miR-196a Ameliorates Cytotoxicity and Cellular Phenotype in Transgenic Huntington's Disease Monkey Neural Cells

Neuroinflammation and the role of epigenetic-based therapies for Huntington's disease management: the new paradigm

Huntington's disease (HD) is an inherited, autosomal, neurodegenerative ailment that affects the striatum of the brain. Despite its debilitating effect on its patients, there is no proven cure for HD management as of yet. Neuroinflammation, excitotoxicity, and environmental factors have been reported to influence the regulation of gene expression by modifying epigenetic mechanisms. Aside focusing on the etiology, changes in epigenetic mechanisms have become a crucial factor influencing the interaction between HTT protein and epigenetically transcribed genes involved in neuroinflammation and HD. This review presents relevant literature on epigenetics with special emphasis on neuroinflammation and HD. It summarizes pertinent research on the role of neuroinflammation and post-translational modifications of chromatin, including DNA methylation, histone modification, and miRNAs. To achieve this about 1500 articles were reviewed via databases like PubMed, ScienceDirect, Google Scholar, and Web of Science. They were reduced to 534 using MeSH words like 'epigenetics, neuroinflammation, and HD' coupled with Boolean operators. Results indicated that major contributing factors to the development of HD such as mitochondrial dysfunction, excitotoxicity, neuroinflammation, and apoptosis are affected by epigenetic alterations. However, the association between neuroinflammation-altered epigenetics and the reported transcriptional changes in HD is unknown. Also, the link between epigenetically dysregulated genomic regions and specific DNA sequences suggests the likelihood that transcription factors, chromatin-remodeling proteins, and enzymes that affect gene expression are all disrupted simultaneously. Hence, therapies that target pathogenic pathways in HD, including neuroinflammation, transcriptional dysregulation, triplet instability, vesicle trafficking dysfunction, and protein degradation, need to be developed.

miR-196a provides antioxidative neuroprotection via USP15/Nrf2 regulation in Huntington's disease

Huntington's disease (HD) is a devastating neurodegenerative disorder characterized by the accumulation of mutant Huntingtin protein (mHTT) and oxidative stress-induced neuronal damage. Based on previous reports, microRNA-196a (miR-196a) has emerged as a potential therapeutic target due to its neuroprotective effects in various neurodegenerative diseases. However, whether miR-196a functions through antioxidative effects is still unknown. In this study, we demonstrated that HD models, both in vitro and in vivo, exhibit elevated levels of reactive oxygen species (ROS) and increased neuronal death, and miR-196a mitigates ROS levels and reduces cell death in HD cells. Moreover, we elucidated that miR-196a facilitates the translocation of nuclear factor erythroid 2 (Nrf2) into the nucleus, enhancing the transcription of antioxidant genes, including heme oxygenase-1 (HO-1). We further identified ubiquitin-specific peptidase 15 (USP15), a direct target of miR-196a related to the Nrf2 pathway, and USP15 exacerbates mHTT aggregate formation while partially counteracting miR-196a-induced reductions in mHTT levels. Taken together, these findings shed light on the multifaceted role of miR-196a in HD, highlighting its potential as a therapeutic avenue for ameliorating oxidative stress and neurodegeneration in this debilitating disease.

Understanding the Roles and Regulation of Mitochondrial microRNAs (MitomiRs) in Neurodegenerative Diseases: Current Status and Advances

MicroRNAs (miRNA) are a class of small non-coding RNA, roughly 21 - 22 nucleotides in length, which are master gene regulators. These miRNAs bind to the mRNA's 3' - untranslated region and regulate post-transcriptional gene regulation, thereby influencing various physiological and cellular processes. Another class of miRNAs known as mitochondrial miRNA (MitomiRs) has been found to either originate from the mitochondrial genome or be translocated directly into the mitochondria. Although the role of nuclear DNA encoded miRNA in the progression of various neurological diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, etc. is well known, accumulating evidence suggests the possible role of deregulated mitomiRs in the progression of various neurodegenerative diseases with unknown mechanism. We have attempted to outline the current state of mitomiRs role in controlling mitochondrial gene expression and function through this review, paying particular attention to their contribution to neurological processes, their etiology, and their potential therapeutic use.

