Cohort-guided insights into gene-environment interactions in autism spectrum disorders

Dysregulation of the mTOR-FMRP pathway and synaptic plasticity in an environmental model of ASD

Autism Spectrum Disorder (ASD) is caused by genetic, epigenetic, and environmental factors. Mutations in the human FMR1 gene, encoding the Fragile X Messenger Ribonucleoprotein 1 (FMRP), cause the most common monogenic form of ASD, the Fragile X Syndrome (FXS). This study explored the interaction between the FMR1 gene and a viral-like infection as an environmental insult, focusing on the impact on core autistic-like behaviors and the mGluR1/5-mTOR pathway. Pregnant heterozygous Fmr1 mouse females were exposed to maternal immune activation (MIA), by injecting the immunostimulant Poly (I:C) at the embryonic stage 12.5, simulating viral infections. Subsequently, ASD-like behaviors were analyzed in the adult offspring, at 8-10 weeks of age. MIA exposure in wild-type mice led to ASD-like behaviors in the adult offspring. These effects were specifically confined to the intrauterine infection, as immune activation at later stages, namely puberty (Pubertal Immune Activation, PIA) at post-natal day 35 or adulthood (Adult Immune Activation, AIA) at post-natal day 56, did not alter adult behavior. Importantly, combining the Fmr1 mutation with MIA exposure did not intensify core autistic-like behaviors, suggesting an occlusion effect. Mechanistically, MIA provided a strong activation of the mGluR1/5-mTOR pathway, leading to increased LTP and downregulation of FMRP specifically in the hippocampus. Finally, FMRP modulates mTOR activity via TSC2. These findings further strengthen the key role of the mGluR1/5-mTOR pathway in causing ASD-like core symptoms.

Environmental exposure to common pesticide induces synaptic deficit and social memory impairment driven by neurodevelopmental vulnerability of hippocampal parvalbumin interneurons

Environmental exposure to pesticides at levels deemed safe by regulatory agencies has been linked to increased risk for neurodevelopmental disorders. Yet, the mechanisms linking exposure to these disorders remain unclear. Here, we show that maternal exposure to the pesticide deltamethrin (DM) at the no observed adverse effect level (NOAEL) disrupts long-term potentiation (LTP) in the hippocampus of adult male offspring three months after exposure, a phenotype absent in female offspring. Clonazepam, a GABAa receptor agonist, rescued this deficit, indicating impaired hippocampal GABAergic signaling. Recordings from CA1 pyramidal neurons, complemented by MALDI mass spectrometry imaging, showed an imbalance in excitatory/inhibitory tone. Using a combination of parvalbumin (PV)-Cre transgenic mice and hippocampal injection of designer receptors exclusively activated by designer drugs (DREADDs), we show that developmental DM exposure reduces hippocampal PV interneuron intrinsic firing. DREADD activation rescued both PV interneuron firing and LTP deficits. Complementary behavioral experiments revealed a deficit in social memory, a behavior relevant to autism spectrum disorder (ASD) symptomatology, which was restored by DREADD activation. Overall, these results establish a novel mechanistic link between maternal exposure to DM at the NOAEL and known cellular, circuital, and behavioral vulnerabilities, indicating it is a potential driver in the exposome of ASD.

Prenatal exposure to per- and polyfluoroalkyl substances, genetic factors, and autistic traits: Evidence from the Shanghai birth cohort

The epidemiological evidence regarding prenatal PFAS exposure and its interaction with genetic factors on the autistic traits risk is unclear. This study included 1610 mother-child pairs from the Shanghai Birth Cohort (SBC). Ten PFAS were quantified in blood serum collected in the first trimester. Child autistic traits were evaluated at age 4 using a Chinese version of the social responsiveness scale-short form (SRS-SF). We calculated the polygenic risk score (PRS) to evaluate the cumulative genetic effects of autism. Additive interaction models were established to explore whether genetic susceptibility modified the effects of prenatal PFAS exposure. After adjusting for confounders, we found prenatal PFOA exposure was associated with an increased risk of autistic traits in children (OR, 3.05; 95 % CI, 1.14-7.58), and the increased risk associated with PFOA was mitigated among women who reported pre-pregnancy folic acid supplementation. Additionally, an increased risk of autistic traits was observed in children with higher levels of prenatal PFHxS exposure and a high PRS (p for interaction = 0.021). Our findings suggest prenatal PFAS exposure may increase the risk of autistic traits in children, especially in those with a high genetic risk. Further research is warranted to confirm this association and explore the underlying mechanisms.

