Human Postmortem Brain Samples Research Articles

Antipsychotic-induced epigenomic reorganization in frontal cortex of individuals with schizophrenia

Genome-wide association studies have revealed >270 loci associated with schizophrenia risk, yet these genetic factors do not seem to be sufficient to fully explain the molecular determinants behind this psychiatric condition. Epigenetic marks such as post-translational histone modifications remain largely plastic during development and adulthood, allowing a dynamic impact of environmental factors, including antipsychotic medications, on access to genes and regulatory elements. However, few studies so far have profiled cell-specific genome-wide histone modifications in postmortem brain samples from schizophrenia subjects, or the effect of antipsychotic treatment on such epigenetic marks. Here, we conducted ChIP-seq analyses focusing on histone marks indicative of active enhancers (H3K27ac) and active promoters (H3K4me3), alongside RNA-seq, using frontal cortex samples from antipsychotic-free (AF) and antipsychotic-treated (AT) individuals with schizophrenia, as well as individually matched controls (n=58). Schizophrenia subjects exhibited thousands of neuronal and non-neuronal epigenetic differences at regions that included several susceptibility genetic loci, such as NRG1, DISC1, and DRD3. By analyzing the AF and AT cohorts separately, we identified schizophrenia-associated alterations in specific transcription factors, their regulatees, and epigenomic and transcriptomic features that were reversed by antipsychotic treatment; as well as those that represented a consequence of antipsychotic medication rather than a hallmark of schizophrenia in postmortem human brain samples. Notably, we also found that the effect of age on epigenomic landscapes was more pronounced in frontal cortex of AT-schizophrenics, as compared to AF-schizophrenics and controls. Together, these data provide important evidence of epigenetic alterations in the frontal cortex of individuals with schizophrenia, and remark for the first time on the impact of age and antipsychotic treatment on chromatin organization.

Neuronal-specific methylome and hydroxymethylome analysis reveal significant loci associated with alcohol use disorder.

Background: Alcohol use disorder (AUD) is a complex condition associated with adverse health consequences that affect millions of individuals worldwide. Epigenetic modifications, including DNA methylation (5mC), have been associated with AUD and other alcohol-related traits. Epigenome-wide association studies (EWAS) have identified differentially methylated genes associated with AUD in human peripheral and brain tissue. More recently, epigenetic studies of AUD have also evaluated DNA hydroxymethylation (5hmC) in the human brain. However, most of the epigenetic work in postmortem brain tissue has examined bulk tissue. In this study, we investigated neuronal-specific 5mC and 5hmC alterations at CpG sites associated with AUD in the human orbitofrontal cortex (OFC). Methods: Neuronal nuclei from the OFC were evaluated in 34 human postmortem brain samples (10 AUD, 24 non-AUD). Reduced representation oxidative bisulfite sequencing was used to assess 5mC and 5hmC at the genome-wide level. Differential 5mC and 5hmC were evaluated using the methylKit R package and significance was set at false discovery rate < 0.05 and differential methylation > 2. Functional enrichment analyses were performed, and gene-level convergence was evaluated in an independent dataset that assessed 5mC and 5hmC of AUD in bulk cortical tissue. Results: We identified 417 5mC and 3635hmC significant differential CpG sites associated with AUD, with 59% in gene promoters. Some of the identified genes have been previously implicated in alcohol consumption, including SYK, DNMT3A for 5mC, GAD1, DLX1, DLX2, for 5hmC and GATA4 in both. Convergence with a previous AUD 5mC and 5hmC study was observed for 28 genes. We also identified 5 and 35 differential regions for 5mC and 5hmC, respectively. Lastly, GWAS enrichment analysis showed an association with AUD for differential 5mC genes. Discussion: This study reveals neuronal-specific methylome and hydroxymethylome dysregulation associated with AUD, identifying both previously reported and potentially novel gene associations with AUD. Our findings provide new insights into the epigenomic dysregulation of AUD in the human brain.

