Nodal signaling regulates endodermal cell motility and actin dynamics via Rac1 and Prex1

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
The Journal of Cell Biology (Impact Factor: 9.83). 09/2012; 198(5):941-52. DOI: 10.1083/jcb.201203012
Source: PubMed

ABSTRACT Embryo morphogenesis is driven by dynamic cell behaviors, including migration, that are coordinated with fate specification and differentiation, but how such coordination is achieved remains poorly understood. During zebrafish gastrulation, endodermal cells sequentially exhibit first random, nonpersistent migration followed by oriented, persistent migration and finally collective migration. Using a novel transgenic line that labels the endodermal actin cytoskeleton, we found that these stage-dependent changes in migratory behavior correlated with changes in actin dynamics. The dynamic actin and random motility exhibited during early gastrulation were dependent on both Nodal and Rac1 signaling. We further identified the Rac-specific guanine nucleotide exchange factor Prex1 as a Nodal target and showed that it mediated Nodal-dependent random motility. Reducing Rac1 activity in endodermal cells caused them to bypass the random migration phase and aberrantly contribute to mesodermal tissues. Together, our results reveal a novel role for Nodal signaling in regulating actin dynamics and migration behavior, which are crucial for endodermal morphogenesis and cell fate decisions.

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    • "RESEARCH ARTICLE Cytoskeleton, Month 2015 00:00–00 (doi: 10.1002/cm.21253) V C 2015 Wiley Periodicals, Inc. [Woo et al., 2012] "
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    ABSTRACT: Dynamic changes of cytoplasmic and cortical actin filaments drive various cellular and developmental processes. Although real-time imaging of actin filaments in living cells has been developed, imaging of actin filaments in specific cells of living organisms remains limited, particularly for analysis of gamete formation and early embryonic development. Here, we report production of transgenic zebrafish expressing the C-terminus of Moesin, an actin filament-binding protein, fused with green fluorescent protein or red fluorescent protein (GFP/RFP-MoeC), under the control of a cyclin B1 promoter. GFP/RFP-MoeC was expressed maternally, which labels the cortical actin cytoskeleton of blastula-stage cells. High levels of GFP/RFP fluorescence were detected in the adult ovary and testis. In the ovaries, GFP/RFP-MoeC was expressed in oocytes but not in follicle cells, which allows us to clearly visualize the organization of actin filaments in different stages of the oocyte. Using full-grown oocytes, we revealed dynamic changes of actin columns assembled in the cortical cytoplasm during oocyte maturation. The number of columns slightly decreased in the early period before germinal vesicle breakdown (GVBD) and then significantly decreased at GVBD, followed by recovery after GVBD. Our transgenic fish are useful for analyzing dynamics of actin filaments in oogenesis and early embryogenesis. This article is protected by copyright. All rights reserved. © 2015 Wiley Periodicals, Inc.
    Cytoskeleton 09/2015; DOI:10.1002/cm.21253 · 3.12 Impact Factor
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    • "All transgenic constructs were assembled using entry clones kindly provided by Chi-Bin Chien and Kristen Kwan (University of Utah, USA), unless specified otherwise. A 5′-entry clone containing a sox17 mini-promoter (Woo et al., 2012) was used to express genes specifically in the endoderm. A 5′-entry clone containing an nkx2.5 promoter (Choe et al., 2013) was used to express genes specifically in myocardial cells. "
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    ABSTRACT: Coordination between the endoderm and adjacent cardiac mesoderm is crucial for heart development. We previously showed that myocardial migration is promoted by convergent movement of the endoderm, which itself is controlled by the S1pr2/Gα13 signaling pathway, but it remains unclear how the movements of the two tissues is coordinated. Here, we image live and fixed embryos to follow these movements, revealing previously unappreciated details of strikingly complex and dynamic associations between the endoderm and myocardial precursors. We found that during segmentation the endoderm underwent three distinct phases of movement relative to the midline: rapid convergence, little convergence and slight expansion. During these periods, the myocardial cells exhibited different stage-dependent migratory modes: co-migration with the endoderm, movement from the dorsal to the ventral side of the endoderm (subduction) and migration independent of endoderm convergence. We also found that defects in S1pr2/Gα13-mediated endodermal convergence affected all three modes of myocardial cell migration, probably due to the disruption of fibronectin assembly around the myocardial cells and consequent disorganization of the myocardial epithelium. Moreover, we found that additional cell types within the anterior lateral plate mesoderm (ALPM) also underwent subduction, and that this movement likewise depended on endoderm convergence. Our study delineates for the first time the details of the intricate interplay between the endoderm and ALPM during embryogenesis, highlighting why endoderm movement is essential for heart development, and thus potential underpinnings of congenital heart disease. © 2015. Published by The Company of Biologists Ltd.
    Development 09/2015; 142(17). DOI:10.1242/dev.113944 · 6.46 Impact Factor
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    • "A family of Rho GDIs also negatively regulates Rho GTPases by binding to the GDP-bound form and maintaining it in this inactive state [5]. Rac1, one of the subfamily member of Rho GTPases, plays a pivotal role in many cellular processes including myotube fusion [6], differentiation [7] [8], actin dynamics [9], superoxide production [10] [11], cell movement [12] [13], proliferation [14] [15] [16], apoptosis [17] [18] [19], and gene expression [18, 20–23], as "
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    ABSTRACT: The p104 protein inhibits cellular proliferation when overexpressed in NIH3T3 cells and has been shown to associate with p85α, Grb2, and PLCγ1. In order to isolate other proteins that interact with p104, yeast two-hybrid screening was performed. Rac1 was identified as a binding partner of p104 and the interaction between p104 and Rac1 was confirmed by immunoprecipitation. Using a glutathione S-transferase (GST) pull-down assay with various p104 fragments, the 814-848 amino acid residue at the carboxyl-terminal region of p104 was identified as the key component to interact with Rac1. The CrkII which is involved in the Rac1-mediated cellular response was also found to interact with p104 protein. NIH3T3 cells which overexpressed p104 showed a decrease of Rac1 activity. However, neither the proline-rich domain mutant, which is unable to interact with CrkII, nor the carboxy-terminal deletion mutant could attenuate Rac1 activity. During the differentiation of myoblasts, the amount of p104 protein as well as transcript level was increased. The overexpression of p104 enhanced myotube differentiation, whereas siRNA of p104 reversed this process. In this process, more Rac1 and CrkII were bound to increased p104. Based on these results, we conclude that p104 is involved in muscle cell differentiation by modulating the Rac1 activity.
    The Scientific World Journal 01/2014; 2014:592450. DOI:10.1155/2014/592450 · 1.73 Impact Factor
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