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.

We identified seven families associating NEUROD2 pathogenic mutations with ASD and intellectual disability. To get insight into the pathophysiological mechanisms, we analyzed cortical development in Neurod2 KO mice. Cortical projection neurons (CPNs) over-migrated during embryogenesis, inducing abnormal thickness and laminar positioning of cortical layers. At juvenile ages, dendritic spine turnover and intrinsic excitability were increased in L5 CPNs. Differentially expressed genes in Neurod2 KO mice were enriched for voltage-gated ion channels, and the human orthologs of these genes were strongly associated with ASD. Furthermore, adult Neurod2 KO mice exhibited core ASD-like behavioral abnormalities. Finally, by generating Neurod2 conditional mutant mice we demonstrate that forebrain excitatory neuron-specific Neurod2 deletion recapitulates cellular and behavioral ASD phenotypes found in full KO mice. Our findings demonstrate crucial roles for Neurod2 in cortical development and function, whose alterations likely account for ASD and related symptoms in the newly defined NEUROD2 mutation syndrome.

Karen Runge 1 *, Rémi Mathieu 1 *, Stéphane Bugeon 2 *, Sahra Lafi 1,2, Corinne Beurrier 2 &, Surajit Sahu 1&, Fabienne Schaller 1, Arthur Loubat 1, Leonard Herault 3, Stéphane Gaillard 4, Mélanie Cahuc 1, Emilie Pallesi-Pocachard 1, Aurélie Montheil 1, Andreas Bosio 5, Jill A Rosenfeld 6, Eva Hudson 7, Kristin Lindstrom 8, Saadet Mercimek-Andrews 9, Lauren Jeffries 10, Arie van Haeringen 11, Olivier Vanakker 12, Bruno Pichon 13, Audrey Van Hecke 14, Dina Amrom 14, Sebastien Küry 15, Candace Gamble 7, Alfonso Represa 1, Carlos Cardoso 1 *, Harold Cremer 2 * and Antoine de Chevigny 1,£

AbstractWe identified seven families associatingNEUROD2pathogenic mutations with ASD and intellectual disability. To get insight into the pathophysiological mechanisms, we analyzed cortical development inNeurod2KO mice. Cortical projection neurons (CPNs) over-migrated during embryogenesis, inducing abnormal thickness and laminar positioning of cortical layers. At juvenile ages, dendritic spine turnover and intrinsic excitability were increased in L5 CPNs. Differentially expressed genes inNeurod2KO mice were enriched for voltage-gated ion channels, and the human orthologs of these genes were strongly associated with ASD. Furthermore, adultNeurod2KO mice exhibited core ASD-like behavioral abnormalities. Finally, by generatingNeurod2conditional mutant mice we demonstrate that forebrain excitatory neuron-specificNeurod2deletion recapitulates cellular and behavioral ASD phenotypes found in full KO mice. Our findings demonstrate crucial roles forNeurod2in cortical development and function, whose alterations likely account for ASD and related symptoms in the newly definedNEUROD2mutation syndrome.