Stable maintenance of de novo assembled human artificial chromosomes in embryonic stem cells and their differentiated progeny in mice.

De novo assembled alphoid(tetO)-type human artificial chromosomes (HACs) represent a novel promising generation of high capacity episomal vectors. Their function and persistence, and any adverse effects, in various cell types in live animals, have not, however, been explored. In this study we transferred the alphoid(tetO)-HAC into mouse ES cells and assessed whether the presence of this extra chromosome affects their pluripotent properties. Alphoid(tetO)-HAC-bearing ES cells were indistinguishable from their wild-type counterparts: they retained self-renewal potential and full capacity for multilineage differentiation during mouse development, whereas the HAC itself was mitotically and transcriptionally stable during this process. Our data provide the first example of fully synthetic DNA behaving like a normal chromosome in cells of living animals. It also opens a new perspective into functional genetic studies in laboratory animals as well as stem cell-based regenerative medicine.