Deletion of the Dishevelled family of genes disrupts anterior-posterior axis specification and selectively prevents mesoderm differentiation.

The Dishevelled proteins transduce both canonical Wnt/β-catenin and non-canonical Wnt/planar cell polarity (PCP) signaling pathways to regulate many key developmental processes during embryogenesis. Here, we disrupt both canonical and non-canonical Wnt pathways by targeting the entire Dishevelled family of genes (Dvl1, Dvl2, and Dvl3) to investigate their functional roles in the early embryo. We identified several defects in anterior-posterior axis specification and mesoderm patterning in Dvl1+/-; Dvl2-/-; Dvl3-/- embryos. Homozygous deletions in all three Dvl genes (Dvl TKO) resulted in defects in distal visceral endoderm migration and a complete failure to induce mesoderm formation. To identify potential mechanisms that lead to the defects in the developmental processes preceding gastrulation, we generated Dvl TKO mouse embryonic stem cells (mESCs) and compared the transcriptional profile of these cells with wild-type (WT) mESCs during germ lineage differentiation into 3D embryoid bodies (EBs). While the Dvl TKO mESCs displayed similar morphology, self-renewal properties, and minor transcriptional variation from WT mESCs, we identified major transcriptional dysregulation in the Dvl TKO EBs during differentiation in a number of genes involved in anterior-posterior pattern specification, gastrulation induction, mesenchyme morphogenesis, and mesoderm-derived tissue development. The absence of the Dvls leads to specific down-regulation of BMP signaling genes. Furthermore, exogenous activation of canonical Wnt, BMP, and Nodal signaling all fail to rescue the mesodermal defects in the Dvl TKO EBs. Moreover, endoderm differentiation was promoted in the absence of mesoderm in the Dvl TKO EBs, while the suppression of ectoderm differentiation was delayed. Overall, we demonstrate that the Dvls are dispensable for maintaining self-renewal in mESCs but are critical during differentiation to regulate key developmental signaling pathways to promote proper axis specification and mesoderm formation.