vnewjay

Polycomb Repressive Complex 2 (PRC2) methylates histone H3 tails at lysine 27 and is essential for embryonic development. The three core components of PRC2,Eed, Ezh2, and Suz12, are also highly expressed in embryonic stem (ES) cells where they are postulated to repress developmental regulators and thereby prevent differentiation to maintain the pluripotent state. We performed gene expression and chimera analyses on low and high passage Eed(null) ES cells to determine whether PRC2 is required for the maintenance of pluripotency. We report here that, although developmental regulators are overexpressed in Eed(null) ES cells, both low and high passage cells are functionally pluripotent. We hypothesize that they are pluripotent because they maintain expression of critical pluripotency factors. Given that EED is required for stability of EZH2, the catalytic subunit of the complex, these data suggest that PRC2 is not necessary for the maintenance of the pluripotent state in ES cells. We propose a positive-only model of embryonic stem cell maintenance, where positive regulation of pluripotency factors is sufficient to mediate stem cell pluripotency.

kiteforever

This paper depicts that the EED, which is the component of Polycomb repressive complex 2, if knockout, won't affect the pluripotency of ES cells. However, I doubt how many passages did the author tried in culture these EED null ES cells. As far as I know, PRC 2 is one of the most important key factors inhibiting ES cell differentiation by repress development regulator gene. PRC function in ES cell to keep bivalent domain in key development gene, in short term, maybe it's hard to observe the effect of EED in EED-null ES cells, but indeed, it will have great consequences in ES cells in the long term.

vnewjay

非常同意楼上的看法，我想问题在于，维持self-renewal是一个系统，即使Polycomb Repressive Complex 2也是一个复合物，因此，去掉其中的一部分，并不能完全说明失去它的意义！

就像在创伤状态下，机体会有一定的代偿，以维持机体的运行！