Coexpression networks identify brain region-specific enhancer RNAs in the human brain

Transcriptional enhancers in human neuronal differentiation provide clues to neuronal disorders

Genome-wide association studies (GWASs) have identified thousands of variants associated with complex phenotypes, including neuropsychiatric disorders. To better understand their pathogenesis, it is necessary to identify the functional roles of these variants, which are largely located in non-coding DNA regions. Here, we employ a human mesencephalic neuronal cell differentiation model, LUHMES, with sensitive and high-resolution methods to discover enhancers (NET-CAGE), perform DNA conformation analysis (Capture Hi-C) to link enhancers to their target genes, and finally validate selected interactions. We expand the number of known enhancers active in differentiating human LUHMES neurons to 47,350, and find overlap with GWAS variants for Parkinson's disease and schizophrenia. Our findings reveal a fine-tuned regulation of human neuronal differentiation, even between adjacent developmental stages; provide a valuable resource for further studies on neuronal development, regulation, and disorders; and emphasize the importance of exploring the vast regulatory potential of non-coding DNA and enhancers.

eRNA-IDO: A One-stop Platform for Identification, Interactome Discovery, and Functional Annotation of Enhancer RNAs

Growing evidence supports the transcription of enhancer RNAs (eRNAs) and their important roles in gene regulation. However, their interactions with other biomolecules and their corresponding functionality remain poorly understood. In an attempt to facilitate mechanistic research, this study presents eRNA-IDO, the first integrative computational platform for the identification, interactome discovery, and functional annotation of human eRNAs. eRNA-IDO comprises two modules: eRNA-ID and eRNA-Anno. Functionally, eRNA-ID can identify eRNAs from de novo assembled transcriptomes. eRNA-ID includes eight kinds of enhancer makers, enabling users to customize enhancer regions flexibly and conveniently. In addition, eRNA-Anno provides cell-/tissue-specific functional annotation for both new and known eRNAs by analyzing the eRNA interactome from prebuilt or user-defined networks between eRNAs and protein-coding genes. The prebuilt networks include the Genotype-Tissue Expression (GTEx)-based co-expression networks in normal tissues, The Cancer Genome Atlas (TCGA)-based co-expression networks in cancer tissues, and omics-based eRNA-centric regulatory networks. eRNA-IDO can facilitate research on the biogenesis and functions of eRNAs. The eRNA-IDO server is freely available at http://bioinfo.szbl.ac.cn/eRNA_IDO/.

Genome-wide enhancer RNA profiling adds molecular links between genetic variation and human cancers

BACKGROUND

Dysregulation of enhancer transcription occurs in multiple cancers. Enhancer RNAs (eRNAs) are transcribed products from enhancers that play critical roles in transcriptional control. Characterizing the genetic basis of eRNA expression may elucidate the molecular mechanisms underlying cancers.

METHODS

Initially, a comprehensive analysis of eRNA quantitative trait loci (eRNAQTLs) was performed in The Cancer Genome Atlas (TCGA), and functional features were characterized using multi-omics data. To establish the first eRNAQTL profiles for colorectal cancer (CRC) in China, epigenomic data were used to define active enhancers, which were subsequently integrated with transcription and genotyping data from 154 paired CRC samples. Finally, large-scale case-control studies (34,585 cases and 69,544 controls) were conducted along with multipronged experiments to investigate the potential mechanisms by which candidate eRNAQTLs affect CRC risk.

RESULTS

A total of 300,112 eRNAQTLs were identified across 30 different cancer types, which exert their influence on eRNA transcription by modulating chromatin status, binding affinity to transcription factors and RNA-binding proteins. These eRNAQTLs were found to be significantly enriched in cancer risk loci, explaining a substantial proportion of cancer heritability. Additionally, tumor-specific eRNAQTLs exhibited high responsiveness to the development of cancer. Moreover, the target genes of these eRNAs were associated with dysregulated signaling pathways and immune cell infiltration in cancer, highlighting their potential as therapeutic targets. Furthermore, multiple ethnic population studies have confirmed that an eRNAQTL rs3094296-T variant decreases the risk of CRC in populations from China (OR = 0.91, 95%CI 0.88-0.95, P = 2.92 × 10-7) and Europe (OR = 0.92, 95%CI 0.88-0.95, P = 4.61 × 10-6). Mechanistically, rs3094296 had an allele-specific effect on the transcription of the eRNA ENSR00000155786, which functioned as a transcriptional activator promoting the expression of its target gene SENP7. These two genes synergistically suppressed tumor cell proliferation. Our curated list of variants, genes, and drugs has been made available in CancereRNAQTL ( http://canernaqtl.whu.edu.cn/#/ ) to serve as an informative resource for advancing this field.

CONCLUSION

Our findings underscore the significance of eRNAQTLs in transcriptional regulation and disease heritability, pinpointing the potential of eRNA-based therapeutic strategies in cancers.

An Emerging Role for Enhancer RNAs in Brain Disorders

Noncoding DNA undergoes widespread context-dependent transcription to produce noncoding RNAs. In recent decades, tremendous advances in genomics and transcriptomics have revealed important regulatory roles for noncoding DNA elements and the RNAs that they produce. Enhancers are one such element that are well-established drivers of gene expression changes in response to a variety of factors such as external stimuli, cellular responses, developmental cues, and disease states. They are known to act at long distances, interact with multiple target gene loci simultaneously, synergize with other enhancers, and associate with dynamic chromatin architectures to form a complex regulatory network. Recent advances in enhancer biology have revealed that upon activation, enhancers transcribe long noncoding RNAs, known as enhancer RNAs (eRNAs), that have been shown to play important roles in enhancer-mediated gene regulation and chromatin-modifying activities. In the brain, enhancer dysregulation and eRNA transcription has been reported in numerous disorders from acute injuries to chronic neurodegeneration. Because this is an emerging area, a comprehensive understanding of eRNA function has not yet been achieved in brain disorders; however, the findings to date have illuminated a role for eRNAs in activity-driven gene expression and phenotypic outcomes. In this review, we highlight the breadth of the current literature on eRNA biology in brain health and disease and discuss the challenges as well as focus areas and strategies for future in-depth research on eRNAs in brain health and disease.

Molecular mechanisms of microbiome modulation by the eukaryotic secondary metabolite azelaic acid

Photosynthetic eukaryotes, such as microalgae and plants, foster fundamentally important relationships with their microbiome based on the reciprocal exchange of chemical currencies. Among these, the dicarboxylate metabolite azelaic acid (Aze) appears to play an important, but heterogeneous, role in modulating these microbiomes, as it is used as a carbon source for some heterotrophs but is toxic to others. However, the ability of Aze to promote or inhibit growth, as well as its uptake and assimilation mechanisms into bacterial cells are mostly unknown. Here, we use transcriptomics, transcriptional factor coexpression networks, uptake experiments, and metabolomics to unravel the uptake, catabolism, and toxicity of Aze on two microalgal-associated bacteria, Phycobacter and Alteromonas, whose growth is promoted or inhibited by Aze, respectively. We identify the first putative Aze transporter in bacteria, a 'C4-TRAP transporter', and show that Aze is assimilated through fatty acid degradation, with further catabolism occurring through the glyoxylate and butanoate metabolism pathways when used as a carbon source. Phycobacter took up Aze at an initial uptake rate of 3.8×10-9 nmol/cell/hr and utilized it as a carbon source in concentrations ranging from 10 μM to 1 mM, suggesting a broad range of acclimation to Aze availability. For growth-impeded bacteria, we infer that Aze inhibits the ribosome and/or protein synthesis and that a suite of efflux pumps is utilized to shuttle Aze outside the cytoplasm. We demonstrate that seawater amended with Aze becomes enriched in bacterial families that can catabolize Aze, which appears to be a different mechanism from that in soil, where modulation by the host plant is required. This study enhances our understanding of carbon cycling in the oceans and how microscale chemical interactions can structure marine microbial populations. In addition, our findings unravel the role of a key chemical currency in the modulation of eukaryote-microbiome interactions across diverse ecosystems.

