Expression of highly polysialylated NCAM (NCAM-H) in developing and adult chicken auditory organ

Neural cell adhesion molecule (NCAM) is highly polysialylated (NCAM-H) in developing tissues, and recent findings suggest that NCAM-H is more essential for neural development than poorly sialylated NCAM (NCAM-L). In order to understand the precise role of NCAM-H in developing and adult inner ears, the immunohistochemical localization of NCAM-H in developing and adult chicken inner ears was examined using a monoclonal antibody which is only specific for NCAM-H. Immunoreactivity of NCAM-H was initially observed on acoustic ganglion at stage 24, when peripheral (afferent) fibers begin to emerge from the ganglion cells. At stage 38, when peripheral fibers form synapses with hair cells, NCAM-H was observed on peripheral fibers and the base of hair cells in the auditory epithelium. At stage 42, NCAM-H on nerve fibers disappeared, and only some acoustic ganglion cells were still positive for NCAM-H. This immunostain on ganglion cells was retained after birth. These data are consistent with the hypothesis that NCAM-H specifically regulates the afferent nerve fibers' growth and synaptogenesis with hair cells during inner ear development and may be associated with processing of auditory information and neuronal plasticity.