The field of molecular genetics is constantly evolving with each new discovery. Most are baby steps towards a critical breakthrough but every once in a great while a monumental discovery is made that is a game changer. Recently that game changer is CRISPR or clustered regularly interspaced short palindromic repeats. CRISPRs are short repetitive segments of DNA that are part of the immune system of certain bacteria. CRISPR works with Cas proteins (CRISPR associated protein) as a system to identify viral DNA and remove it. Viral DNA sequences of a virus that had previously invaded that particular bacteria are incorporated between CRISPR sequences as a type of molecular mug shot to help ID a “recurrent offender”. From those viral sequences RNA is made that helps the Cas protein identify the viral gene sequence and destroy it (should it try to invade again). Think of it as a spam filter used to weed out questionable emails from your inbox.
So what? Why is this important? Up until recently characterizing a gene, i.e. determining its functional role in an organism, required a great deal of money and time. I will not go into the details of what was involved but will instead direct you to the “For More Information” section below. As researchers played around with the CRISPR system they realized they could replace the viral sequence with a DNA sequence of interest and precisely remove that sequence from a cell. When I say a cell I mean any kind of cell and the technology involved is less than a nice dinner out. The possibilities are endless for what CRISPR can do-disease treatment, agricultural improvements, invasive species eradication, the list goes on. That is why CRISPR is considered the best thing since sliced bread or in molecular speak the best thing since PCR (https://en.wikipedia.org/wiki/Polymerase_chain_reaction).
So basically I am talking about gene editing or genetic engineering. You may have heard of researchers wanting to create a woolly mammoth from elephant eggs or the Chinese researchers that tried (unsuccessfully) to genetically edit inviable human embryos for beta thalassemia, a genetic disorder that impedes the development of red blood cells. That is all based on the use of CRISPR. Google CRISPR and you will be amazed by the variety of research that is currently underway.
One of the common examples of how CRISPR technology can be used is genetically editing mosquitos to essentially wipe them out. Basically, researchers would incorporate a CRISPR system into mosquitos that removes a gene required for their survival but does not get in the way of reproduction-let’s call it gene x. Those genetically engineered mosquitos that lack gene x (gene x mosquitos) would be released so they could mate in the wild. When gene x mosquitos mate with wild mosquitos the CRISPR system would remove gene x from wild mosquito chromosomes thus leading to progeny with no gene x. With the right gene, say one that creates only male progeny, you could potentially wipe out that particular species of mosquito. This is a form of gene drive (https://en.wikipedia.org/wiki/Gene_drive). Similar work has been going on for some time now but with CRISPR the pace and efficiency of research increased at lightening speed.
So that would be great, right? No mosquitos! Except, when you eliminate a species there is a cascade effect. Think of the poor beleaguered bats and all the other critters that call mosquitos dinner. Or the other possible outcomes if we were to intentionally eradicate a species. Yes, we unintentionally cause the demise of many species but once we get rid of mosquitos where would it end? Who decides? As our ability to genetically manipulate organisms (including ourselves) improves we need to consider the ethical uses of that technology. In the future we may be able to eradicate some terrible genetic diseases such as sickle-cell anemia or invasive pests such the Emerald Ash Borer. Without discussions and regulations (all of that is happening on some level right now) things could become rather surreal. Hello saber tooth tiger…
About the Illustration
Watercolor and pencil, nothing fancy. This image is available via Redbubble.
For More Information
http://www.nature.com/news/crispr-the-disruptor-1.17673 http://blogs.scientificamerican.com/guest-blog/gene-drives-and-crispr-could-revolutionize-ecosystem-management/ http://www.wired.com/2015/07/crispr-dna-editing-2/