Lysophosphatidic acid signaling controls cortical actin assembly and cytoarchitecture in Xenopus embryos

Abstract

The mechanisms that control shape and rigidity of early embryos are not well understood, and yet are required for all embryonic processes to take place. In the Xenopus blastula, the cortical actin network in each blastomere is required for the maintenance of overall embryonic shape and rigidity. However, the mechanism whereby each cell assembles the appropriate pattern and number of actin filament bundles is not known. The existence of a similar network in each blastomere suggests two possibilities: cellautonomous inheritance of instructions from the egg; or mutual intercellular signaling mediated by cell contact or diffusible signals. We show that intercellular signaling is required for the correct pattern of cortical actin assembly in Xenopus embryos, and that lysophosphatidic acid (LPA) and its receptors, corresponding to LPA 1 and LPA 2 in mammals, are both necessary and sufficient for this function.

The lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) receptor gene families: cloning and comparative expression analysis in Xenopus laevis

“…LPA expression suggests housekeeping functions in Xenopus LPA1 and LPA2 have already been cloned in Xenopus (Kimura et al 2001;Lloyd et al 2005). Our results indicate a wider distribution for LPA1.1 and LPA1.2 in adult frog than previously published, but confirm that these transcripts are strongly expressed in the nervous system and ovary (oocytes) (Kimura et al 2001).…”

“…Although the sequences for several LPA/S1P receptors were available in databases, we cloned cDNAs for 8 of these receptors by in silico analysis, due to the increased coverage of ESTs and the X. tropicalis genomic DNA sequencing projects. In particular we identified sequences for X. tropicalis LPA3 and S1P3 that previous studies failed to identify (Lloyd et al 2005;Ohuchi et al 2008). Bioinformatics analysis indicated that all the sequences display the characteristic extracellular N terminus and the 7 transmembrane domains (TM) of these receptors which are located at the same position to the human orthologous sequences.…”

“…previously published (Kimura et al 2001;Lloyd et al 2005). For the other receptors, X. laevis or X. tropicalis ESTs were identified and alignments of these sequences were performed to generate the consensus but incomplete sequence of their cDNA.…”

“…Xenopus laevis LPA1.1 and LPA1.2 and Xenopus tropicalis LPA2 receptors have already been cloned (Kimura et al 2001;Lloyd et al 2005). Although the sequences for several LPA/S1P receptors were available in databases, we cloned cDNAs for 8 of these receptors by in silico analysis, due to the increased coverage of ESTs and the X. tropicalis genomic DNA sequencing projects.…”

G-protein-coupled signals control cortical actin assembly by controlling cadherin expression in the earlyXenopusembryo

“…Cells that are dividing in vivo, or dissociated in calcium-and magnesium-free saline, or depleted of C-cadherin, all lose their dense cortical actin network, but retain a sparse network, even in the absence of cadherin on the cell surface (Fig. 2) (see also Lloyd et al, 2005). This sparse network is clearly cadherin-independent and is independent of the dense network.…”