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. Author manuscript; available in PMC: 2022 Aug 1.
Published in final edited form as: Trends Mol Med. 2021 Jan 8;27(8):792–806. doi: 10.1016/j.molmed.2020.12.008

Fig. 3. Methods for precision genome editing of mice.

Fig. 3

A. Conventional genome editing approach. A desired mutation (red star) can be incorporated into the genome when the host cell’s HDR-repair machinery repairs the DSB produced by Cas9. B. Base editing (BE) approach. A Cas9 that produces only single-strand breaks (nicks) works with a deaminase. The deaminase chemically modifies a specific cytidine base (C) to uracil (U). The nick is repaired, converting a guanine–uracil (G–U) intermediate to an adenine–thymine (A–T) base pair. C. Prime editing (PE) approach. A nick-producing Cas9 and a reverse transcriptase produce nicked DNA into which sequences corresponding to the guide RNA have been incorporated. The original DNA sequence is excised, then the nicked strand is repaired to produce a fully edited duplex. RT, Reverse transcriptase. D. Conventional pronuclear injection. The 2-cell stage zygotes are delivered to the oviduct, while blastocysts are delivered to the uterus. E. The CRISPR-EZ approach [107]. This method of electroporation embryos with CRISPR/Cas9 reagents eliminates the need for microinjection, which requires expensive intrumentation and substantial expertise.