Indian researchers have reported the precise genome-editing potential of a protein found in the pathogenic bacterium Francisella novicida1. The protein, they say, could potentially be used to correct genetic mutations that cause sickle cell anemia and other single-gene disorders.
Bacteria use CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9), a specific system of DNA sequences and a protein that selectively detects and destroys parts of viral DNA, eventually disabling viruses.
In labs, such systems have been seen selectively targeting specific parts of human genome, adding or deleting pieces of genetic material.
The Cas9 protein found in F. novicida has earlier been shown to have high specificity to recognize and bind to DNA bases. Its genome-editing property, however, remained unexplored.
To find out, scientists from the Institute of Genomics and Integrative Biology in New Delhi incubated different DNA sequences with equal amounts of the bacterial protein, which is actually an enzyme. They found that the enzyme completely cleaved the DNA targets within 30 minutes to two hours.
Remarkably, the enzyme didn’t cut DNA sequences with 2 or 3 mismatches, suggesting that it is extremely specific in recognising its target. It also showed negligible or no affinity for off-target DNA sequences.
The researchers, led by Debojyoti Chakraborty, found that the enzyme could bind to DNA in specific mouse cells.
Next, they probed its genome-editing prowess in sickle cell anemia mutation in an Indian patient-derived specific stem cells. The enzyme was able to initiate DNA repair process in these cells, indicating its therapeutic potential.
Chakraborty told Nature India that the team is hoping to conclude preclinical studies with the Cas9 tool and explore the possibility of using it as a therapy for curing sickle cell anaemia.
References
1. Acharya, S. et al. Francisella novicida Cas9 interrogates genomic DNA with very high specificity and can be used for mammalian genome editing. Proc. Natl. Acad. Sci. Unit. States. Am. (2019)Doi:10.1073/pnas.1818461116
