Scientists have used the smallest Cas9 gene scissors to date to treat eye disease.

Scientists from South Korea have developed the smallest CRISPR-Cas9 to date using engineering techniques, which are delivered to muscle cells and eyes in mice via adeno-related viruses (AAVs) to modify a gene that causes blindness.
the findings were published in the international academic journal Natue Communications.
the CRISPR-Cas9 system is expected to be a new treatment tool for common and drug-insotress-untreated diseases.
CRISPR-Cas9 is a new, inexpensive and precise gene editing tool.
Cas9 is a "gene scissors" protein that can locate cutting target genes under the guidance of guiding RNA.
to help CRISPR-Cas9 reach the target DNA, it needs to be carried by prosurages or viruses.
AAV is an efficient and safe carrier for gene expression in the body and is widely used in gene therapy.
cas9 used in the most common CRISPR-Cas9 technology is derived from purulent streptococcus, but this Cas9 protein contains 1,368 amino acids that cannot be packaged and transported via AAV.
cas9 from Staphylococcus acolytes can also be used for gene editing, although only 1,053 amino acids can be carried through AAV, but there is not enough room to carry other proteins.
the study, researchers found that CjCas9 was both effective and small enough to consist of only 984 amino acids that could be packaged into AAV along with more than one guide RNA and a fluorescent reporting protein.
researchers have optimized some aspects of the technology.
then packaged the new CRISPR-Cas9 system into AAV, with two guide RNA and a fluorescent reporting protein to mutate genes in the muscles and eyes of mice.
chose two genes involved in aging-related macular degeneration, a disease that causes blindness in adults.
one gene is a common target for treating the disease, called VEGF A, and the other is the transcription factor HIF-1a, which activates VEGF A gene transcription.
study, researchers demonstrated that CjCas9, delivered to the retina via AAV, was effective in inhibiting the activation of the Hif1a and VEGF A genes in mice and reducing the area of new blood vessel formation in the vein membrane.
CRISPR-CjCas9, which is packaged with AAV injections into the eyes, can also be used to treat other retinal and systemic diseases.
CjCas9 is highly specific and does not off-target to cause other mutations in the genome.
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