In silico Gene Set and Pathway Enrichment Analyses Highlight Involvement of Ion Transport in Cholinergic Pathways in Autism: Rationale for Nutritional Intervention

Genetic Relationships between Attention-Deficit/Hyperactivity Disorder, Autism Spectrum Disorder, and Intelligence

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) commonly co-occur; both traits exert an influence on intelligence scores. Genetic relationships between these three traits are far from being clear.

METHODS

The summary results of genome-wide association studies of ADHD (20,183 cases and 35,191 controls), ASD (18,381 cases and 27,969 controls), and intelligence (269,867 participants) were used for the analyses. Local genetic correlation analysis and polygenic overlap analysis were used to explore the shared genetic components between ADHD, ASD, and intelligence. Mendelian randomization (MR) analysis was used to examine the causal associations between ADHD, ASD, and intelligence. A cross-trait meta-analysis was performed to identify pleiotropic genetic variants across the three traits.

RESULTS

Our results showed that intelligence has a positive and negative genetic correlation with ASD and ADHD, respectively, including three hub genomic regions showing correlated genetic effects across the three traits. Polygenic overlap analysis indicated that all the risk variants contributing to ADHD are overlapped with half of those for intelligence, and the majority of the shared variants have opposite effect directions between them. The majority of risk variants (80%) of ASD are overlapped with almost all the risk variants of intelligence (97%). Notably, some ASD/intelligence overlapping variants displayed opposing effects on these two conditions. MR analysis showed that the genetic liability to higher intelligence was associated with an increased risk for ASD (OR = 1.12) and a decreased risk for ADHD (OR = 0.78). Cross-trait meta-analyses identified 170 pleiotropic genomic loci across the three traits, including 12 novel loci. Functional analyses of the novel genes support their potential involvement in neurodevelopment.

CONCLUSION

Our results suggest that ADHD is associated with inheriting a reduced set of low-intelligence alleles, whereas ASD results from incongruous effects from a mixture of high-intelligence and low-intelligence contributing alleles summed up with additional, ASD-specific risk variants not associated with intelligence.

Shared genetics between autism spectrum disorder and attention-deficit/hyperactivity disorder and their association with extraversion

BACKGROUND

Deciphering the genetic relationships between autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) may uncover underlining shared pathophysiology as well as inform treatment.

METHODS

The summary results of genome-wide association studies on ADHD, ASD, and extraversion were utilized for the analyzes. Genetic correlations between ADHD, ASD, and extraversion were tested using linkage disequilibrium score regression. Causal relationships between ADHD, ASD, and extraversion were investigated using Mendelian randomization (MR) analysis. Novel pleiotropic genomic loci shared by ADHD and ASD were identified using a cross-trait meta-analysis.

RESULTS

Extraversion was positively correlated with ADHD (r_g = 0.205) and negatively correlated with ASD (r_g = -0.193). The MR analysis showed that ADHD confers a causal effect on ASD (OR: 1.35, 95% confidence interval (CI):1.20-1.52) and vice versa (1.46, 1.38-1.55). Extraversion exerts a causal effect on ADHD only (1.19, 1.05-1.33). The cross-trait meta-analysis identified three novel pleiotropic genomic loci for ADHD and ASD, involving two pleiotropic genes, LINC00461 and KIZ.

CONCLUSIONS

Our study provides new insights into the shared genetics of ADHD and ASD and their connections with extraversion.

Vitamin A supplementation ameliorates prenatal valproic acid-induced autism-like behaviors in rats

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social deficits and repetitive stereotyped behaviors. Prenatal exposure to the anticonvulsant drug valproic acid (VPA) is reported to induce ASD in human and ASD-like phenotypes in rodents. Unfortunately, the etiology and pathogenesis of ASD remains unclear.

METHODS

Pregnant rats received an intraperitoneal injection of 600 mg/kg VPA on E12.5 to construct the ASD rat model in offspring. The different expression of long non-coding RNA (lncRNA) and mRNA profiles in the hippocampus were determined by RNA sequencing to investigate potential mechanisms of VPA-induced ASD. Gene Ontology (GO) and pathway enrichment analysis were performed to predict the function of dysregulated lncRNAs. Co-expression network and real-time polymerase chain reaction (RT-PCR) analysis were conducted to validate the potential regulatory lncRNA-mRNA network.

RESULTS

VPA increased the total distance, time spent in the central zone and self-grooming (open field test) in rats. Meanwhile, VPA induced social impairment (three-chamber sociability test) and repetitive behaviors (marble burying test). A total of 238 lncRNAs and 354 mRNAs were differentially expressed in the VPA group. In addition, the dysregulated lncRNAs were involved in neural function and developmental processes of ASD. 5 lncRNAs and 7 mRNAs were differently expressed and included in the lncRNA-mRNA co-expression network. RT-PCR confirmed the upregulation of 4 lncRNAs and 6 mRNAs, and identified a potential regulatory network of NONRATT021475.2 (lncRNA) and Desert hedgehog (Dhh). Moreover, VPA decreased the serum vitamin A (VA) levels in offspring rats on postnatal day (PND) 21 and 49. Importantly, VA supplementation significantly restored VPA-induced autism-related behaviors and upregulation of NONRATT021475.2 and Dhh in the hippocampus of ASD rats.

CONCLUSION

This study not only contributed to understand the importance of lncRNAs and mRNAs in the progression of ASD, but also identified VA as a potential therapy for the condition.

DATA AVAILABILITY

The data that support the findings of this study are available from the corresponding author with reasonable request.

Mitochondrial Disruption by Amyloid Beta 42 Identified by Proteomics and Pathway Mapping

Alzheimer’s disease (AD) is marked by chronic neurodegeneration associated with the occurrence of plaques containing amyloid β (Aβ) proteins in various parts of the human brain. An increase in several Aβ fragments is well documented in patients with AD and anti-amyloid targeting is an emerging area of therapy. Soluble Aβ can bind to various cell surface and intracellular molecules with the pathogenic Aβ₄₂ fragment leading to neurotoxicity. Here we examined the effect of Aβ₄₂ on network adaptations in the proteome of nerve growth factor (NGF) differentiated PC12 cells using liquid-chromatography electrospray ionization mass spectrometry (LC-ESI MS/MS) proteomics. Whole-cell peptide mass fingerprinting was coupled to bioinformatic gene set enrichment analysis (GSEA) in order to identify differentially represented proteins and related gene ontology (GO) pathways within Aβ₄₂ treated cells. Our results underscore a role for Aβ₄₂ in disrupting proteome responses for signaling, bioenergetics, and morphology in mitochondria. These findings highlight the specific components of the mitochondrial response during Aβ₄₂ neurotoxicity and suggest several new biomarkers for detection and surveillance of amyloid disease.