Genetically Modifying an Entire Ecosystem 52
New submitter structural_biologist writes: Genes normally have a 50-50 chance of being passed from parent to offspring, but scientists may have figured out a way to create genes that show up in offspring with a much higher frequency. "One type of gene drive influences inheritance by copying itself onto chromosomes that previously lacked it. When an organism inherits such a gene drive from only one parent, it makes a cut in the chromosome from the other parent, forcing the cell to copy the inheritance-biasing gene drive—and any adjacent genes—when it repairs the damage." When introduced into the wild, organisms containing gene drives would breed with the population, quickly spreading the modified genes throughout the ecosystem. While the technology could help prevent the spread of malaria and manage invasive species, many scientists worry about the wide-ranging effects of such a technology and are calling for its regulation.
Summary is terrible (Score:5, Informative)
Summary is an excerpt of an article highlighting some potential use of technology developed by George Church's lab at Harvard (and others). It is actually some pretty incredible stuff. Church's first published the adaption of the CRISPR system to gene editing in eukaryotes a few years ago. Basically, it works like this. CRISPR is a bacterial defense system where an enzyme (endonuclease) is directed to cut a specific DNA sequence by it's directly adjacent targeting sequence. Bacteria use this to protect themselves from viruses. When a virus tries to insert itself into the genome of a bacterium, CRISPR will cleave that sequence (if the bacterium has the appropriate targeting system) and subsequent DNA repair processes will occur that will excise the viral sequence. You can think of it as a pseudo-immunity system for bacteria against viruses. Like other DNA sequences, CRISPR sequences can be transferred between bacteria in a population allowing for broad-ranging resistance to viral infection to occur within a bacterial community.
The innovation by Church's group is to put the CRISPR system in eukaryotes. Introducing modified genes by homologous recombination has been around for a long time, but the problem with most eukaryotes is they have multiple copies of each chromosome. So a modification in one copy will get diluted out over several rounds of replication. By including the CRISPR system in the mutation that targets the original gene, a mechanism is supplied to allow a modified gene to quickly spread throughout the population. This makes genetic modification of eukaryotes much more efficient and easier to control.
Now, while safely applies in a laboratory system, the ecological consequences of using such a system in a natural setting are unclear. This is the purpose of the article: to raise some of the issues and possibilities to begin a discussion about how such a system might be used safely and what sort of regulations may need to be put into place. The article does quite a good job of illustrating some scenarios. Here is what I consider the meat of it, but of course other scenarios exist as well.
Why and how might we use gene drives to intervene in a particular ecosystem? Our earlier example is perhaps the most compelling: we might use gene drives to control malaria by altering Anopheles mosquitoes that transmit the disease. Anti-malarial medicines and insecticides are losing effectiveness due to evolving resistance, while a vaccine remains out of reach despite intense research and investment. Gene drives, in contrast, might spread genes conferring malaria resistance through the mosquito populations with few if any effects on other species. Alternatively, they might be able to reduce or even eliminate the mosquitoes for long enough to permanently eradicate the malaria parasite. Similar strategies could work for other organisms that spread disease.
Just want to put that out there so that a somewhat productive conversation can hopefully happen here.