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Genesis May 1, 2015; 53 (5): 308-20.

Early neural ectodermal genes are activated by Siamois and Twin during blastula stages.

Klein SL , Moody SA .

BMP signaling distinguishes between neural and non-neural fates by activating epidermis-specific transcription and repressing neural-specific transcription. The neural ectoderm forms after the Organizer secrets antagonists that prevent these BMP-mediated activities. However, it is not known whether neural genes also are transcriptionally activated. Therefore, we tested the ability of nine Organizer transcription factors to ectopically induce the expression of four neural ectodermal genes in epidermal precursors. We found evidence for two pathways: Foxd4 and Sox11 were only induced by Sia and Twn, whereas Gmnn and Zic2 were induced by Sia, Twn, as well as seven other Organizer transcription factors. The induction of Foxd4, Gmnn and Zic2 by Sia/Twn was both non-cell autonomous (requiring an intermediate protein) and cell autonomous (direct), whereas the induction of Sox11 required Foxd4 activity. Because direct induction by Sia/Twn could occur endogenously in the dorsal-equatorial blastula cells that give rise to both the Organizer mesoderm and the neural ectoderm, we knocked down Sia/Twn in those cells. This prevented the blastula expression of Foxd4 and Sox11, demonstrating that Sia/Twn directly activate some neural genes before the separation of the Organizer mesoderm and neural ectoderm lineages.

PubMed ID: 25892704
Article link: Genesis
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: ctnnb1 foxd4l1.1 foxd4l1.2 gmnn hesx1 lhx1 pou3f4 sia1 sia2 sox11 zic2
Morpholinos: foxd4l1.1 MO1 foxd4l1.2 MO1 sia1 MO2 sia2 MO2

Phenotypes: Xla Wt + sia1 MO + sia2 MO (fig.4)

Article Images: [+] show captions