α-Synuclein oligomers potentiate neuroinflammatory NF-κB activity and induce Cav3.2 calcium signaling in astrocytes

BackgroundIt is now realized that Parkinson’s disease (PD) pathology extends beyond the substantia nigra, affecting both central and peripheral nervous systems, and exhibits a variety of non-motor symptoms often preceding motor features. Neuroinflammation induced by activated microglia and astrocytes is thought to underlie these manifestations. α-Synuclein aggregation has been linked with sustained neuroinflammation in PD, aggravating neuronal degeneration; however, there is still a lack of critical information about the structural identity of the α-synuclein conformers that activate microglia and/or astrocytes and the molecular pathways involved.MethodsTo investigate the role of α-synuclein conformers in the development and maintenance of neuroinflammation, we used primary quiescent microglia and astrocytes, post-mortem brain tissues from PD patients and A53T α-synuclein transgenic mice that recapitulate key features of PD-related inflammatory responses in the absence of cell death, i.e., increased levels of pro-inflammatory cytokines and complement proteins. Biochemical and -omics techniques including RNAseq and secretomic analyses, combined with 3D reconstruction of individual astrocytes and live calcium imaging, were used to uncover the molecular mechanisms underlying glial responses in the presence of α-synuclein oligomers in vivo and in vitro.ResultsWe found that the presence of SDS-resistant hyper-phosphorylated α-synuclein oligomers, but not monomers, was correlated with sustained inflammatory responses, such as elevated levels of endogenous antibodies and cytokines and microglial activation. Similar oligomeric α-synuclein species were found in post-mortem human brain samples of PD patients but not control individuals. Detailed analysis revealed a decrease in Iba1Low/CD68Low microglia and robust alterations in astrocyte number and morphology including process retraction. Our data indicated an activation of the p38/ATF2 signaling pathway mostly in microglia and a sustained induction of the NF-κB pathway in astrocytes of A53T mice. The sustained NF-κB activity triggered the upregulation of astrocytic T-type Cav3.2 Ca2+ channels, altering the astrocytic secretome and promoting the secretion of IGFBPL1, an IGF-1 binding protein with anti-inflammatory and neuroprotective potential.ConclusionsOur work supports a causative link between the neuron-produced α-synuclein oligomers and sustained neuroinflammation in vivo and maps the signaling pathways that are stimulated in microglia and astrocytes. It also highlights the recruitment of astrocytic Cav3.2 channels as a potential neuroprotective mediator against the α-synuclein-induced neuroinflammation.Graphical

Molecular profiling of the hippocampus of children with autism spectrum disorder.

Several lines of evidence point to a key role of the hippocampus in Autism Spectrum Disorders (ASD). Altered hippocampal volume and deficits in memory for person and emotion related stimuli have been reported, along with enhanced ability for declarative memories. Mouse models have demonstrated a critical role of the hippocampus in social memory dysfunction, associated with ASD, together with decreased synaptic plasticity. Chondroitin sulfate proteoglycans (CSPGs), a family of extracellular matrix molecules, represent a potential key link between neurodevelopment, synaptic plasticity, and immune system signaling. There is a lack of information regarding the molecular pathology of the hippocampus in ASD. We conducted RNAseq profiling on postmortem human brain samples containing the hippocampus from male children with ASD (n = 7) and normal male children (3-14 yrs old), (n = 6) from the NIH NeuroBioBank. Gene expression profiling analysis implicated molecular pathways involved in extracellular matrix organization, neurodevelopment, synaptic regulation, and immune system signaling. qRT-PCR and Western blotting were used to confirm several of the top markers identified. The CSPG protein BCAN was examined with multiplex immunofluorescence to analyze cell-type specific expression of BCAN and astrocyte morphology. We observed decreased expression of synaptic proteins PSD95 (p < 0.02) and SYN1 (p < 0.02), increased expression of the extracellular matrix (ECM) protease MMP9 (p < 0.03), and decreased expression of MEF2C (p < 0.03). We also observed increased BCAN expression with astrocytes in children with ASD, together with altered astrocyte morphology. Our results point to alterations in immune system signaling, glia cell differentiation, and synaptic signaling in the hippocampus of children with ASD, together with alterations in extracellular matrix molecules. Furthermore, our results demonstrate altered expression of genes implicated in genetic studies of ASD including SYN1 and MEF2C.

