CADHERIN-11 EXPRESSION MARKS THE MESENCHYMAL PHENOTYPE - TOWARDS NEW FUNCTIONS FOR CADHERINS

Cadherin-11 (cad-11) belongs to the cell adhesion type II cadherin fam ily which seems to have different functions from the classic cadherin family. This study shows the overall pattern of cad-11 gene expression during rat embryonic development, from the pregastrula to very late e mbryonic stage. Cad-11 is the first cadherin found to be highly expres sed in the dispersed and migrating mesenchymal cells that originate fr om the neuroectodermal neural crest cells and from the pre-chordal and paraxial mesoderm. A burst of cad-11 expression appears during the ep ithelial to mesenchymal transition, as observed by sclerotome formatio n. Cad-11 mRNAs were present in all mesenchymal cells throughout the e mbryo, regardless of their embryonic origin. A proximo-distal and ante ro-posterior gradient of cad-11 expression is seen in the limb buds, g enitalia, and tail. As development proceeds, while all epithelium are negative, cad-11 is present in all mesenchymal cells involved in vario us morphogenetic events, such as the mesenchyme condensations during c hondrogenesis and in the formation of sclera, cornea, naris, palate an d meninges. Cad-11 was strongly expressed in mesenchyme during lung or kidney branching morphogenesis or the many epithelium to mesenchyme i nductions that operate in the nasal septum, skin, vibrissae, teeth and various glands. High levels of cad-11 transcripts were also found in the dispersed cells of the hyaloid plexus in the vitreous body and in the invading mesenchyme within the trabeculae of the outflow tract of the heart. Cad-11 is thus specific to the mesenchymal phenotype whatev er the stage of embryonic development.