Synaptic activity suppresses expression of neurogenic differentiation factor 2 in an NMDA receptor-dependent manner

Disruption of NEUROD2 causes a neurodevelopmental syndrome with autistic features via cell-autonomous defects in forebrain glutamatergic neurons

While the transcription factor NEUROD2 has recently been associated with epilepsy, its precise role during nervous system development remains unclear. Using a multi-scale approach, we set out to understand how Neurod2 deletion affects the development of the cerebral cortex in mice. In Neurod2 KO embryos, cortical projection neurons over-migrated, thereby altering the final size and position of layers. In juvenile and adults, spine density and turnover were dysregulated in apical but not basal compartments in layer 5 neurons. Patch-clamp recordings in layer 5 neurons of juvenile mice revealed increased intrinsic excitability. Bulk RNA sequencing showed dysregulated expression of many genes associated with neuronal excitability and synaptic function, whose human orthologs were strongly associated with autism spectrum disorders (ASD). At the behavior level, Neurod2 KO mice displayed social interaction deficits, stereotypies, hyperactivity, and occasionally spontaneous seizures. Mice heterozygous for Neurod2 had similar defects, indicating that Neurod2 is haploinsufficient. Finally, specific deletion of Neurod2 in forebrain excitatory neurons recapitulated cellular and behavioral phenotypes found in constitutive KO mice, revealing the region-specific contribution of dysfunctional Neurod2 in symptoms. Informed by these neurobehavioral features in mouse mutants, we identified eleven patients from eight families with a neurodevelopmental disorder including intellectual disability and ASD associated with NEUROD2 pathogenic mutations. Our findings demonstrate crucial roles for Neurod2 in neocortical development, whose alterations can cause neurodevelopmental disorders including intellectual disability and ASD.

L-Lactate Regulates the Expression of Synaptic Plasticity and Neuroprotection Genes in Cortical Neurons: A Transcriptome Analysis

Lactate, a product of aerobic glycolysis in astrocytes, is required for memory formation and consolidation, and has recently emerged as a signaling molecule for neurons and various cell types in peripheral tissues. In particular lactate stimulates mRNA expression of a few plasticity-related genes. Here, we describe a RNA-seq study that unravels genome-wide transcriptomic responses to this energy metabolite in cortical neurons. Our results show that mRNA expression of 20 immediate-early genes involved in the MAPK signaling pathway and in synaptic plasticity were increased by more than twofold following 1 h of lactate stimulation. This effect was dependent on NMDA receptor (NMDAR) activity since it was prevented by pre-treatment with MK-801. Comparison with published datasets showed that a significant proportion of genes modulated by lactate were similarly regulated by a stimulation protocol activating specifically synaptic NMDARs known to result in upregulation of pro-survival and downregulation of pro-death genes. Remarkably, transcriptional responses to lactate were reproduced by NADH (for 74 of the 113 genes, FDR < 0.05), suggesting a redox-dependent mechanism of action. Longer-term gene expression changes observed after 6 h of lactate treatment affected genes involved in regulating neuronal excitability and genes coding for proteins localized at synapses. Gene set enrichment analyses performed with ranked lists of expressed genes revealed effects on molecular functions involved in epigenetic modulation, and on processes relevant to sleep physiology and behavioral phenotypes such as anxiety and hyperactivity. Overall, these results strengthen the notion that lactate effectively regulates activity-dependent and synaptic genes, and highlight new signaling effects of lactate in plasticity and neuroprotection.