Epigenetics & Chromatin

The Spemann organizer is an essential signaling centre in Xenopus axis formation. Th e establishment of Spemann organizer is due to the dorsal accumulation of nuclear β-catenin under the infl uence of cytoplasmic determinants displaced by fertilization. It has been reported that β-catenin binds to TCF/LEF and recruits the methyl transferase enzyme Prmt2 in order to modify the chromatin structure there by inducing the expression of dorsal organizer genes. Zic2 is a member of the Zinc fi nger of cerebellum family. In human and mice, the lack of functional Zic2 provokes a defective node and holoprosencephaly. Zic2 can modulate key organizer gene cascades such as canonical Wnt/β-catenin and TGF-β/Nodal signaling, but its precise role in the organizer/node development remains unknown. Here, we report using animal cap assay and ChIP experiments that the maternal Zic2 is required for the canonical Wnt signaling and it acts as a pioneer factor. We provide evidence that maternal Zic2 modulates Prmt2-mediated epigenetic bookmarking of crucial organizer genes before the mid-blastula transition while zygotic Zic2 controls homeostasis of both Wnt/β-catenin and TGF-β/Nodal gene targets during organizer formation.