Researchers from the University of Alabama at Birmingham have successfully used CRISPR to target neurons. With their novel approach, the team led by Jeremy Day was able to manipulate the function of neurons in vivo.
CRISPR, a self-defense system for bacteria against viral invaders, has become a very popular gene editing tool, as it allows researchers to make very targeted changes to an organism’s DNA. Normally using CRISPR-Cas9, the process involves a piece of guide RNA guiding Cas9 to the desired gene where it cuts it, rendering the gene inexpressible.
However, Day’s team used a different CRISPR mechanism, CRISPRa, which increases the expression of the desired gene. For their CRISPRa, they used CRISPR-dCas9, a CRISPR system with a deactivated Cas9, to which they attached transcriptional effectors. This allowed the guide RNA to guide the transcriptional effectors to a particular gene so it could be up-regulated, increasing its expression. In focusing on neurons, Day’s team targeted the promoter sequence for SYN genes, a common group of genes in the brain that code for proteins that regulate neurotransmitters, and designed their guide RNA accordingly.
After injecting their effector-coupled dCas9 system into live rats using viral hosts, the desired genes were successfully up-regulated, with the researchers viewing their new protein products after the fact through fluorescent markers in cell samples. Following this achievement, Day and his team expanded their CRISPR-dCas9 system, incorporating multiple guide RNAs into a single system to target multiple sections of DNA at the same time and using it analyze the complex Bdnf gene that has multiple promoters and plays a core role in brain function and development.
This innovative approach to targeting genes in the brain has far-reaching applications, allowing for versatile gene editing in live animals, which, in the words of Vanderbilt Brain Institute researcher Erin Calipari, “is going to give us an unprecedented view of the role of gene expression in behavior”.
From psychology to physiology and beyond, there is no doubt that this discovery’s molecular insight will give us a far greater understanding of the brain.