Pluripotent stem cells can divide into daughter cells that maintain the ability to give rise to all cell types in the body, or they can be triggered to differentiate into a specialized state. In 2006 two groups published Hot Papers that began to tease out the networks of regulators that control the pluripotency-differentiation decision.
Richard Young at the Whitehead Institute and collaborators investigated the Polycomb complex in one of the Hot Papers. The Polycomb group of regulator proteins was first described as repressors of homeotic genes in Drosophila research from the late 1970s. Homeotic genes control segment identity in the developing fly embryo, and the absence of Polycomb components is lethal.
Young and colleagues found that the Polycomb complex occupies and prevents expression of a set of developmental genes, more than 200 in all, in human embryonic stem cells that must be repressed to maintain pluripotency. Surprisingly, many of these ...
