Regulation of gastrulation movements by emergent cell and tissue interactions

Abstract

It is during gastrulation that the primordial germ layers are specified, embryonic axes become morphologically manifest, and the embryonic body plan begins to take shape. As morphogenetic movements push and pull nascent tissues into position within the gastrula, new interactions are established between neighboring cells and tissues. These interactions represent an emergent property within gastrulating embryos, and serve to regulate and promote ensuing morphogenesis that establishes the next set of cell/tissue contacts, and so on. Several recent studies demonstrate the critical roles of such interactions during gastrulation, including those between germ layers, along embryonic axes, and at tissue boundaries. Emergent tissue interactions result from - and result in - morphogen signaling, cell contacts, and mechanical forces within the gastrula. Together, these comprise a dynamic and complex regulatory cascade that drives gastrulation morphogenesis.

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

“…Highmagnification spinning disc confocal imaging showed that the hESCs collectively migrated to these nodes and further revealed that many ingressed basally upon reaching the node to ultimately assemble into a second cellular layer that expressed the mesoderm marker T(brachyury) ( Figure 1C). This cellular behavior is highly reminiscent of gastrulation, wherein cells of the developing epiblast collectively migrate towards the midline and ingress to form a secondary transient structure called the primitive streak, which gives rise to the mesoderm and endoderm germ layers (Shahbazi et al, 2019;Shahbazi and Zernicka-Goetz, 2018;Simunovic and Brivanlou, 2017;Voiculescu et al, 2014;Williams and Solnica-Krezel, 2017). Analogous to the embryonic primitive streak that expands as gastrulation progresses, these "gastrulation-like" nodes in the hESC colonies similarly continued to expand between 24 and 48 hours post-BMP4-stimulation ( Figure 1E).…”

Oscillatory cortical forces promote three dimensional cell intercalations that shape the mandibular arch

“…4,5). As in an unstable foam 58,59 , mesenchymal cells exhibited a broad distribution of cell faces (7)(8)(9)(10)(11)(12)(13)(14) with relatively few neighbours in the mid-portion of the mandibular arch ( Fig. 2A,B, Supplementary Fig.…”

“…Most of the recognised principles of morphogenesis concern mechanisms that shape sheets of embryonic tissue [1][2][3][4][5][6][7][8][9][10][11][12][13] . In particular, exchange of cell neighbours is central to tissue shape change in two dimensions (2D) and involves a limited number of transient multicellular configurations including tetrads (T1 exchange) and rosettes.…”

Mechanistic insights from the LHX1‐driven molecular network in building the embryonic head

“…During gastrulation, cells in the posterior part of the epiblast contribute to the primitive streak from which cells are allocated to different mesoderm and endoderm lineages as they ingress through the primitive streak (Arnold & Robertson, 2009). At the completion of gastrulation, three germ layers are formed: the ectoderm for the skin and nervous system; the mesoderm for the skeleton, muscles and the circulatory system, and the endoderm for the gut and epithelial tissues (Williams & Solnica-Krezel, 2017). In situ hybridization has been used to visualize Lhx1 expression in different tissues during gastrulation of the mouse embryo.…”