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First published online 30 July 2008
doi: 10.1242/dev.021121
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1 Laboratory of Embryonic Stem Cell Research, Stem Cell Research Center,
Institute for Frontier Medical Sciences, Kyoto University, 53 Kawahara-cho,
Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
2 Department of Development and Differentiation, Institute for Frontier Medical
Sciences, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto
606-8507, Japan.
3 Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, 69
Konoe-cho, Yoshida, Sakyo-ku, Kyoto 606-8507, Japan.
* Author for correspondence (e-mail: hsuemori{at}frontier.kyoto-u.ac.jp)
Accepted 3 July 2008
The canonical Wnt/β-catenin signaling has remarkably diverse roles in embryonic development, stem cell self-renewal and cancer progression. Here, we show that stabilized expression of β-catenin perturbed human embryonic stem (hES)-cell self-renewal, such that up to 80% of the hES cells developed into the primitive streak (PS)/mesoderm progenitors, reminiscent of early mammalian embryogenesis. The formation of the PS/mesoderm progenitors essentially depended on the cooperative action of β-catenin together with Activin/Nodal and BMP signaling pathways. Intriguingly, blockade of BMP signaling completely abolished mesoderm generation, and induced a cell fate change towards the anterior PS progenitors. The PI3-kinase/Akt, but not MAPK, signaling pathway had a crucial role in the anterior PS specification, at least in part, by enhancing β-catenin stability. In addition, Activin/Nodal and Wnt/β-catenin signaling synergistically induced the generation and specification of the anterior PS/endoderm. Taken together, our findings clearly demonstrate that the orchestrated balance of Activin/Nodal and BMP signaling defines the cell fate of the nascent PS induced by canonical Wnt/β-catenin signaling in hES cells.
Key words: Primitive streak, Mesoderm, Endoderm, Stem cells, β-Catenin, Wnt
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