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Development 2013 Dec 01;14024:4881-9. doi: 10.1242/dev.095844.
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Short-range Wnt5 signaling initiates specification of sea urchin posterior ectoderm.

McIntyre DC , Seay NW , Croce JC , McClay DR .

The border between the posterior ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the ectoderm-endoderm boundary is established before gastrulation, and ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary ectoderm. This signal activates a unique subcircuit of the ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of ectodermal cells, even though all ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border ectoderm.

PubMed ID: 24227654
PMC ID: PMC3848187
Article link: Development
Grant support: [+]

Genes referenced: bmp2 irx4 LOC100887844 LOC105438994 LOC578814 Nk1 nkx1 nodall pax2 pax2l
Antibodies: msp130 Ab2
Morpholinos: LOC105438994 MO1 bmp2 MO1 hbox7 MO2 nodall MO2

References [+] :
Angerer, A BMP pathway regulates cell fate allocation along the sea urchin animal-vegetal embryonic axis. 2000, Pubmed, Echinobase