Final Report Summary - ZEBRASOMWNT (Role of canonical Wnt signaling during somite formation in the zebrafish embryo)
Role of canonical Wnt signaling during somite formation in the zebrafish embryo Vertebrae, ribs and most skeletal muscles derive from the somites, which are segmented embryonic structures. They form periodically at the anterior extremity of the unsegmented presomitic mesoderm (PSM) and this can be seen by the formation of a new somitic boundary (See Figure1). In the meantime, new cells are being added in the PSM by posterior growth of the embryo. It has been shown that the rhythm of this process is set up by oscillation of cyclic gene expression, and it has been proposed that the position where the future boundary forms is defined by a determination front. This front would regress posteriorly with the growth of the embryo, thereby shifting posteriorly the position of the next boundary after one period of cyclic gene expression. The canonical Wnt pathway has been suggested in the mouse to control the position of the determination front and to regulate some cyclic genes (1-4). However, it remains difficult to specifically address its function in the segmentation of the PSM because this pathway plays an important role earlier in development for the formation of posterior structures (5, 6). In particular, the role of Wnt in somite formation is unknown in zebrafish embryo.