eRNAbase: a comprehensive database for decoding the regulatory eRNAs in human and mouse

Enhancer RNAs (eRNAs) transcribed from distal active enhancers serve as key regulators in gene transcriptional regulation. The accumulation of eRNAs from multiple sequencing assays has led to an urgent need to comprehensively collect and process these data to illustrate the regulatory landscape of eRNAs. To address this need, we developed the eRNAbase (http://bio.liclab.net/eRNAbase/index.php) to store the massive available resources of human and mouse eRNAs and provide comprehensive annotation and analyses for eRNAs. The current version of eRNAbase cataloged 10 399 928 eRNAs from 1012 samples, including 858 human samples and 154 mouse samples. These eRNAs were first identified and uniformly processed from 14 eRNA-related experiment types manually collected from GEO/SRA and ENCODE. Importantly, the eRNAbase provides detailed and abundant (epi)genetic annotations in eRNA regions, such as super enhancers, enhancers, common single nucleotide polymorphisms, expression quantitative trait loci, transcription factor binding sites, CRISPR/Cas9 target sites, DNase I hypersensitivity sites, chromatin accessibility regions, methylation sites, chromatin interactions regions, topologically associating domains and RNA spatial interactions. Furthermore, the eRNAbase provides users with three novel analyses including eRNA-mediated pathway regulatory analysis, eRNA-based variation interpretation analysis and eRNA-mediated TF-target gene analysis. Hence, eRNAbase is a powerful platform to query, browse and visualize regulatory cues associated with eRNAs.

Possible roles of deep cortical neurons and oligodendrocytes in the neural basis of human sociality

Sociality is an instinctive property of organisms that live in relation to others and is a complex characteristic of higher order brain functions. However, the evolution of the human brain to acquire higher order brain functions, such as sociality, and the neural basis for executing these functions and their control mechanisms are largely unknown. Several studies have attempted to evaluate how human sociality was acquired during the course of evolution and the mechanisms controlling sociality from a neurodevelopment viewpoint. This review discusses these findings in the context of human brain evolution and the pathophysiology of autism spectrum disorder (ASD). Comparative genomic studies of postmortem primate brains have demonstrated human-specific regulatory mechanisms underlying higher order brain functions, providing evidence for the contribution of oligodendrocytes to human brain function. Functional analyses of the causative genes of ASD in animal models have demonstrated that the neural basis of social behavior is associated with layer 6 (L6) of the neocortex and oligodendrocytes. These findings demonstrate that both neurons and oligodendrocytes contribute to the neural basis and molecular mechanisms underlying human brain evolution and social functioning. This review provides novel insights into sociability and the corresponding neural bases of brain disorders and evolution.

Epigenetic changes in sperm are associated with paternal and child quantitative autistic traits in an autism-enriched cohort

There is a need to consider paternal contributions to autism spectrum disorder (ASD) more strongly. Autism etiology is complex, and heritability is not explained by genetics alone. Understanding paternal gametic epigenetic contributions to autism could help fill this knowledge gap. In the present study, we explored whether paternal autistic traits, and the sperm epigenome, were associated with autistic traits in children at 36 months enrolled in the Early Autism Risk Longitudinal Investigation (EARLI) cohort. EARLI is a pregnancy cohort that recruited and enrolled pregnant women in the first half of pregnancy who already had a child with ASD. After maternal enrollment, EARLI fathers were approached and asked to provide a semen specimen. Participants were included in the present study if they had genotyping, sperm methylation data, and Social Responsiveness Scale (SRS) score data available. Using the CHARM array, we performed genome-scale methylation analyses on DNA from semen samples contributed by EARLI fathers. The SRS-a 65-item questionnaire measuring social communication deficits on a quantitative scale-was used to evaluate autistic traits in EARLI fathers (n = 45) and children (n = 31). We identified 94 significant child SRS-associated differentially methylated regions (DMRs), and 14 significant paternal SRS-associated DMRs (fwer p < 0.05). Many child SRS-associated DMRs were annotated to genes implicated in ASD and neurodevelopment. Six DMRs overlapped across the two outcomes (fwer p < 0.1), and, 16 DMRs overlapped with previous child autistic trait findings at 12 months of age (fwer p < 0.05). Child SRS-associated DMRs contained CpG sites independently found to be differentially methylated in postmortem brains of individuals with and without autism. These findings suggest paternal germline methylation is associated with autistic traits in 3-year-old offspring. These prospective results for autism-associated traits, in a cohort with a family history of ASD, highlight the potential importance of sperm epigenetic mechanisms in autism.

Enhancer RNAs: mechanisms in transcriptional regulation and functions in diseases

In recent years, increasingly more non-coding RNAs have been detected with the development of high-throughput sequencing technology, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), small nucleolar RNAs (snoRNAs), and piwi-interacting RNA (piRNAs). The discovery of enhancer RNAs (eRNAs) in 2010 has further broadened the range of non-coding RNAs revealed. eRNAs are non-coding RNA molecules produced by the transcription of DNA cis-acting elements, enhancer fragments. Recent studies revealed that the transcription of eRNAs may be a biological marker responding to enhancer activity that can participate in the regulation of coding gene transcription. In this review, we discussed the biological characteristics of eRNAs, their functions in transcriptional regulation, the regulation factors of eRNAs production, and the research progress of eRNAs in different diseases. Video Abstract.

Noncoding transcripts are linked to brain resting-state activity in non-human primates

Brain-derived transcriptomes are known to correlate with resting-state brain activity in humans. Whether this association holds in nonhuman primates remains uncertain. Here, we search for such molecular correlates by integrating 757 transcriptomes derived from 100 macaque cortical regions with resting-state activity in separate conspecifics. We observe that 150 noncoding genes explain variations in resting-state activity at a comparable level with protein-coding genes. In-depth analysis of these noncoding genes reveals that they are connected to the function of nonneuronal cells such as oligodendrocytes. Co-expression network analysis finds that the modules of noncoding genes are linked to both autism and schizophrenia risk genes. Moreover, genes associated with resting-state noncoding genes are highly enriched in human resting-state functional genes and memory-effect genes, and their links with resting-state functional magnetic resonance imaging (fMRI) signals are altered in the brains of patients with autism. Our results highlight the potential for noncoding RNAs to explain resting-state activity in the nonhuman primate brain.

Identification and characterization of transcribed enhancers during cerebellar development through enhancer RNA analysis

BACKGROUND

The development of the brain requires precise coordination of molecular processes across many cell-types. Underpinning these events are gene expression programs which require intricate regulation by non-coding regulatory sequences known as enhancers. In the context of the developing brain, transcribed enhancers (TEs) regulate temporally-specific expression of genes critical for cell identity and differentiation. Transcription of non-coding RNAs at active enhancer sequences, known as enhancer RNAs (eRNAs), is tightly associated with enhancer activity and has been correlated with target gene expression. TEs have been characterized in a multitude of developing tissues, however their regulatory role has yet to be described in the context of embryonic and early postnatal brain development. In this study, eRNA transcription was analyzed to identify TEs active during cerebellar development, as a proxy for the developing brain. Cap Analysis of Gene Expression followed by sequencing (CAGE-seq) was conducted at 12 stages throughout embryonic and early postnatal cerebellar development.

RESULTS

Temporal analysis of eRNA transcription identified clusters of TEs that peak in activity during either embryonic or postnatal times, highlighting their importance for temporally specific developmental events. Functional analysis of putative target genes identified molecular mechanisms under TE regulation revealing that TEs regulate genes involved in biological processes specific to neurons. We validate enhancer activity using in situ hybridization of eRNA expression from TEs predicted to regulate Nfib, a gene critical for cerebellar granule cell differentiation.

