... Bucay, N., Hinton, A., Firpo, M T., King, C C., and Hayek, A (20 05) Activin A maintains pluripotency of human embryonic stem cells in the absence of feeder layers Stem Cells 23, 489-4 95 Besser, ... H., and Miyazono, K (2007) Activin-Nodal signaling is involved in propagation of mouse embryonic stem cells J Cell Sci 120, 55 - 65 Oh, S P., and Li, E (1997) The signaling pathway mediated by the ... H D., and Andrews, P W (2004) Specific knockdown of Oct4 and beta2microglobulin expression by RNA interference in human embryonic stem cells and embryonic carcinoma cells Stem Cells 22, 659 -668...