Cytosine methylation is essential for normal embryonic development, X chromosome inactivation, genomic imprinting and transposon silencing. In mammals, DNA methylation at CG dinucleotides is unique because it has the ability to be maintained in the absence of signals which created it. This molecular memory system is dependent upon the symmetry of CG dinucleotides, allowing methylation marks to be copied to a cognate CG on the reverse strand following replication through the action of DNA methyltransferase DNMT1. Significantly, molecular memory could be transmitted by further symmetric DNA sequences, including the CHG context (where H is any non-C nucleotides). In plants, CHG nucleotides carry epigenetic information in a manner that is CMT3 methyltransferase dependent. We propose to overexpress the plant CMT3 protein in cultured mammalian cells, and create for the first time epigenetic memory outside of the canonical CG context. In this research we will be testing the catalytic activity of the CMT3 enzyme using bisulphite sequencing to measure the global methylation level after CMT3 transfection, either in the present of existing CG methylation (when CMT3 is introduced into wild-type cells) or in the absence of other methylation system (when CMT3 is introduced into DNMT-TKO cells). Additionally we will also endeavour to investigate the potential implications such a modification to the epigenome could have to the developmental potency and morphology of the mouse embryonic stem cells. This work has significance for the emerging field of ‘synthetic epigenetics’ and could have extensive biotechnological and medical applications.