The updated development of blood-based biomarkers for Huntington's disease

Huntington's disease is a progressive neurodegenerative disease caused by mutation of the huntingtin (HTT) gene. The identification of mutation carriers before symptom onset provides an opportunity to intervene in the early stage of the disease course. Optimal biomarkers are of great value to reflect neuropathological and clinical progression and are sensitive to potential disease-modifying treatments. Blood-based biomarkers have the merits of minimal invasiveness, low cost, easy accessibility and safety. In this review, we summarized the updated development of blood-based biomarkers for HD from six aspects, including neuronal injuries, oxidative stress, endocrine functions, immune reactions, metabolism and differentially expressed miRNAs. The blood-based biomarkers presented and discussed in this review were close to clinical applicability and might facilitate clinical design as surrogate endpoints. Exploration and validation of robust blood-based biomarkers require further standard and systemic study design in the future.

Non-coding RNAs in human health and disease: potential function as biomarkers and therapeutic targets

Human diseases have been a critical threat from the beginning of human history. Knowing the origin, course of action and treatment of any disease state is essential. A microscopic approach to the molecular field is a more coherent and accurate way to explore the mechanism, progression, and therapy with the introduction and evolution of technology than a macroscopic approach. Non-coding RNAs (ncRNAs) play increasingly important roles in detecting, developing, and treating all abnormalities related to physiology, pathology, genetics, epigenetics, cancer, and developmental diseases. Noncoding RNAs are becoming increasingly crucial as powerful, multipurpose regulators of all biological processes. Parallel to this, a rising amount of scientific information has revealed links between abnormal noncoding RNA expression and human disorders. Numerous non-coding transcripts with unknown functions have been found in addition to advancements in RNA-sequencing methods. Non-coding linear RNAs come in a variety of forms, including circular RNAs with a continuous closed loop (circRNA), long non-coding RNAs (lncRNA), and microRNAs (miRNA). This comprises specific information on their biogenesis, mode of action, physiological function, and significance concerning disease (such as cancer or cardiovascular diseases and others). This study review focuses on non-coding RNA as specific biomarkers and novel therapeutic targets.

Epigenetic Changes in Prion and Prion-like Neurodegenerative Diseases: Recent Advances, Potential as Biomarkers, and Future Perspectives

Prion diseases are transmissible spongiform encephalopathies (TSEs) caused by a conformational conversion of the native cellular prion protein (PrP^C) to an abnormal, infectious isoform called PrP^Sc. Amyotrophic lateral sclerosis, Alzheimer’s, Parkinson’s, and Huntington’s diseases are also known as prion-like diseases because they share common features with prion diseases, including protein misfolding and aggregation, as well as the spread of these misfolded proteins into different brain regions. Increasing evidence proposes the involvement of epigenetic mechanisms, namely DNA methylation, post-translational modifications of histones, and microRNA-mediated post-transcriptional gene regulation in the pathogenesis of prion-like diseases. Little is known about the role of epigenetic modifications in prion diseases, but recent findings also point to a potential regulatory role of epigenetic mechanisms in the pathology of these diseases. This review highlights recent findings on epigenetic modifications in TSEs and prion-like diseases and discusses the potential role of such mechanisms in disease pathology and their use as potential biomarkers.

miR-196a enhances polymerization of neuronal microfilaments through suppressing IMP3 and upregulating IGF2 in Huntington's disease

