Xiao-Bing Yuan

Background: Autism spectrum disorder (ASD) is biologically heterogeneous and has limited mechanism-informed interventions targeting core behavioral symptoms. Emerging evidence suggests that gut microbial metabolism shapes neurobehavioral outcomes, yet the specific metabolic pathways linking gut ecology to brain function remain incompletely understood. One candidate pathway is polyamine metabolism, which links microbial amino acid metabolism to host regulation and represents a plausible but underexplored contributor to ASD-related phenotypes. Notably, the psychobiotic Lactiplantibacillus plantarum PS128 has been reported to improve social behaviors in individuals with ASD, although the molecular basis for these effects is unclear. In this study, we used Fragile X mental retardation 1 knockout ( Fmr1 KO) mice, a well-established ASD model, to investigate microbiota-dependent metabolic mechanisms underlying autism-like behaviors. Results: We found that autism-like behaviors in Fmr1 KO mice were associated with gut dysbiosis, impaired intestinal barrier integrity, disruption of the arginine–ornithine–polyamine pathway, and elevated putrescine in the prefrontal cortex (PFC). Supplementation with PS128 remodeled the gut microbiota, reduced inflammation- and disease-associated taxa, improved intestinal structure and permeability, and restored polyamine homeostasis. Targeted metabolomics revealed an increased PFC-to-serum putrescine ratio in KO mice, which was normalized following PS128 intervention. This correction was accompanied by reduced expression of polyamine transporters in the PFC, including ATP13A family members. Causal experiments supported a functional role for putrescine, as peripheral elevation of putrescine induced autism-like behaviors in wild-type mice, whereas pharmacological inhibition of putrescine synthesis ameliorated behavioral deficits in Fmr1 KO mice. Conclusions: These findings identify putrescine metabolic dysregulation as a key contributor to autism-like phenotypes and support the existence of an ASD subtype defined by disruption of the arginine–ornithine–polyamine axis. Integrated multi-omics and causal perturbation analyses support a model in which microbiota-targeted intervention rebalances systemic polyamine regulation along the gut–brain axis, thereby improving ASD-relevant behaviors. Our work provides mechanistic evidence linking microbial metabolism to neurochemical homeostasis and highlights the translational potential of metabolic stratification in ASD. Graphical We identify dysregulated microbiota-driven polyamine homeostasis as a causal contributor to autism-like behaviors in Fmr1 knockout mice. A psychobiotic intervention restores gut–brain metabolic balance and rescues social and repetitive behavioral deficits through coordinated microbial and host transport regulation.

The molecular etiology of numerous risk genes for autism spectrum disorder (ASD), including Cadherin 11 (CDH11), remains elusive. We investigated the role of CDH11 in the development of ASD-related behaviors using gene-deficient mice. CDH11 is enriched at synapses in glutamatergic neurons of the anterior cingulate cortex (ACC), which project to the dorsal striatum, nucleus accumbens, and the basolateral amygdala. Developmental ablation of Cdh11 in these neurons led to increased self-grooming, reduced sociability, and decreased neuronal activity in the ACC. Chemogenetic inhibition of ACC glutamatergic neurons recapitulates the over-grooming phenotype, while activation of these neurons mitigates self-grooming in Cdh11-deficient mice. Moreover, targeted expression of CDH11 in the ACC of these mice significantly attenuated their over-grooming behaviors. Proteomics of ACC synaptosomes and CDH11 interactomes revealed that CDH11 participates in synaptic vesicle trafficking, as evidenced by a reduction in presynaptic vesicle density at excitatory synapses in Cdh11-deficient mice. These findings highlight an important role of CDH11 in the development of ASD-related brain circuits and provide insights into the molecular basis of repetitive behaviors in ASD.

Pathogenic variants in MED13L cause MED13L syndrome, a well-defined neurodevelopmental disorder characterized by motor deficits, intellectual disability, and language delay, yet its underlying developmental and molecular mechanisms remain largely elusive. To address this gap, we generated a gene knockout mouse model of MED13L syndrome. While homozygous Med13l knockout exhibit neonatal lethality accompanied by reduced brain volume and cortical thickness, heterozygous mice are viable and display hallmarks of MED13L syndrome, including impaired learning and memory, reduced motor coordination, and heightened anxiety. Additionally, heterozygous mice show microcephaly with simplified neuronal morphology in the motor cortex. Single-cell transcriptomics and immunofluorescence reveal severe cortical neurogenesis deficits in Med13l knockout embryos, driven by impaired neural progenitor differentiation. Integrative multi-omics analyses reveal that MED13L orchestrates cortical neurogenesis by priming the transcriptional activation of key developmental genes, including Neurod2, Sox5, Auts2, and Nfib. This priming effect is mediated by MED13L binding to the core mediator complex, which facilitates the complex’s association with RNA Pol II and subsequent dissociation from MED13L. These findings uncover a pivotal role for MED13L in transcriptional regulation during brain development and highlight potential targets for restoring normal transcriptional programs in MED13L syndrome.

