Study identifies highly efficient new Cas9 for in vivo genome editing

A collaborative study between researchers from the Broad Institute of MIT and Harvard, MIT, and the NIH-NCBI has identified a highly efficient Cas9 nuclease that overcomes one of the primary challenges to in vivo genome editing.

This finding, published today in Nature, is expected to help make the CRISPR toolbox accessible for in vivo experimental and therapeutic applications.

Originally discovered in bacteria, the CRISPR-Cas9 system enables the cutting of DNA as a defense mechanism against viral infection. Although numerous microbial species possess this system, the Cas9 enzyme from Streptococcus pyogenes (SpCas9) was the first to be engineered for altering the DNA of higher organisms, and has since emerged as the basis for a series of highly versatile genome modification technologies.

In order to perturb genes in adult animals, key components of the CRISPR-Cas9 system must be introduced into cells using delivery vehicles known as vectors. Adeno-associated virus (AAV) is considered one of the most promising candidate vectors, as it is not known to cause human disease and has already gained clinical regulatory approval in Europe. However, the small cargo capacity of AAV makes it challenging to package both the SpCas9 enzyme and the other components required for gene editing into a single viral particle.

The Cas9 nuclease from the bacteria Staphylococcus aureus (SaCas9), presented in this new work, is 25% smaller than SpCas9, offering a solution to the AAV packaging problem.