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PLoS Biol 2009 Feb 03;72:e1000029. doi: 10.1371/journal.pbio.1000029.
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Gene regulatory network interactions in sea urchin endomesoderm induction.

Sethi AJ , Angerer RC , Angerer LM .

A major goal of contemporary studies of embryonic development is to understand large sets of regulatory changes that accompany the phenomenon of embryonic induction. The highly resolved sea urchin pregastrular endomesoderm-gene regulatory network (EM-GRN) provides a unique framework to study the global regulatory interactions underlying endomesoderm induction. Vegetal micromeres of the sea urchin embryo constitute a classic endomesoderm signaling center, whose potential to induce archenteron formation from presumptive ectoderm was demonstrated almost a century ago. In this work, we ectopically activate the primary mesenchyme cell-GRN (PMC-GRN) that operates in micromere progeny by misexpressing the micromere determinant Pmar1 and identify the responding EM-GRN that is induced in animal blastomeres. Using localized loss-of -function analyses in conjunction with expression of endo16, the molecular definition of micromere-dependent endomesoderm specification, we show that the TGFbeta cytokine, ActivinB, is an essential component of this induction in blastomeres that emit this signal, as well as in cells that respond to it. We report that normal pregastrular endomesoderm specification requires activation of the Pmar1-inducible subset of the EM-GRN by the same cytokine, strongly suggesting that early micromere-mediated endomesoderm specification, which regulates timely gastrulation in the sea urchin embryo, is also ActivinB dependent. This study unexpectedly uncovers the existence of an additional uncharacterized micromere signal to endomesoderm progenitors, significantly revising existing models. In one of the first network-level characterizations of an intercellular inductive phenomenon, we describe an important in vivo model of the requirement of ActivinB signaling in the earliest steps of embryonic endomesoderm progenitor specification.

PubMed ID: 19192949
PMC ID: PMC2634790
Article link: PLoS Biol
Grant support: [+]

Species referenced: Echinodermata
Genes referenced: ago1b endo16 evxl foxa1 gata6 gcml LOC100887844 LOC100889251 LOC100893907 LOC115919910 LOC115921237 LOC115925415 LOC115926321 LOC575170 LOC593908 LOC594353 pmar1 prdm1 sox2 tbxt wnt8a znf474
Antibodies: sox2 Ab1
Morpholinos: LOC100147806 MO1 LOC100147806 MO2 dll1 MO2

Article Images: [+] show captions
References [+] :
Abdollahi, Transcriptional network governing the angiogenic switch in human pancreatic cancer. 2007, Pubmed