CONCLUSIONS

The results of this analysis provide a valuable dataset for the identification of cerebellar enhancers and provide insight into the molecular mechanisms critical for brain development under TE regulation. This dataset is shared with the community through an online resource ( https://goldowitzlab.shinyapps.io/trans-enh-app/ ).

Insights into Enhancer RNAs: Biogenesis and Emerging Role in Brain Diseases

Enhancers are cis-acting elements that control the transcription of target genes and are transcribed into a class of noncoding RNAs (ncRNAs) termed enhancer RNAs (eRNAs). eRNAs have shorter half-lives than mRNAs and long noncoding RNAs; however, the frequency of transcription of eRNAs is close to that of mRNAs. eRNA expression is associated with a high level of histone mark H3K27ac and a low level of H3K27me3. Although eRNAs only account for a small proportion of ncRNAs, their functions are important. eRNAs can not only increase enhancer activity by promoting the formation of enhancer-promoter loops but also regulate transcriptional activation. Increasing numbers of studies have found that eRNAs play an important role in the occurrence and development of brain diseases; however, further research into eRNAs is required. This review discusses the concept, characteristics, classification, function, and potential roles of eRNAs in brain diseases.

Alzheimer's Disease: From Immune Homeostasis to Neuroinflammatory Condition

Alzheimer's Disease is the most common cause in the world of progressive cognitive decline. Although many modifiable and non-modifiable risk factors have been proposed, in recent years, neuroinflammation has been hypothesized to be an important contributing factor of Alzheimer's Disease pathogenesis. Neuroinflammation can occur through the combined action of the Central Nervous System resident immune cells and adaptive peripheral immune system. In the past years, immunotherapies for neurodegenerative diseases have focused wrongly on targeting protein aggregates Aβ plaques and NFT treatment. The role of both innate and adaptive immune cells has not been fully clarified, but several data suggest that immune system dysregulation plays a key role in neuroinflammation. Recent studies have focused especially on the role of the adaptive immune system and have shown that inflammatory markers are characterized by increased CD4+ Teff cells' activities and reduced circulating CD4+ Treg cells. In this review, we discuss the key role of both innate and adaptive immune systems in the degeneration and regeneration mechanisms in the pathogenesis of Alzheimer's Disease, with a focus on how the crosstalk between these two systems is able to sustain brain homeostasis or shift it to a neurodegenerative condition.

Population-level variation in enhancer expression identifies disease mechanisms in the human brain

Identification of risk variants for neuropsychiatric diseases within enhancers underscores the importance of understanding population-level variation in enhancer function in the human brain. Besides regulating tissue-specific and cell-type-specific transcription of target genes, enhancers themselves can be transcribed. By jointly analyzing large-scale cell-type-specific transcriptome and regulome data, we cataloged 30,795 neuronal and 23,265 non-neuronal candidate transcribed enhancers. Examination of the transcriptome in 1,382 brain samples identified robust expression of transcribed enhancers. We explored gene-enhancer coordination and found that enhancer-linked genes are strongly implicated in neuropsychiatric disease. We identified expression quantitative trait loci (eQTLs) for both genes and enhancers and found that enhancer eQTLs mediate a substantial fraction of neuropsychiatric trait heritability. Inclusion of enhancer eQTLs in transcriptome-wide association studies enhanced functional interpretation of disease loci. Overall, our study characterizes the gene-enhancer regulome and genetic mechanisms in the human cortex in both healthy and diseased states.

Temporal analysis of enhancers during mouse cerebellar development reveals dynamic and novel regulatory functions

We have identified active enhancers in the mouse cerebellum at embryonic and postnatal stages which provides a view of novel enhancers active during cerebellar development. The majority of cerebellar enhancers have dynamic activity between embryonic and postnatal development. Cerebellar enhancers were enriched for neural transcription factor binding sites with temporally specific expression. Putative gene targets displayed spatially restricted expression patterns, indicating cell-type specific expression regulation. Functional analysis of target genes indicated that enhancers regulate processes spanning several developmental epochs such as specification, differentiation and maturation. We use these analyses to discover one novel regulator and one novel marker of cerebellar development: Bhlhe22 and Pax3, respectively. We identified an enrichment of de novo mutations and variants associated with autism spectrum disorder in cerebellar enhancers. Furthermore, by comparing our data with relevant brain development ENCODE histone profiles and cerebellar single-cell datasets we have been able to generalize and expand on the presented analyses, respectively. We have made the results of our analyses available online in the Developing Mouse Cerebellum Enhancer Atlas (https://goldowitzlab.shinyapps.io/developing_mouse_cerebellum_enhancer_atlas/), where our dataset can be efficiently queried, curated and exported by the scientific community to facilitate future research efforts. Our study provides a valuable resource for studying the dynamics of gene expression regulation by enhancers in the developing cerebellum and delivers a rich dataset of novel gene-enhancer associations providing a basis for future in-depth studies in the cerebellum.

Genomic Strategies for Understanding the Pathophysiology of Autism Spectrum Disorder

Recent breakthroughs in sequencing technology and technological developments have made it easier to analyze the entire human genome than ever before. In addition to disease-specific genetic mutations and chromosomal aberrations, epigenetic alterations in individuals can also be analyzed using genomics. Autism spectrum disorder (ASD) is a neurodevelopmental disorder (NDD) caused by genetic and/or environmental factors. More than a thousand genes associated with ASD have been identified which are known to be involved in brain development. However, it is difficult to decode the roles of ASD-associated genes without in vitro and in vivo validations, particularly in the process of brain development. In this review, we discuss genomic strategies for understanding the pathological mechanisms underlying ASD. For this purpose, we discuss ASD-associated genes and their functions, as well as analytical strategies and their strengths and weaknesses in cellular and animal models from a basic research perspective.

Evolution of the Human Brain Can Help Determine Pathophysiology of Neurodevelopmental Disorders

The evolution of humans brought about a co-occurring evolution of the human brain, which is far larger and more complex than that of many other organisms. The brain has evolved characteristically in humans in many respects, including macro-and micro-anatomical changes in the brain structure, changes in gene expression, and cell populations and ratios. These characteristics are essential for the execution of higher functions, such as sociality, language, and cognition, which express humanity, and are thought to have been acquired over evolutionary time. However, with the acquisition of higher functions also comes the risk of the disease in which they fail. This review focuses on human brain evolution and neurodevelopmental disorders (NDDs) and discusses brain development, molecular evolution, and human brain evolution. Discussing the potential for the development and pathophysiology of NDDs acquired by human brain evolution will provide insights into the acquisition and breakdown of higher functions from a new perspective.

Detection and identification of cis-regulatory elements using change-point and classification algorithms

BACKGROUND

Transcriptional regulation is primarily mediated by the binding of factors to non-coding regions in DNA. Identification of these binding regions enhances understanding of tissue formation and potentially facilitates the development of gene therapies. However, successful identification of binding regions is made difficult by the lack of a universal biological code for their characterisation.

RESULTS

We extend an alignment-based method, changept, and identify clusters of biological significance, through ontology and de novo motif analysis. Further, we apply a Bayesian method to estimate and combine binary classifiers on the clusters we identify to produce a better performing composite.

CONCLUSIONS

The analysis we describe provides a computational method for identification of conserved binding sites in the human genome and facilitates an alternative interrogation of combinations of existing data sets with alignment data.

Current and Future Perspectives of Noncoding RNAs in Brain Function and Neuropsychiatric Disease

Noncoding RNAs (ncRNAs) represent the majority of the transcriptome and play important roles in regulating neuronal functions. ncRNAs are exceptionally diverse in both structure and function and include enhancer RNAs, long ncRNAs, and microRNAs, all of which demonstrate specific temporal and regional expression in the brain. Here, we review recent studies demonstrating that ncRNAs modulate chromatin structure, act as chaperone molecules, and contribute to synaptic remodeling and behavior. In addition, we discuss ncRNA function within the context of neuropsychiatric diseases, particularly focusing on addiction and schizophrenia, and the recent methodological developments that allow for better understanding of ncRNA function in the brain. Overall, ncRNAs represent an underrecognized molecular contributor to complex neuronal processes underlying neuropsychiatric disorders.

Brain transcriptomic profiling reveals common alterations across neurodegenerative and psychiatric disorders

Neurodegenerative and neuropsychiatric disorders (ND-NPs) are multifactorial, polygenic and complex behavioral phenotypes caused by brain abnormalities. Large-scale collaborative efforts have tried to identify the genetic architecture of these conditions. However, the specific and shared underlying molecular pathobiology of brain illnesses is not clear. Here, we examine transcriptome-wide characterization of eight conditions, using a total of 2,633 post-mortem brain samples from patients with Alzheimer’s disease (AD), Parkinson’s disease (PD), Progressive Supranuclear Palsy (PSP), Pathological Aging (PA), Autism Spectrum Disorder (ASD), Schizophrenia (Scz), Major Depressive Disorder (MDD), and Bipolar Disorder (BP)–in comparison with 2,078 brain samples from matched control subjects.

Similar transcriptome alterations were observed between NDs and NPs with the top correlations obtained between Scz-BP, ASD-PD, AD-PD, and Scz-ASD. Region-specific comparisons also revealed shared transcriptome alterations in frontal and temporal lobes across NPs and NDs. Co-expression network analysis identified coordinated dysregulations of cell-type-specific modules across NDs and NPs. This study provides a transcriptomic framework to understand the molecular alterations of NPs and NDs through their shared- and specific gene expression in the brain.

Comprehensive multi-omics integration identifies differentially active enhancers during human brain development with clinical relevance

BACKGROUND

Non-coding regulatory elements (NCREs), such as enhancers, play a crucial role in gene regulation, and genetic aberrations in NCREs can lead to human disease, including brain disorders. The human brain is a complex organ that is susceptible to numerous disorders; many of these are caused by genetic changes, but a multitude remain currently unexplained. Understanding NCREs acting during brain development has the potential to shed light on previously unrecognized genetic causes of human brain disease. Despite immense community-wide efforts to understand the role of the non-coding genome and NCREs, annotating functional NCREs remains challenging.

METHODS

Here we performed an integrative computational analysis of virtually all currently available epigenome data sets related to human fetal brain.

RESULTS

Our in-depth analysis unravels 39,709 differentially active enhancers (DAEs) that show dynamic epigenomic rearrangement during early stages of human brain development, indicating likely biological function. Many of these DAEs are linked to clinically relevant genes, and functional validation of selected DAEs in cell models and zebrafish confirms their role in gene regulation. Compared to enhancers without dynamic epigenomic rearrangement, DAEs are subjected to higher sequence constraints in humans, have distinct sequence characteristics and are bound by a distinct transcription factor landscape. DAEs are enriched for GWAS loci for brain-related traits and for genetic variation found in individuals with neurodevelopmental disorders, including autism.

CONCLUSION

This compendium of high-confidence enhancers will assist in deciphering the mechanism behind developmental genetics of human brain and will be relevant to uncover missing heritability in human genetic brain disorders.

Genetic contributions to autism spectrum disorder

Autism spectrum disorder (autism) is a heterogeneous group of neurodevelopmental conditions characterized by early childhood-onset impairments in communication and social interaction alongside restricted and repetitive behaviors and interests. This review summarizes recent developments in human genetics research in autism, complemented by epigenetic and transcriptomic findings. The clinical heterogeneity of autism is mirrored by a complex genetic architecture involving several types of common and rare variants, ranging from point mutations to large copy number variants, and either inherited or spontaneous (de novo). More than 100 risk genes have been implicated by rare, often de novo, potentially damaging mutations in highly constrained genes. These account for substantial individual risk but a small proportion of the population risk. In contrast, most of the genetic risk is attributable to common inherited variants acting en masse, each individually with small effects. Studies have identified a handful of robustly associated common variants. Different risk genes converge on the same mechanisms, such as gene regulation and synaptic connectivity. These mechanisms are also implicated by genes that are epigenetically and transcriptionally dysregulated in autism. Major challenges to understanding the biological mechanisms include substantial phenotypic heterogeneity, large locus heterogeneity, variable penetrance, and widespread pleiotropy. Considerable increases in sample sizes are needed to better understand the hundreds or thousands of common and rare genetic variants involved. Future research should integrate common and rare variant research, multi-omics data including genomics, epigenomics, and transcriptomics, and refined phenotype assessment with multidimensional and longitudinal measures.

Sex-based eRNA expression and function in ischemic stroke

Enhancer-derived RNAs (eRNAs) are a new class of long noncoding RNA that have roles in modulating enhancer-mediated gene transcription, which ultimately influences phenotypic outcomes. We recently published the first study mapping genome-wide eRNA expression in the male mouse cortex during ischemic stroke and identified 77 eRNAs that were significantly altered following a 1 h middle cerebral artery occlusion (MCAO) and 6 h of reperfusion, as compared to sham controls. Knockdown of one such stroke-induced eRNA - eRNA_06347 - resulted in significantly larger infarcts, demonstrating a role for eRNA_06347 in modulating the post-stroke pathophysiology in males. In the current study, we applied quantitative real-time PCR to evaluate whether the 77 eRNAs identified in the male cortex also show altered expression in the post-stroke female cortex. Using age-matched and time-matched female mice, we found that only a subset of the 77 eRNAs were detected in the post-stroke female cortex. Of these, only a small fraction showed similar temporal expression characteristics as males, including eRNA_06347 which was highly induced in both sexes. Knockdown of eRNA_06347 in the female cortex resulted in significantly increased infarct volumes that were closely matched to those in males, indicating that eRNA_06347 modulates the post-stroke pathophysiology similarly in males and females. This suggests a common underlying role for eRNA_06347 in the two sexes. Overall, this is the first study to evaluate eRNA expression and perturbation in the female cortex during stroke, and present a comparative analysis between males and females. Our findings show that eRNAs have sex-dependent and sex-independent expression patterns that may be of significance to the pathophysiological responses to stroke in the two sexes.

Enhancer RNA: biogenesis, function, and regulation

Enhancers are noncoding DNA elements that are present upstream or downstream of a gene to control its spatial and temporal expression. Specific histone modifications, such as monomethylation on histone H3 lysine 4 (H3K4me1) and H3K27ac, have been widely used to assign enhancer regions in mammalian genomes. In recent years, emerging evidence suggests that active enhancers are bidirectionally transcribed to produce enhancer RNAs (eRNAs). This finding not only adds a new reliable feature to define enhancers but also raises a fundamental question of how eRNAs function to activate transcription. Although some believe that eRNAs are merely transcriptional byproducts, many studies have demonstrated that eRNAs execute crucial tasks in regulating chromatin conformation and transcription activation. In this review, we summarize the current understanding of eRNAs from their biogenesis, functions, and regulation to their pathological significance. Additionally, we discuss the challenges and possible mechanisms of eRNAs in regulated transcription.

Cocaine-related DNA methylation in caudate neurons alters 3D chromatin structure of the IRXA gene cluster

Epigenetic mechanisms, like those involving DNA methylation, are thought to mediate the relationship between chronic cocaine dependence and molecular changes in addiction-related neurocircuitry, but have been understudied in human brain. We initially used reduced representation bisulfite sequencing (RRBS) to generate a methylome-wide profile of cocaine dependence in human post-mortem caudate tissue. We focused on the Iroquois Homeobox A (IRXA) gene cluster, where hypomethylation in exon 3 of IRX2 in neuronal nuclei was associated with cocaine dependence. We replicated this finding in an independent cohort and found similar results in the dorsal striatum from cocaine self-administering mice. Using epigenome editing and 3C assays, we demonstrated a causal relationship between methylation within the IRX2 gene body, CTCF protein binding, three-dimensional (3D) chromatin interaction, and gene expression. Together, these findings suggest that cocaine-related hypomethylation of IRX2 contributes to the development and maintenance of cocaine dependence through alterations in 3D chromatin structure in the caudate nucleus.

