CRISPR Knockin Mice Enable Rapid Gene Editing

By Bio-IT World Staff

September 26, 2014 | Researchers at the Broad Institute of MIT and Harvard have created a line of mice whose cells naturally express the Cas9 protein used in CRISPR gene editing. These mice can be used for virtually any gene knockdown experiment, allowing researchers to quickly and easily alter the expression of one or more regions of the genome at any stage in the mouse's life.

The Cas9 protein, when directed by a guide RNA molecule to a matching stretch of DNA, cuts that DNA directly from the chromosome, making this CRISPR method by far the most flexible tool for gene editing yet discovered. (CRISPR is named for Clustered Regularly Interspersed Short Palindromic Repeats, a kind of signature DNA sequence associated with Cas9 that, in bacteria, encodes the guide RNA.) Until now, researchers using CRISPR have created complexes that include both Cas9 and guide RNA, delivering these to cells in order to switch off or modify specific genes. However, with the new Cas9-expressing mice, only the guide RNA has to be introduced to change the native genome, an easier proposition well within the capabilities of most biology labs.

The Broad Institute team, supervised by CRISPR pioneer Feng Zhang and his colleague Phillip Sharp, also demonstrated the power of their knockin mice by inducing lung cancer-related mutations. Using an adeno-associated virus as a vector for guide RNA sequences, the team simultaneously altered the KRAS, p53 and LKB1 genes, which resulted in adenocarcinoma in the mice. The work is published in this week's Cell.

CRISPR knockin mice have already been shared with more than a dozen institutions, and are available for purchase through the Jackson Laboratory, a popular national resource for genetically modified animal models.