致敬韩春雨老师-“不鸣则已，一鸣惊人

一项国内重大原创-科学网鉴定一下

NgAgo Gene Editing - horizondiscovery.com

罗列了其技术优势：

In May 2016, a DNA-guided nuclease suitable for genome editing in cells was reported by Gao et al in Nature Biotechnology.  Like CRISPR-Cas9, NgAgo can introduce targeted double strand breaks in mammalian cells (the paper reports targeting in MCF7, K562 and HeLa cells). However, NgAgo differs from the CRISPR Cas9 system in a number of  ways:

• It uses a DNA guide and not RNA as a guide for targeting a genomic site

• It removes several nucleotides within its target region rather than just introducing a break

• The guide can be 24 nucleotides long, while sgRNAs for Cas9 are limited to 20 nucleotides of homology

• NgAgo has no requirement for a PAM site - meaning there are potentiall no target sequence restrictions

Alongside these differences the system has a number of other nice features that lend it to genome editing with potentially high fidelity:

• It requires 5' phosphorylated ssDNA as a guide. These types of nucleotide are not found in high abundance in human cells

• Once loaded with its guide it will not swap it for unbound free oligos - further minimizing the possibility it will be loaded with unexpected guides.

• The system is highly sensitive to single base mismatches along the length of the guide

• Evidence from Gao et al suggests NgAgo can drive HDR with high efficiency (>10%)

• It's smaller than Cas9 - 887aa vs 1368aa

Finally, Gao et al compared the targeting efficiency of NgAgo with Cas9 directly. At a well studied gene target (DYRK1A) the efficiency of the two systems was comparable (31.97% for NgAgo vs 32.2% for Cas9). However in GC rich loci NgAgo was found to perform significantly better. This observation, coupled with the lack of requirement for PAM makes this a potentially very exciting expansion to the genome editors tool box.

注：PAM: