S103L reactive chondroitin sulfate proteoglycan (aggrecan) mRNA expressed in developing chick brain and cartilage is encoded by a single gene.

A large chondroitin sulfate proteoglycan (CSPG) identified in embryonic chick brain, and synthesized exclusively by neurons in a developmentally expressed pattern that coincides with migration and establishment of neuronal nuclei, reacts with a monoclonal antibody (S103L) developed against the cartilage-specific CSPG, aggrecan. The relationship of the brain and cartilage S103L CSPGs was established by chemical, biosynthetic and molecular analyses. Significant posttranslational differences (absence of keratan sulfate (KS), less CS, and different sulfation patterns) distinguish the brain S103L species from the cartilage S103L species. However, quantitative and qualitative Northern analysis, cassette RT-PCR and direct cloning and sequencing of the entire brain-specific S103L CSPG coding sequence, all indicate that the brain and cartilage core proteins are identical. Thus, although the S103L CSPG synthesized by chick brain and cartilage are the product of a single gene, they are clearly biochemically distinct and differentially expressed proteoglycan products, suggesting tissue specific roles for these proteoglycan homologs.