Item

Abstract

Mouse embryoid bodies can break their initial symmetry to form a localized expression of germ layer markers that resembles the formation of the anterior-posterior axis in the embryo. Here, we analyze this self-organization in three dimensions by using lightsheet microscopy. Our data shows that the formation of the anterior-posterior axis is characterized by a moving gene expression front of mesendodermal fates that propagates from the boundary on one side of the embryoid body. By developing a three-dimensional computational model of embryoid body self-organization, we show that this spatiotemporal dynamics can be recapitulated by a bi-stable reaction-diffusion mechanism under the influence of signals coming from the boundary. To test this hypothesis we analyze anterior-posterior axis self-organization in embrioid bodies of different size and upon pharmacological inhibition of signaling pathways. In agreement with the model, our data show that the formation of the axis is size-independent and that the velocity of the front is mediated by Wnt and Nodal signaling.