XB-ART-47881PLoS One 2013 Jan 01;89:e73646. doi: 10.1371/journal.pone.0073646.
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Breakage of bilateral symmetry in amphibian embryos depends on the development of a ciliated epithelium at the gastrocoel roof during early neurulation. Motile cilia at the gastrocoel roof plate (GRP) give rise to leftward flow of extracellular fluids. Flow is required for asymmetric gene expression and organ morphogenesis. Wnt signaling has previously been involved in two steps, Wnt/ß-catenin mediated induction of Foxj1, a regulator of motile cilia, and Wnt/planar cell polarity (PCP) dependent cilia polarization to the posterior pole of cells. We have studied Wnt11b in the context of laterality determination, as this ligand was reported to activate canonical and non-canonical Wnt signaling. Wnt11b was found to be expressed in the so-called superficial mesoderm (SM), from which the GRP derives. Surprisingly, Foxj1 was only marginally affected in loss-of-function experiments, indicating that another ligand acts in this early step of laterality specification. Wnt11b was required, however, for polarization of GRP cilia and GRP morphogenesis, in line with the known function of Wnt/PCP in cilia-driven leftward flow. In addition Xnr1 and Coco expression in the lateral-most GRP cells, which sense flow and generate the first asymmetric signal, was attenuated in morphants, involving Wnt signaling in yet another process related to symmetry breakage in Xenopus.
PubMed ID: 24058481
PMC ID: PMC3772795
Article link: PLoS One
Species referenced: Xenopus laevis
Genes referenced: actl6a dand5 foxj1 foxj1.2 fzd8 nodal1 nodal3.1 pitx2 wnt11b
Morpholinos: fzd8 MO3 wnt11b MO2
Phenotypes: Xla Wt + fzd8 MO (Fig. S1 F, G)
Article Images: [+] show captions
References [+] :
Adams, Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates. 2006, Pubmed, Xenbase