DISTRIBUTION OF HEPARAN-SULFATE PROTEOGLYCANS IN EMBRYONIC CHICKEN NEURAL RETINA AND ISOLATED INNER LIMITING MEMBRANE

Quantitative distribution of proteoglycans was studied in retinal neur al epithelium and its basement membrane (inner limiting membrane). Hep aran sulfate proteoglycans (HSPGs) were primarily associated with both inner and outer plexiform (synaptic) layers, and inner limiting membr ane (ILM), as determined by autoradiographs of lyase-digested cryosect ions. Based on distribution of S-35-sulfate-labeled proteoglycans, the isolated ILM contained on average approximately three fourths of its proteoglycans as HSPGs and one fourth as chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs), whereas the remaining retina contain ed approximately equal amounts of the two proteoglycans (PGs). Immunoh istochemical staining indicates that the core proteins of the HSPGs in the ILM are distinct from those of the plexiform layers. The photorec eptor layer, which other studies have shown to contain much of the ext racellular CS/DSPGs, was not examined. Enrichment of distinct HSPGs in the ILM and plexiform layers support the conclusion that the HSPGs ma y be intimately involved in the different developmental events charact erizing the two regions: development and extension of ganglion cell ax ons in the former, synaptogenesis and neuronal function in the latter.