Elimination of the four extracellular matrix molecules tenascin-C, tenascin-R, brevican and neurocan alters the ratio of excitatory and inhibitory synapses

Christine Gottschling,David Wegrzyn,Andreas Faissner,Bernd Denecke

doi:10.1038/s41598-019-50404-9

Christine Gottschling, David Wegrzyn + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-50404-9

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Journal: Scientific Reports	Publication Date: Sep 26, 2019
Citations: 83	License type: open-access

Affiliation: Ruhr University Bochum, RWTH Aachen University

Abstract

The synaptic transmission in the mammalian brain is not limited to the interplay between the pre- and the postsynapse of neurons, but involves also astrocytes as well as extracellular matrix (ECM) molecules. Glycoproteins, proteoglycans and hyaluronic acid of the ECM pervade the pericellular environment and condense to special superstructures termed perineuronal nets (PNN) that surround a subpopulation of CNS neurons. The present study focuses on the analysis of PNNs in a quadruple knockout mouse deficient for the ECM molecules tenascin-C (TnC), tenascin-R (TnR), neurocan and brevican. Here, we analysed the proportion of excitatory and inhibitory synapses and performed electrophysiological recordings of the spontaneous neuronal network activity of hippocampal neurons in vitro. While we found an increase in the number of excitatory synaptic molecules in the quadruple knockout cultures, the number of inhibitory synaptic molecules was significantly reduced. This observation was complemented with an enhancement of the neuronal network activity level. The in vivo analysis of PNNs in the hippocampus of the quadruple knockout mouse revealed a reduction of PNN size and complexity in the CA2 region. In addition, a microarray analysis of the postnatal day (P) 21 hippocampus was performed unravelling an altered gene expression in the quadruple knockout hippocampus.

Highlights

The functionality of neuronal synapses is warranted by the correspondence of a pre- and a postsynapse that form the synaptic cleft which allows for the transmission of an electrical activity by chemical neurotransmitters
We examined the proportion of inhibitory and excitatory synapses in culture, as well as the spontaneous activity of the neuronal networks using the multielectrode array (MEA) approach[32]
Hippocampal neurons and cortical astrocytes of wildtype and quadruple knockout mice were cultivated in the four possible combinations (Nwt/wt/Awt/wt, Nwt/wt/Ak°/k°, Nk°/ko/Awt/wt, Nko/ko/Ako/ko), in the following referred to as conditions

Summary

Introduction

The functionality of neuronal synapses is warranted by the correspondence of a pre- and a postsynapse that form the synaptic cleft which allows for the transmission of an electrical activity by chemical neurotransmitters. In a previous study our laboratory investigated hippocampal neurons of the quadruple knockout mouse in vitro and found diminished PNNs and an altered expression of synaptic proteins that were accompanied by a decreased frequency of mEPSCs and mIPSCs after 14 and 21 DIV29. This translates in an altered synaptic plasticity in vivo as the quadruple www.nature.com/scientificreports/. In the light of these observations we sought to expand our insight into the importance of the ECM for the process of synaptogenesis To this end we explored the quadruple knockout mouse in conjunction with the indirect co-culture system of cortical astrocytes and hippocampal neurons[29,31]. We compared the gene expression in this brain structure at postnatal day (P) 21 in wildtype and quadruple knockout mice by microarray analysis

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Results

Conclusion