In December 2014, MIT Technology Review hailed CRISPR/Cas9 as the biggest biotech discovery of the century. CRISPR – which stands for Clustered Regularly Interspaced Short Palindromic Repeats – is a natural process used by bacteria to fend off viruses. The technology is now being applied to life sciences research all over the world.
CRISPR is a gene editing toolbox that can be used for many different purposes. It’s a relatively new technology, validated in 2013 when scientists demonstrated for the first time that CRISPR molecules, once delivered into cells, can be engineered to precisely snip a particular piece of DNA and replace it with another one. Since then, CRISPR genome engineering technology has revolutionised genetics and molecular biology research.
How is CRISPR being used?
One way to use CRISPR is to delete a single gene to prove or disprove its link to a disease. For example, our colleagues at the Walter and Eliza Hall Institute (WEHI) were able to kill human Burkitt lymphoma cells in pre-clinical models by precisely deleting MCL-1, a gene that has been shown to keep cancer cells alive.
CRISPR can also be used to artificially generate precise pre-clinical models that mimic the development of diseases such as cancer. At WEHI, we have successfully adapted CRISPR technology for the generation of pre-clinical models. While conventional methods of generating a pre-clinical model can take up to 15 months, CRISPR technology more than halves the time to 6 months. The advantages of CRISPR over any other genome modifying procedures are its ease of use, precision and speed with which specific alterations can be made in a cell or even a whole organism.
Recently, the technology has also been employed for whole genome screening to identify new gene products involved in normal cellular pathways such as cell death, differentiation or proliferation. The screening procedures have led to the identification of new tumour suppressor genes and drug resistance genes that will assist the development of new medicines for cancer.
The application of CRISPR to whole genome screening has been a huge success, as the validity of newly identified gene targets can be more than 50%, which is much higher compared to any other screening technologies ever used. Overall, CRISPR technology has made whole genome screening easy and reliable.
CRISPR at WEHI
In cancer research, a key objective of whole genome screening is to identify new tumour suppressive genes that contribute to cancer growth. However, from a therapeutic or drug development point of view, it will be more beneficial to identify gene products that kill cancer cells when their functions are inhibited.
With funding from the Australian Cancer Research Foundation, the ACRF Breakthrough Technologies Laboratory was established in 2015 to do exactly that: identify genes that form cancer’s Achilles Heel.
The ACRF Breakthrough Technologies Laboratory houses sophisticated equipment that enable researchers to conduct a new form of CRISPR screening called the ‘arrayed screen’.
‘Arrayed screens’ differ from the alternative ‘pooled screens’ in one major aspect: different CRISPR molecules are delivered to the cells of interest individually in multiwell plates (see Figure below). Each well contains cells with one known genetic modification and therefore researchers are better able to detect positive ‘hits’. In ‘pooled screens’ various selection techniques to isolate cells of interest are needed. . While more superior and convenient, ‘arrayed screens’ are more labour intensive thus requiring the use of automation to handle the large number of plates.
Since the opening of the ACRF Breakthrough Technologies Laboratory in September 2015, researchers from our institute have been fervently laying the groundwork to conduct CRIPSR screenings for various diseases from diabetes to cancers.
In just a little over three years since the 2013 breakthrough discovery, we are already seeing the direct benefits of CRISPR such as identifying new targets for cancer therapy. We believe that it would not be long before we see widespread adoption of cancer therapies developed through the CRISPR technology.
Process workflow of an arrayed genome-wide CRISPR screening.
Figure credit – Dr Hélène Jousset Sabroux, Head of Screening Laboratory, Walter and Eliza Hall Institute.