Research: Staying immature
22 January 2008
For several years, the Nanog gene had been regarded as a key regulator of embryonic stem cell fate. It is expressed in embryonic stem cells and, when the dose of the gene was reduced, stem cells typically adopted mature cell fates. Furthermore, Nanog has been identified as a gene involved in transforming adult cells to an embryonic stem-like state.
Now, in work carried out at the University of Edinburgh, Ian Chambers and colleagues have given their field a big surprise by showing that Nanog is not essential for growth of embryonic stem cells, but rather helps to maintain their stem cell state and has an additional specific role in the development of germ cells.
Using a fluorescently tagged Nanog gene, the researchers found that mouse embryonic stem cells that had switched off Nanog could switch it back on again. When the gene was deleted entirely, the growth of the cells slowed, but many retained a stem cell identity. Critically, stem cells lacking Nanog could contribute to nearly any adult tissue when injected into embryos. The key exception appears to be germ cells, which go on to become egg- and sperm producing tissues: without Nanog, they do not mature. The researchers suggest that Nanog acts like a dimmer switch to allow stem cells to resist signals that would normally cause them to mature.
Image: Human embryonic stem cells; Annie Cavanagh, Wellcome Images
References
Chambers I et al. Nanog safeguards pluripotency and mediates germline development. Nature 2007;450(7173):1230-4.
This research was funded in part by the Wellcome Trust.