The role of SMAD4 in human embryonic stem cell self-renewal and stem cell fate.
Transforming growth factor (TGF)-beta superfamily proteins play a key role in the regulation of human embryonic stem cells (hESCs). Those of the TGFbeta/activin/nodal branch seem to support self-renewal and pluripotency, whereas those of the bone morphogenic protein (BMP) branch induce differentiation. In contrast to this generalization, we found that hESC remained undifferentiated after knockdown of SMAD4 with inducible short hairpin RNA interference, although the knockdown inhibited TGFbeta signaling and rendered the cells nonresponsive to BMP-induced differentiation. Moreover, the rapid differentiation of hESC after pharmacological inhibition of TGFbeta/activin/nodal receptor signaling was restricted after SMAD4 knockdown. These results suggest that TGFbeta/activin/nodal signaling supports the undifferentiated phenotype of hESC by suppressing BMP activity. During long-term culture, SMAD4 knockdown cell populations became less stable and more permissive to neural induction, a situation that was rescued by re-establishment of SMAD4 expression. These results suggest that SMAD4 is not required for maintenance of the undifferentiated state of hESC, but rather to stabilize that state.
Department of Biomedical Science, Centre for Stem Cell Biology, University of Sheffield, Western Bank, Sheffield, S10 2TN, United Kingdom. stuart.avery@imb.a-star.edu.sg
Stuart
S
Avery
Gaetano
G
Zafarana
Paul J
PJ
Gokhale
Peter W
PW
Andrews
D028341:Activins / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division / Q000235:genetics*; D019070:Cell Lineage / Q000235:genetics*; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D055457:Nodal Protein / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D051901:Smad4 Protein / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000378:metabolism
D055457:Nodal Protein; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D028341:Activins