Hoppler, S. | bioRxiv Science

bioRxiv2024

WNT-mediating TCF/LEF transcription factor gene expression in early human pluripotency and cell lineages differs from the rodent paradigm

Embryonic stem cell research has uncovered different requirements for WNT/{beta}-catenin signalling in human naive pluripotent cells compared to the mouse paradigm. It is therefore important to study WNT/{beta}-catenin signalling directly in models of early human development. Since TCF/LEF factors mediate the regulation of target genes downstream of WNT/{beta}-catenin signalling, we studied the expression and protein localisation of the four TCF/LEF genes by analysing in vitro "snapshots" of human development, leveraging naive and primed pluripotent cells as well as extraembryonic and early embryonic cell lineages. Strikingly, we comprehensively confirm clear differences between mouse and human pluripotent stem cells, suggesting species-specific requirements for WNT signalling that may reflect differences in states of pluripotency. Human naive ES cells express very low TCF7L1, unlike their mouse counterparts. TCF7L2 is robustly expressed in human naive ES-derived trophectoderm cells. In human primed pluripotent stem cells, activation of WNT/{beta}-Catenin signalling is required to induce expression of both TCF7 and LEF1, concomitant with hallmark gastrulation markers. This expression of human TCF/LEF genes benchmarks differential requirements for WNT/{beta}-catenin signalling throughout early human embryo development that requires further investigation.

developmental biology↗

bioRxiv2021

Positive Feedback Regulation of fzd7 Expression Robustly Shapes Wnt Signaling Range in Early Heart Development

Secreted molecules called morphogens govern tissue patterning in a concentration-dependent manner. However, it is still unclear how reproducible patterning can be achieved with diffusing molecules, especially when patterning differentiation of a thin region. Wnt is a morphogen that organizes cardiac development; especially Wnt6 patterns the cardiogenic mesoderm to induce differentiation of a thin pericardium in Xenopus. It is, however, unclear how Wnt6 can pattern such a thin tissue. In this study, we reveal that a Wnt receptor, frizzled7, is expressed in a Wnt-dependent manner in the prospective heart region, and that this receptor-feedback is essential for shaping a steep gradient of Wnt. In addition, the feedback imparts robustness against fluctuations of Wnt ligand production and allows the system to reach a steady state quickly. We also found a Wnt antagonist sFRP1, which is expressed at the opposite side of Wnt source, accumulates on a novel type of heparan sulfate (HS), N-acetyl-rich HS, which is highly presented in the outer of cardiogenic mesoderm, achieving local inhibition of Wnt signaling by restricting sFRP1 spreading. These two intricate regulatory systems restrict Wnt signaling and ensure reproducible patterning of a thin pericardium tissue.

developmental biology↗