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Development 2015 Jan 01;1421:207-17. doi: 10.1242/dev.113043.
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Dose-dependent nuclear β-catenin response segregates endomesoderm along the sea star primary axis.

McCauley BS , Akyar E , Saad HR , Hinman VF .

In many invertebrates, the nuclearization of β-catenin at one pole of the embryo initiates endomesoderm specification. An intriguing possibility is that a gradient of nuclear β-catenin (nβ-catenin), similar to that operating in vertebrate neural tube patterning, functions to distinguish cell fates in invertebrates. To test this hypothesis, we determined the function of nβ-catenin during the early development of the sea star, which undergoes a basal deuterostomal mode of embryogenesis. We show that low levels of nβ-catenin activity initiate bra, which is expressed in the future posterior endoderm-fated territory; intermediate levels are required for expression of foxa and gata4/5/6, which are later restricted to the endoderm; and activation of ets1 and erg in the mesoderm-fated territory requires the highest nβ-catenin activity. Transcription factors acting downstream of high nβ-catenin segregate the endoderm/mesoderm boundary, which is further reinforced by Delta/Notch signaling. Significantly, therefore, in sea stars, endomesoderm segregation arises through transcriptional responses to levels of nβ-catenin activity. Here, we describe the first empirical evidence of a dose-dependent response to a dynamic spatiotemporal nβ-catenin activity that patterns cell fates along the primary axis in an invertebrate.

PubMed ID: 25516976
PMC ID: PMC4299145
Article link: Development
Grant support: [+]

Genes referenced: erg ets1 foxa1 LOC100887844 LOC115919910 LOC115921237 LOC594353 pole tbxt
Morpholinos: ets1 MO2 foxa1 MO2 gata6 MO2

References [+] :
Chan, Developmental gene regulatory networks in the zebrafish embryo. 2009, Pubmed