Mouse ten-m/odz is a new family of dimeric type II transmembrane proteins expressed in many tissues

The Drosophila gene ten-m/odz is the only pair rule gene identified to date which is not a transcription factor, In an attempt to analyze the structur e and the function of ten-m/odz in mouse, we isolated four murine ten-m cDN As which code for proteins of 2,700-2,800 amino acids. All four proteins (T en-m1-4) lack signal peptides at the NH2 terminus, but contain a short hydr ophobic domain characteristic of transmembrane proteins, 300-400 amino acid s after the NH2 terminus. About 200 amino acids COOH-terminal to this hydro phobic region are eight consecutive EGF-like domains. Cell transfection, biochemical, and electronmicroscopic studies suggest tha t Ten-mi is a dimeric type II transmembrane protein. Expression of fusion p roteins composed of the NH2-terminal and hydrophobic domain of ten-mi attac hed to the alkaline phosphatase reporter gene resulted in membrane-associat ed staining of the alkaline phosphatase. Electronmicroscopic and electropho retic analysis of a secreted form of the extracellular domain of Ten-mi sho wed that Ten-mi is a disulfide-linked dimer and that the dimerization is me diated by EGF-like modules 2 and 5 which contain an odd number of cysteines . Northern blot and immunohistochemical analyses revealed widespread expressi on of mouse ten-m genes, with most prominent expression in brain. All four ten-m genes can be expressed in variously spliced mRNA isoforms, The extrac ellular domain of Ten-mi fused to an alkaline phosphatase reporter bound to specific regions in many tissues which were partially overlapping with the Ten-mi immunostaining. Far Western assays and electronmicroscopy demonstra ted that Ten-mi can bind to itself.