Neurgluycan C, a neural tissue-specific transmembrane chondroitin sulfate proteoglycan, in retinal neural network formation

PURPOSE. Neuroglycan C (NGC) is a transmembrane chondroitin sulfate proteog lycan present exclusively in central nervous system tissues. In the current study the expression pattern and characterization of NGC during the develo pment of the retina were investigated. METHODS. Expressional changes of NGC mRNAs during rat retinal development w ere examined by semiquantitative reverse transcription-polymerase chain rea ction (RT-PCR). The localization and characterization of NGC core proteins were investigated by immunoblot analysis and immunohistochemistry using an anti-NGC antibody. RESULTS. Immunohistochemical analysis revealed that NGC was highly expresse d in the nerve fiber layer (NFL) and inner plexiform layer (IPL) in rat pos tnatal developing retina. At embryonal stages, NGC immunoreactivities were faint. In contrast, at postnatal developmental stages (approximately postna tal day [P]7), intense immunoreactivity was observed in the NFL and IPL, wh ere active dendrite branching was observed, and conventional synapses began to be formed. As retinal layer differentiation proceeded (from P14 to P42) , immunoreactivities in the inner retinal layers gradually became fainter. Immunoblot and semiquantitative RT-PCR analyses showed that the peak level of NGC expression occurred on approximately P7 and P14. Glycosylation of th e NGC core protein changed as the retinal layers matured. In immunoelectron microscopic analysis, NGC immunoreactivity was located on the axonal membr anes of neuronal cells in the postnatal retina, whereas immunoreactivity wa s reduced on membranes at the adult stage. In retinal ganglion cells in vit ro, NGC was highly localized in their spiny budding neurites. CONCLUSIONS. The results show spatiotemporal expression patterns of NGC, an d suggest that it plays a role in the formation of neural networks in retin al development.