by Niamh Butler-Carroll
CRISPR has created a lot of conversation in the scientific community and the general public alike over recent years, especially following the birth of two genetically edited babies in November 2018. For those that don’t know, CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) technology is a simple yet powerful gene-editing tool that was first observed and described in bacteria. These organisms use CRISPR-derived RNA and Cas-9 proteins to create a “library” of any invading organisms’ DNA, which they can then use to destroy the DNA of future invaders, allowing bacteria to build a defense against those invaders. Despite having been discovered in 1987, it would take a few decades before scientists began to study this mechanism with the goal of reworking it to allow for genomic editing.
Today, the use of CRISPR is spreading quickly in the field of synthetic biology, having been adapted into new technologies such as CRISPRi and CRISPRa. The “i” refers to interference, with this version made to specifically silence certain genes, whereas CRISPRa allows for the activation of genes, hence the “a”. By designing a small stretch of base pairs that match the gene that has been chosen and ensuring this sequence is only present in the targeted gene and nowhere else in the genome, a new “guide RNA” is created that is complementary to this sequence. This molecule, combined with Cas-9 (CRISPR-associated protein 9) and the guide RNA will go in, find the sequence, and act like scissors to cut out the targeted DNA sequence. Once cut, the target cells would innate their repair system to fix the cut, or the researchers will fill in the gap with their own DNA sequence - a disease-negative genomic sequence, for example.
This technology has turned what used to be a very time-consuming and expensive task into something relatively cheaper, quicker, and more versatile than anything else geneticists had available - with applications ranging from editing out genes in fruit flies to study how Hox genes work, removing and replacing once incurable genetic diseases out of humans, and changing plant genomes in order to study how polyploidy affects plant reproduction. With endless possibilities, any genetic disease could effectively be treated in any organism across the globe. Scientists are already begun working on wiping out mosquitoes that carry malaria, and creating hardier, more nutritious crops for nations around the world. Indeed, with such a powerful tool at our disposal, researchers are even beginning to question the ethics of whether or not we should be editing the genes of the people around us. Talk of the ethics of gene editing have spiked thanks to the news that two HIV-negative “CRISPR babies” were born to HIV positive biological parents in China last winter.
However, CRISPR isn’t anywhere near to a perfect gene editor. Recent studies have found CRISPR editing can sometimes trigger cancers, and if researchers aren’t careful, CRISPR could target other sequences of DNA that they don’t intend for it to target - if they match the specific sequence. Even still, sometimes CRISPR simply fails to work on the site it is intended to work at, cutting out strips of DNA that it was never intended to touch, or adding new genes in the wrong places. It is very difficult to optimize a technology so new, and a lot of research must go into the way CRISPR works before we can truly tout it to be the godly gene editing tool we all want it to be. Especially following the birth of He Jiankui’s CRISPR babies, it is clear that there needs to be careful rules and regulations about what can and cannot be attempted with this powerful, yet understudied new tool.
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