During blastula and gastrula stages the establishment of anteroposterior (A–P) patterning of the amphibian embryo starts in response to signaling by several groups of secreted molecules. Xenopus anterior neural induction first occurs at blastula stage by bone morphogenetic protein (BMP) antagonists Chordin and Noggin, which are expressed at the dorsal-animal region, and this low-BMP region called the blastula Chordin- and Noggin-expressing (BCNE) center gives rise to anterior neural tissue and is indispensable for brain formation (Kuroda et al. 2004; Ishibashi et al. 2008). At gastrula stage cerberus, which is expressed in the anterior endoderm region and functions as multiantagonists to block transforming growth factor (TGF)-β molecules such as BMPs and nodals and canonical Wnt proteins (Niehrs 2010), is required for head formation (Bouwmeester et al. 1996). Retinoic acid and fibroblast growth factor (FGF) also functions as an important regulatory signaling for A–P patterning, and blockade of FGF signaling downregulates the expression of members of the RAR (retinoic acid receptor) signaling pathway, resulting in anteriorization of Xenopus embryos (Tannahill et al. 1992; Blumberg et al. 1997; Shiotsugu et al. 2004). Interestingly, Shisa, which is strongly expressed in the prospective head ectoderm and the Spemann organizer of Xenopus gastrula embryos, and physically interacts with immature forms of the Wnt receptor Frizzled and the FGF receptor within the endoplasmic reticulum. As a result Shisa inhibits their posttranslational maturation and trafficking to the cell surface of Wnt and FGF, and Shisa therefore promotes head formation like cerberus (Yamamoto et al. 2005).
As a hormone and neurotransmitter, adrenaline acts on nearly all body tissues, and its actions are strongly dependent on tissue type and tissue expression of adrenergic receptors. Adrenaline acts by binding to a variety of adrenergic receptors and is a nonselective agonist of all adrenergic receptors, including the major subtypes α1, α2, β1, β2, and β3 (Cotecchia et al. 2012). β-adrenergic receptor (Adrβ) and their associated guanine nucleotide regulatory protein (G protein)/adenylyl cyclase signal transduction pathways are central to the overall regulation of cardiant function (Moniotte et al. 2001; Wachter & Gilbert 2012). Interestingly, in the early developmental stage of Xenopus embryos, RNA coding β1 receptor is present in the mature oocyte, decreases after fertilization up to stage six and then gradually increases during gastrulation (Devic et al. 1997), meaning that embryonic development is likely to be regulated by adrenaline. However, the role of adrenaline for early developmental stages has never been examined. This study is the first report of the role of β-adrenergic signaling for early developmental stage of vertebrate. We show that adrenaline and its receptor have posteriorizing activity during the gastrula stage.