An additional strategy which has recently been developed is the use of Cas9 to recruit cytosine deaminase enzymes usually involved in somatic hypermutation in immune cells (such as the Apobec and AID enzymes) to edit the sequence of the genome without inducing a DSB (Hess et al. 2016; Komor et al. 2016; Nishida et al. 2016) (Fig. 4g). Whilst this could be informative in terms of screening and for certain specific mutations, its general application in disease modelling is somewhat limited, since only transitions from cytosine to thymine are possible.