Huntington's disease (HD) is one of the inheritable neurodegenerative diseases, and these diseases share several similar pathological characteristics, such as abnormal neuronal morphology. miR-196a is a potential target to provide neuroprotective functions, and has been reported to enhance polymerization of neuronal microtubules in HD. While microtubules and microfilaments are two important components of the neuronal cytoskeleton, whether miR-196a improves neuronal microfilaments is still unknown. Here, we identify insulin-like growth factor 2 mRNA binding protein 3 (IMP3), and show that miR-196a directly suppresses IMP3 to increase neurite outgrowth in neurons. In addition, IMP3 disturbs neurite outgrowth in vitro and in vivo, and worsens the microfilament polymerization. Moreover, insulin-like growth factor-II (IGF2) is identified as the downstream target of IMP3, and miR-196a downregulates IMP3 to upregulate IGF2, which increases microfilamental filopodia numbers and activates Cdc42 to increase neurite outgrowth. Besides, miR-196a increases neurite outgrowth through IGF2 in different HD models. Finally, higher expression of IMP3 and lower expression IGF2 are observed in HD transgenic mice and patients, and increase the formation of aggregates in the HD cell model. Taken together, miR-196a enhances polymerization of neuronal microfilaments through suppressing IMP3 and upregulating IGF2 in HD, supporting the neuroprotective functions of miR-196a through neuronal cytoskeleton in HD.

The emerging role of long non-coding RNAs, microRNAs, and an accelerated epigenetic age in Huntington’s disease

Huntington’s disease (HD) is a dominantly inherited neurodegenerative disease with variable clinical manifestations. Recent studies highlighted the contribution of epigenetic alterations to HD progress and onset. The potential crosstalk between different epigenetic layers and players such as aberrant expression of non-coding RNAs and methylation alterations has been found to affect the pathogenesis of HD or mediate the effects of trinucleotide expansion in its pathophysiology. Also, microRNAs have been assessed for their roles in the modulation of HD manifestations, among them are miR-124, miR-128a, hsa-miR-323b-3p, miR-432, miR-146a, miR-19a, miR-27a, miR-101, miR-9*, miR-22, miR-132, and miR-214. Moreover, long non-coding RNAs such as DNM3OS, NEAT1, Meg3, and Abhd11os are suggested to be involved in the pathogenesis of HD. An accelerated DNA methylation age is another epigenetic signature reported recently for HD. The current literature search collected recent findings of dysregulation of miRNAs or lncRNAs as well as methylation changes and epigenetic age in HD.

Extracellular Vesicles, Stem Cells and the Role of miRNAs in Neurodegeneration

There are different modalities of intercellular communication governed by cellular homeostasis. In this review, we will explore one of these forms of communication called extracellular vesicles (EVs). These vesicles are released by all cells in the body and are heterogeneous in nature. The primary function of EVs is to share information through their cargo consisting of proteins, lipids and nucleic acids (mRNA, miRNA, dsDNA etc.) with other cells, which have a direct consequence on their microenvironment. We will focus on the role of EVs of mesenchymal stem cells (MSCs) in the nervous system and how these participate in intercellular communication to maintain physiological function and provide neuroprotection. However, deregulation of this same communication system could play a role in several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, multiple sclerosis, prion disease and Huntington's disease. The release of EVs from a cell provides crucial information to what is happening inside the cell and thus could be used in diagnostics and therapy. We will discuss and explore new avenues for the clinical applications of using engineered MSC-EVs and their potential therapeutic benefit in treating neurodegenerative diseases.

MicroRNAs in Huntington's Disease: Diagnostic Biomarkers or Therapeutic Agents?

MicroRNA (miRNA) is a non-coding single-stranded small molecule of approximately 21 nucleotides. It degrades or inhibits the translation of RNA by targeting the 3′-UTR. The miRNA plays an important role in the growth, development, differentiation, and functional execution of the nervous system. Dysregulated miRNA expression has been associated with several pathological processes of neurodegenerative disorders, including Huntington’s disease (HD). Recent studies have suggested promising roles of miRNAs as biomarkers and potential therapeutic targets for HD. Here, we review the emerging role of dysregulated miRNAs in HD and describe general biology of miRNAs, their pathophysiological implications, and their potential roles as biomarkers and therapeutic agents.

