THE MURINE TYPE-II TGF-BETA RECEPTOR HAS A COINCIDENT EMBRYONIC EXPRESSION AND BINDING PREFERENCE FOR TGF-BETA-1

We have isolated cDNAs of the murine type II TGF-beta receptor and hav e found a conserved cytoplasmic domain, but a less extensive homology in the extracellular receptor domain between the human and murine homo logues. In situ hybridization analysis of the mouse fetus during mid g estation localized the expression of this receptor to various developi ng tissues, primarily in the mesenchyme and epidermis. This expression pattern correlates well with the expression of TGF-beta in general an d especially TGF-beta 1, suggesting that TGF-beta 1 exerts its develop mental role through this receptor in an autocrine or paracrine fashion . Type II receptor expression was not detected in the central nervous system and developing cartilage. These tissues lack TGF-beta 1 express ion but express TGF-beta 2 and/or TGF-beta 3, suggesting that they may exert their activities through separate receptor isoforms. In additio n, the efficient binding of TGF-beta 1, but not TGF-beta 2, to the clo ned type II receptor strengthens the likelihood that additional type I I receptor isoforms exist which display preferential binding to TGF-be ta 2 and have their own defined role in development.