Multi-armed CRISPR
It became possible to edit several fragments of the genome at once
The new CHyMErA tool, created by researchers from the University of Toronto, allows you to edit several fragments of the genome at once. The authors described their development in the journal Nature Biotechnology (Gonatopoulos-Pournatzis et al., Genetic interaction mapping and exon-resolution functional genomics with a hybrid Cas9–Cas12a platform).
The CRISPR/Cas DNA editing method has revolutionized the study of the genome, making it possible to accurately remove any human gene and find out its function. Although such a tool did not always "hit" exactly on target, it was very useful for genetic research and allowed many discoveries to be made in this area. However, using CRISPR, it is still impossible to edit several sections of the genome at the same time. Meanwhile, such a feature would shed light on the joint action of several sequences and their regulation in the event of a pathological condition.
Now researchers from the University of Toronto have managed to create such a tool. It was named CHyMErA (Cas Hybrid for Multiplexed Editing and Screening Applications). Its work is similar to CRISPR, but the new tool uses two enzymes for editing at once – Cas9 and Cas12a. Cas12a is an enzyme that can be used to produce several guide RNA molecules in the same cell. It is this property that allows you to edit several DNA fragments at once.
Before creating a new tool, the authors tried for several years to create systems for editing several DNA fragments based on either Cas9 or Cas12a. But all attempts did not bring results. Then the scientists decided to combine these two enzymes. Having tested the new technology, the authors saw that it is really capable of removing two segments of genes.
At the next stage of the work, the scientists resorted to the help of colleagues to apply CHyMErA for the systematic analysis of the interaction of genes in a healthy state and in various pathologies. The researchers were able to modify the system for such purposes. In one application of the new tool, the researchers targeted it at pairs of genes known as paralogs that have a similar sequence but remain poorly understood.
Since paralogs arose as a result of gene duplication, it was assumed that they would play similar roles. But their function cannot be disclosed by existing single-gene targeting methods, mainly because one paralog would compensate for what was missing. Using this tool for about 700 pairs of paralogs – almost all that exist in the human genome – scientists have confirmed that many of these pairs of genes do indeed perform similar roles in cell survival, while others have different functions. In the future, the authors plan to use CHyMErA to solve other important genetic problems and find answers to questions that have not been studied until now.
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