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Dev Biol 2007 May 01;3051:103-19. doi: 10.1016/j.ydbio.2007.01.040.
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The competence of Xenopus blastomeres to produce neural and retinal progeny is repressed by two endo-mesoderm promoting pathways.

Yan B , Moody SA .

Only a subset of cleavage stage blastomeres in the Xenopus embryo is competent to contribute cells to the retina; ventral vegetal blastomeres do not form retina even when provided with neuralizing factors or transplanted to the most retinogenic position of the embryo. These results suggest that endogenous maternal factors in the vegetal region repress the ability of blastomeres to form retina. Herein we provide three lines of evidence that two vegetal-enriched maternal factors (VegT, Vg1), which are known to promote endo-mesodermal fates, negatively regulate which cells are competent to express anterior neural and retinal fates. First, both molecules can repress the ability of dorsal-animal retinogenic blastomeres to form retina, converting the lineage from neural/retinal to non-neural ectodermal and endo-mesodermal fates. Second, reducing the endogenous levels of either factor in dorsal-animal retinogenic blastomeres expands expression of neural/retinal genes and enlarges the retina. The dorsal-animal repression of neural/retinal fates by VegT and Vg1 is likely mediated by Sox17alpha and Derriere but not by XNr1. VegT and Vg1 likely exert their effects on neural/retinal fates through at least partially independent pathways because Notch1 can reverse the effects of VegT and Derriere but not those of Vg1 or XNr1. Third, reduction of endogenous VegT and/or Vg1 in ventral vegetal blastomeres can induce a neural fate, but only allows expression of a retinal fate when both BMP and Wnt signaling pathways are concomitantly repressed.

PubMed ID: 17428460
PMC ID: PMC1892348
Article link: Dev Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: a2m cer1 egr2 en2 foxd4l1.1 gal.2 gdf1 gdf3 irx1 krt70 nodal nodal1 nog notch1 otx2 rax sox17a sox3 tbxt vegt wnt8a
Morpholinos: vegt MO5

Article Images: [+] show captions
References [+] :
Agius, Endodermal Nodal-related signals and mesoderm induction in Xenopus. 2000, Pubmed, Xenbase