Molecular Brain Research, 2 (1987) 271-275 271 Elsevier BRM 80013 A human teratocarcinoma which expresses a rare neuronal cell surface antigen P.D. Kushner 1, G.M. Cole 2, H. Sternberg 1'* and P.I. Woloshin 1 lALS and Neuromuscular Research Center, San Francisco, CA 94115 (U.S.A.) and 2Department of Physiology and Anatomy, University of California, Berkeley, CA 94720 (U.S.A.) (Accepted 16 June 1987) Key words: Tor 23; NTERA-2; Human teratocarcinoma; Neuronal cell surface antigen A molecular characterization of the events at the cell surface of neurons is pivotal for our understanding of how the nervous system is formed and maintained. The study of cell surface events in the human nervous system may be crucial to the study of human neuro- logical maladies. NTERA-2 is a human teratocarcinoma which is unique amongst the teratocarcinomas for its ability to express many neurons. Tested for the binding of a monoclonal antibody Tot 23, which recognizes a surface antigen on rare and specific neurons, cul- tures of NTERA-2 cells contained cells with a neuronal morphology which bound the monoclonal antibody Tor 23 on their surface. The data indicate that Tor 23 antigen is a cell surface molecule with the same or very similar properties in rays, rats, and humans. The NTERA-2 cells are thus capable of expressing highly differentiated neuronal cell surface phenotypes and promise to be a powerful model system for the study of cell surface events of the human nervous system in vitro. Teratocarcinomas yield tumor cell lines that have the unique potential to express many different cell types 21. The capability of one stem cell to divide and produce many different cell phenotypes has made the teratocarcinomas useful for the study of devel- opment and embryogenesis 17. In the study of the ner- vous system, the teratocarcinomas have not been widely utilized, probably because many teratocarci- nomas do not express a significant proportion of neu- ronal cells. Recently, a clonal embryonal carcinoma of human origin, NTERA-2 (ref. 4), has been found to express a significant number of cells with neuronal phenotypes when these pluripotent cells are grown under the appropriate conditions 3,8,16. The cells are neuronal by morphologic criteria: from a large soma, a 'neuron' extends multiple long processes which branch extensively and form ultrastructurally identi- fied synapses on other neuronal processes 8. In addi- tion, these cells possess neurofilaments and express tetanus toxin binding 8,16. Because the NTERA-2 cultures can be induced to contain a large proportion of neurons and are of hu- man origin, they offer a unique opportunity to study human neuronal expression and development in vit- ro. The differentiated cultures, while known to ex- press general neuronal properties, have not yet, however, been shown to express cell surface phe- notypes of neuronal subgroups. A demonstration of a highly differentiated and rare neuronal cell surface phenotype in these cultures would establish them as an in vitro model system in which cell surface prop- erties are analogous to those found in situ. We have tested a clonal derivative of the NTERA- 2, NT2/D1, for the binding of an antibody which de- fines the cell surface of a rare and discrete set of CNS neurons. Tor 23 is a monoclonal antibody which rec- ognizes a determinant on the cell surface of motor neurons and a highly restricted subset of other brain neurons 12'2°. Tor 23 was made to a purely cholinergic nerve terminal preparation from the electric organ of * Present address: Department of Physiology and Anatomy, University of California, Berkeley, CA 94720, U.S.A. Correspondence: P.D. Kushner, ALS and Neuromuscular Research Center, 2351 Clay Street, Rm. 416, San Francisco, CA 94115, U.S.A. 0169-328X/87/$03.50 © 1987 Elsevier Science Publishers B.V. (Biomedical Division)