Induction of dorsal mesodermal genes by pinhead and chordin

Xenopus embryonic ectodermal cells are responsive to various inducing factors. Mesoderm is specified and patterned by extracellular factors including FGF, Nodal, BMP and Wnt families. Pinhead is another secreted protein implicated in mesoderm formation. We found that Pinhead physically interacts with and antagonizes ADMP (anti-dorsalizing morphogenetic protein) that acts as BMP-like protein to promote ventral mesoderm formation. ADMP and BMPs have been shown to cooperate to activate phospho-Smad1 signaling to lead to ventral mesoderm development. Since Chordin is a BMP antagonist, we hypothesized that Pinhead together with Chordin can promote downregulation of phospho-Smad1 signaling that leads to dorsal mesoderm development. RNA sequencing revealed that Pinhead and Chordin synergize in dorsal mesoderm formation in ectodermal explants. Eight samples are collected for RNAseq from four groups with duplicates. One group is control ectodermal explants (Co), the second is Flag-Pnhd expressing explants (Fpinh), the third is Chordin expressing explants (Chor) and the fourth is Pinhd and chordin expressing explants (Chor-Pinh).