Ayad, N. M. E. | Search bioRxiv

bioRxiv2023

Tissue tension permits β-catenin phosphorylation to drive mesoderm specification in human embryonic stem cells.

The role of morphogenetic forces in cell fate specification is an area of intense interest. Our prior studies suggested that the development of high cell-cell tension in human embryonic stem cells (hESC) colonies permits the Src-mediated phosphorylation of junctional {beta}-catenin that accelerates its release to potentiate Wnt-dependent signaling critical for initiating mesoderm specification. Using an ectopically expressed nonphosphorylatable mutant of {beta}-catenin (Y654F), we now provide direct evidence that impeding tension-dependent Src-mediated {beta}-catenin phosphorylation impedes the expression of Brachyury (T) and the epithelial-to-mesenchymal transition (EMT) necessary for mesoderm specification. Addition of exogenous Wnt3a or inhibiting GSK3{beta} activity rescued mesoderm expression, emphasizing the importance of force dependent Wnt signaling in regulating mechanomorphogenesis. Our work provides a framework for understanding tension-dependent {beta}-catenin/Wnt signaling in the self-organization of tissues during developmental processes including gastrulation.

developmental biology↗

bioRxiv2020

Mechanics regulate human embryonic stem cell self-organization to specify mesoderm

Embryogenesis is directed by morphogens that induce differentiation within a defined tissue geometry. Tissue organization is mediated by cell-cell and cell-extracellular matrix (ECM) adhesions and is modulated by cell tension and tissue-level force. Whether cell tension regulates development by directly influencing morphogen signaling remains unclear. Human embryonic stem cells (hESCs) exhibit an intrinsic capacity for self-organization that motivates their use as a tractable model of early human embryogenesis. We engineered patterned substrates that enhance cell-cell interactions to direct the self-organization of cultured hESCs into "gastrulation-like" nodes. Tissue geometries that generate local nodes of high cell-cell tension and induce these self-organized tissue nodes drive BMP4-dependent gastrulation by enhancing phosphorylation and nuclear translocation of {beta}-catenin to promote Wnt signaling and mesoderm specification. The findings underscore the interplay between tissue organization, cell tension, and morphogen-dependent differentiation, and demonstrate that cell- and tissue-level forces directly regulate cell fate specification in early human development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/943076v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@e21aaeorg.highwire.dtl.DTLVardef@45c41forg.highwire.dtl.DTLVardef@4ee902org.highwire.dtl.DTLVardef@a3837d_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG HighlightsO_LISubstrates that enhance cell-cell adhesion promote hESC self-organization C_LIO_LITissue nodes exhibiting high tension are predisposed to gastrulation induction C_LIO_LIColony geometry dictates the localization of tension nodes to specify mesoderm C_LIO_LITension activates {beta}-catenin and stimulates Wnt signaling to induce mesoderm C_LI In BriefEngineered substrates that promote cell-cell adhesion and reconstitute epiblast tissue organization facilitate "gastrulation-like" morphogenesis in cultured hESCs. Tissue geometries that foster localized regions of high cell-cell tension potentiate BMP4-dependent mesoderm specification by enhancing phosphorylation and nuclear translocation of {beta}-catenin to promote Wnt signaling.

developmental biology↗