Impaired response to sleep deprivation in heterozygous Disc1 mutant mice

Adolescent sleep defects and dopaminergic hyperactivity in mice with a schizophrenia-linked Shank3 mutation

Shank3 is a shared risk gene for autism spectrum disorders and schizophrenia. Sleep defects have been characterized for autism models with Shank3 mutations; however, evidence has been lacking for the potential sleep defects caused by Shank3 mutation associated with schizophrenia and how early in development these defects may occur. Here we characterized the sleep architecture of adolescent mice carrying a schizophrenia-linked, R1117X mutation in Shank3. We further employed GRABDA dopamine sensor and fiber photometry to record dopamine release in the nucleus accumbens during sleep/wake states. Our results show that homozygous mutant R1117X mice have significantly reduced sleep in the dark phase during adolescence, altered electroencephalogram power, especially during the rapid-eye-movement sleep, and dopamine hyperactivity during sleep but not during wakefulness. Further analyses suggest that these adolescent defects in sleep architecture and dopaminergic neuromodulation tightly correlate with the social novelty preference later in adulthood and predict adult social performance during same-sex social interactions. Our results provide novel insights into the sleep phenotypes in mouse models of schizophrenia and the potential use of developmental sleep as a predictive metric for adult social symptoms. Together with recent studies in other Shank3 models, our work underscores the idea that Shank3-involved circuit disruptions may be one of the shared pathologies in certain types of schizophrenia and autism. Future research is needed to establish the causal relationship among adolescent sleep defects, dopaminergic dysregulation, and adult behavioral changes in Shank3 mutation animals and other models.

Altered synaptic protein expression, aberrant spine morphology, and impaired spatial memory in Dlgap2 mutant mice, a genetic model of autism spectrum disorder

A microdeletion of approximately 2.4 Mb at the 8p23 terminal region has been identified in a Taiwanese autistic boy. Among the products transcribed/translated from genes mapped in this region, the reduction of DLGAP2, a postsynaptic scaffold protein, might be involved in the pathogenesis of autism spectrum disorder (ASD). DLGAP2 protein was detected in the hippocampus yet abolished in homozygous Dlgap2 knockout (Dlgap2 KO) mice. In this study, we characterized the hippocampal phenotypes in Dlgap2 mutant mice. Dlgap2 KO mice exhibited impaired spatial memory, indicating poor hippocampal function in the absence of DLGAP2. Aberrant expressions of postsynaptic proteins, including PSD95, SHANK3, HOMER1, GluN2A, GluR2, mGluR1, mGluR5, βCAMKII, ERK1/2, ARC, BDNF, were noticed in Dlgap2 mutant mice. Further, the spine density was increased in Dlgap2 KO mice, while the ratio of mushroom-type spines was decreased. We also observed a thinner postsynaptic density thickness in Dlgap2 KO mice at the ultrastructural level. These structural changes found in the hippocampus of Dlgap2 KO mice might be linked to impaired hippocampus-related cognitive functions such as spatial memory. Mice with Dlgap2 deficiency, showing signs of intellectual disability, a common co-occurring condition in patients with ASD, could be a promising animal model which may advance our understanding of ASD.

Chronic N-Acetylcysteine Treatment Prevents Amphetamine-Induced Hyperactivity in Heterozygous Disc1 Mutant Mice, a Putative Prodromal Schizophrenia Animal Model

Symptoms of schizophrenia (SZ) typically emerge during adolescence to young adulthood, which gives a window before full-blown psychosis for early intervention. Strategies for preventing the conversion from the prodromal phase to the psychotic phase are warranted. Heterozygous (Het) Disc1 mutant mice are considered a prodromal model of SZ, suitable for studying psychotic conversion. We evaluated the preventive effect of chronic N-acetylcysteine (NAC) administration, covering the prenatal era to adulthood, on the reaction following the Amph challenge, which mimics the outbreak or conversion of psychosis, in adult Het Disc1 mice. Biochemical and morphological features were examined in the striatum of NAC-treated mice. Chronic NAC treatment normalized the Amph-induced activity in the Het Disc1 mice. Furthermore, the striatal phenotypes of Het Disc1 mice were rescued by NAC including dopamine receptors, the expression of GSK3s, MSN dendritic impairments, and striatal PV density. The current study demonstrated a potent preventive effect of chronic NAC treatment in Disc1 Het mice on the acute Amph test, which mimics the outbreak of psychosis. Our findings not only support the benefit of NAC as a dietary supplement for SZ prodromes, but also advance our knowledge of striatal dopamine receptors, PV neurons, and GSK3 signaling pathways as therapeutic targets for treating or preventing the pathogenesis of mental disorders.