Genomic organization and expression pattern of mouse neuroglycan C in the cerebellar development

Neuroglycan C (NGC) is a membrane-spanning chondroitin sulfate proteoglycan with an epidermal growth factor module that is expressed predominantly in the brain. Cloning studies with mouse NGC cDNA revealed the expression of t hree distinct isoforms (NGC-I, -II, and -III) in the brain and revealed tha t the major isoform showed 94.3% homology with the rat counterpart. The NGC gene comprised six exons, was approximately 17 kilobases in size, and was assigned to mouse chromosome band 9F1 by fluorescence in situ hybridization , Western blot analysis demonstrated that, although NGC in the immature cer ebellum existed in a proteoglycan form, most NGC in the mature cerebellum d id not bear chondroitin sulfate chain(s), indicating that NGC is a typical part-time proteoglycan, Immunohistochemical studies showed that only the Pu rkinje cells were immunopositive in the cerebellum. In the immature Purkinj e cells, NGC, probably the proteoglycan form, was immunolocalized to the so ma and thick dendrites on which the climbing fibers formed synapses, not to the thin branches on which the parallel fibers formed synapses, This findi ng suggests the involvement of NGC in the differential adhesion and synapto genesis of the climbing and parallel fibers with the Purkinje cell dendrite s.