Release date: 2017-02-24
IBS scientists have discovered the smallest member of the CRISPR-Cas9 family to date, and studies have shown that it can edit mutant blinding genes through adeno-associated viruses.
Researchers at the Institute for Basic Science (IBS) and Seoul National University in Korea have designed the smallest CRISPR-Cas9 and delivered it to muscle cells and mice via adeno-associated virus (AAV). In the eyes, to edit the genes that cause blindness.
The findings, published in Nature Communications, from the C. jejuni (CjCas9) system, may become a new tool for the treatment of general diseases and "incurable" diseases in the future.
CRISPR-Cas9 is red-purple, and as a "genetic scissors" protein, Cas9 needs to be cleaved at the precise target gene position under the guidance of a targeting RNA. The CRISPR-Cas9 complex needs to be delivered by plasmid or virus in order to reach the target DNA. KIM Jin Soo, director of the IBS Genomics Engineering Center, explained: "AAV is an effective and safe vector for the expression of target genes in vivo and has been widely used in gene therapy."
In its natural state, Cas9 is an immune weapon for bacteria that cuts viral DNA that can damage bacteria. The most common CRISPR-Cas9 technique uses Cas9 derived from S. pyogenes. However, this protein consists of 1,368 amino acids and is too bulky to be packaged and delivered via AAV. Even if scientists divide it into two parts, each wrapped in a different virus, there will be other problems, such as requiring twice the amount of virus, the activity is smaller than the complete Cas9. Staphylococcus aureus Cas9 can also be used for gene editing and is slightly smaller (1,053 amino acids), so it can be transmitted by AAV, but this Cas9 does not have enough space to load other proteins.
In this latest study, the researchers found that CjCas9 is the right size and efficient. This protein has 984 amino acids and can be packaged into AAV along with multiple targeting RNAs and fluorescent reporter genes.
In order to use bacterial proteins for gene editing, the researchers optimized the technique by designing a short DNA sequence next to the Cas9-targeted DNA sequence, the Protospacer Adjacent Motif (PAM). Each different Cas9 requires a specific PAM sequence, otherwise it will not bind and cleave the target DNA sequence. In addition, the researchers also modified the length of the targeting RNA.
After completing this optimization, the researchers packaged the new CRISPR-Cas9 complex, along with two targeting RNAs and fluorescent reporter proteins, into AAV for delivery to mutant genes in mouse muscle and eyes. They focus on two genes involved in age-related macular degeneration (AMD), which is one of the leading causes of blindness in adults.
One gene is a common therapeutic target for ADM, called vascular endothelial growth factor A (VEGF A), and the other is a transcription factor that activates VEGF A transcription: HIF-1a. The latter has not previously been used as a drug target. In this study, the team demonstrated that CjCas9 is transmitted to the retina via AAV, effectively inactivating Hif-1a and VEGF A in mice and reducing the area of ​​choroidal neovascularization (CNV).
KIM Jin-Soo explained: “CjCas9 is highly specific and does not exhibit off-target mutations in the genome.â€
Original search
In vivo genome editing with a small Cas9 orthologue derived from Campylobacter jejuni
Source: Biopass
Reusable Pen Injector,Cartridge Injection Pen,Injector For Self-Administrition,Customized Pen Injector
Shanghai Enjosim Medical Technology Co., Ltd , https://www.enjosimmedical.com