The association between neuropsychiatric effects of substance use and occurrence of endoplasmic reticulum and unfolded protein response: A systematic review

IntroductionThis systematic review aimed to assess the association between neuropsychiatric effects of substance use and occurrence of ER stress and unfolded protein response (UPR) through comprehensive electronic search of existing literature and review of their findings. MethodsA comprehensive electronic literature search was carried out on research articles published between 1950 to July 2023 through major databases, such as Scopus, Web of Science, Google Scholar, PubMed, PsycINFO, EMBASE, Medline and Cochrane Library. ResultsA total of 21 research articles were selected for review, which were comprised of sixteen animal studies, four human studies and one study on postmortem human brain samples. The selected studies revealed that alcohol, methamphetamine, cocaine, opioid and kratom exposures contributed to neuropsychiatric effects: such as decline in learning and memory function, executive dysfunction, alcohol, methamphetamine, opioid, and kratom dependence. These effects were associated with activation and persistent of ER stress and UPR with elevation of BiP and CHOP expression and the direction of ER stress is progressing towards the PERK-eIF2α-ATF4-CHOP pathway and neuronal apoptosis and neurodegeneration at various regions of the brain. In addition, regular kratom use in humans also contributed to elevation of p-JNK expression, denoting progress of ER stress towards the IRE1-ASK1-JNK-p-JNK pathway which was linked to kratom use disorder. However, treatment with certain compounds or biological agents could reverse the activation of ER stress. ConclusionsThe neuropsychiatric effects of alcohol, methamphetamine, cocaine, opioid and kratom use may be associated with persistent ER stress and UPR.

Cholesterol accumulation promotes ABCA1 degradation in astrocytes via Caveolin‐1 mediated endocytosis in ApoE4

AbstractBackgroundApolipoprotein E4 (ApoE4) dysregulates cholesterol metabolism in the brain promoting the accumulation of lipid droplets, synaptic dysfunction and associates with a greater Alzheimer’s disease risk. We previously demonstrated that ApoE4 reduces the function of ATP‐binding cassette transporters A1 (ABCA1) which has important roles in cholesterol transport. The mechanisms of how ApoE4 induces less ABCA1 activity are poorly understood.MethodABCA1 binding proteins were analyzed with mass spectrum after immunoprecipitation. Immortalized astrocytes, primary astrocytes, mouse brain and human postmortem brain samples were used to test the association of ABCA1 and caveolin‐1 levels. Small interfere RNA was used to knockdown caveolin‐1 expression and 3H labelled cholesterol was used to test the cholesterol efflux of ABCA1.ResultHere, we enriched ABCA1 binding protein complexes from ABCA1‐overexpressing cells treated with recombinant ApoE3 or ApoE4 proteins for a proteomic screen implicating endocytosis as a major pathway differentiating ApoE3 from ApoE4. Among the protein targets discovered, caveolin‐1 expression increased after ApoE4 treatment. Caveolin‐1 and ABCA1 interactions were confirmed using immunoprecipitation experiments. Cholesterol accumulation in astrocytes induced caveolin‐1 expression and promoted ABCA1 degradation. Greater caveolin‐1 and lower ABCA1 expression was observed in brains of 8, 18 and 22 months‐old ApoE4‐TR mice compared with the corresponding ApoE3‐TR mice. Isolation of single cell types from adult mouse ApoE‐TR brains confirmed lower ABCA1 and greater caveolin‐1 expression was largely driven by astrocytes and not microglia or neurons enriched fractions.ConclusionIn conclusion, cholesterol accumulation induced by ApoE4 promotes ABCA1 degradation in astrocytes partly through a caveolin‐1 dependent endocytosis pathway.

Tpr Misregulation in Hippocampal Neural Stem Cells in Mouse Models of Alzheimer's Disease.

