RESUMO
The forkhead type Brain Factor 2 from mouse and chicken help pattern the forebrain, optic vesicle and kidney. We have isolated a Xenopus homolog (Xbf2) and found that during gastrulation it is expressed in the dorsolateral mesoderm, where it helps specify this territory by downregulating BMP-4 and its downstream genes. Indeed, Xbf2 overexpression caused partial axis duplication. Interference with BMP-4 signaling also occurs in isolated animal caps, since Xbf2 induces neural tissue. Within the neurula forebrain, Xbf2 and the related Xbf1 gene are expressed in the contiguous diencephalic and telencephalic territories, respectively, and each gene represses the other. Finally, Xbf2 seems to participate in the control of neural crest migration. Our data suggest that XBF2 interferes with BMP-4 signaling, both in mesoderm and ectoderm.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Mesoderma/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Crista Neural/fisiologia , Prosencéfalo/embriologia , Proteínas de Xenopus , Xenopus/embriologia , Xenopus/metabolismo , Sequência de Aminoácidos , Animais , Clonagem Molecular , Proteínas de Ligação a DNA/metabolismo , Indução Embrionária , Fatores de Transcrição Forkhead , Galactosídeos/metabolismo , Expressão Gênica , Hibridização In Situ , Indóis/metabolismo , Dados de Sequência Molecular , Fatores de Tempo , Proteína 1 Relacionada a TwistRESUMO
The Drosophila homeoproteins Ara and Caup are members of a combination of factors (prepattern) that control the highly localized expression of the proneural genes achaete and scute. We have identified two Xenopus homologs of ara and caup, Xiro1 and Xiro2. Similarly to their Drosophila counterparts, they control the expression of proneural genes and, probably as a consequence, the size of the neural plate. Moreover, Xiro1 and Xiro2 are themselves controlled by noggin and retinoic acid and, similarly to ara and caup, they are overexpressed by expression in Xenopus embryos of the Drosophila cubitus interruptus gene. These and other findings suggest the conservation of at least part of the genetic cascade that regulates proneural genes, and the existence in vertebrates of a prepattern of factors important to control the differentiation of the neural plate.