Abstract
Much of the CRISPR narrative as a revolutionary technology over the past decade has been based on the ease with which this tool has been adopted and the speed at which it can be deployed. After all, it is CRISPR technology that was recognized as a Nobel-worthy invention—not the early work on the discovery of CRISPR-Cas immune systems, nor its deployment for genome editing in human cells, but the quintessential development of a disruptive genome editing tool.
Ten years into the genome editing revolution, we have reached a point where this mature technology is, in turn, spurring novel support technologies that themselves make CRISPR better, easier, and more convenient. Popular nucleases such as Cas9 and Cas12 have been fused to transcriptional regulators and epigenome modifiers, and also engineered as chimeric effectors in combination with other enzymes carrying out a plethora of reactions such as deamination, reverse transcription, transposition, integration, and more.
This issue of The CRISPR Journal encompasses a series of new tools and techniques that further enable the technology and its users for next-generation genome editing.
The rise in base editing therapeutic applications hinges on specific and efficient effectors. On page 430 of this issue, Rieffer et al. present cytosine base editor reporter systems (ARSENEL) designed to evaluate editing levels for NC dinucleotide motifs, and document specificity and efficiency across widely used APOBECs with varying dinucleotide editing preferences. This work lays the foundation to develop increasingly specific therapeutic constructs for base editing modalities.
Expanding the focus on specificity and efficiency of genome editors, Richardson et al. (page 447) present a study on Cas9-mediated knock-in leveraging combinatorial DNA repair protein fusions, featured on the cover of this issue. The authors used repair proteins eRad18 and CtlP (Cas9-RC) to increase the frequency of knock-ins, with implications for reducing heterogeneity in ex vivo applications.
Transitioning to CRISPR-edited cells, a report by Zhang et al. (see page 462) covers computational and experimental approaches (GMUSCLE) to streamline the qualitative and quantitative genotyping of edited cells using multiplexed sequencing of bulk populations. This streamlined approach is more efficient and scalable than incumbent alternatives and a simplified integrated protocol to enable users.
Likewise, a study by Mologu et al. (page 473) in human induced pluripotent stem cells (iPSCs) presents a new method using trichostatin A, a histone deacetylase inhibitor, to decrease chromatin condensation and increasing gene editing efficiency and specificity. This accelerates isogenic iPSC development for disease modeling, drug discovery, and regenerative medicine applications.
Looking ahead to the more distant future, Pescod et al. (page 419) show that gene-driven targeting of Anopheles gambiae, the human Malaria vector, can efficiently overcome small polymorphisms and large chromosomal inversions that occur at the population level, indicating that genetic heterogeneity is not a hindrance to deployment. At a time when disease prevention rather than therapeutic management is en vogue, devising broadly applicable genetic controls of disease has tremendous upside.
Lastly, a review article by Song et al. covers recent advances in Cas12a-based diagnostics, showing how efficient and specific CRISPR effectors can be repurposed for amplification-free detection of nucleic acids for next-generation diagnostics (page 405). Importantly, this review highlights several studies illustrating the ability of CRISPR-based diagnostics based on fluorescence-, electrochemical-, nanomaterial-, and lateral flow-based assays to detect diverse nucleic acids of interest. At a time when vaccines, antivirals, and lurking infectious diseases are on our minds (yet again), access to affordable and customizable home-based diagnostics is urgently needed.
As outlined in the call for our next special issue on CRISPR Trials and progress in the clinic, we are on the cusp of a revolution in personalized medicine to make CRISPR the standard of care for gene and cell therapies in the near future. What may have been an aspirational dream a decade ago is most likely to become a therapeutic reality for patients over the next decade, transcending translational gaps and challenges at unfathomable speed. This hinges on developers and users being able to deploy this technology at speed and at scale across many therapeutic applications to generate these CRISPR-based personalized medicines—as nicely outlined in the collection of articles featured in this issue.