Scientists at the CSIR-Institute of Genomics and Integrative Biology in New Delhi have developed a genome editing system that is better and more precise than current CRISPR technology.
The Basics of CRISPR
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is originally a natural defense mechanism in bacteria that destroys viral DNA. Researchers repurposed the system by altering genes in more complex organisms.
The CRISPR-Cas9 system
The CRISPR-Cas9 technology allows scientists to add, delete or change DNA sequences. It works by using guide RNAs (gRNAs) to direct the Cas9 enzyme to a specific DNA site, where it cuts the DNA. The cell then repairs the cut, which can fix or alter the DNA sequence. However, traditional CRISPR-Cas9 systems can sometimes inadvertently affect other parts of the genome, known as “off-target” effects. Although scientists have made improvements to increase accuracy, these changes often reduce editing efficiency.
Altered FnCas9
To solve this problem, researchers are studying the enzyme FnCas9 in the bacterium Francisella novicida. This enzyme is more accurate and efficient than the SpCas9 variant, but generally less effective. The CSIR-IGIB team improved FnCas9 by changing the amino acid interactions with the PAM sequence. This increases its ability to bind to DNA and makes gene editing more effective. These modifications also helped the enzyme reach hard-to-reach areas of the genome.
Improve diagnostic capabilities
Experiments have shown that the improved FnCas9 can more efficiently identify specific single-nucleotide changes in DNA than the unmodified version, doubling the ability to detect disease-associated genetic variations. The improved FnCas9 was tested in human kidney and eye cells and showed greater accuracy than SpCas9 with minimal off-target effects. This highlights its potential for treating genetic disorders.
Delivery of congenital amaurosis 2 (LCA2)
The improved FnCas9 enzyme was used to correct a mutation in the RPE65 gene that causes a type of blindness called LCA2. The editing almost completely corrected the mutation and retinal cells produced normal protein. This method works better than the older system. Because of these promising results, scientists now want to use stem cells from individual patients. They plan to edit these stem cells to fix the mutation and then transplant them back into the patient. This approach could be safer and more accurate than using CRISPR directly on a patient.
Sudarshan Sinha
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