Gα12/13 regulate epiboly by inhibiting E-cadherin activity and modulating the actin cytoskeleton

Abstract

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 Gα12/13 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 Gα12/13 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 Gα12/13 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 Gα12/13 regulate epiboly through two distinct mechanisms: limiting E-cadherin activity and modulating the organization of the actin cytoskeleton.

S1pr2/Gα13 signaling controls myocardial migration by regulating endoderm convergence

“…Capped mRNA was synthesized using the mMessage mMachine Kit (Ambion). The RNAs encoding the following genes were used: gna13a (100 pg) and GNA13 (100 pg) (Lin et al, 2005); the RGS domain of PDZ RhoGEF (arhgef11RGS) (500 pg) or a dominant-negative mutant Arhgef11 lacking the DHPH domain (arhgef11DDHPH) (500 pg) (Panizzi et al, 2007;Lin et al, 2009); s1pr2/mil (200 pg) (Osborne et al, 2008); and sox32 (400 pg) (Stafford et al, 2006). The previously validated morpholino antisense oligonucleotides (MOs) targeting the following genes were used: gna12 (4 ng), gna13a and gna13b (2 ng each) (Lin et al, 2005), and s1pr2/mil (15 ng) (Kawahara et al, 2009).…”

Gpr125 modulates Dishevelled distribution and planar cell polarity signaling

“…As gastrulation movements are sensitive to both elevated and reduced levels of their regulators (Wallingford et al, 2000;Jessen et al, 2002;Marlow et al, 2002;Carreira-Barbosa et al, 2003;Zeng et al, 2007;Lin et al, 2009), we investigated Gpr125 function through both gain-and loss-of-function approaches. Microinjection of synthetic gpr125 RNA into wild-type zygotes caused dosedependent shortening of the AP axis and synophthalmia or cyclopia ( Fig.…”

Disruption of blastomeric F-actin: a potential early biomarker of developmental toxicity in zebrafish

“…In parallel with this effort are those to develop bioassay systems that are fast, inexpensive, and can be carried out in a high-throughput manner. Actin depolymerization by cytochalasin B [8] and blebbistatin, a myosin 2 inhibitor [9], and alteration of Gα 12/13 signaling [20] have been shown to disrupt zebrafish gastrulation by interfering with epiboly. However, the consequences of such embryonic disruption and correlation to subsequent development have not been detailed.…”

“…Similarly, an abnormal cytoskeleton contributes to epibolic delay in Pou5fl-deficient zebrafish embryos [19]. Membrane proteins, Gα 12 and Gα 13 , also regulate epiboly by promoting actin microfilament assembly through a Rho guanine nucleotide exchange factor (GEF)-dependent signaling pathway that appears to modulate epiboly during zebrafish gastrulation [20]. Eps8 (EGF receptor pathway substrate 8) [21], which directly binds actin has been hypothesized to regulate actin filament dynamics in vitro by promoting the capping of actin [22].…”