The extracellular matrix of perineuronal nets: Dynamics of molecular organization and functional analysis
Final Report Abstract
Penneuronal nets (PNs) of the extracellular matrix specify the properties of the extracellular space including the presynaptic boutons and associated glial cell processes around many types of CNS Neurons. Our previous work and that of other groups has shown that chondroitin sulfate proteoglycans of the aggrecan family, the glycosammoglycan hyaluronan and the glycoproteins tenascin-R and -C form major but variable constituents of PNs, and that tenascin-R plays an important role in the organization of these macromolecular complexes during brain development and in the maintenance of matrix integrity in the adult. In the continuing project we worked further on the mechanisms of formation and roles of PN components. Removal of PNs by aggrecanase, suppression of PN formation by aggrecan siRNA, and restoration of PNs on proximal dendrites in TNR-deficient cultures via direct clustering of aggrecan with polyclonal aggrecan antibodies suggest the important role of this protein for assembly of PNs. Similarly, suppression of PN formation by inhibitors of hyaluronan synthases and multidrug resistance proteins indicates importance of these Proteins. Although we did not detect significance of perineuronal nets for GABAergic synapse formation in dissociated hippocampal cultures, we found that long-term potentiation is impaired after enzymatic removal of chondroitin sulfates or hyaluronan, and the underlying mechanisms involve an increase in excitability of GABAergic interneurons and a deficit in activity of L-type Ca2+ channels, respectively. We also used genetic mouse models with compromised glutamate release (Munc13-1 knock-out, Munc13-l/2 double knock-out) and chronic pharmacological treatments interfering with specific steps of glutamatergic transmission in organotypic slice cultures. The results indicate that neuronal activity is required but that the glutamatergic system is not essential for PN development. Moreover, we could demonstrate in dissociated hippocampal cultures and in organotypic slice cultures that dendrites, soma and axon initial segment of PN-associated neurons are synchronously ensheathed by aggrecan-immunoreactive matrix components. Regarding the aspects of normal turnover and the possible decomposition of the aggrecan based extracellular matrix under pathological conditions, our studies in transgenic mice forming amyloid plaques showed that PNs resist enzymatic destruction by activated glial cells.
Publications
- Axon initial segment ensheathed by extracellular matrix in perineuronal nets. Neuroscience 138 365-375 (2006)
Brückner, G, Szeoke, S , Pavlica, S , Grosche, J, Kacza, J
- Organization of brain extracellular matrix in the Chilean fat-tailed mouse opossum Thylamys elegans (Waterhouse, 1839). J Chem Neuroanat 32 143-158(2006)
Brückner, G , Pavlica, S , Morawski, M , Palacios, A , Reichenbach, A
- Activity-dependent formation and functions of chondroitin sulfate-rich extracellular matrix of perineuronal nets. Dev Neurobiol 67 570-588(2007)
Dityatev, A , Brückner G, Dityateva, G, Grosche, J , Kleene, R, Schachner, M
- Formation of perineuronal nets in organotypic mouse brain slice cultures is independent of neuronal glutamatergic activity. Eur J Neurosci 25 2640-2648 (2007)
Reimers, S , Hartlage-Rübsamen, M , Brückner, G , Roßner, S
- Aggrecan-based extracellular matrix is an integral part of the basal ganglia circuit. Neuroscience 151 489-504(2008)
Brückner, G , Morawski, M , Arendt, T
