Dr. Lukas Oesinghaus, The Simmel Lab, School of Natural Sciences, Technical University of Munich

Engineering conditional Cas12a guide RNAs
CRISPR systems such as Cas9 and Cas12a have enabled researchers to exert unprecedented control over an organism’s genome and transcriptome.

For many applications in basic research and therapeutics, it is desirable to constrain their activity to specific environments, such as target tissues in therapeutic applications. Here, we introduce such spatiotemporal control of Cas12a by engineering its associated guide RNAs (gRNAs) to exhibit conditional activity, primarily through toehold-mediated strand displacement.

We first establish RNA-activated Cas12a gRNAs in vitro, then adapt the resulting system to work in both bacterial and mammalian cells. For the latter, we investigate two different implementations: A straightforward approach using the Pol III-based U6 promoter and a less obvious method using a Pol II promoter, which allows for the integration of the Cas12a coding sequence along with several conditional gRNAs on a single transcript, resulting in highly compact, multiplexed molecular computing constructs.