Abstract
Spatial cellular organization is fundamental for embryogenesis. Remarkably, coculturing embryonic stem cells (ESCs) and trophoblast stem cells (TSCs) recapitulates this process, forming embryo-like structures. However, mechanisms driving ESC-TSC interaction remain elusive. We describe specialized ESC-generated cytonemes that react to TSC-secreted Wnts. Cytoneme formation and length are controlled by actin, intracellular calcium stores, and components of the Wnt pathway. ESC cytonemes select self-renewal-promoting Wnts via crosstalk between Wnt receptors, activation of ionotropic glutamate receptors (iGluRs), and localized calcium transients. This crosstalk orchestrates Wnt signaling, ESC polarization, ESC-TSC pairing, and consequently synthetic embryogenesis. Our results uncover ESC-TSC contact-mediated signaling, reminiscent of the glutamatergic neuronal synapse, inducing spatial self-organization and embryonic cell specification.
Highlights
Spatial cellular organization is fundamental for embryogenesis
We describe embryonic stem cells (ESCs)-generated cytonemes that react to self-renewal–promoting Wnt ligands secreted by trophoblast stem cells (TSCs)
ESCs incubated with TSCs pretreated with inhibitor of Wnt production-2 (IWP2), a small molecule that blocks the secretion of Wnt ligands [22], for 24 h significantly reduced the magnitude of activation, similar to that of ESCs cultured alone (Fig. 1C and SI Appendix, Fig. S1B)
Summary
ESCs and TSCs possess the ability to self-sort and organize when cultured together to generate embryonic structures [2,3,4]. ESCs incubated with TSCs pretreated with inhibitor of Wnt production-2 (IWP2), a small molecule that blocks the secretion of Wnt ligands [22], for 24 h significantly reduced the magnitude of activation, similar to that of ESCs cultured alone (Fig. 1C and SI Appendix, Fig. S1B) These results indicate that TSCs produce Wnt ligands that are received by ESCs to activate the Wnt/ β-catenin pathway. We generated a double knock-out (dKO) of the Wnt coreceptors LRP5 and LRP6 in ESCs (LRP5/6dKO) and observed that the transient contact between cytonemes and TSCs was unaffected These ESCs had a significantly reduced ability to establish stable contacts with TSCs, to the ESC interaction with IWP2-pretreated TSCs (Fig. 1B). To study the specificity of these cytonemes for Wnt ligands, we covalently immobilized purified Wnts to microbeads and investigated the cytoneme-bead interactions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
