Abstract
Somatic cells have been reprogrammed into induced pluripotent stem (iPS) cells that recapitulate the pluripotent nature of embryonic stem (ES) cells. Reduced pluripotency and variable differentiation capacities have hampered progress with this technology for applications in regeneration medicine. We have previously shown that germ cell nuclear factor (Gcnf) is required for the repression of pluripotency genes during ES cell differentiation and embryonic development. Here we report that iPS cell lines, in which the Gcnf gene was properly reprogrammed, allowing expression of Gcnf, repress pluripotency genes during subsequent differentiation. In contrast, iPS clones in which the Gcnf gene was not reprogrammed maintained pluripotency gene expression during differentiation and did not differentiate properly either in vivo or in vitro. These mal-reprogrammed cells recapitulated the phenotype of Gcnf knockout (Gcnf(-/-)) ES cells. Reintroduction of Gcnf into either the Gcnf negative iPS cells or the Gcnf(-/-) ES cells rescued repression of Oct4 during differentiation. Our findings establish a key role for Gcnf as a regulator of iPS cell pluripotency gene expression. It also demonstrates that reactivation of the Gcnf gene may serve as a marker to distinguish completely reprogrammed iPS cells from incompletely pluripotent cells, which would make therapeutic use of iPS cells safer and more practical as it would reduce the oncogenic potential of iPS cells.