Nuclear pore complexes (NPCs) are highly dynamic macromolecular protein structures that facilitate molecular exchange across the nuclear envelope. Aberrant NPC functioning has been implicated in neurodegeneration. The translocated promoter region (Tpr) is a critical scaffolding nucleoporin (Nup) of the nuclear basket, facing the interior of the NPC. However, the role of Tpr in adult neural stem/precursor cells (NSPCs) in Alzheimer's disease (AD) is unknown. Using super-resolution (SR) and electron microscopy, we defined the different subcellular localizations of Tpr and phospho-Tpr (P-Tpr) in NSPCs in vitro and in vivo. Elevated Tpr expression and reduced P-Tpr nuclear localization accompany NSPC differentiation along the neurogenic lineage. In 5xFAD mice, an animal model of AD, increased Tpr expression in DCX+ hippocampal neuroblasts precedes increased neurogenesis at an early stage, before the onset of amyloid-β plaque formation. Whereas nuclear basket Tpr interacts with chromatin modifiers and NSPC-related transcription factors, P-Tpr interacts and co-localizes with cyclin-dependent kinase 1 (Cdk1) at the nuclear chromatin of NSPCs. In hippocampal NSPCs in a mouse model of AD, aberrant Tpr expression was correlated with altered NPC morphology and counts, and Tpr was aberrantly expressed in postmortem human brain samples from patients with AD. Thus, we propose that altered levels and subcellular localization of Tpr in CNS disease affect Tpr functionality, which in turn regulates the architecture and number of NSPC NPCs, possibly leading to aberrant neurogenesis.

Imaging and quantifying microglial activation in vivo and ex vivo using diffusion MRI – with validation by immunohistochemistry

AbstractBackgroundAlzheimer disease (AD) is the most common type of dementia.There is growing evidence that the amyloid plaques in postmortem AD human brains are surrounded by activated microglia. Using diffusion basis spectrum imaging (DBSI), we have previously observed increased cellular diffusivity in AD patients, suggesting increased microglia activation as a key pathology in AD. To better understand the underlying mechanism and further establish the noninvasive and nonradioactive DBSI biomarkers of microglia activation, we conducted a realistic Monte Carlo (MC) simulation to model diffusion MRI signals associated with microglia in various activation states.MethodFirst, realistic microglia diffusion signals were generated using MC simulation with real 3D microglia geometry obtained from neuromorpho.org (Fig. 1A). We simulated different pathophysiological scenarios to validate DBSI’s capability in quantitatively detecting microglia activation (Fig. 1B). Second, we conducted and ex vivo MRI scans on human postmortem AD brain samples, followed by immunohistochemical (IHC) staining of microglia (Iba‐1) in aligned sections from the same tissue. DBSI cell apparent diffusion coefficients (ADC), reflecting microglia activation, were estimated and compared to quantitative histological assessments of microglia activation. Finally, in vivo DBSI was conducted on 200 participants who were classified into healthy control, preclinical AD, and early symptomatic AD groups based on cognitive assessments and measures of CSF amyloid (Aβ42) and pTau181.ResultTwo exemplary regions in grey matter (GM) and white matter (WM) of a postmortem AD brain were selected (Fig. 1C). We found that GM had significantly higher DBSI‐derived cell ADC than WM (Fig. 1D). Iba‐1 IHC revealed that WM had significantly larger average microglial area (p&lt;0.005) and bigger max microglia larea (Fig. 1E‐F). MC Simulation was conducted on 700 microglia models. Microglial activation would result in an increased DBSI cell ADC (Fig. 1G). According to MC simulation, increased DBSI‐derived cell ADC in preclinical and early symptomatic AD indicated microglial activation in preclinical and early symptomatic AD (Fig. 1H).ConclusionDBSI‐derived cell ADC increases with microglial activation as assessed by quantitative Iba‐1 IHC. This finding is supported by MC simulation using real 3D microglia geometry. The study indicates that DBSI has the potential to provide non‐invasive MRI biomarkers of microglia activation.

Pseudo‐temporal models of Alzheimer’s Disease progression across brain‐derived transcriptomics, proteomics, and metabolomics

