can cut any given gene. If we also supply a DNA sequence that the cell can use to repair the damage, it will incorporate this new DNA, precisely editing the genome. When performed in the cells that give rise to eggs or sperm, these changes will be inherited by future generations. Because most altered traits don’t improve and may even decrease the organism’s ability to survive and reproduce, they generally can’t spread through wild populations.

Now imagine we want to edit a particular gene—say, one controlling the immune response of mosquitoes to malaria. We could make a mosquito with an edited version of this gene and insert the CRISPR system right next to it along with a fragment directing CRISPR to cut the original—but not the edited—gene. When our altered mosquito mates with a wild mosquito, the offspring will inherit one edited and one normal copy. CRISPR will then cut the normal copy and the cell will attempt to repair the cut by copying the edited version and the CRISPR system. The offspring will now have two copies of the edited version plus CRISPR.

This insect will mate with other insects in which the same process of turning the normal genes into edited genes will be repeated. Given enough generations, CRISPR will spread the edited gene through the entire population of mosquitoes—and this is key—even if the edited gene reduces the odds that each mosquito will reproduce.

The ability to manage ecosystems by altering wild populations will have profound implications for our relationship to nature. Selective breeding and genome engineering have in many ways defined agriculture, human living and medicine, but have had comparatively little impact on most ecosystems due to the inability of domesticated crops and animals to survive in the wild.

Kevin Esvelt is a Technology Development Fellow at the Wyss Institute for Biologically Inspired Engineering at Harvard University and lead author of the eLife and Science papers on RNA-guided gene drives."