Effects of sex and DTNBP1 (dysbindin) null gene mutation on the developmental GluN2B-GluN2A switch in the mouse cortex and hippocampus.

Duncan Sinclair,Mary Mcmullen,Joseph Cesare,Greg C Carlson,Karin E Borgmann-Winter,Chang-Gyu Hahn

doi:10.1186/s11689-016-9148-7

Abstract

BackgroundNeurodevelopmental disorders such as autism spectrum disorders and schizophrenia differentially impact males and females and are highly heritable. The ways in which sex and genetic vulnerability influence the pathogenesis of these disorders are not clearly understood. The n-methyl-d-aspartate (NMDA) receptor pathway has been implicated in schizophrenia and autism spectrum disorders and changes dramatically across postnatal development at the level of the GluN2B-GluN2A subunit “switch” (a shift from reliance on GluN2B-containing receptors to reliance on GluN2A-containing receptors). We investigated whether sex and genetic vulnerability (specifically, null mutation of DTNBP1 [dysbindin; a possible susceptibility gene for schizophrenia]) influence the developmental GluN2B-GluN2A switch.MethodsSubcellular fractionation to enrich for postsynaptic density (PSD), together with Western blotting and kinase assay, were used to investigate the GluN2B-GluN2A switch in the cortex and hippocampus of male and female DTNBP1 null mutant mice and their wild-type littermates. Main effects of sex and DTNBP1 genotype, and interactions with age, were assessed using factorial ANOVA.ResultsSex differences in the GluN2B-GluN2A switch emerged across development at the frontal cortical synapse, in parameters related to GluN2B. Males across genotypes displayed higher GluN2B:GluN2A and GluN2B:GluN1 ratios (p < 0.05 and p < 0.01, respectively), higher GluN2B phosphorylation at Y1472 (p < 0.01), and greater abundance of PLCγ (p < 0.01) and Fyn (p = 0.055) relative to females. In contrast, effects of DTNBP1 were evident exclusively in the hippocampus. The developmental trajectory of GluN2B was disrupted in DTNBP1 null mice (genotype × age interaction p < 0.05), which also displayed an increased synaptic GluN2A:GluN1 ratio (p < 0.05) and decreased PLCγ (p < 0.05) and Fyn (only in females; p < 0.0005) compared to wild-types.ConclusionsSex and DTNBP1 mutation influence the GluN2B-GluN2A switch at the synapse in a brain-region-specific fashion involving pY1472-GluN2B, Fyn, and PLCγ. This highlights the possible mechanisms through which risk factors may mediate their effects on vulnerability to disorders of NMDA receptor dysfunction.Electronic supplementary materialThe online version of this article (doi:10.1186/s11689-016-9148-7) contains supplementary material, which is available to authorized users.

Highlights

Neurodevelopmental disorders such as autism spectrum disorders and schizophrenia differentially impact males and females and are highly heritable
This GluN2B-GluN2A switch was more gradual and protracted in the frontal cortex than in the hippocampus. It occurred in the context of developmental increases in the abundance of all GluN subunits in the frontal cortex (GluN1 F(3, 96) = 4.4, p = 0.005; GluN2A F(3, 96) = 19.4, p < 1 × 10 −5; GluN2B F(3, 96) = 7.3, p < 0.0005; Fig. 2b) and GluN1 and GluN2A in the hippocampus (GluN1 F(3, 64) =
The sex difference in the GluN2B:GluN2A ratio in postsynaptic density (PSD) enrichments from the frontal cortex appeared to be driven by differences in levels of GluN2B, with a sex difference observed in the GluN2B:GluN1 ratio (F(1, 96) = 8.0, p = 0.0057; Fig. 3e) but not the GluN2A:GluN1 ratio (F(1, 96) = 2.4, p = 0.13; Fig. 3i)

Summary

Introduction

Neurodevelopmental disorders such as autism spectrum disorders and schizophrenia differentially impact males and females and are highly heritable. The N-methyl-D-aspartate (NMDA) receptor pathway has been implicated in schizophrenia and autism spectrum disorders and changes dramatically across postnatal development at the level of the GluN2B-GluN2A subunit “switch” (a shift from reliance on GluN2B-containing receptors to reliance on GluN2A-containing receptors). The NMDA receptor becomes less sensitive to blockade by GluN2B antagonists ifenprodil, CP101,606, and Ro25-6981 [9, 15,16,17,18] These changes are accompanied by concurrent changes in electrophysiological properties, such as increasing excitatory postsynaptic current (EPSC) amplitude and decreasing decay time [15, 17], and reflect the healthy, activity-dependent maturation of the brain [19,20,21]

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