The regulatory roles of microRNAs toward pathogenesis and treatments in Huntington's disease

Huntington's disease (HD) is one of neurodegenerative diseases, and is defined as a monogenetic disease due to the mutation of Huntingtin gene. This disease affects several cellular functions in neurons, and further influences motor and cognitive ability, leading to the suffering of devastating symptoms in HD patients. MicroRNA (miRNA) is a non-coding RNA, and is responsible for gene regulation at post-transcriptional levels in cells. Since one miRNA targets to several downstream genes, it may regulate different pathways simultaneously. As a result, it raises a potential therapy for different diseases using miRNAs, especially for inherited diseases. In this review, we will not only introduce the update information of HD and miRNA, but also discuss the development of potential miRNA-based therapy in HD. With the understanding toward the progression of miRNA studies in HD, we anticipate it may provide an insight to treat this devastating disease, even applying to other genetic diseases.

Critical roles of microRNA-196 in normal physiology and non-malignant diseases: Diagnostic and therapeutic implications

MicroRNAs (miRNAs) have emerged as a critical component of regulatory networks that modulate and fine-tune gene expression in a post-transcriptional manner. The microRNA-196 family is encoded by three loci in the human genome, namely hsa-mir-196a-1, hsa-mir-196a-2, and hsa-mir-196b. Increasing evidence supports the roles of different components of this miRNA family in regulating key cellular processes during differentiation and development, ranging from inflammation and differentiation of stem cells to limb development and remodeling and structure of adipose tissue. This review first discusses about the genomic context and regulation of this miRNA family and then take a bird's eye view on the updated list of its target genes and their biological processes to obtain insights about various functions played by members of the microRNA-196 family. We then describe evidence supporting the involvement of the human microRNA-196 family in regulating critical cellular processes both in physiological and non-malignant inflammatory conditions, highlighting recent seminal findings that carry implications for developing novel therapeutic or diagnostic strategies.

High-Throughput Sequencing of BACHD Mice Reveals Upregulation of Neuroprotective miRNAs at the Pre-Symptomatic Stage of Huntington's Disease

Huntington’s disease (HD) is a genetic disorder marked by transcriptional alterations that result in neuronal impairment and death. MicroRNAs (miRNAs) are non-coding RNAs involved in post-transcriptional regulation and fine-tuning of gene expression. Several studies identified altered miRNA expression in HD and other neurodegenerative diseases, however their roles in early stages of HD remain elusive. Here, we deep-sequenced miRNAs from the striatum of the HD mouse model, BACHD, at the age of 2 and 8 months, representing the pre-symptomatic and symptomatic stages of the disease. Our results show that 44 and 26 miRNAs were differentially expressed in 2- and 8-month-old BACHD mice, respectively, as compared to wild-type controls. Over-representation analysis suggested that miRNAs up-regulated in 2-month-old mice control the expression of genes crucial for PI3K-Akt and mTOR cell signaling pathways. Conversely, miRNAs regulating genes involved in neuronal disorders were down-regulated in 2-month-old BACHD mice. Interestingly, primary striatal neurons treated with anti-miRs targeting two up-regulated miRNAs, miR-449c-5p and miR-146b-5p, showed higher levels of cell death. Therefore, our results suggest that the miRNAs altered in 2-month-old BACHD mice regulate genes involved in the promotion of cell survival. Notably, over-representation suggested that targets of differentially expressed miRNAs at the age of 8 months were not significantly enriched for the same pathways. Together, our data shed light on the role of miRNAs in the initial stages of HD, suggesting a neuroprotective role as an attempt to maintain or reestablish cellular homeostasis.

Mitochondrial MicroRNAs in Aging and Neurodegenerative Diseases

MicroRNAs (miRNAs) are important regulators of several biological processes, such as cell growth, cell proliferation, embryonic development, tissue differentiation, and apoptosis. Currently, over 2000 mammalian miRNAs have been reported to regulate these biological processes. A subset of microRNAs was found to be localized to human mitochondria (mitomiRs). Through years of research, over 400 mitomiRs have been shown to modulate the translational activity of the mitochondrial genome. While miRNAs have been studied for years, the function of mitomiRs and their role in neurodegenerative pathologies is not known. The purpose of our article is to highlight recent findings that relate mitomiRs to neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and Huntington’s. We also discuss the involvement of mitomiRs in regulating the mitochondrial genome in age-related neurodegenerative diseases.