Developing cost-effective and disease-relevant animal models is essential for advancing biomedical research into human disorders. Here we investigate the feasibility of a pig model for autism spectrum disorder (ASD) using embryonic exposure to valproic acid (VPA), an antiepileptic drug known to increase ASD risk. We established experimental paradigms to assess the behavioral characteristics of these pig models. Administration of VPA to Bama miniature pigs (Sus scrofa domestica) during critical embryonic stages resulted in abnormal gait, increased anxiety levels, reduced learning capabilities and altered social patterns, while largely preserving social preference of treated piglets. Notably, we detected significant neuroanatomical changes in cortical regions associated with ASD in the VPA-treated pigs, including cortical malformation, increased neuronal soma size, decreased dendritic complexity and reduced dendritic spine maturation. Transcriptome analysis of the prefrontal cortex of VPA-treated pigs further revealed substantial alterations in the expression of genes linked to ASD, especially genes of the dopamine signaling pathway, highlighting the model’s relevance and potential for shedding light on ASD’s underlying neuropathological and molecular mechanisms. These findings suggest that pig models could serve as a promising alternative to traditional rodent models and provide a more ethical substitute for the use of primates in translational research on neurodevelopmental disorders.

Developing cost-effective and disease-relevant animal models is essential for advancing biomedical research into human disorders. This study investigates the feasibility of a pig model for autism spectrum disorder (ASD) using embryonic exposure to valproic acid (VPA), an antiepileptic drug known to increase ASD risk. We established experimental paradigms to assess the behavioral characteristics of these pig models. Administration of VPA to Bama miniature pigs (Sus scrofa domestica) during critical embryonic stages resulted in abnormal gait, increased anxiety levels, reduced learning capabilities, and altered social patterns, while largely preserving social preference of treated piglets. Notably, we detected significant neuroanatomical changes in cortical regions associated with ASD in the VPA-treated pigs, including cortical malformation, increased neuronal soma size, decreased dendritic complexity, and reduced dendritic spine density and maturation. Transcriptome analysis of the prefrontal cortex of VPA-treated pigs further revealed substantial alterations in the expression of genes linked to ASD, especially genes of the dopamine signaling pathway, highlighting the model’s relevance and potential for shedding light on ASD’s underlying neuropathological and molecular mechanisms. These findings suggest that pig models could serve as a promising alternative to traditional rodent models and provide an ethical substitute for using primates in the translational research of neurodevelopmental disorders.

The neural basis of fear of heights remains largely unknown. In this study, we investigated the fear response to heights in male mice and observed characteristic aversive behaviors resembling human height vertigo. We identified visual input as a critical factor in mouse reactions to heights, while peripheral vestibular input was found to be nonessential for fear of heights. Unexpectedly, we found that fear of heights in naïve mice does not rely on image-forming visual processing by the primary visual cortex. Instead, a subset of neurons in the ventral lateral geniculate nucleus (vLGN), which connects to the lateral/ventrolateral periaqueductal gray (l/vlPAG), drives the expression of fear associated with heights. Additionally, we observed that a subcortical visual pathway linking the superior colliculus to the lateral posterior thalamic nucleus inhibits the defensive response to height threats. These findings highlight a rapid fear response to height threats through a subcortical visual and defensive pathway from the vLGN to the l/vlPAG.

Katanin catalytic subunit A1 like 2 ( KATNAL2 ) is a high-risk gene associated with autism spectrum disorders (ASD), however its impact on brain development and disease remains unclear. The present study revealed an unexpected role of KATNAL2 in regulating ependymal ciliary motion and cerebrospinal fluid flow during brain development, an important contributing factor for ASD. We discovered a distinct expression pattern of KATNAL2 in multiciliated ependymal cells of both human and mouse brains. Notably, an ASD-associated mutation of Katnal2 disrupted its molecular function and resulted in ASD-related behavioral deficits in mice. Additionally, this mutation affected the polarized organization and beating of ependymal cilia, leading to delayed cerebrospinal fluid flow and sustained ventricular enlargement from the early postnatal stage. Conditional ablation of Katnal2 specifically in the ependymal cells of neonatal mice is sufficient to cause ventricular dilation, whereas no such effect was observed in adult mice. Our findings highlight the importance of ependymal motile cilia and hydrocephalus in ASD, offering insights into its pathogenesis and potential intervention.

