Lin, F. et al. Gα12/13 regulate epiboly by inhibiting E-cadherin activity and modulating the actin cytoskeleton. J. Cell Biol. 184, 909-921

Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
The Journal of Cell Biology (Impact Factor: 9.83). 04/2009; 184(6):909-21. DOI: 10.1083/jcb.200805148
Source: PubMed


Epiboly spreads and thins the blastoderm over the yolk cell during zebrafish gastrulation, and involves coordinated movements of several cell layers. Although recent studies have begun to elucidate the processes that underlie these epibolic movements, the cellular and molecular mechanisms involved remain to be fully defined. Here, we show that gastrulae with altered Galpha(12/13) signaling display delayed epibolic movement of the deep cells, abnormal movement of dorsal forerunner cells, and dissociation of cells from the blastoderm, phenocopying e-cadherin mutants. Biochemical and genetic studies indicate that Galpha(12/13) regulate epiboly, in part by associating with the cytoplasmic terminus of E-cadherin, and thereby inhibiting E-cadherin activity and cell adhesion. Furthermore, we demonstrate that Galpha(12/13) modulate epibolic movements of the enveloping layer by regulating actin cytoskeleton organization through a RhoGEF/Rho-dependent pathway. These results provide the first in vivo evidence that Galpha(12/13) regulate epiboly through two distinct mechanisms: limiting E-cadherin activity and modulating the organization of the actin cytoskeleton.

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Available from: Sherry Clendenon, Oct 09, 2015
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    • "The observed cell dissociation in response to excess March8 focused our attention on cadherins, major cell-cell adhesion proteins that have been well studied in Xenopus and zebrafish embryos [3], [14], [38], [39]. Xenopus [9], [10], [11], [12], and zebrafish [4], [5], [6], [7] cadherins are expressed at high levels in the egg and early embryo, and are essential for cleavage, epiboly and gastrulation movements [8], [40], [41]. The essential function of E-cadherin in zebrafish epiboly is most clearly demonstrated in the half baked mutant, which affects the cdh1 locus [6]. "
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    ABSTRACT: March8 is a member of a family of transmembrane E3 ubiquitin ligases that have been studied mostly for their role in the immune system. We find that March8 is expressed in the zebrafish egg and early embryo, suggesting a role in development. Both knock-down and overexpression of March8 leads to abnormal development. The phenotype of zebrafish embryos and Xenopus animal explants overexpressing March8 implicates impairment of cell adhesion as a cause of the effect. In zebrafish embryos and in cultured cells, overexpression of March8 leads to a reduction in the surface levels of E-cadherin, a major cell-cell adhesion molecule. Experiments in cell culture further show that E-cadherin can be ubiquitinated by March8. On the basis of these observations we suggest that March8 functions in the embryo to modulate the strength of cell adhesion by regulating the localization of E-cadherin.
    PLoS ONE 04/2014; 9(4):e94873. DOI:10.1371/journal.pone.0094873 · 3.23 Impact Factor
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    • "E-cadherin adhesion activity is required for epiboly and convergence/extension cell movements during gastrulation (Babb and Marrs, 2004; Kane et al., 2005; Morita and Heisenberg, 2013; Solnica-Krezel, 2006; Song et al., 2013). Ecadherin distribution and trafficking is regulated during gastrulation, particularly in the prechordal plate (the leading edge of the anterior mesendoderm) by critical early developmental signaling pathways, including non-canonical Wnt (Ulrich et al., 2005), heterotrimeric G-protein (Lin et al., 2009) and Pou5f1/Oct4 signaling pathways (Song et al., 2013). "
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    ABSTRACT: Fetal alcohol spectrum disorder (FASD) occurs when pregnant mothers consume alcohol, causing embryonic ethanol exposure and characteristic birth defects that include craniofacial, neural and cardiac defects. Gastrulation is a particularly sensitive developmental stage for teratogen exposure, and zebrafish is an outstanding model to study gastrulation and FASD. Epiboly (spreading blastomere cells over the yolk cell), prechordal plate migration and convergence/extension cell movements are sensitive to early ethanol exposure. Here, experiments are presented that characterize mechanisms of ethanol toxicity on epiboly and gastrulation. Epiboly mechanisms include blastomere radial intercalation cell movements and yolk cell microtubule cytoskeleton pulling the embryo to the vegetal pole. Both of these processes were disrupted by ethanol exposure. Ethanol effects on cell migration also indicated that cell adhesion was affected, which was confirmed by cell aggregation assays. E-cadherin cell adhesion molecule expression was not affected by ethanol exposure, but E-cadherin distribution, which controls epiboly and gastrulation, was changed. E-cadherin was redistributed into cytoplasmic aggregates in blastomeres and dramatically redistributed in the extraembryonic yolk cell. Gene expression microarray analysis was used to identify potential causative factors for early development defects, and expression of the cell adhesion molecule protocadherin-18a (pcdh18a), which controls epiboly, was significantly reduced in ethanol exposed embryos. Injecting pcdh18a synthetic mRNA in ethanol treated embryos partially rescued epiboly cell movements, including enveloping layer cell shape changes. Together, data show that epiboly and gastrulation defects induced by ethanol are multifactorial, and include yolk cell (extraembryonic tissue) microtubule cytoskeleton disruption and blastomere adhesion defects, in part caused by reduced pcdh18a expression.
    Biology Open 10/2013; 2(10):1013-21. DOI:10.1242/bio.20135546 · 2.42 Impact Factor
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    • "In zebrafish, Nodal signaling modulates cortical tension (Krieg et al., 2008), but Nodal signaling is normal in MZspg embryos (Lunde et al., 2004). However, other changes in MZspg may contribute to the adhesion phenotype, like the observed increase in gna12a mRNA levels pre-MBT, which may alter Rho activity and cortical tension or result in increased Galpha12 binding to E-cad, causing inhibition of E-cad adhesive activity (Lin et al., 2009). Interestingly, E-cad may be involved in both adhesion and cortical tension mechanisms (Cavey et al., 2008). "
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    ABSTRACT: Initiation of motile cell behavior in embryonic development occurs during late blastula stages when gastrulation begins. At this stage, the strong adhesion of blastomeres has to be modulated to enable dynamic behavior, similar to epithelial-to-mesenchymal transitions. We show that, in zebrafish maternal and zygotic (MZ)spg embryos mutant for the stem cell transcription factor Pou5f1/Oct4, which are severely delayed in the epiboly gastrulation movement, all blastomeres are defective in E-cadherin (E-cad) endosomal trafficking, and E-cad accumulates at the plasma membrane. We find that Pou5f1-dependent control of EGF expression regulates endosomal E-cad trafficking. EGF receptor may act via modulation of p120 activity. Loss of E-cad dynamics reduces cohesion of cells in reaggregation assays. Quantitative analysis of cell behavior indicates that dynamic E-cad endosomal trafficking is required for epiboly cell movements. We hypothesize that dynamic control of E-cad trafficking is essential to effectively generate new adhesion sites when cells move relative to each other.
    Developmental Cell 03/2013; 24(5):486-501. DOI:10.1016/j.devcel.2013.01.016 · 9.71 Impact Factor
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