Application of the CRISPR/Cas9-based gene editing technique in basic research, diagnosis, and therapy of cancer

Table 1 Comparison of Cas9 variants

Year	Variant of Cas9	PAM(5’to3’)	Application	References
2012	SpCas9	NGG	Multiplex genome editing in mammalian cells.	[14]
2015	SaCas9	NNGRRT	Highly efficient genome-editing by the AAV-SaCas9-gRNA vector system.	[42]
2015	SpCas9-VRER	NGCG	Modification of previously inaccessible sites in zebrafish embryos and human cells	[36]
2017	CjCas9	NNNVRYM	In Vivo Genome Editing with CjCas9 in TA Muscles of Dmd Knockout Mice	[43]
2018	xCas9–3.7	NG, GAA, GAT	Base substitution of C•G → T•A and A•T → G•C for the pathogenic mutation sites	[39]
2018	SpCas9-NG	NG	Efficient and accurate genome editing in mouse zygotes and somatic culture cells	[44]
2018	evoCas9	NGG	Limits the unspecific cleavage of a difficult-to-discriminate off-target site and fully abrogated the cleavage of two additional off-targets	[45]
2020	SpRY	PAM sequence has not been characterized	Precise editing to extend almost to the entire genome	[32]

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