Hippocampal circAnk3 Deficiency Causes Anxiety-like Behaviors and Social Deficits by Regulating the miR-7080-3p/IQGAP1 Pathway in Mice.

BACKGROUND: Circular RNAs are highly enriched in the synapses of the mammalian brain and play important roles in neurological function by acting as molecular sponges of microRNAs. circAnk3 is derived from the 11th intron of the ankyrin-3 gene, Ank3, a strong genetic risk factor for neuropsychiatric disorders; however, the function of circAnk3 remains elusive. In this study, we investigated the function of circAnk3 and its downstream regulatory network for target genes in the hippocampus of mice. METHODS: The DNA sequence from which circAnk3 is generated was modified using CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9) technology, and neurobehavioral tests (anxiety and depression-like behaviors, social behaviors) were performed in circAnk3+/- mice. A series of molecular and biochemical assays were used to investigate the function of circAnk3 as a microRNA sponge and its downstream regulatory network for target genes. RESULTS: circAnk3+/- mice exhibited both anxiety-like behaviors and social deficits. circAnk3 was predominantly located in the cytoplasm of neuronal cells and functioned as a miR-7080-3p sponge to regulate the expression of Iqgap1. Inhibition of miR-7080-3p or restoration of Iqgap1 in the hippocampus ameliorated the behavioral deficits of circAnk3+/- mice. Furthermore, circAnk3 deficiency decreased the expression of the NMDA receptor subunit GluN2a and impaired the structural plasticity of dendritic synapses in the hippocampus. CONCLUSIONS: Our results reveal an important role of the circAnk3/miR-7080-3p/IQGAP1 axis in maintaining the structural plasticity of hippocampal synapses. circAnk3 might offer new insights into the involvement of circular RNAs in neuropsychiatric disorders.

Neurodevelopmental defects in human cortical organoids with N-acetylneuraminic acid synthase mutation.

Biallelic genetic variants in N-acetylneuraminic acid synthase (NANS), a critical enzyme in endogenous sialic acid biosynthesis, are clinically associated with neurodevelopmental disorders. However, the mechanism underlying the neuropathological consequences has remained elusive. Here, we found that NANS mutation resulted in the absence of both sialic acid and protein polysialylation in the cortical organoids and notably reduced the proliferation and expansion of neural progenitors. NANS mutation dysregulated neural migration and differentiation, disturbed synapse formation, and weakened neuronal activity. Single-cell RNA sequencing revealed that NANS loss of function markedly altered transcriptional programs involved in neuronal differentiation and ribosomal biogenesis in various neuronal cell types. Similarly, Nans heterozygous mice exhibited impaired cortical neurogenesis and neurobehavioral deficits. Collectively, our findings reveal a crucial role of NANS-mediated endogenous sialic acid biosynthesis in regulating multiple features of human cortical development, thus linking NANS mutation with its clinically relevant neurodevelopmental disorders.

Synapse differentiation-induced gene 1 regulates stress-induced depression through interaction with the AMPA receptor GluA2 subunit of nucleus accumbens in male mice.

Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are key regulators during the process of synaptic plasticity in major depression disorder (MDD). Synapse differentiation-induced gene 1 (SynDIG1) functions as an atypical AMPAR auxiliary subunit and regulates synaptic AMPAR content; however, the role of SynDIG1 in MDD remains elusive. In this study, we found that the SynDIG1 expression was significantly increased in the neurons of the nucleus accumbens (NAc) of male mice after chronic social defeat stress (CSDS). CSDS enhanced SynDIG1-GluA2 binding and promoted the surface expression of AMPAR subunit GluA2 in the NAc. Knockdown of SynDIG1 decreased the surface expression of GluA2 and reversed the alteration of dendrite spines in the neurons, eventually alleviating the depressive-like behaviors of the stressed mice. Moreover, intra-NAc injection of IP12, a specific peptide to disrupt the interaction of SynDIG1 with GluA2, rescued depressive-like behaviors. Collectively, SynDIG1 regulates the surface expression of GluA2 and dendritic remodeling in the NAc of male mice under CSDS, thus mediating the depressive-like behaviors.

Simvastatin Blocks Reinstatement of Cocaine-induced Conditioned Place Preference in Male Mice with Brain Lipidome Remodeling.

Drug-associated reward memories are conducive to intense craving and often trigger relapse. Simvastatin has been shown to regulate lipids that are involved in memory formation but its influence on other cognitive processes is elusive. Here, we used a mass spectrometry-based lipidomic method to evaluate the impact of simvastatin on the mouse brain in a cocaine-induced reinstatement paradigm. We found that simvastatin blocked the reinstatement of cocaine-induced conditioned place preference (CPP) without affecting CPP acquisition. Specifically, only simvastatin administered during extinction prevented cocaine-primed reinstatement. Global lipidome analysis showed that the nucleus accumbens was the region with the greatest degree of change caused by simvastatin. The metabolism of fatty-acids, phospholipids, and triacylglycerol was profoundly affected. Simvastatin reversed most of the effects on phospholipids induced by cocaine. The correlation matrix showed that cocaine and simvastatin significantly reshaped the lipid metabolic pathways in specific brain regions. Furthermore, simvastatin almost reversed all changes in the fatty acyl profile and unsaturation caused by cocaine. In summary, pre-extinction treatment with simvastatin facilitates cocaine extinction and prevents cocaine relapse with brain lipidome remodeling.