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BMC Biol 2010 Nov 30;8:143. doi: 10.1186/1741-7007-8-143.
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Uncoupling of complex regulatory patterning during evolution of larval development in echinoderms.

Yankura KA , Martik ML , Jennings CK , Hinman VF .

BACKGROUND: Conservation of orthologous regulatory gene expression domains, especially along the neuroectodermal anterior-posterior axis, in animals as disparate as flies and vertebrates suggests that common patterning mechanisms have been conserved since the base of Bilateria. The homology of axial patterning is far less clear for the many marine animals that undergo a radical transformation in body plan during metamorphosis. The embryos of these animals are microscopic, feeding within the plankton until they metamorphose into their adult forms. RESULTS: We describe here the localization of 14 transcription factors within the ectoderm during early embryogenesis in Patiria miniata, a sea star with an indirectly developing planktonic bipinnaria larva. We find that the animal-vegetal axis of this very simple embryo is surprisingly well patterned. Furthermore, the patterning that we observe throughout the ectoderm generally corresponds to that of "head/anterior brain" patterning known for hemichordates and vertebrates, which share a common ancestor with the sea star. While we suggest here that aspects of head/anterior brain patterning are generally conserved, we show that another suite of genes involved in retinal determination is absent from the ectoderm of these echinoderms and instead operates within the mesoderm. CONCLUSIONS: Our findings therefore extend, for the first time, evidence of a conserved axial pattering to echinoderm embryos exhibiting maximal indirect development. The dissociation of head/anterior brain patterning from "retinal specification" in echinoderm blastulae might reflect modular changes to a developmental gene regulatory network within the ectoderm that facilitates the evolution of these microscopic larvae.

PubMed ID: 21118544
PMC ID: PMC3002323
Article link: BMC Biol
Grant support: [+]

Species referenced: Echinodermata
Genes referenced: foxd4 foxe3l foxg1 foxj1 gata6 klf13 lhx9l LOC100887844 LOC100893907 Nk1 nkx1 nkx2-1 onecut2 pax6 pole six6 tbr1 unpgl zic1

Article Images: [+] show captions
References [+] :
Aamar, Isolation and expression analysis of foxj1 and foxj1.2 in zebrafish embryos. 2008, Pubmed