Table 1.

Recent Advances in CRISPR-based Genome Editing

Advancement	Reference
Cas variants (other than wild-type SpCas9)
Smaller nuclease size
Staphylococcus aureus Cas9 (SaCas9)	[12]
Streptococcus thermophilus Cas9 (St1Cas9)	[12]
Controllable sticky end generated
Prevotella and Francisella 1 Cas (Cpf1)	[3]
Class 2 Cas (C2c1)	[13]
More relaxed PAM
Francisella novicida Cas9 (FnCas9)	[16]
Higher specificity
Enhanced specificity SpCas9 (eSpCas9)	[17]
High-fidelity SpCas9 (SpCas9-HF1)	[4]
Double nicking Cas9 (Cas9 nickase)	[18]
Targeting single-stranded RNA
Leptotrichia shahii Cas (C2c2)	[14]
Altered PAM specificities to broaden the Cas9 application
Streptococcus pyogenes Cas9 (SpCas9)	[12]
Staphylococcus aureus Cas9 (SaCas9)	[12]
Altered sgRNA and Cas9 to improve genome-editing efficiency and specificity
Chemically modified sgRNA	[6]
Truncated sgRNA	[19]
Improved homologous recombination-mediated DNA replacement and gene knockin
Asymmetric donor DNA	[20]
Homology-directed repair (HDR) enhancer	[21]
Inhibit non-homologous end joining (NHEJ) activity	[22]
NHEJ homology-independent knock-in	[24]
Silent CRISPR/Cas-blocking mutations	[23]
Base editing approach	[25]
Efficient delivery vehicles
Serotype-specific AAV viral vector	[5]
Combine use of lipid nanoparticle and AAV viral vector	[55]