Spemann organizer transcriptome induction by early beta-catenin, Wnt, Nodal, and Siamois signals in Xenopus laevis

Significance We present a genome-wide study of the signals responsible for the early induction of the body axis in the following experimental conditions: β-catenin morpholino; Wnt , Siamois , and Cerberus mRNAs; LiCl treatment; and dorsal-ventral regenerating half-embryos bisected at gastrula. Comparing 46 RNA-seq libraries, we uncovered the genetic networks that initiate dorsal-ventral patterning and Spemann’s organizer formation. We defined an early β-catenin signature that has only minor overlap with recently published late zygotic Wnt signatures. The relation of these early steps of development to endomesodermal germ layer induction was studied by overexpressing the growth factor antagonist Cerberus. This study offers a rich resource for understanding the earliest inductive events in the body plan of a model vertebrate embryo.