Involvement and regulation of the left anterior cingulate cortex in the ultrasonic communication deficits of autistic mice.

Introduction: Autism spectrum disorder (ASD) is a group of diseases often characterized by poor sociability and challenges in social communication. The anterior cingulate cortex (ACC) is a core brain region for social function. Whether it contributes to the defects of social communication in ASD and whether it could be physiologically modulated to improve social communication have been poorly investigated. This study is aimed at addressing these questions. Methods: Fragile X mental retardation 1 (FMR1) mutant and valproic acid (VPA)-induced ASD mice were used. Male-female social interaction was adopted to elicit ultrasonic vocalization (USV). Immunohistochemistry was used to evaluate USV-activated neurons. Optogenetic and precise target transcranial magnetic stimulation (TMS) were utilized to modulate anterior cingulate cortex (ACC) neuronal activity. Results: In wild-type (WT) mice, USV elicited rapid expression of c-Fos in the excitatory neurons of the left but not the right ACC. Optogenetic inhibition of the left ACC neurons in WT mice effectively suppressed social-induced USV. In FMR1-/-- and VPA-induced ASD mice, significantly fewer c-Fos/CaMKII-positive neurons were observed in the left ACC following USV compared to the control. Optogenetic activation of the left ACC neurons in FMR1-/- or VPA-pretreated mice significantly increased social activity elicited by USV. Furthermore, precisely stimulating neuronal activity in the left ACC, but not the right ACC, by repeated TMS effectively rescued the USV emission in these ASD mice. Discussion: The excitatory neurons in the left ACC are responsive to socially elicited USV. Their silence mediates the deficiency of social communication in FMR1-/- and VPA-induced ASD mice. Precisely modulating the left ACC neuronal activity by repeated TMS can promote the social communication in FMR1-/- and VPA-pretreated mice.

Establishment of a two-hit mouse model of environmental factor induced autism spectrum disorder.

Autism spectrum disorder (ASD) is a group of developmental diseases characterized by social dysfunction and repetitive stereotype behaviors. Besides genetic mutations, environmental factors play important roles in the development of ASD. Valproic acid (VPA) is widely used for modeling environmental factor induced ASD in rodents. However, traditional VPA modeling is low-in-efficiency and the phenotypes often vary among different batches of experiments. To optimize this ASD-modeling method, we tested "two-hit" hypothesis by single or double exposure of VPA and poly:IC at the critical time points of embryonic and postnatal stage. The autistic-like behaviors of mice treated with two-hit schemes (embryonic VPA plus postnatal poly:IC, embryonic poly:IC plus postnatal VPA, embryonic VPA plus poly: IC, or postnatal VPA plus poly:IC) were compared with mice treated with traditional VPA protocol. The results showed that all single-hit and two-hit schemes produced core ASD phenotypes as VPA single treatment did. Only one group, namely, mice double-hit by VPA and poly:IC simultaneously at E12.5 showed severe impairment of social preference, social interaction and ultrasonic communication, as well as significant increase of grooming activity and anxiety-like behaviors, in comparation with mice treated with the traditional VPA protocol. These data demonstrated that embryonic two-hit of VPA and poly:IC is more efficient in producing ASD phenotypes in mice than the single-hit of VPA, indicating this two-hit scheme could be utilized for modeling environmental factors induced ASD.

Glycolysis mediates neuron specific histone acetylation in valproic acid-induced human excitatory neuron differentiation.

Pregnancy exposure of valproic acid (VPA) is widely adopted as a model of environmental factor induced autism spectrum disorder (ASD). Increase of excitatory/inhibitory synaptic transmission ratio has been proposed as the mechanism of VPA induced ASD. How this happened, particularly at the level of excitatory neuron differentiation in human neural progenitor cells (NPCs) remains largely unclear. Here, we report that VPA exposure remarkably inhibited human NPC proliferation and induced excitatory neuronal differentiation without affecting inhibitory neurons. Following VPA treatment, mitochondrial dysfunction was observed before neuronal differentiation, as showed by ultrastructural changes, respiratory complex activity, mitochondrial membrane potential and oxidation levels. Meanwhile, extracellular acidification assay revealed an elevation of glycolysis by VPA stimulation. Interestingly, inhibiting glycolysis by 2-deoxy-d-glucose-6-phosphate (2-DG) efficiently blocked the excitatory neuronal differentiation of human NPCs induced by VPA. Furthermore, 2-DG treatment significantly compromised the VPA-induced expression of H3ac and H3K9ac, and the VPA-induced binding of H3K9ac on the promoter of Ngn2 and Mash1, two key transcription factors of excitatory neuron fate determination. These data, for the first time, demonstrated that VPA biased excitatory neuron differentiation by glycolysis-mediated histone acetylation of neuron specific transcription factors.

Axin2 coupled excessive Wnt-glycolysis signaling mediates social defect in autism spectrum disorders.

Social dysfunction is the core syndrome of autism spectrum disorder (ASD) and lacks effective medicine. Although numerous risk genes and relevant environmental factors have been identified, the convergent molecular mechanism underlying ASD-associated social dysfunction remains largely elusive. Here, we report aberrant activation of canonical Wnt signaling and increased glycolysis in the anterior cingulate cortex (ACC, a key brain region of social function) of two ASD mouse models (Shank3-/- and valproic acid-treated mice) and their corresponding human neurons. Overexpressing ß-catenin in the ACC of wild-type mice induces both glycolysis and social deficits. Suppressing glycolysis in ASD mice partially rescued synaptic and social phenotype. Axin2, a key inhibitory molecule in Wnt signaling, interacts with the glycolytic enzyme enolase 1 (ENO1) in ASD neurons. Surprisingly, an Axin2 stabilizer, XAV939, effectively blocked Axin2/ENO1 interaction, switched glycolysis/oxidative phosphorylation balance, promoted synaptic maturation, and rescued social function. These data revealed excessive neuronal Wnt-glycolysis signaling as an important underlying mechanism for ASD synaptic deficiency, indicating Axin2 as a potential therapeutic target for social dysfunction.