enhanced FnCas9

Source: The Hindu 30-07

using CRISPR-Cas9, researchers can add, remove, or alter specific DNA sequences in the genomes of animals. This system has been used in various fields, including in agriculture — to improve the nutritional value of plants and increase their yield — and in healthcare to diagnose several diseases and treat genetic disorders.

The CRISPR-Cas9 gene editing tool uses a guide-RNA (gRNA) designed to find and bind to a specific part of the target genome. The gRNA directs an enzyme, Cas9, to the target site, which is followed by a short DNA sequence called the protospacer adjacent motif (PAM). Cas9 recognises and binds to the PAM sequence, and acts as a molecular scissor that snips some damaged DNA. This automatically triggers the cell’s DNA repair system, which repairs the snipped part to insert the correct DNA sequence.

But the CRISPR-Cas9 system can also recognise and cut parts of the genome other than the intended portion. Such “off-target” effects

SpCas9 enzyme derived from Streptococcus pyogenesbacteria.

Cas9 enzymes from Francisella novicidabacteria. While this Cas9, called FnCas9, is highly precise, it has low effciency as well.

The researchers tinkered with amino acids in FnCas9 that recognise and interact with the PAM sequence on the host genome. “By doing this, we increase the binding affnity of the Cas protein with the PAM sequence"

enhanced FnCas9 cut target DNA at a higher rate compared to unmodified FnCas9. enFnCas9 outperformed unmodified FnCas9.

Nucleotides are the building blocks of DNA and RNA. Each nucleotide consists of a nucleobase, a phosphate group, and a sugar. Each nucleotide in DNA has one of four nucleobases: adenosine, thymine, guanine, and cytosine.

With an indigenous patent for such a high precision editor, we are now in a better position to develop newer therapeutics at affordable costs for people in low- and middle-income countries like ours.