Cerebellar Shank2 Regulates Excitatory Synapse Density, Motor Coordination, and Specific Repetitive and Anxiety-Like Behaviors

Abstract

Shank2 is a multidomain scaffolding protein implicated in the structural and functional coordination of multiprotein complexes at excitatory postsynaptic sites as well as in psychiatric disorders, including autism spectrum disorders. While Shank2 is strongly expressed in the cerebellum, whether Shank2 regulates cerebellar excitatory synapses, or contributes to the behavioral abnormalities observed in IntroductionThe Shank/ProSAP family of excitatory postsynaptic scaffolding proteins contains three known members, Shank1, Shank2, and Shank3, which are thought to play important roles in the structural assembly of the multiprotein complexes in the postsynaptic density (PSD) as well as in the functional coordination of excitatory synaptic signaling (Sheng and Sala, 2001;Boeckers et al., 2002; Sheng and Hoogenraad, 2007; Feng and Zhang, 2009; Grabrucker et al., 2011;Sheng and Kim, 2011;Sala et al., 2015).Shank2 (also known as ProSAP1) contains several domains for protein-protein interactions (Du et al., 1998;Boeckers et al., 1999b;Lim et al., 1999;Sheng and Kim, 2000), which mediate the interactions of Shank2 with diverse PSD proteins, including GKAP/SAPAP, Homer, and GluD2 Significance StatementThe postsynaptic side of excitatory synapses contains multiprotein complexes, termed the postsynaptic density, which contains receptors, scaffolding/adaptor proteins, and signaling molecules. Shank2 is an excitatory postsynaptic scaffolding protein implicated in the formation and functional coordination of the postsynaptic density and has been linked to autism spectrum disorders. Using Shank2-null mice and Shank2-conditional knock-out mice with a gene deletion restricted to cerebellar Purkinje cells, we explored functions of Shank2 in the cerebellum. We found that Shank2 regulates excitatory synapse density, motor coordination, and specific repetitive and anxiety-like behaviors, but is not associated with autistic-like social deficits or repetitive behaviors.

Pianp deficiency links GABAB receptor signaling and hippocampal and cerebellar neuronal cell composition to autism-like behavior

“…The trend to lower DA concentrations in the amygdala of PianpKO may suggest that altered dopaminergic signaling could be involved as DA signaling in the amygdala has been described to affect anxiety [30][31][32][33][34][35][36][37][38][39]. Anxiety-like behavior is also present in mice with Purkinje cell-specific deficiency of Shank2 [40]. Thus, enhanced anxiety in PianpKO could be mediated by altered output signaling from the cerebellum.…”

Deficiency of Shank2 causes mania-like behavior that responds to mood stabilizers

“…using different lines of Cre-transgenic mice (53,54). In addition, although change in synaptic proteins and synaptic function related to NMDAR responses has also been reported also in both Δe6 -/-and Δe6-7…”

“…Two separate mutations, Δe6 and Δe6-7, have been introduced into mice globally or specifically in the cerebellar PCs (26,27,53,54). While the molecular consequences of the Δe6 and the Δe6-7 deletions may be expected to be similar, there are significant differences in the behaviors and synaptic functions in these two lines of Shank2 mutant mice (Supplemental Table 4).…”

A DLG2 deficiency in mice leads to reduced sociability and increased repetitive behavior accompanied by aberrant synaptic transmission in the dorsal striatum

“…Whole brain lysates were prepared by boiling with β-mercaptoethanol directly after homogenization. Total brain lysates separated in electrophoresis and transferred to a nitrocellulose membrane were incubated with primary antibodies to DLG2/PSD-93 (#1634, rabbit, as previously described [20]), DLG4/PSD-95 (Neuromab 75-028), and α-tubulin (Sigma T5168) at 4°C overnight. Fluorescent secondary antibody signals were detected using Odyssey® Fc Dual Mode Imaging System.…”