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ECB-ART-41066
Development 2009 Apr 01;1367:1179-89. doi: 10.1242/dev.032300.
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The sea urchin animal pole domain is a Six3-dependent neurogenic patterning center.

Wei Z , Yaguchi J , Yaguchi S , Angerer RC , Angerer LM .


Abstract
Two major signaling centers have been shown to control patterning of sea urchin embryos. Canonical Wnt signaling in vegetal blastomeres and Nodal signaling in presumptive oral ectoderm are necessary and sufficient to initiate patterning along the primary and secondary axes, respectively. Here we define and characterize a third patterning center, the animal pole domain (APD), which contains neurogenic ectoderm, and can oppose Wnt and Nodal signaling. The regulatory influence of the APD is normally restricted to the animal pole region, but can operate in most cells of the embryo because, in the absence of Wnt and Nodal, the APD expands throughout the embryo. We have identified many constituent APD regulatory genes expressed in the early blastula and have shown that expression of most of them requires Six3 function. Furthermore, Six3 is necessary for the differentiation of diverse cell types in the APD, including the neurogenic animal plate and immediately flanking ectoderm, indicating that it functions at or near the top of several APD gene regulatory networks. Remarkably, it is also sufficient to respecify the fates of cells in the rest of the embryo, generating an embryo consisting of a greatly expanded, but correctly patterned, APD. A fraction of the large group of Six3-dependent regulatory proteins are orthologous to those expressed in the vertebrate forebrain, suggesting that they controlled formation of the early neurogenic domain in the common deuterostome ancestor of echinoderms and vertebrates.

PubMed ID: 19270175
PMC ID: PMC2685935
Article link: Development


Genes referenced: LOC100887844 LOC115919910 LOC115925415 nodall pole six6
Antibodies: gscl Ab1
Morpholinos: nodall MO4 six6 MO1 six6 MO2

References [+] :
Andreazzoli, Xrx1 controls proliferation and neurogenesis in Xenopus anterior neural plate. 2003, Pubmed