A unique circular RNA expression pattern in the peripheral blood of myalgic encephalomyelitis/chronic fatigue syndrome patients.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease with obscure aetiology. The underdiagnosis rate of ME/CFS is high due to the lack of diagnostic criteria based on objective markers. In recent years, circRNAs have emerged as potential genetic biomarkers for neurological diseases, including Parkinson's disease and Alzheimer's disease, making them likely to have the same prospect of being biomarkers in ME/CFS. However, despite the extensive amount of research that has been performed on the transcriptomes of ME/CFS patients, all of them are solely focused on linear RNAs, and the profiling of circRNAs in ME/CFS has been completely omitted. In this study, we investigated the expression profiles of circRNAs, comparing ME/CFS patients and controls before and after two sessions of cardiopulmonary exercise longitudinally. In patients with ME/CFS, the number of detected circRNAs was higher compared to healthy controls, indicating potential differences in circRNA expression associated with the disease. Additionally, healthy controls showed an increase in the number of circRNAs following exercise testing, while no similar pattern was evident in ME/CFS patients, further highlighting physiological differences between the two groups. A lack of correlation was observed between differentially expressed circRNAs and their corresponding coding genes in terms of expression and function, suggesting the potential of circRNAs as independent biomarkers in ME/CFS. Specifically, 14 circRNAs were highly expressed in ME/CFS patients but absent in controls throughout the exercise study, indicating a unique molecular signature specific to ME/CFS patients and providing potential diagnostic biomarkers for the disease. Significant enrichment of protein and gene regulative pathways were detected in relation to five of these 14 circRNAs based on their predicted miRNA target genes. Overall, this is the first study to describe the circRNA expression profile in peripheral blood of ME/CFS patients, providing valuable insights into the molecular mechanisms underlying the disease.

Investigation of circular RNA transcriptome in obesity-related endometrial cancer.

The present study has investigated the circular RNA (circRNA) transcriptome of twenty obese and postmenopausal women, recruited in Australia, with endometrial cancer (EC). This paper expands on previous findings which evaluated the circRNA transcriptome of a similar cohort of six women recruited in the United States of America. EC is the most common gynaecological malignancy and the fifth most common cancer in women worldwide with obesity as one of its major risk factors. CircRNAs, a class of non-coding RNAs, are involved in many human diseases including cancer. As such the objective of this study was to investigate the circRNA transcriptome of these twenty women and identify circRNAs of interest. We obtained paired samples (EC and adjacent normal tissue) from the cohort of twenty women. Samples were subjected to ribosomal RNA depletion and sequencing performed using Illumina sequencing technology. CircRNAs were identified through CIRI2 and CIRCexplorer2 and common circRNAs extracted for differential expression with edgeR which met the criteria of counts per million > 0.1 and expressed in ≥ 10. We found that the overall abundance of circRNAs was lower in EC compared to adjacent non-cancerous endometrial tissue. We also identified hotspot genes, genes expressing over 10 distinct circRNA isoforms. There were 82 hotspot genes in normal tissue and 23 hotspot genes in EC. There were 174 significantly differentially expressed circRNAs, of which 172 were down-regulated and 2 were up-regulated in EC. The circRNAs identified from this study may act as diagnostic or prognostic biomarkers for EC in obese women. While the circRNA transcriptome of obesity-related EC has been investigated further work is required to determine their functional significance.

Circular RNA Expression and Interaction Patterns Are Perturbed in Amyotrophic Lateral Sclerosis.

Circular RNAs (circRNAs) are a type of long noncoding RNA that are highly abundant and highly conserved throughout evolution and exhibit differential expression patterns in various tissue types in multiple diseases, including amyotrophic lateral sclerosis (ALS). The most well-known function of circRNAs is their ability to act as microRNA (miRNA) sponges. This entails circRNA binding to miRNA, which would otherwise target and degrade messenger RNA, thus affecting gene expression. This study analyzed ALS patient samples from three spinal cord regions to investigate circular transcriptome perturbation and circular RNA-microRNA-mRNA interactions. Using stringent statistical parameters, we identified 92 differentially expressed circRNAs across the spinal cord tissues with the aim of identifying specific circRNAs with biomarker potential. We also found evidence for differential expression of 37 linear RNAs possibly due to miRNA sequestration by circRNAs, thus revealing their potential as novel biomarkers and therapeutic candidates for ALS.

Investigation of Transcriptome Patterns in Endometrial Cancers from Obese and Lean Women.

