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Nature 2011 May 29;4747353:635-9. doi: 10.1038/nature10100.
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A gene regulatory network controlling the embryonic specification of endoderm.

Specification of endoderm is the prerequisite for gut formation in the embryogenesis of bilaterian organisms. Modern lineage labelling studies have shown that in the sea urchin embryo model system, descendants of the veg1 and veg2 cell lineages produce the endoderm, and that the veg2 lineage also gives rise to mesodermal cell types. It is known that Wnt/β-catenin signalling is required for endoderm specification and Delta/Notch signalling is required for mesoderm specification. Some direct cis-regulatory targets of these signals have been found and various phenomenological patterns of gene expression have been observed in the pre-gastrular endomesoderm. However, no comprehensive, causal explanation of endoderm specification has been conceived for sea urchins, nor for any other deuterostome. Here we propose a model, on the basis of the underlying genomic control system, that provides such an explanation, built at several levels of biological organization. The hardwired core of the control system consists of the cis-regulatory apparatus of endodermal regulatory genes, which determine the relationship between the inputs to which these genes are exposed and their outputs. The architecture of the network circuitry controlling the dynamic process of endoderm specification then explains, at the system level, a sequence of developmental logic operations, which generate the biological process. The control system initiates non-interacting endodermal and mesodermal gene regulatory networks in veg2-derived cells and extinguishes the endodermal gene regulatory network in mesodermal precursors. It also generates a cross-regulatory network that specifies future anterior endoderm in veg2 descendants and institutes a distinct network specifying posterior endoderm in veg1-derived cells. The network model provides an explanatory framework that relates endoderm specification to the genomic regulatory code.

PubMed ID: 21623371
PMC ID: PMC3976212
Article link: Nature
Grant support: [+]

Genes referenced: LOC100887844 LOC115919910 LOC115921237 LOC594353
Morpholinos: LOC373243 MO2 dach1 MO1 evxl MO1 foxa1 MO1 gata6 MO1 hbox7 MO2 hnf1a MO1 myc MO1 notch1 MO1 otx2 MO2 otx2 MO3 sox4 MO1 tbxt MO1 tgif2l MO1

References [+] :
Byrum, Blocking Dishevelled signaling in the noncanonical Wnt pathway in sea urchins disrupts endoderm formation and spiculogenesis, but not secondary mesoderm formation. 2009, Pubmed, Echinobase