Genome editing using CRISPR, CAST, and Fanzor systems

Abstract

Genetic engineering technologies are essential not only for basic science but also for generating animal models for therapeutic applications. The clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas) system, derived from adapted prokaryotic immune responses, has led to unprecedented advancements in the field of genome editing because of its ability to precisely target and edit genes in a guide RNA-dependent manner. The discovery of various types of CRISPR-Cas systems, such as CRISPR-associated transposons (CASTs), has resulted in the development of novel genome editing tools. Recently, research has expanded to systems associated with obligate mobile element guided activity (OMEGA) RNAs, including ancestral CRISPR-Cas and eukaryotic Fanzor systems, which are expected to complement the conventional CRISPR-Cas systems. In this review, we briefly introduce the features of various CRISPR-Cas systems and their application in diverse animal models.

Keywords: Clustered regularly interspaced short palindromic repeats-associated protein; Clustered regularly interspaced short palindromic repeats-associated transposons; Fanzor; Genome editing; IscB; TnpB.

Fig. 1

History of research on CRISPR-Cas and OMEGA systems. It has taken more than 2 decades to demonstrate genome editing using the CRISPR-Cas system. Over the next 10 years, there has been remarkable progress in genome editing technology together with the discovery of diverse CRISPR-Cas variants (Cho et al., 2013a, Ishino et al., 1987, Jansen et al., 2002).

Fig. 2

Structures of nuclease domains of CRISPR-Cas and OMEGA systems. The type II system has RuvC and HNH nucleases, whereas the type V system has only RuvC nuclease. Type VI systems contain RNA nucleases, such as HEPN. The OMEGA systems have only RuvC nuclease similar to the type V. HEPN, higher eukaryotic and prokaryotic nucleotide-binding.

Fig. 3

Phylogenetic tree of CRISPR-Cas and OMEGA systems. OMEGA systems are phylogenetically correlated with the CRISPR-Cas system.