Classification and Functional Diversity of CRISPR-Cas Systems with Emerging Editing and Delivery Tools

Abstract

The CRISPR-Cas system originates from the adaptive immune mechanism of microorganisms and has now evolved into a revolutionary gene-editing tool, driving rapid development in the field of molecular biology. This system is systematically classified into two major categories: Class 1 (multi-protein complexes) and Class 2 (single-protein effectors), covering six main types, including DNA-targeting Cas9, Cas12 and RNA-targeting Cas13. These types possess diverse editing and regulatory functions. In recent years, this technology has not only achieved precise gene knockout and repair, but also derived new tools such as base editing and prime editing, which have significantly improved editing accuracy and expanded application scope. In addition, CRISPR technology has gone beyond gene editing itself and been applied in transcriptional regulation (CRISPRa/i) and molecular diagnostics (e.g., high-sensitivity nucleic acid detection). However, this technology still faces challenges in terms of delivery efficiency, safety and specificity. In particular, the limitations of viral vectors in packaging capacity and immunogenicity have promoted research on non-viral vectors (such as lipid nanoparticles, LNP) and physical delivery methods. This article reviews three aspects of the CRISPR system: classification and functions, evolution and optimization of editing tools, and delivery technologies, and looks forward to its broad prospects in the fields of genetic disease treatment, infectious disease detection and cell programming.