Alternative splicing in mouse brains affected by psychological stress is enriched in the signaling, neural transmission and blood-brain barrier pathways.

Psychological stress increases the risk of major psychiatric disorders. Psychological stress on mice was reported to induce differential gene expression (DEG) in mice brain regions. Alternative splicing is a fundamental aspect of gene expression and has been associated with psychiatric disorders but has not been investigated in the stressed brain yet. This study investigated changes in gene expression and splicing under psychological stress, the related pathways, and possible relationship with psychiatric disorders. RNA-seq raw data of 164 mouse brain samples from 3 independent datasets with stressors including chronic social defeat stress (CSDS), early life stress (ELS), and two-hit stress of combined CSDS and ELS were collected. There were more changes in splicing than in gene expression in the ventral hippocampus and medial prefrontal cortex, but stress-induced changes of individual genes by differential splicing and differential expression could not be replicated. In contrast, pathway analyses produced robust findings: stress-induced differentially spliced genes (DSGs) were reproducibly enriched in neural transmission and blood-brain barrier systems, and DEGs were reproducibly enriched in stress response-related functions. The hub genes of DSG-related PPI networks were enriched in synaptic functions. The corresponding human homologs of stress-induced DSGs were robustly enriched in AD-related DSGs as well as BD and SCZ in GWAS. These results suggested that stress-induced DSGs from different datasets belong to the same biological system throughout the stress response process, resulting in consistent stress response effects.

Integrative analyses prioritize GNL3 as a risk gene for bipolar disorder.

Genome-wide association studies (GWASs) have identified numerous single nucleotide polymorphisms (SNPs) associated with bipolar disorder (BD), but what the causal variants are and how they contribute to BD is largely unknown. In this study, we used FUMA, a GWAS annotation tool, to pinpoint potential causal variants and genes from the latest BD GWAS findings, and performed integrative analyses, including brain expression quantitative trait loci (eQTL), gene coexpression network, differential gene expression, protein-protein interaction, and brain intermediate phenotype association analysis to identify the functions of a prioritized gene and its connection to BD. Convergent lines of evidence prioritized protein-coding gene G Protein Nucleolar 3 (GNL3) as a BD risk gene, with integrative analyses revealing GNL3's roles in cell proliferation, neuronal functions, and brain phenotypes. We experimentally revealed that BD-related eQTL SNPs rs10865973, rs12635140, and rs4687644 regulate GNL3 expression using dual luciferase reporter assay and CRISPR interference experiment in human neural progenitor cells. We further identified that GNL3 knockdown and overexpression led to aberrant neuronal proliferation and differentiation, using two-dimensional human neural cell cultures and three-dimensional forebrain organoid model. This study gathers evidence that BD-related genetic variants regulate GNL3 expression which subsequently affects neuronal proliferation and differentiation.

Diallyl disulfide induces DNA damage and growth inhibition in colorectal cancer cells by promoting POU2F1 ubiquitination.

Previous studies have demonstrated that diallyl disulfide (DADS) exhibits potent anti-tumor activity. However, the pharmacological actions of DADS in inhibiting the growth of colorectal cancer (CRC) cells have not been clarified. Herein, we show that DADS treatment impairs the activation of the pentose phosphate pathway (PPP) to decrease PRPP (5-phosphate ribose-1-pyrophosphate) production, enhancing DNA damage and cell apoptosis, and inhibiting the growth of CRC cells. Mechanistically, DADS treatment promoted POU2F1 K48-linked ubiquitination and degradation by attenuating the PI3K/AKT signaling to up-regulate TRIM21 expression in CRC cells. Evidently, TRIM21 interacted with POU2F1, and induced the K272 ubiquitination of POU2F1. The effects of DADS on the enhanced K272 ubiquitination of POU2F1, the PPP flux, PRPP production, DNA damage and cell apoptosis as well as the growth of CRC tumors in vivo were significantly mitigated by TRIM21 silencing or activating the PI3K signaling in CRC cells. Conversely, the effects of DADS were enhanced by TRIM21 over-expression or inhibiting the PI3K/AKT signaling in CRC cells. Collectively, our findings reveal a novel mechanism by which DADS suppresses the growth of CRC by promoting POU2F1 ubiquitination, and may aid in design of novel therapeutic intervention of CRC.

Brain eQTLs of European, African American, and Asian ancestry improve interpretation of schizophrenia GWAS.

Research on brain expression quantitative trait loci (eQTLs) has illuminated the genetic underpinnings of schizophrenia (SCZ). Yet, the majority of these studies have been centered on European populations, leading to a constrained understanding of population diversities and disease risks. To address this gap, we examined genotype and RNA-seq data from African Americans (AA, n=158), Europeans (EUR, n=408), and East Asians (EAS, n=217). When comparing eQTLs between EUR and non-EUR populations, we observed concordant patterns of genetic regulatory effect, particularly in terms of the effect sizes of the eQTLs. However, 343,737 cis-eQTLs (representing ∼17% of all eQTLs pairs) linked to 1,276 genes (about 10% of all eGenes) and 198,769 SNPs (approximately 16% of all eSNPs) were identified only in the non-EUR populations. Over 90% of observed population differences in eQTLs could be traced back to differences in allele frequency. Furthermore, 35% of these eQTLs were notably rare (MAF < 0.05) in the EUR population. Integrating brain eQTLs with SCZ signals from diverse populations, we observed a higher disease heritability enrichment of brain eQTLs in matched populations compared to mismatched ones. Prioritization analysis identified seven new risk genes ( SFXN2 , RP11-282018.3 , CYP17A1 , VPS37B , DENR , FTCDNL1 , and NT5DC2 ), and three potential novel regulatory variants in known risk genes ( CNNM2 , C12orf65 , and MPHOSPH9 ) that were missed in the EUR dataset. Our findings underscore that increasing genetic ancestral diversity is more efficient for power improvement than merely increasing the sample size within single-ancestry eQTLs datasets. Such a strategy will not only improve our understanding of the biological underpinnings of population structures but also pave the way for the identification of novel risk genes in SCZ.

