Maternal factors initiate development in many animal embryos but the zygotic gene combinations activated by these factors are poorly understood. Now, on ,Rothbächer and co-workers reveal that the maternal transcription factor Ci-GATAa (orthologue of vertebrate GATA4, 5 and 6) controls the ectodermal regulatory network in Ciona intestinalis. The ectoderm, which develops into epidermis and nervous tissue, occupies the animal half of ascidian embryos. The researchers report that Ci-GATAa activity is initially found throughout the embryo before being repressed in the vegetal hemisphere by maternal β-catenin. In the animal hemisphere, Ci-GATAa first activates the pan-ectodermal gene Ci-fog. After neural induction, it also activates Ci-otx in neural progenitor cells. The researchers show that this activation pattern is achieved by Ci-GATAa and maternal Ets1/2 binding to the Ci-otx enhancer and synergistically activating Ci-otx in neural territories; in non-neural territories, maternal Ets1/2 prevents Ci-otx activation by Ci-GATAa. Overall, these results identify a precise combinatorial code of maternal factors that initiates ectodermal development in Ciona.
