RESTRICTED EXPRESSION OF TYPE-II TGF-BETA RECEPTOR IN MURINE EMBRYONIC-DEVELOPMENT SUGGESTS A CENTRAL ROLE IN TISSUE MODELING AND CNS PATTERNING

The type-II TGF beta receptor mediates many of the biological response s to TGF beta. An examination of the expression of the type-II TGF bet a receptor during mouse embryogenesis therefore provides specific info rmation about the role of TGF beta during embryogenesis than has been available to date. We have isolated the genomic murine homologue of th e human type-II TGF beta receptor corresponding to exon 2. The murine and human sequences show a high degree of homology. Using the murine p robe, we found that type-II TGF beta receptor expression is regulated in both a spatial and a temporal fashion by using in situ hybridizatio n and ribonuclease protection assays. Type-II TGF beta receptor expres sion is localized to the mesenchyme during critical interactions with adjacent epithelium such as developing hair follicles, whisker follicl es and tooth anlage. In the central nervous system, type-II TGF beta r eceptor expression is highly restricted to the floor plate. Strong exp ression is also detected in migrating neural crest cells, meninges, an d choroid plexus. Specific mesenchymal localization of type-II TGF bet a receptor is also observed in lung, kidney, intestine, stomach, and b ladder. The restricted expression of type-II TGF beta receptor in mese nchymal cells at sites of epithelial-mesenchymal interactions suggests that type-II TGF beta receptor plays a major role in mediating the es tablishment of embryonic organ systems. The highly restricted expressi on of type-II TGF beta receptor in the developing CNS suggests an impo rtant role for a serine/threonine kinase in patterning of the nervous system.