Shown is a mesenchyme blastula stage of the sea urchin embryo. The embryo is stained with antibody to ß-catenin (red) which stains all the adherens junctions of the embryo, and with an antibody to primary mesenchyme cells (green). When the primary mesenchyme cells leave the epithelium to become mesenchyme cells one of their first changes is to eliminate ß-catenin from their adherens junctions. This enables them to pull out of the epithelium and become mesenchymal cells.

David McClay
Professor
Department of Biology