Starting in 2016, the above hybrid ‘Target-AID’ system of cytosinedeaminases was extensively used for developing a large number of plasmidvectors (Komor et al., 2016), which were described as base editors (BEs). TheseBEs were successfully used for generatingprecise C®T mutations in anumber of mouse/Xenopus/human livingcells and embryos. In case of mouse and Xenopus,the modified embryos were also used for transplantation in surrogate mothersfor generating offsprings exhibiting altered phenotypes (e.g., black to albinobody colour).
In plant systems also, protoplasts were successfully used forcreating mutations in specific genes, and then regenerated into whole plantsexhibiting desirable altered traits. In 2017, adenine deaminases were alsodeveloped in the laboratory, so that adenine base editors (ABE) becameavailable for conversion of adenine into inosine, so that it became possible toreplace A:T base pair by G:C (A:T®I:T®G:C) (Gaudelli et al. 2017). In this mannerCRISPR/Cas was modified and used in the form of BEs, and ABEs, which broughtmani fold efficiency and precision to gene editing technology. The technique of single base editing was particularly developedand nurtured by a team of workers, which was ledby David Lui (Fig. 2), a Professor of Chemistry and Chemical Biology at HarvardUniversity.
He is also a core member of the internationally known BroadInstitute of MIT in USA. Keeping in view the revolution that BEs brought in geneediting technology during 2016-17, David Lui was listed as first of the ten people, who mattered in the year2017 according to Nature10 (Volume 552, Issue 7685). In the present article, anattempt has been made to describe this new approach of single base-editing andto review the progress made in this subject during 2016 and 2017. The authorhopes that thearticle will prove usefulfor teachers and students in developingawareness about this very activeand exciting area of research. The progress made in the development and use of BEswas summarized in five articles thatappeared in a special issue of Nature Biotechnology in May 2017(see later). These five papers included paperson base editing in mouse embryos as well as in crops including rice, wheat, maize and tomato.