RT Journal Article
SR Electronic
T1 Differential Expression and Cell-Type Specificity of Perineuronal Nets in Hippocampus, Medial Entorhinal Cortex and Visual Cortex Examined in the Rat and Mouse
JF eneuro
JO eNeuro
FD Society for Neuroscience
SP ENEURO.0379-16.2017
DO 10.1523/ENEURO.0379-16.2017
A1 Kristian Kinden Lensjø
A1 Ane Charlotte Christensen
A1 Simen Tennøe
A1 Marianne Fyhn
A1 Torkel Hafting
YR 2017
UL http://www.eneuro.org/content/early/2017/05/25/ENEURO.0379-16.2017.abstract
AB Perineuronal nets (PNNs) are specialized extracellular matrix structures that condense around the soma and proximal dendrites of subpopulations of neurons. Emerging evidence suggests that they are involved in regulating brain plasticity. However, the expression of PNNs varies between and within brain areas. A lack of quantitative studies describing the distribution and cell-specificity of PNNs makes it difficult to reveal the functional roles of PNNs. In the current study, we examine the distribution of PNNs and the identity of PNN-enwrapped neurons in three brain areas with different cognitive functions: the dorsal hippocampus, medial entorhinal cortex (mEC) and primary visual cortex (V1). We compared rats and mice as knowledge from these species are often intermingled. The most abundant expression of PNNs was found in the mEC and V1, while dorsal hippocampus showed strikingly low levels of PNNs, apart from dense expression in the CA2 region. In hippocampus we also found apparent species differences in expression of PNNs. While we confirm that the PNNs enwrap parvalbumin-expressing (PV+) neurons in V1, we found that they mainly co-localize with excitatory CamKII-expressing neurons in CA2. In mEC we demonstrate that in addition to PV+ cells, the PNNs co-localize with reelin-expressing stellate cells. We also show that the maturation of PNNs in mEC coincides with the formation of grid cell pattern, while PV+ cells, unlike in other cortical areas, are present from early postnatal development. Finally, we demonstrate considerable effects on the number of PSD-95 - gephyrin puncta after enzymatic removal of PNNs.Significance Statement Perineuronal nets (PNNs) are proposed as a key regulator of plasticity in the adult brain. However, PNNs are not uniformly expressed and their prevalence and cell-type specificity is lacking for several well-studied brain regions. Here, we examine the visual cortex, hippocampus and the medial entorhinal cortex (mEC) and show that the density and structure of PNNs as well their cell-type specificity are different between brain areas and between rats and mice. We show for the first time a dense expression of PNNs in mEC and that their assembly during postnatal development coincides with reports on development of the grid cell’s activity pattern. The variable expression patterns of PNNs may reflect different levels of plasticity and wiring of the neural networks.