Control of progenitor cell positioning and organ patterning during embryogenesis. Danio rerio

The precise positioning of organ progenitor cells constitutes an essential, yet poorly understood step in organ development and function. Using primordial germ cells and the process of gonadogenesis as an in vivo model, we present the developmental mechanisms facilitating the maintenance of a motile progenitor cell population at the site where the organ develops. We find that the action of repulsive cues coupled with the generation of physical barriers confine the cells to the correct bilateral positions within the embryo. Using computer particle-based simulations we could also demonstrate the role of reflecting barriers, from which cells turn away upon contact, and the importance of proper level of cell-cell interaction for maintaining the tight cell clusters and their correct positioning at the target region. The cellular mechanisms operating during those events were determined using high-resolution live imaging microscopy. This analysis revealed cell polarity change upon interaction with the physical barrier and the establishment of compact clusters that involves increased cell-cell interaction as a result of collapse of cell protrusions and enhanced adhesion. The combination of these developmental and cellular Overall design: RNA profiling in zebrafish embryos of 7 hpf and 36 hpf in sorted germ cells and randomly sorted somatic cells