AbstractBackgroundWe applied a pseudo‐temporal model to multi‐omic data from individuals with heterogeneous neuropathology to examine molecular changes across the spectrum of Alzheimer’s Disease (AD) progression.MethodsManifold learning algorithms ‘order’ samples based on similarity of expression or abundance patterns to calculate a ‘trajectory’ of disease progression. We applied this approach to RNAseq (N = 1078), TMT‐proteomics (N = 602), and metabolomics (N = 500) profiles of human postmortem brain samples from the ROS/MAP study within the Accelerating Medicine Partnership‐AD consortia (AMP‐AD); 318 individuals were included in all three ‐omics datasets. Analyses were stratified by sex. We examined associations between pseudotime, a quantitative measure of progress along each trajectory, and neuropathological and clinical endpoints. We calculated differential expression or abundance along each trajectory. For transcriptomic and proteomic data, we used gene set enrichment analyses to identify significant GO terms changing along the trajectory and grouped them into 19 distinct AD‐relevant biological domains. We similarly annotated changing metabolic pathways along metabolomic trajectories.ResultsPseudotime estimates were significantly associated with AD status such that “early” (low pseudotime) samples were enriched for controls, and “late” (high pseudotime) samples were enriched for cases, in all ‐omics. Omic‐specific pseudotimes were weakly correlated with each other (Pearson’s r for: RNAseq vs proteomics: 0.39; RNAseq vs metabolomics: 0.28; proteomics vs metabolomics: 0.41). Proteins involved in mitochondrial metabolism and synaptic function were downregulated in early stages in both sexes, while transcriptomic trajectories indicated early sex‐specific differences in synaptic function and immune response. In both sexes, metabolic amino acid and lipid pathways were perturbed in early stages, though specific pathways were different; early Phosphatidylcholine and Leucine, Isoleucine, and Valine Metabolism perturbations were especially prominent in women, while early Glutathione Metabolism perturbations were more prominent in men.ConclusionsDespite differences in the biological nature of the data used to order trajectories, pseudotime was associated with multiple measures of AD progression across all three ‐omics. Each analysis provided a unique snapshot of molecular change across AD progression. Sex‐specific differences, especially those noted early in disease trajectories, may provide crucial insights into key processes driving disease in women and men.

Exploration of SUMO2/3 Expression Levels and Autophagy Process in Fragile X-Associated Tremor/Ataxia Syndrome: Addressing Study Limitations and Insights for Future Research.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that appears in adult FMR1 premutation carriers. The neuropathological hallmark of FXTAS is an intranuclear inclusion in neurons and astrocytes. Nearly 200 different proteins have been identified in FXTAS inclusions, being the small ubiquitin-related modifier 2 (SUMO2), ubiquitin and p62 the most highly abundant. These proteins are components of the protein degradation machinery. This study aimed to characterize SUMO2/3 expression levels and autophagy process in human postmortem brain samples and skin fibroblast cultures from FXTAS patients. Results revealed that FXTAS postmortem brain samples are positive for SUMO2/3 conjugates and supported the idea that SUMO2/3 accumulation is involved in inclusion formation. Insights from RNA-sequencing data indicated that SUMOylation processes are significantly upregulated in FXTAS samples. In addition, the analysis of the autophagy flux showed the accumulation of p62 protein levels and autophagosomes in skin fibroblasts from FXTAS patients. Similarly, gene set analysis evidenced a significant downregulation in gene ontology terms related to autophagy in FXTAS samples. Overall, this study provides new evidence supporting the role of SUMOylation and autophagic processes in the pathogenic mechanisms underlying FXTAS.

Measuring Up: A Comparison of TapeStation 4200 and Bioanalyzer 2100 as Measurement Tools for RNA Quality in Postmortem Human Brain Samples.

The determination of RNA integrity is a critical quality assessment tool for gene expression studies where the experiment's success is highly dependent on the sample quality. Since its introduction in 1999, the gold standard in the scientific community has been the Agilent 2100 Bioanalyzer's RNA integrity number (RIN), which uses a 1-10 value system, from 1 being the most degraded, to 10 being the most intact. In 2015, Agilent launched 4200 TapeStation's RIN equivalent, and reported a strong correlation of r2 of 0.936 and a median error < ±0.4 RIN units. To evaluate this claim, we compared the Agilent 4200 TapeStation's RIN equivalent (RINe) and DV200 to the Agilent 2100 Bioanalyzer's RIN for 183 parallel RNA samples. In our study, using RNA from a total of 183 human postmortem brain samples, we found that the RIN and RINe values only weakly correlate, with an r2 of 0.393 and an average difference of 3.2 RIN units. DV200 also only weakly correlated with RIN (r2 of 0.182) and RINe (r2 of 0.347). Finally, when applying a cut-off value of 6.5 for both metrics, we found that 95.6% of samples passed with RIN, while only 23.5% passed with RINe. Our results suggest that even though RIN (Bioanalyzer) and RINe (TapeStation) use the same 1-10 value system, they should not be used interchangeably, and cut-off values should be calculated independently.