Functional roles and networks of non-coding RNAs in the pathogenesis of neurodegenerative diseases

Recent transcriptome analyses have revealed that noncoding RNAs (ncRNAs) are broadly expressed in mammalian cells and abundant in the CNS, with tissue and cell type-specific expression patterns. Moreover, ncRNAs have been found to intricately and dynamically regulate various signaling pathways in neurodegeneration. As such, some antisense transcripts and microRNAs are known to directly affect neurodegeneration in disease contexts. The functions of ncRNAs in pathogenesis are unique for each disorder, as are the pertinent networks of ncRNA/miRNA/mRNA that mediate these functions. Thus, further understanding of ncRNA biogenesis and effects might aid the discovery of diagnostic biomarkers or development of effective therapeutics for neurodegenerative disorders. Here, we review the ncRNAs that have so far been identified in major neurodegenerative disease etiology and the mechanisms that link ncRNAs with disease-specific phenotypes, such as HTT aggregation in HD, α-synuclein in PD, and Aβ plaques and hyperphosphorylated Tau in AD. We also summarize the known lncRNA/miRNA/mRNA networks that participate in neurodegenerative diseases, and we discuss ncRNA-related treatments shown to delay disease onset and prolong lifespan in rodent models.

Circulating RNAs as Potential Biomarkers in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex multi-system neurodegenerative disorder with currently limited diagnostic and no therapeutic options. Despite the intense efforts no clinically applicable biomarkers for ALS are yet established. Most current research is thus focused, in particular, in identifying potential non-invasive circulating biomarkers for more rapid and accurate diagnosis and monitoring of the disease. In this review, we have focused on messenger RNA (mRNA), non-coding RNAs (lncRNAs), micro RNAs (miRNAs) and circular RNA (circRNAs) as potential biomarkers for ALS in peripheral blood serum, plasma and cells. The most promising miRNAs include miR-206, miR-133b, miR-27a, mi-338-3p, miR-183, miR-451, let-7 and miR-125b. To test clinical potential of this miRNA panel, a useful approach may be to perform such analysis on larger multi-center scale using similar experimental design. However, other types of RNAs (lncRNAs, circRNAs and mRNAs) that, together with miRNAs, represent RNA networks, have not been yet extensively studied in blood samples of patients with ALS. Additional research has to be done in order to find robust circulating biomarkers and therapeutic targets that will distinguish key RNA interactions in specific ALS-types to facilitate diagnosis, predict progression and design therapy.

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

Epigenetic modifications are emerging as major players in the pathogenesis of neurodegenerative disorders and susceptibility to acute brain injury. DNA and histone modifications act together with non-coding RNAs to form a complex gene expression machinery that adapts the brain to environmental stressors and injury response. These modifications influence cell-level operations like neurogenesis and DNA repair to large, intricate processes such as brain patterning, memory formation, motor function and cognition. Thus, epigenetic imbalance has been shown to influence the progression of many neurological disorders independent of aberrations in the genetic code. This review aims to highlight ways in which epigenetics applies to several commonly researched neurodegenerative diseases and forms of acute brain injury as well as shed light on the benefits of epigenetics-based treatments.

Chromatin accessibility and transcription dynamics during in vitro astrocyte differentiation of Huntington's Disease Monkey pluripotent stem cells

BACKGROUND

Huntington's Disease (HD) is a fatal neurodegenerative disorder caused by a CAG repeat expansion, resulting in a mutant huntingtin protein. While it is now clear that astrocytes are affected by HD and significantly contribute to neuronal dysfunction and pathogenesis, the alterations in the transcriptional and epigenetic profiles in HD astrocytes have yet to be characterized. Here, we examine global transcription and chromatin accessibility dynamics during in vitro astrocyte differentiation in a transgenic non-human primate model of HD.

