A study in the June 2007 issue of Nature Cell Biology investigates how pluripotency, the ability of a stem cell to differentiate into every cell type of the adult organism, is regulated.
Understanding how stem cells maintain their pluripotent state has involved the characterisation of a multitude of transcription factors -- the proteins that determine whether a specific gene is expressed or not. Pluripotency in embryonic stem cells was thought to be controlled primarily by the transcription factors Oct3/4 and Sox2, as these proteins were believed to activate Oct-Sox enhancers -- regulatory regions that determine the expression of pluripotent stem cell-specific genes. Shinji Masui and colleagues used mutant mice lacking the Sox2 gene to show that although Sox2 is needed for stem cell pluripotency, it is not required for the enhancers to function and in fact governs the expression of Oct3/4. The authors went on to show that this regulation is indirect, as Sox2 controls the expression of a number of transcription factors that in turn regulate Oct3/4 expression.
This study illustrates the precise regulation of pluripotency by key proteins, and reorders the hierarchy of these factors with Sox2 as the master regulator -- another small step towards a complete understanding of stem cell biology.
Shinji Masui (International Medical Center of Japan, Tokyo, Japan)
Abstract available online.
(C) Nature Cell Biology press release.
Message posted by: Trevor M. D'Souza