Single-cell atlas reveals correlates of high cognitive function, dementia, and resilience to Alzheimer’s disease pathology

Alzheimer's disease (AD) is the most common cause of dementia worldwide, but the molecular and cellular mechanisms underlying cognitive impairment remain poorly understood. To address this, we generated a single-cell transcriptomic atlas of the aged human prefrontal cortex covering 2.3 million cells from postmortem human brain samples of 427 individuals with varying degrees of AD pathology and cognitive impairment. Our analyses identified AD-pathology-associated alterations shared between excitatory neuron subtypes, revealed a coordinated increase of the cohesin complex and DNA damage response factors in excitatory neurons and in oligodendrocytes, and uncovered genes and pathways associated with high cognitive function, dementia, and resilience to AD pathology. Furthermore, we identified selectively vulnerable somatostatin inhibitory neuron subtypes depleted in AD, discovered two distinct groups of inhibitory neurons that were more abundant in individuals with preserved high cognitive function late in life, and uncovered a link between inhibitory neurons and resilience to AD pathology.

Sex specific molecular networks and key drivers of Alzheimer’s disease

BackgroundAlzheimer’s disease (AD) is a progressive and age-associated neurodegenerative disorder that affects women disproportionally. However, the underlying mechanisms are poorly characterized. Moreover, while the interplay between sex and ApoE genotype in AD has been investigated, multi-omics studies to understand this interaction are limited. Therefore, we applied systems biology approaches to investigate sex-specific molecular networks of AD.MethodsWe integrated large-scale human postmortem brain transcriptomic data of AD from two cohorts (MSBB and ROSMAP) via multiscale network analysis and identified key drivers with sexually dimorphic expression patterns and/or different responses to APOE genotypes between sexes. The expression patterns and functional relevance of the top sex-specific network driver of AD were further investigated using postmortem human brain samples and gene perturbation experiments in AD mouse models.ResultsGene expression changes in AD versus control were identified for each sex. Gene co-expression networks were constructed for each sex to identify AD-associated co-expressed gene modules shared by males and females or specific to each sex. Key network regulators were further identified as potential drivers of sex differences in AD development. LRP10 was identified as a top driver of the sex differences in AD pathogenesis and manifestation. Changes of LRP10 expression at the mRNA and protein levels were further validated in human AD brain samples. Gene perturbation experiments in EFAD mouse models demonstrated that LRP10 differentially affected cognitive function and AD pathology in sex- and APOE genotype-specific manners. A comprehensive mapping of brain cells in LRP10 over-expressed (OE) female E4FAD mice suggested neurons and microglia as the most affected cell populations. The female-specific targets of LRP10 identified from the single cell RNA-sequencing (scRNA-seq) data of the LRP10 OE E4FAD mouse brains were significantly enriched in the LRP10-centered subnetworks in female AD subjects, validating LRP10 as a key network regulator of AD in females. Eight LRP10 binding partners were identified by the yeast two-hybrid system screening, and LRP10 over-expression reduced the association of LRP10 with one binding partner CD34.ConclusionsThese findings provide insights into key mechanisms mediating sex differences in AD pathogenesis and will facilitate the development of sex- and APOE genotype-specific therapies for AD.

Increased pituitary adenylate cyclase-activating polypeptide in the central bed nucleus of the stria terminalis in mood disorders in men

The mood disorders major depressive disorder (MDD) and bipolar disorder (BD) are highly prevalent worldwide. Women are more vulnerable to these psychopathologies than men. The bed nucleus of the stria terminalis (BNST), the amygdala, and the hypothalamus are the crucial interconnected structures involved in the stress response. In mood disorders, stress systems in the brain are put into a higher gear. The BNST is implicated in mood, anxiety, and depression. The stress-related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is highly abundant in the central BNST (cBNST). In this study, we investigated alterations in PACAP in the cBNST of patients with mood disorders. Immunohistochemical (IHC) staining of PACAP and in situ hybridization (ISH) of PACAP mRNA were performed on the cBNST of post-mortem human brain samples. Quantitative IHC revealed elevated PACAP levels in the cBNST in both mood disorders, MDD and BD, but only in men, not in women. The PACAP ISH was negative, indicating that PACAP is not produced in the cBNST. The results support the possibility that PACAP innervation of the cBNST plays a role in mood disorder pathophysiology in men.

