LOW-AFFINITY NERVE GROWTH-FACTOR RECEPTOR IS ASSOCIATED WITH MOTONEURON AXONAL PATHWAYS

The unidentified cell-surface antigen recognized by monoclonal antibod y M7412 is distributed along motoneuron axonal outgrowth pathways in c hicken embryos. To better characterize its role in motoneuron developm ent, the M7412 antigen was purified from chicken embryos by immunoaffi nity chromatography. Its N-terminal amino acid sequence corresponded t o that predicted for chicken low-affinity nerve growth factor receptor (LNGFR). Experiments were performed to confirm that LNGFR was indeed the antigen recognized by M7412. First, M7412 bound to recombinant chi cken LNGFR expressed in mammalian cells. Second, a rabbit serum raised to the purified antigen showed the same staining pattern in chicken e mbryos as did M7412. Lastly, a novel method for direct detection of ne rve growth facter (NGF) bound to its receptors was used to show that i n mixed spinal cord cultures, only neurons that expressed M7412 antige n had low-affinity binding sites for NGF. Furthermore, at the subcellu lar level, M7412 labeling was co-localized with bound NGF. The M7412 a ntigen is thus chicken LNGFR, whose role in motoneuron outgrowth pathw ays is discussed. (C) 1997 Elsevier Science Ireland Ltd.