MONOCLONAL-ANTIBODIES TO A RAT NESTIN FUSION PROTEIN RECOGNIZE A 220-KDA POLYPEPTIDE IN SUBSETS OF FETAL AND ADULT HUMAN CENTRAL-NERVOUS-SYSTEM NEURONS AND IN PRIMITIVE NEUROECTODERMAL TUMOR-CELLS

Nestin is the major intermediate filament protein of embryonic central nervous system (CNS) progenitor cells. To identify proteins involved in early stages of lineage commitment in the developing human CNS we g enerated monoclonal antibodies to a TrpE-rat nestin fusion protein. Th is resulted in a monoclonal antibody (designated NST11) that did not r ecognize authentic human nestin, but did recognize a novel neuron-spec ific human polypeptide expressed in a subset of embryonic and adult CN S neurons as well as in medulloblastomas. NST11 immunoreactivity was a bundant in developing spinal cord motor neurons, but was extinguished in these neurons by 17 weeks gestation. NST11 also labeled Purkinje ce lls at 17 weeks gestation, but Purkinje cells continued to express the NST11 antigen throughout gestation as well as in the adult cerebellum , and NST11 immunoreactivity was more abundant in Purkinje cells than in any other human CNS neurons. No NST11 immunoreactivity was detected in cells of the adult human peripheral nervous system or in a variety of adult non-neural human tissues. Further, NST11 almost exclusively stained cerebellar medulloblastomas. In Western blots of immature and mature human cerebral and cerebellar extracts, NST11 did not bind huma n nestin, but did detect an immunoband with a molecular weight of 220 kd. A similar immunoband was detected in medulloblastoma-derived cell lines with a neuron-like phenotype. These findings suggest that the NS T11 monoclonal antibody recognizes a novel protein expressed by a subp opulation of immature and mature human CNS neurons, medulloblastomas, and medulloblastoma-derived cell lines.