Dysregulated plasma autoantibodies are associated with B cell dysfunction in young Arab children with autism spectrum disorder in Qatar

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction and communication, as well as the occurrence of stereotyped and repetitive behaviors. Previous studies have provided solid evidence of dysregulated immune system in ASD; however, limited studies have investigated autoantibody profiles in individuals with ASD. This study aims to screen plasma autoantibodies in a well-defined cohort of young children with ASD (n = 100) and their matched controls (n = 60) utilizing a high-throughput KoRectly Expressed (KREX) i-Ome protein-array technology. We identified differential protein expression of 16 autoantibodies in ASD, which were correlated with differential gene expression of these markers in independent ASD cohorts. Meanwhile, we identified a distinct list of 33 autoantibodies associated with ASD severity; several of which were correlated with maternal age and birth weight in ASD. In addition, we found dysregulated numbers of circulating B cells and activated HLADR+ B cells in ASD, which were correlated with altered levels of several autoantibodies. Further in-depth analysis of B cell subpopulations revealed an increased frequency of activated naïve B cells in ASD, as well as an association of resting naïve B cells and transitional B cells with ASD severity. Pathway enrichment analysis revealed disrupted MAPK signaling in ASD, suggesting a potential relevance of this pathway to altered autoantibodies and B cell dysfunction in ASD. Finally, we found that a combination of eight autoantibodies associated with ASD severity showed an area under the curve (ROC-AUC) of 0.937 (95% CI = 0.890, 0.983; p < 0.001), which demonstrated the diagnostic accuracy of the eight-marker signature in the severity classification of ASD cases. Overall, this study determined dysregulated autoantibody profiles and B cell dysfunction in children with ASD and identified an eight-autoantibody panel for ASD severity classification.

Validation of plasma protein glycation and oxidation biomarkers for the diagnosis of autism

Autism Spectrum Disorder (ASD) is a common neurodevelopmental disorder in children. It is currently diagnosed by behaviour-based assessments made by observation and interview. In 2018 we reported a discovery study of a blood biomarker diagnostic test for ASD based on a combination of four plasma protein glycation and oxidation adducts. The test had 88% accuracy in children 5-12 years old. Herein, we present an international multicenter clinical validation study (N = 478) with application of similar biomarkers to a wider age range of 1.5-12 years old children. Three hundred and eleven children with ASD (247 male, 64 female; age 5.2 ± 3.0 years) and 167 children with typical development (94 male, 73 female; 4.9 ± 2.4 years) were recruited for this study at Sidra Medicine and Hamad Medical Corporation hospitals, Qatar, and Hospital Regional Universitario de Málaga, Spain. For subjects 5-12 years old, the diagnostic algorithm with features, advanced glycation endproducts (AGEs)-Nε-carboxymethyl-lysine (CML), Nω-carboxymethylarginine (CMA) and 3-deoxyglucosone-derived hydroimidazolone (3DG-H), and oxidative damage marker, o,o'-dityrosine (DT), age and gender had accuracy 83% (CI 79 - 89%), sensitivity 94% (CI 90-98%), specificity 67% (CI 57-76%) and area-under-the-curve of receiver operating characteristic plot (AUROC) 0.87 (CI 0.84-0.90). Inclusion of additional plasma protein glycation and oxidation adducts increased the specificity to 74%. An algorithm with 12 plasma protein glycation and oxidation adduct features was optimum for children of 1.5-12 years old: accuracy 74% (CI 70-79%), sensitivity 75% (CI 63-87%), specificity 74% (CI 58-90%) and AUROC 0.79 (CI 0.74-0.84). We conclude that ASD diagnosis may be supported using an algorithm with features of plasma protein CML, CMA, 3DG-H and DT in 5-12 years-old children, and an algorithm with additional features applicable for ASD screening in younger children. ASD severity, as assessed by ADOS-2 score, correlated positively with plasma protein glycation adducts derived from methylglyoxal, hydroimidazolone MG-H1 and Nε(1-carboxyethyl)lysine (CEL). The successful validation herein may indicate that the algorithm modifiable features are mechanistic risk markers linking ASD to increased lipid peroxidation, neuronal plasticity and proteotoxic stress.

