Genome Editing with CRISPR-Cas9
-- posted January 2016 --
CRISPR (Clustered Regularly-Interspaced Short Palindromic Repeats) is a gene-editing method for accurate modification of targeted single or multiple genes in the genome of any organism. The latest progress in the CRISPR method has frequently been listed as one of the top scientific advancements in 2015, and also has been called by MIT Technology Review ‘the biggest biotech discovery of the century.’
The following 4:13 minutes video provides an excellent brief overview of the main principle of work of CRISPR.
https://www.youtube.com/watch?v=2pp17E4E-O8
The method is based on the use of a protein called Cas9, and was initially found in bacteria. They have been using it for millennia for modifying their own DNA as a protective means against viruses. Cas9 acts as a pair of molecular scissors that are employed to cut out the virus DNA sequence, which is afterwards replaced with a harmless sequence of DNA. The process of matching Cas9 with the target gene sequence is carried out with the help of guide RNA.
Later research showed that the same technique can be applied to cut out any particular piece of DNA in the genome of any species, and consequently to turn genes on or off – a process known as genome engineering. Pairing Cas9 with guide RNA that carries a DNA sequence matching the region in the DNA at the location of the targeted gene, allows the editing complex to latch accurately with the target gene, where Cas9 would cut the DNA sequence and disable the gene permanently. The complementary sequence of DNA carrying the desired gene would then replace the original gene in the genome.
The advantage of CRISPR over other similar gene-editing methods, such as restriction enzymes, is its precision. Considering that the previous methods could not achieve good control in cutting DNA, disabling specific genes before CRISPR was a challenging task. In addition, CRISPR can be used for editing multiple genes in a single procedure, and therefore it is suitable for treating complex diseases affected by a multitude of genes.
Our understanding of the function of approximately 20,000 genes in the human genome is still rudimentary, thus by disabling certain genes researchers can study their function and get a better understanding of their influence. Vice versa, dormant genes in the genome can be activated in order to impart new functions to the cells.
Areas of application that can potentially benefit from CRISPR are: treating diseases (such as diabetes or cancer) using a precise gene-therapy treatment, designing more efficient drugs, developing food crops with enhanced infections resistance, designing biomaterials with new functions and properties, etc.
