Neuroglycan C (NGC) is a transmembrane-type of chondroitin sulfate proteoglycan that is exclusively expressed in the central nervous system. NGC gene expression is developmentally regulated, and is altered by addiction to psychostimulants and by nerve lesion. Its core protein has a particular multidomain structure differing from those of other known proteoglycans, and this protein is modified post-translationally in various ways such as phosphorylation and glycosylation. NGC is a novel part-time proteoglycan that changes its structure from a proteoglycan form to a non-proteoglycan form without chondroitin sulfate chains during the development of the cerebellum and retina. Results obtained from immunohistological, cell biological and biochemical experiments suggest that NGC is involved in neuronal circuit formation in the central nervous system. To verify the proposed functions of NGC in the brain, production and phenotype-analyses are being performed in mice with various NGC gene mutations causing the expression or glycosylation of NGC to be altered.