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BMC Dev Biol 2017 Feb 13;171:4. doi: 10.1186/s12861-017-0145-1.
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Nodal and BMP expression during the transition to pentamery in the sea urchin Heliocidaris erythrogramma: insights into patterning the enigmatic echinoderm body plan.

Koop D , Cisternas P , Morris VB , Strbenac D , Yang JY , Wray GA , Byrne M .

BACKGROUND: The molecular mechanisms underlying the development of the unusual echinoderm pentameral body plan and their likeness to mechanisms underlying the development of the bilateral plans of other deuterostomes are of interest in tracing body plan evolution. In this first study of the spatial expression of genes associated with Nodal and BMP2/4 signalling during the transition to pentamery in sea urchins, we investigate Heliocidaris erythrogramma, a species that provides access to the developing adult rudiment within days of fertilization. RESULTS: BMP2/4, and the putative downstream genes, Six1/2, Eya, Tbx2/3 and Msx were expressed in the earliest morphological manifestation of pentamery during development, the five hydrocoele lobes. The formation of the vestibular ectoderm, the specialized region overlying the left coelom that forms adult ectoderm, involved the expression of putative Nodal target genes Chordin, Gsc and BMP2/4 and putative BMP2/4 target genes Dlx, Msx and Tbx. The expression of Nodal, Lefty and Pitx2 in the right ectoderm, and Pitx2 in the right coelom, was as previously observed in other sea urchins. CONCLUSION: That genes associated with Nodal and BMP2/4 signalling are expressed in the hydrocoele lobes, indicates that they have a role in the developmental transition to pentamery, contributing to our understanding of how the most unusual body plan in the Bilateria may have evolved. We suggest that the Nodal and BMP2/4 signalling cascades might have been duplicated or split during the evolution to pentamery.

PubMed ID: 28193178
PMC ID: PMC5307799
Article link: BMC Dev Biol

Species referenced: Echinodermata Heliocidaris erythrogramma
Genes referenced: bmp2 chrd dlxl eya1 gscl lefty1 LOC100887844 LOC115918707 msx1 nodall pitx2 six1 tbx2

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References [+] :
Angerer, The evolution of nervous system patterning: insights from sea urchin development. 2011, Pubmed, Echinobase