Mechanochemical actuators of embryonic epithelial contractility

Abstract

Spatiotemporal regulation of cell contractility coordinates cell shape change to construct tissue architecture and ultimately directs the morphology and function of the organism. Here we show that contractility responses to spatially and temporally controlled chemical stimuli depend much more strongly on intercellular mechanical connections than on biochemical cues in both stimulated tissues and adjacent cells. We investigate how the cell contractility is triggered within an embryonic epithelial sheet by local ligand stimulation and coordinates a long-range contraction response. Our custom microfluidic control system allows spatiotemporally controlled stimulation with extracellular ATP, which results in locally distinct contractility followed by mechanical strain pattern formation. The stimulationresponse circuit exposed here provides a better understanding of how morphogenetic processes integrate responses to stimulation and how intercellular responses are transmitted across multiple cells. These findings may enable one to create a biological actuator that actively drives morphogenesis.microfluidics | multicellular | mechanotransduction | signaling P hysiological control systems have evolved diverse strategies to sense the environment, transduce signals, and actuate contractile responses. One such strategy involves the actuation of nonmuscle cell contractility to drive a wide range of developmental processes as well as normal physiological and pathological disease states (1-5). The contractile behaviors of cells and their interactions in multicellular arrays are not only critical in shaping and guiding tissue formation (e.g., epithelial folding) for the successful outcome of development programs (6, 7), but also play a major role in the pathology of tumor growth, the invasionmetastasis cascade, wound healing, and tissue regeneration (8,9).From a signaling standpoint, embryonic development is a dynamic process where cells interact and coordinate force generation as their identities are patterned by spatiotemporally applied chemical stimuli. There has been considerable debate over the effectiveness of intra-versus intercellular signaling during development (10, 11); nevertheless, the cell-cell signaling and the coordination of a variety of multicellular responses are known to be mediated by gap-junction-dependent intercellular communication (12, 13). However, recent findings from studies of cell mechanics indicate that mechanical cues can be as potent as chemical factors in directing cell differentiation and behaviors and suggest a role in modulating signal transduction pathways (14, 15). Less clear is whether signal transduction can be modulated by mechanical connections during morphogenesis. Results and DiscussionTo investigate the complex integrated response of a multicellular system and investigate the mechanochemical response and actuation, we cultured an intact epithelial sheet adhered to a fibronectin extracellular matrix substrate within a custom microfluidic chamber and exposed a narrow band of 4-5 cells...

Maintenance of the Epithelial Barrier and Remodeling of Cell-Cell Junctions during Cytokinesis

“…First, embryos treated with calyculin A exhibited a ~2-fold increase in vinculin-3×GFP recruitment to junctions, while the intensity of E-cad-3xmCherry was unchanged (Figure S2E). Second, upon addition of ATP, which also increases contractility [39, 40], the embryo exhibited contraction within 60 s and a significant increase (~3-fold) in the intensity of vinculin-3xGFP at junctions within minutes (Figure S2F). Together, these results suggest that elevated tension reinforces AJs connected to the contractile ring by increasing the stability of individual AJ proteins and recruiting vinculin to the cleavage furrow.…”

Distinct intracellular Ca2+ dynamics regulate apical constriction and differentially contribute to neural tube closure

“…This result suggests that, at the concentrations used, these inhibitors selectively affected the active Ca 2+ fluctuations, and therefore, that the active Ca 2+ signaling is required for NTC. During Xenopus gastrulation, a purinergic receptor (Corriden and Insel, 2010;Schwiebert and Zsembery, 2003) for extracellular ATP (eATP) is required for frequent Ca 2+ elevations (Shindo et al, 2010;, and early ectodermal cells respond to eATP causing transient contractions of their apical side (Kim et al, 2014). To examine the possibility that eATP is involved in Ca 2+ fluctuations in the NP, we exhausted the eATP by overexpressing Xenopus ectonucleoside triphosphate diphosphohydrolase 1 (ENTPDase1) (Massé et al, 2007).…”

Spatiotemporally Controlled Mechanical Cues Drive Progenitor Mesenchymal-to-Epithelial Transition Enabling Proper Heart Formation and Function

“…To determine whether mechanical changes in the HFR coincide with MET we tracked tissue movements of the embryo’s ventral anterior surface from late neurula stage (stage 17) using a custom image analysis program [30](Figure 4A; Movie S3). Rather than elongate anteroposteriorly at a constant rate like dorsal tissues, the HFR elongates in a complex manner (Figure 4B), initially shortening and then elongating (Figure 4C).…”