Xenopus brain factor-2 controls mesoderm, forebrain and neural crest development

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.Postdoctoral fellowships from Ministerio de Educación y Cultura to JLGS and Banco Bilbao Vizcaya visiting professorship at University of Cambridge to JM are acknowledged. This investigation was supported by grants from FONDECYT (1960910, 7960009 and 3970017), Third World Academy of Sciences, Fundación Andes, Universidad de Chile, CSIC/CONICYT, Dirección General de Investigación Cientı́fica y Técnica (PB93-0181), Comunidad Autónoma of Madrid, EC (contract CHRX-CT94-0692) and by an institutional grant from Fundación Ramón Areces to the Centro de Biologı́a Molecular Severo Ochoa