UC Berkeley researchers have developed an improved method for gene-editing in mice that will allow for more efficient and accessible genetic modeling.
The new process provides a more direct mechanism for inserting CRISPR-Cas9, a protein that was discovered in October 2015 by UC Berkeley researchers and has shown promise as a gene-editing tool. According to the researchers, their work will allow for an easier, faster and less expensive means of altering the genes of mice, opening up greater opportunities for research into human genetics and hereditary diseases.
The researchers’ new method — called CRISPR RNP Electroporation of Zygotes, or CRISPR-EZ — employs electroporation, a lab technique in which electricity is used to open up microscopic pores in mouse embryos. According to Sean Chen, a campus graduate student and researcher for the project, the technique facilitates easier production of genetically modified, “knockout” animals, which are used to study genetic conditions.
“This new technique will potentially revolutionize the ability to rapidly generate transgenic and knockout mice for studying a multitude of processes and disease states,” said Gary Firestone, professor of cell and developmental biology, in an email. “The fidelity and efficiency of this approach is remarkable.”
According to Chen, current methods of injecting CRISPR molecules involve microinjections of mRNA into the embryos, a process with a low success rate and high cost. Chen said that, while traditional microinjections have about a 10 to 15 percent embryo survival rate, insertions of CRISPR proteins using electroporation have a 30 to 50 percent survival rate.
In addition, the new process allows complete CRISPR-Cas9 molecules with accompanying guide RNA — rather than the usual mRNA — to be inserted into the embryo in order to make direct alterations to the mouse’s genes.
“(This technique) enables a lot of laboratories that wouldn’t otherwise be able to make genetically modified mice to do so with unprecedented cost and speed,” Chen said.
Dirk Hockemeyer, assistant professor of cell and developmental biology, said that, while the production of genetically modified mice was possible before, this research is significant for streamlining the process. According to Hockemeyer, the CRISPR-EZ method could produce mice in as little as four weeks and could be “really important for studying cancer and other conditions.”
Jacob Corn, director and principal investigator of the Innovative Genomics Initiative, provided input for the research, and said in an email that CRISPR-EZ is “a big step towards making mouse models easy.” Corn referenced the project’s lead researcher Lin He, an associate professor of cell and developmental biology, as contributing to the development of genetically modified animals.
“With (He’s) work, just about any lab has the capability to make mouse models without needing to rely on onerous or time-consuming injection techniques,” Corn said in an email.