Brain Long Noncoding RNAs: Multitask Regulators of Neuronal Differentiation and Function

The extraordinary cellular diversity and the complex connections established within different cells types render the nervous system of vertebrates one of the most sophisticated tissues found in living organisms. Such complexity is ensured by numerous regulatory mechanisms that provide tight spatiotemporal control, robustness and reliability. While the unusual abundance of long noncoding RNAs (lncRNAs) in nervous tissues was traditionally puzzling, it is becoming clear that these molecules have genuine regulatory functions in the brain and they are essential for neuronal physiology. The canonical view of RNA as predominantly a 'coding molecule' has been largely surpassed, together with the conception that lncRNAs only represent 'waste material' produced by cells as a side effect of pervasive transcription. Here we review a growing body of evidence showing that lncRNAs play key roles in several regulatory mechanisms of neurons and other brain cells. In particular, neuronal lncRNAs are crucial for orchestrating neurogenesis, for tuning neuronal differentiation and for the exact calibration of neuronal excitability. Moreover, their diversity and the association to neurodegenerative diseases render them particularly interesting as putative biomarkers for brain disease. Overall, we foresee that in the future a more systematic scrutiny of lncRNA functions will be instrumental for an exhaustive understanding of neuronal pathophysiology.

Modulation of Brain Pathology by Enhancer RNAs in Cerebral Ischemia

Recent studies have reported widespread stimulus-dependent transcription of mammalian enhancers into noncoding enhancer RNAs (eRNAs), some of which have central roles in the enhancer-mediated induction of target genes and modulation of phenotypic outcomes during development and disease. In cerebral ischemia, the expression and functions of eRNAs are virtually unknown. Here, we applied genome-wide H3K27ac ChIP-seq and genome-wide RNA-seq to identify enhancer elements and stroke-induced eRNAs, respectively, in the mouse cerebral cortex during transient focal ischemia. Following a 1-h middle cerebral artery occlusion (MCAO) and 6 h of reperfusion, we identified 77 eRNAs that were significantly upregulated in stroke as compared to sham, of which 55 were exclusively expressed in stroke. The knockdown of two stroke-induced eRNAs in the mouse brain resulted in significantly larger infarct volumes as compared to controls, suggesting that these eRNAs are involved in the post-stroke neuroprotective response. A preliminary comparison of eRNA expression in the male versus female cortices revealed sex-dependent patterns that may underlie the physiological differences in response to stroke between the two sexes. Together, this study is the first to illuminate the eRNA landscape in the post-stroke cortex and demonstrate the significance of an eRNA in modulating post-stroke cortical brain damage.

Exploring the secrets of brain transcriptional regulation: developing methodologies, recent significant findings, and perspectives

Exploring and revealing the secret of the function of the human brain has been the dream of mankind and science. Delineating brain transcriptional regulation has been extremely challenging, but recent technological advances have facilitated a deeper investigation of molecular processes in the brain. Tracing the molecular regulatory mechanisms of different gene expression profiles in the brain is divergent and has made it possible to connect spatial and temporal variations in gene expression to distributed properties of brain structure and function. Here, we review the molecular diversity of the brain among rodents, non-human primates and humans. We also discuss the molecular mechanism of non-coding DNA/RNA at the transcriptional/post-transcriptional level based on recent technical advances to highlight an improved understanding of the complex transcriptional network in the brain. Spatiotemporal and single-cell transcriptomics have attempted to gain novel insight into the development and evolution of the brain as well as the progression of human diseases. Although it is clear that the field is developing and challenges remain to be resolved, the impressive recent progress provides a solid foundation to better understand the brain and evidence-based recommendations for the diagnosis and treatment of brain diseases.

A post-GWAS confirming the genetic effects and functional polymorphisms of AGPAT3 gene on milk fatty acids in dairy cattle

BACKGROUND

People are paying more attention to the healthy and balanced diet with the improvement of their living standards. Milk fatty acids (FAs) have been reported that they were related to some atherosclerosis and coronary heart diseases in human. In our previous genome-wide association study (GWAS) on milk FAs in dairy cattle, 83 genome-wide significant single nucleotide polymorphisms (SNPs) were detected. Among them, two SNPs, ARS-BFGL-NGS-109493 and BTA-56389-no-rs associated with C18index (P = 0.0459), were located in the upstream of 1-acylglycerol-3-phosphate O-acyltransferase 3 (AGPAT3) gene. AGPAT3 is involved in glycerol-lipid, glycerol-phospholipid metabolism and phospholipase D signaling pathways. Hence, it was inferred as a candidate gene for milk FAs. The aim of this study was to further confirm the genetic effects of the AGPAT3 gene on milk FA traits in dairy cattle.

RESULTS

Through re-sequencing the complete coding region, and 3000 bp of 5' and 3' regulatory regions of the AGPAT3 gene, a total of 17 SNPs were identified, including four in 5' regulatory region, one in 5' untranslated region (UTR), three in introns, one in 3' UTR, and eight in 3' regulatory region. By the linkage disequilibrium (LD) analysis with Haploview4.1 software, two haplotype blocks were observed that were formed by four and 12 identified SNPs, respectively. Using SAS9.2, we performed single locus-based and haplotype-based association analysis on 24 milk FAs in 1065 Chinese Holstein cows, and discovered that all the SNPs and the haplotype blocks were significantly associated with C6:0, C8:0 and C10:0 (P < 0.0001-0.0384). Further, with Genomatix, we predicted that four SNPs in 5' regulatory region (g.146702957G > A, g.146704373A > G, g.146704618A > G and g.146704699G > A) changed the transcription factor binding sites (TFBSs) for transcription factors SMARCA3, REX1, VMYB, BRACH, NKX26, ZBED4, SP1, USF1, ARNT and FOXA1. Out of them, two SNPs were validated to impact transcriptional activity by performing luciferase assay that the alleles A of both SNPs, g.146704373A > G and g.146704618A > G, increased the transcriptional activities of AGPAT3 promoter compared with alleles G (P = 0.0004).

CONCLUSIONS

In conclusion, our findings first demonstrated the significant genetic associations of the AGPAT3 gene with milk FAs in dairy cattle, and two potential causal mutations were detected.

HeRA: an atlas of enhancer RNAs across human tissues

Enhancer RNA (eRNA) is a type of long non-coding RNA transcribed from DNA enhancer regions. Despite critical roles of eRNA in gene regulation, the expression landscape of eRNAs in normal human tissue remains unexplored. Using numerous samples from the Genotype-Tissue Expression project, we characterized 45 411 detectable eRNAs and identified tens of thousands of associations between eRNAs and traits, including gender, race, and age. We constructed a co-expression network to identify millions of putative eRNA regulators and target genes across different tissues. We further constructed a user-friendly data portal, Human enhancer RNA Atlas (HeRA, https://hanlab.uth.edu/HeRA/). In HeRA, users can search, browse, and download the eRNA expression profile, trait-related eRNAs, and eRNA co-expression network by searching the eRNA ID, gene symbol, and genomic region in one or multiple tissues. HeRA is the first data portal to characterize eRNAs from 9577 samples across 54 human tissues and facilitates functional and mechanistic investigations of eRNAs.

