title: Foxi2 is an animally localized maternal mRNA in Xenopus, and an activator of the zygotic ectoderm activator Foxi1e.
abstract: 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.
authors: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America.
authors: Sang-Wook
authors: SW
authors: Cha
authors: Meredith
authors: M
authors: McAdams
authors: Jay
authors: J
authors: Kormish
authors: Christopher
authors: C
authors: Wylie
authors: Matthew
authors: M
authors: Kofron
mesh_terms: D000818:Animals; D001483:Base Sequence; D036703:Blastula / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D004475:Ectoderm / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D021381:Protein Transport; D023121:RNA, Messenger, Stored / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D015053:Zygote / Q000166:cytology / Q000378:metabolism*
chemical_list: C502563:FOXI1 protein, Xenopus; D051858:Forkhead Transcription Factors; C504435:FoxI2 protein, Xenopus; D023121:RNA, Messenger, Stored; D020825:T-Box Domain Proteins; D014157:Transcription Factors; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins