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Proc Natl Acad Sci U S A 2014 Nov 25;11147:E5029-38. doi: 10.1073/pnas.1419141111.
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Specific functions of the Wnt signaling system in gene regulatory networks throughout the early sea urchin embryo.

Cui M , Siriwon N , Li E , Davidson EH , Peter IS .

Wnt signaling affects cell-fate specification processes throughout embryonic development. Here we take advantage of the well-studied gene regulatory networks (GRNs) that control pregastrular sea urchin embryogenesis to reveal the gene regulatory functions of the entire Wnt-signaling system. Five wnt genes, three frizzled genes, two secreted frizzled-related protein 1 genes, and two Dickkopf genes are expressed in dynamic spatial patterns in the pregastrular embryo of Strongylocentrotus purpuratus. We present a comprehensive analysis of these genes in each embryonic domain. Total functions of the Wnt-signaling system in regulatory gene expression throughout the embryo were studied by use of the Porcupine inhibitor C59, which interferes with zygotic Wnt ligand secretion. Morpholino-mediated knockdown of each expressed Wnt ligand demonstrated that individual Wnt ligands are functionally distinct, despite their partially overlapping spatial expression. They target specific embryonic domains and affect particular regulatory genes. The sum of the effects of blocking expression of individual wnt genes is shown to equal C59 effects. Remarkably, zygotic Wnt-signaling inputs are required for only three general aspects of embryonic specification: the broad activation of endodermal GRNs, the regional specification of the immediately adjacent stripe of ectoderm, and the restriction of the apical neurogenic domain. All Wnt signaling in this pregastrular embryo is short range (and/or autocrine). Furthermore, we show that the transcriptional drivers of wnt genes execute important specification functions in the embryonic domains targeted by the ligands, thus connecting the expression and function of wnt genes by encoded cross-regulatory interactions within the specific regional GRNs.

PubMed ID: 25385617
PMC ID: PMC4250154
Article link: Proc Natl Acad Sci U S A
Grant support: [+]

Genes referenced: LOC100887844 LOC115919910 porcn
Morpholinos: LOC105438994 MO2 LOC105438994 MO3 evxl MO1 foxa1 MO1 gata6 MO1 hbox7 MO3 porcn MO1 prdm1 MO3 tbxt MO1 wnt1 MO1 wnt16 MO1 wnt4 MO1 wnt4 MO2 wnt8a MO2 wnt8a MO3

References [+] :
Angerer, The evolution of nervous system patterning: insights from sea urchin development. 2011, Pubmed, Echinobase