Intermittent Hypobaric Hypoxia Ameliorates Autistic-Like Phenotypes in Mice

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by persistent deficits in social communication and stereotyped behaviors. Although major advances in basic research on autism have been achieved in the past decade, and behavioral interventions can mitigate the difficulties that individuals with autism experience, little is known about the many fundamental issues of the interventions, and no specific medication has demonstrated efficiency for the core symptoms of ASD. Intermittent hypobaric hypoxia (IHH) is characterized by repeated exposure to lowered atmospheric pressure and oxygen levels, which triggers multiple physiological adaptations in the body. Here, using two mouse models of ASD, male Shank3B -/- and Fmr1 -/y mice, we found that IHH training at an altitude of 5,000 m for 4 h per day, for 14 consecutive days, ameliorated autistic-like behaviors. Moreover, IHH training enhanced hypoxia inducible factor (HIF) 1α in the dorsal raphe nucleus (DRN) and activated the DRN serotonergic neurons. Infusion of cobalt chloride into the DRN, to mimic IHH in increasing HIF1α expression or genetically knockdown PHD2 to upregulate HIF1α expression in the DRN serotonergic neurons, alleviated autistic-like behaviors in Shank3B -/- mice. In contrast, downregulation of HIF1α in DRN serotonergic neurons induced compulsive behaviors. Furthermore, upregulating HIF1α in DRN serotonergic neurons increased the firing rates of these neurons, whereas downregulation of HIF1α in DRN serotonergic neurons decreased their firing rates. These findings suggest that IHH activated DRN serotonergic neurons via upregulation of HIF1α, and thus ameliorated autistic-like phenotypes, providing a novel therapeutic option for ASD.

Umbelliprenin via increase in the MECP2 and attenuation of oxidative stress mitigates the autistic-like behaviors in mouse model of maternal separation stress

Introduction: Autism spectrum disorder (ASD) is a complex neurodevelopmental condition. Maternal separation (MS) stress is an early-life stress factor associated with behaviors resembling Autism. Both MECP2 and oxidative stress are implicated in the pathophysiology of Autism. Umbelliprenin (UMB) is a coumarin compound with various pharmacological properties. Our study aimed to investigate the potential effects of UMB in mitigating autistic-like behaviors in a mouse model subjected to MS stress, focusing on probable alterations in MECP2 gene expression in the hippocampus. Methods: MS paradigm was performed, and mice were treated with saline or UMB. Behavioral tests consisting of the three-chamber test (evaluating social interaction), shuttle box (assessing passive avoidance memory), elevated plus-maze (measuring anxiety-like behaviors), and marble-burying test (evaluating repetitive behaviors) were conducted. Gene expression of MECP2 and measurements of total antioxidant capacity (TAC), nitrite level, and malondialdehyde (MDA) level were assessed in the hippocampus. Results: The findings demonstrated that MS-induced behaviors resembling Autism, accompanied by decreased MECP2 gene expression, elevated nitrite, MDA levels, and reduced TAC in the hippocampus. UMB mitigated these autistic-like behaviors induced by MS and attenuated the adverse effects of MS on oxidative stress and MECP2 gene expression in the hippocampus. Conclusion: In conclusion, UMB likely attenuated autistic-like behaviors caused by MS stress, probably, through the reduction of oxidative stress and an increase in MECP2 gene expression.

Microglia at the Tripartite Synapse during Postnatal Development: Implications for Autism Spectrum Disorders and Schizophrenia

Synapses are the fundamental structures of neural circuits that control brain functions and behavioral and cognitive processes. Synapses undergo formation, maturation, and elimination mainly during postnatal development via a complex interplay with neighboring astrocytes and microglia that, by shaping neural connectivity, may have a crucial role in the strengthening and weakening of synaptic functions, that is, the functional plasticity of synapses. Indeed, an increasing number of studies have unveiled the roles of microglia and astrocytes in synapse formation, maturation, and elimination as well as in regulating synaptic function. Over the past 15 years, the mechanisms underlying the microglia- and astrocytes-dependent regulation of synaptic plasticity have been thoroughly studied, and researchers have reported that the disruption of these glial cells in early postnatal development may underlie the cause of synaptic dysfunction that leads to neurodevelopmental disorders such as autism spectrum disorder (ASD) and schizophrenia.