Space-Dependent Glia-Neuron Interplay in the Hippocampus of Transgenic Models of β-Amyloid Deposition

This review is focused on the description and discussion of the alterations of astrocytes and microglia interplay in models of Alzheimer's disease (AD). AD is an age-related neurodegenerative pathology with a slowly progressive and irreversible decline of cognitive functions. One of AD's histopathological hallmarks is the deposition of amyloid beta (Aβ) plaques in the brain. Long regarded as a non-specific, mere consequence of AD pathology, activation of microglia and astrocytes is now considered a key factor in both initiation and progression of the disease, and suppression of astrogliosis exacerbates neuropathology. Reactive astrocytes and microglia overexpress many cytokines, chemokines, and signaling molecules that activate or damage neighboring cells and their mutual interplay can result in virtuous/vicious cycles which differ in different brain regions. Heterogeneity of glia, either between or within a particular brain region, is likely to be relevant in healthy conditions and disease processes. Differential crosstalk between astrocytes and microglia in CA1 and CA3 areas of the hippocampus can be responsible for the differential sensitivity of the two areas to insults. Understanding the spatial differences and roles of glia will allow us to assess how these interactions can influence the state and progression of the disease, and will be critical for identifying therapeutic strategies.

CRISPR-Cas13a Targeting the Enhancer RNA-SMAD7e Inhibits Bladder Cancer Development Both in vitro and in vivo

Enhancers are cis-acting elements that can promote the expression of target genes and respond to estrogen to induce the transcription of eRNAs, which are closely associated with cancer development. Further study on eRNAs may lead to a better understanding of the significance of transcriptional regulation and the progression of malignant tumors. SMAD7 enhancer RNA (SMAD7e) is an estrogen-responsive eRNA. However, the relationship between SMAD7e and bladder cancer remains unclear. SMAD7e was significantly upregulated in bladder cancer tissues and estrogen-stimulated cells. Knockdown of SMAD7e by CRISPR-Cas13a suppressed cell proliferation and migration, and induced cell apoptosis and inhibited cell invasion. Estrogen caused overexpression of SMAD7e and played a facilitating role in bladder cancer cells. Furthermore, knockdown of SMAD7e by CRISPR-Cas13a prevented the cancer-promoting effects of estrogen on bladder cancer both in vitro and in vivo. The present study suggested the crucial role of SMAD7e in bladder cancer. Estrogen might promote the development of bladder cancer by inducing SMAD7e production. These findings may provide a potential target for CRISPR-mediated gene therapy for bladder cancer in the future.

Enhancer RNAs predict enhancer-gene regulatory links and are critical for enhancer function in neuronal systems

Genomic enhancer elements regulate gene expression programs important for neuronal fate and function and are implicated in brain disease states. Enhancers undergo bidirectional transcription to generate non-coding enhancer RNAs (eRNAs). However, eRNA function remains controversial. Here, we combined Assay for Transposase-Accessible Chromatin using Sequencing (ATAC-Seq) and RNA-Seq datasets from three distinct neuronal culture systems in two activity states, enabling genome-wide enhancer identification and prediction of putative enhancer-gene pairs based on correlation of transcriptional output. Notably, stimulus-dependent enhancer transcription preceded mRNA induction, and CRISPR-based activation of eRNA synthesis increased mRNA at paired genes, functionally validating enhancer-gene predictions. Focusing on enhancers surrounding the Fos gene, we report that targeted eRNA manipulation bidirectionally modulates Fos mRNA, and that Fos eRNAs directly interact with the histone acetyltransferase domain of the enhancer-linked transcriptional co-activator CREB-binding protein (CBP). Together, these results highlight the unique role of eRNAs in neuronal gene regulation and demonstrate that eRNAs can be used to identify putative target genes.

Regulatory sites for splicing in human basal ganglia are enriched for disease-relevant information

Genome-wide association studies have generated an increasing number of common genetic variants associated with neurological and psychiatric disease risk. An improved understanding of the genetic control of gene expression in human brain is vital considering this is the likely modus operandum for many causal variants. However, human brain sampling complexities limit the explanatory power of brain-related expression quantitative trait loci (eQTL) and allele-specific expression (ASE) signals. We address this, using paired genomic and transcriptomic data from putamen and substantia nigra from 117 human brains, interrogating regulation at different RNA processing stages and uncovering novel transcripts. We identify disease-relevant regulatory loci, find that splicing eQTLs are enriched for regulatory information of neuron-specific genes, that ASEs provide cell-specific regulatory information with evidence for cellular specificity, and that incomplete annotation of the brain transcriptome limits interpretation of risk loci for neuropsychiatric disease. This resource of regulatory data is accessible through our web server, http://braineacv2.inf.um.es/.

Regulation of gene expression and splicing are thought to be tissue-specific. Here, the authors obtain genomic and transcriptomic data from putamen and substantia nigra of 117 neurologically healthy human brains and find that splicing eQTLs are enriched for neuron-specific regulatory information.

A long noncoding RNA cluster-based genomic locus maintains proper development and visual function

Long noncoding RNAs (lncRNAs) represent a group of regulatory RNAs that play critical roles in numerous cellular events, but their functional importance in development remains largely unexplored. Here, we discovered a series of previously unidentified gene clusters harboring conserved lncRNAs at the nonimprinting regions in brain (CNIBs). Among the seven identified CNIBs, human CNIB1 locus is located at Chr 9q33.3 and conserved from Danio rerio to Homo sapiens. Chr 9q33.3-9q34.11 microdeletion has previously been linked to human nail-patella syndrome (NPS) which is frequently accompanied by developmental and visual deficiencies. By generating CNIB1 deletion alleles in zebrafish, we demonstrated the requirement of CNIB1 for proper growth and development, and visual activities. Furthermore, we found that the role of CNIB1 on visual activity is mediated through a regulator of ocular development-lmx1bb. Collectively, our study shows that CNIB1 lncRNAs are important for zebrafish development and provides an lncRNA cluster-mediated pathophysiological mechanism for human Chr 9q33.3-9q34.11 microdeletion syndrome.

Eukaryotic transcription factors can track and control their target genes using DNA antennas

Eukaryotic transcription factors (TF) function by binding to short 6-10 bp DNA recognition sites located near their target genes, which are scattered through vast genomes. Such process surmounts enormous specificity, efficiency and celerity challenges using a molecular mechanism that remains poorly understood. Combining biophysical experiments, theory and bioinformatics, we dissect the interplay between the DNA-binding domain of Engrailed, a Drosophila TF, and the regulatory regions of its target genes. We find that Engrailed binding affinity is strongly amplified by the DNA regions flanking the recognition site, which contain long tracts of degenerate recognition-site repeats. Such DNA organization operates as an antenna that attracts TF molecules in a promiscuous exchange among myriads of intermediate affinity binding sites. The antenna ensures a local TF supply, enables gene tracking and fine control of the target site's basal occupancy. This mechanism illuminates puzzling gene expression data and suggests novel engineering strategies to control gene expression.

An integrative analysis of non-coding regulatory DNA variations associated with autism spectrum disorder

A number of genetic studies have identified rare protein-coding DNA variations associated with autism spectrum disorder (ASD), a neurodevelopmental disorder with significant genetic etiology and heterogeneity. In contrast, the contributions of functional, regulatory genetic variations that occur in the extensive non-protein-coding regions of the genome remain poorly understood. Here we developed a genome-wide analysis to identify the rare single nucleotide variants (SNVs) that occur in non-coding regions and determined the regulatory function and evolutionary conservation of these variants. Using publicly available datasets and computational predictions, we identified SNVs within putative regulatory regions in promoters, transcription factor binding sites, and microRNA genes and their target sites. Overall, we found that the regulatory variants in ASD cases were enriched in ASD-risk genes and genes involved in fetal neurodevelopment. As with previously reported coding mutations, we found an enrichment of the regulatory variants associated with dysregulation of neurodevelopmental and synaptic signaling pathways. Among these were several rare inherited SNVs found in the mature sequence of microRNAs predicted to affect the regulation of ASD-risk genes. We show a paternally inherited miR-873-5p variant with altered binding affinity for several risk-genes including NRXN2 and CNTNAP2 putatively overlay maternally inherited loss-of-function coding variations in NRXN1 and CNTNAP2 to likely increase the genetic liability in an idiopathic ASD case. Our analysis pipeline provides a new resource for identifying loss-of-function regulatory DNA variations that may contribute to the genetic etiology of complex disorders.