RESULTS

We found global changes in accessibility and transcription across different stages of HD pluripotent stem cell differentiation, with distinct trends first observed in neural progenitor cells (NPCs), once cells have committed to a neural lineage. Transcription of p53 signaling and cell cycle pathway genes was highly impacted during differentiation, with depletion in HD NPCs and upregulation in HD astrocytes. E2F target genes also displayed this inverse expression pattern, and strong associations between E2F target gene expression and accessibility at nearby putative enhancers were observed.

CONCLUSIONS

The results suggest that chromatin accessibility and transcription are altered throughout in vitro HD astrocyte differentiation and provide evidence that E2F dysregulation contributes to aberrant cell-cycle re-entry and apoptosis throughout the progression from NPCs to astrocytes.

The Emerging Role of microRNAs in Polyglutamine Diseases

MicroRNAs (miRNAs) are small non-coding molecules that regulate a large amount of post-transcriptional repressor genes by recognizing semi-complementary target sequences that are normally located in the 3' UTR of the mRNA. Altered expression of miRNA has been related to several pathological processes, including polyglutamine (Poly Q) diseases. Specific expression patterns in the circulating fluids and brain parenchyma have been speculated as potential biomarkers for Poly Q disease diagnosis and prognosis. Several miRNAs have been consistently identified in diseases including Huntington's disease (HD) and spinocerebellar ataxia (SCA). In our review, we describe the emerging role of miRNAs in Poly Q diseases and provide an overview on general miRNA biology, implications in pathophysiology, and their potential roles as future biomarkers and applications for therapy.

Combination of stem cell and gene therapy ameliorates symptoms in Huntington's disease mice

Huntington's disease (HD) is a dominantly inherited monogenetic disorder characterized by motor and cognitive dysfunction due to neurodegeneration. The disease is caused by the polyglutamine (polyQ) expansion at the 5' terminal of the exon 1 of the huntingtin (HTT) gene, IT15, which results in the accumulation of mutant HTT (mHTT) aggregates in neurons and cell death. The monogenetic cause and the loss of specific neural cell population make HD a suitable candidate for stem cell and gene therapy. In this study, we demonstrate the efficacy of the combination of stem cell and gene therapy in a transgenic HD mouse model (N171-82Q; HD mice) using rhesus monkey (Macaca mulatta) neural progenitor cells (NPCs). We have established monkey NPC cell lines from induced pluripotent stem cells (iPSCs) that can differentiate into GABAergic neurons in vitro as well as in mouse brains without tumor formation. Wild-type monkey NPCs (WT-NPCs), NPCs derived from a transgenic HD monkey (HD-NPCs), and genetically modified HD-NPCs with reduced mHTT levels by stable expression of small-hairpin RNA (HD-shHD-NPCs), were grafted into the striatum of WT and HD mice. Mice that received HD-shHD-NPC grafts showed a significant increase in lifespan compared to the sham injection group and HD mice. Both WT-NPC and HD-shHD-NPC grafts in HD mice showed significant improvement in motor functions assessed by rotarod and grip strength. Also, immunohistochemistry demonstrated the integration and differentiation. Our results suggest the combination of stem cell and gene therapy as a viable therapeutic option for HD treatment.

Amelioration of Huntington's disease phenotype in astrocytes derived from iPSC-derived neural progenitor cells of Huntington's disease monkeys

