Primary mesenchyme cells (PMCs) must undergo several changes in their adhesive properties in order to detach from the epithelium of the vegetal plate and ingress into the interior: (1) they must lose affinity for neighboring epithelial cells that remain in the vegetal plate; (2) they must lose affinity for the hyaline layer on the exterior of the embryo; and (3) they presumabl;y must gain affinity for the basal lamina,. since PMCs later migrate within the blastocoel. Hideki Katow anf Michael Solursh used transmission electron microscopy to show that PMCs undergo a dramatic reorganization of their cytoskeleton and their contacts with these three regions during ingression. A colorized adapatation of their original work is shown here:
