Abstract
Dendritic spines are the postsynaptic targets of excitatory synaptic inputs that undergo extensive proliferation and maturation during the first postnatal month in mice. However, our understanding of the molecular mechanisms that regulate spines during this critical period is limited. Previous work has shown that pannexin 1 (Panx1) regulates neurite growth and synaptic plasticity. We therefore investigated the impact of global Panx1 KO on spontaneous cortical neuron activity using Ca2+ imaging and in silico network analysis. Panx1 KO increased both the number and size of spontaneous co-active cortical neuron network ensembles. To understand the basis for these findings, we investigated Panx1 expression in postnatal synaptosome preparations from early postnatal mouse cortex. Between 2 and 4 postnatal weeks, we observed a precipitous drop in cortical synaptosome protein levels of Panx1, suggesting it regulates synapse proliferation and/or maturation. At the same time points, we observed significant enrichment of the excitatory postsynaptic density proteins PSD-95, GluA1, and GluN2a in cortical synaptosomes from global Panx1 knock-out mice. Ex vivo analysis of pyramidal neuron structure in somatosensory cortex revealed a consistent increase in dendritic spine densities in both male and female Panx1 KO mice. Similar findings were observed in an excitatory neuron-specific Panx1 KO line (Emx1-Cre driven; Panx1 cKOE) and in primary Panx1 KO cortical neurons cultured in vitro. Altogether, our study suggests that Panx1 negatively regulates cortical dendritic spine development.
Footnotes
The authors declare no competing financial interests. A disclosure has been made with the University of Victoria Research Partnerships and Knowledge Mobilization, and a provisional patent application has been filed for a peptide targeting a Panx1-Crmp2 interaction (US Application 62/767,806).
This work was supported by operating grants from the Canadian Institutes of Health Research (Grant MOP142215), The Scottish Rite Charitable Foundation of Canada (15118), and the University of Victoria-Division of Medical Sciences to L.A.S., by a Michael Smith Foundation for Health Research and British Columbia Schizophrenia Society Foundation Scholar Award (5900) to L.A.S., by a University of Victoria Fellowship Graduate Award to J.C.S.A., partial salary support from the Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education Co-innovation Center of Neuroregeneration, Nantong University, China to M.L., and infrastructure support from the Canada Foundation for Innovation (29462) and the BC Knowledge Development Fund (804754) for the Leica SP8 confocal microscope system to L.A.S. We thank Maria Weaver (supported by a University of Victoria Summer Undergraduate Student Award) and Ana De Lucas-Rius for technical assistance.
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