ECM molecules
The neural ECM lacks the typical fibrous proteins that form the ECM of other tissues (collagens, fibronectin,
laminin, etc.). Instead, the major components of the neural ECM are the polysaccharide hyaluronic acid and associated glycoproteins and proteoglycans. Together, these molecules form a fine, soft mesh of small filaments that surrounds neurons and glial cells.
Major components of the neural extracellular matrix. Adapted from:
Viapiano and Matthews, Trends in Mol. Medicine (2006).
Sometimes, the fine structure of the ECM becomes condensed around certain types of neurons and forms a dense
perineuronal net that can be easily detected by microscopy. It is not known what makes some neurons
have 'PNets' while others do not. Even more, the specific functions of these nets are very poorly
understood, althought they have been proposed to control neuronal excitability, the formation of
synaptic contacts, and act as a barrier to synaptic plasticity in the adult brain.
Brainstem neuron showing a perineuronal net with typical 'honeycomb' structure that envelops the cell (image
courtesy of Dr. Jerry Silver, Dept. Neurosciences, Case Western Reserve University)
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