Fig 1.

Schematic of perineuronal net chondroitin sulfate-glycosaminoglycan (CS-GAG) sulfation patterns in the brain. A, Depiction of a neuron enmeshed by sulfated CS-GAG containing perineuronal nets. B-C, The brain CS-GAG sulfation code is comprised of five CS isomers (CS-O, -A, -C-, -D, -E) distinguished by their unique sulfation pattern (non-, mono-, and di-sulfated), the relative abundance of which can influence perineuronal net stability and biological function. D, Experimental workflow for the release, isolation, and purification of CS disaccharides from formalin-fixed human brain tissue using chondroitinaseABC (ChABC). Isolated CS isomers are quantitatively analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) and the remaining brain tissue is sequentially labeled for protein expression using immunohistochemistry