Endometrial cancer is the most common gynaecological malignancy in developed countries. One of the largest risk factors for endometrial cancer is obesity. The aim of this study was to determine whether there are differences in the transcriptome of endometrial cancers from obese vs. lean women. Here we investigate the transcriptome of endometrial cancer between obese and lean postmenopausal women using rRNA-depleted RNA-Seq data from endometrial cancer tissues and matched adjacent non-cancerous endometrial tissues. Differential expression analysis identified 12,484 genes (6370 up-regulated and 6114 down-regulated) in endometrial cancer tissues from obese women, and 6219 genes (3196 up-regulated and 3023 down-regulated) in endometrial cancer tissues from lean women (adjusted p-value < 0.1). A gene ontology enrichment analysis revealed that the top 1000 up-regulated genes (by adjusted p-value) were enriched for growth and proliferation pathways while the top 1000 down-regulated genes were enriched for cytoskeleton restructure networks in both obese and lean endometrial cancer tissues. In this study, we also show perturbations in the expression of protein coding genes (HIST1H2BL, HIST1H3F, HIST1H2BH, HIST1H1B, TTK, PTCHD1, ASPN, PRELP, and CDH13) and the lncRNA MBNL1-AS1 in endometrial cancer tissues. Overall, this study has identified gene expression changes that are similar and also unique to endometrial cancers from obese vs. lean women. Furthermore, some of these genes may serve as prognostic biomarkers or, possibly, therapeutic targets for endometrial cancer.

RNA polyadenylation patterns in the human transcriptome.

The eukaryotic transcriptome undergoes various post-transcriptional modifications which assists gene expression. Polyadenylation is a molecular process occurring at the 3'-end of the RNA molecule which involves the poly(A) polymerase attaching adenine monophosphate molecules in a chain-like fashion to assemble a poly(A) tail. Multiple RNA isoforms are produced with differing 3'-UTR and exonic compositions through alternative polyadenylation (APA) which enhances the diversification of alternatively spliced mRNA transcripts. To study polyadenylation patterns, novel methods have been developed using short-read and long-read sequencing technologies to analyse the 3'-ends of the transcript. Recent studies have identified unique polyadenylation patterns in different cellular functions, including oncogenic activity, which could prove valuable in the understanding of medical genetics, particularly in the discovery of biomarkers in diseased states. We present a review of current literature reporting on polyadenylation and the biological relevance in the mammalian transcriptome, with a focus on the human transcriptome. Additionally, we have explored the various methods available to detect polyadenylation patterns using second and third generation sequencing technologies.

Identification of Specific Circular RNA Expression Patterns and MicroRNA Interaction Networks in Mesial Temporal Lobe Epilepsy.

Circular RNAs (circRNAs) regulate mRNA translation by binding to microRNAs (miRNAs), and their expression is altered in diverse disorders, including cancer, cardiovascular disease, and Parkinson's disease. Here, we compare circRNA expression patterns in the temporal cortex and hippocampus of patients with pharmacoresistant mesial temporal lobe epilepsy (MTLE) and healthy controls. Nine circRNAs showed significant differential expression, including circRNA-HOMER1, which is expressed in synapses. Further, we identified miRNA binding sites within the sequences of differentially expressed (DE) circRNAs; expression levels of mRNAs correlated with changes in complementary miRNAs. Gene set enrichment analysis of mRNA targets revealed functions in heterocyclic compound binding, regulation of transcription, and signal transduction, which maintain the structure and function of hippocampal neurons. The circRNA-miRNA-mRNA interaction networks illuminate the molecular changes in MTLE, which may be pathogenic or an effect of the disease or treatments and suggests that DE circRNAs and associated miRNAs may be novel therapeutic targets.

Cell type-specific circular RNA expression in human glial cells.

The circular transcriptome of human glial cells is an area of neuroscience that has not been thoroughly elucidated. Circular RNAs (circRNAs) have the potential to facilitate the understanding of vast, complex and unknown mechanisms derived from the human transcriptome, including elements of the human brain that are not known and the evolution of the human brain, the complexities of which are not well understood. Moreover, the glial cells have been determined to contribute to human brain evolution. This study presents the first comprehensive analysis of the human brain glia circRNA transcriptome, that is, astrocytes, microglia and oligodendrocytes. After stringent criteria applied to the detection of circRNAs, it was found that the circular transcriptomes of these glia are unique from one another, and hence might be indicative of distinct roles for circRNAs within the brain. This study found 265, 239 and 442 circRNAs comprising the unique circular transcriptome of astrocytes, microglia and oligodendrocytes, respectively. The most abundant circRNAs in these glial cell types are expressed by parent genes co-expressing linear RNAs in low abundance, suggesting spliceosome activity favorable to the back-splicing mechanism instead of canonical splicing activity.

Analysis of the Circular Transcriptome in the Synaptosomes of Aged Mice.

Recently, circular RNAs (circRNAs) have been revealed to be an important non-coding element of the transcriptome. The brain contains the most abundant and widespread expression of circRNA. There are also indications that the circular transcriptome undergoes dynamic changes as a result of brain ageing. Diminished cognitive function with increased age reflects the dysregulation of synaptic function and ineffective neurotransmission through alterations of the synaptic proteome. Here, we present changes in the circular transcriptome in ageing synapses using a mouse model. Specifically, we observed an accumulation of uniquely expressed circular transcripts in the synaptosomes of aged mice compared to young mice. Individual circRNA expression patterns were characterized by an increased abundance in the synaptosomes of young or aged mice, whereas the opposite expression was observed for the parental gene linear transcripts. These changes in expression were validated by RT-qPCR. We provide the first comprehensive survey of the circular transcriptome in mammalian synapses, thereby paving the way for future studies. Additionally, we present 16 genes that express solely circRNAs, without linear RNAs co-expression, exclusively in young and aged synaptosomes, suggesting a synaptic gene network that functions along canonical splicing activity.

