Layer- and region-specific distribution of chondroitinase-resistant, lectin-binding extracellular matrix structures in the mouse somatosensory cortex and hippocampus.

Extracellular matrix (ECM) structures in the brain, including perineuronal nets (PNNs), contribute to synaptic plasticity, neuroprotection, and circuit stability. Wisteria floribunda agglutinin (WFA) is widely used to label PNNs but detects only a subset of ECM glycoconjugates. To better understand ECM composition and organization, we used a panel of plant-derived lectins with distinct glycan-binding specificities to examine the spatial distribution of ECM in the mouse primary somatosensory cortex and hippocampus. Brain sections from adult male C57BL/6N mice (n = 6) were stained using seven biotinylated lectins (Jacalin, PSA, AAL, LCA, WGA, PHA-E, and PHA-L). Confocal imaging and quantitative fluorescence analysis revealed that each lectin exhibited a unique pattern of ECM labeling. Several lectins, such as Jacalin, WGA, and PHA-E, showed strong labeling in superficial cortical layers and select hippocampal subfields, while others displayed more diffuse or subregion-specific distributions. Co-labeling with WFA demonstrated partial overlap with some lectins but also revealed non-overlapping ECM components. Notably, most lectin signals, including those forming perineuronal net-like structures, remained intact after chondroitinase ABC digestion, in contrast to the loss of WFA staining. These results highlight the molecular heterogeneity and anatomical specificity of brain ECM structures, revealing a chondroitin sulfate-independent scaffold not visualized by WFA. These results highlight the molecular heterogeneity and anatomical specificity of brain ECM structures. Using diverse lectins provides complementary information to WFA-based labeling and reveals broader ECM architectures. This approach offers new insights into region- and layer-specific ECM organization, with implications for understanding the differential plasticity, resilience, and vulnerability of brain circuits.