CRISPR: using, not abusing

dna_methylationWhat if your child suffers from an untreatable and fatal genetic disease that could be reversed by a novel “search-cut-copy-pasting” gene-editing technology? Welcome CRISPR, the “crispy” name given to a bacterial mechanism to fight invading viruses, which has been adapted in a revolutionising gene-editing technology, once again sparking ongoing discussions about the ethics of tinkering with the code of life itself. The debates reached a new high earlier this year when researchers from Sun Yat-sen University in China used  CRISPR to edit the genes of unviable human embryos; although, the latter had lost the ability to develop into human beings, the study highlighted the potential of this powerful technology to generate permanent genetic changes that could ultimately affect the course of evolution if applied to viable offspring. Yet, the predicted benefits of CRISPR are hard to ignore.

Recently, CRISPR’s co-inventor, Jennifer Doudna, wrote in a Nature Comment: “Who besides the scientists using the technique would be able to lead an open conversation about its repercussions?” So here is my contribution to the conversation, highlighting what the fuss is all about and how to use, but not abuse, this incredible technology. Praised as the scientific “Breakthrough of the Year” and a “game-changer” in molecular biology, CRISPR to me compares to the industrial revolution, the latter comprising the modernisation of basic tools and the introduction of modern manufacturing. Molecular components capable of snapping the DNA open have been available since the 70’s, and refined tools to engineer precise genetic changes were introduced once at the beginning of the century and again ten years later. Nonetheless, the toolbox was too complex, to rigid and available to few expert laboratories. Think of the first computers in history and their modern-day counterparts. CRISPR belongs to the latter, and here comes why.

Search-cut-copy-and-paste

That’s all there is to CRISPR. Exactly, it is dead-easy to do! As a result, the technique has been adopted by thousands of laboratories worldwide soon after its use as a gene editing tool was described back in 2012. Our genes are coded by the letters A, G, C, T – and there are 6 billion (!) letters in every single diploid human cell (i.e. a cell with a set of DNA from your dad and another set from your mum). Even a single typo in the sequence, when part of an essential gene, may prove to be fatal. Such point mutations underlie monogenic diseases like cystic fibrosis and the severe overgrowth disorders that my PhD project focusses on. CRISPR consists of two basic components that enable precise cutting of the DNA at the site of a mutation and correction of the latter.  The so-called guide RNA is like “velcro” – it is designed to match the region of the DNA that you want to correct. It searches the DNA and guides the second component, a molecular scissor named Cas9, to the matching region. In the split of a second, Cas9 cuts the DNA open at the exact position specified by the guide, and if a copy of the correct DNA code has been provided, the cell can now amend the break by pasting the correct sequence, potentially getting rid of a devastating disease. Other uses of this technology involve the introduction of mutations to create herbicide-resistant plants, malaria-resistant mosquitoes, pigs that can grow human organs for transplant, and hypoallergenic peanuts, to name just a few. In short, a versatile molecular version of a Swiss army knife has been developed.

Fear and regulations

With third-graders using CRISPR to manipulate the DNA of yeast for less than $100, it is no surprise that concerns have been raised over the potential (ab)use of CRISPR by the wrong hands, including those of terrorists. Perhaps the technique should be banned, the reagents destroyed and forgotten?! Unlikely to be effective. After all, gene editing has been possible years before CRISPR, and a ban of the latter is unlikely to be the solution. Similarly, few people would agree to banning the manufacturing of weapons altogether to prevent them from being used by terrorist groups. Having said that, the CRISPR “craze” has urged (and rightly so!) world leaders in biology, genetics, ethics and policymaking to debate future regulations aimed at stipulating how research and applications of genome engineering might be pursued responsibly. Partly because the technique is not fail-proof and fears of such “off-target” effects – the introduction of unwanted mutations – continue to haunt the scientists using it. Consequently, in their most recent three-day meeting, leaders in this field concluded that gene editing should not be applied in the clinic to alter viable human embryos until “(i) the relevant safety and efficacy issues have been resolved … and (ii) there is broad societal consensus about the appropriateness of the proposed application.”

CRISPR and me

As alluded to above, the power of CRISPR makes it possible to correct or replicate the genetic defect causing a particular human disorder. That’s exactly what I have been up to in the past two months. I feel lucky that the discovery of CRISPR (for gene editing) was made only 3 years ago, in time for my PhD. Previously, my supervisor’s team has been limited to studying cells isolated from the skin of our patients, and these cells constitute a very poor  disease model, hampering our attempts at understanding the molecular mechanisms underlying PROS (“PIK3CA-related overgrowth spectrum”; for more on my PhD project, click here). Thanks to CRISPR and stem cell technology, this is now history. I can introduce the specific mutation that I want to scrutinise in stem cells in less than a month, and use these stem cells to generate the exact cell type that is most relevant to the disease I want to study. The insight gleaned from such studies may ultimately drive the development of new therapies for a disease that is currently untreatable. Not to mention, the importance of a better understanding of the protein encoded by PIK3CA, p110a, which plays a key role in cancer and a cell’s response to insulin.

The above is my personal example of how to use – and not abuse – CRISPR. Clearly, the latter will have major effects on society as a whole, and it is imperative that its implications are communicated to ordinary people before they are offered gene-edited pets or the life-saving reversal of a fatal mutation.

Here are some links if you want to know more:

A video by MIT researchers, explaining the CRISPR method for gene-editing

A New Yorker article on CRISPR, which I personally find very interesting and accessible: “The Gene Hackers”

CRISPR in agriculture

A summary of the recent gene-editing summit in Washington

An ethical perspective: “Editing life: Scientists can, but should they?”

Jennifer Doudna on embryo editing

 

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