The neural basis of fear of heights remains essentially unknown. We observed mice displaying stereotyped aversive behaviors when encountered height threats, resembling human height vertigo. Visual input plays a crucial role in mouse reactions to heights, which can also be influenced by vestibular input and prior height experiences. Unexpectedly, fear of heights in inexperienced mice does not rely on image-forming visual processing by the primary visual cortex. Instead, a subset of neurons in the ventral lateral geniculate nucleus (vLGN) connecting to the lateral/ventrolateral periaqueductal gray (l/vlPAG) drives the expression of height-related fear. Additionally, a subcortical visual pathway linking the superior colliculus to the lateral posterior thalamic nucleus inhibits the defensive response to height threats. These findings highlight an unconscious fear response to height threats through a rapid subcortical visual and defensive pathway from vLGN to l/vlPAG. One-Sentence Summary A non-image visual mechanism of fear of heights

A large number of putative risk genes for autism spectrum disorder (ASD) have been reported. The functions of most of these susceptibility genes in developing brains remain unknown, and causal relationships between their variation and autism traits have not been established. The aim of this study was to predict putative risk genes at the whole-genome level based on the analysis of gene co-expression with a group of high-confidence ASD risk genes (hcASDs). The results showed that three gene features – gene size, mRNA abundance, and guanine-cytosine content – affect the genome-wide co-expression profiles of hcASDs. To circumvent the interference of these features in gene co-expression analysis, we developed a method to determine whether a gene is significantly co-expressed with hcASDs by statistically comparing the co-expression profile of this gene with hcASDs to that of this gene with permuted gene sets of feature-matched genes. This method is referred to as "matched-gene co-expression analysis" (MGCA). With MGCA, we demonstrated the convergence in developmental expression profiles of hcASDs and improved the efficacy of risk gene prediction. The results of analysis of two recently-reported ASD candidate genes, CDH11 and CDH9, suggested the involvement of CDH11, but not CDH9, in ASD. Consistent with this prediction, behavioral studies showed that Cdh11-null mice, but not Cdh9-null mice, have multiple autism-like behavioral alterations. This study highlights the power of MGCA in revealing ASD-associated genes and the potential role of CDH11 in ASD.

Background: Gene co-expression analysis (GCA) has emerged as an important tool to identify convergent molecular pathways of ASD risk genes. The aim of this study is to identify ASD-relevant genes at the whole-genome level using GCA with consideration of the effect of confounding factors on GCA, including the size, expression level, and guanine-cytosine content of genes. Methods: Pearson’s correlation coefficient was computed to indicate the co-expression of a gene pair based on the BrainSpan human brain transcriptome dataset. Whether a gene is significantly co-expressed with a group of high-confidence ASD risk genes (hcASDs) was determined by statistically comparing the co-expression of this gene with the hcASD gene set to that of this gene with permuted gene sets of matched gene features. This method is referred to as "matched-gene co-expression analysis" (MGCA). Gene ontology (GO) analysis and construction of integrated GO enrichment networks were performed to reveal convergent pathways of co-expressed genes. Behavioral tests were carried out in gene knockout mice. Results: Gene size, mRNA length, mRNA abundance, and guanine-cytosine content were found to affect co-expression profiles of ASD genes. Using the MGCA method, we confirmed the convergence in the developmental expression profiles of hcASDs. MGCA also effectively revealed convergent molecular pathways of ASD risk genes and determined that CDH11, but not CDH9, is associated with ASD. Mouse behavioral studies showed that Cdh11-null mice, but not Cdh9-null mice, have multiple autistic-like behavioral alterations.Limitations: The use of tissue-derived transcriptomes instead of single-cell transcriptomes may have detected coincident expression of some functionally irrelevant genes in different cell types. Some ASD risk genes may have been missed due to the highly stringent statistical standard of MGCA. Another limitation is the relatively small number of animals analyzed in behavioral tests. Conclusions: Results of this study revealed the importance of considering matched gene features in GCA. CDH11 was confirmed to be an important ASD risk gene and Cdh11-null mice were found to be a very useful animal model for investigation of ASD.