The Rho-Rock-Myosin signaling axis determines cell-cell integrity of self-renewing pluripotent stem cells.
BACKGROUND
Embryonic stem (ES) cells self-renew as coherent colonies in which cells maintain tight cell-cell contact. Although intercellular communications are essential to establish the basis of cell-specific identity, molecular mechanisms underlying intrinsic cell-cell interactions in ES cells at the signaling level remain underexplored.


RESULTS
Here we show that endogenous Rho signaling is required for the maintenance of cell-cell contacts in ES cells. siRNA-mediated loss of function experiments demonstrated that Rock, a major effector kinase downstream of Rho, played a key role in the formation of cell-cell junctional assemblies through regulation of myosin II by controlling a myosin light chain phosphatase. Chemical engineering of this signaling axis by a Rock-specific inhibitor revealed that cell-cell adhesion was reversibly controllable and dispensable for self-renewal of mouse ES cells as confirmed by chimera assay. Furthermore, a novel culture system combining a single synthetic matrix, defined medium, and the Rock inhibitor fully warranted human ES cell self-renewal independent of animal-derived matrices, tight cell contacts, or fibroblastic niche-forming cells as determined by teratoma formation assay.


CONCLUSIONS
These findings demonstrate an essential role of the Rho-Rock-Myosin signaling axis for the regulation of basic cell-cell communications in both mouse and human ES cells, and would contribute to advance in medically compatible xeno-free environments for human pluripotent stem cells.
Harb
Nicole
N
Department of Biochemistry, University of California Riverside, Riverside, California, United States of America.
Archer
Trevor K
TK
Sato
Noboru
N
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D024462:Myosin Type II / Q000502:physiology*; D039904:Pluripotent Stem Cells / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D054460:rho-Associated Kinases / Q000502:physiology*
D034741:RNA, Small Interfering; D054460:rho-Associated Kinases; D024462:Myosin Type II