Conditional Gene Editing in Presynaptic Extinction-ensemble Cells via the CRISPR-SaCas9 System.

The CRISPR-Cas9 enables efficient gene editing in various cell types, including post-mitotic neurons. However, neuronal ensembles in the same brain region can still be functionally or anatomically different, and such heterogeneity requires gene editing in specific neuronal populations. We recently developed a CRISPR-SaCas9 system-based technique. Combined with activity-dependent cell-labeling methods and anterograde/retrograde adeno-associated virus (AAV) vectors, this technique achieves function- and projection-specific gene editing in the mammalian brain. We showed that perturbing cbp (CREB-binding protein) in extinction-ensemble neurons among amygdala-projecting infralimbic cortex (IL) cells impaired fear extinction learning, demonstrating the high efficiency in regulation of extinction learning with CRISPR-Cas9. Here, we describe a detailed protocol of gene perturbation in presynaptic extinction-ensemble neurons in adult rats, including gRNA design, gRNA evaluation in vitro, stereotaxic AAV injection, and contextual fear conditioning. The high specificity and efficiency of projection- and function-specific CRISPR-SaCas9 system can be widely applied in neural circuitry studies.