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PLoS One January 1, 2012; 7 (7): e41782.

Foxi2 is an animally localized maternal mRNA in Xenopus, and an activator of the zygotic ectoderm activator Foxi1e.

Cha SW , McAdams M , Kormish J , Wylie C , Kofron M .

Foxi1e is a zygotic transcription factor that is essential for the expression of early ectodermal genes. It is expressed in a highly specific pattern, only in the deep cell layers of the animal hemisphere, and in a mosaic pattern in which expressing cells are interspersed with non-expressing cells. Previous work has shown that several signals in the blastula control this expression pattern, including nodals, the TGFβ family member Vg1, and Notch. However, these are all inhibitory, which raises the question of what activates Foxi1e. In this work, we show that a related Forkhead family protein, Foxi2, is a maternal activator of Foxi1e. Foxi2 mRNA is maternally encoded, and highly enriched in animal hemisphere cells of the blastula. ChIP assays show that it acts directly on upstream regulatory elements of Foxi1e. Its effect is specific, since animal cells depleted of Foxi2 are able to respond normally to mesoderm inducing signals from vegetal cells. Foxi2 thus acts as a link between the oocyte and the early pathway to ectoderm, in a similar fashion to the vegetally localized VegT acts to initiate endoderm and mesoderm formation.

PubMed ID: 22848601
PMC ID: PMC3407068
Article link: PLoS One
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: cad cald1 cdh1 cer1 dvl2 foxi1 foxi2 foxj1.2 gdf1 krt12.4 lhx5 maml1 mmut myc nodal nodal1 notch1 sox17a sox2 tbxt vegt

Article Images: [+] show captions
References [+] :
Birsoy, Vg 1 is an essential signaling molecule in Xenopus development. 2005, Pubmed, Xenbase