The Wnt-dependent master regulator NKX1-2 controls mouse pre-implantation development

Embryo size, specification, and homeostasis are regulated by a complex gene regulatory and signalling network. Reverse engineering of a mouse embryonic stem cell (ESC) regulatory network and its interrogation with gene expression signatures of Wnt-activated ESC clones identified NKX1-2 as a novel master regulator of pre-implantation embryo development. Nkx1-2 inhibition resulted in reduction of nascent RNA synthesis, downregulation of genes regulating ribosome biogenesis, RNA translation and transport, and in severe alteration of nucleolus structure, with exclusion of RNA polymerase I from nucleoli. In turn, these dysfunctions lead to chromosome missegregation in 2-cell to 4-cell embryo stages, severe decrease of blastomere number, alteration of tight junctions, and lack of microlumens coarsening. Taken together, these changes impair the blastocoel expansion–collapse cycle and embryo cavitation, leading to altered lineage specification and developmental arrest. Overall design: scRNA-Seq of morpholino injected mouse morula and blastocyst embryos