Neural circular transcriptomes across mammalian species.

Circular RNAs (circRNAs) have recently attracted significant interest in the realm of science and the evolution of species. Given the lack of information available on circRNAs due to various barriers related to sequencing techniques and bioinformatics tools, little regarding their function is known. It has been predicted that circRNAs contribute to gene expression regulation, but aside from a few specific cases, this contention has yet to be proven. Although the role of circRNAs in evolution remains elusive, from the few studies that have shown circRNA conservation in mammalian species, tissue specificity in brain regions, and the abundance of circRNAs in the brains of various species, the concept is becoming more likely with much gravitas. The proposed functional role of circRNAs being gene regulators is of great interest and would provide a basis to further understand not only the functional capabilities of organisms, but also the evolution of mammalian species.

Early transcriptome changes in response to chemical long-term potentiation induced via activation of synaptic NMDA receptors in mouse hippocampal neurons.

Long term potentiation (LTP) is a form of synaptic plasticity. In the present study LTP was induced via activation of synaptic NMDA receptors in primary hippocampal neuron cultures from neonate mice and RNA was isolated for RNA sequencing at 20 min following LTP induction. RNA sequencing and differential expression testing was performed to determine the identity and abundance of protein-coding and non-coding RNAs in control and LTP induced neuron cultures. We show that expression levels of a small group of transcripts encoding proteins involved in negative regulation of gene expression (Adcyap1, Id3), protein translation (Rpl22L1), extracellular structure organization (Bgn), intracellular signalling (Ppm1H, Ntsr2, Cldn10) and protein citrullination (PAD2) are downregulated in the stimulated neurons. Our results suggest that the early stages of LTP are accompanied by the remodelling of the biosynthetic machinery, interactions with the extracellular matrix and intracellular signalling pathways at the transcriptional level.

Are serum ferritin and transferrin saturation risk markers for restless legs syndrome in young adults? Longitudinal and cross-sectional data from the Western Australian Pregnancy Cohort (Raine) Study.

Restless legs syndrome has been associated with serum iron deficiency in clinical studies. However, studies investigating this relationship have had inconsistent results and there are no studies in young adults. Therefore, we investigated the relationship between serum measures of iron stores and restless legs syndrome in young adults in the community. Participants in the Western Australian Pregnancy Cohort (Raine) Study answered questions on restless legs syndrome (n = 1,100, 54% female) at age 22 years, and provided serum measures of iron stores (ferritin and transferrin saturation) at ages 17 and 22 years. Restless legs syndrome was diagnosed when four International RLS Study Group criteria were met (urge to move, dysaesthesia, relief by movement, worsening during evening/night) and these symptoms occurred ≥5 times per month. Logistic regression was used to assess associations between serum iron stores and restless legs syndrome, adjusting for potential confounders. The prevalence of restless legs syndrome at age 22 years was 3.0% (n = 33, 70% female). Among those who provided restless legs syndrome and iron data at age 22 years (n = 865), the median (interquartile range) ferritin was not different between the restless legs syndrome (55 [29.5-103.5] µg L-1 ) and the non-restless legs syndrome group (65.0 [35.0-103.3] µg L-1 , p = 0.2), nor were there differences in iron deficiency prevalence (p = 0.36). There was no association between restless legs syndrome (22 years) and iron stores (17, 22 years) before or after adjustment for potential confounders. There was no association between restless legs syndrome at 22 years and iron stores at 17 or 22 years in this cohort. Serum iron stores may not be a useful indicator of restless legs syndrome risk in young adults in the community.

Multiple System Atrophy: Many Lessons from the Transcriptome.

Multiple system atrophy (MSA) is a complex, multifactorial, debilitating neurodegenerative disease that is often misdiagnosed and misunderstood. MSA has two subclasses, MSA-P and MSA-C, defined by the dominance of parkinsonism or cerebellar dysfunction in the earlier stages of disease, coupled with dysautonomia. This distinction between subclasses becomes largely redundant as the disease progresses. Aggregation of α-synuclein is a clinical marker used to confirm MSA diagnoses, which can only be performed postmortem. Transcriptome profiling provides in-depth information about the diseased state and can contribute to further understanding of MSA, enabling easier and more rapid diagnosis as well as contributing to improving the quality of life of people with MSA. Currently, there is no method of diagnosing MSA with certainty, and there is no cure for this disease. This review provides an update on current advances in investigations of molecular pathology of MSA with particular focus on perturbation of individual gene expression and MSA transcriptome.