Meeting Abstract
The genesis of gastrulation was arguably a key evolutionary innovation that enabled metazoan diversification, leading to the formation of distinct germ layers that gives rise to specialized tissues. The gene expression profile of the cells that give rise to these different germ layers is regulated by the transcriptional activators/repressors whose activity is governed by the inputs of intracellular and/or extracellular signals. A recent study in the basal metazoan Nematostella vectensis has characterized the NvTcf/canonical-Wnt (cWnt) signaling inputs in to the cnidarian endomesodermal gene regulatory network (GRN). To extend the functional analysis of signaling pathways in the GRN, we knocked down the TGFβ molecule NvBMP 2/4, a putative key player of the cnidarian endomesodermal GRN using a translation blocking morpholino. A previous study has shown that BMP signaling in Nematostella might be playing a role in patterning the endoderm and the dorso-ventral (DV) axis but these conclusions were based on the expression patterns of a limited number of marker genes. In our study, confocal microscopy showed that the NvBMP 2/4 morphant embryos failed to form a normal epithelial gut, indicating to defects in cell-fate specification. Further analysis of gene expression profiles of morphant embryos using in-situ hybridization showed that NvBMP 2/4 knock down affected the expression of a subset of genes including NvSnailB and NvFgf1a, which were not affected by NvTcf/cWnt inhibition in the cnidarian endomesodermal GRN. These results suggest that BMP 2/4 signaling has additional inputs in to the endomesodermal GRN in Nematostella. Further analysis of these inputs would provide critical information for a detailed understanding of the transcriptional regulation/interaction of key players of the cnidarian endomesodermal GRN.
