Development/Plasticity/Repair Sensory Deprivation Alters Aggrecan and Perineuronal Net Expression in the Mouse Barrel Cortex

An important role for the neural extracellular matrix in modulating cortical activity-dependent synaptic plasticity has been established by a number of recent studies. However, identification of the critical molecular components of the neural matrix that mediate these processes is far fromcomplete. Of particular interest is the perineuronal net (PN), an extracellularmatrix component found surrounding the cell bodyandproximalneurites of a subset ofneurons.Becauseof the appositionof thePN to synapses andexpressionof this structure coincident with the close of the critical period, it has been hypothesized that nets could play uniquely important roles in synapse stabilization and maturation. Interestingly, previous work has also shown that expression of PNs is dependent on appropriate sensory stimulation in the visual system. Here, we investigated whether PNs in the mouse barrel cortex are expressed in an activity-dependent manner bymanipulating sensory input throughwhisker trimming. Importantly, thismanipulationdidnot lead to a global loss of PNsbut instead led to a specific decrease inPNs, detectedwith the antibodyCat-315, in layer IVof thebarrel cortex. In addition,we identified akey activity-regulated component of PNs is the proteoglycan aggrecan.We also demonstrate that these Cat-315-positive neurons virtually all also express parvalbumin. Together, these data are in support of an important role for aggrecan in the activity-dependent formation of PNs on parvalbumin-expressing cells and suggest a role for expression of these nets in regulating the close of the critical period. Key words: chondroitin sulfate; lectican; extracellular matrix; proteoglycan; parvalbumin; somatosensory cortex; critical perio