Beyond the Exome: The Non-coding Genome and Enhancers in Neurodevelopmental Disorders and Malformations of Cortical Development

The development of the human cerebral cortex is a complex and dynamic process, in which neural stem cell proliferation, neuronal migration, and post-migratory neuronal organization need to occur in a well-organized fashion. Alterations at any of these crucial stages can result in malformations of cortical development (MCDs), a group of genetically heterogeneous neurodevelopmental disorders that present with developmental delay, intellectual disability and epilepsy. Recent progress in genetic technologies, such as next generation sequencing, most often focusing on all protein-coding exons (e.g., whole exome sequencing), allowed the discovery of more than a 100 genes associated with various types of MCDs. Although this has considerably increased the diagnostic yield, most MCD cases remain unexplained. As Whole Exome Sequencing investigates only a minor part of the human genome (1-2%), it is likely that patients, in which no disease-causing mutation has been identified, could harbor mutations in genomic regions beyond the exome. Even though functional annotation of non-coding regions is still lagging behind that of protein-coding genes, tremendous progress has been made in the field of gene regulation. One group of non-coding regulatory regions are enhancers, which can be distantly located upstream or downstream of genes and which can mediate temporal and tissue-specific transcriptional control via long-distance interactions with promoter regions. Although some examples exist in literature that link alterations of enhancers to genetic disorders, a widespread appreciation of the putative roles of these sequences in MCDs is still lacking. Here, we summarize the current state of knowledge on cis-regulatory regions and discuss novel technologies such as massively-parallel reporter assay systems, CRISPR-Cas9-based screens and computational approaches that help to further elucidate the emerging role of the non-coding genome in disease. Moreover, we discuss existing literature on mutations or copy number alterations of regulatory regions involved in brain development. We foresee that the future implementation of the knowledge obtained through ongoing gene regulation studies will benefit patients and will provide an explanation to part of the missing heritability of MCDs and other genetic disorders.

Landscape of Enhancer-Enhancer Cooperative Regulation during Human Cardiac Commitment

Although accumulating evidence has demonstrated the key roles of enhancers in gene expression regulation, the contribution of genome-wide enhancer-enhancer interactions to developmental decisions remains unclear. Here we explored the cooperative regulation patterns among enhancers to understand their regulatory mechanism. We first filtered robust enhancers in embryonic stem cells (ESCs) through integrating bidirectional transcription, genomic location, and epigenetic modification. Genome-wide enhancer-enhancer interactions were then identified based on enhancer-promoter relationships that were derived from Hi-C data. We further explored the interacting principles of the identified enhancer-enhancer interactions. The results revealed that the observed cooperativity occurred mainly between enhancers distributed within a 1-kb to 10-Mb distance across the genome. In addition, enhancer-enhancer pairs had higher expression correlations than non-interacting pairs. Finally, we identified robust enhancers during human cardiac commitment, and we found that enhancers exhibited strong stage-specific expression patterns. We further inferred the enhancer-enhancer interactions based on RNA sequencing (RNA-seq) data in heart development, according to the regulatory principles characterized from Hi-C data. The identified enhancer-enhancer interaction networks (EEINs) presented highly dynamic linkages. Moreover, enhancers cooperatively targeted many marker genes in each developmental stage to regulate stage-specific functions, which contribute to the organization of cell identity in heart development. Our work will increase the understanding of enhancer regulation in human heart development.

A Potential Role for the Noncoding Transcriptome in Psychiatric Disorders

Understanding the complexity and regular function of the human brain is an unresolved challenge that hampers the identification of disease-contributing components and mechanisms of psychiatric disorders. It is accepted that the majority of psychiatric disorders result from a complex interaction of environmental and heritable factors, and efforts to determine, for example, genetic variants contributing to the pathophysiology of these diseases are becoming increasingly successful. We also continue to discover new molecules with unknown functions that might play a role in brain physiology. One such class of polymeric molecules is noncoding RNAs; though discovered years ago, they have only recently started to receive careful attention. Furthermore, recent technological advances in the field of molecular genetics and high-throughput sequencing have facilitated the discovery of a broad spectrum of RNAs that show no obvious coding potential but may provide additional layers of complexity and regulation to the molecular mechanisms underlying psychiatric disorders. Their exquisite enrichment and expression profiles in the brain may point to important functions of these RNAs in health and disease. This review will therefore aim to provide insight into the expression of noncoding RNAs in the brain, their function, and potential role in psychiatric disorders.

Adolescent Alcohol Exposure Epigenetically Suppresses Amygdala Arc Enhancer RNA Expression to Confer Adult Anxiety Susceptibility

BACKGROUND

Adolescent intermittent ethanol (AIE) exposure is an emerging risk factor for adult psychopathology, such as anxiety disorders. Enhancer RNAs (eRNAs) are short noncoding RNAs transcribed from enhancer regions that regulate synaptic plasticity-associated gene expression, including Arc, but their role in AIE-induced susceptibility to anxiety in adulthood is unknown.

METHODS

Rats were exposed to AIE (ethanol exposure 2 days on/off) or intermittent normal saline during postnatal days 28 to 41 and allowed to grow to adulthood for analysis of behavior and biochemical measures. Some AIE rats and rats with intermittent normal saline exposure were exposed to an acute challenge with ethanol in adulthood. Cohorts of alcohol-naïve adult rats were cannulated in the central nucleus of amygdala and infused with either Kdm6b small interfering RNA or an antisense locked nucleic acid oligonucleotide specific to Arc eRNA before behavioral and biochemical analysis.

RESULTS

AIE adult rats displayed heightened anxiety and decreased Arc eRNA expression, which is regulated epigenetically through decreased Kdm6b expression. This triggered condensed chromatin at the synaptic activity response element site and promoter of the Arc gene, facilitating increased negative elongation factor binding to the Arc promoter and decreasing Arc expression in the amygdala. Knockdown of Kdm6b or Arc eRNA expression in the central nucleus of amygdala provoked anxiety in alcohol-naïve adult rats and recapitulated the molecular and epigenetic phenotypes of AIE.

CONCLUSIONS

These data suggest that eRNA regulation via epigenetic reprogramming in the amygdala, particularly at the Arc synaptic activity response element site, contributes to adult anxiety after adolescent alcohol exposure.

Using Machine Learning to Measure Relatedness Between Genes: A Multi-Features Model

Measuring conditional relatedness between a pair of genes is a fundamental technique and still a significant challenge in computational biology. Such relatedness can be assessed by gene expression similarities while suffering high false discovery rates. Meanwhile, other types of features, e.g., prior-knowledge based similarities, is only viable for measuring global relatedness. In this paper, we propose a novel machine learning model, named Multi-Features Relatedness (MFR), for accurately measuring conditional relatedness between a pair of genes by incorporating expression similarities with prior-knowledge based similarities in an assessment criterion. MFR is used to predict gene-gene interactions extracted from the COXPRESdb, KEGG, HPRD, and TRRUST databases by the 10-fold cross validation and test verification, and to identify gene-gene interactions collected from the GeneFriends and DIP databases for further verification. The results show that MFR achieves the highest area under curve (AUC) values for identifying gene-gene interactions in the development, test, and DIP datasets. Specifically, it obtains an improvement of 1.1% on average of precision for detecting gene pairs with both high expression similarities and high prior-knowledge based similarities in all datasets, comparing to other linear models and coexpression analysis methods. Regarding cancer gene networks construction and gene function prediction, MFR also obtains the results with more biological significances and higher average prediction accuracy, than other compared models and methods. A website of the MFR model and relevant datasets can be accessed from http://bmbl.sdstate.edu/MFR.

