Beyond CRISPR: single base editors for human health and crop improvement

During 2016-2018, CRISPR/Cas9 technology was modified using disabled Cas9 with nickase activity in combination with cytosine/adenine deaminases for the development of four generations of cytosine base editors (BE1-BE4) for C -> U conversion and at least seven generations of adenine base editors (ABE1-ABE7) for A -> I conversion. These base editors exhibited improved efficiency and reduced frequency of deletions among the products. Further improvement in the form of enhanced base editors and high-fidelity base editors was achieved through the use of 1-3 copies of uracil N-glycosylase inhibitors and phage Mu-Gam protein. The technology will bring precision to gene editing technology for human healthcare and crop improvement.