Calvary, L. | bioRxiv Science

bioRxiv2024

Tricellular junction recruitment of the Wave regulatory complex by Sidekick and Lar induces protrusive activity resolving cell intercalation

Cell intercalation, a fundamental morphogenetic process characterized by the exchange of neighboring cells, plays a pivotal role in epithelial tissue development. While the initiation of new junctions remains poorly understood, recent research indicates the involvement of tricellular junction actors. In this study, we explore the contribution of the WAVE regulatory complex (WRC), a critical regulator of branched F-Actin generation, in tissue elongation and cell intercalation within the Drosophila ovarian follicular epithelium. WRC localizes at tricellular junctions, where it orchestrates the generation of highly dynamic protrusions emanating from one cell and extending between the bicellular junctions of neighboring cells. This protrusive activity is essential for the initiation of new junctions in cells located at the extremities of these junctions. Furthermore, our findings indicate that WRC recruitment at tricellular junctions is a redundant process, involving the cooperative action of the two transmembrane proteins Sidekick and Lar. Disruption of this recruitment impairs protrusive activity, cell intercalation resolution, and tissue elongation, thereby mechanistically bridging molecular, cellular and tissular scales. Consequently, this elucidates a critical mechanism underlying epithelial morphogenesis through actin polymerization at tricellular junctions.

cell biology↗

bioRxiv2024

Application of tissue-scale tension to avian epithelia in vivo to study multiscale mechanical properties and inter-germ layer coupling

As cross-disciplinary approaches drawing from physics and mechanics have increasingly influenced our understanding of morphogenesis, the tools available to measure and perturb physical aspects of embryonic development have expanded as well. However, it remains a challenge to measure mechanical properties and apply exogenous tissue-scale forces in vivo, particularly for epithelia. Exploiting the size and accessibility of the developing chick embryo, here we describe a simple technique to quantitatively apply exogenous forces on the order of 1-100 N to the endodermal epithelium. To demonstrate the utility of this approach, we performed a series of proof-of-concept experiments that reveal fundamental and unexpected mechanical behaviors in the early chick embryo, including mechanotype heterogeneity among cells of the midgut endoderm, complex non-cell autonomous effects of actin disruption, and a high degree of mechanical coupling between the endoderm and adjacent paraxial mesoderm. To illustrate the broader utility of this method, we determined that forces on the order of 10 N are sufficient to unzip the neural tube during primary neurulation. Together, these findings provide basic insights into the mechanics of embryonic epithelia in vivo in the early avian embryo, and provide a useful tool for future investigations of how morphogenesis is influenced by mechanical factors. Graphical AbstractO_ST_ABSSummary StatementC_ST_ABS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/588089v2_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@7f0d90org.highwire.dtl.DTLVardef@153a4b0org.highwire.dtl.DTLVardef@614051org.highwire.dtl.DTLVardef@c5b432_HPS_FORMAT_FIGEXP M_FIG C_FIG A simple approach is devised to quantitatively apply tension to epithelia in vivo, and used to study endoderm mechanics in the deeloping chick embryo.

developmental biology↗