Expression is then lost dorsally, so that by the early neurula stage, Foxi1e expression is confined to the non-neural ectoderm. Throughout its expression, Foxi1e mRNA is enriched in deep, compared to superficial cells of the ectoderm, and is mosaic; with Foxi1eexpressing cells interspersed with non-expressing cells. Both long and short range signals control the complex expression pattern of Foxi1e. Loss of signaling through the Notch pathway, the nodals downstream of VegT, or through the maternal TGF-b family member Vg1, all cause up-regulation of Foxi1e mRNA, and loss of its mosaic pattern of expression. However, expression does not spread into the superficial cells, nor into the vegetal hemisphere. Clearly there are more controls remaining to be identified, particularly as all of the signals so far Niraparib PARP inhibitor identified in the blastula that control expression of Foxi1e are repressors. This raises the major question of what activates its expression in the animal hemisphere. We hypothesized that the final expression pattern of Foxi1e is determined by a combination of maternally encoded activators and regional repressors in the blastula. To test this, and to identify putative maternal activators of Foxi1e, we analyzed the 5 kb upstream sequence of Xenopus tropicalis Foxi1e from the JGI sequencing project, cloned and sequenced the 3.5 kb upstream sequence of the Xenopus laevis Foxi1e gene, and compared and scanned the sequences for common transcription factor binding sites. We then assayed EST databases for candidate transcription factors that are maternal, and whose mRNAs are concentrated in the animal hemisphere of the oocyte, and are therefore inherited at highest concentration by animal cells. We report here that another Forkhead family member, Foxi2, whose mRNA is inherited from the egg, is highly enriched in animal cells of the blastula, and is an essential activator of Foxi1e. Foxi2 thus provides the link between the maternal mRNA stockpile and the formation of the ectoderm, as does VegT for the endoderm. Forkhead genes, originally identified in Drosophila, are represented in the genomes of animal species, from yeast to man. The DNA-binding Forkhead domain is highly conserved, but there is wide sequence divergence outside this domain, giving rise to 35 families of Fox genes in humans and mice. Fox genes play essential roles in development and differentiation, the immune system, the cell cycle and cancer, in species longevity, and metabolism. Mutations in Fox genes cause many human congenital disorders. The Foxi class is still poorly understood. So far only identified in deutostomes, expression patterns, and some functional data have been published for Ciona, Xenopus, Zebrafish, and mouse. All Foxi genes for which expression patterns have been published show some expression in the ectoderm, as well as other tissues, although early expression patterns corresponding to the times described here for Xenopus have not been well-studied. In the mouse and Zebrafish, Foxi1 is expressed in the otic placodes and structures derived from them, and mutations of Foxi1 in both species cause defects in sensory structures derived from the otic placodes. Foxi2 in the mouse is also expressed in ectodermal structures, including olfactory epithelium, whiskers, dental epithelium and otic placode. Foxi3 in the mouse is expressed in an ectodermal region defined as pan-placodal, as well as hair follicles and dental epithelium. Furthermore, it has recently been shown that the loss of hair and teeth in Mexican and Peruvan hairless dogs is caused by a mutation in the Foxi3 gene, confirming a role for this gene in ectodermal differentiation. In Zebrafish, Foxi3a and b are expressed in early ectoderm.