DACS, novel matrix structure composed of chondroitin sulfate proteoglycan in the brain

Chondroitin sulfate proteoglycans (CSPGs) are major components of the extracellular matrix (ECM) in the brain. In the adult cerebral cortex, there are special CSPG-containing structures known as perineuronal nets (PNNs), which are highly condensed ECM structures. Here, we report a novel CSPG-containing structure distinct from PNNs in the adult mouse cerebral cortex. An anti-chondroitin sulfate antibody CS56 delineated a structure with a unique morphology like a dandelion clock. Accordingly, we named it DAndelion Clock-like Structure (DACS). Immunohistochemical evidence showed that DACSs surrounded a group of NeuN-positive/GABA-negative neurons. At ultrastructural level, CS56-immunoreactivities were localized in the cytoplasm and on the membrane of astrocytes. As the postnatal cerebral cortex matured, DACSs became visible around the end of the critical period. This is the first report demonstrating the presence of an ECM structure DACS composed of CSPGs around a group of cortical neurons in the adult cerebral cortex.