JNK3 Overexpression in the Entorhinal Cortex Impacts on the Hippocampus and Induces Cognitive Deficiencies and Tau Misfolding.

c-Jun N-terminal kinases (JNKs) are a family of protein kinases activated by a myriad of stimuli consequently modulating a vast range of biological processes. In human postmortem brain samples affected with Alzheimer's disease (AD), JNK overactivation has been described; however, its role in AD onset and progression is still under debate. One of the earliest affected areas in the pathology is the entorhinal cortex (EC). Noteworthy, the deterioration of the projection from EC to hippocampus (Hp) point toward the idea that the connection between EC and Hp is lost in AD. Thus, the main objective of the present work is to address if JNK3 overexpression in the EC could impact on the hippocampus, inducing cognitive deficits. Data obtained in the present work suggest that JNK3 overexpression in the EC influences the Hp leading to cognitive impairment. Moreover, proinflammatory cytokine expression and Tau immunoreactivity were increased both in the EC and in the Hp. Therefore, activation of inflammatory signaling and induction of Tau aberrant misfolding caused by JNK3 could be responsible for the observed cognitive impairment. Altogether, JNK3 overexpression in the EC may impact on the Hp inducing cognitive dysfunction and underlie the alterations observed in AD.

Senescence-related impairment of autophagy induces toxic intraneuronal amyloid-β accumulation in a mouse model of amyloid pathology

Aging is the main risk factor for Alzheimer’s disease (AD) and other neurodegenerative pathologies, but the molecular and cellular changes underlying pathological aging of the nervous system are poorly understood. AD pathology seems to correlate with the appearance of cells that become senescent due to the progressive accumulation of cellular insults causing DNA damage. Senescence has also been shown to reduce the autophagic flux, a mechanism involved in clearing damaged proteins from the cell, and such impairment has been linked to AD pathogenesis. In this study, we investigated the role of cellular senescence on AD pathology by crossing a mouse model of AD-like amyloid-β (Aβ) pathology (5xFAD) with a mouse model of senescence that is genetically deficient for the RNA component of the telomerase (Terc−/−). We studied changes in amyloid pathology, neurodegeneration, and the autophagy process in brain tissue samples and primary cultures derived from these mice by complementary biochemical and immunostaining approaches. Postmortem human brain samples were also processed to evaluate autophagy defects in AD patients. Our results show that accelerated senescence produces an early accumulation of intraneuronal Aβ in the subiculum and cortical layer V of 5xFAD mice. This correlates with a reduction in amyloid plaques and Aβ levels in connecting brain regions at a later disease stage. Neuronal loss was specifically observed in brain regions presenting intraneuronal Aβ and was linked to telomere attrition. Our results indicate that senescence affects intraneuronal Aβ accumulation by impairing autophagy function and that early autophagy defects can be found in the brains of AD patients. Together, these findings demonstrate the instrumental role of senescence in intraneuronal Aβ accumulation, which represents a key event in AD pathophysiology, and emphasize the correlation between the initial stages of amyloid pathology and defects in the autophagy flux.

Enduring Controversial Story in the Human Brain

Adult hippocampal neurogenesis (AHN) is a well-studied phenomenon that involves the derivation of new neurons from neural progenitor cells in the dentate gyrus region of the hippocampus, an area responsible for cognitive functions such as learning and memory storage. Moreover, the hippocampus is known to be implicated in neurological conditions such as Alzheimer's disease. Although AHN has been extensively observed in animal models for twenty years, its existence and persistence in humans have been widely debated in academia, heavily based on post-mortem immunohistochemical markers. Using the search engines PubMed and Google Scholar for “Adult Human Neurogenesis,” 143 articles that were most relevant to the history of AHN discovery, detection in rodents, immunohistochemical studies on post-mortem human sections, and therapeutic development targeting AHN were reviewed. This review article highlights the current understanding of AHN in rodents and humans, its implications in neurodegenerative diseases and therapeutics, and the inconsistencies and methodological variabilities encountered in studying AHN in humans. Furthermore, the correlation between AHN and diseases such as mood disorders and Alzheimer's disease is still not well established, with conflicting findings reported. Standardization of transcriptomic methodologies and increased availability of post-mortem human brain samples are crucial in advancing AHN research. This review article attempts to discover the fascinating and controversial world of adult human neurogenesis and its potential implications in treating neurological disorders. Apart from the discussion on AHN existence, tackling devastating diseases with this supplemental knowledge can lead to therapeutic advancements which greatly rely on understanding not only the presence of AHN but the mechanisms mediating its availability.