Huntington’s disease (HD) is a devastating monogenic, dominant, hereditary, neurodegenerative disease. HD is caused by the expansion of CAG repeats in exon 1 of the huntingtin (HTT) gene, IT15, resulting in an expanded polyglutamine (polyQ) residue in the N-terminus of the HTT protein. HD is characterized by the accumulation of mutant HTT (mHTT) in neural and somatic cells. Progressive brain atrophy occurs initially in the striatum and extends to different brain regions with progressive decline in cognitive, behavioral and motor functions. Astrocytes are the most abundant cell type in the brain and play an essential role in neural development and maintaining homeostasis in the central nervous system (CNS). There is increasing evidence supporting the involvement of astrocytes in the development of neurodegenerative diseases such as Parkinson’s disease (PD), Huntington’s disease (HD), Alzheimer’s disease (AD), and amyotrophic lateral sclerosis (ALS). We have generated neural progenitor cells (NPCs) from induced pluripotent stem cells (iPSCs) of transgenic HD monkeys as a model for studying HD pathogenesis. We have reported that NPCs can be differentiated in vitro into mature neural cells, such as neurons and glial cells, and are an excellent tool to study the pathogenesis of HD. To better understand the role of astrocytes in HD pathogenesis and discover new therapies to treat HD, we have developed an astrocyte differentiation protocol and evaluated the efficacy of RNAi to ameliorate HD phenotypes in astrocytes. The resultant astrocytes expressed canonical astrocyte-specific markers examined by immunostaining and real-time PCR. Flow cytometry (FACS) analysis showed that the majority of the differentiated NPCs (95.7%) were positive for an astrocyte specific marker, glial fibrillary acidic protein (GFAP). Functionalities of astrocytes were evaluated by glutamate uptake assay and electrophysiology. Expression of mHTT in differentiated astrocytes induced cytosolic mHTT aggregates and nuclear inclusions, suppressed the expression of SOD2 and PGC1, reduced ability to uptake glutamate, decreased 4-aminopyridine (4-AP) response, and shifted I/V plot measured by electrophysiology, which are consistent with previous reports on HD astrocytes and patient brain samples. However, expression of small-hairpin RNA against HTT (shHD) ameliorated and reversed aforementioned HD phenotypes in astrocytes. This represents a demonstration of a novel non-human primate (NHP) astrocyte model for studying HD pathogenesis and a platform for discovering novel HD treatments.

MicroRNA in Brain pathology: Neurodegeneration the Other Side of the Brain Cancer

The mammalian brain is made up of billions of neurons and supporting cells (glial cells), intricately connected. Molecular perturbations often lead to neurodegeneration by progressive loss of structure and malfunction of neurons, including their death. On the other side, a combination of genetic and cellular factors in glial cells, and less frequently in neurons, drive oncogenic transformation. In both situations, microenvironmental niches influence the progression of diseases and therapeutic responses. Dynamic changes that occur in cellular transcriptomes during the progression of developmental lineages and pathogenesis are controlled through a variety of regulatory networks. These include epigenetic modifications, signaling pathways, and transcriptional and post-transcriptional mechanisms. One prominent component of the latter is small non-coding RNAs, including microRNAs, that control the vast majority of these networks including genes regulating neural stemness, differentiation, apoptosis, projection fates, migration and many others. These cellular processes are also profoundly dependent on the microenvironment, stemness niche, hypoxic microenvironment, and interactions with associated cells including endothelial and immune cells. Significantly, the brain of all other mammalian organs expresses the highest number of microRNAs, with an additional gain in expression in the early stage of neurodegeneration and loss in expression in oncogenesis. However, a mechanistic explanation of the concept of an apparent inverse correlation between the odds of cancer and neurodegenerative diseases is only weakly developed. In this review, we thus will discuss widespread de-regulation of microRNAome observed in these two major groups of brain pathologies. The deciphering of these intricacies is of importance, as therapeutic restoration of pre-pathological microRNA landscape in neurodegeneration must not lead to oncogenesis and vice versa. We thus focus on microRNAs engaged in cellular processes that are inversely regulated in these diseases. We also aim to define the difference in microRNA networks between pro-survival and pro-apoptotic signaling in the brain.

Transcriptional Dysregulation and Post-translational Modifications in Polyglutamine Diseases: From Pathogenesis to Potential Therapeutic Strategies

