Gal‐NCAM is a differentially expressed marker for mature sensory neurons in the rat olfactory system

A new monoclonal antibody, 2E11, was produced by immunizing mice with the microsomal fraction of rat accessory olfactory bulb cells. This IgM recognizes a previously described complex alpha-galactosyl containing glycolipid, as well as N-linked glycoproteins at 170 and 210 kD. These proteins correspond to a new nerve cell adhesion molecule (NCAM) glycoform, Gal-NCAM, which contains a blood group B-like oligosaccharide. During embryonic development, the 2E11 epitope is expressed by a subset of mature olfactory sensory neurons randomly dispersed throughout the olfactory epithelium, whereas in the olfactory bulb, immunostaining is restricted to medial areas of the nerve layer. When compared to PSA-NCAM, another NCAM glycoform, Gal-NCAM has a mutually exclusive distribution pattern both in the olfactory epithelium and in the olfactory bulb. We propose a model for the hierarchy of neuronal maturation in the olfactory epithelium, including a switch from PSA-NCAM expression by immature neurons to the expression of Gal-NCAM by mature neurons.