The Role of KDM2A and H3K36me2 Demethylation in Modulating MAPK Signaling During Neurodevelopment.

Intellectual disability (ID) is a condition characterized by cognitive impairment and difficulties in adaptive functioning. In our research, we identified two de novo mutations (c.955C>T and c.732C>A) at the KDM2A locus in individuals with varying degrees of ID. In addition, by using the Gene4Denovo database, we discovered five additional cases of de novo mutations in KDM2A. The mutations we identified significantly decreased the expression of the KDM2A protein. To investigate the role of KDM2A in neural development, we used both 2D neural stem cell models and 3D cerebral organoids. Our findings demonstrated that the reduced expression of KDM2A impairs the proliferation of neural progenitor cells (NPCs), increases apoptosis, induces premature neuronal differentiation, and affects synapse maturation. Through ChIP-Seq analysis, we found that KDM2A exhibited binding to the transcription start site regions of genes involved in neurogenesis. In addition, the knockdown of KDM2A hindered H3K36me2 binding to the downstream regulatory elements of genes. By integrating ChIP-Seq and RNA-Seq data, we made a significant discovery of the core genes' remarkable enrichment in the MAPK signaling pathway. Importantly, this enrichment was specifically linked to the p38 MAPK pathway. Furthermore, disease enrichment analysis linked the differentially-expressed genes identified from RNA-Seq of NPCs and cerebral organoids to neurodevelopmental disorders such as ID, autism spectrum disorder, and schizophrenia. Overall, our findings suggest that KDM2A plays a crucial role in regulating the H3K36me2 modification of downstream genes, thereby modulating the MAPK signaling pathway and potentially impacting early brain development.

Changes of immune-related factors in the blood of schizophrenia and bipolar disorder patients receiving monotherapy.

Schizophrenia (SCZ) and bipolar disorder (BPD) are associated with abnormal expression of immune-related factors (IRFs), which have been proposed as biomarkers of either disease diagnosis (trait markers) or treatment (state markers). However, the state markers have been found to be less reproducible than the trait markers in previous studies. In the current study, we focused on the changes of IRFs in blood of SCZ and BPD patients receiving monotherapy. SCZ (N = 49) and BPD (N = 49) Chinese patients were recruited at acute episode and followed for 9 to 51 days until remission. Blood samples were collected at two state-points, acute state before treatment and remission state after treatment. A total of 41 IRFs in plasma were quantified by the Luminex assay. After adjusting covariates, we found four cytokines or cytokine receptors were significantly increased at remission when compared to acute episode in all the patients, including CD30, BAFF, CCL20, and CXCL10 (Bonferroni corrected p < 0.05). CD30 and BAFF were consistently increased in both SCZ and BPD while the increase of CCL20 was only observed in BPD but not SCZ when analyzing the two disorders separately. CXCL10 change was not significant in either SCZ or BPD alone. The changes of these four factors were correlated with each other, but not with clinical features. CD30 concentration in the BPD acute state was correlated with sleep quality (Spearman's rs = 0.365, Bonferroni corrected p < 0.05). Overall, we found that four factors (CD30, BAFF, CCL20, and CXCL10) might be associated with treatment of psychosis.

Glioma cells are resistant to inflammation­induced alterations of mitochondrial dynamics.

Accumulating evidence suggests that inflammation is present in solid tumors. However, it is poorly understood whether inflammation exists in glioma and how it affects the metabolic signature of glioma. By analyzing immunohistochemical data and gene expression data downloaded from bioinformatic datasets, the present study revealed an accumulation of inflammatory cells in glioma, activation of microglia, upregulation of proinflammatory factors (including IL­6, IL­8, hypoxia­inducible factor­1α, STAT3, NF­κB1 and NF­κB2), destruction of mitochondrial structure and altered expression levels of electron transfer chain complexes and metabolic enzymes. By monitoring glioma cells following proinflammatory stimulation, the current study observed a remodeling of their mitochondrial network via mitochondrial fission. More than half of the mitochondria presented ring­shaped or spherical morphologies. Transmission electron microscopic analyses revealed mitochondrial swelling with partial or total cristolysis. Furthermore, proinflammatory stimuli resulted in increased generation of reactive oxygen species, decreased mitochondrial membrane potential and reprogrammed metabolism. The defective mitochondria were not eliminated via mitophagy. However, cell viability was not affected, and apoptosis was decreased in glioma cells after proinflammatory stimuli. Overall, the present findings suggested that inflammation may be present in glioma and that glioma cells may be resistant to inflammation­induced mitochondrial dysfunction.