Long non-coding RNA repertoire and open chromatin regions constitute midbrain dopaminergic neuron - specific molecular signatures

Midbrain dopaminergic (DA) neurons are involved in diverse neurological functions, including control of movements, emotions or reward. In turn, their dysfunctions cause severe clinical manifestations in humans, such as the appearance of motor and cognitive symptoms in Parkinson’s Disease. The physiology and pathophysiology of these neurons are widely studied, mostly with respect to molecular mechanisms implicating protein-coding genes. In contrast, the contribution of non-coding elements of the genome to DA neuron function is poorly investigated. In this study, we isolated DA neurons from E14.5 ventral mesencephalons in mice, and used RNA-seq and ATAC-seq to establish and describe repertoires of long non-coding RNAs (lncRNAs) and putative DNA regulatory regions specific to this neuronal population. We identified 1,294 lncRNAs constituting the repertoire of DA neurons, among which 939 were novel. Most of them were not found in hindbrain serotonergic (5-HT) neurons, indicating a high degree of cell-specificity. This feature was also observed regarding open chromatin regions, as 39% of the ATAC-seq peaks from the DA repertoire were not detected in the 5-HT neurons. Our work provides for the first time DA-specific catalogues of non-coding elements of the genome that will undoubtedly participate in deepening our knowledge regarding DA neuronal development and dysfunctions.

Enhancer RNAs: a missing regulatory layer in gene transcription

Enhancers and super-enhancers exert indispensable roles in maintaining cell identity through spatiotemporally regulating gene transcription. Meanwhile, active enhancers and super-enhancers also produce transcripts termed enhancer RNAs (eRNAs) from their DNA elements. Although enhancers have been identified for more than 30 years, widespread transcription from enhancers are just discovered by genome-wide sequencing and considered as the key to understand longstanding questions in gene transcription. RNA-transcribed enhancers are marked by histone modifications such as H3K4m1/2 and H3K27Ac, and enriched with transcription regulatory factors such as LDTFs, P300, CBP, BRD4 and MED1. Those regulatory factors might constitute a Mega-Trans-like complex to potently activate enhancers. Compared to mRNAs, eRNAs are quite unstable and play roles at local. Functionally, it has been shown that eRNAs promote formation of enhancer-promoter loops. Several studies also demonstrated that eRNAs help the binding of RNA polymerase II (RNAPII) or transition of paused RNAPII by de-association of the negative elongation factor (NELF) complex. Nevertheless, these proposed mechanisms are not universally accepted and still under controversy. Here, we comprehensively summarize the reported findings and make perspectives for future exploration. We also believe that super-enhancer derived RNAs (seRNAs) might be informative to understand the nature of super-enhancers.

Microglia in Neurological Diseases: A Road Map to Brain-Disease Dependent-Inflammatory Response

Microglia represent a specialized population of macrophages-like cells in the central nervous system (CNS) considered immune sentinels that are capable of orchestrating a potent inflammatory response. Microglia are also involved in synaptic organization, trophic neuronal support during development, phagocytosis of apoptotic cells in the developing brain, myelin turnover, control of neuronal excitability, phagocytic debris removal as well as brain protection and repair. Microglial response is pathology dependent and affects to immune, metabolic. In this review, we will shed light on microglial activation depending on the disease context and the influence of factors such as aging, environment or cell-to-cell interaction.

Oestrogen promotes tumorigenesis of bladder cancer by inducing the enhancer RNA-eGREB1

In recent years, studies have shown that enhancer RNAs (eRNAs) can be transcribed from enhancers. Increasing evidence has revealed that eRNAs play critical roles in the development of various cancers. Oestrogen‐associated eRNAs are closely related to breast cancer. In view of the gender differences in bladder cancer (BCa), we suppose that oestrogen‐associated eRNAs are also involved in tumorigenesis of BCa. In our study, we first demonstrated that eGREB1 derived from the enhancer of an oestrogen‐responsive gene—GREB1 was up‐regulated in BCa tissues, and the expression level of eGREB1 is positively associated with the histological grade and TNM stage of BCa. Knockdown of eGREB1 by CRISPR‐Cas13a could inhibit cell proliferation, migration and invasion and induce apoptosis in BCa cells T24 and 5637. Besides, we exhibited the promoting effect of oestrogen on BCa cells. What's more, down‐regulation of eGREB1 could improve the malignant biological characteristics of BCa cells induced by oestrogen. In conclusion, our data indicated that eGREB1 plays oncogenic role and oestrogen may promote the occurrence and progression of BCa by inducing eGREB1 production. Our findings provide new insights into the prevention of BCa and develop a novel therapeutic target for the treatment of BCa.

Capturing functional long non-coding RNAs through integrating large-scale causal relations from gene perturbation experiments

Characterizing functions of long noncoding RNAs (lncRNAs) remains a major challenge, mostly due to the lack of lncRNA-involved regulatory relationships. A wide array of genome-wide expression profiles generated by gene perturbation have been widely used to capture causal links between perturbed genes and response genes. Through annotating >600 gene perturbation profiles, over 354,000 causal relationships between perturbed genes and lncRNAs were identified. This large-scale resource of causal relations inspired us to develop a novel computational approach LnCAR for inferring lncRNAs' functions, which showed a higher accuracy than the co-expression based approach. By application of LnCAR to the cancer hallmark processes, we identified 38 lncRNAs involved in distinct carcinogenic processes. The "activating invasion & metastasis" related lncRNAs were strongly associated with metastatic progression in various cancer types and could act as a predictor of cancer metastasis. Meanwhile, the "evading immune destruction" related lncRNAs showed significant associations with immune infiltration of various immune cells and, importantly, can predict response to anti-PD-1 immunotherapy, suggesting their potential roles as biomarkers for immune therapy. Taken together, our approach provides a novel way to systematically reveal functions of lncRNAs, which will be helpful for further experimental exploration and clinical translational research of lncRNAs.

Enhancer RNAs (eRNAs): New Insights into Gene Transcription and Disease Treatment

Enhancers are cis-acting elements that have the ability to increase the expression of target genes. Recent studies have shown that enhancers can act as transcriptional units for the production of enhancer RNAs (eRNAs), which are hallmarks of activity enhancers and are involved in the regulation of gene transcription. The in-depth study of eRNAs is of great significance for us to better understand enhancer function and transcriptional regulation in various diseases. Therefore, eRNAs may be a potential therapeutic target for diseases. Here, we review the current knowledge of the characteristics of eRNAs, the molecular mechanisms of eRNAs action, as well as diseases related to dysregulation of eRNAs.

Glucocerebrosidase mRNA is Diminished in Brain of Lewy Body Diseases and Changes with Disease Progression in Blood

Parkinson disease (PD) and dementia with Lewy bodies (DLB) are Lewy body diseases characterized by abnormal alpha-synuclein deposits and overlapping pathological features in the brain. Several studies have shown that glucocerebrosidase (GBA) deficiency is involved in the development of LB diseases. Here, we aimed to find out if this deficiency starts at the transcriptional level, also involves alternative splicing, and if GBA expression changes in brain are also detectable in blood of patients with LB diseases. The expression of three GBA transcript variants (GBAtv1, GBAtv2 and GBAtv5) was analyzed in samples from 20 DLB, 25 PD and 17 control brains and in blood of 20 DLB, 26 PD patients and 17 unaffected individuals. Relative mRNA expression was determined by real-time PCR. Expression changes were evaluated by the ΔΔCt method. In brain, specific expression profiles were identified in the temporal cortex of DLB and in the caudate nucleus of PD. In blood, significant GBA mRNA diminution was found in both DLB and PD patients. Early PD and early-onset DLB patients showed lowest GBA levels which were normal in PD patients with advanced disease and DLB patients who developed disease after 70 years of age. In conclusion, disease group specific GBA expression profiles were found in mostly affected areas of LBD. In blood, GBA expression was diminished in LB diseases, especially in patients with early onset DLB and in patients with early PD. Age of disease onset exerts an opposite effect on GBA expression in DLB and PD.