Polyglutamine (polyQ) diseases are hereditary neurodegenerative disorders caused by an abnormal expansion of a trinucleotide CAG repeat in the coding region of their respective associated genes. PolyQ diseases mainly display progressive degeneration of the brain and spinal cord. Nine polyQ diseases are known, including Huntington's disease (HD), spinal and bulbar muscular atrophy (SBMA), dentatorubral-pallidoluysian atrophy (DRPLA), and six forms of spinocerebellar ataxia (SCA). HD is the best characterized polyQ disease. Many studies have reported that transcriptional dysregulation and post-translational disruptions, which may interact with each other, are central features of polyQ diseases. Post-translational modifications, such as the acetylation of histones, are closely associated with the regulation of the transcriptional activity. A number of groups have studied the interactions between the polyQ proteins and transcription factors. Pharmacological drugs or genetic manipulations aimed at correcting the dysregulation have been confirmed to be effective in the treatment of polyQ diseases in many animal and cellular models. For example, histone deaceylase inhibitors have been demonstrated to have beneficial effects in cases of HD, SBMA, DRPLA, and SCA3. In this review, we describe the transcriptional and post-translational dysregulation in polyQ diseases with special focus on HD, and we summarize and comment on potential treatment approaches targeting disruption of transcription and post-translation processes in these diseases.

Epigenetic profiles in polyglutamine disorders

The dominant polyglutamine (polyQ) disorders are a group of progressive and incurable neurodegenerative disorders, which are caused by unstable expanded CAG trinucleotide repeats in the coding regions of their respective causative genes. The most prevalent polyQ disorders worldwide are Huntington’s disease and spinocerebellar ataxia type 3. Epigenetic mechanisms, such as DNA methylation, histone modifications and chromatin remodeling and noncoding RNA regulation, regulate gene expression or genome function. Epigenetic dysregulation has been suggested to play a pivotal role in the pathogenesis of polyQ disorders. Here, we summarize the current knowledge of epigenetic changes present in several representative polyQ disorders and discuss the potentiality of miRNAs as therapeutic targets for the clinic therapy of these disorders.

Progress in developing transgenic monkey model for Huntington's disease

Huntington's disease (HD) is a complex neurodegenerative disorder that has no cure. Although treatments can often be given to relieve symptoms, the neuropathology associated with HD cannot be stopped or reversed. HD is characterized by degeneration of the striatum and associated pathways that leads to impairment in motor and cognitive functions as well as psychiatric disturbances. Although cell and rodent models for HD exist, longitudinal study in a transgenic HD nonhuman primate (i.e., rhesus macaque; HD monkeys) shows high similarity in its progression with human patients. Progressive brain atrophy and changes in white matter integrity examined by magnetic resonance imaging are coherent with the decline in cognitive behaviors related to corticostriatal functions and neuropathology. HD monkeys also express higher anxiety and irritability/aggression similar to human HD patients that other model systems have not yet replicated. While a comparative model approach is critical for advancing our understanding of HD pathogenesis, HD monkeys could provide a unique platform for preclinical studies and long-term assessment of translatable outcome measures. This review summarizes the progress in the development of the transgenic HD monkey model and the opportunities for advancing HD preclinical research.

miR-196a Enhances Neuronal Morphology through Suppressing RANBP10 to Provide Neuroprotection in Huntington's Disease

MicroRNAs (miRNAs) play important roles in several neurobiological processes, including the development and progression of diseases. Previously, we identified that one specific miRNA, miR-196a, provides neuroprotective effects on Huntington's disease (HD), although the detailed mechanism is still unclear. Based on our bioinformatic analyses, we hypothesize miR-196a might offer neuroprotective functions through improving cytoskeletons of brain cells. Here, we show that miR-196a could enhance neuronal morphology, further ameliorating intracellular transport, synaptic plasticity, neuronal activity, and learning and memory abilities. Additionally, we found that miR-196a could suppress the expression of RAN binding protein 10 (RANBP10) through binding to its 3' untranslated region, and higher expression of RANBP10 exacerbates neuronal morphology and intracellular transport. Furthermore, miR-196a enhances neuronal morphology through suppressing RANBP10 and increasing the ability of β-tubulin polymerization. Most importantly, we observed higher expression of RANBP10 in the brains of HD transgenic mice, and higher expression of RANBP10 might exacerbate the pathological aggregates in HD. Taken together, we provide evidence that enhancement of neuronal morphology through RANBP10 is one of the neuroprotective mechanisms for miR-196a. Since miR-196a has also been reported in other neuronal diseases, this study might offer insights with regard to the therapeutic use of miR-196a in other neuronal diseases.