Astrocytes display ultrastructural alterations and heterogeneity in the hippocampus of aged APP-PS1 mice and human post-mortem brain samples

The past decade has witnessed increasing evidence for a crucial role played by glial cells, notably astrocytes, in Alzheimer’s disease (AD). To provide novel insights into the roles of astrocytes in the pathophysiology of AD, we performed a quantitative ultrastructural characterization of their intracellular contents and parenchymal interactions in an aged mouse model of AD pathology, as aging is considered the main risk factor for developing AD. We compared 20-month-old APP-PS1 and age-matched C57BL/6J male mice, among the ventral hippocampus CA1 strata lacunosum-moleculare and radiatum, two hippocampal layers severely affected by AD pathology. Astrocytes in both layers interacted more with synaptic elements and displayed more ultrastructural markers of increased phagolysosomal activity in APP-PS1 versus C57BL6/J mice. In addition, we investigated the ultrastructural heterogeneity of astrocytes, describing in the two examined layers a dark astrocytic state that we characterized in terms of distribution, interactions with AD hallmarks, and intracellular contents. This electron-dense astrocytic state, termed dark astrocytes, was observed throughout the hippocampal parenchyma, closely associated with the vasculature, and possessed several ultrastructural markers of cellular stress. A case study exploring the hippocampal head of an aged human post-mortem brain sample also revealed the presence of a similar electron-dense, dark astrocytic state. Overall, our study provides the first ultrastructural quantitative analysis of astrocytes among the hippocampus in aged AD pathology, as well as a thorough characterization of a dark astrocytic state conserved from mouse to human.

Genome-wide landscape of RNA-binding protein (RBP) networks as potential molecular regulators of psychiatric co-morbidities: a computational analysis

BackgroundPsychiatric disorders are a major burden on global health. These illnesses manifest as co-morbid conditions, further complicating the treatment. There is a limited understanding of the molecular and regulatory basis of psychiatric co-morbidities. The existing research in this regard has largely focused on epigenetic modulators, non-coding RNAs, and transcription factors. RNA-binding proteins (RBPs) functioning as multi-protein complexes are now known to be predominant controllers of multiple gene regulatory processes. However, their involvement in gene expression dysregulation in psychiatric co-morbidities is yet to be understood.ResultsTen RBPs (QKI, ELAVL2, EIF2S1, SRSF3, IGF2BP2, EIF4B, SNRNP70, FMR1, DAZAP1, and MBNL1) were identified to be associated with psychiatric disorders such as schizophrenia, major depression, and bipolar disorders. Analysis of transcriptomic changes in response to individual depletion of these RBPs showed the potential influence of a large number of RBPs driving differential gene expression, suggesting functional cross-talk giving rise to multi-protein networks. Subsequent transcriptome analysis of post-mortem human brain samples from diseased and control individuals also suggested the involvement of ~ 100 RBPs influencing gene expression changes. These RBPs were found to regulate various processes including transcript splicing, mRNA transport, localization, stability, and translation. They were also found to form an extensive interactive network. Further, hnRNP, SRSF, and PCBP family RBPs, Matrin3, U2AF2, KHDRBS1, PTBP1, and also PABPN1 were found to be the hub proteins of the RBP network.ConclusionsExtensive RBP networks involving a few hub proteins could result in transcriptome-wide dysregulation of post-transcriptional modifications, potentially driving multiple psychiatric disorders. Understanding the functional involvement of RBP networks in psychiatric disorders would provide insights into the molecular basis of psychiatric co-morbidities.

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?

New unexpected role for Wolfram Syndrome protein WFS1: a novel therapeutic target for Alzheimer's disease?