Early steps in the development of the mouse embryo lead to establishment of the anterior-posterior axis (future head to tail axis). This process depends on a group of cells called the anterior visceral endoderm (AVE), which migrates from the bottom of the embryo to a position that overlies the eventual head. The AVE migrates as a collective group of cells, and a recent paper has found that the GTPase Rac1 is required for this migration event. Above is a set of time-lapse images of an AVE cell from a wild-type (top) or Rac1 mutant (bottom) embryo. The cells are painted in the bottom row of each set of images, highlighting the lack of long protrusions in the Rac1 mutant compared to the wild-type cell.
Reference: Isabelle Migeotte, Tatiana Omelchenko, Alan Hall, Kathryn V. Anderson. Authors’ PLoS Biology paper can be found here.