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Synapse formation and clustering of neuroligin-2 in the absence of GABAA receptors


Patrizi, A; Scelfo, B; Viltono, L; Briatore, F; Fukaya, M; Watanabe, M; Strata, P; Varoqueaux, F; Brose, N; Fritschy, J M; Sassoè-Pognetto, M (2008). Synapse formation and clustering of neuroligin-2 in the absence of GABAA receptors. Proceedings of the National Academy of Sciences of the United States of America (PNAS), 105(35):13151-13156.

Abstract

GABAergic synapses are crucial for brain function, but the mechanisms underlying inhibitory synaptogenesis are unclear. Here, we show that postnatal Purkinje cells (PCs) of GABA(A)alpha1 knockout (KO) mice express transiently the alpha3 subunit, leading to the assembly of functional GABA(A) receptors and initial normal formation of inhibitory synapses, that are retained until adulthood. Subsequently, down-regulation of the alpha3 subunit causes a complete loss of GABAergic postsynaptic currents, resulting in a decreased rate of inhibitory synaptogenesis and formation of mismatched synapses between GABAergic axons and PC spines. Notably, the postsynaptic adhesion molecule neuroligin-2 (NL2) is correctly targeted to inhibitory synapses lacking GABA(A) receptors and the scaffold molecule gephyrin, but is absent from mismatched synapses, despite innervation by GABAergic axons. Our data indicate that GABA(A) receptors are dispensable for synapse formation and maintenance and for targeting NL2 to inhibitory synapses. However, GABAergic signaling appears to be crucial for activity-dependent regulation of synapse density during neuronal maturation.

GABAergic synapses are crucial for brain function, but the mechanisms underlying inhibitory synaptogenesis are unclear. Here, we show that postnatal Purkinje cells (PCs) of GABA(A)alpha1 knockout (KO) mice express transiently the alpha3 subunit, leading to the assembly of functional GABA(A) receptors and initial normal formation of inhibitory synapses, that are retained until adulthood. Subsequently, down-regulation of the alpha3 subunit causes a complete loss of GABAergic postsynaptic currents, resulting in a decreased rate of inhibitory synaptogenesis and formation of mismatched synapses between GABAergic axons and PC spines. Notably, the postsynaptic adhesion molecule neuroligin-2 (NL2) is correctly targeted to inhibitory synapses lacking GABA(A) receptors and the scaffold molecule gephyrin, but is absent from mismatched synapses, despite innervation by GABAergic axons. Our data indicate that GABA(A) receptors are dispensable for synapse formation and maintenance and for targeting NL2 to inhibitory synapses. However, GABAergic signaling appears to be crucial for activity-dependent regulation of synapse density during neuronal maturation.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Pharmacology and Toxicology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2 September 2008
Deposited On:12 Nov 2008 08:47
Last Modified:05 Apr 2016 12:33
Publisher:National Academy of Sciences
ISSN:0027-8424
Additional Information:Copyright: National Academy of Sciences USA
Publisher DOI:10.1073/pnas.0802390105
PubMed ID:18723687
Permanent URL: http://doi.org/10.5167/uzh-5317

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