20-P028 A fatemap of placodes in Xenopus laevis

Pieper, Mareike; Schlosser, Gerhard

doi:10.1016/j.mod.2009.06.861

Cited by 1 publication

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“…Less is known about the mechanisms through which the PPE is established and segregated from the adjacent neural crest. Whether the PPE is derived from a common precursor shared with neural crest (Brugmann and Moody, 2005;Streit, 2007) or is instead a distinct entity with a different origin (Ahrens and Schlosser, 2005;Pieper and Schlosser, 2009;Schlosser, 2008) is currently controversial.…”

Section: Introductionmentioning

confidence: 99%

RIPPLY3 is a retinoic acid-inducible repressor required for setting the borders of the pre-placodal ectoderm

et al. 2012

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SUMMARYRetinoic acid signaling is a major component of the neural posteriorizing process in vertebrate development. Here, we identify a new role for the retinoic acid receptor (RAR) in the anterior of the embryo, where RAR regulates Fgf8 expression and formation of the pre-placodal ectoderm (PPE). RAR2 signaling induces key pre-placodal genes and establishes the posterolateral borders of the PPE. RAR signaling upregulates two important genes, Tbx1 and Ripply3, during early PPE development. In the absence of RIPPLY3, TBX1 is required for the expression of Fgf8 and hence, PPE formation. In the presence of RIPPLY3, TBX1 acts as a transcriptional repressor, and functions to restrict the positional expression of Fgf8, a key regulator of PPE gene expression. These results establish a novel role for RAR as a regulator of spatial patterning of the PPE through Tbx1 and RIPPLY3. Moreover, we demonstrate that Ripply3, acting downstream of RAR signaling, is a key player in establishing boundaries in the PPE. represses the ability of TBX1 to activate reporter gene constructs in vivo and this inhibition depends on the association of RIPPLY3 with its co-repressor GROUCHO and with TBX1. In agreement with our predictions, RIPPLY3 knockdown perturbs the borders of PPE marker expression. These results demonstrate a novel role for RAR in the precise positioning of the PPE boundaries and establish RIPPLY3 as a key factor that demarcates the boundaries of the PPE. MATERIALS AND METHODS Ripply3 alignment and construction of a phylogenetic treeRipply sequences were obtained from Genbank and Uniprot databases (Benson et al., 2008;Uniprot Consortium, 2009), aligned with MAFFT (L-INS-i algorithm) (Katoh et al., 2009;Katoh et al., 2005) and a phylogenetic tree constructed with PROml, version 3.69 (Protein Maximum Likelihood) (Felsenstein, 2005). Default settings were used, global rearrangements (-G) were performed, and the outgroup (-O) was set to amphioxus. The resultant tree was drawn with FigTree (Rambaut, 2007). Conserved domains of the Ripply gene family were visualized with WebLogo (Crooks et al., 2004;Schneider and Stephens, 1990). EmbryosXenopus eggs were fertilized in vitro as described previously (Blumberg et al., 1997;Koide et al., 2001) and embryos staged according to Nieuwkoop and Faber (Nieuwkoop and Faber, 1967). Embryos were maintained in 0.1ϫ MBS until appropriate stages or treated with 1 M agonist (TTNPB) and 1 M antagonist (AGN193109) as described (Arima et al., 2005). MicroinjectionEmbryos were injected bilaterally or unilaterally at the two-cell stage with combinations of gene specific morpholinos (MO), mRNAs and 100 pg/embryo -galactosidase mRNA lineage tracer. MOs used for this study are found in supplementary material Table S1. Control embryos were injected with 20 ng standard control MO: CCT CTT ACC TCA GTT ACA ATT TAT A (GeneTools). The following plasmids were constructed by PCR amplification of the protein-coding regions of the indicated genes and cloning into the expression vector pCDG1: xRARa2.2 (Sharpe, ...

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Section: Introductionmentioning

confidence: 99%